Ambulatory Dactyli Research Articles

Odontonia kerangcaris sp. nov., a new bivalve-associated shrimp (Crustacea, Decapoda, Palaemonidae) from East Kalimantan, revealing intrageneric host switching

A new species of bivalve mollusk dwelling palaemonid shrimp of the genus Odontonia is described from the Berau Islands, East Kalimantan, Indonesia. This is the only Odontonia species recorded as a symbiont of a bivalve mollusk, all other congeners are known to associate with solitary ascidians. The new species belongs to the group wherein the dactylus of the ambulatory pereiopods has an accessory tooth. It differs from these species in the absence of a forward directed proximal tooth on the flexor margin of the corpus of the ambulatory dactyli. It also lacks the small denticles posterior to the distoventral accessory tooth on the dactylar corpus.

Evolution of protective symbiosis in palaemonid shrimps (Decapoda: Caridea) with emphases on host spectrum and morphological adaptations

Palaemonidae is the most speciose caridean shrimp family, with its huge biodiversity partially generated via symbiosis with various marine invertebrates. Previous studies have provided insights into the evolution of protective symbiosis in this family with evidence for frequent inter-phyla host switches, but the comprehensiveness of evolutionary pathways is hampered by the resolution of the previous phylogenetic trees as well as the taxon coverage. Furthermore, several critical issues related to the evolution of a symbiotic lifestyle, including the change in host spectrum and corresponding morphological adaptations, remain largely unresolved. We therefore performed a much extended phylogenetic comparative study on Palaemonidae, rooted in a comprehensive phylogeny reconstructed by a supermatrix-supertree approach based on a total of three mitochondrial and five nuclear markers. Ancestral state reconstruction of host associations revealed at least three independent evolutions into symbiosis, with potentially a drive to seek protection fuelling incipient symbiosis. Yet, most of the observed symbiotic species diversity was radiated from a single cnidarian associate. The evolution of mandibles and ambulatory dactyli suggests a general lack of correlation with host affiliation (except sponge endosymbionts), implying limited morphological adaptations following host switching, despite being putatively a major adaptive consequence of symbiosis. Our analyses of host spectrum, in terms of basic and taxonomic specificity, revealed no apparent phylogenetic signal but instead resolved a dynamic pattern attributable to frequent host switching. Uncoupling between host spectrum and the degree of morphological specialisation is the norm in palaemonids, suggesting that morphological characters are not fully in tune with host spectrum, in addition to host affiliation. This study demonstrates the complexity in the evolution of symbiosis, pointing to the presence of cryptic adaptations determining host spectrum and governing host switch diversification, and provides a clear direction for the evolutionary study of symbiosis in other marine symbiotic groups involving host switching.

Two New Species and a Further Country Record of the Caridean Shrimp Genus Periclimenaeus Borradaile, 1915 from Korea (Decapoda: Palaemonidae).

Two new species of the palaemonid genus Periclimenaeus are described and illustrated from Korea; additionally, a third species is recorded from Korea for the first time. Periclimenaeus karantina sp. nov. was obtained from ascidian hosts. The species has a denticulate dactylus on both second pereiopods, considered to be typical for ascidian associates. It can be separated from related species by the combination of the following characters: the carpocerite overreaching the anterior margin of the scaphocerite; the distolateral tooth of the scaphocerite exceeding the anterior margin of the lamella; the dactylus of the minor chela exceeding the fixed finger; and the ambulatory dactyli furnished with a minute proximal tooth. Periclimenaeus apomonosi sp. nov. was obtained from sponge hosts, and belongs to the P. robustus species-group, on account of the developed anterior median lobe on the tergite of the first abdominal somite. It can be distinguished from related species by the combination of the presence of a supraorbital tooth; the presence of a pointed process on the inferior orbital angle; the distolateral tooth of the scaphocerite terminating level with the anterior margin of the lamella; the antennal carpocerite reaching about 0.6 of the scaphocerite; the first and second chelae with non-serrated cutting edges; the ischium and merus of the second pereiopods harbouring tubercles on the ventral margin; and the ambulatory dactyli with a distal accessory tooth and the corpus furnished with denticles, ventrally. The sponge associated species, Periclimenaeus djboutensis, relatively widespread across the Indo-Pacific, is reported for the first time from Korea in Geomundo Island. Asides from a morphological description of all three species, molecular information of two genetic markers (16S + COI) is provided to aid in future phylogenetic reconstructions of the genus.

