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A new genus and species of xanthoid crab (Decapoda: Brachyura) from offshore hard bank habitats in the Gulf of Mexico
Speciose populations of small xanthoid crabs on offshore banks and reefs of the northern Gulf of Mexico include a new species that is not assignable to presently named genera. Morphological diagnoses of the new genus and species are underpinned by previously published gene sequence analyses, originally misattributed to another species but now known to apply to this taxon. Herein named Guinope tiara n. gen., n. sp., the species shows molecular phylogenetic affinities with the family Linnaeoxanthidae Stevcic, 2005, an ally of panopeid and pseudorhombilid crabs. Specimens from Occulina banks off the Florida Atlantic coast, previously regarded to represent Garthiope barbadensis (Rathbun, 1921), are not that species but instead morphologically assignable to Guinope n. gen. Whether they represent variants of Guinope tiara n. gen, n. sp. or a second species of the genus awaits the collection of fresh materials for DNA analyses.
A new mud shrimp of the genus Pugnatrypaea from outer continental shelf waters of the northern Gulf of Mexico, commonly associated with hydrocarbon seeps (Crustacea: Decapoda: Callianassidae)
A new species of callianassid mud shrimp is described from outer continental shelf waters of the northwestern Gulf of Mexico, where it appears to commonly live in close association with sediments on or near natural hydrocarbon seeps. Recent genus-level taxonomic revisions of the Callianassidae, based on gene sequence analyses and comparative morphological studies, included specimens representing this new species, assigning it with strong support to the genus Pugnatrypaea Poore et al., 2019. The other known species of this genus are also typically found in offshore waters of continental shelves, but are all restricted in distribution to the Indo-West Pacific and are known from relatively few specimens. Collections of this new Gulf of Mexico representative of the genus are all from slightly deeper waters than for other known congeners, and commonly occur near hydrocarbon seeps, on some occasions being directly associated with sulfidic substrates that include waxy crude oil globules.
A new crab of the genus Nanoplax from the Gulf of Mexico, and assignment of Micropanope pusilla to a new genus (Crustacea, Brachyura, Pseudorhombilidae)
Nanoplax thomai n. sp. is described from the Gulf of Mexico, representing the second species of the genus. The description is based upon a number of specimens previously misidentified as Micropanope truncatifrons Rathbun, 1898, including one so represented in recent molecular phylogenetic analyses. As restricted, Micropanope truncatifrons remains known with certainty from only the limited type series, which does not include a mature male, and sequence quality tissues are not available for molecular phylogenetic analyses. Its generic placement remains questionable following morphological study of its type materials and comparisons to specimens representing other present and former members of Micropanope Stimpson, 1871. Those comparisons underscore that morphological and molecular distinctions warrant assignment of Micropanope pusilla A. Milne-Edwards, 1880 to a new genus, herein designated as Pseudopanopeus n. gen.
A new genus and species of mud crab (Crustacea, Brachyura, Panopeidae) from shoreline waters of the western Gulf of Mexico
Several specimens of a small panopeid crab from coastal waters of the western Gulf of Mexico were long suspected to represent an undescribed species and are herein designated as representatives of a new genus. While the originally collected specimens from over four decades ago were not of gene-sequence quality, later collections from the same locality produced materials that yielded sequence data for inclusion in molecular phylogenetic studies. Building on results of those analyses, the present taxonomic description draws upon morphology to support the description of a unique species in which especially the male first gonopods differ from those of all other described panopeid genera. To date, the species remains known from only two western Gulf of Mexico sites, both of which are wave-washed intertidal rocky habitats where substrates are heavily burrowed by boring bivalves and sipunculans. While we cannot exclude the possibility that the species was introduced, recurrent collections show its populations to be at very least persistent, the species most likely being a long-overlooked among a confusing hard-substrate assemblage of small panopeid crabs.
