Fourth Pereopods Research Articles

A new genus and species of micro-pagurid hermit crab (Crustacea, Decapoda, Paguridae) from the rariphotic reef zone in Curaçao, Lesser Antilles, Caribbean Sea.

During field investigations of deep-reefs off the coast of Curaçao in the Lesser Antilles, Caribbean Sea, a female specimen was collected of an undescribed micro-pagurid crab with striking dorso-ventral flattening of the right cheliped. It was further characterized by a reduced branchial formula, fourth pereopods with grasping-like spines instead of typically pagurid rasp-like scales, nearly symmetrical uropods and telson, and a minute pair of first pleopods (gonopods). The single specimen was discovered in samples from the rariphotic zone (~130-309 m) obtained using a suction sampler operated from the manned submersible R/V Curasub over cryptic habitats and surfaces populated by communities of sessile macro-organisms. As the specimen does not fit any known pagurid taxon, we regard it to represent a new monotypic genus. We fully describe this new micro-pagurid as Raripagurus roseangelae n. gen., n. sp. and also provide photographs of its live coloration. The CO1 barcode for the holotype in the Barcode of Life Database and GenBank accession number are included as part of the description for any future phylogenetic investigations.

Chirostyloid and galatheoid squat lobsters (Decapoda: Anomura) from Andaman and Nicobar Islands, India, with three new species

ABSTRACT The squat lobster fauna of the Andaman and Nicobar waters, India is known to be represented by more than 40 species from 19 genera and six families. Seven species, including three new to science, collected from six dedicated surveys of the Fishery Oceanographic Research Vessel Sagar Sampada during 2011–2019 are described. Gastroptychus valdiviae Balss, 1913 is redescribed based on the syntype and the newly collected material. Grimothea krishaha sp. nov. and an unidentified species provisionally assigned to Grimothea Leach, 1820 are reported. These two species of Grimothea differ from known congeners in the spination on the carapace, pleon, antennule, antenna and third maxilliped. Examination of the syntype and newly collected specimen revealed that Munida vigiliarum Alcock, 1901 should be transferred to Leptonida Macpherson and Baba in Machordom et al., 2022. Leptonida vigiliarum comb. nov. is here redescribed. Trapezionida aequispina sp. nov. differs from related species in the spination on the carapace, and in the shape and relative lengths of the second to fourth pereopod dactyli. Trapezionida bharuchai sp. nov. differs from related species in the carapace morphology, the presence of a mesial spine on the antennal peduncle second article, and the armature on pereopods. Leiogalathea sp. does not resemble known congeners in morphological aspects, but because of the poor condition of the unique specimen presently available for study, formal description is deferred in the hope that additional material will be collected. With this report, the number of species reported from the region increases to 47. http://www.zoobank.org/urn:lsid:zoobank.org:pub:A82CE9B3-BF67-4282-97DF-20D37CF02464

Squat lobsters of the genera Raymunida Macpherson & Machordom, 2000 and Munidopsis Whiteaves, 1874 (Decapoda: Anomura: Galatheoidea) from the Indian Exclusive Economic Zone, with descriptions of three new species

ABSTRACT We report four squat lobster species of the genera Raymunida Macpherson and Machordom, 2000 (Munididae) and Munidopsis Whiteaves, 1874 (Munidopsidae) from the Indian Exclusive Economic Zone. The genus Raymunida is recorded for the first time from Indian waters, including a new species R. shraddhanandi sp. nov. and R. vittata Macpherson, 2009 based on material from the Andaman Sea. Raymunida shraddhanandi sp. nov. differs from its closest congener R. formasanus Lin, Chan and Chu, 2004 in the armatures of the anterior branchial carapace region, antennal peduncle and third maxilliped merus, and the length of the fourth pereopod. Two new species of the genus Munidopsis, referred to the Anoplonotus group, are described from the south-western Bay of Bengal and the south-eastern Arabian Sea. Munidopsis bengala sp. nov. and M. kadal sp. nov. are distinguished from all of their allies – M. bruta Macpherson, 2007, M. shulerae Vázquez-Bader, Gracia and Lemaitre, 2014, and M. truculenta Macpherson and Segonzac, 2005 – by the unarmed dorsodistal margin of the third maxilliped merus and the relative length of the antennal peduncle, respectively. http://www.zoobank.org/urn:lsid:zoobank.org:pub:5C724556-6532-41F2-9A6E-8424CAE0F2C6

