Dwarf Fin Whale

Balaenoptera omurai (lat.) — Balinakimilər dəstəsinə, Zolaqlı balinalar (Balaenopteridae) fəsiləsinə aid növ. Müstəqil növ olaraq 2003-ci ildə molyekulyar-genetik araşdırmalar nəticəsində müəyyənləşmişdir. Bu növün aşkarlanmasında yapon Hideo Omurinin (大村 秀雄) şərəfinə adlandırılmışdır.

Növün qeydə alınması

Növün təstiqlənməsi 20 noyabr 2003 ildə «Nature»^[1] jurnalında dərc olunmuşdur. Yapon zooloqları Siro Vada, Masayoki Oisi və Tadasu Yamada muzeylərdə olan Brayde zolaqlı balina və İden zolaqlı balina skeletlərini araşdırdıqdan sonra yeni növün aşkarlanmasını qeydə alırlar.

2015-ci ilin oktyabrında beynəlxalq araşdırmaçılar Madaqaskar sahillərində bir qrup Omuri balinasını aşkarlamışlar. Bu zaman ilk dəfə olaraq növün xüsusiyyətləri müəyyənləşdirilmişdir^[2].

Areal

Əsasən Sakit okeanın Yaponiya adaları sahillərində yayılmışlar.

İstinadlar

Balaenoptera omurai, Nossi-Bé

Balaenoptera omurai és una espècie de balena de la qual no se sap gairebé res. De fet, manca fins i tot de nom vernacular. El descobriment d'aquesta balena fou anunciat a l'edició del 20 de novembre del 2003 de la revista científica Nature (426, 278-281) per tres científics japonesos, Shiro Wada, Masayuki Oishi i Tadasu K. Yamada. A l'article, els científics descriuen l'espècie com a similar al rorqual comú en aparença externa, però més petita.

Referències

Schädel eines Omurawals

Der Omurawal (Balaenoptera omurai) ist eine im November 2003 erstmals beschriebene Art der Furchenwale (Balaenopteridae), die zu den Bartenwalen (Mysticeti) gehören. Die Typusexemplare der Art wurden in den späten 1970er Jahren im Japanischen Meer (Terra typica), in der Salomonensee und in der Nähe der Cocos Islands gefangen.

Nach Angaben der Erstbeschreiber Shirō Wada (和田 志郎), Masayuki Ōishi (大石 雅之) und Tadasu K. Yamada (山田 格) aus Japan handelt es sich um eine dem Finnwal (Balaenoptera physalus) sehr ähnliche Art, die aber mit einer Länge von rund zwölf Metern deutlich kleiner als diese ist. Auch haben sie mit nur 200 Barten deutlich weniger als andere Bartenwale. Über die Lebensweise der Tiere ist nichts bekannt.

Die Veröffentlichung der Artbeschreibung in der Fachzeitschrift Nature am 20. November 2003 stieß zunächst auf massive Zweifel in der Fachwelt, da man Omurawale bisher lediglich für kleine Exemplare der Brydewale hielt. Die Forscher belegten ihre Beschreibung anhand von mitochondrialen DNA-Vergleichen mit anderen Walen, wobei sie auch die Notwendigkeit weiterer Analysen herausstellten. Als Grundlage dienten ihnen neun Individuen, von denen acht bereits in den späten 1970er Jahren gefangen worden waren. Das Artepithet des wissenschaftlichen Namens leitet sich von dem japanischen Walforscher Hideo Ōmura (大村 秀雄, 1906–1993) ab.

Verbreitung

Zunächst ging man davon aus, dass Omurawale nur im zentralen Indopazifik vorkommen. Zwischen 2007 und 2019 wurden Omurawale jedoch mit Ausnahme des zentralen und östlichen Pazifik in den gemäßigten, subtropischen und tropischen Bereichen aller Weltmeere gefunden. Nachweise gibt es aus dem zentralen Indopazifik, dem nördlichen, zentralen und westlichen Indischen Ozean (Madagaskar^[1]), von der Straße von Hormus, aus dem nördlichen Roten Meer und aus dem südlichen und mittleren Atlantik.^[2][3][4]

Belege

1. ↑ ^{a b} Salvatore Cerchio, Boris Andrianantenaina, Alec Lindsay, Melinda Rekdahl, Norbert Andrianarivelo, Tahina Rasoloarijao: Omura’s whales (Balaenoptera omurai) off northwest Madagascar: ecology, behaviour and conservation needs. Oktober 2015, DOI: 10.1098/rsos.150301.
2. ↑ Jean-Luc Jung, Wim C. Mullié, Koen Van Waerebeek, Moulaye Mohamed Wagne, Abdellahi Samba Ould Bilal, Zein El Abidine Ould Sidaty, (2016). Omura's whale off West Africa: Autochthonous population or inter-oceanic vagrant in the Atlantic Ocean? Marine Biology Research, 12, 66–75, 2015, doi: 10.1080/17451000.2015.1084424
3. ↑ Ana Lúcia Cypriano‐Souza, Ana Carolina Oliveira de Meirelles, Vitor Luz Carvalho, Sandro Luis Bonatto (2017). Rare or cryptic? The first report of an Omura's whale (Balaenoptera omurai) in the South Atlantic Ocean. Marine Mammal Science, 33, 80–95, 2016, doi: 10.1111/mms.12348
4. ↑ Salvatore Cerchio, Tadasu K. Yamada uand Robert L. Brownell Jr. (2019). Global distribution of Omura's whales (Balaenoptera omurai) and assessment of range-wide threats. Frontiers in Marine Science, 6, 67. doi: 10.3389/fmars.2019.00067

Literatur

• Shiro Wada, Masayuki Oishi, Tadasu K. Yamada: A newly discovered species of living baleen whale. In: Nature. Band 426, 2003, S. 278–281, doi:10.1038/nature02103 (englisch, PDF).
• Hadoram Shirihai: Meeressäuger. Alle 129 Arten weltweit. Illustriert von Brett Jarett. Franckh-Kosmos Verlags GmbH, Stuttgart 2008, ISBN 978-3-440-11277-9.

Weblinks

– Sammlung von Bildern, Videos und Audiodateien

• National Geographic – New Whale Species Announced by Japanese Scientists
• Balaenoptera omurai in der Roten Liste gefährdeter Arten der IUCN 2021.2. Eingestellt von: Cooke, J.G. & Brownell Jr., R.L., 2019. Abgerufen am 25. Oktober 2021.
• Erste Filmaufnahmen eines Omurawals (New England Aquarium auf YouTube)

Omura's whale or the dwarf fin whale (Balaenoptera omurai) is a species of rorqual about which very little is known.^[3] Before its formal description, it was referred to as a small, dwarf or pygmy form of Bryde's whale by various sources.^[4] The common name and specific epithet commemorate Japanese cetologist Hideo Omura.^[5][6]

The scientific description of this whale was made in Nature in 2003 by three Japanese scientists. They determined the existence of the species by analysing the morphology and mitochondrial DNA of nine individuals – eight caught by Japanese research vessels in the late 1970s in the Indo-Pacific and an adult female collected in 1998 from Tsunoshima, an island in the Sea of Japan. Later, abundant genetic evidence confirmed Omura's whale as a valid species and revealed it to be an early offshoot from the rorqual lineage, diverging much earlier than Bryde's and sei whales. It is perhaps more closely related to its larger relative, the blue whale.^[5][7]

In the third edition of Mammal Species of the World, the "species" is relegated to being a synonym of Balaenoptera edeni. However, the authors note that this is subject to a revision of the genus.^[8] The database ITIS lists this as a valid taxon, noting a caveat on the disputed systematics of this species, Balaenoptera edeni and Balaenoptera brydei.^[9]

