Hoho carteta

Mallacoota carteta

DIAGNOSIS (of female phenotype CC).—Differing from M. marilla in presence of single middorsal posterior tooth on each of pleonites 1–2, with strong, rounded middorsal carina on pleonite 3; apex of posteroventral lobe on coxa 4 with slight extension; epimeron 3 with enlarged posteroventral tooth; rami of uropod 3 slightly broadened but equal in relative length to M. marilla; telson with lateral wing of apex enormously extended. Females up to 11.0 mm long; juvenile 3.0 mm also known and bearing typical teeth.

MALE OF PHENOTYPE CC.—Gnathopod 2 scarcely setose, palm very oblique, ill defined, bearing weak spinose humps and facial ridge locking dactyl, nodulate, dactyl long, weakly curved, apically simple; teeth of pleonites 1–2 very thick; lateral wings of telson not as highly elongate as in other phenotypes or in female of phenotype C.

MALE OF PHENOTYPE CS.—Gnathopod 2 highly setose medially as in PS of M. marilla; dactyl simple. Male is juvenile, 4.5 mm; adult unknown; possibly this phase transforms into adult CC.

HOLOTYPE.—WAM, male, 8.8 mm.

TYPE-LOCALITY.—Slack-Smith 2, Cheyne Beach, east of Albany, Western Australia, intertidal, weedy rocks, 6 December 1968.

DISTRIBUTION.—Warm-temperate Australia, intertidal and sublittoral.

Parelasmopus Stebbing

THE PROBLEM OF SPECIES IN THIS GENUS

The following names have been established for species in Parelasmopus: Gammarus suluensis Dana (see 1853); G. albidus Dana (see 1853); Parelasmopus setiger Chevreux (1901); P. resacus J. L. Barnard (1965). Stebbing (1888) identified and described a species as P. suluensis, which has been used as a model comparator ever since. Only the female of G. suluensis was described by Dana in 1853, but his weakly developed figures clearly show Stebbing’s material to be distinct in the presence of a pair of dorsal teeth on pereonite 7 and in the weakly serrate article 2 of pereopods 3–5. Dana showed G. suluensis to be lacking teeth on pereonite 7, but he distinguished them on the pleonites successfully; he also showed a heavily serrate article 2 of pereopods 3–5, which appears very real directly beside a similar species now believed to be in the same genus, G. albidus. Dana drew the latter with a smooth article 2 of pereopods 3–5, implying, at the least, that they were so poorly serrate that, with his enlarging lens, the serrations appeared minimal.

Chevreux (1901) differentiated his P. setiger from Stebbing’s (1888) view of P. suluensis in a number of characters, one of which seems today to be of importance: the strong anteroventral tooth on coxa 1 in P. setiger. In addition, the oblique palm of gnathopod 2 and the apparent absence of long setae on pereopods 3–5 seem to differentiate Stebbing’s material from P. setiger. (Stebbing’s specimen lacked articles 5–7 of the pereopods, so that the degree of setosity is not fully clear except on article 4). Whether the difference between 4 telsonic spines on each lobe in P. setiger and 2 spines in Stebbing’s material is valid is difficult to determine until similar instars can be compared. Chevreux also noted that Stebbing in P. setiger drew rounded lateral cephalic lobes that are truncate. Parelasmopus setiger also is characterized by long dorsal body setae, but I have specimens on hand, otherwise congruous to P. setiger, with thsese setae either absent or very sparse, though elongate. Other differences mentioned by Chevreux are difficult now to evaluate.

Walker (1904) had specimens that he believed mixed together characters of Stebbing’s P. suluensis and Chevreux’s P. setiger, and he started a trend to synoymizing P. suluensis and P. setiger, followed later by Stebbing, K. H. Barnard, Stephensen, and Pirlot among others with the result that by 1936 the two species definitely had been synonymized. But in 1938 Schellenberg rediscovered the fact that Dana also had described another Parelasmopus, G. albidus. Unfortunately, I believe he attributed the wrong material to that species, as did Stebbing (1888), who apparently also attributed wrong material to P. suluensis

It now appears that major specific characters in the genus include at least the following: (1) whether dorsal teeth are present or absent on pereonite 7 in adults; (2) whether the palm of male gnathpod 2 is nearly transverse or definitely and strongly oblique; (3) whether article 2 of pereopods 3–5 is grossly or weakly serrate; (4) whether coxa 1 (and 2, 3, and 4) has an extended, sharp anteroventral tooth; and (5) whether pereopods 3–5 have extremely long setae or not. If variations in these characters can be demonstrated to represent only demes or morphs, one must then synonymize all of these species.

Character 5 may be of little value, as I have found specimens of P. setiger without dorsal setae of any extent, and thus by extension I consider the possibility that setose and nonsetose forms of pereopods may occur. Since 1904, however, characters 1–4 have not been consistently handled in identifying specimens of Parelasmopus, although an occasional reference to what has since become a single species, P. suluensis, has sufficient information to suggest a proper identification. Until the tropical Indo-Pacific specimens of Parelasmopus can be studied thoroughly, it seems wise to separate the various species originally described and any other identification not fitting the original material of each name. This is presented in the key to Ifalukia, Mallacoota, and Parelasmopus, wherein Parelasmopus resacus is removed to a new genus, Ifalukia.

Among the various references to P. suluensis and P. albidus, one may find some clues to a different identification than that proposed by the identifier:

Walker’s (1904) P. suluensis appears to be P. setiger.

Walker’s (1905) P. suluensis also may be P. setiger.

Chilton’s (1922) P. suluensis is definitely P. setiger in the dorsally nonsetose phase.

Stephensen’s (1931) P. suluensis may be P. albidus.

K. H. Barnard’s (1935) P. suluensis is generally similar to Stebbing’s (1888) version of P. suluensis except that pereopods 3–5 have long setae. It is thus the most disturbing material so far reported, and it suggests that the systematic problem in Parelasmopus is compounded by the presence of many undescribed species or undescribed phenotypes of a common stem.

Schellenberg’s (1938) P. albidus may be Dana’s P. suluensis.

Schellenberg’s (1938) P. suluensis is enigmatic.

Identifications of P. suluensis by Spandl (1924), Pillai (1957), and Nayar (1967) all suggest the presence of additional species or morphs in the genus.

Identifications of P. suluensis in the following papers did not include any significant morphological notes: Chevreux (1908), Walker (1909), Stebbing (1922), Pirlot (1936), K. H. Barnard (1940), Ruffo (1959).

I have reexamined my (1965) identification of P. albidus from Micronesia and find that the one juvenile specimen fits the key (herein) to P. albidus, but it does not fit Schellenberg’s (1938) material of P. albidus because the serrations on article 2 of pereopod 3 are of the weak and not the strong alternative. The specimen has a weakly developed gnathopod 2, no teeth on pereonite 7, a sharp anteroventral cusp on only coxae 1–2. Articles 5–7 of pereopods 3–5 are missing, but article 4 has a few of the medium-long spine setae (about 60 percent as long as article 4) that are not considered to be the long kind of flexible setae seen in P. setiger. The peduncle of antenna 2 fails strongly in reaching the end of the peduncle of antenna 1. Except for antenna 2, this specimen thus fits the original description of P. albidus more strongly than anything since reported in the literature.

A key to the species of Ifalukia, Mallacoota, and Parelasmopus precedes the description of Ifalukia.