A new species of Pseudomoraria from an alpine spring of Picos de Europa, North of Spain

Pseudomoraria triglavensis was described by Brancelj (1994) from specimens collected in a high-alpine reservoir at the Triglav National Park (NW Slovenia) at an altitude of 1690 m a.s.l. During an expedition in the Picos de Europa National Park (N Spain) in 2018, a new species of Pseudomoraria was collected in an epikarst spring (Fuente Escondido), below the ice cave of Altaiz at an altitude of 2112 m a.s.l. The new species can be easily distinguished from Pseudomoraria triglavensis by the presence of an inner seta on the edopodite 1 of female and male pereopod 1; absence of the outer spine on the exopodite 2 of the third and fourth female pereopods; four, instead of five setae on the second endopodite of the fourth female pereopod; and the female furca lacks the ventral distal patch of spinules characteristic of P. triglavensis. In the male, the new species differs from its congeners by the position and shape of the apophysis of the second edopodite of the pereopod 3, which is positioned in the outer, instead of the inner margin, and is bent around the distal inner spine; the second exopodite of the pereopod 4 has spines/setae, lacking the innermost seta which is present in P. triglavensis. The female armature of the pereopod 5 is highly variable, with 4-6 setae/spines on the exopod and 4-6 setae on the baso-endopod. According to Brancelj (1994), P. triglavensis could not be included in any genus known at the time and concluded, based on the armature of the pereopod 5 of both sexes, that it would be most closely related to Moraria. We disagree with this author and propose a close relationship of this genus with the genus Hypocamptus Chappuis, 1929 sharing similar male pereopod segmentation and armature. In addition, the species belonging to both genera are a characteristic for the fauna of the alpine water bodies. It is not yet clear the phylogenetic relationship between the two genera, but evidences suggest that Pseudomoraria may be a junior synonym of Hypocamptus.

Two axiidean ghost shrimps (Crustacea: Decapoda) from India, Guyanacaris keralam sp. nov. (Axiidae) and Paragourretia galathea (K. Sakai, 2017) (Ctenochelidae).

Ghost shrimps collected from the Indian Exclusive Economic Zone by the Fishery Oceanographic Research Vessel Sagar Sampada during two cruises in the eastern (105 metres depth) and southeastern Arabian Sea (101 and 326 metres depth) were studied. One male, identified as Guyanacaris keralam sp. nov. of the Axiidae, differs from its congeners in the unique armature of the rostrum, gastric region of carapace, pleonal pleural margins, dorsal margins of cheliped fingers, ventral margin of second pereopod merus, and lateral margins of telson; the presence of corneous spines on the propodi and dactyli of third and fourth pereopods, and the relative sizes of the ocular peduncles, antennular peduncle, scaphocerite and cheliped fingers. Guyanacaris K. Sakai, 2011 is re-diagnosed based on the presence of short supraocular spine and post-cervical carina on carapace, dentate margins of first two pleonal pleura, third to fifth pleura with angular to straight posterior margins, antennal scaphocerite with mesial spine at base, and presence of male first pleopod 1. Bruceaxius thailandensis K. Sakai, 2015 is tentatively retained in Bruceaxius K. Sakai, 2011, owing to absence of mesial spine at the base of scaphocerite, tuberculate upper margins of carpus, propodus and dactylus of major cheliped, and tri-segmented appendix masculina on male second pleopod. In addition, two males, diagnosed herein as Paragourretia galathea (K. Sakai, 2017) of the Ctenochelidae, differ from the holotype female only in the relative length of the terminal antennular article and the presence of a distomedian spinule on the telson, of all the features.