Taxonomy

Skull of Omura's whale in National Museum of Natural Science

The six specimens obtained in the Solomon Sea in 1976 were only noted to be smaller at sexual maturity than the "ordinary" Bryde's whales caught off New Zealand, whereas the two caught near the Cocos-Keeling Islands in 1978 were not differentiated from the 118 other "ordinary" Bryde's whales taken in the eastern Indian Ocean, south of Java. As a result of allozyme analysis, their distinctive baleen and small size at physical maturity compared to Bryde's whale, and photographs obtained of the harvested whales (showing their fin whale-like coloration), Shiro Wada and Kenichi Numachi (1991) decided that these eight individuals represented members of a new species of baleen whale. However, due to the lack of a detailed osteological study and the absence of "conclusive data", the International Whaling Commission decided to consider them only as a regionally distinct group of "small-form Bryde's whale". Despite this declaration, the specific status of the Solomon Sea specimens was supported by a mitochondrial DNA study done by Hideyoshi Yoshida and Hidehiro Kato (1999).^{[1][10][11][12][13]}

The identity of these eight specimens was finally resolved in 1998 when an unidentified whale, which had died after colliding with a fishing boat in the Sea of Japan and was towed to Tsunoshima, was examined by Tadasu Yamada, Chief of the Division of Mammals and Birds at the National Science Museum, Tokyo. This specimen closely resembled the individuals caught in the 1970s in external appearance and allowed a complete osteological examination of the putative new species to be conducted. As a result of external morphology, osteology, and mitochondrial DNA analysis of two of the harvested whales and the Tsunoshima specimen, Wada, Masayuki Oishi, and Yamada described Balaenoptera omurai in the 20 November 2003 issue of the journal Nature. In honour of the people of Tsunoshima, who helped remove the flesh from the type specimen, it was given the Japanese vernacular name of Tsunoshima kujira (English: Horn Island whale).^[5][12]

Holotype and paratypes

The holotype is an 11.03 m (36.2 ft) adult female, NSMT-M32505 (National Science Museum, Tokyo), which stranded at Tsunoshima () in the southern Sea of Japan on 11 September 1998. It includes a complete skeleton, both complete rows of baleen plates, and frozen pieces of muscle, blubber, and kidney collected by T. K. Yamada, M. Oishi, T. Kuramochi, E. Jibiki, and S. Fujioka. The type locality is the Sea of Japan, which may not be representative of the species’ typical range. The paratypes include the eight specimens (five females and three males), NRIFSF1-8 (National Research Institute of Far Seas Fisheries, Fisheries Research Agency, Shizuoka), collected by Japanese research vessels in the Indo-Pacific in the late 1970s. The longest baleen plate (NRIFSF6 includes 18 more baleen plates), an earplug, and a piece of the sixth thoracic vertebra with associated epiphysis were collected from each individual.^[1][5]

Description

Osteology

Omura's whale has several unique skeletal features that distinguish it from its congeners, namely B. brydei and B. edeni. In B. omurai and B. brydei, the posterior end of the ascending process of the maxilla widens to become squarish, whereas in B. edeni, it is slender and round throughout its length. In B. omurai, this widened posterior portion conceals the premaxilla, which disappears below the maxilla and nasal and does not reach the frontal, whereas in both B. brydei and B. edeni, the premaxilla reaches the frontal. The parietals flare laterally in dorsal view in B. omurai and the Indo-Pacific form of B. brydei, but are invisible in dorsal view in B. edeni and the North Pacific form of B. brydei. B. omurai has two small foramina "along the suture between the parietal and squamosal in the posterior wall of the temporal fossa", which both B. brydei and B. edeni lack. B. omurai has an oblique ridge on the dorsal side of the maxilla near the base of the rostrum, which is absent in both B. brydei and B. edeni. Unlike B. edeni, the alisphenoid is separate from the squamosal in B. omurai. The head of the first rib is not bifurcated in B. omurai, unlike B. brydei and B. edeni.^[5][14]

Omura's whale has a total of 53 vertebrae, including seven cervical (the standard number among mammals), 13 thoracic, 12 lumbar, and 21 caudal. Like all members of its genus, it has only four digits on the manus of each pectoral fin (the third digit is missing). The phalangeal formula is: I-5, II-7, IV-6, V-3.^[5][15]

External appearance

Feeding off Nosy Be, Madagascar

Its appearance resembles the larger fin whale (thus the alternate common names of dwarf fin whale^[16] and little fin whale), both having a dark gray left lower jaw, and on the right side a white mandible patch, a white blaze, a dark eye stripe, a white inter-stripe wash, as well as a white chevron on the back, pectoral fins with a white anterior border and inner surface, and flukes with a white ventral surface and black margins. Like fin whales, it also exhibits a white left gape and a dark right gape, a reversal of the asymmetrical pigmentation on the lower jaw. It has a very falcate dorsal fin with a leading edge that gradually slopes into the back, halfway in shape between the more gradual slope of the fin whale and the more acute angle of Bryde's and sei whales. Its dorsal fin is also proportionally smaller and less upright than these other species. It typically has a single prominent median ridge on the rostrum, but can have faint lateral ridges, which are more pronounced in calves. Bryde's whale, on the other hand, has three prominent ridges on the rostrum. It has 45 to 95 ventral grooves that extend past the umbilicus. The type specimen (NSMT-M32505) had 203-208 pairs of baleen plates that were "short and broad with uncurled, stiff, grayish-white fringes", while NRIFSF6 had an estimated 181–190 on the right side – fewer than any other species in its genus. Other specimens of Omura's whale had between 204 and 246 pairs of baleen plates. Like the fin whale, NSMT-M32505 exhibited asymmetrical coloration in its baleen, as well: on the right side, the front third are yellowish-white, the intermediate 100 plates are bi-colored (dark on the outer side and yellowish-white on the inner side), and the remaining plates in the back were all black, while on the left side, the majority are bi-colored with the remaining back plates being all black like the right side. The average length and width for the nine specimens was 26 by 21.4 cm (10.2 by 8.4 in), the smallest length-to-breadth quotient (1.22) for any species in its genus.^{[3][5][17][18]}

Omura's whale seen off New Caledonia, the Solomon Islands, West Sumatra, and East Kalimantan showed extensive scarring from cookiecutter shark bites, indicating they had ventured into deep waters;^[19] whereas those off Madagascar did not exhibit them.^[17]

Morphometrics

The rostrum is flat and V-shaped with the head occupying about a quarter of the body length. The pectoral fins are short but slender, being from about 13 to 15 per cent of the body length. The dorsal fin ranges between 7.5 and 20 cm (3 to 8 inches) in height and 18 to 60 cm (7 to 23.6 inches) in length for specimens 3.9 to 7.15 m (12.8 to 23.4 ft) in length, and is placed about 57 per cent of the body length back from the tip of the rostrum. It is 61.5 per cent of the body length from the tip of the lower jaw to the umbilicus, whereas it is about 63 per cent from the tip of the lower jaw to the end of the ventral grooves. The flukes are about a quarter to a fifth of the body length in width.^[18][20][21]

Size

Omura's whale is among the smallest of the rorquals – only the two species of minke whale, the common and Antarctic, which reach 9.75 and 10.7 m (32.0 and 35.1 ft) in length, respectively, are smaller.^[22] Of the eight specimens taken during Japanese whaling in the Indo-Pacific, the five females ranged in length from 10.1 to 11.5 m (33.1 to 37.7 ft), while the three males ranged from 9.6 to 10.0 m (31.5 to 32.8 ft). The females ranged in age from perhaps only 9 years (the earplug was damaged or partially lost) for an 11.2 m (36.7 ft) individual to 29 years for the longest female, whereas the three males ranged from perhaps 21 years (another damaged or partially lost earplug) for the longest male to 38 years for one of the 9.6 m (31.5 ft) specimens. All were physically mature with the exception of the smallest female. Of individuals found stranded in Taiwan and Thailand between 1983 and 2004, five males ranged in length from 5.13 to 10 m (16.8 to 32.8 ft), while two females were 4.3 and 5.95 m (14.1 and 19.5 ft), respectively – a specimen of unknown sex that stranded in 1983 in Phuket Province, Thailand, was 7 m (23.0 ft) in length.^[5][14]

