Amphithrax verrucosus (H. Milne Edwards, 1832)

Parasram, Nadeshinie, Santana, William, Valles, Yvonne, Windsor, Amanda M. & Valles, Henri, 2024, Morphological and molecular support for Amphithrax verrucosus (H. Milne Edwards, 1832) and Amphithrax aculeatus (Herbst, 1790) (Crustacea, Decapoda, Brachyura) as valid species, Zoosystematics and Evolution 100 (1), pp. 15-30 : 15

Amphithrax verrucosus (H. Milne Edwards, 1832)

Figs 2B , 4A-D , 5B , 6E-H

Mithrax verrucosus H. Milne Edwards, 1832: 11, pl. 4 [type-locality: Martinique; type probably in MNHN]. - Schomburgk 1848: 65; Stimpson 1860: 187; Desbonne and Schramm 1867: 6; A. Milne-Edwards 1875: 102; Miers 1886: 86; Rathbun 1897: 9; 1921: 83; 1924: 20; Nutting 1919: 77; Rodriguez 1980: 287; Abele and Kim 1986: 47, 524 fig. c, d; Wagner 1990: 29-32, figs 32-35; Melo 1996: 239, unnumbered fig.; Ng et al. 2008: 120; Alves et al. 2012: 943, fig. 3C; Carmona-Suárez and Poupin 2016: 373, fig. 6I.

Mithrax verrucosus variety - Rathbun 1898: 259.

Mithrax (Mithrax) verrucosus - Young 1900: 93; Rathbun 1925: 400, pl. 144; 1933: 30; Boone 1927: 39; Williams 1965: 255, figs 235, 245B; 1984: 336, figs 271, 275c; Coelho and Ramos 1972: 215; Collins and Morris 1976: 119, pl. 17, fig. 7, pl. 18, figs 5-7; Powers 1977: 58; Keith 1985: 259, fig. 5E.

Mithrax plumosus Rathbun, 1901: 67 [type-locality: Puerto Real, Puerto Rico; holotype in USNM 23775].

Amphithrax aculeatus - Assugeni et al. 2017: 1630, tab. 1; Mantelatto et al. 2020: 39; Lianos et al. 2021: 1-19, figs 1, 11; Ortiz 2022: 34, fig. 14C (not Cancer aculeatus Herbst, 1790).

Amphithrax verrucosus - Poupin 2018: 193, fig. 211; Questel 2019: 16, unnumbered figure; Parasram et al. 2023: 21, fig. 9D.

Material examined

. Type material. Holotype of Mithrax plumosus Rathbun, 1901: Puerto Rico, Port Real, Vieques, Fish Hawk Expedition • 1 ovig., ♀ (CW: 37.0 mm; CL: 29.0 mm) (USNM 23775), 18°7'29.8956"N, 65°26'31.6428"W.

Additional material.

