Ceradocus (Denticeradocus) serratus (Spence Bate 1862)

Ceradocus serratus (Bate)

Megamoera serrata Bate, 1862:226, pl. 39: fig. 5.

Moera spinosa Haswell 1880b: 268, pl. 10: fig. 5.—Haswell 1885:105, figs. 5–12 [part].

Ceradocus (Denticeradocus) serrata.—Sheard 1939:285–288, figs. 4, 5a-m [with references].

This material from Port Phillip Bay apparently represents the form described by Sheard (1939) and found in Western Port, a short distance from Port Phillip.

DIAGNOSIS (of bay form).—In alcohol, eyes lacking black pigment; slit of lateral cephalic lobe deep, edges fully appressed, anteroventral corner below slit with small sharp tooth; antenna 1 with 3 ventral spines on article 1; simple gland cone of antenna 2 reaching 60 percent along article 3 of peduncle; antenna 2 reaching only 67 percent along article 2 of peduncle on antenna 1; article 3 of mandibular palp as long as article 1; lateral ridge on coxa 2 placed somewhat anteriad; article 4 of gnathopods 1–2 with sharp posteroventral tooth; female gnathopod 2 with simple, oblique palm defined by weak cusp; male gnathopod 2 with variable gnathopod 2, left occasionally small and like female, or enlarged and bearing large falconiform process near base of dactyl, process defined by sinus, remainder of palm with straight oblique margin and not defined, right gnathopod 2 either larger or smaller than left, bearing 1 weak notch and rudimentary falconiform process or process slightly enlarged and joined by second subquadrate process also defined by sinus; posteroventral corner of article 2 on pereopods 3–5 with sharp process; telson of adolescent female with strongly attenuate apices each bearing 2 spines, 1 spine nearly as long as telson, plus 1 distal feathered seta and 2 basolateral feathered setae, adolescent male telson with apices much less attenuate and apical spines very short, adults with 4–5 spines on each lobe; pleonites 1–3 dorsally serrate evenly; in adolescents pleonite 4 dorsally bearing 6 teeth subequal in length to each other, occasionally lateralmost tooth slightly elongate, middle of dorsal edge with teeth evenly spaced, pleonite 5 always with middle tooth, with 6 small teeth of even size and even distribution or middle tooth enlarged. Adults with 9 dorsal teeth on pleonite 4 arranged coronately, middle tooth sometimes enlarged, pleonite 5 with 1 large tooth in middle and 2 laterals each side; pleonal epimera 1–2 with small, sharp definitive posteroventral tooth, small notch on ventral margin below main tooth and 2 small-to-medium teeth above definitive tooth, both epimera with lateral ridge, epimeron 2 with or without weak waves above main tooth, epimeron 3 grossly serrate on posterior margin and with 2–3 gross serrations on posterior part of ventral margin.

RELATIONSHIP.—The even distribution of teeth on pleonites 4–5, the presence of a strong sharp tooth on epimeron 2, the shortened gland cone, the shortened peduncle of antenna 2, and the long article 3 of the mandibular palp distinguish this species from C. dooliba. That species might be considered in the category of a cryptic or sibling partner of C. serratus and may heretofore have been identified as juveniles of C. serratus. Sexual characters of males and females appear at least as early as a body length of 8.2 mm, but no juveniles smaller than that size are in the collections. Males of C. dooliba do not develop penial processes until a body length of about 11.0 mm is reached; no specimens of C. dooliba smaller than about 9.0 mm are available. Specimens of both species with body lengths of 9–11 mm have been compared to determine whether C. dooliba simply represents a transformation of C. serratus to adult stages; both species may be distinguished in those body sizes, but there is only negative evidence that one does not transform into the other. No intergrades have been found in mandibular palp, gland cone, epimeron 2, and pleonites 4–5, but the female of C. serratus in contrast to the male has a telson characteristic of C. dooliba. Uropod 1 of both species has a basolateral spine and a large distolateral spine on the peduncle. The heads are nearly identical, the small tooth of C. dooliba being slightly more blunt. Gnathopod 1 and pereopods 1–2 are similar in both species.