Of 16 "Bryde's whales" caught by hunters from Pamilacan between 1991 and 1993, 12 were measured. These cluster into two size categories, nine whales less than 10 m (32.8 ft), and three 12 m (39.4 ft) or more. Later, 85% (24 of 28) of the identified skull specimens examined from the Bohol Sea were found to be Omura's whales, whereas only 15% (4 of 28) were what was tentatively called the Indo-Pacific form of Bryde's whale (B. brydei). The former size category may be primarily (if not entirely) Omura's whale, whereas the larger whales – one of unknown sex of 12 m (39.4 ft) and two females of 13 m (42.7 ft) – would be the larger, offshore form of Bryde's whale. Of those smaller whales, four males ranged from 6.7 to 9.8 m (22.0 to 32.2 ft), four females ranged from 4.9 to 9.3 m (16.1 to 30.5 ft), and one of unknown sex was 9.4 m (30.8 ft).^[23][24]

Lone individuals seen off Madagascar were estimated to range between 8 and 12 m (26.2 to 39.4 ft), while calves were estimated to be between 3 and 5 m (9.8 to 16.4 ft).^[17]

The identity of three mature specimens (two females and a male) examined by biologist Graham Chittleborough in 1958 at a whaling station in Western Australia, which ranged in length from 10.6 to 11.74 m (34.8 to 38.5 ft), is uncertain – they may refer to Omura's whale or the smaller form of Bryde's whale (B. edeni). These three individuals were noted to have very small baleen plates – about 22 cm (8.8 in) by 15 cm (5.9 in), about 22 cm (8.8 in) by 16 cm (6.3 in), and 23.5 by 17.5 cm (9.3 by 6.9 in), respectively – with length-breadth quotients of 1.34 to 1.46, within the upper range (1.00-1.43) of the 9 specimens included in the formal description of Omura's whale, but also within the lower range of the Bryde's whale complex (1.2 to 1.33). The holotype of the smaller form of Bryde's whale (B. edeni) from Myanmar, though, had baleen plates of 30 by 15 cm (11.8 by 5.9 in), or a length-breadth quotient of exactly 2.0 – within the typical range of the Bryde's whale complex (1.8 to 2.4).^{[1][11][25][26][27]}

Mating

Of the three females caught in the Solomon Sea, two were ovulating and lactating and one was resting (not lactating, ovulating, or pregnant), while one of the two females caught near the Cocos Islands was accompanied by a calf estimated to be about 3 m (9.8 ft) in length.^[10][11] Nothing is known of the duration of gestation and lactation, and little is known of the timing or extent of breeding seasons. In August 2005, a 3.2 m (10 ft) female neonate with fetal folds and folded dorsal fin and flukes stranded at Miyazaki, Miyazaki Prefecture, on the eastern coast of Kyushu.^[28][29] Off northwestern Madagascar, six different cow-calf pairs were seen: one in August 2011, three in November 2013, and two in August 2015, suggesting a protracted calving season. The three calves observed in November had bent dorsal fins (indicating that they were fairly young) but did not have fetal folds, while one of the calves sighted in August had an erect dorsal fin, indicating that it was older but still probably born that year. These calves were estimated to range in length from 3 to 5 m (9.8 to 16.4 ft).^[17]

Behavior and diet

breaching off Nosy Be, Madagascar

Little is known of the behavior and diet of Omura's whale. Their blow is low and diffuse. After surfacing, the dorsal fin is usually not visible until after the head and splashguard have disappeared and they don't fluke when diving. They have been seen lunge feeding, defecating, and breaching off both Komodo National Park and northwestern Madagascar; they've also been seen rolling at the surface in apparent mating (the last of which allowed the identification of a male) off the former area.^[30][17] Off Madagascar, average group size was only 1.1 individuals (272 individuals in 247 groups), but loose aggregations of as many as a dozen whales could be seen. A total of thirteen cow-calf pairs were observed between 2011 and 2016, including a female first seen in an aggregation in 2012, then with a calf in 2013, and alone again in 2015 and 2017, showing that individuals can exhibit strong site fidelity.^[31]

The six paratypes taken in the Solomon Sea in 1976 reportedly only had krill (Euphausia diomedeae) in their stomachs,^[1][32] while crustaceans and fish were found in a 7 m (23 ft) female from Japan. Individuals in Madagascar have been observed lunge feeding on the krill Pseudeuphausia latifrons.^[31]

Song

Omura's whale produce amplitude-modulated songs of 15-50 Hz with a peak frequency of 36.1 Hz and an average duration of 9.2 seconds.^[17] This is sometimes followed by a tonal call of 17 Hz and four seconds in duration. These songs are repeated every two to three minutes, sometimes for as long as thirteen hours. Songs have been recorded off northwest Madagascar year-round, with peak activity from late October to late January and again from late May to late June. Overlapping choruses of several singing individuals have been recorded throughout the year as well.^[31]

Movements

Four Omura's whales were satellite-tagged off northwest Madagascar in November 2016. The tags stayed on an average of 42 days (range: 30–58 days). The tagged whales traveled an average of 2,530 km (range: 2,148 to 3,181 km) but remained within a small coastal range of only 230 to 405 km (average: 283 km) off the northwest coast of the island. All whales traversed their entire individual ranges several times, spending most of their time on shelf waters and rarely venturing into deep waters.^[31]

Range

Distribution in western Pacific Ocean

Omura's whale are found in the Indo-Pacific and the Atlantic Oceans, primarily in shelf waters between 35° N and 35° S, with the majority of records in the tropics (between 23° 26' N and 23° 26' S).^[19] Their range includes southern Japan (with strandings and entanglements recorded in March and from May to October; including the prefectures of Yamaguchi,^[33] Miyazaki,^[34] Kagawa,^[35] Mie, Shizuoka, and Chiba),^[19] South Korea^[36] (December to January, from the provinces of South Jeolla and South Gyeongsang),^[19] China^[37][38] (with strandings from November to February and in August; including the provinces of Zhejiang, Fujian, Guangdong,^[18] and Guangxi),^[20] Taiwan (with strandings from November to March and in May; there are also sightings from April to May and July to August),^[14][39] Hong Kong (March),^[40][41] the Philippines^[42] (Manila Bay, Busuanga,^[19] and the Bohol Sea),^[24] Vietnam (Quảng Ngãi Province),^[19] Malaysia (Pahang),^[43] Thailand (with sightings and strandings from February, May to June, and November to December; including the provinces of Phang Nga, Phuket,^[14] Prachuap Khiri Khan, and Songkhla),^[19] Indonesia (with sightings and strandings from February, April to June, and from September to November; with records from West Sumatra, the southern Java Sea, Bali,^[19] Komodo,^[30] the Solor Archipelago, Seram, Raja Ampat Islands, and East Kalimantan),^[19] the Cocos (Keeling) Islands,^[5] the Andaman Islands (April),^[19] Australia (Western Australia from Exmouth^[44] to north of Darwin in the Northern Territory at about 9° 30' S - 10° S, 130° E),^[45] South Australia^[46] (January, Gulf St Vincent), Queensland (November to December, Port Douglas and Mission Beach),^[47] the Solomon Islands,^[48] New Caledonia,^[49] Sri Lanka (February),^[50] the Chagos Archipelago,^[19] Iran (September, Strait of Hormuz),^[51] Egypt (April, the northern Red Sea)^[19] northwestern Madagascar (12° 01' S to 19° 23' S, with sightings by researchers from August and October to December, by whale watch operators from April to December, and acoustically detected year-round),^[31] Mauritania (November, Trarza Region),^[52] Brazil (September, Ceará),^[21] and in the vicinity of the Saint Peter and Saint Paul Archipelago.^[19]

Sightings

In 1999 and 2000, an unidentified species of rorqual was repeatedly seen in the waters of Komodo National Park. They were small (most estimated to be only 7 to 10 m (23 to 33 ft) in length) with asymmetrical coloration similar to the fin whale, only had a single prominent ridge on the rostrum, and an extremely hooked dorsal fin. At first, they were tentatively identified as a "pygmy or regionally distinct" form of Bryde's whale, which was confirmed when one was photographed and biopsied in October 2000 and its tissue sample sent to the Southwest Fisheries Science Center in La Jolla, California. There, its DNA was analyzed and found to be a complete match with a "pygmy Bryde's" sample obtained from the Philippines – later, however, it was discovered samples from the Philippines corresponded to B. omurai and not B. edeni.^[1][3][30]

