Rhopalione racemus, Boyko & Williams, 2024

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 : 167-169

publication ID	https://doi.org/ 10.5252/zoosystema2024v46a7
publication LSID	lsid:zoobank.org:pub:A7CA7D85-2633-4930-BA12-ACFCB3D0DE21
DOI	https://doi.org/10.5281/zenodo.10881725
persistent identifier	https://treatment.plazi.org/id/91BC048C-A4A0-4959-A322-504403BE1E36
taxon LSID	lsid:zoobank.org:act:91BC048C-A4A0-4959-A322-504403BE1E36
treatment provided by	Plazi
scientific name	Rhopalione racemus
status	sp. nov.

Treatment

Rhopalione racemus n. sp.

( Figs 8 View FIG ; 9 View FIG )

urn:lsid:zoobank.org:act:91BC048C-A4A0-4959-A322-504403BE1E36

“large parasitic Isopod (Epicarid)” – Hale 1927: 174 [ex Pinnotheres subglobosus Baker, 1907 (now Discorsotheres subglobosus (Baker, 1907) , Gulf St. Vincent, South Australia; specimen examined herein]. — Silas & Alagarsiwami 1967: 1191 [reference to Hale’s findings].

“the isopod mentioned by Hale” – Page 1985: 201 [mention].

? “an undescribed species of Rhopalione ” – Poore et al. 2002: 124 [see Remarks below].

Rhopalione sp. – McDermott 2009: 792, table 2 [list]. — An et al. 2014: 2, table 1 [list]. — Ahyong 2018: 557 [ ex Discorsotheres subglobosus (Baker, 1907) View in CoL , Gulf St. Vincent, South Australia]. — Williams et al. 2023: 533 [list].

TYPE MATERIAL. — Holotype. Australia • ovigerous ♀ (8.9 mm TL), from under pleon of ♀ Discorsotheres subglobosus (Baker, 1907) (10.5 mm CL, 11.7 mm CW), ex Equichlamys bifrons (Lamarck, 1819) ( Pectinidae Rafinesque, 1815 ); South Australia, Port Willunga; 25.II.1990; N. Holmes leg.; SAM C16386.

Allotype. Australia • mature ♂ (3.8 mm TL), collected with holotype; South Australia, Port Willunga ; 25.II.1990; N. Holmes leg.; SAM C16386 View Materials .

Paratype. Australia • 1 mature ♀ (6.4 mm TL; male not present), from under pleon of female D. subglobosus (7.6 mm CL, 8.6 mm CW), ex E. bifrons ; South Australia, Gulf St. Vincent; no date; A. Zietz leg.; SAM C1397.

ETYMOLOGY. — The specific name, racemus , is a Latin noun meaning a bunch of grapes, which the shapes of the pleopods and lateral plates resemble; it is used in apposition.

