Epialtus parvulus, Tavares & de Mendonça, 2022

In, First Published, 2022, Brachyuran crabs (Crustacea, Decapoda) from the remote oceanic Archipelago Trindade and Martin Vaz, South Atlantic Ocean, Zootaxa 5146, pp. 1-129 : 30-35

Epialtus parvulus sp. nov.

( Figs. 14A–E , 15A, C, E, G, H, J, K, M , 16A–E , 17A–E )

Trindade and Martin Vaz specimens. Holotype male, cl 6.4 mm, cw 5.1 mm, ( MZUSP 40577 ), off Espírito Santo, Trindade Island, Ponta do Monumento, 20º30’10.3’’S, 29º20’36.1’’W, J.B. Mendonça coll., 13.vii.20º12, 8.1 m. 1 ovigerous female paratype, cl 6.5 mm, cw 5.6 mm ( MZUSP 39678 ), ibidem, Ponta Noroeste, 20º29’46.4’’S, 29º20’46.4’’W, J.B. Mendonça coll., 28.xi.2017, 9.4 m, on foliaceous calcareous reddish algae. 1 young female paratype, cl 3.8 mm, cw 2.9 mm ( MZUSP 39679 ), ibidem, Enseada das Orelhas, 20º29’40.2’’S, 29º20’32.9’’W, J.B. Mendonça coll., 16.v.2014, 10.4 m. 1 male paratype, cl 4.4 mm, cw 3.2 mm ( MZUSP 40975 ), ibidem, 30.vi.2012, 14.4 m. 1 juvenile female paratype ( MZUSP 40687 ), ibidem, Enseada da Cachoeira , Farrilhões, 20º31’2.4’’S, 29º19’52.0’’W, J.B. Mendonça coll., 5.v.2014, 14.4 m. 1 male paratype, cl 6.4 mm, cw 5.0 mm ( MZUSP 40727 ), Martin Vaz Archipelago, 20º30’45.7’’S, 29º18’21.9’’W, J.B. Mendonça coll., 23.vii.2013, washed algae, 13 m. 1 ovigerous female paratype, cl 6.4 mm, cw 5.5 mm ( MZUSP 33814 ), ibidem, J.B. Mendonça coll., 24.vii.2013, 12.3 m.

Comparative material examined. Epialtus bituberculatus : Brazil: Rio Grande do Norte: 1 female ( MZUSP 22570 ), Rio do Fogo, Praia de Zumbi, 05º19’908’’S, 35º21’607”W, stn 29, Tavares et al. coll., 27.xi.2009, fisherman beach pulling net. 3 males, 11 females ( MZUSP 22660 ), Praia de Genipabu , 05º41’630”S, 35º12’210’’W, stn 2, Tavares et al. coll., 16.xi.2009, 0.2 m, washed algae. Espírito Santo: 1 male, 1 ovigerous female ( MZUSP 32450 ), Aracruz, 2.xii.1987. Rio de Janeiro: 5 males, 5 females ( MZUSP 2788 ) , Ilha Grande, Praia do Funil, 24.vii.1966. São Paulo : 3 males ( MZUSP 1713 ) , São Vicente, Ilha das Vacas, Stowbunenko coll., 1962. Epialtus brasiliensis : Rio de Janeiro: 1 male, 1 ovigerous female ( MZUSP 41772 ), Cotunduba Island , 22º57’55.76’’S, 43º109’02.09” W, J.B. Mendonça coll., 14.xi.2009, 6.7 m. Epialtus elongatus : United States: Florida: holotype male, cl 12 mm, cw 8.2 mm ( USNM 47090 ), R/V “ Fish Hawk ”, stn 7429, off Duck Key, 9.ii.1899, 4 m. Epialtus longirostris : Bahamas: 1 male, cl 4.5 mm, cw 3.0 mm ( USNM 88670 ), Bimini, A.S. Pearse coll., 2.xi.1948, dredge [F. Chace det.] . Cuba: 1 male, cl 7.5 mm, cw 5.5 mm ( USNM 48742 ), Co. S.R., stn 14, Tomas Barrera Expedition, Henderson and Bartsch coll., on reef Lavesos, Italianos, opposite Cayo Lavesos, 3–5 m [M. J. Rathbun det. 1925.] . Jamaica: 1 female, cl 6.5 mm, cw 4.5 mm ( USNM 43019 ), E. A. Andrews coll., 1910 [M. J. Rathbun det. 1925.] . Porto Rico: 1 juvenile male, cl 8.0 mm, cw 5.5 mm ( USNM 75097 ), W.S. Schmitt coll., 29.iii.1937 [M. J. Rathbun det. as E. longirostris forma portoricensis ]. 1 female, cl 8.1 mm, cw 6.0 mm ( USNM 1462844 ) , U.S. Fish Commission Porto Rico Expedition, R/V “ Fish Hawk ” 1898–1899, no further details. Epialtus portoricensis : Porto Rico: holotype male, cl 5.4 mm, cw 3.7 mm ( USNM 24154 ), R/V “ Fish Hawk ”, 9.ii.1899, Culebra Island, Ensenada Honda .

