Luminous Flying Squid

Eucleoteuthis luminosa (Sasaki, 1915)

DIAGNOSIS.—As for genus.

ORIGINAL REFERENCE.—Sasaki, 1915:144, fig. 4, pl. 4: figs. 7–13.

TYPE LOCALITY.—Sagami Bay, Japan.

DEPOSITION OF TYPES.—Holotype: Museum of the Science College, Tokyo Imperial University, Japan.

Paratypes: None designated.

DISTRIBUTION AND BIOLOGY.—This species is found across the North Pacific from about 20°N to 40°N. In the Southern Hemisphere it is found in all three major oceans at similar south latitudes (Figure 3), but records are not abundant in these areas (Zuev et al., 1975) due to less frequent sampling. It is considered to be a Transition Zone species (McGowan, 1971) by Wormuth (1976).

As is the case for most ommastrephids, little is known of its depth distribution. It occurs with Ommastrephes bartramii but is seen less frequently. This may be because of actual lower abundance or because it rarely approaches the surface. Little is known of its prey species or its reproductive behavior.

Males and females from waters off the east coast of Australia mature at between 120 mm ML and 130 mm ML (Dunning and Brandt, 1985). The broad size range encountered suggests a protracted spawning season.

Eucleoteuthis luminosa (Sasaki, 1915)

The striped squid or luminous flying squid, E. luminosa, has a distribution similar to that of O. bartramii, occurring in subtropical waters of the North and South Pacific but restricted to south of the equator in the Indian and Atlantic oceans (Zuev et al., 1975; Okutani, 1980). In the South Pacific, this species has previously been reported from around New Caledonia and Norfolk Island (Rancurel, 1970; Zuev et al., 1975) and eastward from the Kermadec Islands to 80°54′E off the coast of Chile (Wormuth, 1976; Polezhaev, 1986). Nesis (1979b) considered E. luminosa to be a peripheral species in the Australasian region.

Larval E. luminosa have been reported from off the eastern Australian coast between 14°30′S and 35°46′S, where sea surface temperatures (where recorded) ranged from 28° C to 20.6° C. Juveniles (<75 mm ML) were collected between 23°59′S and 37°45′S in water temperatures of 25.6° C to 19.1° C (Dunning, 1988c).

Nesis (1979c) reported larval and juvenile E. luminosa between 2 mm ML and 10 mm ML from a depth of 200 m near Norfolk Island; however, no specimens of this species were caught in towed plankton nets or surface scoop nets during summer Tasman Sea and southern Coral Sea surveys undertaken by Dunning (1988c).

Near the eastern Australian coast, adult E. luminosa have been caught between 23°59′S and 36°35′S (surface temperatures 25.6°–20.8° C). Single females also were jigged at two stations in the southeastern Coral Sea at 31°44′S, 164°58′E, and 30°03′S, 163°49′E, in late February 1982 and in the southwest Tasman Sea at 35°50′S, 156°38′E, in December 1982 (Dunning, 1988c). During January 1982, three specimens of E. luminosa were caught in midwater trawls where bottom depth exceeded 800 m. An additional 18 specimens trawled and jigged off the New South Wales coast were examined, and all were taken where water depth exceeded 600 m (Dunning, 1988c).

Symplectoteuthis luminosa Sasaki, 1915

Symplectoteuthis oualaniensis.—Watase, 1906, p. 195. Symplectoteuthis luminosa Sasaki, 1915, p.144, text fig. 4, pl.4, figs. 7–13; 1916, p.106; 1929, p.293, text fig. 140, pl.24, figs. 4–5.

Eucleoteuthis luminosa.—Berry, 1916, p.60.—Okada, 1927, p.4.

DESCRIPTION.—The mantle is long and slender (width 15–20% of length); anterior to the fins it is nearly cylindrical, but posteriorly it tapers to a point. The free margin is only slightly produced near the ventral locking-cartilages and not at all in the nuchal region. The mantle wall is extremely thick and muscular.

The fins are about 45–50% of the mantle in length and about 55–60% in total width. They are muscular and attenuate posteriorly. The fins extend to the posterior tip of the mantle. The anterior lobes are free.

The funnel is short and muscular. It is fused to the ventroposterior side of the head by a narrow muscular band extending forward anterior to the funnel locking-cartilage. The funnel locking-cartilage has an inverted T-shaped groove which is fused with the mantle locking-cartilage in the posterior portion of the longitudinal groove. The dorsal pad of the funnel organ has an inverted V-shape with only a slight trace of an anterior papilla. The lateral arms are very long and extend onto the funnel retractor muscles. The ventral pads are rather slender and extremely elongate. The anterior and posterior extent of the ventral and dorsal pads coincides. A large funnel valve is present.

The head is approximately the same diameter as the mantle. The eyes are large and occupy almost the entire lateral sides of the head. A large anterior sinus is present on each eyelid, and there is a small “window” in the skin above and below each eye. A nuchal crest bears 4 folds which are connected posteriorly. An oblique ridge, the “olfactory” organ, lies on the posterior extension of the second fold from the funnel. A distinct funnel groove is present. The foveola has 8 low ridges on its anterior wall. Only a single, small, side pocket can be found on each side of the foveola. The nuchal cartilage broadens at the anterior end and has a median ridge with a central groove.

The arms are short (30–40% of the M.L.) and in the order 2=3=4>1. Arms I–III all have well-developed aboral keels. An additional keel is present along the lateral side of each arm I. Large lateral keels are present on arms IV.

