Two new species of the genus Anisomysis (Anisomysis) (Crustacea,Mysida, Mysidae) from coral reef waters in Thailand

Two new species of Anisomysis Hansen, 1910 (Mysida, Mysidae), Anisomysis (Anisomysis) spinaintus sp. n. and Anisomysis (Anisomysis) phuketensis sp. n., from coral-reef waters in Thailand are described. Anisomysis (Anisomysis) spinaintus, collected in the Chaolao Beach, Chanthaburi Province, is distinguished from the closely allied species Anisomysis (Anisomysis) incisa Tattersall, 1936, and Anisomysis (Anisomysis) hawaiiensis Murano, 1995, by the presence of 6–9 spines on the apical cleft of telson, which are absent in the latter two allied species. The new species can also be distinguished from Anisomysis (Anisomysis) aikawai Ii, 1964, by the presence of a deep telson cleft and a large number of spines on the lateral margin of telson. Anisomysis (Anisomysis) phuketensis sp. n., collected in Ko Lon, Phuket, is distinguished from the allied species Anisomysis (Anisomysis) robustispina Panampunnayil, 1984, by having a short telson and a pair of long spines on the apical part of the telson. Keys to the subgenera and species of Anisomysis, including the two new species, are presented.     

Two new species belonging to the genus Anisomysis (Crustacea, Mysidacea) and a new record of Anisomysis bipartoculata from the Indian Ocean

This paper deals with three species of the genus Anisomysiscollected from the South West coast of Australia of which A.gracilis and A. robustispina are new to science and A. bipanocularais reported for the first time from the Indian Ocean.     

Rhopalophthalmus constrictus sp. nov. and Australomysis reubeni sp. nov. (Crustacea-Mysidacea) from south-west Australian waters

Two new species of mysids are described. Rhopalophthalmus constrictussp. nov. is unique in having a well-produced triangular rostralplate, pleural plates on the anterior five abdominal somitesand prominent constriction at the distal end of the telson.Australomysis reubeni sp. nov. is distinguished by its rostrum,telson, fourth male pleopod and modified setae on the carpopropodalsegment.     

Descriptions of five new species of Haplostylus (Mysidacea-Crustacea) from South West Australia

Five new species, Haplostylus flagelliforma sp. nov., H.similissp. nov., H.multispinosus sp. nov., H.uthupus sp. nov. and H.disparsp. nov., are described from the south-west coast of Australia.These new species are distinguishable from each other and fromthe other allied species by the structure of the pleopods ofthe male, and by the armature of the telson and the uropods.     

Two new species of Siriella (Crustacea--Mysidacea) from the southwest coast of Australia

Two new species of Siriella, S.australiensis sp. nov. and S.spinulasp. nov., are described here. Siriella australiensis is distinguishedby the character of the third and fourth pleopods of the male.Siriella spinula is characterized by the short frontal spineof the labrum and the short linguiform telson showing sexualdimorphism.     

The zoeal stages and megalopa of Portunus rubromarginatus (Lanchester) (Decapoda: Portnnidae), reared in the laboratory

The present state of knowledge concerning Portunus larvae isreviewed, and the three zoeal and the megalopa stages of P.rubromarginatus are described and figured. Details of appendagesetation are tabulated. This species is unusual amongst knownPortunus spp. in having only three zoeal stages and, like otherPortunus spp. but in contrast with other Portuninae, it has4 + 4, or 4 + 1 + 4, setae on the posterior telson border. When compared with larvae of the five other Indo-West PacificPortunus species whose larvae are known P. rubromarginatus zoeaeare readily distinguished from all, except P. hastatoides, usingthe key features given by Kurata (1975). Comparison was madebetween first zoeae of these two species, and also of P. pelagicusand P. sanguinolentus, using larvae reared by the authors. Itwas found telson characters alone allow distinction betweenlarvae of these four species. These characters are tabulated. P. rubromarginatus megalopae differ from those known for congenitorsin having a large spine on the uchium of the first pereiopod,but not on the carpus, and in having relatively very small sternalcornuae. Several of these features disagree with those previously thoughtto characterise larval Portuninae or Portunus species.     