During marine mammal surveys conducted in the Solomon Islands in 2009 and 2010, what were "most likely" Omura's whales were sighted on three occasions. They were estimated to be 6 to 10 m (20 to 33 ft) in length and lacked obvious auxiliary ridges. The sightings were made very close to shore (within a few hundred meters), one on the west coast of Malaita in November 2009, one on the northwest coast of Guadalcanal in November 2010, and a pair observed feeding within the Sandfly Passage of the Florida Islands on 14 November 2010.^[48]

In October 2015, an international team of scientists, led by Salvatore Cerchio of the New England Aquarium and Woods Hole Oceanographic Institution, released the first images and field observations of the species from a population off northwestern Madagascar.^[53] Forty-four sightings of Omura's whale were made between 2011 and 2014, with the majority in 2013 (thirteen) and 2014 (twenty-five). Forty-two were made off Nosy Iranja and the Ampasindava Peninsula, while only two occurred off Nosy Be. They were observed in open shelf waters that averaged 31 m (100 ft) deep (range: 4 to 202 m, or 13.1 to 662 ft) and were never seen in deep waters off the shelf break or in shallower coastal waters or embayments.^[17]

In 2018, Pierre Laboute and Philippe Borsa published a paper on sightings of Omura's whale made off Nosy Be in 1991–1995, 1998, and 2000, including photographs of an aggregation of a dozen whales seen skim and lunge feeding in 40 to 80 m (130 to 260 ft) of water in November 1994 at 13° 26' S, 48° 05' E.^[54]

In 2017, the first confirmed live sightings of Omura's whale were made off Taiwan^[55] and Sri Lanka.^[50]

Hunting and other mortality

Artisanal whaling

Photograph showing a small rorqual taken by villagers of Lamakera between 1915 and 1944. This is thought to likely be an Omura's whale (see text).

As early as the late 19th century, the natives of Lila, Bohol, began hunting whales in the Bohol Sea. By the turn of the century, this had spread to nearby Pamilacan Island and later to Sagay, Camiguin. At Pamilacan, whales were caught as early as January and as late as June, but most were taken in April and May. When a whale was spotted from shore, between 10 and 20 pump boats (boats with motors originally used for pumps) were launched in chase. When within range, a "hookman" jumped onto the whale's head and stabbed it with a 35-cm-long, 22.5-cm-wide stainless steel hook attached to a heavy line of 30 m (98 ft) with a 2 m (6.6 ft) bamboo spar buoy at the end of it. At Camiguin, they harpooned it with a toggle-headed grommet harpoon with a 2.5 m (8.2 ft) wooden shaft similar to the "dolphin irons" used by American whalemen in the mid-19th century, which in turn was either attached to a 140 m (460 ft) rope with a plastic fishing float or a 400 m (1,300 ft) rope with a plastic float or oil drum at the end. After an hour or more, the whale tired, and men took turns cutting it until it died. The boats usually towed the carcass to Lila for butchering, where it was sold and the meat eaten raw or cooked. Pamilacan hunters alone caught 10 to 20 per year, whereas at Camiguin, they caught them only sporadically.^[23]

When Maria Louella L. Dolar and colleagues (1994) examined photographs or baleen of the whales caught in the Bohol Sea between 1991 and 1993, they identified them as Bryde's whales; this was supported by osteological examinations of skulls collected from the same sites by Dolar, William F. Perrin, and others (1996), who suggested they were a "small form" of Bryde's whale. The specimens were deposited in the collections of the Marine Research Laboratory of Silliman University in Dumaguete, Negros Oriental, Philippines, where they were examined by T. K. Yamada and co-workers (2008). They discovered that 24 of the skulls were actually from Omura's whales, whereas only four were from the Indo-Pacific Bryde's whale (B. brydei). This was supported by genetic studies, which found that, based on comparison of published phylogenies, the small "Bryde's whales" from the Philippines correspond to Omura's whale.^{[7][23][24][56]}

A monograph from 1923 describes three skulls of balaenopterids taken by native whalers in Indonesia. Later examination of photographs of those skulls by one of the scientists (Tadasu K. Yamada) that had formally described Omura's whale showed that two of them, one from Bangsri, Java, and another from Lamakera, Solor, belonged to B. omurai. There is also a photograph (taken between 1915 and 1944) of a whale caught by the villagers of Lamakera that "strongly resembles a young Omura's whale in size and shape".^[19]

Commercial whaling

Among the small "Bryde's whale" caught 40 mi off Shionomisaki, Wakayama Prefecture, in June 1976, were two sexually mature females of 7.9 m (25.9 ft) and 8.5 m (27.9 ft), both of which are thought to likely be Omura's whale.^[19]

Scientific whaling

Of the eight individuals taken by Japanese scientific whaling in the 1970s, six were processed aboard the factory ship Tonan Maru No. 2 in the Solomon Sea (9°49'-10°17'S, 157°29'-157°56'E) on 24 October 1976, and two were processed aboard the factory ship Nisshin Maru No. 3 near the Cocos Islands ( and , respectively) on 15 and 17 November 1978.^[5][10][57]

Bycatch

Three of the seven records from Japan involve bycaught individuals, including a 9.2 m (30.1 ft) male in Sagami Bay in October 2003, a 10.05 m (33 ft) female in Tokyo Bay in May 2004, and a 6.3 m (20.7 ft) female near Ise Bay in March 2012. Both records from South Korea were individuals taken as bycatch, including a 6.3 m (20.7 ft) female off Geoje in January 2004 and a 6.4 m (21 ft) male off Goheung in December 2006. A 4.4 m (14.4 ft) male calf was also caught in small-mesh herring seine nets in the Gulf of Thailand, Songkhla Province, in May 2011, while a 7.5 m (24.6 ft) whale (thought to likely be an Omura's whale) was caught in fishing gear off Negombo, Sri Lanka, in August 1985.^[19] A live whale seen off Sri Lanka in 2017 also had a scar on its rostrum suggestive of an entanglement with fishing gear.^[50]

Ship strikes

Two individuals of Omura's whale were victims of ship strike, including the holotype of the species, an 11 m (36.1 ft) female found off Tsunoshima in the Sea of Japan in September 1998, and a whale brought into Manila Bay on the bow of a ship.^[19]

Conservation

Omura's whale is listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals. It is listed on Appendix II as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.^[58]

In addition, Omura's whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU).^[59]

See also

• List of cetaceans
• Baleen whale

References

El rorcual de Omura o rorcual aleta enano (Balaenoptera omurai) es una especie de cetáceo misticeto de la familia Balaenopteridae del que todavía se conoce muy poco, pues su descubrimiento fue anunciado en 2003. Recibe su nombre en honor de Hideo Omura.

Nueva especie

El anuncio de su clasificación taxonómica fue realizado el 20 de noviembre de 2003 en la edición 426 de la revista Nature, por tres científicos japoneses: Shiro Wada, Masayuki Oishi y Tadasu K. Yamada. Los tres científicos determinaron la existencia de la especie analizando la morfología y el ADN mitocondrial de nueve ejemplares, ocho de ellos capturados por una navío japonés de investigación a fines de la década de 1970 y otro más atrapado en 1998 en una pequeña isla del mar de Japón.

En la tercera edición del Mammal Species of the World, la especie es relegada a un sinónimo del rorcual de Bryde.^[3]​ Sin embargo los autores resaltan que esto es una medida provisoria. La base de datos ITIS la relaciona como un taxón válido, anotando una advertencia sobre la clasificación factible de la especie como, Balaenoptera edeni y Balaenoptera brydei.^[4]​

Descripción

Además del patrimonio genético específico, el rorcual de Omura se diferencia de los otros rorcuales por algunas particularidades morfológicas en el cráneo y poseer un menor número de barbas. Su apariencia externa es semejante al rorcual común, pero con un tamaño inferior, pues no supera los 12 metros de longitud.^[5]​

Población y distribución

La distribución de los rorcuales de Omura es poco conocida debido a que hasta la fecha muy pocos especímenes han sido confirmados.