On the taxonomy of two rare freshwater crabs (Decapoda, Brachyura, Chasmocarcinidae and Hymenosomatidae) from Palau, western Pacific

Abstract The taxonomy of two species of secondary freshwater crabs endemic to Palau is discussed. Males of the chasmocarcinid Australocarcinus palauensis Davie & Guinot, 1996 (Trogloplacinae), previously known only from one female, are reported for the first time and the species is redescribed and figured. This species is closest to A. kanaka Davie & Guinot, 1996, from New Caledonia, but can be distinguished by the form of the carapace, third maxillipeds and gonopods. The rare hymenosomatid Neorhynchoplax inermis (Takeda & Miyake, 1971) (Hymenosomatinae), known only from the original description, is here shown to be distinct from species of Neorhynchoplax Sakai, 1938 s. str., differing in its complete absence of a true rostrum, absence of postocular lobes, the relatively short ischia and meri of the third maxillipeds, unarmed ambulatory dactyli and strongly twisted male first gonopod. The species is redescribed and transferred to a new genus, Insulaplax.

Cinetorhynchus gabonensis, a new species of hinge-beak shrimp(Crustacea: Decapoda: Rhynchocinetidae) from the eastern Atlantic.

A new species of the rhynchocinetid genus Cinetorhynchus, C. gabonensis sp. n. from the Atlantic waters of Gabon, is described based on morphological and molecular comparisons and its distinctive colour pattern. This is the second known species of the genus in the eastern Atlantic, and the third species in the Atlantic as the whole. The new species is more closely related to the western Atlantic C. manningi, both having quadrispinose ambulatory dactyli (i.e. with unguis + 3 ventral spinules), but differs from the latter by the presence of an arthrobranch on the three anterior pereiopods (vs only on the first pereiopod in C. manningi). The branchial formula of the new species is consistent with most of the Indo-West Pacific congeners, and with the amphi-Atlantic C.rigens; the latter possessing trispinose ambulatory dactyli. Other distinctions of the new species from its congeners are in the carpal and meral spinulation of the ambulatory legs, and in the posterolateral and posteroventral armament of pleomeres IV and V. Cinetorhynchus gabonensis sp. n. differs from both known Atlantic congeners also by a specific colour pattern which is dense deep-red mottled with a pair of small white spots delineated by deep-red broad rings on the top of the third pleomere.

A new species of Neorhynchoplax (Crustacea: Decapoda: Brachyura: Hymenosomatidae) from Taiwan.

A new hymenosomatid crab, Neorhynchoplax chipolini sp. nov., is described from Taiwan. Of the 32 known species of Neorhynchoplax, only five other species possess a posterolateral tooth on the carapace and unarmed ambulatory dactyli as in N. chipolini sp. nov.: i.e. N. attenuipes (Chopra Das, 1930), N. falcifera Naruse, Mendoza Ng, 2008, N. sinensis (Shen, 1932), N. tuberculata (Chopra Das, 1930), and N. venusta Ng, 2015. Neorhynchoplax chipolini sp. nov., however, differs from these congeners by having the median rostral tooth distinctly bent downwards and the presence of a tubercle on the inner anterolateral margin of the first exopod article of the third maxilliped. Brood size, egg diameters, and the protective structure of eggs in N. chipolini sp. nov. are noted. A table for the habitat preferences of all known species of Neorhynchoplax is provided.

Madangella altirostris, a new genus and species of palaemonid shrimps (Crustacea: Decapoda: Palaemonidae) from Papua New Guinea.

A single ovigerous female specimen of marine shrimp of the family Palaemonidae collected from Madang Province, N.E. Papua New Guinea, was recognized as a representative of a new genus and species. Due to the presence of a sternal thoracic process, 3 pairs of posterior telson cuspidate setae, and the simple ambulatory dactyli, as well as the lack of branchiae on the two posterior maxillipeds, the new species clearly belongs to the assemblage of primarily free-living palaemonid taxa surrounding the speciose genera Cuapetes and Palaemonella. As the specimen possesses a short leaf-like rostrum, slender second pereiopods with small chelae similar to and not noticeably longer than the first pereiopods and very slender simple ambulatory dactyli, the specimen is without parallel within this assemblage and clearly represents a new genus. Its position within the Cuapetes/Palaemonella lineage of genera is also confirmed by a molecular comparison. The specimen is described and illustrated as a new genus and species.