Trabeculate protective membranes are well developed on all arms. On arms I–III, the membranes on the ventral margins are broader than on the dorsal margins. These are most fully developed on arms III where they are wider than the greatest width of the aboral keel of the same arm. The long, slender, supporting trabeculae extend to the margin of the membrane. The trabeculate membranes of arms IV are equally developed on both margins.

The suckers of the arms are biserially arranged and total 43–48 on each of arms I–III and 56–58 on arms IV. The basal few suckers on each arm generally have 3–5 broad, truncate teeth on the upper margin of the chitinous ring and a smooth lower margin. Each broad tooth is the homologue of 2 pointed teeth on the more distal suckers. At rows 5 and 6 on the arms, the teeth have approximately 9–12 sharply pointed teeth on the distal margin that merge with 1–3 broad, generally truncate, teeth on each lateral margin; the proximal margin is smooth. The teeth are more or less of a uniform size, except for an occasional small tooth situated near a larger tooth, although more frequently these are fused, forming a single, somewhat lopsided tooth. The number of teeth is somewhat irregular; some of the large suckers of arms II may have small broadly spaced teeth on the proximal half of the sucker ring. This appears to be a variable feature. Suckers of the seventeenth and eighteenth rows each have 5–6 long pointed teeth on the distal half of their inner rings. The largest suckers of arms IV are roughly half the diameter of the largest suckers of arms II. The largest suckers of arms I and III are only slightly smaller than those of arms II.

The tentacles are short and muscular.. An aboral keel extends the full length of the tentacular stalk and onto the club where it is continuous with the dorsoaboral keel of the dactylus. The clubs are only slightly expanded and bear roughly 115–123 suckers. The suckers of the manus are arranged in 4 longitudinal rows except at the proximal end where the number of suckers rapidly diminishes to a few irregularly arranged suckers that extend onto the tentacular stalk. There are no carpal suckers although a single carpal knob was found near the base of the manus close to the dorsal border of both clubs in one specimen, but not in the other. The suckers in the 2 median rows on the manus are greatly enlarged, the largest being 2½ to 3 times the diameter of the marginal suckers. These suckers each bear a single enlarged tooth on the distal margin of the sucker ring. The remaining margin has low jagged edges which form teeth lacking a regular pattern or shape. The dentition becomes more regular on the smaller suckers. The marginal suckers bear about 30–35 teeth around the entire circumference of the chitinous ring. The teeth of the distal margin are slender, pointed, and roughly alternate between long and short sizes. The teeth on the proximal margin are all short and uniform. The dactylus has 4 longitudinal rows of suckers which are continuous with those of the manus. The suckers grade in size in a transverse series from the largest in the ventral row to the smallest in the dorsal row. The sucker dentition is the same as in the marginal suckers of the manus, although the number of teeth decreases as the size of the suckers diminishes near the tip of the dactylus. There is a small pad of about 7–8 smooth ringed suckers at the tip of the dactylus.

The buccal membrane has 7 lappets. The buccal connectives attach to the dorsal borders of arms I, II, IV, and to the ventral borders of arms III.

This species has a very distinctive photophore pattern. Two broad luminous strips extend almost the full length of the mantle on either side of the ventral midline. Each strip consists of 3 separate parts: a small anterior segment is situated at the free margin of the mantle; a short gap separates this from the second part which extends to approximately the level of the lateral angles of the fins; and this is barely separated from the third portion which continues to approximately the level of the conus of the pen. Near the anterior edge of the mantle are two small patches, one situated on either side of the ventral midline, but medial to the anterior portion of the long strips. Also near the anterior margin, but lateral to each of the long strips, is a medium-size photophore. There is a large photophore on the ventral surface of the head at the base of each arm IV, and another is located on midventral surface of each arm IV.

Many small photophores, generally invisible without dissection, are scattered over the mantle, funnel, head, and arms. These form almost a complete line along the anterodorsal margin of the mantle. They are scattered irregularly over the ventral surface of the mantle, but are absent from its dorsolateral surface. They are scattered along the dorsal midline from the anterior mantle margin to the fins. The inner surface of the funnel has a single photophore on each dorsolateral side at approximately the level of the emergence of the cephalic vein. There is a photophore at the funnel attachment of each of the 2 bridles and 2 small photophores are imbedded in the funnel valve. On the head, a few photophores are scattered lateral to the base of the funnel. I have found only a single photophore in the integument immediately in front of the foveola; however, since most of the tissue there has been torn away, it is quite likely that at least several others are present in intact specimens. A small distinct photophore is present at the medial base of each ventral arm very near the point where the arms unite. A line of irregularly shaped photophores extends along the lateral edge of each ventral arm at the base of the keel in the proximal half of the arm. There is also a series of small photophores along the surface of the axial nerve of each tentacle.

There can be no assurance that all photophores have been located, since they are extremely difficult to see. For example, Okada (1927) in a histological examination found photophores in the fins, but I have not been able to find them by gross dissection.

The larger specimen examined is a gravid female with greatly enlarged nidamental glands. The mature eggs measure just under 1 mm.

The animal is covered with numerous, small, reddish brown chromatophores. The dorsal surface is darker than the ventral surface, and the lateral sides of the animal have a distinct silvery appearance.

TYPE LOCALITY.—Off Misaki, Japan.

LOCATION OF TYPE.—In Tokyo Imperial University.

Eucleoteuthis is a monotypic genus of squid from the family Ommastrephidae; the only species is Eucleoteuthis luminosa, the striped flying squid or luminous flying squid.

oceanic, epi- to mesopelagic

Known from seamounts and knolls