Allokepon longicauda, Duan, Jiangyan, An, Jianmei & Yu, Haiyan, 2008

Duan, Jiangyan, An, Jianmei & Yu, Haiyan, 2008, A new species and two new record species of genus Allokepon Markham, 1982 (Isopoda: Epicaridea: Bopyridae) from China, Zootaxa 1682, pp. 62-68 : 66-68

Allokepon longicauda n. sp.

( Fig. 3 )

Material examined. Infesting Portunus pulchricristatus . Holotype: Beibu Gulf, stn. 6263, 19° 0 0ˏ N, 107° 0 0ˏ E, 59m. 19 October 1960, Guangzong Wu, coll., CIEP 626301, Ψ. Allotype: Beibu Gulf, stn. 6263, 19° 0 0ˏ N, 107° 0 0ˏ E, 59m. 19 October 1960, Guangzong Wu, coll., CIEP 626302, ɗ.

Diagnosis. Holotype with an asymmetrical body, short frontal lamina, almost smooth margins of lateral plates of pleomeres and the long slender uropods. Allotype with a semicircular head, antennae without setae, all pereomeres and pleomere 1 with prominent midventral tubercles, and sixth pleomere produced into two rounded symmetrically extending posterior lobes.

Description of holotype (CIEP626301). Body (excluding uropods) 4.46 mm long, maximal width across pereomere 3, 3.06 mm; head length 0.98 mm, width 0.94 mm; pereon length 2.64 mm, pleon length 0.84 mm, uropods length 1.93 mm, sinistral distortion 38°. All body regions and segments distinct. No pigmentation ( Fig. 3 A, B).

Head oblong, with narrow frontal lamina. Eyes absent. Antenna obscure. Maxilliped with large, falcate, curved, non-articled, setose palp and blunt plectron ( Fig. 3 C). Barbula with two falcate lateral projections on each side, and a pair of tubercles on middle region ( Fig. 3 D).

Pereon broadest across pereomere 3, gradually tapering on each side posteriorly. Coxal plates absent. Last two pereomeres with prominent middorsal projections. Dorsolateral bosses on first four pereomeres, tergal projections rudimentary. ( Fig. 3 A). Oostegites completely enclosing highly vaulted brood pouch ( Fig. 3 B). First oostegite ( Fig. 3 E, F) smoothly rounded anteriorly, with almost unornamented internal ridge, round posterolateral point. First segment of oostegite 1 larger than second one. Pereopods similar in morphology, propodi, carpi and meri setose ( Fig. 3 G).

Pleon of six pleomeres, first five bearing biramous pleopods and lateral plates, all slender and slightly serrate. Endopodite much shorter than its exopodite and lateral plates ( Fig. 3 B). Last pleomere with very long uniramous uropods similar to pleopods and lateral plates.

Allotype (CIEP626302). Length 1.68 mm, maximal width across pereon 5, 0.38 mm, head length 0.11 mm, head width 0.16 mm, pereon length 0.99 mm, pleon length 0.53 mm. All body segments distinct, no pigment ( Fig. 3 H, I).

Head semicircular, small eyes in posterolateral regions ( Fig. 3 H). Antennae of 3 and 5 articles respectively, without setae. Pereomeres 3–6 almost equally wide, round margins. All pereomeres with prominent midventral tubercles ( Fig. 3 I). All pereopods of same size and structure.

Pleon of six pleomeres, first five with tuberculiform pleopods, pleomere 1 with midventral tubercle ( Fig. 3 I), sixth pleomere produced into two rounded symmetrically extending posterior lobes ( Fig. 3 I).

Etymology. The specific name longicauda refers to the long uropods of the holotype female.

Remarks. A. longicauda n. sp. is placed in the genus Allokepon on the basis of the following characters: females with well-developed endopodites, prominent middorsal projections only on pereomeres and suboval oostegite 1; males with midventral tubercles on all seven pereomeres. These characters distinguish Allokepon from Leidya , Megacepon , and Cardiocepon . The females of the new species have particularly long uropods, which characterizes genus Leidya . The shape of oostegite 1 of A. longicauda excludes the species from genus Leidya . The new species differs from species of genus Megacepon in having middoral projections only on the pereomeres and absence of middorsal projections on the first pleomere of the female. The species of the genus Cardiocepon possesses peculiarly shaped, ventrally directed, pleopodal endopodites, and an extreme elongated oostegite 1.

The new species, A. longicauda , is distinguished from the other four species recorded in Chinese waters by the long slender uropods of females. Allokepon longicauda appears to be most closely related to A. tiariniae ( Shiino, 1937) , which also has fairly long uropods. The new species differs, however, from A. tiariniae in its asymmetrical body, short frontal lamina, and almost smooth margins of lateral plates and pleomeres. Furthermore, the sixth pleomere of the allotype has two rounded symmetrically extending posterior lobes, and not sharp lobes as in A. tiariniae ( Shiino, 1937) .

Distribution and hosts. Beibu Gulf; on Portunus pulchricristatus .

Figures

FIGURE 3. Allokepon longicauda n. sp. Female (A – F). A, dorsal view. B, ventral view. C, right maxilliped, external view. D, Barbula, right side. E, right oostegite 1, external view. F, right oostegite 1, internal view. G, left pereopod 7. Male (H, I). H, dorsal view. I, ventral view. Scale 1.00 mm for A, B; 0.42 mm for C, D, E, F; 0.25 mm for G, H, I.