The structure and organization of the gills of gammaridean Amphipoda

The gills of gammaridean amphipods consist of epipods on the coxa of peraeopods 2 to 6 and an exopod on the basis of peraeopod 7. Bilobed coxal gills are found on Gammaracanthus spp., lysianassoids and a few other species. Pleated and phyllobranchiate gills are found in some lysianassoids, dexaminoids and eusiroids. The trend in amphipods is towards a reduction in gill area through a loss of the outer lobe, simplification in gill structure, and a loss of individual gills. The reduction in gill area is associated with a decrease in body size.     

Crymostygidae,a new family of subterranean freshwater gammaridean amphipods (Crustacea) recorded from subarctic Europe

Crymostygidae, a new family of gammaridean amphipods (Crustacea), is described from Iceland. The family is based on a new species and genus, Crymostygius thingvallensis, found in spring inlets feeding Lake Thingvallavatn, south-west Iceland. This is the first report of a stygobiont freshwater amphipod from Iceland and the northern-most report of a stygobiont species in Europe. The species apparently survived Pliocene and Pleistocene glaciations in the groundwater of a porous lava and may have persisted in Iceland for several million years.     

New and unusual abyssal gammaridean Amphipoda from the north-east Pacific

Seventeen species of gammaridean amphipods were identified from sediment trap collections in the north-east Pacific, off the central California coast from depths of 3450–4050 m. Four new monotypic genera, Anisocallisoma (Family Scopelocheiridae), Triquetramana (Family Eusiridae), Octomana and Macroarthrus (Family Pardaliscidae) and eight new species, Cyphocaris latirama, Schisturella spinirama, Paracallisoma spinipoda, Anisocallisoma armigera, Triquetramana brevipalpa, Octomana hadromischa, Macroarthrus victoriae, Oedicerina denticulata are described. A number of new and unusual morphological characteristics were discovered, most notably in the family Pardaliscidae, where two of the new genera belong. In addition, new distributional and/or depth records are established for the following species: Procyphocaris indurata (K. H. Barnard, 1925), Scopelocheiropsis abyssalis Schellenberg, 1926a, Rhachotropis distincta (Holmes, 1908), Cleonardo biscayensis Chevreux, 1908b, Cleonardo macrocephala Birstein and Vinogradov, 1955, Pardaliscopsis tenuipalpa Chevreux, 1911, Halice aculeata Chevreux, 1912 and the genus Oedicerina Stephensen, 1931. In order to assist future identification, the new species are fully diagnosed and illustrated. Three tables for comparing characters and a key to the species of Oedicerina are also provided. Additional morphological information and figures are given for existing species that hitherto were poorly described and illustrated. Sediment traps normally employed in studying organic matter fluxes are herewith used for the first time as a source of deep-sea amphipods, and this potentially exciting method is discussed. The high proportion of new taxa illustrates the deficiencies in our knowledge of the abyssal fauna in this area, emphasizes the importance of continued collecting in the deep-sea, and demonstrates the need for increased taxonomic effort to document this diversity.     

New genera of Bogidiellidae (Amphipoda: Gammaridea) from SW Pacific and Mediterranean marine caves

Two new genera and species of the stygobiont gammaridean amphipod family Bogidiellidae are described from anchialine or fully marine subterranean habitats in Mediterranean and SW Pacific Islands. Fidelidiella pectinata, from a littoral cave in Lifou (Loyalty Islands), differs from any other bogidiellid known thus far by the presence on the left mandible of a modified lacinia which is hypertrophied and expanded laterally, and by the possession of a transverse row of strong rounded processes on the anterior side of the distomedial corner of the fourth segment of the maxillipedal palp. This is the most easterly record of bogidiellid amphipods in the SW Pacific. Racovella uniramea, discovered in a Mallorcan anchialine cave, is remarkable among the Bogidiellidae in exhibiting a combination of only six distal spines on the basal endite of the maxillule, and presence of coxal gills on pereopods 3–6. We place particular emphasis on the determination of segmental homologies of all limbs and on the resolution of fine‐scale integumentary details, in order to provide a sound basis for future comparison with other family members.     

