Shape Of Telson Research Articles

Two new species of Pseudocrangonyx (Amphipoda: Pseudocrangonyctidae) from the hyporheic zones in South Korea

Pseudocrangonyx Akatsuka & Komai, 1922, is the most diverse group of subterranean amphipods in the groundwater communities of Far East Asia and is related to the biogeographic origin and evolution of subterranean amphipod fauna in the region. In this study, we describe two new subterranean species of pseudocrangonyctid amphipods, P. seomjinensis sp. nov. and P. danyangensis sp. nov., from the hyporheic zones in South Korea. These new species can be distinguished from their congeners by the length of the uropod 2 outer ramus, the number of accessory flagella of antenna 1, and telson shape. Additionally, we determined sequences of the nuclear 28S rRNA and the mitochondrial cytochrome c oxidase subunit I gene of the new species for molecular analyses.

A new species of the genus Pseudocrangonyx (Crustacea: Amphipoda: Pseudocrangonyctidae) from subterranean waters of Japan.

A new species of pseudocrangonyctid amphipod, Pseudocrangonyx asuwaensis, is described from subterranean water in a quarry on Mt. Asuwa "Nanatsuo-guchi", Fukui Prefecture, Japan. Pseudocrangonyx asuwaensis sp. nov. differs from its congeners in various morphological features, such as head without eyes, relative length of antennae 1, female antenna 2 without calceoli, length ratio of mandibular palp articles, setal numbers on maxillae 1 and 2 inner plates, absence of sternal gills, armature of urosomite 1, and shape of telson. Molecular phylogenetic analyses suggest that P. asuwaensis sp. nov. is clustered with P. komaii Tomikawa & Nakano, 2018, Pseudocrangonyx sp. 7 and Pseudocrangonyx sp. 8, and was the first of these species to diverge.

A new amphipod species of the bathyal genus Dautzenbergia Chevreux, 1900 (Amphipoda, Calliopioidea, Pontogeneiidae) associated with cold-water corals off Angola

A new species of pontogeneiid amphipod, Dautzenbergia concavipalma sp. nov., is described from cold-water corals off Angola. This is only the second observation of this genus in the South Atlantic. Important morphological characters in combination, which define the new species from its congeners, occur especially in the shape and size of gnathopod 1-2 propodus, the smooth pereopod dactyls, the shape of the basis of pereopod 7 and the telson shape with narrow cleft. The taxon is fully described and figured and is compared with known species of the genus. A key to Dautzenbergia species is also given.

A new species rises from beneath Florida: molecular phylogenetic analyses reveal cryptic diversity among the metapopulation of Crangonyx hobbsi Shoemaker, 1941 (Amphipoda: Crangonyctidae)

The phylogenetic structure of 23 populations of Crangonyx hobbsi, a stygobitic amphipod species endemic to the Floridan aquifer, is detailed. Molecular genetic analyses (based on three genes the nuclear 18S rDNA, 28S rDNA, and mitochondrial 16S rDNA) point to the presence of at least two phylogenetic clades within the aquifer. These clades align into two major zoogeographic regions, the Northern Suwannee River Basin and the Coastal and Central Lowlands in the Florida peninsula. Three species delimitation models indicate that the Northern Suwannee River Basin Clade represents a species level differentiation from C. hobbsi sensu stricto. Morphological analyses support the molecular analyses, revealing the presence of several taxonomically significant differences between the two species, including presence/absence of calceoli on the second antennae of males and differences in telson shape in both sexes. Additionally, the molecular diversity of C. hobbsi sensu stricto was shown to be surprisingly variable, suggesting the potential presence of additional diversity within the taxon.

Two new species of the genus Lepidophthalmus (Decapoda, Axiidea,Callianassidae) from coastal Pacific waters of Central America.

