Pohleus, Colavite & Windsor & Santana, 2020

Colavite, Jessica, Windsor, Amanda M. & Santana, William, 2020, A new genus for Pericera septemspinosa Stimpson, 1871 and Pericera heptacantha Bell, 1836 (Crustacea, Brachyura, Majoidea), based on morphology and molecular data, Zoosystematics and Evolution 96 (1), pp. 205-216 : 205

Pohleus gen. nov.

Type species.

Pericera septemspinosa Stimpson, 1871, by present designation.

Included species.

Pohleus septemspinosus (Stimpson, 1871) gen. nov. et comb. nov. and Pohleus heptacanthus (Bell, 1836) gen. nov. et comb. nov.

Diagnosis.

Carapace subglobose, covered by short velvet pubescence interspaced by dense rows of long, hooked and simple setae in all carapace regions. Carapace armed with strong spines, including seven sharp spines on posterior half: one short mesial metagastric, four long, strong, conical lateral spines (two in each branchial region) aligned with one cardiac spine and one intestinal spine; lateral spines longest, slightly directed upwards. Pterygostomial region with strong spines visible in dorsal view. Rostrum bifurcated, base elongated, fused, diverging abruptly forming a Y-shape, ending in acute tips. Pre-orbital spine strong, acute, directed upwards; post-orbital spine short, acute. Basal article of antenna with three spines, one tubercle, not visible in dorsal view. Cheliped long, merus armed with short spines or tubercles, granulated. P2 shorter than cheliped, dactylus much shorter than propodus. Thoracic sternal somite IV with lateral margins straight. Sternite VIII concealed by pleon in males. Male and female pleon with six somites not fused plus telson. Male telson tight-fitting into sterno-pleonal cavity, distinctly triangular. G1 slender, straight, with bilobed apex. G2 slender, straight, tapering distally, short about one fifth of G1 length.

Comparative material.