Description of Paraxiopsis kensleyi n. sp., a new axiid lobster from the Gulf of Mexico (Crustacea: Decapoda: Axiidea)
A new species of axiid was discovered during sampling offshore deep banks on the middle continental shelf off Louisiana. Paraxiopsis kensleyi n. sp. appears to inhabit interstices and cavities of coralline algal rubble, rhodoliths, coral rubble, and other eroded calcareous substrates. Weakly separated from Eutrichocheles Wood-Mason, 1876 on the basis of morphology, present assignments of western Atlantic species to Paraxiopsis de Man, 1905 are regarded as provisional. The new species is described morphologically, and the coloration of freshly captured specimens is documented and compared to related species where possible. Coloration readily distinguishes mature specimens of the new species from Paraxiopsis spinipleura Kensley, 1996, with which it was initially confused. The diagnosis includes GenBank accession numbers for COI sequences to allow future molecular phylogenetic comparisons. Compared to regional species that share a similar dentation or spination on the submedian carina, the pleon of the new species is distinctive in the truncate ventral margin on pleura 2–4, as opposed to being broadly rounded or directed ventrally in an acutely triangular tip. The new species is the eighteenth species of Paraxiopsis worldwide and the ninth from western Atlantic waters, seven of which are now known to range into the Gulf of Mexico. An updated key to western Atlantic members of the genus is provided.
Molecular phylogenetic analysis of the Paguristes tortugae Schmitt, 1933 complex and selected other Paguroidea (Crustacea: Decapoda: Anomura)
Morphological characters, as presently applied to describe members of the Paguristes tortugae Schmitt, 1933 species complex, appear to be of limited value in inferring phylogenetic relationships within the genus, and may have similarly misinformed understanding of relationships between members of this complex and those presently assigned to the related genera Areopaguristes Rahayu & McLaughlin, 2010 and Pseudopaguristes McLaughlin, 2002. Previously undocumented observations of similarities and differences in color patterns among populations additionally suggest genetic divergences within some species, or alternatively seem to support phylogenetic groupings of some species. In the present study, a Maximum Likelihood (ML) phylogenetic analysis was undertaken based on the H3, 12S mtDNA, and 16S mtDNA sequences of 148 individuals, primarily representatives of paguroid species from the western Atlantic. This molecular analysis supported a polyphyletic Diogenidae Ortmann, 1892, although incomplete taxonomic sampling among the genera of Diogenidae limits the utility of this finding for resolving family level relationships. Several hypotheses regarding the evolutionary relationships among hermit crab genera were refuted by the Kishino-Hasegawa (KH). ShimodairaHasegawa (SH) and Approximately Unbiased (AU) tree topology tests, among them the hypothesis that Areopaguristes is monophyletic. A lack of support for the monophyly of Areopaguristes calls into question the phylogenetic validity of gill number for the differentiation of Paguristes, Areopaguristes, and Pseudopaguristes. The study was inconclusive with regard to the relationships among these three genera, but previously unknown diversity within both Paguristes and Areopaguristes was demonstrated. Existence of an undescribed species confounded under the name Paguristes tortugae Schmitt, 1933 was supported by genetics, morphology, and coloration. A second undescribed species with remarkable similarity to Areopaguristes hummi Wass, 1955 was discovered based on genetics and coloration.
A new shallow-water mud crab of the genus Hexapanopeus Rathbun, 1898 from Belize (Crustacea: Decapoda: Panopeidae)
A new species of panopeid crab from shallow coastal waters of Belize is formally described and named based upon comparative study of three small specimens obtained in the course of a regional biodiversity survey of decapod crustaceans. The herein designated holotype of Hexapanopeus klausruetzleri n. sp. is a specimen previously included in a comparative molecular phylogenetic analysis that showed it to be closely related to, but genetically distinct from, the western Atlantic species Hexapanopeus angustifrons (Benedict & Rathbun, 1891). Hexapanopeus klausruetzleri n. sp. differs from this widely reported warm-temperate species in both its smoother carapace and pereopod surfaces and its generally more lobiform anterolateral teeth. The unique male first gonopod of the new species also strongly supports its morphological separation from all known congeners and other superficially similar western Atlantic panopeids with which it might be confused. To date, mature females have not been found, and the limited available collections are restricted to the vicinity of Carrie Bow Cay and nearby waters. Fourteen additional species of small panopeid and pseudorhombilid crabs, similar to Hexapanopeus klausruetzleri n. sp. in size and general habitus, were taken in the course of our studies in Belize. Most have not been previously reported from these waters, and several warrant further study to confirm their identifications.
