Pseudione stylopoda, Boyko, 2004

Boyko, Christopher B., 2004, The Bopyridae (Crustacea, Isopoda) parasites of the Stylodactylidae (Crustacea, Decapoda, Caridea), Zoosystema 26 (2), pp. 199-210 : 200-204

publication ID	https://doi.org/ 10.5281/zenodo.5400151
persistent identifier	https://treatment.plazi.org/id/03EB87C8-FFEA-1E4C-FCC0-8BBA405EF95B
treatment provided by	Marcus
scientific name	Pseudione stylopoda
status	sp. nov.

Treatment

Pseudione stylopoda View in CoL n. sp.

( Figs 1-4 View FIG View FIG View FIG View FIG )

“bopyre” Cleva 1997: 392, 398.

TYPE MATERIAL. — Vanuatu. MUSORSTOM 8, stn CP 1137, 15°41.52’S, 167°02.67’E, 350-371 m, 11.X.1994, in left branchial chamber of Stylodactylus multidentatus multidentatus Kubo, 1942 , 10 mm CL (MNHN-Na 13217), holotype brooding sinistral 8.1 mm GoogleMaps ; allotype 3.2 mm (MNHN- Ep 905).

MATERIAL EXAMINED. — New Caledonia. BATHUS 1, stn CP 670, 20°54.0’S, 165°53.4’E, 394- 397 m, 14. III.1993, in right branchial chamber of ovigerous Parastylodactylus richeri Cleva, 1990 ,

5.0 mm (MNHN-Na 14631), 1 immature paratype 3.8 mm (MNHN-Ep 906).

ETYMOLOGY. — The specific name is given to denote the styliform endopodites of pleopods IV and V, as well as the occurrence of the species on hosts in the Stylodactylidae .

DISTRIBUTION. — Known from Stylodactylus multidentatus multidentatus from Vanuatu and Parastylodactylus richeri from New Caledonia. Depth: between 350 and 397 m.

DESCRIPTION

Female ( Figs 1 View FIG ; 2 View FIG )

Based on holotype. Body length 8.1 mm, maximal width 5.4 mm, head length 1.8 mm, head width 2.4 mm. Pereon somewhat sinuous but essentially straight, left side slightly longer than other (sinistral) ( Fig. 1 View FIG ). All body regions and pereomeres distinctly separated.

Head broader than long, moderately produced with anterior lamina equal to approximately oneseventh length of head ( Fig. 1A View FIG ). Small eyes present. Antenna of five articles, antennule of three articles ( Fig. 2A View FIG ). Maxilliped ( Fig. 2B View FIG ) with thin distally rounded spur; palp narrow, distally tapering and rounded, non-articulating, with four thick, elongate setae distally and numerous short, thin setae on dorsal margin. Pereon of seven pereomeres, broadest across pereomere III, tapering anteriorly and posteriorly; pereomere I with convex posterior margin, II with slightly sinuous posterior margin, II-VII with strongly concave posterior margins; approximately three-fourths of pereomere I median obscured by head. First oostegite with proximal lobe subquadrate, distal lobe subtriangular, distally tapering and rounded, internal ridge with one small, smooth lobe proximally and one large, elongate lobe distally ( Fig. 2C, D View FIG ). Coxal plates as small lobes on pereomeres I-IV, clearly separated from pereomeres. Dorsolateral bosses clearly demarcated with left and right sides subequal. Pereomeres III and IV with distinctly demarcated tergal area, not projecting. Oostegites enclosing only approximately half of marsupium. Pereopods V-VII longer than I-IV ( Fig. 2E, F View FIG ). Dorsal margin of propodus and ventral margin of merus with thin band of scales; propodus elongate. Bases of pereopods lacking bosses. First pair of pereopods surrounding head region; I-IV evenly spaced, V-VII closely approximated.