Libinia spinosa H. Milne Edwards, 1834 - Brazil • 1 male, 1 female; Macaé, near Santana Archipelago, PITA stn 12 III (MZUSP 20271). Macrocoeloma camptocerum (Stimpson,1871) - USA • 13 males, 7 females, 7 ovig. females; Sanibel Island, 26.440359N, 82.113705W, 0.54-11 m depth; Mar 1938; F A Chace Jr. leg. det. (MCZ 10191). Macrocoeloma concavum Miers, 1886 - Venezuela • 1 female; Costa de Falcon, UTM 378365 and 1358259; 27 Apr 2007 (GIC040). Brazil • 1 male; Paraíba, Projeto Algas, stn 85-B; 04 Jun 1981; Apr 2008, L E A Bezerra det. (MZUSP 5937). Macrocoeloma diplacanthum (Stimpson, 1860) - US Virgin Islands • 1 male; Saint Thomas, R/V Albatross; 17-24 Jan 1884 (USNM 16182). Guadeloupe • 1 ovig. female; 16°13'37.3188"N, 61°32'23.0388"W, Karubenthos 2012, stn GD49; 21 May 2012 (MNHN IU-2013-6755). Macrocoeloma eutheca . (Stimpson,1871) - USA • 1 ovig. female; off North Carolina, 33°48'06"N, 76°34'42"W, 77 m depth; 03 Apr 1981; Duke University for MMS 0S05 exped., 1981, P Krikorian det. (USNM 220812). Macrocoeloma intermedium Rathbun, 1901 - Cuba • male holotype; off Havana, R/V Albatross, stn 2323, 23°10'51"N, 82°19'03"W, 298 m depth; 17 Jan 1885; M J Rathbun det. (USNM 9492). Colombia • 1 female; Santa Marta; 29 Jun 1975; M Vélez det. (SMF 9093). Macrocoeloma laevigatum (Stimpson, 1860) - USA • 1 male; Florida, Hawk Channel, R/V Fish Hawk, stn 7429, 4.2 m depth; 27 Jan 1903 (USNM 46933). Bahamas • 1 female; off Whale Cay, 23.7 m depth, 9 Jul 1904, F A Chace Jr. det. (MCZ 8927). Macrocoeloma maccullochae Garth, 1940 - Mexico • 1 male, 1 female; Isabel Island, Allan Hancock Pacific exped., R/V Velero III, stn 747-37, 18-32 m depth; 2 Apr 1937; W Schmitt leg., 1940; J S Garth det. (NHMLAC-AHF 372). Macrocoeloma nodipes (Desbonne in Desbonne & Schramm, 1867) - USA• 3 males, 2 females; Florida, Off Cape Sable, R/V Fish Hawk, stn 7351, 25°09'45"N, 81°18'35"W, 17 Dec 1902, 5.9 m depth (USNM 46922). Grenada • 1 male; Grand Anse Bay, 12°01'45.19"N, 61°45'21.29"W, 11 Nov 2012, L R L Simone, A P Dornellas, V S Amaral leg., 27 Nov 2019, J Colavite det. (MZUSP 40162). Macrocoeloma subparallelum (Stimpson, 1860) - US Virgin Islands • male lectotype; soft shell, cl. 13.98 mm, cw. 9.90 mm; St. Thomas, 18.345591N, 64.923613W, no date, A H Riise leg., 1860, W Stimpson det. (MCZ 1243). Brazil • 3 females; Porto da Barra, Salvador, left side, 24 Apr 2006, R Bispo, R Jhonsson, W Santana, F Faria leg., Apr 2008, G Melo det. (MZUSP 18626). Macrocoeloma trispinosum (Latreille, 1825) - USA • 1 ovig. female; Kingston Harbour; 1893; R P Bigelow leg., M J Rathbun det. (USNM 17959). Antigua • 1 male; English Harbour, Antigua-Barbados exped., 1918; University of Iowa State exped., M J Rathbun det. (USNM 72956). Macrocoeloma villosum (Bell, 1836) - Ecuador • 3 males, 1 female; Salinas, Walter Rathbone Bacon travelling Scholarship exped., stn 1, 2, 3; 12-14 Sep 1926; W L Schmitt leg., M J Rathbun det. (USNM 70942). Thersandrus compressus (Desbonne in Desbonne & Schramm, 1867) - Belize • 1 male; west Bay, 1.3 m depth; 09 Jun 1985 (USNM 1526077).

Remarks.

Macrocoeloma Miers, 1879 s. str. is an amphi-American genus with 12 species. This genus is characterised by the pyriform or triangular carapace, densely covered by short, velvet-like setae; with well-developed bifurcated or parallel rostral spines; the eyes completely protected by the orbits when retracted; orbits composed by the pre-orbital and the post-orbital spines and one or two projections of the basal article of antenna forming a functional, laterally projected protective hood. Although some of these characters can be observed in Pohleus gen. nov., the new genus can be easily distinguished from Macrocoeloma s. str. by a unique combination of characters, which include: (i) carapace relatively more globose in Pohleus gen. nov. (Figs 2A-C , 3 , 4 ) (vs. carapace subtriangular or pyriform in Macrocoeloma ; Fig. 2E, F ); (ii) carapace covered by short velvet pubescence interspaced by dense rows of long hooked and simple setae in all carapace regions in Pohleus gen. nov. (Fig. 2C ) (vs. carapace densely covered by velvet pubescence with hooked setae in specific regions of the carapace in Macrocoeloma ); (iii) basal article of antenna with small spines ventrally directed, not visible in dorsal view in Pohleus gen. nov. (Fig. 2B ) (vs. with a long laterally-directed spine, between the rostral and pre-orbital spine, visible in dorsal view of Macrocoeloma , except in Macrocoeloma diplacanthum ; Fig. 2F ); (iv) pterygostomial region with a strong spine, laterally projected, visible in dorsal view in Pohleus gen. nov. (Fig. 2B ) (vs. pterygostomial spines short, reduced or not visible in dorsal view in Macrocoeloma ; Fig. 2F ); (v) male sterno-pleonal cavity with no crest anteriorly in Pohleus gen. nov. (Fig. 2B ); (vs. male sterno-pleonal cavity with a distinct crest anteriorly on thoracic sternite IV in Macrocoeloma ; Fig. 2E ); (vi) male sternite IV almost straight laterally in Pohleus gen. nov. (Fig. 2B ) (vs. sternite IV deeply concave laterally in Macrocoeloma ; Fig. 2E ); (vii) episternites IV and V forming a continuous line with the sternite, slightly downward directed in Pohleus gen. nov. (Fig. 2B ) (vs. episternites IV, V and VI upward directed in Macrocoeloma ; Fig. 2F ); and (viii) sternal sutures shallow in Pohleus gen. nov. (Fig. 2B ) (vs. sternal sutures deep sculpted in Macrocoeloma ; Fig. 2F ).

