Robinione, Boyko & Williams & Shields, 2017

Boyko, Christopher B., Williams, Jason D. & Shields, Jeffrey D., 2017, Parasites (Isopoda: Epicaridea and Nematoda) from ghost and mud shrimp (Decapoda: Axiidea and Gebiidea) with descriptions of a new genus and a new species of bopyrid isopod and clarification of Pseudione Kossmann, 1881, Zootaxa 4365 (3), pp. 251-301 : 278-279

Robinione n. gen.

Diagnosis. Female: Body ovate; all segments distinct. Frontal lamina weakly to moderately developed, smooth. Barbula with pair of lateral projections, either smooth or tuberculate; median region smooth or with series of low lobes. Maxilliped usually with setose palp ( Fig. 9 A ). First oostegites with tapered posterolateral point; internal ridge with numerous fimbriate projections. Coxal plates moderately developed on pereomeres 1–4 on both sides, margins crenulate; tergal projections present; lateral margins of pereomeres 1–4 crenulate, blunt, 5–6 not distinctly different from 1–4 ( Fig. 9 A ). Pereopods with elongate carpi, bases with large irregular, infolded mass on dorsal surface ( Fig. 9C, D ). Six pleomeres, first five produced into moderately to greatly developed lateral plates with crenulate edges, directed posterolaterally; five pairs of biramous pleopods, lanceolate, edges crenulate, external surfaces strongly tuberculate; uropods lanceolate, uniramous, margins crenulate and external surface tuberculate. Male: Body gradually tapered anteriorly and posteriorly from widest pereomere ( Fig. 10 A ); all body regions distinct. Anterior pereopods not markedly larger than others ( Fig. 10 A –C ). Pleon of six pleomeres, usually distinct but last two fused in one species; pleomeres either similar in shape to pereomeres or becoming progressively thinner and with tapered, posteriorly directed, lateral margins ( Fig. 10D ); pleopods uniramous, low, tuberculiform ( Fig. 10D ); posteriolateral margins of pleotelson slightly to strongly produced into posterolateral lobes; resembling uropods of the female in the type species ( Fig. 10 A, D ); true uropods lacking. Currently known only from the Americas (east coast of North America, Gulf of Mexico and west coast of South America), infesting hosts in Axiidea.

Type species. Pseudione overstreeti Adkison & Heard, 1995 .

Other included species. Pseudione brattstroemi Stuardo, Vega & Céspedes, 1986 .

Etymology. The genus is named in honor of Dr. Robin Overstreet for his many contributions to the field of parasitology. Because the type species epithet was based on Dr. Overstreet’s surname, we felt it appropriate to form the generic name based on his given name (combined with the bopyrid genus name Ione ). The gender is feminine.

Remarks. Robinione n. gen. can be distinguished from Pseudione sensu stricto by the following character states of the females (those of Pseudione in parentheses): 1) body outline ovate (elongate), 2) coxal plates with crenulated and tuberculate margins (margins smooth), 3) first oostegite with numerous filamentous projections along nearly all of inner ridge (inner ridge smooth or with only a few small rounded projections in proximal region), 4) bases of pereopods with large dorsal, irregular, infolded mass, larger and more complex sculpture in posterior pereopods (pereopods without dorsal mass), and 5) lateral plates and distolateral margins of pereomeres greatly expanded, lateral plates as broad as associated pleomeres (lateral plates and pereomeres not so expanded, lateral plates narrower than their respective pleomeres).

The females of R. overstreeti n. comb. and R. brattstroemi n. comb. are nearly identical. Based on the specimens examined herein and the descriptions of Stuardo et al. (1986a, b), the only obvious difference between the females is that the barbula of R. brattstroemi n. comb. has lateral lobes with crenulate margins (barbular lobes of R. overstreeti n. comb. are smooth). The males of the two species, however, are remarkably different. The males of R. brattstroemi n. comb. have few taxonomically important features at the species level, although Stuardo et al. (1986b) used SEM and found setae and other morphological characters that were useful for distinguishing this species from those in other genera. The male of R. overstreeti n. comb. is distinct in having the lateral margins of pleomeres 2–5, as well as those of the pleotelson becoming tapered and extended posteriorly. This is reminiscent of the condition of males in Ione ; however, in Ione , which belongs to a different bopyroid family than Robinione n. gen., the males have all the segments of the pleon fused (separate in R. overstreeti n. comb.) and all the pleon segments are modified (only 2–5 modified in R. overstreeti n. comb.). This pleonal condition was found in all males of R. overstreeti n. comb. examined in this study. The males of R. overstreeti n. comb. have rounded medial lobes on the pleomeres ( Fig. 10 A, D ), which may represent reduced pleopods. Finally, Stuardo et al. (1986b; Fig. 13) documented cephalic slits on the males of R. brattstroemi n. comb. and these were also found in the males of R. overstreeti n. comb. examined in the present study.

Figures

FIGURE 9. Scanning electron micrographs of Robinione overstreeti (Adkison & Heard, 1995), n. comb., mature female (ex Callichirus islagrande (Schmitt, 1935), ULLZ 10205). A, ventral overview of female; B, ventral view of head, left side, showing antennule (A1), antenna (A2), mouth (m), maxilliped palp (Mxp), and pereopod 1 (Pe); C, right pereopod 3, arrowhead indicates basis with dorsal mass; D, left pereopods 5–7 (left to right), arrowhead indicates basis with dorsalmass on pereopod 5; E, scales of basis of right pereopod 3; F, scales of carpus of right pereopod 3. Scale bars: A = 1 mm; B, C = 100 µm; D = 250 µm; E, F = 10 µm.

FIGURE 10. Scanning electron micrographs of Robinione overstreeti (Adkison & Heard, 1995), n. comb., mature male (ex Callichirus islagrande(Schmitt, 1935), ULLZ 10198).A, ventral overview of male; B, ventral view of head, left side, showing antennule, antenna, mouth, and pereopod 1; C, left pereopods 6 and 7 (top and bottom, respectively); D, ventral view of pleon, showing pleopodswith rounded medial lobes (noted on third and fourth pleopodsby asterisks).Scale bars: A = 500 µm; B, C = 100 µm; D= 200 µm.