Pleon with five distinct pleomeres plus pleotelson; posterior margins of pleomeres I-III smoothly and moderately concave, those of IV and V sharply concave ( Fig. 1A View FIG ). Pleomeres I-V with biramous pleopods and uniramous lateral plates ( Figs 1B View FIG ; 2G View FIG ); pleomeres I-III with subequal lamellar exopodites, broad proximally and distally tapering, endopodites as small lobes arising from common base with exopodites, endopods of pleopods I and II subequal, those of pleopod III smaller; pleomeres IV and V with exopodites long, thin, and only tapering at tip, endopodites thin, styliform, arising from lateral margin of exopodites; lateral plates on longer side lamellar and laterally separate, I-III directed laterally, IV and V sharply directed posteriorly, lateral plates on shorter side thinner with I-III pressed together; edges and surfaces of all lateral plates smooth; uropods uniramous, of nearly same shape and size as exopodite of pleopod V.

Male ( Figs 3 View FIG ; 4 View FIG )

Based on allotype. Length 3.2 mm, maximal width 1.0 mm, head length 0.4 mm, head width 0.6 mm, pleon length 1.0 mm.

Head subovate, widest posteriorly, distinct from first pereomere ( Fig. 3A View FIG ). Eyes present, small. Antenna of seven articles, distally setose, extending beyond margin of head; antennule of three articles, distally setose ( Fig. 4A View FIG ).

Pereomeres IV and V broadest, tapering anteriorly and posteriorly. Pereomeres I-V directed laterally, VI and VII directed slightly posterolaterally, distolateral margins of all pereomeres rounded. No detectable pigmentation. Pereopods ( Fig. 4B, C View FIG ) all subequal, all articles distinctly separated, palm of propodus with row of low blunt stout setae and surrounding region of granules, distoventral tip of carpus with granules and few distal setae.

Pleon of six separate pleomeres. Pleomeres I-II directed laterally, III-V directed slightly posterolaterally, distolateral margins of all pleomeres rounded. Pleomere VI (pleotelson) subtriangular with posterolateral lobes of approximately half its length; mediodistal margin with small anal cone, distal tips of posterolateral lobes with tufts of short setae ( Fig. 3B View FIG ). Pleopods as low, lateral, hemispherical swellings on pleomeres I-V ( Fig. 3B View FIG ). No midventral tubercles or uropods.

Variations

The only paratype is an immature female that shows no body distortion and has poorly developed oostegites and lateral plates on the pleomeres. This specimen would be difficult to identify, were it not for the shape and configuration of the endopodite and exopodite of pleopod V which are identical to those of the holotype.

REMARKS

The host of the immature female is an ovigerous specimen but, although not all species of bopyrids are absolute sterilizers of their hosts (Boyko pers. obs.), in this case it is likely that the juvenile state of the parasite was insufficient to influence the reproductive development of the host. Egg production by the host might have ceased as the parasite matured.

The species closest to P. stylopoda n. sp. is P. pontocari Page, 1985 . Females of both species have the same distinctive styliform shape of the endopods of pleopods IV and V. The two species are also similar in the development of the female’s maxilliped palp and shape of the pereopods (although the latter were incompletely described by Page [1985]) and the number of segments in the antenna and antennules of the male. Females of the two species differ in the shape of the lateral plates of the pleon (broad and produced only on the longer side in P. pontocari vs thin and well developed on both sides in P. stylopoda n. sp.), the inner ridge of the first oostegite (several short lobes in P. pontocari vs one long and one short lobe in P. stylopoda n. sp.), and the number of segments in the antennule and antenna (three and seven in P. pontocari vs three and five in P. stylopoda n. sp.). The males differ in the degree of development of the pleopods (more developed in P. pontocari ) and the projection of the posterolateral pleotelson (longer in P. pontocari ). The males also differ in characters such as the presence of eyes (only in P. stylopoda n. sp.) and the fusion of the head with pereomere I (only in P. pontocari ), but these characters are often variable within a species and are of dubious utility in delimiting taxa (see also Boyko & Williams 2001).