USA, Florida, Big Pine Key • 3 ♂♂, 3 ♀♀, 3 ovig. ♀♀ (USNM 14030), 24°40'11.514"N, 81°21'14.2884"W . Florida • 8 ♂♂, 3 ovig. ♀♀ (MCZ 353), 27°59'39.8472"N, 81°45'36.9144"W . Idem , 1 ♂, 1 juv. ♀ (MCZ unnumbered), 27°59'39.8472"N, 81°45'36.9144"W . Idem , 1 juv. ♀ (CW: 34.0 mm; CL: 20.0 mm) (ULLZ 4534), 27°59'39.8472"N, 81°45'36.9144"W . Idem , 1 ♂ (ULLZ 13956), 27°59'39.8472"N, 81°45'36.9144"W . Idem , Florida Keys • 1 ovig. ♀ (CW: 56.0 mm; CL: 42.0 mm) (ULLZ 15294), 24°41'29.0472"N, 81°11'22.8552"W . Idem, Big Pine Key • 1 ♂ (ULLZ 11924), 24°40'11.514"N, 81°21'14.2884"W . Idem, Loggerhead Key • 1 ♂ (CW: 67.0 mm; CL: 53.0 mm) (ULLZ 11736), 24°63'23.745"N, 82°92'06.767" W. Idem, Dry Tortugas • 1 ♂ (USNM 69068), 24°62'82"N, 82°87'32"W . Belize, Carrie Bow Cay Reef • 1 ♂ (CW: 10.0 mm; CL: 8.0 mm) (ULLZ 9148), 17°29'51.77"N, 88°11'11.95"W . Honduras, Swan Island • 1 ♂ (USNM 15074) . Guadeloupe, Pointe Baham , MADIBENTHOS • 1 ♂ (MNHN-IU-2016-10018), 14°24'42.9984"N, 60°50'4.9956"W . Martinique, Point Jacob , MADIBENTHOS • 1 ♀ (MNHN-IU-2017-10364), 14°36'8.0028"N, 60°48'57.996"W . Barbados, Palm Court , St. Michael • 1 ♀ (CW: 31.6 mm; CL: 24.0 mm) (BLSZ 225). Idem , 1 ovig. ♀ (CW: 26.2 mm; CL: 22.0 mm) (BLSZ 227), nearshore rubble, 13°04'30.73"N, 59°36'12.49"W . Idem , 1 ♂ (CW: 26.7 mm; CL: 22.0 mm) (BLSZ 228). Idem, 1 ♀ (CW: 31.4 mm; CL: 24.5 mm) (BLSZ 328). Idem, 1 juv. ♀ (CW: 12.4 mm; CL: 12.0 mm) (BLSZ 332). Idem, 1 ♂ (CW: 24.5 mm; CL: 23.0 mm) (BLSZ 229). Idem, 1 ♀ (CW: 30.2 mm; CL: 25.6 mm) (BLSZ 251). Idem, 1 ♂ (CW: 21.1 mm; CL: 18.2 mm) (BLSZ 226). Drill Hall , St. Michael • 3 ♀, 1 ♂ (CW: 27.1; 11.3; 5.3 mm; CL: 22.0; 12.5; 6.0) (BLSZ 123), nearshore rubble, 13°04'36.30"N, 59°36'26.63"W . Idem, 1 ♀ ovig., (CW: 26.4 mm; CL: 27.5 mm) (BLSZ 266). Idem, 1 ♂ (CW: 27.2 mm; CL: 22.0 mm) (BLSZ 265). Idem , 1 ♂ (CW: 35.1 mm; CL: 27.4 mm) (BLSZ 250). Idem , 1 ovig., ♀ (CW: 31.6 mm; CL: 25.7 mm) (BLSZ 249). Idem , 12 ♂♂, 3 ♀♀, 2 juv., ♀♀ (CW: 7.5 mm; 14.3 mm; 16.6 mm; 22.0 mm; 14.2 mm; 13.6 mm; 23.5 mm; 8.5 mm; 22.0 mm; 15.2 mm; 15.0 mm; 20.3 mm; 24.0 mm; 25.7 mm; 17.4 mm; 20.0 mm; 15.0 mm; CL: 7.0 mm; 13.1 mm; 15.0 mm; 18.4 mm; 12.6 mm; 12.7 mm; 19.1 mm; 7.0 mm; 19.0 mm; 14.8 mm; 14.0 mm; 17.0 mm; 20.0 mm; 21.0 mm; 20.5 mm; 17.0 mm; 13.6 mm) (BLSZ 278). Batts Rock , St. Michael • 1 ♂ (CW: 26.7 mm; CL: 21.5 mm) (BLSZ 165) subtidal, 13°08'04.81"N, 59°38'12.30"W . Idem , 1 ♂ (CW: 40.5 mm; CL not taken) (MZUSP 40921). Coconut Court , Christ Church • 2 ♂♂, 1 ♀, 1 ovig., ♀ (CW: 16.7 mm; 6.0 mm; 15.5 mm; 20.0 mm; CL: 15.5 mm; 6.4 mm; 14.7 mm; 22.8 mm) (BLSZ 211), nearshore rubble, 13°04'31.59"N, 59°36'13.78"W . Trinidad and Tobago, Chacachacare, Rusts Bay • 1 ♂ (CW: 42.0 mm; CL: 33.0 mm) (USNM 137759), 10°40'59.99"N, 61°44'59.99"W . Venezuela, Isla de Coche, Bajo Culebra • 2 ♀♀, 3 ♂♂ (GIC 072), 10°46'21.59"N, 63°56'24.59"W . Idem , 1 ♂ (LSZ 012), 10°46'21.59"N, 63°56'24.59"W . Isla de Cubagua • 1 ♂, 1 ♀ (LSZ 012), 10°49'4.79"N, 64°10'34.20"W . Brazil, Rio Grande do Norte, Atoll das Rocas • 1 ♂ (MZUSP 15323), 3°51'59.99"N, 33°48'59.99"W . Idem , 1 ♂ (MZUSP 24761), 3°51'59.99"N, 33°48'59.99"W . Idem , 2 ♂ (MNRJ 15609), 3°51'59.99"N, 33°48'59.99"W . Idem , 3 ♂♂, 1 ovig., ♀ (MNRJ 4782), 3°51'59.99"N, 33°48'59.99"W . São Paulo, Ilha Vitoria • 3 ♂♂ (MZUSP 16708), 20°19'9.98"N, 40°20'16.01"W .