A new pinnotherid crab of the genusPinnixulalaPalacios Theil, Cuesta & Felder, 2016 from uncertain infaunal hosts in the northern Gulf of Mexico, with a rediagnosis and updated synonymy for the polychaete symbiontPinnixulala retinens(Rathbun, 1918) (Decapoda: Brachyura: Pinnotheridae)

AbstractA new infaunal pinnotherid crab, Pinnixulala heardin. sp., is described from muddy substrates of the middle to inner continental shelf of the northern Gulf of Mexico. Molecular genetic analysis supports its separation from P. retinens (Rathbun, 1918), the only other western Atlantic member of the genus and a species most commonly found living as a symbiont of large polychaete worms. Both western Atlantic species are clearly separated from several described and undescribed populations of congeners occurring along shorelines of the eastern Pacific. We herein include a rediagnosis of P. retinens to facilitate morphological comparisons with P. heardin. sp. Unlike P. retinens, which is more common in shallow inshore waters and reaches larger sizes, the new species lacks development of a strong distally directed spine on the fourth pereopod ischium and has chelae that are at least as heavily developed as the second and third pereopods. In addition, the mature male first gonopods in P. heardin. sp. are tapered over their terminal one-third and directed distally, rather than being curved in their terminal one-third with the tips directed mesially, as they are in P. retinens. The new species is invariably collected from samples including infaunal worms and other invertebrates, but the specific hosts remain to be determined

A new species of Alvinocaris (Crustacea: Decapoda: Caridea: Alvinocarididae) from hydrothermal vents in the Izu-Bonin and Mariana Arcs, north-western Pacific

AbstractA new species of the caridean genus Alvinocaris, A. marimonte sp. nov., is described and illustrated on the basis of specimens collected from hydrothermal vents at three locations in Izu-Bonin and Mariana Arcs of the north-western Pacific Ocean, Myojin Knoll (1224 m depth), NW Eifuku (1574–1582 m depth) and NW Rota seamounts (525 m depth). It is the 17th species assigned to Alvinocaris, and differs from all other congeneric species in several morphological characteristics derived from the rostrum length and armature, the carapace armature, the shape of the posterior margin of the telson and the armature of the third and fourth pereopods. Results of molecular phylogenetic analyses based on partial sequences of the mitochondrial COI and nuclear ITS-I genes compared between specimens of A. marimonte sp. nov. and other known species of Alvinocaris supported our recognition of the new species, although available data are still limited. Alvinocaris marimonte sp. nov. is represented by two morphotypes, distinguished by the armature of the posterior margin of the telson (spines vs plumose setae), which were not detected as separate species by the molecular analysis. Our discovery of the intraspecific variation in the armature of the posterior margin of the telson led us to reassess diagnostic characters used to distinguish species within the genus Alvinocaris.

Description of a new alpheid shrimp, Automate isabelae sp. nov. (Decapoda, Caridea, Alpheidae) found in fish stomach contents of the lane snapper Lutjanus synagris (Linnaeus, 1758), from the west coast of Florida, Gulf of Mexico.

A new species of caridean shrimp of the family Alpheidae, Automate isabelae sp. nov., found in stomach analysis contents of the lane snapper Lutjanus synagris (Linnaeus, 1758), from the Keys and SW coast of Florida, Gulf of Mexico, is described. The abdomen and portions of the cephalic appendages were damaged in holotype, but remainder of the body and the chelipeds, whith the most important diagnostic characters are in decent or perfect condition, the description was further supplemented based on intact morphological parts of the paratypes. The presence of tubercles on the dorsal and ventral margins of the major chela palm, shows this new species to be related to the eastern Pacific Automate rugosa Coutière, 1902. Both congeners can be easily discriminated by the proportions and shape of the third maxilliped, the proportions and ornamentation of the carpus, merus, and chela of the major cheliped, the ventral seta of the carpus of the minor cheliped, the presence of a distoventral spine on the propodi of third and fourth pereopods, the armature of dorsal surface of telson, and their geographical distribution. The description of this new species increases the number of worldwide valid species known of the genus Automate to 12.