Two new marine hermit crabs allied with the Paguristes tortugae complex (Crustacea: Decapoda: Anomura) from the western Atlantic
A recent molecular phylogenetic analysis that focused on selected species of western Atlantic Paguristes Dana, 1851, Areopaguristes Rahayu & McLaughlin, 2010, and Pseudopaguristes McLaughlin, 2002 was somewhat inconclusive regarding relationships among those genera, but it revealed two new unrecognized species genetically related to members of the Paguristes tortugae complex. One of the new species is sister to A. hummi (Wass, 1955), which is readily separated from Wass’ taxon by significant differences in coloration. However, no definitive characters have been found for its identification on the basis of structural morphology. A second new species is genetically sister to P. tortugae Schmitt, 1933, even though it was regarded in earlier literature as no more than an ecomorphic variant expressing protective coloration related to habitat substrate color. In addition to its unique coloration, subtle distinctions are evident in structural morphology. Both species are formally named with accompanying morphological and color descriptions.
A new mud shrimp of the genus Paragourretia Sakai, 2004, from the Gulf of Mexico (Crustacea: Decapoda: Ctenochelidae)
A new western Atlantic member of the ctenochelid genus Paragourretia Sakai, 2004 is described to accommodate a single unique specimen collected by dredge on muddy rubble substrates of the continental shelf in the southwestern Gulf of Mexico. Paragourretia sandrae n. sp. closely resembles Paragourretia biffari, another regionally reported species for which photographs and additional illustrations are herein provided. While P. biffari and P. sandrae n. sp. are similar in habitus and known habitat o the more commonly encountered confamilial Dawsonius latispina, the third maxillipeds in Paragourretia bear distinct exopods that are absent in Dawsonius. As in eight other world congeners, P. sandrae n. sp. differs from both P. biffari and Dawsonius in lacking triangular ventrolateral projections on the sixth pleomere. It is further distinguished from P. biffari by lacking a distinctly incised notch in the anterodistal margin of the uropodal exopod and by absence of a median terminal spine on the telson. Additional sequence-quality specimens of P. sandrae n. sp. are required to clarify its relationships within the polyphyletic genus Paragourretia on a molecular genetic basis.
New species and records of the symbiotic shrimp genus Leptalpheus Williams, 1965, with notes on Fenneralpheus Felder & Manning, 1986, and preliminary molecular analysis of phylogenetic relationships (Crustacea: Decapoda: Alpheidae)
The shrimp genera Leptalpheus Williams, 1965 and Fenneralpheus Felder & Manning, 1986 are composed entirely of symbiotic species that co-inhabit burrows of infaunal macrocrustaceans. We report extensive collections of these genera from western Atlantic, eastern Pacific and Indo-West Pacific regions. Integrative taxonomy methods, including morphological comparisons and analysis of three mitochondrial genetic markers, are used to test species hypotheses and evolutionary relationships among members of these genera. Our molecular analysis failed to recover Leptalpheus or Fenneralpheus as monophyletic groups. Our results strongly supported the monophyly of three clades composed of species of Leptalpheus, loosely corresponding to previously proposed species groups. Three new species closely related to Leptalpheus forceps Williams, 1965, L. marginalis Anker, 2011, and L. mexicanus Ríos & Carvacho, 1983 are described. Leptalpheus ankeri n. sp., from the Caribbean Sea, Atlantic coast of Florida, and Gulf of Mexico, is a polymorphic species that exhibits two major cheliped morphotypes. Leptalpheus sibo n. sp., from the Pacific coast of Nicaragua, is morphologically very similar to L. ankeri n. sp., likely its transisthmian sister species, and shares its cheliped polymorphism. A reassessment of L. forceps concluded that records of this species from the Caribbean Sea and Brazil are not conspecific with L. forceps sensu stricto from the Atlantic coast of the USA and the Gulf of Mexico, and they are herein described as Leptalpheus degravei n. sp. Based on both molecular and morphological evidence, we found Leptalpheus bicristatus Anker, 2011 to be a junior synonym of L. mexicanus and Leptalpheus canterakintzi Anker & Lazarus, 2015 to be a junior synonym of Leptalpheus azuero Anker, 2011. First reports of Leptalpheus axianassae Dworschak & Coelho, 1999 in Texas and Mexico, Leptalpheus denticulatus Anker & Marin, 2009 in the Mariana Islands, Leptalpheus felderi Anker, Vera Caripe & Lira, 2006 and Leptalpheus lirai Vera Caripe, Pereda & Anker, 2021 in the USA, and Leptalpheus pereirai Anker & Vera Caripe, 2016 in Cuba are included.