Type locality. Ponta do Monumento , 20º30’10.3’’S, 29º20’36.1’’W, 8.1 m, Trindade Island, off Espírito Santo, Brazil .

Distribution. Currently known only from the Trindade and Martin Vaz Archipelago.

Description of the holotype. Carapace ( Figs. 14A , 15A ) generally smooth, little longer than wide, length 1.2 times greatest width (about 1.3 times width in the juvenile female), very slightly narrower across hepatic region than across the branchial region. Greatest width at level of branchial lobe. Hepatic and branchial lobes distinctly broad triangular, hepatic larger than branchial, margins minutely granulated. Anterior margin of hepatic lobe produced into low hump situated a little beyond halfway from eye to tip of hepatic lobe. Lateral margin between hepatic and branchial lobes deeply concave in dorsal view outline. Carapace surface with 2 low small protogastric elevations, each bearing minute granules; cardiac region delimited laterally by semicircular shallow furrow. Rostrum strongly depressed, rather short, moderately broad triangular, tip rounded; ventral surface deeply concave to receive antennule, grooved terminally ( Fig. 14B ). Preorbital angle distinctly cut, broadly concave. Preorbital tooth prominent, blunt, minutely granulated. Eyes relatively large, visible in dorsal view. Postorbital notch deeply and roundly incised ( Figs. 14A , 15A ). Supraorbital margin continuing gradually into anterior margin of hepatic lobe. Subhepatic region swollen. Antennal peduncle (flagellum excluded) much shorter than rostrum.

Chelipeds ( Figs. 14A, B , 15E ) rather long, homochelous, homodonts. Fingers much shorter than half of maximum length of propodus (measured along dorsal margin), gapping proximally when closed, deeply spoon-shaped, each finger provided with many long stiff setae along near cutting edge intermingled with each other. Cutting edges crenulated. Dactylus rather massive, strongly curved downward and inward. Propodus progressively widening distally, slightly swollen mesially and laterally. Carpus oblong in dorsal view ( Fig. 15C ). Merus subtriangular in crosssection distally; two joint tubercles about half length of dorsal surface.

P2 ( Fig. 14A, B ) longer than remainder, little shorter than P1. Dactylus shorter than propodus (measured dorsally), distal 2/3 dentate ventrally, teeth small. Propodus about 3.5 times as long as high (measured dorsally), lateral surface ending in disc-like projection covering base of dactylus. Carpus slightly shorter than propodus and merus. Merus little less 3.5 times as long as high (measured dorsally).

P3–P5 (Figs. 14A, B, 15J) of similar shape, P5 shortest. Dactyli slightly longer than propodi (measured dorsally), distinctly more robust and curved than that of P2; ventral surface armed with two longitudinal rows of evenly spaced acute teeth. Propodi little less than 2.5 times as long as high, without tooth of setae near proximal end, lateral surface ending in disc-like projection covering base of dactyli. Carpi little shorter than propodi, meri distinctly longer than propodi. P5 merus length (measured along dorsal margin) distinctly less than two times merus width.

Male pleonal somites 4–5 fused; anterolateral angle of sixth somite produced, rounded ( Figs. 14B , 15H, K, M ).

G1 ( Fig. 16A–E ) nearly straight, reaching well beyond thoracic sternal suture 4/5; distal keel membranous. G2 very short, about 1/3 of the length of G1, tapering slightly distally, ending in truncate tip.

The females ( Figs. 14C–E , 17A–E ) essentially differ from the males in having the carapace branchial lobe incised into two small teeth; the anterior margin of the hepatic lobe provided with a distinct blunt tubercle situated a little beyond halfway from the eye to tip of hepatic lobe; the rostrum truncate with incised tip; the preorbital angle distinctly cut, broadly V-shaped; shorter chelipeds with two small tubercles on the merus subproximal dorsal surface. The broad pleon reaches to the base of the legs and the pleonal somites 4–6 are fused with indiscernible sutures.