A new pea crab species of the genus Arcotheres Manning, 1993 (Crustacea: Decapoda: Brachyura: Pinnotheridae) from India.

A new species of pinnotherid crab, Arcotheres shahi n. sp., is described on the basis of specimens collected during a crustacean survey along the coastal areas of Pamban fishing harbor in the Gulf of Mannar, Tamil Nadu state, east coast of India. The new species resembles A. pernicola (Bürger, 1895), A. winckworthi (Gordon, 1936) and A. rayi Ahyong Ng, 2007, in having the dactyli of the longer fourth pereopod longer than that of fifth pereopod. Arcotheres shahi n. sp. differs from these three known species in the shape of female carapace, frontal region and chela, setal pattern on the dactyli of the fourth and fifth pereopods and relative length of the ambulatory pereiopods.

A new gammaridean amphipod from the Lake District Region of Turkey: Gammarus deryae sp. nov.

In order to determine the distribution and composition of freshwater amphipod species of the Lake District Region of Turkey, detailed samplings were conducted between 1998 and 2001. Among these materials, those from Pinar Pazari and Yukari Gokdere villages (Isparta Province, Turkey) were studied in the present study. Because of having different character combinations, the author believes that they belong to a new species, Gammarus deryae sp. nov. The new species is a typical member of the Gammarus pulex -group having setose third and fourth pereopod and uropod 3 where dense plumose setae exist. Elevated urosomal segments and sharply pointed third epimeral plate are the most distinct characters of the species. In addition, the palp of right maxilla 1 has 1 seta on the outer margin. These encountered characters are commonly observed in the G. pulex -group but the combination of these characters is specific for the newly identified species. All the extremities of the holotype male and allotype female are illustrated and described in detail. The similar and different morphological characters of the new species are compared with those of related species.

The shell-acquisition behaviour of the bivalve-using hermit crab Porcellanopagurus nihonkaiensis Takeda, 1985 (Decapoda, Anomura, Paguroidea)

Almost all species of hermit crabs inhabit dead gastropod shells; however, species of some genera have evolved to inhabit bivalve or patelliform shells. It has been assumed that these species carry their shells using uropodal rasps and the hooked dactyls of their fourth pereopods, although no detailed description of the shell acquisition behaviour of those species has previously been documented. We have therefore observed the shell acquisition behaviour of Porcellanopagurus nihonkaiensis Takeda, 1985, which was collected by dredge at Shimoda, Shizuoka Prefecture, Japan. Our observation suggests that the shell is fixed in place by only the uropodal rasps in combination with hydrostatic pressure in the telson.

A new genus and species of axiid shrimp (Crustacea, Decapoda) from a southwestern Indian Ocean seamount

A new genus and species of axiid shrimp, Montanaxius mediumquod gen. et sp. nov., is described and illustrated based on three specimens collected from hexactinellid sponges from a seamount in the southwest Indian Ocean. The new genus is characterized by a laterally denticulate rostrum, short lateral carina, absence of submedian carina, a prominent toothed median carina, round pleomere pleura 2–5, pleurobranchs on second to fourth pereopods, and the presence of a male first pleopod and appendix interna on pleopods 3–5. It most closely resembles Levantocaris Galil & Clark, 1993 and Planaxius Komai & Tachikawa, 2008, but differs from the former by being gonochoristic, having a strongly elevated gastric region and well-developed eyes, and from the latter by its toothed median carina and the presence of a median telson spine.

New records of caridean shrimp (Crustacea: Decapoda) from hydrothermally influenced fields off Futuna Island, Southwest Pacific, with description of a new species assigned to the genus Alvinocaridinides Komai & Chan, 2010 (Alvinocarididae).