Two new species of intertidal ghost shrimp are described from coastal Central American habitats of the eastern Pacific Ocean, bringing the total known membership of the genus to 18 species. Lepidophthalmus natesi sp. nov. from Colombia and Nicaragua shares with Lepidophthalmus panamensis sp. nov. from Colombia and Panama the lack of extensive ventral pleomere armor, especially in lacking a median ventral sclerite on the second pleomere. The absence of this plate is also a character of the eastern Pacific species L. rafai Felder & Manning, 1998, but the two new species differ from it in telson shape. Ventral armor including this plate is present in Lepidophthalmus bocourti (A. Milne-Edwards, 1870) and L. eiseni Holmes, 1904 which occur sympatrically with L. natesi sp. nov. in eastern Pacific tropical estuaries. As also known for at least L. bocourti, L. natesi sp. nov. invades and densely colonizes penaeid shrimp aquaculture ponds in regional estuarine settings. Individuals of L. panamensis sp. nov. are of smaller body size but also may be densely concentrated, especially in clayey substrates including those adjacent to intertidal rocks. Despite their similarities in the pleon and shape of the telson, the species can be readily separated by dentition of the cheliped fingers, relative length of the minor chela fingers, the second pleopod appendix of mature males, and egg size. The large eggs of L. panamensis sp. nov. suggest extremely abbreviated development. Characteristic coloration is described for both new species.

Cyathura odaliscae, a new species of anthurid isopod (Crustacea: Peracarida) from a brackish habitat on the Pacific coast of Costa Rica.

During a preliminary survey of a brackish mangrove habitat in the Terraba River delta on the Pacific coast of Costa Rica, several adult and subadult specimens of a new anthurid isopod, Cyathura odaliscae n. sp. were discovered. The specimens were collected from decaying wood in low salinity conditions (<5‰). The unique shape and complexity of the male copulatory stylet of C. odaliscae distinguishes it from the other 22 species for which males have been described. A combination of other characters (e.g., morphology of the mouth parts, body setation, shape of telson and first pereopod) is used to distinguish the female from the others within the genus. Illustrations of the known male copulatory stylets for the genus and a table listing diagnostic information, depth ranges, and general distribution for the 32 currently recognized species of Cyathura are provided.

The larval development of the mud shrimp Upogebia yokoyai Makarov, 1938 (Decapoda: Gebiidea: Upogebiidae) reared under laboratory conditions

Larval development of the mud shrimp Upogebia yokoyai Makarov, 1938 (Decapoda: Gebiidea: Upogebiidae) is described and illustrated for the first time from material reared in the laboratory. The development includes four zoeal stages and a megalopa. At 20–22°C the megalopa was attained 16 days after hatching. The zoeae of U. yokoyai are distinguishable from those of the sympatric species Upogebia major and Upogebia issaeffi, inhabiting Russian waters of the Sea of Japan, by the presence of two pairs of spines (posterolateral and posterodorsal), each on the fourth and fifth pleonal somites. The megalopa of U. yokoyai differs in the length of the rostral spine, shape of telson and number of antennular aesthetascs.

A New Leanchoiliid Megacheiran Arthropod from the Lower Cambrian Emu Bay Shale, South Australia

The Leanchoiliidae is well-known from abundant material of Leanchoilia, from the Burgess Shale and Chengjiang Konservat-Lagerstatten. The first Australian member of the group is Oestokerkus megacholix gen. et sp. nov., described from the Emu Bay Shale (Cambrian Series 2, Stage 4), at Buck Quarry, Kangaroo Island, South Australia, and is intermediate in age between the well known leanchoiliid species from the Burgess Shale and Chengjiang. Phylogenetic analysis of “short great appendage” arthropods (Megacheira) in the context of the chelicerate stem group resolves the Australian species as sister to Burgess Shale, Utah, and Chengjiang Leanchoilia species, but most readily distinguished from Leanchoilia and Alalcomenaeus by a different telson shape, interpreted as being forked, widening distally, and with a few dorsally curved spines at the posterior angle. Leanchoiliid interrelationships are stable to alternative character weights, and Megacheira corresponds to a clade in most analyses.