Two new burrowing mud shrimps of the genus Gilvossius from the Gulf of Mexico (Crustacea: Decapoda: Callianassidae)
Previous reports of Gilvossius setimanus (De Kay, 1844) from the Gulf of Mexico have been based on a population of small specimens from deep offshore continental shelf waters off Texas and larger specimens from shorelines and shallow embayments of western Florida. The offshore population, herein designated Gilvossius fredericqae n. sp., reaches sexual maturity at much smaller size than does Gilvossius setimanuss.s. from the U.S. Atlantic seaboard, a species from which it differs in a number of morphological characters. While maturing at a similar size to G. setimanus s.s., a western Florida population, herein designated Gilvossius howellorum n. sp., differs from it in the 16S mt gene sequence, and from both it and the offshore species in morphology. An updated synonymy and rediagnosis of G. setimanus s.s. herein accompany descriptions of the two new species.
Morphological and molecular characterization of Paratylenchus beltsvillensis n. sp. (Tylenchida: Paratylenchidae) from the rhizosphere of pine tree ( Pinus virginiana Mill) in Maryland, USA
The pin nematode, Paratylechus beltsvillensis sp. collected from rhizosphere soil of a Virginia pine tree (Pinus virginiana Mill) growing in Little Paint Branch Park, Beltsville, Prince George’s County, Maryland, USA, is described and illustrated along with light and scanning electron photomicrographs. Females, males, and juveniles of this new species were recovered from soil samples using the sugar centrifugal flotation and Baermann funnel extraction methods. Morphologically, females are short, body length ranging from 245 to 267 μm, stylet from 70 to 75 μm long with anchor shaped knobs, vulva located at 70–73% and small vulval flap, spermatheca large, and ovoid filled with sperms. Lateral field with three incisures, of which the outer two are prominent. Tail slender, having a rounded tail terminus. Males without stylet and have a degenerated pharynx, spicules = 17–20 µm and gubernaculum = 5.0–5.5 µm. Both morphological observations and molecular analysis of ITS and partial 28S ribosomal RNA gene sequences indicated that the specimens collected from the soil at Beltsville Park from rhizosphere soil samples from Virginia pine represents a new pin nematode species.
Molecular and morphological characterization of a first report of Cactodera torreyanae Cid del Prado Vera & Subbotin, 2014 (Nematoda: Heteroderidae) from Minnesota, the United States of America
Cactodera torreyanae Cid del Prado Vera & Subbotin, 2014 cysts were discovered during a Pale Potato Cyst Nematode (PCN) survey conducted by Minnesota Department of Agriculture as part of the Animal and Plant Health Inspection Service (APHIS) efforts to survey states for the presence of PCN. The soil samples were collected from a potato field, located in Karlstad, Kittson County, Minnesota, USA. Two out of 175 vials submitted for identification to the Mycology and Nematology Genetic Diversity and Biology Laboratory (MNGDBL) contained few cysts and juveniles of C. torreyanae. Cysts were dark brown in color, lemon-shaped to elongated with distinct vulval cone. Vulva with denticles present around fenestra, cyst length to width ratio between 1.6 and 2.3 and anus distinct. The juveniles had rounded stylet knobs, some sloping slightly posteriorly. The molecular analysis included sequence and phylogenetic analysis of ITS rRNA, D2-D3 expansion segments of 28S rRNA and COI of mtDNA genes. The nematode species was identified by both morphological and molecular means as Cactodera torreyanae. To the best of our knowledge this represents the first report of Cactodera torreyanae from the United States and first report of this cyst nematode species from potato fields. Definite host plant for this nematode remains unknown.