Los primeros individuos fueron recogidos cerca de Oyama en el sur del Mar de Japón en 1998. En 1970, con la caza científica de ballenas se tomaron ocho muestras,que en un principio se pensaron que correspondían a rorcuales de Bryde, pero estudios genéticos posteriores confirmaron que se trataban de rorcuales de Omura. Otras muestras más fueron tomadas en las islas Salomón, dos más en aguas cercanas a las Islas Cocos y en el mar de Bohol.^[6]​

Referencias

Balaenoptera omurai oso gutxi ezagutzen dugun zere espezie bat da^[1]. Bere deskripzio formalaren aurretik askotan agertzen zen Balaenoptera edeni espeziearen bertsio nano gisa. Izena Hideo Omura japoniar zetologoaren omenez darama^[2].

Deskribapena 2003an egin zuen Nature aldizkarian japoniar zientzialari talde batek. Bederatzi aleren DNA mitokondriala eta morfologia aztertuta determinatu zuten beste espezie bat zela. Beranduago aurkitutako beste ale batzuen genetikak demostratu du espezie ezberdina direla eta zereen eboluzioan bereizitako lehen espezieetako bat dela. Baliteke balea urdinaren ahaide gertukoa izatea^[2][3].

Erreferentziak

Kanpo estekak

Omuranvalas (Balaenoptera omurai) on erittäin harvinainen uurteisvalaisiin kuuluva valaslaji.

Lähteet

Aiheesta muualla

• Mystinen valas löytyi ensimmäistä kertaa elossa Yle.fi 31.10.2015
• Omura’s whales (Balaenoptera omurai) off northwest Madagascar Royal Society Publishing 14.10.2015

Balaenoptera omurai

Le Rorqual d'Omura (Balaenoptera omurai) est une espèce de cétacés de la famille de Balaenopteridae. Elle a été identifiée en 2003 par une équipe de chercheurs japonais, Shiro Wada (d), Masayuki Oishi (d) et Tadasu K. Yamada (d)^[2]. Il mesure de 9 à 11 m de long^[3].

Photographie prise au large des côtes de Nosy Be, Madagascar du rorqual d'Omura dans son milieu naturel^[4],[5].

Ce rorqual a été photographié pour la première fois en milieu naturel au large de Nosy Be (Madagascar) en 1994^[6], mais ce n'est qu'en 2012-2014 que des observations approfondies sont réalisées, dans la même zone^[7]. Une femelle s'est échouée le 14 avril 2015 sur une plage d'Australie-Occidentale près d’Exmouth. C'est la seconde fois seulement que ce rorqual est observé en Australie^[8]. Balaenoptera omurai a été identifié pour la première fois en Atlantique Nord le long des cotes Mauritaniennes^[9].

Notes et références

• (en) Cet article est partiellement ou en totalité issu de l’article de Wikipédia en anglais intitulé .

O rorcual de Omura, Balaenoptera omurai,^[2] é un unha especie de mamífero mariño da orde dos cetáceos, suborde dos misticetos e familia dos balenoptéridos, unha das sete que integran o xénero Balaenoptera, e da que aínda se coñece moi puoco, xa que o seu descubrimento foi anunciado no 2003.

Unha femia encontrouse varada o 14 de abril de 2015 nunha praia de Australia Occidental, preto de Exmouth. Foi a segunda vez que este rorcual foi observado en Australia.^[4]

Este rorcual foi filmado por primeira vez na natureza na costa de Madagascar no ano 2015.^[5]

Taxonomía

Descrición

A especie foi identificada, e descrita, por un equipo de investigadores xaponeses formado por Shiro Wada, Masayuki Oishi e Tadasu K. Yamada.^[6]

Nome específico

O nome específico, omurai, que significa 'de Omura', débese a que foi descuberto preto de Ōmura, un concello xaponés da prefectura de Nagasaki.

Notas

Véxase tamén

Bibliografía

• Schokkenbroek, Joost C. A. (2008): Trying-out: An Anatomy of Dutch Whaling and Sealing in the Nineteenth Century, 1815-1885. Amsterdam: Aksant Academic Publishers. ISBN 978-90-5260-283-7.

Outros artigos

• Cetáceos
• Misticetos
• Balenoptéridos
• Balenopterinos

Balaenoptera omurai atau Paus Gembala Laut adalah spesies paus yang informasinya tidak banyak diketahui dan memiliki sedikit nama umum. Pengumuman ditemukannya paus ini diumumkan pada 20 November 2003, edisi majalah Nature (426, 278-281) oleh tiga ilmuwan Jepang, Shiro Wada, Masayuki Oishi dan Tadasu K. Yamada.

Referensi

• Wada, S., Oishi, M., and Yamada, T.K. 2003. A newly discovered species of living baleen whales. Nature 426: 278–281.
• Sasaki, T., Nikaido, M., Wada, S., Yamada, T.K., Cao, Y., Hasegawa, M., and Okada, N. 2006. Balaenoptera omurai is a newly discovered baleen whale that represents an ancient evolutionary lineage. Molecular Phylogenetics and Evolution 41(1): 40–52.

Balaenoptera omurai^[2][3] (Wada, Oishi & Yamada, 2003), conosciuta come Balenottera di Omura^[4], in onore del cetologo giapponese Hideo Omura, è una specie di balenottera della famiglia Balaenopteridae. Nomi comuni: Omura’s whale (inglese), Rorqual d'Omura (francese). La sua scoperta è stata annunciata su Nature (426, 278-281) da tre scienziati giapponesi, Shiro Wada, Masayuki Oishi e Tadasu K. Yamada, il 20 novembre del 2003.

Comunque, la maggior parte della comunità cetologica ha accettato con cautela l'annuncio della scoperta di questa nuova specie. Sul New York Times, ad esempio, il Dr. Howard C. Rosenbaum, un biologo conservazionista della Wildlife Conservation Society, ha sostenuto che i ricercatori giapponesi hanno fatto «un lavoro ammirevole per dimostrare l'appartenenza ad una specie distinta», ma aggiunge che sono necessarie ulteriori analisi del DNA.

Balaenoptera omurai mentre si nutre al largo del Madagascar

I tre scienziati hanno determinato l'esistenza della specie analizzando la morfologia e il DNA mitocondriale di nove esemplari - otto catturati da una nave di ricerca giapponese alla fine degli anni '70 nell'Indo-Pacifico ed un altro trovato arenato su una piccola isola del Mar del Giappone nel 1998.

Nel loro studio, gli scienziati hanno descritto la nuova specie come simile nell'aspetto alla balenottera comune, sebbene sia di dimensioni più piccole.

Nella terza edizione di Mammal Species of the World, questa «specie» è stata relegata come sinonimo della balenottera di Bryde. Comunque, gli autori hanno specificato che questa collocazione è solo temporanea.

Note

Bibliografia

• Wada, S., Oishi, M., and Yamada, T.K. 2003. A newly discovered species of living baleen whales. Nature 426: 278–281.
• Sasaki, T., Nikaido, M., Wada, S., Yamada, T.K., Cao, Y., Hasegawa, M., and Okada, N. 2006. Balaenoptera omurai is a newly discovered baleen whale that represents an ancient evolutionary lineage. Molecular Phylogenetics and Evolution 41(1): 40–52.

Balaenoptera omurai (ang. Sea Shepherd Whale) – banginių rūšis, apie kurią beveik nieko nėra žinoma. Ji neturi bendro vardo. Šio banginio atradimo data laikoma 2003 m. lapkričio 20-oji. Pirmą kartą rūšis paminėta leidinyje „Nature“, trijų Japonijos mokslininkų Shiro Wada, Masayuki Oishi ir Tadasu K. Yamada.