Diagnosis.

Dorsal surface of carapace uniformly covered with closely-set granules of irregular size; there are a few blunt tubercles on the gastric, branchial and cardiac regions; spines are only present in the lateral margins. In fully developed males chelipeds massive, carpus dorsally smooth with few blunt, short tubercles dorsolaterally in some specimens, strong teeth on inner margins and the palm of the cheliped is smooth. Propodi of pereopods are without spines, but have the presence of long and short dark setae. Carapace is predominantly maroon in colour.

Remarks.

Much of the ambiguity surrounding A. aculeatus and A. verrucosus originated when Rathbun described Mithrax pilosus and M. plumosus ( Rathbun 1892, 1901; Fig. 5B, C ). These descriptions were based on small specimens, which naturally appear more similar than their fully matured counterparts. Additionally, Windsor and Felder (2014) based their decision on very small juvenile specimens, mistakenly identified as A. aculeatus (see Suppl. material 2 in supplementary material and phylogenetic section of this work). Despite the similarities observed in younger specimens, the distinct morphological characteristics presented should suffice to prevent any further confusion between the two species.

The G1 of A. verrucosus was described in detail by Lianos et al. (2021) under the name A. aculeatus and by Wagner (1990) as Mithrax verrucosus (see also remark section for A. aculeatus ).

Ontogenetic intraspecific variations in A. verrucosus from juveniles to adults are: juvenile specimens have short and long setae that are evenly distributed on the carapace, cheliped and third maxillipeds, while adults have much less setae or are devoid of setae in these regions. Some very small specimens may have few spines on the carapace, especially on branchial regions. Anterolateral margins with six to eight spines on juveniles, whereas adults have eight spines. Younger specimens and females with strong short spines dorsally on the carpus of the cheliped, which are not present in fully developed adults, remaining only inner carpal spines. The carapace spines on the branchial region, along with the spines dorsally on carpus in young specimens may have led some authors to confuse A. verrucosus with A. aculeatus . It is important to note that even in very small specimens, the palm of the cheliped and the propodus of pereopods in A. verrucosus lack spines. Amphithrax verrucosus is very abundant in Barbados as well and specimens were collected by hand and with caged crab traps on the west and south coasts of Barbados. Parasram et al. (2023), reported Amphithrax verrucosus as being found in close association with A. aculeatus , Mithraculus coryphe (Herbst, 1801), Mithraculus forceps A. Milne-Edwards, 1875, Eriphia gonagra (Fabricius, 1781) and Pachygrapsus transversus (Gibbes, 1850). Females of this species are generally smaller than males (see materials examined). Ovigerous females were collected in June and September 2021.

Colouration.