Five species of caridean shrimp, including four Alvinocarididae Christoffersen, 1986 and one thorid species of the genus Lebbeus White, 1847, are reported from the recently discovered hydrothermal vent field off Futuna Island in the Southwest Pacific (depths 1418-1478 m): Alvinocaridinides semidentatus n. sp., Alvinocaris komaii Zelnio & Hourdez, 2009, Nautilocaris saintlaurentae Komai & Segonzac, 2004, Rimicaris variabilis (Komai & Tsuchida, 2015), and Lebbeus wera Ahyong, 2009. The new species, provisionally assigned to Alvinocaridinides Komai & Chan, 2010, is readily distinguished from the type species of the genus, A. formosa Komai & Chan, 2010, by the characteristic armature of the rostrum and of the propodi of the third and fourth pereopods and the possession of ischial spines on the third and fourth pereopods. Identification of R. variabilis has been confirmed by morphology and sequence comparison of mitochondrial COI gene. The geographical range of L. wera is extended to the north from the Brothers Caldera in the Kermadec Ridge.

Enosteoides Johnson, 1970 (Crustacea: Decapoda: Anomura: Porcellanidae) from the Central Philippines, with description of a new species of the genus

Three species of the porcellanid genus Enosteoides Johnson, 1970, including a new species, are reported from the Central Philippines on the basis of material mainly collected by the PANGLAO Marine Biodiversity Project 2004. Enosteoides lobatus Osawa, 2009 and E. palauensis (Nakasone and Miyake, 1968) are new to the Philippine crustacean fauna. Enosteoides turkayi n. sp. is most closely allied to E. melissa (Miyake, 1942) and E. philippinensis Dolorosa and Werding, 2014 in the shape and structure of the rostrum and chelipeds and the comparatively slender second to fourth pereopods. However, the new species is distinguished from E. melissa and E. philippinensis by the third thoracic sternite without an anteriorly produced median lobe and the carpi and propodi of the second to fourth pereopods being bright red for the most part.

Androgenic Gland Implantation Induces Partial Masculinization in Marmorkrebs Procambarus fallax f. virginalis.

The androgenic gland in malacostracan crustacean species produces and secretes androgenic gland hormone, which is responsible for male sexual differentiation, such as the induction and development of male sexual traits, and in turn the suppression of female sexual traits. Marmorkrebs, Procambarus fallax forma virginalis, which was identified as the first parthenogenetic species in decapod crustaceans, produces only female offspring. In this study, in order to reveal whether the Marmorkrebs crayfish is sensitive to androgenic gland hormone, we transplanted an androgenic gland from a related congener, P. clarkii, to P. fallax f. virginalis. In androgenic gland-implanted specimens, partial masculinization was confirmed: the masculinization of several external sexual characteristics (i.e., thickening of the first and second pleopods; formation of reverse spines on the third and fourth pereopods) was detected, whereas that of internal sexual characteristics (e.g., the formation of ovotestes and male gonoducts) was not. Our results imply that P. fallaxf. virginalis still has sensitivity to the androgenic gland hormone and, at least partly, the hormone should be able to induce male characteristics, even in parthenogenetic Marmorkrebs.

Raymunida Macpherson & Machordom, 2000 (Crustacea: Decapoda: Anomura: Munididae) from the KUMEJIMA 2009 Expedition in the Ryukyu Islands, Japan

Two species of the munidid genus Raymunida Macpherson & Machordom, 2000, are reported from Kume Island, RyukyuIslands, southwestern Japan. Raymunida striata n. sp. appears closest to R. confundens Macpherson & Machordom, 2001,and R. dextralis Macpherson & Machordom, 2001, but is distinguished by the second and third abdominal somites eachwith an uninterrupted stria between two distinct transverse ridges on the dorsal surface, the merus of the third maxillipedwith a prominent distal spine on the extensor margin, and the mero-carpal articulation of the fourth pereopod reachingonly to the lateral end of the anterior cervical groove of the carapace. The occurrence of R. vittata Macpherson, 2009, inKume Island greatly extends its distribution range to the north hemisphere. Morphological variations of R. vittata are also discussed on the basis of the present specimens. An updated key to the species of Raymunida is provided.