Ar ši nauja rūšis bus patvirtinta – dar nėra aišku. Daktaras Howard C. Rosenbaum „New York Times“ pasakė, kad Japonijos tyrėjai padarė labai gerą darbą užduodami klausimą, ar tai yra skirtinga rūšis, bet pridūrė, jog dar reikia atlikti tikslingesnius DNR tyrimus, kad galutinai būtų atsakyta į šį klausimą. Jei būtų patvirtinta, jog tai atskira rūšis, tai bendras vardas banginiui tikėtina bus Sea Shepherd Whale (ang.) (Jūros piemens banginis), japonų tyrinėtojo Hideo Omura garbei.

Trys mokslininkai nustatė rūšies egzistavimą, analizuodami devynių individų morfologiją ir DNR – aštuoni sugauti japonų tyrinėtojų 1970-ųjų pabaigoje iš Indijos bei Ramiojo vandenyno ir 1998 metais iš mažos salos Japonijos jūroje. Jie jį apibūdina panašiu į Finvalą, bet mažesniu už jį.

De omurawalvis (Balaenoptera omurai) is een soort vinvis uit het geslacht Balaenoptera. Vroeger werd de soort gerekend tot de brydevinvis (B. brydei) of Edens vinvis (B. edeni) - waarvan nog onduidelijk is of het één of twee soorten zijn - maar sinds 2006 wordt de omurawalvis door het IUCN en de Internationale Walvisvaartcommissie^[3] als een fylogenetisch verschillende soort beschouwd.

Hoewel de soort als apart wordt beschouwd, kan nog blijken dat de wetenschappelijke naam B. omurai niet geldig is en vervangen moet worden. Dit is te wijten aan het onzekere karakter van het holotype van B. edeni, waarvan niet bepaald is of het behoort tot de Edens vinvis of de brydevinvis zoals die bekendstaan. B. omurai werd vergeleken met een ander specimen, waarvan vermoed wordt dat het B. edeni betreft. Mogelijk is het holotype echter van een andere soort dan van dit specimen. Mocht blijken dat het holotype van B. edeni en B. omurai één soort betreffen, dan is B. edeni de juiste naam voor deze soort. Het typespecimen van B. edeni kan echter ook van de soort zijn die nu bekendstaat als de brydevinvis of inderdaad van de Edens vinvis zoals bekend van het latere specimen.^[1][4]

Naamgeving

De soortaanduiding omurai eert Hideo Omura, een Japanse walviskundige, voor zijn bijdragen aan de kennis over walvissen.^[2]

Leefgebied

Er zijn weinig specimina van de omurawalvis bekend, waardoor zijn volledige leefgebied nog niet helemaal zeker is. Hij komt voor in de Indische en Stille Oceaan. Ze werden waargenomen nabij de Cocoseilanden, Indonesië, Japan, Maleisië, de Filipijnen en de Salomonseilanden. Hij komt zowel in diep water als in kustgebieden.^[1]

Kenmerken

De soort onderscheidt zich van zijn verwanten door de morfologie van de schedel (breed en plat) en het lage aantal baleinen (circa 200 aan elke kant). De voorste baleinen zijn geelwit, de achterste zwart, de middelste hebben beide kleuren. De snuit wordt smaller vanaf de basis. De soort is kleiner dan de brydevinvis/Edens vinvis: een exemplaar wordt tussen 9,6 tot 12 meter lang; de vrouwtjes zijn groter dan de mannetjes. Uiterlijk lijkt de omurawalvis wat op de gewone vinvis. Zo zijn de voor- en onderzijde van de borstvinnen wit en is de onderkant asymmetrisch. De linkerkant van de keel is gepigmenteerd, de rest van de buikzijde is wit. De staartvin is onderaan wit met een zwarte rand. Het aantal buikplooien wordt op 80 tot 90 geschat. In tegenstelling tot de brydevinvis heeft de omurawalvis geen opstaande randen op de zijkanten van het hoofd; het hoofd is echter ook niet compleet glad.^[2][4]

Omurawalvissen leven niet in grote groepen, maar in losse groepen van enkele exemplaren, die niet dicht bij elkaar zitten, maar wel op hoorbare afstand blijven. Ze zingen een lage, herhalende melodie die meer dan uur kan duren. Sporadisch verheffen meerdere individuen samen hun stem; de reden daarvoor is nog niet helemaal zeker.^[5]

Fylogenie

De omurawalvis vormt een monofyletische groep met de brydevinvis/Edens vinvis, noordse vinvis en blauwe vinvis. Hoewel de omurawalvis tot de brydevinvis/Edens vinvis werd gerekend, wijst fylogenetisch onderzoek uit dat de soort zich - net als de blauwe vinvis - eerder afsplitste dan de brydevinvis, Edens vinvis en de noordse vinvis onderling.^[2][6]

Referenties

Omuras dvergbrydehval (Balaenoptera omurai) er en liten nyoppdaget bardehval i finnhvalfamilien. Den tilhører de ekte finnhvalene og er svært lik dvergbrydehval og brydehval, men skiller seg fra disse på vesentlige punkter. Navnet Omuras dvergbrydehval er nå offentlig akseptert.^[1]

Beskrivelse

Omuras dvergbrydehval er en typisk finnhval med en lang og slank, nærmest torpedolignende kropp, men den skiller seg fra dvergbrydehvalen og brydehvalen på flere punkter og har derfor blitt annonsert som en egen art. Den blir trolig omkring 8-14 meter lang (et av eksemplerene som ble studert var 12 meter). Hunnene blir marginalt større enn hannene.

Annet

DNA-studier viser at Omuras dvergbrydehval, dvergbrydehval og brydehval er individuelt nærmere beslektet med seihval enn de er med hverandre.Studien viser også at Omuras dvergbrydehval var den av de tre artene som først ble separert fra en felles stamfar med blåhvalen.^[2] Omuras dvergbrydehval skiller seg på vesentlige punkter fra de to andre brydene, blant annet gjennom distinkte forskjeller i både DNA-profilen og morfologi. Den har blant annet forskjeller i kraniets struktur og (kanskje spesielt) den har færre bardeplater. Den samme studien viser også at dvergbrydehval og brydehval er nært beslekta søsterarter som bare fjernt er beslektet med Omuras dvergbrydehval.

Omuras dvergbrydehval er oppkalt etter den japanske cetologen Hideo Omura. Den ble først beskrevet av de tre japanske forskerne Shiro Wada, Masayuki Oishi og Tadasu K. Yamada i en artikkel i det vitenskapelige magasinet Nature (426, 278-281) den 20. november 2003. Wada, Oishi og Yamada fastslo arten eksistens gjennom analyser av morfologi og mtDNA for ni individer. Åtte av disse ble opprinnelig fanget av et japansk forskningsfartøy på slutten av 1970-tallet og befant seg på et museum, mens det niende eksemplaret ble fanget i 1998 utenfor ei av de japanske øyene.

Hvorvidt Omuras dvergbrydehval blir akseptert som en egen art gjenstår å se. Flere forskere har i senere tid advart sterkt mot å inndele dyr i flere arter enn strengt talt nødvendig, slik tendensen har vært de siste årene. Mange mener at både Omuras dvergbrydehval, dvergbrydehval og brydehval trenger ytterligere studier før de evetuelt kan klassfiseres som separate arter. Dette ar bakgrunn i at moderne teknologi i større grad finner forskjeller som gjør det mulig å dele dyr inn i flere arter enn tidligere, men det hersker stor uenighet omkring hvor grensene for artsdannelse skal trekkes.

Referanser

Eksterne lenker

• (en) Omuras dvergbrydehval – oversikt og omtale av artene i WORMS-databasen
• (en) Omuras dvergbrydehval i Encyclopedia of Life
• (en) Omuras dvergbrydehval i Global Biodiversity Information Facility
• (en) Omuras dvergbrydehval hos Fossilworks
• (en) Omuras dvergbrydehval hos NCBI
• (en) Omuras dvergbrydehval hos ITIS
• (en) Kategori:Balaenoptera omurai – bilder, video eller lyd på Wikimedia Commons
• Balaenoptera omurai – detaljert informasjon på Wikispecies
• John Roach. 2003. «New Whale Species Announced by Japanese Scientists». National Geographic News.