Etymology. The specific epithet is taken from the Latin diminutive adjective “parvulus” (little) in reference to the small size of this new species.

Ecological notes. In Trindade and Martin Vaz on foliaceous calcareous, reddish algae and washed algae, between 8– 13 m.

Remarks. Epialtus parvulus sp. nov. can be easily separated from E. bituberculatus by a combination of characters which include (characters for E. bituberculatus between brackets): 1) carapace only slightly narrower across the hepatic region than across the branchial region ( Figs. 14A, C, E , 15A , 17A ) (vs carapace distinctly narrower across the hepatic region than across the branchial region, Fig. 15B ); 2) hepatic lobe distinctly cut, broad triangular, broader than the branchial lobe ( Figs. 14A, C, E , 15A , 17A ) (vs hepatic lobe remarkably less developed than the branchial lobe, Fig. 15B ); 3) branchial lobe distinctly cut, broad triangular ( Figs. 14A, C, E , 15A , 17A ) (vs branchial lobe poorly cut, rather coalescent with the margins of the carapace, Fig. 15B ); 4) carapace lateral margin between the hepatic and branchial lobes deeply concave in dorsal view outline ( Figs. 14A, C, E , 15A , 17A ) (vs margin between the hepatic and branchial lobes nearly straight or shallowly concave at most in dorsal view outline, Fig. 15B ); 5) postorbital notch deeply and roundly incised ( Figs. 14A, C, E , 15A , 17A ) (vs postorbital notch very narrow and inconspicuous, Fig. 15B ); 6) cheliped fingers deeply spoon-shaped, each finger provided with many long stiff setae along near cutting edge intermingled with each other when closed ( Fig. 15G ) (vs cheliped fingers spoon-shaped but each finger with only a subdistal tuft of stiff setae, Fig. 15I ); 7) cheliped dactylus rather massive, remarkably short, strongly curved downward and inward ( Fig. 15E, G ) (vs cheliped dactylus much less massive, gently curved downward and inward, Fig. 15F, I ); 8) cheliped carpus devoid of dorsal tubercles with a granular bump at most ( Fig. 15C ) (vs cheliped carpus with two granular tubercles dorsally, Fig. 15D ); 9) cheliped merus with two small tubercles on dorsal surface ( Fig. 15E ) (vs such tubercles absent, Fig. 15F ); 10) P5 merus length (measured along dorsal margin) distinctly less than two times merus maximum width ( Fig. 15J ) (vs P5 merus length much more than two times merus maximum width, Fig. 15L ). Epialtus parvulus sp. nov. ( Fig. 16A–E ) also strongly differs from E. bituberculatus ( Fig. 16F, G ) and from E. brasiliensis Dana, 1852a ( Fig. 16H, I ), in the shape of the first male gonopod.

Epialtus parvulus sp. nov. ( Figs. 14A–E , 15A, C, E, G, H, J, K ) is superficially similar to E. longirostris , in that the hepatic and branchial lobes are distinctly cut and broad triangular, the carapace is usually slightly narrower across the hepatic region than across the branchial region, and the supraorbital notch is deeply and roundly incised. However, in the new species the rostrum is remarkably shorter and broad triangular, whereas E. longirostris has remarkably longer and slender rostrum with subparallel sides and slightly arcuate tip in dorsal view ( Figs. 18A–F ).