Larval stages of Pandalus borealis

Our studies of larval growth of Pandalus borealis revealed that the available literature for identification of the larval stages was inconsistent and thereby difficult to use. We present a robust key for identification of larval stages of P. borealis, that separates the five zoea stages (ZI–ZV), one megalopa stage (M) and the post-larva (P) in the North Atlantic. Through extensive morphometric measurements and analysis we have developed this key for the identification of larval stages that will serve as a helpful tool in future P. borealis larvae research. The key is based on the functional development of the larvae with emphasis on the telson shape, and on distinct morphological characteristics in each stage. We studied live and preserved larvae, both reared and wild caught, originating from North Norwegian fjords and the Barents Sea. The literature study suggests differences, in morphology and size, between larval stages for the Atlantic (P. borealis) and the Pacific (P. eous) species or subspecies.

A New Species of the Genus Burmoniscus (Isopoda, Oniscidea, Philosciidae) from Ko Phuket, Thailand

A new species, Burmoniscus phuketensis, is described from Ko Phuket, Thailand. The new species belongs to the group characterized by male pereopods 1 and 2 with enlarged and flattened carpi, including B. coecus (Budde-Lund, 1895), B. ferrarai (Schumalfuss, 1983), B. mossambicus (Ferrara and Taiti, 1985), B. rowei Taiti and Manicastri, 1988, and B. rakataensis Green, Ferrara and Taiti, 1990. Among them, this new species resembles B. coecus and B. rakataensis in the pigmentless body and the shape of pereonite 7 epimeron with acute postero-lateral corner, but is easily distinguished from both specie by the shape of telson. While the eyes are absent in B. coecus, they are present in this new species.

A morphometric approach to the geographic variation of the terrestrial isopod speciesArmadillo tuberculatus(Isopoda: Oniscidea)

The terrestrial isopod species Armadillo tuberculatus Vogl, 1876 (Crustacea, Isopoda, Oniscidea) is a widely polymorphic species distributed in the south-central Aegean region (Greece) with a different morph on each island. Variation consists in coloration, size of cuticular tubercules, shape of telson and the shape of the male first pleopod exopodite (secondary sexual character of taxonomic importance). We studied the allometric growth of a cuticular tubercule in 17 populations (for both male and female individuals) and the shape variation of the first male pleopod exopodite in 10 populations using Elliptic Fourier Analysis, in order to test for patterns of intraspecific variation and possible relationships between morphs. In addition, Thin Plate Spline analysis was used for the calculation of the minimum bending energy between different exopodite shapes, which was then used for estimating the minimum spanning network (MSN) connecting them. The different allometric growth rates of the tubercule among island groups were significantly related to island latitude and climatic factors. On the other hand, the clustering of islands and the MSN based on male exopodite shape differences were not related to the palaeogeography of the Aegean region or to the present geographic distances of islands. These results are interpreted as evidence for non-adaptive radiation of the morphs.

A new species of Uristes Dana, 1849 (Amphipoda: Lysianassoidea: Uristidae) from the Beagle Channel, Argentina

A new species of Uristes Dana, 1849 (Uristidae) collected from shallow waters in the Beagle Channel, Argentina, is described and illustrated. Uristes yamana n. sp., the third species of this genus reported for the Magellan area, is closely related to U. serratus Schellenberg 1931, principally by the possession of an unusual stout gnathopod 1 propodus. Both species can be separated by telson shape and relative setosity of uropod 3. The geographical distribution of U. gigas Dana, 1849 is also emended.