Notes on two species of Processa (Decapoda: Processidae) from the Mexican Pacific

Material belonging to the genus Processa, held in the Regional Marine Invertebrates Collection in Mazatlán, Mexico, is revised including specimens of the widely distributed P. peruviana, and the scarcely collected P. hawaiensis. For comparative purposes with the specimens from Hawaii and other localities, a detailed description of a male of P. hawaiensis collected in continental Mexico is provided, including illustrations of all appendages. Small differences are noted with previous description and partial redescriptions of this species, including proportion between propodus and dactylus of the fourth pereopod, and between merus and carpus of the right cheliped. In addition, the shape and setation of the first pair of pleopods in the Mexican material differs from the description of P. hawaiensis based on African material.

Postispinatus youngi n. gen., n. sp. (Apseudomorpha; Tanaidacea; Crustacea): phylogenetic analysis and taxonomic remarks about kalliapseudids

The presence of setae or a sensorial structure on the dactylus of pereopod 1 as one of the defining features of the familyKalliapseudidae is re-evaluated. A new genus, Postispinatus, including the new species P. youngi n. gen., n. sp., isdescribed and thought to belong to the Kalliapseudidae based on phylogenetic analysis. The diagnostic features of newgenus—and species by monotypy —are: basal article of uropod with two curved spiniform processes; exopods on the fourth and fifth pereopods of the manca stage; absence of a maxillule palp.

Embryonic Development and Expression Analysis of Distal-less in Caprella scaura (Crustacea, Amphipoda, Caprellidea)

The Caprellidea generally possess rudimentary abdomens and degenerated third and fourth pereopods. Previous molecular phylogenetic studies support the concept that their unique body plan is derived from a gammarid-like body plan from which the abdomen or third and fourth pereopods have been lost in the Caprellidea. To understand the developmental and genetic mechanisms for the morphological evolution of the Caprellidea, we observed the embryonic development of Caprella scaura. Although in the early embryonic stage limb buds appeared in all of the pereonites, we found that elongation of the limb buds did not occur in the third and fourth pereonites; instead, only oval projections (possibly primordial gills) were observed. We next examined the gene expression of Distal-less (Dll) by in situ hybridization and found that Dll was not expressed in the third and fourth pereonites. This suggests that the suppression of Dll expression is responsible for the reduction of Caprellidea pereopods.

Complicated evolution of the caprellid (Crustacea: Malacostraca: Peracarida: Amphipoda) body plan, reacquisition or multiple losses of the thoracic limbs and pleons

The Caprellidea (Crustacea) have undergone an interesting morphological evolution from their ancestral gammarid-like form. Although most caprellid families have markedly reduced third and fourth pereopods (the walking thoracic limbs) and pleons (the posterior body parts), one family, Caprogammaridae, has developed pleon with swimming appendages (pleopods), whereas another family, Phtisicidae, possesses well-developed functional third and fourth pereopods. The unique character status of these families implies that there has been reacquisition or multiple losses of both pereopods and the pleon within the Caprellidea lineages. Although the Caprellidea are fascinating animals for the study of morphological evolution, the phylogenetic relationships among the Caprellidea are poorly understood. One obstacle to studying the evolution of the Caprellidea is the difficulty of collecting samples of caprogammarid species. In this study, we obtained live samples of a Caprogammaridae species and confirmed that its pleon and pleopods could perform similar locomotive functions and swimming movements as observed in gammarids. From the phylogenetic analyses on 18S ribosomal RNA gene sequences, we identified three distinct clades of Caprellidea. The ancestral state reconstruction based on the obtained phylogeny suggested that once lost, the third and fourth pereopods were regained in the Phtisicidae, while the pleon was regained in the Caprogammaridae, while we could not exclude the possibility of independent losses. In either case, the caprellid lineage underwent a quite complicated morphological evolution, and possibly the Caprellidea may be an exception to Dollo's law.