Rhopalione sinensis Markham, 1990

Boyko, Christopher B. & Williams, Jason D., 2024, New records of bopyrid parasites (Crustacea, Isopoda, Epicaridea) of pea crabs (Crustacea, Decapoda, Pinnotheridae) with descriptions of two new species of Rhopalione Pérez, 1921 and a review of the genus, Zoosystema 46 (7), pp. 149-175 : 165-166

Rhopalione sinensis Markham, 1990

( Fig. 7 )

Rhopalione uromyzon – Nierstrasz & Brender à Brandis 1931: 175- 176 [host unknown, Zamboanga, Philippines; specimen examined herein] (not Rhopalione uromyzon Pérez, 1920 ).

Rhopalione sinensis Markham, 1990: 555 , 560-562, fig. 3 (ex Pinnotheres sinensis atrinae Sakai, 1939 (now Arcotheres atrinae (Sakai, 1939)) , Hong Kong); 1992: 299, table 1 [list]. — Huang 1994: 530 [list]; 2001: 327 [list]. — Li 2003: 140, 153, 158, table 1 [list]. — Morton 2003: 43, table 4 [list]. — An et al. 2009: 351 [list]; 2014: 1-2, fig. 1 (ex Arcotheres sinensis (Shen, 1932) , Fujian Province, China), 4 [key to species]. — McDermott 2009: 790, 792, table 2 [list]. — Kuo et al. 2018: 1434-1448, fig. 1 (ex A. sinensis , Taiwan). — Ahyong & Boyko 2019: 286 [comparison with R. kali ], 287 [key to species]. — Williams et al. 2023: 533 [list], 539 [mention].

TYPE MATERIAL EXAMINED. — China • non-ovigerous holotype ♀ (3.9 mm TL), ex ♀ Pinnotheres sinensis atrinae Sakai, 1939 (now Arcotheres atrinae (Sakai, 1939) (6.5 mm CW); Hong Kong, Deep Bay , 16.IV.1954; B. Morton leg.; USNM 233554 .

OTHER MATERIAL EXAMINED. — Philippines • 1 non-ovigerous ♀ (7.13 mm TL), ex unknown host (pinnotherid); Zamboanga, St. Cruz Island ; 24.II.1914; Dr Th. Mortensen’s Pacific Expedition 1914-16, leg.; NHMD-1184775 .

DESCRIPTION (modified from Markham 1990; An et al.

2014)

Female

Body nearly straight, ovate in outline, longer than wide; all segments distinct. Head ovate, separated from pereon, wider than long, anterior and posterior margins convex, lateral margins rounded; thin frontal lamina. Eyes absent. Antennules of three articles each, antennae of five articles each, both setose, neither visible dorsally. Maxilliped longer than wide; broad non-articulated palp, apex rounded; plectron short, slender, straight. Barbula with one or two pairs of smooth, slender falcate projections laterally, weakly concave medially. Pereon nearly straight. Pereomeres dorsally distinct, produced laterally into tapered, rounded lobes; widest at pereomere 4; margins straight or weakly curved, mid-dorsal bosses and projections absent; irregularly-shaped dorsolateral bosses and rounded coxal plates on all seven pereomeres. Oostegites completely enclosing brood pouch, strongly vaulted ventrally, protruding beyond anterior margins of body, visible dorsally. Oostegite 1 longer than wide; anterior lobe rounded, larger than distal lobe; internal ridge digitate; posterior lobe with acute, nearly straight distal projection on margin. Oostegite 5 posterior margin fringed with setae. Pereopods isomorphic, subchelate. Pleon short, five pleomeres, all dorsally distinct, each with lateral plates produced into slender, distally rounded lobes, similar in size and shape to corresponding five pairs of biramous pleopods. Uniramous uropods similar in size and shape to pleopods and adjacent lateral plates of pleomere 5.

Male

Body elongate, fusiform, straight, length 3.0 × width; all segments distinct. Head transversely ovate in dorsal view, longer than pereomere 1; anterior margin broadly curved, medially concave; posterior margin broadly curved; eyes present. Antennules of three articles each, antennae of six articles each, both with terminal setae. Pereomeres 1-7 subequal in length, lateral margins rounded, pereomere 1 with posterior margin concave; all pereomeres subequal in width; midventral projections absent. Pereopods isomorphic in size and shape, subchelate. Pleon with tapered outline; pleomeres distinct, distal margins rounded, posteriorly recurved, apices blunt; pleopods 1-5 bulbous, uniramous. Pleotelson indented posteriorly.

REMARKS

Markham (1990) described R. sinensis based on the holotype female from Hong Kong. He noted that it closely resembled the female of R. uromyzon , but that R. sinensis had a head broader than long, well separated coxal plates, and indistinct dorsal separation of pleomeres whereas R. uromyzon had a nearly oval head, “somewhat separated coxal plates”, and distinct dorsal separation of all pleomeres. The holotype of R. sinensis was examined and found to agree with the description of Markham (1990) in all features except that the five projections on the inner ridge of the oostegite 1 are more clearly demarcated and spaced than indicated by Markham (1990: fig. 3I) and more like those seen in specimens of R. uromyzon from the Persian Gulf, and that the inner projection of the barbula is present, but only about half the length of the outer projection. Additionally, examination of the maxilliped and oostegite 1 of R. uromyzon shows them to be indistinguishable from those of R. sinensis . Based on female morphology, it is very difficult to distinguish R. sinensis from R. uromyzon except for the shape of the pleopods, which are much slenderer and more elongate in R. sinensis ; however, the males do show differences in that those of R. sinensis have the pleopods displaced laterally while those of R. uromyzon have the pleopods located closer to the pleon median.

The single female specimen ( Fig. 7 ) from the Philippines cited by Nierstrasz & Brender à Brandis (1931) was examined and is identifiable as R. sinensis rather than R. uromyzon ; it matches in body form ( Fig. 7A, B ), maxilliped ( Fig. 7D ), and oostegite 1 ( Fig. 7E ) morphology. The host for this specimen was given by Nierstrasz & Brender à Brandis (1931) as a Pinna bivalve but, as pointed out by Page (1985), the host must have been a Pinna -infesting pinnotherid.

Figures

FIG. 7. — Rhopalione sinensis Markham, 1990 (NHMD-1184775): A, female, dorsal view; B, female, lateral view; C, left oostegite 1, inner view; D, left maxilliped, outer view. Scale bars: A, B, 2 mm; C, D, 100 µm.