Linguimaera Pirlot, 1936

Krapp-Schickel, T., 2003, Linguimaera Pirlot, 1936 (Crustacea, Amphipoda, Melitidae), a valid genus, Memoirs of Museum Victoria 60 (2), pp. 257-283 : 258-260

Linguimaera Pirlot, 1936

Figure 1

Linguimaera Pirlot, 1936: 309 .— Schellenberg, 1938: 49 (synonymy of Linguimaera with Maera )

Type species. Linguimaera pirloti sp. nov. (= Maera othonides Walker sensu Pirlot, 1936 ), not Maera othonides Walker, 1904 ; herein selected, see ICZN (4th edition, 1999) Article 70.3.1

Diagnosis. Body smooth. Eyes reniform, more than twice as long as wide. Upper lip thickened, in side-view linguiform, lengthened, reaching between peduncles of antenna 2 ( Fig. 1 ); mandibular palp article 1 rounded or subquadrate, distally not produced; article 3 considerably shorter than article 2, maxilla 1 inner plate with 3 robust setae, maxilla 2 not marginally setose. Antenna 1 longer than antenna 2; antenna 1 accessory flagellum of 2–6 articles; antenna 2 peduncle article 2 gland cone not longer than article 3; Ceradocus -like cephalic cheek having notch or slit. Coxa 1 anteriorly lengthened, pointed or rounded, posterodistal corner notched. Gnathopod 1 carpus Ceradocus -like swollen, with distoinferior margin usually lengthened to short, acute tooth, often hardly visible under dense robust setae; gnathopod 2 sexually dimorphic and asymmetrical in both sexes, palm ornate and excavate. Pereopod 3 equal to or longer than pereopod 4, merus often somewhat swollen; pereopods 5–7 slender, basis clearly longer than wide, often rectolinear with right-angled posterodistal corner, weakly to strongly serrated posteriorly; dactyli simple, with stiff robust seta on inner side functioning like a pincer. Pleon dorsally smooth. Epimeral plates 1, 2 posterodistal corner upwards curved, acute, followed by shallow sinus defined by another acute tooth; epimeral plate 3 posterior margin densely serrate, up to 9–11 teeth; uropod 3 rami much longer than peduncle, richly spinose, robust setae always much shorter than length of rami; telson deeply cleft, lobes characteristically asymmetrically incised, the outer end being longer; robust setae clearly shorter than telson length.

Included species. Linguimaera bogombogo sp. nov., L. caesaris sp. nov., L. garitima sp. nov., L. kellissa sp. nov., L. leo sp. nov., L. mannarensis Sivaprakasam, 1968 , L. pirloti sp. nov., L. tias sp. nov.

Discussion. Lowry et al. (2001) redescribed Megamoera mastersii Haswell, 1879 from type material and figured round, not sexually dimorphic, eyes and symmetrical not sexually dimorphic gnathopods. They also redescribed Moera hamigera Haswell, 1879 on the basis of abundant recent collections. The latter is obviously a common species on Australian coasts which nevertheless totally seems to have escaped collecting in the last 130 years. It has different second epimeral plates, third uropods and telsonic lobes. Lowry et al. (2001) also redescribed Megamoera boeckii Haswell, 1879 with an emarginate telson shorter than broad. All these species do not seem to be closely related to the species flock presented here.

The genus Anamaera Thomas and Barnard, 1985 (from Florida, Thomas and Barnard, 1985) appears to be similar to Linguimaera also having asymmetrical gnathopod 2 and the same epimeral shape. But the mandibular palp article 3 is not shorter than article 2 and the eyes are rounded. Maera williamsi Bynum and Fox, 1977 was given erroneously as a synonym of Anamaera hixoni Thomas and Barnard, 1985 by Krapp-Schickel and Jarrett (2000) but has since been recognised as distinct. Another species remains to be described.

Ceradomaera Ledoyer, 1973 also has asymmetrical second gnathopods and differs mainly in the emarginate telson and dorsal teeth.

Serrations on epimeral plate 3, both below and above the posteroventral tooth, also occur in other species of Maera sensu lato (e.g. Othomaera othonis (Milne-Edwards, 1830) , Quadrimaera serrata ( Schellenberg, 1938) , Maera tepuni Barnard, 1972 ), but extra teeth defining an excavation on epimeral plate 1 and (more clearly visible in) epimeral plate 2, appear to be confined in the Indo-Pacific to Linguimaera , and in the Atlantic to Anamaera and the Maera williamsi -clade.

Barnard (1972a) cited also Maera othonopsis Schellenberg, 1938 in connection with the present species flock. It was described with few figures on the basis of only two incomplete ovigerous females from the Gilbert Is (Tropical West-Pacific) as having subequal mandibular palp articles 2 and 3, quite different third uropods and telson (cf. Quadrimaera Ruffo and Krapp-Schickel, 2000 or Mallacoota Barnard, 1972 ), and was never found again. It certainly does not belong to Linguimaera .

The Indo-Pacific genus Linguimaera is well differentiated from other genera of this region ( Quadrimaera , Ceradocus Costa, 1853, Elasmopus Costa, 1853, Maeracoota Myers, 1997 , Mallacoota ) by asymmetrical second gnathopods in both sexes, a sinus on the posterodistal corner of the first and second epimeral plates and a serrate posterior margin on the third epimeral plate. It shares the asymmetry of the gnathopods with the Atlantic Anamaera and the Indopacific Zygomaera Krapp-Schickel, 2000 , but differs mainly by characters of the mandible (palp articles 2 and 3 subequal) and telson (in Anamaera lobes cuspidate, in Zygomaera lobes partly coalesced). The Maera sensu lato flock of Barnard and Barnard (1983), containing 59 species, is now mostly unravelled, but there are still a dozen species remaining in Maera sensu lato, thereby stressing that they do not belong to the well-defined Maera sensu stricto.

Figures

Figure 1: Linguimaera sp. male (Adelaide, South Australia) SEM pictures. Above: head with thickened upper lip laterally; mandible with palp, maxillae; left half of upper lip ventrally. Second line: head with antennae, upper lip, mandible with palp, maxillae and maxilliped ventrolaterally. Below: head with first coxae and mouthparts from lateral and ventral; gnathopod 2 male.