In Macrocoeloma , the gonopods are highly variable amongst species, but it is possible to recognise a general pattern with G1 being longer than the thoracic sternal suture IV/V, parallel and usually with a bilobed apex (except in M. concavum , M. intermedium and M. laevigatum that have a unilobed apex). Although Pohleus septemspinosus gen. nov. et comb. nov. (G1 of Pohleus heptacanthus gen. nov. et comb. nov. not examined) can be fitted in this general pattern, the G1 apex is notably more similar to the G1 apex of Libinia Leach, 1815 (Fig. 2D and see Tavares and Santana 2011: 63, fig. 2D for Libinia spinosa ).

Thersandrus Rathbun, 1897, is a monotypic genus exhibiting extremely efficient camouflage behaviour as Macrocoeloma and Pohleus gen. nov. However, Thersandrus does not actively decorate itself, presenting crypsis behaviour consisting of matching the body to the environment in shape and colour, being morphologically adapted to live on green algae fronds. For instance: (i) Thersandrus has a carapace covered by long setae giving a felt-like texture (vs. velvet-like and hooked setae in Macrocoeloma and Pohleus gen. nov.); (ii) the carapace and pereopods are flattened in Thersandrus (vs. carapace subtriangular or piriform, not flattened and with cylindrical pereopods in Macrocoeloma and subglobose carapace and cylindrical pereopods in Pohleus gen. nov.); (iii) the orbital spines are reduced, not forming a hood in Thersandrus (vs. orbital spines long, blunt, forming a hood in Macrocoeloma and long, acute and forming a hood in Pohleus gen. nov.); all characters that prevented us from synonymising Thersandrus to Macrocoeloma . However, it is important to note that, based on the molecular results, Thersandrus should be transferred from Majidae to Pisinae as mentioned above.

Etymology.

Generic name in honour of the renowned marine biologist and carcinologist Gerhard Werner Pohle (Atlantic Reference Centre, Huntsman Marine Science Centre). Gender masculine.

Figures

Figure 2. Pohleus septemspinosus (Stimpson, 1871) gen. nov. et comb. nov. A, B. male, (USNM 1256361); C. male (USNM 241030); D. sterno-pleonal cavity with first (G 1) and second (G 2) gonopods in place (USNM 1256361). Macrocoeloma trispinosum (Latreille, 1825); E, F. male (USNM 17959). A, E. habitus; B, F. ventral view; C. frontal view; D. pleonal view in detail. Note the spine of the basal article of antenna (white arrow); pterygostomial spine (grey arrow); margin of the IV sternite thoracic (black arrow). Scale bars: 10 mm.

Figure 3. A. Habitus, dorsal view and B. ventral view of Pohleus septemspinosus (Stimpson, 1871) gen. nov. et comb. nov., female (R 2 unnumbered). Colour in life with debris and algae for camouflage. Scale bars: 10 mm

Figure 4. Geographic distribution Pohleus heptacanthus (Bell, 1836) gen. nov. et comb. nov.; orange circles = distribution based on examined material; green star = type locality and Pohleus septemspinosus (Stimpson, 1871) gen. nov. et comb. nov.; red circles = distribution based on examined material; yellow star = neotype locality.