Denne zoologirelaterte artikkelen er foreløpig kort eller mangelfull, og du kan hjelpe Wikipedia ved å utvide den.
Det finnes mer utfyllende artikkel/artikler på .

Czaszka płetwala skrytego

Płetwal skryty^[3] (Balaenoptera omurai) – mało poznany gatunek ssaka z rodziny płetwalowatych (Balaenopteridae). Po raz pierwszy opisany przez trzech japońskich biologów Shiro Wada, Masayuki Oishi i Tadasu K. Yamada w 2003 roku (w wydaniu Nature z 20 listopada)^[4].

Po opublikowaniu pracy pojawiły się głosy, według których japońscy naukowcy postąpili zbyt pochopnie, bazując jedynie na cechach morfologicznych. Jednak analiza DNA przeprowadzona w 2006 roku potwierdziła ważność gatunku^[5].

Płetwal skryty mierzy około 10 metrów długości, jest koloru szarego z wyjątkiem białej plamy na dolnej szczęce. Żywi się planktonem. Z dotychczasowych informacji, wiele wskazuje, że walenie rozmnażają się przy wschodnim wybrzeżu Afryki^[6].

W 2015 roku zespół badaczy pod kierownictwem biologa morskiego Salvatore Cerchio poinformował, że udało się zaobserwować i udokumentować grupę około 25 osobników tego gatunku u wybrzeży Madagaskaru^[7].

Przypisy

A baleia-de-Omura, Balaenoptera omurai é um mamífero cetáceo da família dos balenopterídeos, descoberta em novembro de 2003 por três cientistas japoneses Shiro Wada, Masayuki Oishi e Tadasu K. Yamada.^[1]

Em 2013 a baleia-de-Omura foi vista pela primera vez em Madagáscar.

Referências

Balaenoptera omurai är en art i familjen fenvalar (Balaenopteridae) som i sin tur tillhör underordningen bardvalar (Mysticeti). Arten beskrevs 2003 för första gången.

Enligt forskarna Shiro Wada, Masayuki Oishi och Tadasu K. Yamada liknar arten en sillval (Balaenoptera physalus) men är med en genomsnittlig längd av 12 meter betydligt mindre. Dessutom har arten bara 200 barder, vilket som är ovanligt för bardvalar. Om deras levnadssätt är ingenting känt.

Den första beskrivningen gjordes i tidskriften Nature den 20 november 2003. Uppgiften som bekräftades med genetiska undersökningar var sedan omstridd bland andra biologer. Analyserna ska ha gjorts med individer som fångades under 1970-talet. Med det vetenskapliga namnet är arten uppkallad efter den japanska valforskaren Hideo Omura.

Källor

Den här artikeln är helt eller delvis baserad på material från tyskspråkiga Wikipedia

1. ^ Balaenoptera omurai på IUCN:s rödlista, auktor: Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N. 2008, besökt 20 mars 2009.

Externa länkar

• Wikimedia Commons har media som rör Balaenoptera omurai.
  Bilder & media
• kort version av bidraget i Nature
• National Geographic – New Whale Species Announced by Japanese Scientists

Balaenoptera omurai oluklu balinagiller familyasına ait bir balina türü. Hakkında çok az şey bilinmektedir.^[1]

Ayrıca bakınız

• Oluklu balinagiller
• Tehlikedeki türler
• Balinalar ve yunuslar listesi

Kaynakça

Смуга́ч Омури (Balaenoptera omurai) — вид ссавців з родини смугачеві (Balaenopteridae) ряду китоподібні. Раніше розглядався як карликова форма смугача Брайда. Нині (січень 2007), генетична ідентичність визначена для дев'яти зразків. Морфологічний опис доступно тільки для типового зразка.

Поширення

Країни: Кокосові острови; Індонезія; Японія; Малайзія; Філіппіни; Соломонові острови. Діапазон поширення смугача Омури погано відомий, тому що на сьогоднішній день дуже небагато особин було підтверджено. B. omurai щонайменше частково симпатричний зі смугачем Брайда (Б. edeni / brydei), і зустрічається як в глибокій воді так і в прибережних районах.

Джерела

• Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N. 2008. Balaenoptera omurai. The IUCN

Cá voi Omura (Balaenoptera omurai) là một loài cá voi trong họ cá voi lưng xám, có rất ít thông tin về loài này.^[2]

Sọ của cá voi Omura tại Bảo tàng Khoa học Tự nhiên Quốc gia của Nhật Bản.

Loài này được 3 nhà khoa học Nhật Bản gồm Shiro Wada, Masayuki Oishi và Tadasu K. Yamada mô tả khoa học năm 2003, trong một ấn phẩm của tạp chí Nature (426, 278–281). Các nhà khoa học này xác nhận sự hiện diện của loài này thông qan phân tích hình thái học và mitochondrial DNA của 9 cá thể bao gồm 8 cá thể bắt được bởi một tàu nghiên cứu của Nhật vào thập niên 1970 trong vùng biển Ấn Độ Dương-Thái Bình Dương và một tiêu bản được thu thập năm 1998 ở đảo Tsunoshima thuộc biển Nhật Bản. Từ các bằng chứng về gen phong phú đã xác nhận cá voi Omura là một loài riêng biệt và cho thấy nó là một nhóm tách ra từ rất sớm của họ Balaenoptiidae, sớm hơn cả cá voi Bryde và Sei. Nó có lẽ có quan hệ gần gũi hơn với nhóm họ hàng lớn hơn là cá voi xanh.^[3][4]

Tên gọi của nó được đặt theo tên của nhà cá voi học Nhật Bản Hideo Omura.^[3]

Chú thích

Tham khảo

Liên kết ngoài

• http://www.pacificcetaceans.org/ Official webpage of the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region

• Проверить достоверность указанной в статье информации.
• Исправить статью согласно стилистическим правилам Википедии.

保存於台灣台中市國立自然科學博物館的角島鯨頭骨

角島鯨又名大村鯨（學名：Balaenoptera omurai），屬鬚鯨科，直到2003年才被確認與命名。

因為模式標本是擱淺在日本山口縣的角島，故俗名「角島鯨」。它的學名omurai則是為了紀念日本的鯨豚學者大村秀雄。

成年角島鯨身長可達11公尺，屬中型鯨，外型極似長鬚鯨，但較長鬚鯨（體長可達26公尺）小很多。

分布

已知分布海域為西太平洋地區，在2015年於馬達加斯加外海，首次被用鏡頭捕捉到活動影像，台灣賞鯨業者則在2017年5月於花蓮外海拍攝到鯨魚的特徵是左下顎黑色色塊、胸鰭白色邊緣與背鰭形狀等，經多處特徵判定後，極可能就是罕見的「角島鯨」^[1][2][3][4]。標本來自日本、台灣、菲律賓、澳洲與所羅門群島，台灣的角島鯨標本，目前絕大多數保存於台中市的國立自然科學博物館^[5]。

發現史

1970年代末，和田志郎從遠洋水產研究所鯨魚資源實驗室研究被捕獲的鯨魚，由1976年太平洋熱帶海域所羅門海雌雄各三條鯨魚樣本及1978年在科科斯群島捕獲二條雌性鯨魚樣本中發現獨特基因。儘管鯨魚長度介於9.6米 - 11.5米，卻是成年鯨魚。當時和田志郎認為這些鯨魚是全新物種，並投稿至科學期刊《Nature》，但是被認為證據不足，並未刊登。

