Fabia emiliai (Melo, 1971)

Campos, Ernesto, 2013, Remarks on the sexual dimorphism and taxonomy of Fabia Dana, 1851 (Crustacea, Brachyura, Pinnotheridae), Zootaxa 3616 (2), pp. 190-200 : 194-197

Fabia emiliai (Melo, 1971)

( Figs. 3 A–E, 4A–E)

Pinnotheres emiliai Melo, 1971: 198 –200, fig. 1, pl. 1.—Fenucci 1975: 173, 175.—Martins & D’Incao 1998: 11, figs. 6, 14E.—Becerra et al. 2006: 1043.—Boschi 2008: unnumbered.—Ng et al. 2008: 249.

Fabia insularis Melo, 1971: 200 –202, figs. 2, 3. pl. 2.—Fenucci 1975, 173–175.—Martins & D’Incao 1998: 6–8: figs. 3, 4.—Becerra et al. 2006: 1043.—Boschi 2008: unnumbered.—Ng et al. 2008: 249.

Fabia emiliai— Fenucci 1975: 173–175, pl. 2 A, pl. 3 F, M, P.—Boschi 1979: 139 (list); 2000: 82.—Campos 1996: 1162, 1168.—Spivak 1997: 79.—Melo 1996: 438; 1998: 496.

Material examined. Observations were based on photographs of the holotype of Pinnotheres emiliai (MZUSP 3480) and Fabia insularis (MZUSP 3688) provided by Gustavo Augusto S. de Melo and the redescription and illustrations of Fenucci (1975).

Type locality. Baia de Ilha Grande, Rio de Janeiro, Brazil.

Distribution. Western Atlantic, Brazil from Rio de Janeiro to Rio Grande do Sul and Mar del Plata, Argentina (Melo 1971; Fenucci 1975; Martins & D’Incao 1998).

Hosts. Anadara brasiliana (Lamark, 1819) , Glycimeris longior (Sowerby, 1832) , Glycimeris sp. (Melo 1971; Fenucci 1975; Martins & D’Incao 1998)

Remarks. During the taxonomic revision of the Argentinean pinnotherid crabs, Fenucci (1975) discovered a sexually dimorphic pair of symbiotic crabs inhabiting the mantle cavity of the bivalve Glycimeris longior (Sowerby, 1832) . His study suggested that the adult hard stage male agreed with the holotype of Pinnotheres emiliai Melo, 1971 , while the late post-hard stage adult female could be identified with Fabia insularis Melo, 1971 . Fenucci (1975) accordingly synonymized both species, using the name P. emiliai and transferred it to Fabia , creating a new combination, F. emiliai (Melo, 1971) . Campos (1996) concurred with these changes during his revision of Fabia . Martins & D’Incao (1998), however, claimed they had discovered the “true” male of Fabia insularis and argued that it was different from P. emiliai restoring its original generic status. A comparative analysis between this putative male and those described by Campos (1996), Campos & Manning (1998) and herein, clearly show that the Martins & D’Incao´s (1998) specimen does not agree with the actual morphology of male Fabia . In fact, most of the described morphological characters agree with a sub-adult post-hard female of Fabia (sensu Pearce 1966) . The Martins & D’Incao´s specimen ( Fig. 3 ) shares the following features with other Fabia females 1) a soft and bare carapace with two sulci that arise from the orbits to the hepatic region, with no traces of setae on the anterolateral margin, (2) slender legs with the second pair asymmetrical, and (3) abdomen with six somites and telson all free. Martins & D’Incao (1998 fig 3-4) had figured what they labeled as a gonopod, but this appendage is so damaged that is difficult, at least on the basis of the original illustration, to recognize it as gonopod, unlike those figured by Campos (1996), Campos & Manning (1998) and herein ( Figs 2 C, 4E). Even assuming this appendage is a damaged or malformed gonopod, what Martins & D’Incao (1998) reported may only be an intersex individual. Intersex and gynandromorphs are generally uncommon among brachyuran crabs (see Zou & Fingerman 2000) and within the Pinnotheroidea in only four species have been recorded: Nepinnotheres androgynous Manning, 1993 ( Senegal, Africa), Nepinnotheres novaezealandiae Filhol, 1885 ( New Zealand), Alain croisneri Manning, 1998 , and Alain raymondi Ahyong and Ng, 2008 ( Philippines) (see Manning 1993, 1998; Ahyong & Ng 2008). Martins & D’Incao (1998) erroneously recognized an intersex female crab stage with a partially masculinized individual as the adult male of Fabia insularis and incorrectly concluded that this species is distinct from Pinnotheres emiliai .

Melo (1971) had inadvertently named two species in two genera on the basis of two fully developed adult specimens occurring in different hosts, but in fact belong to one dimorphic species. This unfortunate mistake was corrected by Fenucci (1975) as discussed above. While the intersex female discovered by Martins & D’Incao (1998) is a very interesting finding, it does not refute Fenucci´s (1975) conclusion. Nevertheless, Fenucci´s argument in favor of precedence of P. emiliai over F. insularis was because the former species appeared published two pages before (p. 198) than the latter (p.200) in Melo´s paper, which was technically incorrect. The International Code of Zoological Nomenclature (ICZN, 1999, article 24.2.2) indicates that if two species are published in a same paper both are nomenclaturally equal and there are no page priority. For this reason I am invoking the first reviewer rule (ICZN, 1999, article 24.2.1) of the Code in order to maintain the Fenucci´s selection of precedence in favor of P. emiliai .

Other American species that has been erroneously named based on different stages of development include, Juxtafabia muliniarum (Rathbun, 1918) [= Pinnotheres jamesi Rathbun, 1923 (male, hard stage), Pinnotheres muliniarum Rathbun, 1918 (male pre-hard stage), Pinnotheres reticulatus Rathbun, 1918 (female, post-hard stage)], Tumidotheres margarita (Say, 1818) [= Pinnotheres margarita Say, 1918 (adult female, post-hard stage), Pinnotheres pubescens (Holmes, 1895) (subadult female, post-hard stage] and Opisthopus transversus Rathbun, 1893 [= Pinnotheres nudus Holmes, 1895 (female, unknown stage)] (see Campos 1989; 1993; Campos & Manning 2000).

Campos (1996) and Ng et al. (2008) concluded that females of Fabia emiliai and F. byssomiae (Florida, USA) are morphologically similar and suggested both might be synonymous. A further comparative analysis between the descriptions and figures provided by Campos (1996), Melo (1971) and Fenucci (1975) for these species now show that they should be regarded as separate taxa. The carapace in F. byssomiae is sub-circular and the abdomen posteriorly curves gently to somites 3 and 4 before it folds towards the thoracic sternum, whereas in F. emiliai the carapace is sub-quadrate and the abdomen posteriorly extends to somite 3 and 4 before it folds towards the thoracic sternum. More specimens will be needed to ascertain if there are more differences; but they should be regarded as distinct species for the time being.

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.

FIGURE 3. Fabia insularis Melo, 1971, A – C, E, from Rio Grande do Sul (FURG- 1235), D, from Rio de Janeiro, Brazil (MZUSP 3688), sub-adult female; A, dorsal view; B, ventral view; C, ventral view of thoracic sterna; D, P 3, longer left and shorter right; E, left gonopod. Scale A – C = 2 mm; D = 1.7 mm; E = 1 mm. (A – C, E from Martins & D’Incao, 1998; D, from Melo 1971).