Two new species of Aphanodactylidae (Crustacea: Decapoda: Brachyura) from the Ryukyu and Ogasawara Islands, Japan, with the establishment of a new genus

A new species of Takedactylus Naruse & Maenosono, 2012, and a new genus and species of Aphanodactylidae are described from Japan. Takedactylus compressus n. sp. is collected from Ogasawara Islands. This new species is distinct from the only congener, Takedactylus masatsunei, by the shapes of the carapace, third maxilliped and the ambulatory legs. Another new species, monotypic Lichtylus kaisha n. gen., n. sp., is distinct from all other aphanodactylid species, in generic level, in the shape and position of the palp of third maxilliped, relatively long and slender ambulatory legs, and a combination of other important characters, i.e. the contour of the carapace, the degree of gap between third maxillipeds, condition of the distoflexor corners of second to fifth ambulatory propodi, and relative length of ambulatory dactyli. The present study brings the number of aphanodactylid taxa to 7 genera and 15 species.http://zoobank.org/urn:lsid:zoobank.org:pub:0B01E38B-A542-4D22-966F-43B01E8D57D5http://zoobank.org/urn:lsid:zoobank.org:act:C1EAADE1-1774-4EED-B62D-8EB2BFDC1C32http://zoobank.org/urn:lsid:zoobank.org:act:195D7820-DB42-4BD6-AF66-F8C91A42B3FEhttp://zoobank.org/urn:lsid:zoobank.org:act:8A2C77F2-184D-4D7F-9317-03D6C8FC8D0D

Periclimenoides tyrannodentatus, a new species of symbiotic shrimps (Crustacea: Decapoda: Palaemonidae) from Taiwan.

A new species of sponge-endosymbiotic shrimps, Periclimenoides tyrannodentatus, is described and illustrated. The species is remarkable for its stout subspatulate first pereiopods chelae with lateral fan-shaped pectination on their dactyli. Due to this character and simple ambulatory dactyli, the new species is similar to the type species of the genus, P. odontodactylus. Another remarkable character is in the unique shape of the minor chela of the second pereiopods; the distal cutting edges of its compressed fingers are distinctly expanded and armed with quite impressive dentitions. An identification key to the three currently recognised species of the genus Periclimenoides is provided. The new species represents the first record of the genus Periclimenoides from Taiwan.

Enneophyllus ecarina, a new species of scaphopod shell dwelling hermit crab (Crustacea: Decapoda: Anomura: Paguridae) from deep-sea off the Ryukyu Islands, southern Japan

A second species of the pagurid genus Enneophyllus McLaughlin, 1997, E. ecarina n. sp., is described and illustrated on the basis of two specimens collected from the upper bathyal depths off Amami-ohshima Island, Ryukyu Islands, southern Japan. The new species is immediately distinguished from the sole known congener, E. spinirostris McLaughlin, 1997, from the Banda Sea, Indonesia, by the non-operculiform right chela and fewer ventral spiniform setae of the ambulatory dactyli. The type species of Enneophillus, E. spinirostris, was represented only by the male holotype, and examination of the female paratype of this new species enables documentation of female characteristics in the generic diagnosis. Like E. spinirostris, the new species inhabits scaphopod shells.

Two new species of Palapedia Ng, 1993 (Crustacea, Decapoda, Brachyura,Xanthidae) from the Persian Gulf.

Two new species of Palapedia Ng, 1993, are described based on material collected from Abu-Musa Island, Persian Gulf during the present study, from Bahrain by the 1937/38 Danish Expedition, and from the Saudi Arabian coast of the Persian Gulf by Michael Apel in 1992-1995. Palapedia persica n. sp. is distinguishable from its congeners by having distinctly large denticles on the upper margin of the palm and fingers of the chelae and anterior margin of the ambulatory dactyli, and by the markedly sickle-shaped dactylus of the ambulatory legs. Palapedia apeli n. sp. is similar to P. valentini Ng, 1993, and P. nitida (Stimpson, 1858), by having relatively smooth appendages.

A new species of false spider crab of the genus Elamena H. Milne Edwards, 1837 (Crustacea: Decapoda: Brachyura: Hymenosomatidae), from Davao Gulf, Philippines

A new species of hymenosomatid crab of the genus Elamena H. Milne Edwards, 1837, is described from the island of Samal, in the Davao Gulf, Mindanao, southern Philippines. Elamena samalensis sp. nov. belongs to the Elamena truncata species-group and is most similar to E. simplidenta Ng & Chuang, 1996, in the general form of the carapace and in the presence of only one subdistal tooth on the ambulatory dactyli. It can be distinguished from this species, however, by its more projecting rostrum, relatively longer and more slender ambulatory legs, and by the pointed apex of the female pleotelson.