1998年9月11日，日本漁船與鯨魚在山口縣角島近海（本州之間的海域）相撞。根據報導指出，這條鯨魚體長約11米，在事故發生時已經死亡或瀕臨死亡。鯨魚和海豚在這個地區很少見，健康的鯨魚不太可能與慢速船隻碰撞。國家科學博物館山田格保存遺體，並交由漁業研究中心中央水產研究所、岩手縣立博物館、日本鯨類研究所進行研究。調查開始三天后，遺體腐敗嚴重，難以詳細調查易發生腐敗的部位，例如軟組織。然而，骨骼的狀況仍然表明這條鯨魚已經成年，因此可以肯定這條鯨魚不是未成年的大型鯨魚。此外，這條鯨魚髖骨的形態獨特，可能是病變個體或未知物種。頭骨也顯示出獨特的形狀。科學家從鼻骨周圍的形狀和線粒體的DNA確認這條鯨魚以及之前發現的八個標本是全新物種。

日本科學家和田志郎、大石雅之、山田格等三人於2003年11月20日在科學期刊《Nature》 發表論文^[6]，確認全新物種角島鯨。角島鯨長相易與長鬚鯨、布氏鯨、塞鯨等鬚鯨科成員混淆。為此歷經三年時間，作者遠赴所有標本可能出現國家，進行標本比對與鑑定。因在骨骼形態、鬚板數量（單側僅200片左右）及DNA分析結果確有獨特的特徵，證實為新種。

重要出沒紀錄及主要出没地点

• 石梯坪^[7][8]
• 花蓮^[4]

參考資料

ツノシマクジラ (Balaenoptera omurai) は日本で発見されたヒゲクジラの一種である。鯨偶蹄目 - ヒゲクジラ亜目 - ナガスクジラ科 - ナガスクジラ属に属する。種小名は日本の鯨学の祖、大村秀雄にちなんで名付けられた。また和名はホロタイプの産地である山口県豊浦郡豊北町の角島に由来する。命名、発表者は和田志郎、山田格、大石雅之の三名。

分布[編集]

これまで確認された個体数が少ないため、はっきりとした分布は分かっていない。標本が捕獲された地域は日本海、太平洋熱帯海域及びインド洋である。

形態・生態[編集]

体長は12m以下^[1]だが、洋上での目測で15mに達したとされる例も存在する^[2]。標本数が少ないため、平均値などは判明していない。また大型種の多いナガスクジラ属では比較的小柄である。同様に産まれた直後の体長なども不明。体色はナガスクジラに似て左右比対称。背面が濃いグレー、腹面は白であるが、左胸までグレーの部分が広がる。また胸びれの前縁と裏は白色となる。のどの畝状部は後方、臍まで達しその数は90近いなど、外観はナガスクジラの小型版といえる。しかし髭板は右列前方のみ黄白色の髭が見られ、それ以外では黄白色と黒のツートンあるいは黒一色であるなど体色と同様左側に黒い部分が多くなる。この特徴はクロミンククジラに似ている。また髭板の数は片側200枚前後で、他のヒゲクジラは大小問わず片側300枚持つことに比べて明らかに少ない点は、この種独特の形態である^[3]。

頭骨の形態は、上面から俯瞰すると上顎骨外縁部の吻端から頬にかけてのラインが丸みを帯びている。またクジラ類特有の左右上顎骨間にある深い溝の最大幅は、ナガスクジラ属では最も狭いなど独特の形態を見せる。^[3]

生態、生息数などについては詳細は不明である。2005年に宮崎県宮崎市の海岸に体長約3.2m程の幼体の雌が漂着したのが確認されている^[4]。

2015年マダガスカル沖にて子供を含む25頭程度の群れが発見された。

発見[編集]

1970年代末、命名、発表者の一人和田志郎は遠洋水産研究所鯨類資源研究室において、調査捕鯨により捕獲された、南半球産のニタリクジラの臓器標本の遺伝子解析を行っていたところ、1976年に太平洋熱帯海域（ソロモン海）産の雌雄各三体、1978年にココス諸島近海のインド洋産の雌二体の標本がユニークな遺伝子を持つ事を発見した。これらは体長が約9.6 - 11.5mと小型であるにも関わらず、成熟した個体であった。これらは新種の可能性があるとしてイギリスの総合学術雑誌「ネイチャー (Nature) に論文を投稿する運びとなった。しかし、形態情報の不足などを指摘され、投稿には至らなかった。このため和田はナガスクジラ属の形態を詳細に調査した結果、ニタリクジラとされるクジラには幾つかの種が含まれている事が判明した。当初ニタリクジラと呼ばれたB. brydeiと、後に同種とされたB. edeniは別種であり、また八体のクジラも別種であったと和田は結論付けた。新種クジラの骨格の形態に関するデータは揃っていなかった。和田は国立科学博物館の山田格の協力を得、八体のクジラを新種として公表する予定であった^[3]。

しかしその直後の1998年9月11日、日本海を航行中の漁船が山口県角島近海の海士ヶ瀬戸（本州との間の海域）においてクジラと衝突する事故が発生した。このクジラは体長約11mのヒゲクジラで、事故当時既に死んでいたか瀕死の状態であった可能性が指摘されている。これは、この海域でクジラやイルカの目撃例が稀であり、また健康な状態のクジラが低速の船と衝突する可能性が低いからである。このクジラは国立科学博物館の山田が確保、水産総合研究センター中央水産研究所、岩手県立博物館、日本鯨類研究所などで詳細に調査された。^[3]調査開始が三日後であったため腐敗がひどく、軟組織など腐敗しやすい部位の詳細な調査が難しかった。しかし化骨の状態は、すでにこの個体が十分に成熟、あるいは既に老齢であることを示していた。ナガスクジラなどは成体で20mを超えるため、大型種の幼体でないのは確かであった。また寛骨の形態が特異であり、病変個体あるいは未知の種である可能性が指摘された。また頭骨も独特の形態を示していた。鼻骨周辺の形やミトコンドリアのDNAなどから、この個体が先の八体の標本と同じく新種と結論付けた。このクジラは Balaenoptera omurai と名付けられ、「ネイチャー」^[5]にて論文が発表された^[6]。ヒゲクジラ類では新種の発見は1913年以来、90年ぶりとなった^[7]。

分類[編集]

1970年代に捕獲された個体が誤認されていた様に、ニタリクジラと類似した形態を持つ。元々この「ニタリクジラ」には複数の種が含まれていると考えられており^[8]、研究チームはこのクジラのDNAについても解析を行った。結果、ニタリクジラは三つの種に分割されると結論付けられている。一つはニタリクジラ Balaenoptera brydei、もう一つはカツオクジラBalaenoptera edeni、そしてこのツノシマクジラである^[9]。

和田らによれば、イワシクジラとニタリクジラ、カツオクジラ、ツノシマクジラは近縁で、最初に分岐したのがツノシマクジラ、次がカツオクジラ、そして（狭義）ニタリクジラとイワシクジラが姉妹群を成すという。

他のクジラ

シロナガスクジラ

ツノシマクジラ

カツオクジラ

ニタリクジラ

イワシクジラ

脚注[編集]

参考文献[編集]

• 村山司 『鯨類学』 東海大学出版会〈東海大学自然科学叢書〉、ISBN 978-4-486-01733-2。

外部リンク[編集]

• 海棲哺乳類図鑑 ツノシマクジラ
• ツノシマクジラ 日本で発見された新種のヒゲクジラ
• BBC NEWS Whale species is new to science（英語）
• 中央水研ニュースNo.34
• 海棲哺乳類情報データベース アーカイブ 宮崎県宮崎市でツノシマクジラの漂着

오무라고래(Balaenoptera omurai)는 고래 중 최근에 발견되어 거의 알려진 바가 없는 종이다. 아직까지 널리 불리는 통칭은 없어, 일본의 고래학자 오무라 히데오의 이름을 붙여 오무라고래라고 일컬어지거나 학명으로 불린다. 이들의 발견은 2003년 11월 20일에 일본의 과학자인 와다 시로, 오이시 마사유키 등에 의해 《네이처》지에 발표되었다. 3명의 과학자는 종의 존재를 형태와 연구선이 인도-태평양에서 잡은 8마리와 동해에서 발견된 개체의 미토콘드리아 DNA를 조사해 발견했다.

각주