MATERIAL.—Port Phillip 16 (5), 48 (1), 56 (1), 88 (5).

DISTRIBUTION.—Southeastern Australia, littoral and sublittoral.

Ceradocus species

MATERIAL.—Australian Museum, Sydney, Catalog P 15921, Shiprock, Burraneer Bay, Port Hacking, collected by A. Healy, 19 November 1967 (male, 13.3 mm).

This specimen has pleonal epimera like C. rubromaculatus, an oblique palm on gnathopod 2, telsonic lobes with 3 and 4 spines each, and a simple gland cone. The oblique palm on gnathopod 2 removes this specimen from C. sellickensis, but in other respects it bears characters of that species. The simple gland cone and more than 2 spines on each telsonic lobe remove the specimen from C. rubromaculatus.

Maera Leach

POSSIBLE REVIVAL OF Linguimaera PIRLOT AS A SUBGENUS OF Maera LEACH

Linguimaera Pirlot (1936), established to represent L. othonides (Walker), was characterized solely by the enlarged sagittal lobe of the upper lip. Schellenberg (1938:49) implied the synonymy of Linguimaera and Maera by his statement “die Keinerlei systematische Bedeutung besitzt.”

There is one other character of Linguimaera that seems to have some importance as the mark of a species flock, the notch on the cephalic cheek, which does not occur in the type-species of Maera, M. grossimana (Montagu). The presence of the cheek notch in combination with carinae on pleonite 4 is utilized herein to distinguish the new genus Mallacoota from Maera; however, in Melita, another genus of Gammaridae, the presence or absence of a cheek notch has been accorded only specific value. There may be some purpose in studying the members of Melita that have lost the cheek notch in order to determine whether they have other characters in common, which might cause them to be assembled as a subgenus. The problem of the cheek notch is prevalent in the genera Eriopisa, Eriopisella, and Nuuanu (see J. L. Barnard, 1970a). The genus Ceradocus is also characterized by the presence of a cheek notch, and some of the species of Maera bearing the cheek notch have a strong external resemblance to members of Ceradocus. This is especially true of Maera mastersi because of the many posterior teeth on epimeron 3 and the pair of teeth on epimeron 2. Maera mastersi, however, differs from the five known species of Ceradocus from Australia in the absence of a cusp on article 1 of the mandibular palp, the elongate article 3 of the mandibular palp, the absence of dorsal serrations on the pleonites, and the characters heretofore used mainly to distinguish Ceradocus from Maera: the absence of strong medial setae on the inner plates of maxillae 1–2. The species of Ceradocus examined by me also have a large inner tooth on article 2 of antenna 1 not occurring in M. mastersi.

Whether the Australian M. mastersi signals any significant relationship between the Linguimaera section of Maera and the genus Ceradocus is a question to ponder. Unfortunately, the only species of the section fairly well described is M. mastersi, and it is not the type of Linguimaera. Perhaps the Linguimaera section and Ceradocus are merely convergent in gnathopods, epimera, and cephalic notch, but there is also a general resemblance in the telson between Maera in general and Ceradocus, although the species of Ceradocus generally have the telson in the extreme condition of extended apices and elongate spines. A second example of character convergence—and one complicating the free use as a unique generic character of the cuspidate article 1 on the mandibular palp of Ceradocus—is the New Zealand species Maera tepuni J. L. Barnard (in press). That species is a typical Maera in the absence of a cephalic notch (though a weak indication of one is present), the poorly setose maxillae, and, most importantly, the completely ordinary telson with broad lobes and weak spines, similar to some members of Maera and Elasmopus. But Maera tepuni has a cuspidate article 1 on the mandibular palp like the genus Ceradocus.

