Fabia hemphilli (Rathbun, 1918) Rathbun, 1918

Campos, Ernesto, 2013, Remarks on the sexual dimorphism and taxonomy of Fabia Dana, 1851 (Crustacea, Brachyura, Pinnotheridae), Zootaxa 3616 (2), pp. 190-200 : 192-194

Fabia hemphilli (Rathbun, 1918) new combination

( Figs. 2 A–D)

Pinnotheres hemphilli Rathbun, 1918: 64 –65, 99–100, pl. 23, figs. 1, 2.—Archer 1947: 12 (popular account).—Schmitt et al. 1973: 48 (list); Powers 1977:123 (listed).—Abele & Kim 1986: 65, 685, 703 (unnumbered figures a–b).— Ng et al. 2008: 249 (list).

Material examined. 1♀ holotype USNM 6420 (post-hard stage, probably II), Cedar Keys, Florida; between tides; “seems rare”, cl = 2.3 mm, cw = 3 mm.

Distribution. Known only from the type-locality, Cedar Keys, Florida, U.S.A.

Redescription (modified from Rathbun 1918: 99). Caparace suboctagonal, thin, transparent, depressed, wrinkled; with 2 ill-defined sulci arising posterior to orbits reaching gastric region; eyes dorsally visible; front subrectangular; posterior margin twice as long as anterior margin, mid-lateral margin subparallel to median line, as long as postlateral margins, anterolateral margins (to angles of front) longest, biconvex.

Third maxilliped short, wide in situ; partly overlapped by anterior portion of thoracic sternum; outer margin of ischium-merus broadly arcuate; palpus with first 2 joints short, broad, carpus slightly shorter than sub-trapezoidal propodus, dactylus digitiform, small, inserted in notch near middle of ventral margin of propodus.

P1 robust, tuft of setae at distal inner angle of merus, manus nearly as wide as superior length, slightly increasing distally in width, upper margin almost straight, lower convex, distal width greater than width across base of fingers; fingers basally broad, regularly tapering, denticulate on prehensile edges, tooth at base of right dactylus.

P2–P5 slender, feeble, relative length P3> P4> P2> P5, P2 subchelate, propodus widest medially slightly tapering distally, with fringe of setae on distal half of ventral margin; P3 substantially longer than the other walking legs, asymmetrical, left longer than right, all propodi dorsally convex, those propodi of P4–P5 slightly increasing in height to distal end; dactyli of P2, P4–P5 subequal in form, very stout at base, subconical, with short curved tip, those of P3 longer, less curved.

Thoracic sternum with a sharp obliquely transverse crest running inward from base of first, second, third pair.

Abdomen widest at somite 3, narrowing to somite 6 widening slightly at semicircular telson, suture between somites 3, 4 and 5, 6; telson faintly demarcated.

Remarks. The holotype of Fabia hemphilli is an atypical specimen since it possesses some masculine and feminine morphological features attributable to both sexes within the genus Fabia . The presence of two sulci, although ill-defined, on the carapace that arise behind the orbits and reach to the gastric region, the asymmetrical P3, and the anterolateral margins not protruding beyond the frontal margin are clearly feminine features, whereas the rectangular front, the dorsally visible eyes and the narrow abdomen with several somites giving the appearance of being fused, are masculine features. As previously pointed out, hard males and females are almost identical, and can only be separated by the presence of gonopods. After the hard stage, females undergo several post-hard stages that are characterized by the phased appearance of feminine features on the carapace and P2-P5 and by the gradual lateral enlargement of the abdominal somites (see Pearse 1966). The morphology of the very small (cw = 3 mm) holotype of F. hemphilli allow the conclusion that it is not a male as identified by Rathbun (1918), but an early post-hard female. Its morphology, including the narrow abdomen, compares well with the post-hard female stage II of Fabia subquadrata (Pearse, 1966) . The morphology of this sub-adult female, especially the form of the chelipeds and P2-P5, actually agrees very well with F. byssomiae Say, 1818 (Campos 1996: fig 1), a species known from Tampa Bay, Florida, U. S.A., a locality close to Cedar Key, Florida, the type locality of F. hemphilli . Examination of additional specimens, including males and females in pre-hard, hard stage and females in post-hard stage, will be necessary to confirm if F. hemphilli is indeed an early post-hard stage and therefore a junior synonym of F. byssomiae . Both are regarded here as separate species for the time being. The masculine shape of the abdomen and third maxilliped of F. hemphilli do not match those of the known males of the Atlantic congeners (see Campos 1996). Instead, the third maxilliped and the abdomen of F. hemphilli actually resemble those of the male holotype of F. malaguena (Garth, 1948) , a species that inhabits the Pacific coast of Colombia (Campos & Manning 1998).

Figures

FIGURE 2. Fabia hemphilli (Rathbun, 1918) new combination, Cedar Keys, Florida, U. S. A., holotype (USNM 6420), caparace length 2.3 mm, width = 3 mm. A, dorsal view; B. ventral view, sterna details omitted; C, abdomen; D, third maxilliped, outer view.