Dactylokepon semipennatus Bourdon, 1983

An, Jianmei, Yu, Haiyan & Williams, Jason D., 2007, Four new records and a new species of Dactylokepon Stebbing, 1910 (Epicaridea: Bopyridae: Ioninae) from Chinese waters, Journal of Natural History 41 (33 - 36), pp. 2063-2079 : 2066-2068

Dactylokepon semipennatus Bourdon, 1983

( Figure 2 )

Dactylokepon semipennatus Bourdon 1983, p 857 –859, Figure 8 [Type locality: Seleman Bay ; infesting Glabropilumnus latimanus Gordon ].

Material examined

Infesting Portunus haanii (Stimpson) . Nansha, Stn 2, 11 ° 309N, 112 ° 52.59E, 70 m, 4 April 1990, dredge; 1♀, CIEP040401 1 „, CIEP040402 . Infesting Lupocyclus rotundatus Adams and White. BeiBu Bay, Stn 6236, 20 ° 509N, 108 ° 009E, 47.5 m, 18 April 1960, Sun coll., dredge; 1♀ (damaged), CIEP623601 .

Redescription of reference female

Length 12.17 mm (excluding uropod), maximal width 8.62 mm, head length 2.46 mm, head width 3.16 mm, frontal lamina length 0.66 mm. Body distorted, 35 ° with right side convex (dextrally deflexed) ( Figure 2A ).

Head bilobate, with prominent frontal lamina, extending beyond both sides of head. Eyes absent ( Figure 2A ). Antenna of five articles, antennule of three articles ( Figure 2B ). Maxilliped ( Figure 2C ) nearly triangular, anterior article broadly rounded, with prominent non-articulating, curved and non-setose palp; plectron short, roundly pointed. Barbula ( Figure 2D ) with two digitate projections on each side, outer pairs larger than inner pairs.

Pereon broadest across third pereomere. No middorsal projections. Brood pouch almost covered by oostegites. Oostegite 1 ( Figure 2E, F ) smoothly rounded anteriorly, produced into sharp extended point posterolaterally; posterior edge with sharp projections; internal ridge simply digitate. Pereopods similar structure except increasing in length posteriorly. Pleon of six pleomeres; first five pleomeres with biramous pleopods and lateral plates, all digitate, posterior sides of rami more deeply digitate than anterior sides. First three lateral plates of left side extending anteriorly, due to body curved to the left. Uniramous uropods similar in size and structure to lateral plates of fifth pleomere.

Redescription of reference male

Length 3.55 mm, maximal width across pereomere 3, 1.13 mm, head length 0.51 mm, pleonal length 1.1 mm. Body gradually tapered posteriorly, all segments distinct ( Figure 2G, H ).

Head oval, broader than long. Conspicuous dark eyes near posterior edge. Head and first pereomere distinctly separated ( Figure 2G ). Antenna of four articles, antennule of three articles, distally setose ( Figure 2I ).

Pereomeres deeply separated. Prominent midventral tubercle on each pereomere ( Figure 2H ). Pereopods all about same size, but dactyli of first two pairs larger than others ( Figure 2J ).

Pleon of six segments without midventral tubercles, first five pleomeres with tuberculiform pleopods ( Figure 2H ), final pleomere cuneate, with straight posterior margin, uropods lacking.

Remarks

This is only the second record of this species, extending its range from Maluku Islands (5 Moluccan Islands), Indonesia to Nansha and Beibu Gulf in China. In addition, two portunid hosts are first recorded as hosts for D. semipennatus , and for any bopyrid isopods; previously D. semipennatus has been found on xanthid hosts. The present material, especially the female, matches the type specimens ( Bourdon 1983) very well. However, the inner projections of the barbula are slightly digitate, unlike the smooth projections seen in Bourdon’s specimens, and the palp of the maxilliped is slightly more curved than in the holotype. The male reported by Bourdon (1983) differs from the present one in having a straight posterior margin to the head, and bifurcate uropods. The female found on Lupocyclus rotundatus Adams and White is damaged and lacks a head, but can be identified based on the morphology of the first oostegite, the pereomeres, and pleomeres. Two species in the genus Dactylokepon were previously known to infest portunids. Stebbing (1910) briefly described D. catoptri , infesting Catoptrus nitidus A. Milne-Edwards from Amirante, but the shapes of its maxilliped palp and barbula are very different from that of the present females. Shiino (1942) described D. palaoensis , infesting Thalamita spp. at Palao, but, as Bourdon (1983) discussed, D. palaoensis and D. semipennatus can be differentiated by the greater digitation of the pleopods and the fact that the uropods are of same length as the lateral plates of the fifth pleomere in the latter species.

Distribution and hosts

Seleman Bay, Maluku Islands, Indonesia, on Glabropilumnus latimanus Gordon ; Nansha and BeiBu Bay, China, on Portunus haanii (Stimpson) and Lupocyclus rotundatus Adams and White.

Figures

Figure 2. Dactylokepon semipennatus Bourdon, 1983. (A–F) Reference female: (A) dorsal view; (B) left antennae; (C) right maxilliped, external view; (D) barbula (left side); (E) left oostegite 1, external view; (F) left oostegite 1, internal view. (G–J) Reference male: (G) dorsal view; (H) ventral view; (I) left antennae; (J) left pereopod 1. Scale bar: 1 mm (A); 0.13 mm (B, I, J); 0.47 mm (C, D); 0.70 mm (E, F); 0.30 mm (G, H).