PTERYGOTIDS (CHELICERATA; EURYPTERIDA) FROM THE SILURIAN VERNON FORMATION OF NEW YORK

Pterygotus monroensis from the Pittsford and Harris Hill members of the Silurian Vernon Formation, New York State, USA, is here assigned to Erettopterus osiliensis, previously known only from Saaremaa, Estonia, based on new material (carapaces, chelicerae, a prosomal appendage VI, several metastoma, genital opercula with appendages, an almost complete opisthosoma, and several bilobed telsons), and re-examination of the original specimens. Telson morphology indicates assignment to Erettopterus or Truncatiramus, but the differences between these two genera are here interpreted as insignificant, and all species are treated as belonging to Erettopterus. The much rarer Pterygotus? sarlei n. sp., a possibly basal pterygotid, also from the Pittsford Member, is based on two telsons with pterygotid-like marginal cuticular sculpture. The telson shape is unlike that of any other adult pterygotid; it is relatively similar to juvenile pterygotids and Slimonia, but lacks the long posterior spine found in Slimonia. These systematic revisions have implications for other pterygotid taxa. Pterygotus impacatus, from Estonia, is a junior synonym of E. osiliensis. P. waylandsmithi, from slightly higher in the Vernon Formation, and is transferred to Erettopterus based on similarities of the chelicerae to E. osiliensis.

Phylogenetic analysis of the Squilloidea (Crustacea:Stomatopoda)

Squilloidea is the most speciose of the stomatopod superfamilies and comprises more than 40 genera. Until 2001, three families were recognised: two extant (Harpiosquillidae, Squillidae) and one extinct (Ursquillidae). Recent studies, however, suggested that Harpiosquillidae is nested among other squillids and was thus synonymised with Squillidae. Interrelationships of all squilloid genera are studied by cladistic analysis based on somatic morphology. Results are used to assess the familial classification and investigate the ‘shape’ of squilloid evolution. The phylogeny of the squilloids shows general trends in the armature of the raptorial claw, increased dorsal carination, a tendency for bilobation of the lateral processes of the exposed thoracic somites, and a change in telson shape from trianguloid with movable submedian teeth, to quadriform with fixed submedian teeth. Harpiosquilla Holthuis, 1964 is deeply nested among other squillid genera, supporting the recent synonymy of the Squillidae and Harpiosquillidae. Characters of the late Cretaceous Ursquillidae show that it is highly derived and is therefore synonymised with Squillidae. Although the antiquity of Ursquilla Hof, 1998 does not show it to be a basal or stem-lineage squilloid, it does show that the squilloids had already undergone significant diversification by the end of the Cretaceous. Species of most squilloid genera are regionally restricted, either to the Indo-west Pacific or Atlanto-east Pacific. Only Alima Leach, 1818, Cloridopsis Manning 1968b, and Pontiosquilla Manning, 1995 are represented in both regions.

Two new species of the genusburmoniscusCollinge, 1914 (crustacea, isopoda, oniscidea) from Palawan island, the Philippines

Two species of the genus Burmoniscus Collinge, 1914 (Philosciidae), B. philippinensis and B. palawanensis from Palawan Island, the Philippines are described as new. In the family Philosciidae, only a single species, Pseudo‐typhloscia alba (Dollfus, 1898), has been recorded from the Philippines. Two species of the genus Burmoniscus Collinge, 1914 (Philosciidae), B. philippinensis and B. palawanensis from Palawan Island, the Philippines are described as new. B. philippinensis is distinguished from its congeners by the shape of telson with straight sides and slightly protruding distal part with acute apex, while B. palawanensis by its peculiar shape of male pleopod 1 endopod.

The post-larval development of the shore crabOcypoda platytarsis M. Edwards andOcypoda cordimana desmarest

1. The megalopae ofO. platytarsis andO. cordimana were for the first time successfully reared in the laboratory to the first crab stage. 2. The megalopae of the two species differ in size, colour, shape of telson and number of setae on the last pleopod. 3. The megalopae of both species burrow in the sand of the intertidal zone before metamorphosing into the first crab stage. 4. A key for the identification of the megalopae and the first crab stages of the two species is given.