Tubicolixa, Theil & Felder, 2020

Theil, Emma Palacios & Felder, Darryl L., 2020, Phylogeny of the genus Pinnixa White, 1846 (Crustacea, Brachyura, Pinnotheridae) and allies inferred from mitochondrial and nuclear molecular markers, with generic reassignment of twenty-one species, Zoosystema 42 (6), pp. 85-103 : 99-101

Genus Tubicolixa n. gen.

urn:lsid:zoobank.org:act:00ADBC20-FD16-4594-B5FB-A7DE037E3E8F

TYPE SPECIES. — Tubicolixa chaetopterana (Stimpson, 1860) n. comb. [ Pinnixa ].

DIAGNOSIS. — Carapace uneven, regions clearly limited by depressions, some surfaces heavily pubescent, especially margins; cardiac region with transverse crest, not extending entirely across carapace; branchial regions with granulate or serrated edges. Third maxilliped with ischiomerus subtrapezoidal; propodus and dactylus longer than carpus, shorter than ischiomerus, elongate; dactylus inserting near base of propodus, reaching beyond end of propodus. Chelipeds strongly developed, setose, with shortened or deflexed fixed finger, in some cases sexual dimorphism. First two ambulatory legs (P2 and P3) slender, third and fourth (P4 and P5) stouter; relative lengths P4> P3> P2> P5. Male pleon tapering toward end, telson subsemicircular; first pleonal somite lacking gonopodal plate between gonopods.

ETYMOLOGY. — Named Tubicolixa in recognition of the group apparent preference for polychaete tubes as a habitat. Gender feminine.

ADDITIONAL SPECIES. — Tubicolixa brevipollex ( Rathbun, 1898) n. comb. [ Pinnixa ];

Tubicolixa rapax (Bouvier, 1917) n. comb. [ Pinnixa ].

MATERIAL EXAMINED. — In addition to the material included in the phylogenetic analyses ( Table 1 ) the following material was available for examination:

Tubicolixa chaetopterana n. comb. — ULLZ 12480 (Beaufort, NC, USA) , ULLZ 4452 (2), ULLZ 4561 (2), ULLZ 5553 (2), ULLZ 6429 , ULLZ 7395 , ULLZ 7400 , ULLZ 10286 , ULLZ 14005 (2), ULLZ 14008 (6), ULLZ 14110 , ULLZ 14907 (4), ULLZ 14911 , ULLZ 17925 (Fort Pierce, FL, USA) , ULLZ 14916 (Peanut Is, FL, USA) , ULLZ 5542 (7) (Florida Keys, USA) , MNHN-IU-2017-9370, ULLZ 17456 (2) (Tampa Bay, FL, USA) , ULLZ 14080 (2) (St. Mark’s lighthouse, FL, USA) , ULLZ 14996 , ULLZ 14997 (2) (St. Joseph’s State Park, FL, USA) , ULLZ 8638 (2), ULLZ 14875 (3) (St. Andrew’s Bay, FL, USA) , ULLZ 14024 (2) (Perdido Key Beach, FL, USA) , ULLZ 8657 (7) (offshore Mississippi, USA) , ULLZ 5552 (2) (Isles Dernieres, LA, USA) , ULLZ 14832 ( Bryan Mound , TX) , ULLZ 2597 (3) (Padre Island, TX, USA) .

Tubicolixa rapax n. comb. — ULLZ 14115 (Ubatuba, Brazil) .

REMARKS

Genetic and morphological differences between specimens of T. chaetopterana (Stimpson, 1860) n. comb. from Venezuela and

Belize and those from the Gulf of Mexico and North Atlantic coasts at minimum suggest population structure within this species. This taxon may represent a species complex, similar to that observed for some of the species of Scleroplax , with different morphotypes at the species and/or population level likely adapted to different habitats and/or hosts. However, most preserved samples available to us at present do not represent sequence quality materials. Additional studies with larger and more broadly representative sample sizes based on markers with resolution at the population level should be undertaken, along with more detailed collection information regarding habitat and hosts. Additional samples of T. chaetopterana n. comb. from Belize should further clarify the identification of that juvenile specimen, once at least a 12S sequence for can be obtained.

The holotypes of Pinnixa brevipollex Rathbun, 1898 ( USNM 21593 , near La Plata estuary, Argentina) and Pinnixa rapax Bouvier, 1917 ( MCZ 10997 , Gulf of San Matías, Argentina) require further study and comparison, along with molecular and morphological studies based on contemporary samples representing their putatively separate populations. These species have been suggested to be synonyms, but the holotypes remain to be compared ( Fenucci 1975; Bezerra et al. 2006). Some authors suggest there are differences in the male pleon ( Righi 1967), but the allegedly junior synonym P. rapax is still considered a valid species ( Ng et al. 2008). This group may represent yet another species complex, and we elect to for now continue their treatment as separate taxa.