Revision of Garthiella Titgen, 1986 (Crustacea: Decapoda: Brachyura: Xanthidae), with description of a new subfamily and a new species from the central Philippines

Examination of the holotype and other specimens of the type species of Garthiella Titgen, 1986, G. aberrans (Rathbun,1906), reveals that this genus must be excluded from Chlorodiellinae Ng & Holthuis, 2007, due to the absence of thediagnostic morphological features of the subfamily such as spoon-tipped chelae, prominent dactylo-propodal locks on theambulatory legs, and subdistal teeth on the ambulatory dactyli. Garthiellinae subfam. nov. is therefore established for thisgenus, as molecular and morphological evidence show that it cannot be classified in any other subfamily of XanthidaeMacLeay, 1838. A new species of Garthiella from the Bohol Sea, central Philippines, is also described. Garthiellasikatuna sp. nov. can be distinguished from G. aberrans by its relatively flatter and less granular carapace, more pronounced and curved anterolateral teeth, longer and more slender pereopods and by the form of the male first gonopods.

A note on an Ancylomenes (Crustacea: Decapoda: Pontoniinae) from the Siboga expedition

A major landmark in the taxonomy of the shrimps of the subfamily Pontoniinae was the publication of the Siboga Expedition monograph by Holthuis (1952). In this report Holthuis referred four lots of specimens to Periclimenes aesopius (Bate). This species is now placed in the genus Ancylomenes Okuno & Bruce (2010) as Ancylomenes aesopius (Bate, 1863) and is known only from Australian waters (South Australia and Western Australia). Through the kindness of Dr Dirk Platvoet it has been possible to re-examine these Siboga specimens. Re-examination showed that none can now be referred to Bate’s species which is distinguished from all other species of the genus by the presence of three or four post-orbital teeth on the anterior carapace (Bruce, 1977). Several species of Ancylomenes are represented in the Siboga material and Holthuis’s description of the material does not appear based on any specimen in particular. One specimen is however, readily distinguishable from the others by the unusually slender ambulatory dactyli. It is also distinct from all presently known species of Ancylomenes, and is herein designated as a new species and its characters described and illustrated.

Aphanodactylidae, a new family of thoracotreme crabs (Crustacea: Brachyura) symbiotic with polychaete worms

The pea crabs of the family Pinnotheridae De Haan, 1833, have traditionally been recognised on the basis of their simplified external morphology, modified third maxillipeds, and general habit of living in association with invertebrate hosts, usually bivalve molluscs. Recent morphological and molecular studies of Pinnotheridae show that it is not a natural group as traditionally conceived. The subfamily Asthenognathinae Stimpson, 1858, actually belongs in the Varunidae H. Milne Edwards, 1853, and the subfamily Tritodynamiinae Števčić, 2005, is part of the Macrophthalmidae Dana, 1851. However, several ‘pinnotherid’ genera that are superficially similar to asthenognathines and allied to Aphanodactylus Tesch, 1918, appear to form a discrete group, but lack the chief synapomorphy of Pinnotheridae, namely, the highly modified maxilliped 3. Moreover, Aphanodactylus and allies do not share synapomorphies with of any presently recognised thoracotreme family. A new family, Aphanodactylidae, is therefore established for Aphanodactylus, Gandoa Kammerer, 2006, Uruma Naruse, Fujita & Ng, 2009, and a new genus and species described herein, Gustavus mecognathus. Aphanodactylids (where known) are symbiotic with terebellid polychaete worms and share short, stout, ambulatory legs with one or more spines lining the flexor margins of the ischiomeri of at least some of the ambulatory legs; a row of distal flexor spines on the ambulatory propodi opposing a claw-like dactylus; very short ambulatory dactyli that are less than half the respective propodus length; and marked sexual dimorphism in which the female is distinctly wider than the male. The phylogenetic position of Aphanodactylidae remains to be determined but the morphology of the third maxillipeds and the position of the male gonopore suggests that it may belong in the Pinnotheroidea, to which it is tentatively assigned. Each genus of the Aphanodactylidae is diagnosed and illustrated, and a key to the genera provided.

A new hermit crab species of the genus Catapagurus (Crustacea: Decapoda: Anomura: Paguridae) from the Ryukyu Islands, southern Japan

A new species of the pagurid hermit crab genus Catapagurus A. Milne-Edwards, 1880, C. insolitus, is described and illustrated based on specimens from shallow waters in Okinawa Island, the Ryukyus. It belongs to an informal species group characterized by the possession of blade-shaped ambulatory dactyli, and is morphologically most similar to C. kosugei (Asakura, 2001). However, the new species is unique within the genus in having a multispinose antennal acicle, rarely seen in species of the family Paguridae.