The final complication reducing the value of the cheek notch is the fact that the type-species, Ceradocus orchestiipes Costa, from the North Atlantic Ocean, lacks the cheek notch. All other species of Ceradocus from the North Atlantic Ocean or from the high circumboreal waters apparently also lack the cheek notch. Kunkel’s two species from Bermuda, C. colei and C. parkeri, are unknown for this character. Thus, C. orchestiipes Costa, C. torelli (Goës), C. baffini Stephensen, and C. sheardi Shoemaker lack the notch. All of the Pacific Ocean and Indian Ocean species, including those from the low North Pacific in California and Hawaii, bear the cheek notch. Hence, the presence or absence of a cheek notch can be shown to occur in Maera, Ceradocus, and Melita. It therefore, appears to have no full generic value in this context, though it may signify relationships among flocks of species within those genera and thus have significance at subgeneric level. So far, it has geographic significance in Ceradocus, but not in Melita and Maera.

The many characteristically deep serrations on epimeron 3 and the 2 each on epimera 1–2 of M. mastersi also may have some significance in finding relationships among various species in the Linguimaera section of Maera. Unfortunately, this character is not well explored among the various species presumed to belong to Linguimaera, but it occurs in the material identified as M. othonides by Pirlot (1936), M. othonopsis Schellenberg (1938), and in the material identified as M. hamigera by J. L. Barnard (1965). Serraations, however, both below and above the main posteroventral tooth on epimeron 3, also occur in various ordinary species of Maera such as M. othonis (Milne Edwards) from the North Atlantic Ocean, M. serrata Schellenberg from the tropical Pacific, and M. tepuni J. L. Barnard (in press) from New Zealand. Serrations or extra teeth on epimera 2–3, however, appear to be confined to some of the species with a cephalic notch herein placed in Linguimaera.

The revival of Linguimaera cannot be made legitimately until the question of Pirlot’s identification of M. othonides Walker is clarified. Since Pirlot cited Walker’s species as the type of Linguimaera and since there is some question whether or not Pirlot had Walker’s species in hand, there remains a possibility that the validity of Linguimaera would have to be considered by the International Committee on Zoological Nomenclature under Article 70a of the Code.

Regardless of name, the concept that the taxa listed below represent a species flock with interconnected ancestry seems presently worth investigation. Some of the apparent taxa in the group are poorly described and may require establishment of new names. Except in the limited statement below, it is not worthwhile now discussing why the various identifications appear as distinct species.

The list of species and presumed species in the Linguimaera section of Maera are as follows:

?Maera othonides Walker (1904)

Linguimaera othonides of Pirlot (1936)

?Maera othonides of Chilton (1921b)

?Maera othonides of K. H. Barnard (1935)

Maera master si (Haswell)

?Maera hamigera (Haswell)

Maera hamigera of J. L. Barnard (1965)

?Maera boeckii (Haswell)

?Elasmopus boeckii of K. H. Barnard (1916)

?Elasmopus laevis K. H. Barnard (1916)

Maera bruzelii Stebbing (1888)

Maera species A of J. L. Barnard (1970a)

Maera othonopsis Schellenberg (1938)

Note on identification of M. othonides Walker (1904). The original description and figures were very slim. One is required to examine illustrations of M. othonis (Milne Edwards) from Europe to make assumptions on characters Walker did not describe. Walker wrote that article 3 of the mandibular palp was “considerably” shorter than article 2. Pirlot (1936) noted that article 3 is “beaucoup plus court” than the second. Nayar (1959) has identified as M. othonides a very unique species in the Gammaridae, because it combines the palp article 3 shortness of Ceradocus (but the absence or only faint indictation of a cusp on article 1) with the maxillae of the genus Maera and a telson apparently either badly squashed or with some medial fusion of the lobes. Gnathopod 2 of Nayar’s specimens is grossly enlarged, whereas in Pirlot’s material it is small, thin, and rectangular, and one infers the small gnathopod from Walker’s original description. Nayar’s specimens also have dorsal pleonal denticulation typical of Ceradocus. His specimens presumably should be placed in a new genus, but whether his or those of Pirlot belong with Walker’s species is highly questionable.