Rathbun (1923) established E. portoricensis Rathbun, 1923 (as E. longirostris forma portoricensis ), which differed from E. longirostris Stimpson, 1860 only in having a slightly wider and thick rostrum, with arcuate tip in dorsal view ( Fig. 18D ). Carmona-Suárez & Poupin (2016) examined 2 specimens from Guadeloupe, one of which was assigned to E. longirostris while the other provisionally referred to E. portoricensis . However, they cautioned that the differences between E. longirostris and E. portoricensis being very subtle, the latter seems to fall into the variation of the former. We have reexamined all the specimens assigned by Rathbun (1923, 1925) to E. longirostris (2 specimens) and E. portoricensis (1 specimen), as well as 6 additional specimens previously referred to E. longirostris (see above under comparative material). The criteria used by Rathbun (1923, 1925) to distinguish between the two species are no greater than the variations between the 3 specimens from Puerto Rico, nor are they greater than the variations between the specimens of E. longirostris from different localities. In the male holotype of E. portoricensis ( Fig. 18D ), for instance, the rostrum has subparallel sides and the tip is slightly arcuate and inconspicuously bifid in dorsal view, whereas in the female USNM 1462844 also from Puerto Rico ( Fig. 18F ), the sides of the rostrum are distinctly concave and the tip markedly arcuate, but not bifid. The juvenile USNM 75097 from Puerto Rico ( Fig. 18E ), has a slightly thicker rostrum with subparallel sides and truncate tip. In E. longirostris , the male USNM 88670 from the Bahamas ( Fig. 18A ), and the female USNM 43019 from Jamaica (previously assigned to E. longirostris by Rathbun 1925) ( Fig. 18C ), both have the rostrum with subparallel sides with very slightly arcuate tip in dorsal view, but in the specimen from the Bahamas the rostrum is distinctly wider. In view of the variations encountered, even in specimens from the same locality and in the absence of distinguishing characters other than those subtle ones submitted by Rathbun (1923; 1925), and considering that the type localities of E. longirostris (St. Thomas) and E. portoricensis ( Puerto Rico) are very close to each other with some islands in between, we regard both species as synonymous, E. longirostris having the priority.

Figures

FIGURE 14. A–E, Epialtus parvulus sp. nov. A, B, Holotype male, cl 6.4 mm, cw 5.1 mm (MZUSP 40577). C, D, Ovigerous female, paratype, cl 6.5 mm, cw 5.6 mm (MZUSP 39678). E, Juvenile female, paratype, cl 3.8 mm, cw 2.9 mm (MZUSP 39679). F, Trindade Island, Ponta Noroeste, 9.4 m, one of the collection sites of Epialtus parvulus sp. nov. Photographs (C, D)

FIGURE 15. A, C, E, G, H, J, K, M, Epialtus parvulus sp. nov., holotype male, cl 6.4 mm, cw 5.1 mm (MZUSP 40577). B, D, F, I, L, Epialtus bituberculatus H. Milne Edwards, 1834, male, cl 8.5 mm, cw 6.5 mm (MZUSP 32450). A, B, Dorsal aspect of the carapace outline. C, D, Dorsal aspect of the right cheliped carpus. Note in (D) two granular tubercles. E, F, Right cheliped dactylus and propodus, lateral view. Note in (E) the much longer propodus with two small tubercles on the dorsal surface. G, I, Right cheliped fingers deeply spoon-shaped, mesial view. Note in (G) fingers provided with many long stiff setae along near cutting edge and in (I) fingers with only a subdistal tuft of stiff setae. J, L, Right fifth pereopod, lateral view. Note in (J) merus length (measured along dorsal margin) distinctly less than two times merus maximum width (merus length much more than two times merus maximum width in L). H, K, M, Dorsal aspect of the pleonal somites. Scales: 1 mm.

FIGURE 16. A–I, Differencial interference contrast images of the first male gonopod in sternal (A–C, F–I) and pleonal (D, E) views. A–E, Epialtus parvulus sp. nov., holotype male, cl 6.4 mm, cw 5.1 mm (MZUSP 40577). F, G, Epialtus bituberculatus H. Milne Edwards, 1834, male, cl 6 mm, cw 7.5 mm (MZUSP 22660). H, I, Epialtus brasiliensis Dana, 1852, male, cl 5.9 mm, cw 4.5 mm (MZUSP 41772). Scales: 0.1 mm.

FIGURE 17. A–E, Epialtus parvulus sp. nov. A, B, Ovigerous female paratype, cl 6.5 mm, cw 5.6 mm (MZUSP 39678). C–E, Ovigerous female paratype, cl 6.4 mm, cw 5.5 mm (MZUSP 33814). A, B, Carapace outline, dorsal and anteroventral views, respectively. C, Third pereopod, lateral view. D, E, Second pereopod, mesial view. Scales: A, B, 1 mm. C–E, 1 mm.

FIGURE 18. A–F, Epialtus longirostris Sitmpson, 1860, dorsal aspect of the carapace. A, Bahamas, male, cl 4.5 mm, cw 3.0 mm (USNM 88670). B, Cuba, male, cl 7.5 mm, cw 5.5 mm (USNM 48742). C, Jamaica, female, cl 6.5 mm, cw 4.5 mm (USNM 43019). D, Porto Rico, male, cl 5.4 mm, cw 3.7 mm (holotype of E. longirostris portoricensis Rathbun, 1923) (USNM 24154).