Colour in life for A. verrucosus is carapace predominantly maroon and maroon mixed with white spots on ventral surface. Some specimens are more brownish, with light spots on the carapace (MNHN-IU-2016-10018) and some adult females have a light brown carapace (MNHN-IU-2017-10364). The chelipeds range from a dark maroon, greenish-brown to a lighter brown hue; in ventral view, only the tip of the fingers is whitish (Figs 4A , 6 E-H ) (see also fig. 3G of Windsor and Felder (2014).

Distribution.

Western Atlantic: USA (South Carolina to Florida), Gulf of Mexico, Cuba, Jamaica, Puerto Rico, Virgin Islands, St. Maarten, Honduras, Antigua, Belize, Guadeloupe, Isla de Aves, Martinique, Barbados, Grenada, Trinidad and Tobago, Bonaire, Curaçao, Aruba, Colombia, Venezuela, and Brazil, from Fernando de Noronha to São Paulo ( Rathbun 1925; Carmona-Suárez and Poupin 2016; Poupin 2018; present study).

Figures

Figure 2. A. BI molecular phylogenetic tree for Amphithrax verrucosus, A. aculeatus and other selected species within the family Mithracidae MacLeay, 1838. Based on GTR + G nucleotide substitution model on the concatenated dataset for two mitochondrial (12 S, 16 S) and one nuclear (ITS- 1) genes, represented as a maximum likelihood phylogram with Bayesian posterior probabilities and maximum likelihood bootstrap values (black diamond = ≤ 50 % support, * = 16 S sequences only). Note: ULLZ's 9148 and 4534, of Windsor and Felder (2014) and 13596 all re-identified as Amphithrax verrucosus (H. Milne Edwards, 1832); B. Amphithrax verrucosus (H. Milne Edwards, 1832), male (CW: 40.7 mm; CL: 29.5 mm), Barbados (BLSZ 218); C. Amphithrax aculeatus (Herbst, 1790), juvenile female (CW: 53.8 mm; CL: 44.0 mm), Barbados (BLSZ 217).

Figure 4. Amphithrax verrucosus (H. Milne Edwards, 1832) adult male (BLSZ 218). A. Habitus, dorsal; B. Ventral view, locality: Barbados; C. Pleonal view of left G 1 (BLSZ 228); D. Distal third of left G 1. Scale bars: 20 mm (A, B); 10 mm (C). Photos: Nadeshinie Parasram.

Figure 5. Type specimens. A. Paralectotype of Cancer aculeatus, Herbst, 1790, dry preserved carapace without setae and with most of the spines broken (ZMB Herbst 79), locality: Antilles; B. Holotype of Mithrax plumosus Rathbun, 1901 (USNM 23775), ovig. female (CW: 37.0 mm; CL: 29.0 mm), locality: Puerto Rico; C. Holotype of Mithrax pilosus Rathbun, 1892, setae on carapace removed (USNM 16299), male (CW: 30.0 mm; CL: 28.0 mm), locality: Bahamas; D. Distal third of the right G 1 of the holotype of Mithrax pilosus (USNM 16299) in pleonal view. Photos: A Kristina von Rintelen. B, C, D Amanda Windsor.

Figure 6. Colour in life. Young female of Amphithrax aculeatus (Herbst, 1790) (BLSZ 217), Barbados. A. Habitus dorsal view; B. Ventral view. Adult male of Amphithrax aculeatus (Herbst, 1790) (MNHN-IU- 2013 - 5929), Guadeloupe; C. Habitus, dorsal view; D. Ventral view. Adult male of Amphithrax verrucosus (H. Milne Edwards, 1832) (GIC 072), Venezuela; E. Habitus, dorsal view; F. Ventral view. Female of Amphithrax verrucosus (H. Milne Edwards, 1832) (BLSZ 328), Barbados; G. Habitus, dorsal view; H. Ventral view. Scale bars: 20 mm. Photos: A, B, G, H. Nadeshinie Parasram. C, D. Joseph Poupin. E, F. William Santana.