Rostromysis bacescuii gen. et sp. nov. and Megalopsis den-ticauda gen. et sp. nov. (Crustacea -- Mysidacea) from the south-west coast of Australia

Rostromysis bacescuii gen. et sp. nov. and Megalopsis denlicaudagen. et sp. nov. belonging to the tribe Leptomysini are describedfrom the south-west coast of Australia. The characters uniqueto the genus Rostromysis are the unusually long club-shapedrostrum and the large delicate lamella-like pleopods of thefemale, thus easily distinguishing it from the allied generaTenagomysis and Doxomysis. The genus Megalopsis is closely alliedto Leptomysis, Prionomysis and Promysis but is readily distinguishablein having a short linguiform uncleft telson with a pair of medianplumose setae.     

A new species of pelagic amphipod of the genus Lestrigonus (Crustacea: Amphipoda: Hyperiidea: Hyperiidae) from eastern Australia

A new species of pelagic amphipod, Lestrigonus ducrayi sp. nov.,from eastern Australia, is described and illustrated. It isvery similar to Lestrigonus bengalensis Giles, 1887, but isreadily distinguished by a relatively shorter telson (aboutone-third peduncle uropod 3) and, in mature males, pereonites1–5 are fused as in females. The two species often occurtogether in the same plankton sample; the new species beingmore abundant inshore, although both species seem to preferinshore waters. A key to the species of Lestrigonus is provided.     

The first-stage zoeas of Carpilius convexus (Forskal, 1775) and Carpilius maculatus (Linnaeus, 1758) (Crustacea: Decapoda: Brachyura: Xanthoidea: Carpiliidae): an example of heterochrony

The first-stage zoeas of Carpilius convexus (Forskål,1775) and Carpilius maculatus (Linnaeus, 1758) are describedand fully illustrated. Both these Indo-West Pacific speciesexhibited a unique xanthoidean character for the basis of thesecond maxilliped, which possesses five (arranged 1,1,1,2) setaeinstead of the expected four (arranged 1,1,1,1). A comparisonwith the zoeal stages of Carpilius corallinus (Herbst, 1783)as reported by Laughlin et al. (Laughlin et al., 1983) revealedmarked differences including the possession of carapace lateralspines (v. absent in C. convexus only), the subterminal setationof the distal maxillule endopod segment with two subterminalsetae (versus one subterminal seta in Indo-West Pacific species),the terminal setation of the distal maxillule endopod segmentwith four setae (versus three setae in C. convexus only), twolateral spines on the telson (versus three in Indo-West Pacificspecies) and the number of zoeal stages. The first-stage zoeasof the two Indo-West Pacific species appear to have hatchedin a more advanced state of development than those of C. corallinus,and the expression of a number of characters has been accelerated(early onset). In fact, the zoeal stages of both Indo-West Pacificspecies and carpiliid species appear to be abbreviated becausethe first zoeas are considered to be equivalent to the third-stagezoeas of C. corallinus.     

Foraging behavior of the predaceous cladoceran, Leptodora kindti, and escape responses of their prey

Using silhouette video photography we have made the first quantitativeobservations of foraging behavior in Leptodora kindti, a predaceouscladoceran (Haplopoda). Leptodora swims with a mean velocityof 13.4?4.0 mm s^–1 and initiates an attack only upon directcontact with potential prey. The attack sequence is as follows:Leptodora swims randomly through the water column with all fivepairs of thorac appendages spread to form a ‘feeding basket’and, seemingly by chance, encounters prey. Shortly after preymake contact with any part of Leptodora's body (usually ventral),the abdomen is rapidly pulled forward, clamping itself underthe feeding basket so that the telson closes it at the posteriorend. The duration of this movement is always the same and weconclude that it is an indiscriminate reflex. If the prey isencountered anywhere but a short distance directly in frontand slightly below the Leptodora, it is not captured. The speedof copepod escape responses effectively allows them to avoidcontact with the predator. Daphnia's escape response, particularlythat of juveniles, is slower and leaves them far more susceptibleto Leptodora predation.     