A new species of Pagurixus (Crustacea: Decapoda: Anomura: Paguridae) from Southern Japan

A new hermit crab species of the pagurid genus Pagurixus Melin, P. fasciatus, is described from shallow rocky reefs of Japan. Fifteen congeners are known from the Indo-Pacific region. The new species is most similar to P. handrecki Gunn & Morgan, known from Western and southeastern Australia, but can be distinguished from the latter by the less setose antennal acicle, the dorsomesial margin of the right palm which is sharply carinate along the entire length, the fewer ventral spines on the ambulatory dactyli, and the sharp, smooth dorsolateral carina of the female right palm. Coloration in life is also different between the two species.

Neorhynchoplax yaeyamaensis, a new false spider crab (Decapoda: Brachyura: Hymenosomatidae) from the Yaeyama Group, the Ryukyu Islands, Japan

A new false spider crab, Neorhynchoplax yaeyamaensis (Decapoda: Brachyura: Hymenosomatidae) is described from the Yaeyama Group, the Ryukyu Islands, Japan. Neorhynchoplax yaeyamaensis is morphologically close to N. exigua and N. aspinifera, however, N. yaeyamaensis is easily differentiated from the latter two species by the dentition of the ambulatory dactyli, and the shapes of the carapace, male abdomen, and G1. Neorhynchoplax okinawaensis, also found in the Ryukyu Islands, differs from N. yaeyamaensis by the presence of a posterior lateral tooth, and the shape of the carapace, male abdomen, and G1.

A New Hermit Crab Species of Pylopaguropsis (Crustacea: Decapoda: Anomura: Paguridae) from the Western Pacific, and Supplemental Note on P. laevispinosa McLaughlin and Haig

Pylopaguropsis vicina, a new species of the Paguridae, is described and illustrated from southern Japan and Indonesia. This new species is most similar to P. laevispinosa McLaughlin and Haig, but is distinguished by the armature of the chelae and ambulatory dactyli, spination of the telson, and stripe pattern of the pereopods. Reexamination of specimens referred to P. laevispinosa by recent authors has shown these assignments to be incorrect. A brief supplemental description is provided for P. laevispinosa in order to clarify its systematic status. An amended key to species of the genus Pylopaguropsis is presented.

Polyonyx Bella, New Species (Decapoda: Anomura: Porcellanidae), From Taiwan, With Notes on Its Reproduction and Swimming Behavior

Polyonyx bella, new species, collected from tubes of the polychaete worm Chaetopterus variopedatus is described from Taiwan. This species resembles P vermicola Ng and Sasekumar of the P. sinensis group, but can be differentiated by the color patterns on the and chelipeds, the absence of a distinct sinus on the median part of the inner of the carpus of the major chela, the narrower ventral posterior projection of the carpus of the ambulatory leg, and the absence of a projection on the outer distal of the ischium, as well as possessing a proportionately broader and shorter propodus of the third maxilliped. Information on its reproduction and swimming behavior is also presented. An undescribed porcellanid crab of the genus Polyonyx Stimpson, 1858, belonging to the P. sinensis group (Johnson, 1958), was recently collected from tubes of the sedentary polychaete Chaetopterus variopedatus Renier, 1804, at the Kaomei tidal flat, Taichung County, western central Taiwan. The P sinensis group consists of eight species, including P. sinensis Stimpson, 1858, P. transversa Haswell, 1882, P. pedalis Nobili, 1905, P. utinomii Miyake, 1943, P. loimicola Sankolli, 1965, P. maccullochi Haig, 1965, P. haigae McNeill, 1968, and P. vermicola Ng and Sasekumar, 1993 (see Johnson, 1958; Ng and Sasekumar, 1993; Ng and Nakasone, 1993). Members of this group share the following characteristics: carapace broader than long; front narrow, trilobate; lateral margins of without spinules; anterior margins of cheliped merus and carpus unarmed; the outer parts of the palm (at least the ventral margins) hairy; ambulatory dactyli with dorsal spine (claw) much smaller than ventral spine and with two or three accessory spinules on ventral margin (Ng and Sasekumar, 1993). Johnson (1958) noticed that members of the P. sinensis group have a pronounced tendency toward commensalism. In this paper, a new species of Polyonyx is described and its reproduction and swimming behavior outside the host is discussed. Specimens examined in this study are deposited at the National Museum of Natural Science, Taiwan (NMNS); National Museum of Natural History, Smithsonian Institution (USNM); and the Zoological Reference Collection, School of Biological Sciences, National University of Singapore (ZRC).