Parasymmetrione tuberculineata, An & Markham & Yu, 2010

An, Jianmei, Markham, John C. & Yu, Haiyan, 2010, Description of two new species and a new genus of bopyrid isopod parasites (Bopyridae: Pseudioninae) of hermit crabs from China, Journal of Natural History 44 (33 - 34), pp. 2065-2073 : 2070-2072

Parasymmetrione tuberculineata sp.nov.

( Figure 2 )

Material examined

Infesting Clibanarius corallinus (H. Milne-Edwards, 1848) . Det of host, Yongliang Wang. Holotype: Xisha , Dong Island, 16°50′ N, 112°20′ E, 28 May 1980, one female, CIEA800503 , Allotype: Xisha , Dong Island, 16°50′ N, 112°20′ E, 28 May 1980, one male, CIEA800504 . Paratypes: Xisha , Dong Island, 16°50′ N, 112°20′ E, 28 May 1980, one female, CIEA800505 , one male, CIEA800506 .

Description of holotype female (CIEA800503) ( Figure 2A–J )

Length 4.1 mm, maximal width 9.2 mm, head length 1.1 mm. Body axis distorted 118°, dextral. Body outline broadly triangular because of extended brood pouch. All body regions and segments distinct. No pigmentation ( Figure 2A,B ).

Head subcircular, with small frontal lamina of two separate sinuous lobes. Eyes absent. Antennae of four and six articles respectively ( Figure 2C ), both setose distally. Barbula ( Figure 2D ) with two lateral falcate projections on each side and one small triangular projection. Maxilliped ( Figure 2E ) almost semicircular, its anteromedial corner indented in place of palp ( Figure 2F ); its posterior article only half as large as anterior one and produced into tiny sharp plectron.

Pereomeres 3–5 fused dorsomedially, others distinct. Pereomeres 1–4 bearing coxal plates on both sides and prominent tergal projections on left sides; pereomeres 1 and 2 with dorsolateral bosses on right sides. Oostegites almost completely enclosing brood pouch; first oostegite ( Figure 2G,H ) with conspicuous outer groove and internal ridge bearing seven to eight irregular lobes along almost whole length; narrow posterior point sharp and curved. Pereopods of about same size, all their articles distinct; tuberculate ridge on basis of pereopod 2 ( Figure 2I ).

Pleon of six pleomeres, first four produced into lobed smooth-edged lateral plates on both sides, those on left side much smaller and narrower. Pleomere 5 bearing pair of spherical lateral plates. Final pleomere with fused spherical lateral plates. Pleopods 1–4 biramous with line of tubercles parallel to each edge ( Figure 2J ). Fifth pleopods and uropods uniramous and sparsely tuberculate.

Description of allotype male (CIEA800504) ( Figure 2K–N )

Length 3.2 mm, head length 0.5 mm, head width 0.6 mm, pereonal length 1.8 mm. All body regions and segments distinct. No pigmentation aside from dark eyespots ( Figure 2K,L ).

Head subelliptical, bearing small dark eyes near posterolateral edges. Antennae of three and seven articles respectively, each with many setae distally; second antenna much longer than first, visible in dorsal view, its fifth and sixth articles setose ( Figure 2M ).

Pereomeres distinct, separated by deep anterolateral notches ( Figure 2K ). Pereopods of first pair largest and only ones with large dactyli; pereopods 2–4 progressively smaller, pereopods 4–7 of almost same size and shape ( Figure 2N ). Meri and carpi of pereopods 1–3 fused, others separated ( Figure 2L ).

Pleon of six pleomeres, narrowing smoothly posteriorly, lateral margins of all pleomeres reflexed laterally and posteriorly ( Figure 2K,L ). Five pairs of prominent uniramous flap-like pleopods progressively smaller posteriorly. Pleomere 6 produced into long flat extended uniramous uropods dorsally articulating.

Remarks on immature female (CIEA800505) ( Figure 2O )

Body distortion less than in holotype, brood pouch not extending far out from body outline, pereomeres 3–5 incompletely separated middorsally, pleonal lateral plates and pleopods much less tuberculate.

Etymology

Combined form tuberculineata from Latin stems tuberculata (“tuberculate”) and lineata (“lined”) meaning “line of tubercles” used as Latin first declension adjective in reference to rows of tubercles near edges of pleopods of holotype female.

Discussion

To date, 10 genera of branchially infesting pseudionine bopyrid parasites of paguroids, the hermit crabs, are known worldwide ( Markham 2003). Females of species in two of these genera, Asymmetrione Codreanu et al., 1965 and Bopyrophryxus Codreanu, 1965 , are extremely distorted, and their males have extended pleons bearing six pairs of prominent flap-like uniramous pleopods. Parasymmetrione tuberculineata exhibits all of these characters, but it differs enough from each of the other two genera to require a genus of its own. Females of Asymmetrione , discussed above, have distinctive pereopodal propodal sockets, and the males of that genus have at least the first two pereopods much larger than the others ( Pardo et al. 2009). In the single known species of Bopyrophryxus , B. branchiabdominalis Codreanu, 1965 , as re-described by Bourdon and Boyko (2005), the female’s brood pouch is typically extended like that of Parasymmetrione tuberculineata , and its frontal lamina is similarly divided, but its antennae, pereopods and pleopods are proportionately much larger, the first oostegite has a very different shape, and no pleopods are biramous; the male of B. branchiabdominalis uniquely has greatly enlarged and extended first pereopods, its short head is nearly as broad as the first pereomeres, and its uropods are much reduced. These three genera are probably closely related, but there is adequate justification for keeping them separate.

This is the first record of bopyrid infestation of either Clibanarius corallinus or Dardanus hessii . These diogenid species have similar extensive known ranges, both being recorded from China, the Philippines, Indonesia and Australia; C. corallinus is also reported from Japan and numerous western Pacific islands, while D. hessi is also known from India (gbif.net, online files). Worldwide, 15 other species of Clibanarius are known to host bopyrid parasites, while four species of Dardanus are known bopyrid hosts ( Markham 2003).

Figures

Figure 2. Parasymmetrione tuberculineata sp. nov. Holotype female (A–J). Allotype male (K–N). Paratype immature female (O). (A) Dorsal view; (B) ventral view; (C) left antennae; (D) right side of barbula; (E) right maxilliped, external view; (F) anteromedial corner of maxilliped; (G) right oostegite 1, external view; (H) right oostegite 1, internal view; (I) left pereopod 2; (J) right side of pleon, ventral view; (K) dorsal view; (L) ventral view; (M) right antennae; (N) right pereopod 7; (O) dorsal view. Scale: 1.00 mm for A,B; 0.15 mm for C,F; 0.32 mm for D; 0.38 mm for E; 0.43 mm for G,H,J; 0.40 mm for I; 0.30 mm for K,L; 0.14 mm for M,N; 0.75 mm for O.