Integumental organs of the phyllosoma larva of the rock lobster Jasus edwardsii (Hutton)

The external morphology and distribution of the integumentalorgans of the final-stage phyllosoma of the rock lobster Jasusedwardsii were examined. Seven types of organs were recognizedon the integument of the body trunk, antennules and antennae:plumose setae, simple setae, porous setae, aesthetasc setae,simple pores, dorsal cuticular organs and dome-shaped structures.The plumose setae and simple pores were abundant on the dorsalsurface of the cephalosome, abdomen and telson. The dorsal cuticularorgans were present only on the dorsal surface of the cephalosome,and the aesthetasc setae were restricted to the antennule. A comparison of the morphology of these organs with the senseorgans of other decapods with known function suggests that thedorsal surface of the body trunk is one of the major sites ofreception of near-field water movement in the Jasus phyllosoma.     

Function and hydrostatics in the telson of the Burgess Shale arthropod Burgessia

Burgessia bella is a characteristic Burgess Shale arthropod (508 Ma), but the unusual preservation of its telson in both straight and bent modes leads to contradictory interpretations of its function. A reinvestigation of the fossil material, including burial attitudes, combined with a comparison with the decay sequence and mechanics of the telson in living Limulus, demonstrates that the telson of Burgessia was flexible in its relaxed state but could be stiffened in life. Evidence of fluid within the telson indicates that this manoeuvrability was achieved by changes in hydrostatic pressure and muscular control. The dual mode in the Burgessia telson is, to my knowledge, the first documented among fossil arthropods. It indicates that the requirement for a rigid telson, which is resolved by a thick sclerotized cuticle in most arthropods, may first have been achieved by hydrostatic means.     

Complete larval development of the hermit crabs Clibanarius aequabilis and Clibanarius erythropus (Decapoda: Anomura: Diogenidae), under laboratory conditions, with a revision of the larval features of genus Clibanarius

The complete larval development (four zoeae and one megalopa) of Clibanarius aequabilis and C. erythropus, reared under laboratory conditions, is described and illustrated. The larval stages of the two northeastern Atlantic Clibanarius species cannot be easily differentiated. Their morphological characters are compared with those of other known Clibanarius larvae. The genus Clibanarius is very homogeneous with respect to larval characters. All Clibanarius zoeae display a broad and blunt rostrum, smooth abdominal segments and an antennal scale without a terminal spine. Beyond the second zoeal stage, the fourth telson process is present as a fused spine, and the uropods are biramous. In the fourth larval stage all species display a mandibular palp. The Clibanarius megalopa presents weakly developed or no ocular scales, symmetrical chelipeds, apically curved corneous dactylus in the second and third pereiopods, and 5–11 setae on the posterior margin of the telson. Apart from the number of zoeal stages, Clibanarius species may be separated, beyond the second zoeal stage, by the telson formula and the morphology of the fourth telson process.     

Additions to the Mysid Fauna (Crustacea: Mysidacea) from Coastal Waters of Oman, Including Descriptions of Two New Species

Two new species of mysid shrimps are described from shallow coastal waters of Northern Oman. Haplostylus quadrispinosus sp. nov. is primarily distinguished from allied species by the arrangement and size of lateral spines on the telson. The form of the telson and exopod of the 4th male pleopod characterize a second new species, Anisomysis arabica sp. nov. A third species Mysidopsis kenyana, was previously recorded only from East Africa and its presence in samples considerably extends its geographical distribution. Four mysid species are now documented from coastal waters of Oman.     