DESCRIPTION

Female

Holotype ( Figs 8A, B View FIG , 9 View FIG A-H). Length 8.9 mm; maximal width at posterior margin of pereomere 46.9 mm (not including coxal plates); head length 1.5 mm; head width 1.8 mm. Body nearly straight ( Fig. 8A, B View FIG ), subcircular in outline but slightly longer than wide when including coxal plates, not distorted; all segments distinct. Head ovate, separated from pereon, slightly wider than long, anterior and posterior margins convex, lateral margins rounded; wide frontal lamina. Eyes absent. Antennules ( Fig. 9A View FIG ) of two articles each, antennae ( Fig. 9A View FIG ) of five articles each, both visible dorsally, few setae distally. Maxilliped ( Fig. 9C View FIG ) longer than wide; narrow non-articulated palp with blunt apex; spur elongate, slender, distally actute. Barbula ( Fig. 9B View FIG ) laterally with outer elongate, smooth, slender falcate projection and inner short acute curved projection; shallowly convex medially. Pereon nearly straight ( Fig. 8A View FIG ). Pereomeres dorsally distinct, produced laterally into blunt, rounded lobes; widest at pereomere 4; margins weakly curved, mid-dorsal bosses or projections absent; irregularly shaped dorsolateral bosses and coxal plates on all seven pereomeres, dorsolateral bosses and coxal plates in posterior pereomeres not fused. Oostegites completely enclosing brood pouch ( Fig. 8B View FIG ), strongly vaulted ventrally, protruding beyond anterior margins of body, visible dorsally. Oostegite 1 ( Fig. 9D, E View FIG ) longer than wide; anterior lobe rounded, subequal in length to distal lobe; internal ridge with numerous irregular slender digitations ( Fig. 9E View FIG ); posterior lobe with acute, triangular distal projection on margin. Oostegite 5 ( Fig. 9F View FIG ) posterior margin fringed with setae. Pereopods isomorphic, subchelate ( Fig. 9G, H View FIG ); small curved dactylus, propodus ovate, carpus and merus fused, ischium and basis tubular, relatively short ( Fig. 9G View FIG ). Pleon short ( Fig. 8A View FIG ; 9F View FIG ), five pleomeres, all dorsally distinct, each with lateral plates produced into short, distally rounded lobes, similar in size and shape to corresponding five pairs of biramous pleopods ( Fig. 9F View FIG ). Uniramous uropods ( Fig. 9F View FIG ) similar in size and shape to pleopods and adjacent lateral plates of pleomere 5.

Male

Allotype ( Figs 8C View FIG ; 9 View FIG I-L). Length 3.8 mm; maximal width at posterior margin of pereomere 4 1.6 mm; head length 0.4 mm; head width 0.9 mm. Body elongate, fusiform, straight, length 2.4 × width; all segments dorsally and ventrally distinct ( Figs 8C View FIG ; 9I View FIG ). Head transversely ovate in dorsal view, about two-thirds as long as pereomere 1 (along midline) ( Fig. 8C View FIG ); anterior and posterior margins nearly straight; eyes absent. Antennules ( Fig. 9J View FIG ) of three articles each, antennae ( Fig. 9J View FIG ) of five articles each, both with terminal setae. Pereomeres 1-7 ( Figs 8C View FIG ; 9I View FIG ) subequal in length, lateral margins subquadrate, posterior margins straight or at most slightly concave; pereomeres 1 and 7 subequal in width, 0.85 × width of pereomere 2; pereomeres 2-6 subequal in width; midventral projections absent ( Fig. 9I View FIG ). Pereopods isomorphic in size and shape, subchelate; dactyli of anterior pair longer than others, setose; propodus ovate, with setae along edge corresponding to region meeting distal end of dactylus; carpus and merus fused, end of carpus with small setae; ischium and basis tubular, bases longer on posterior pereopods ( Fig. 9K, L View FIG ). Pleon ( Figs 8C View FIG ; 9I View FIG ) broadly tapering to rounded general outline; pleomeres dorsally and ventrally distinct, distal margins produced, posteriorly slightly recurved, lateral margins rounded, medioventral tubercles absent; pleopods 1-4 ( Fig. 9I View FIG ) reniform, pleopods 5 rounded, uniramous. Pleotelson ( Fig. 8C, I View FIG ) slightly indented posteriorly.

REMARKS

Females of Rhopalione racemus n. sp. can be distinguished from all other species in the genus by the shape of the pleopods and lateral plates which are short and rounded; females of all other species have markedly elongate pleopods and lateral plates. The specimens reported by Hale (1927) are the paratypes examined and designated as such herein. We consider the specimens cited by Ahyong (2018; SAM C12813) that were collected from same host species in a known locality (Gulf St. Vincent) for R. racemus n. sp. to be this species, although they were not examined for this study.

Poore et al. (2002) noted that “an undescribed species of Rhopalione has been identified from Australia by J. Markham” but this has not been described; it may be conspecific with R. racemus n. sp. but given the lack of information on the locality and host, this is far from certain.