STRUCTURE OF LIMULUS STRIATED MUSCLE : The Contractile Apparatus at Various Sarcomere Lengths

The musculature of the telson of Limulus polyphemus L. consists of three dorsal muscles: the medial and lateral telson levators and the telson abductor, and one large ventral muscle; the telson depressor, which has three major divisions: the dorsal, medioventral, and lateroventral heads. The telson muscles are composed of one type of striated muscle fiber, which has irregularly shaped myofibrils. The sarcomeres are long, with discrete A and I and discontinuous Z bands. M lines are not present. H zones can be identified easily, only in thick (1.0 µm) longitudinal sections or thin cross sections. In lengthened fibers, the Z bands are irregular and the A bands appear very long due to misalignment of constituent thick filaments. As the sarcomeres shorten, the Z lines straighten somewhat and the thick filaments become more aligned within the A band, leading to apparent decrease in A band length. Further A band shortening, seen at sarcomere lengths below 7.4 µm may be a function of conformational changes of the thick filaments, possibly brought about by alterations in the ordering of their paramyosin cores.     

Aspects of embryonic and postembryonic development of the Japanese freshwater crayfish Cambaroides japonicus (Crustacea, Decapoda) including a hypothesis on the evolution of maternal care in the Astacida

Little is known about the biology of the East Asian freshwater crayfish of the genus Cambaroides. Furthermore, the phylogenetic relationships of Cambaroides are controversial. To gain more information about East Asian crayfish and to shed some light on the phylogeny and evolution of freshwater crayfish, some aspects of the embryonic and postembryonic development of the Japanese freshwater crayfish species Cambaroides japonicus are described. The general appearance of the embryo and the growth zone consisting of about 40 ectoteloblasts correspond with the apomorphic pattern described for all other freshwater crayfish species. The occurrence of eight mesoteloblasts is a typical malacostracan character. In addition to the occurrence of freshwater crayfish apomorphies, such as a telson thread, the postembryonic development of C. japonicus follows the ground pattern of the Northern Hemisphere Astacoidea. In particular, some characteristics are in common with the postembryonic development of the Astacidae. These concern the shape of the telson of the juvenile stage 1 and the occurrence of plumose telson setae in juvenile stage 2. Furthermore, the recurved hooks of the hatchlings are lost in the juvenile stage 2, indicating an early independence of the juveniles from the mother. On the other hand, the early appearance of a spermatheca (annulus ventralis) is shared between C. japonicus and the other (American) Cambaridae. The hypothesis is developed that the evolutionary success of the different freshwater crayfish taxa might be related to the stepwise extension of maternal care as an adaptation to the freshwater environment.     

Aberrant individuals ofNeomysis integer and other Mysidacea: Intersexuality and variable telson morphology

Intersexuality in the mysidNeomysis integer is described from samples collected in the Elbe (north Germany), Eems-Dollard (north Netherlands), Westerschelde (south-west Netherlands) and Gironde (southwest France) estuaries. Individuals which had an irregularly shaped or nearly symmetrically rounded telson, rather than a typically truncated one, were also recorded from the four populations studied. A culture experiment with damaged specimens revealed that all types of abnormal telson morphology found in the field can result from regeneration of damaged parts. It is concluded that both intersexuality and aberrant telson morphology are widespread phenomena among estuarineN. integer populations. Both abnormalities seem to be rare in the other common mysid species in the study area: only one intersexualGastrosaccus spinifer and oneSchistomysis kervillei with an aberrant telson were recorded.     

Doxomysis algoaensis, a new mysid species (Crustacea: Mysidacea) from Algoa Bay (South Africa)

Doxomysis algoaensis sp.nov. is described from Algoa Bay, South Africa where it is common in nearshore marine waters just beyond the breaker line. D. algoaensis sp.nov. is morphologically similar to D. australiensis, but can readily be distinguished by the shape and armature of the telson and the length of the exopod of the fourth male pleopod. The apical cleft is one fifth the telson length in the former species and one third the length in D. australiensis. The telson apex on each side of the cleft is also armed with five and four stout spines in the two species, respectively. In D. australiensis, the exopod of the fourth male pleopod is almost three times the length of the endopod; in D. algoaensis sp.nov., the exopod is only slightly longer than the endopod. Other distinctive features of D. algoaensis sp.nov. include the maxillary palp, which is only slightly broader than long and the greater number of spines on the endopod of the uropod.