Effects of temperature and salinity on survival and growth of the amphipod Hyale crassicornis (Gammaridea,Hyalidae)

This study explored the survival and growth of the marine amphipod Hyale crassicornis under different conditions of ambient temperature and salinity in the laboratory. In 96‐h exposure experiments at a salinity of 30, H. crassicornis tolerated temperatures between 6 and 28°C (>90% survival). The 96‐h LT₅₀ value (median lethal temperature) at high temperature range for the amphipod was 32°C. The values at low temperature range for adults and juveniles were 3.2 and 4.2°C, respectively, indicating that adults have a higher tolerance to low temperature than juveniles. At 25°C, the amphipods tolerated salinities between 10 and 50 (with >80% survival in 96?h). The 96‐h LS₅₀ values at high and low salinity ranges were 56 and 2, respectively. Growth of the juveniles from instars 1 to 6 was determined under different combinations of temperature and salinity. Growth rate of juveniles cultured at 25°C and a salinity of 20 was the highest (0.114?mm?day^?1) among the combinations of 15–25°C and 10–40 salinity. The moult increment of body length was affected by both temperature and salinity. Yet the intermoult duration of the amphipods was affected by temperature only but not by salinity.     

A new species of Valettia (Crustacea: Amphipoda) and the relationship of the Valettidae to the Lysianassoidea

The family Vallettidae is re-established to accommodate Valettia coheres Stebbing, 1888 and V. hystrix sp. nov. Although closer to the Lysianassoidea than to any other gammaridean superfamily, characters of the mandible, maxillae, gnathopods and oostegites preclude membership of that superfamily. Further assessments of the Valettidae and other family groups peripheral to the Lysianassoidea will be required before formal high-level classification can be established.     

Deep-water amphipods from the Catalan Sea slope (western Mediterranean): Bathymetric distribution,assemblage composition and biological characteristics

Deep-water epibenthic/suprabenthic species of Amphipoda were studied in the Catalan Sea (north-western Mediterranean) at depths from 389 to 1859 m. In four cruises 20 samples were effected during 1991–1992, covering four different seasonal periods (March, April, July and December). A minimum total of 82 species was collected. Ampelisca uncinata and Eusirus leptocarpus were newly recorded as components of the Mediterranean fauna while three other species collected (Bathymedon sp. A, Autonoe sp. and Rhachotropis cf. gracilis) had distinct possibilities to be new species. The Gammaridae Carangoliopsis spinulosa and the Oedicerotidae Synchelidium maculatum were the two main dominant species on the upper slope level (389-506 m). On the middle slope (between 549-601 m), dominance by any few species was not apparent; the Eusiridae Rhachotropis glabra and R. caeca together with Bathymedon acutifrons, Scopelocheirus hopei and Andaniexis mimonectes were the most abundant species. On the lower slope, at depth below 1000 m, R. caeca was the largely dominant species. The highest species richness (S_T) was reported at intermediate depths over the middle slope (63 species), decreasing with depth increase, and being particularly low at 1808–1859 m (19 species). Total amphipod densities were also higher at the upper and middle slope levels (1760.2–2613.9 amphipods/1000 m³) than below 1000 m (376.4–679.2 amphipods/1000 m³). The low swimming coefficients (K_t) of bathyal Gammaridea, ranging between 0 and 0.336, indicate their relationship to the water-sediment interface although interespecific differences in K_t in relation to species size were also reported. Almost all the dominant amphipods had recruits (=smallest juveniles) in two or three of the three seasons sampled (mainly in March and December), and the smallest juveniles were often only abundant in two of these seasons. This indicates that most species had more than one generation per year, probably suggesting bivoltinism, a commonly adopted biological strategy among intertidal, littoral and shallow water amphipods, as the commonest strategy adopted by the mid-bathyal amphipods in our study.     

Observations on the locomotion and buoyancy of Phronima sedentaria (Forskål, 1775) (Crustacea: Amphipoda: Hyperiidea)

The buoyancy and locomotion of the hyperiid amphipod Phronima sedentaria (which lives in barrels constructed from the tissues of gelatinous animals) was studied. The amphipods were much denser than sea water. Barrels were slightly denser than sea water and had six times the mass of the amphipods living within them. Phronima sedentaria swims much more quickly (by a factor of about 3–4) when swimming without its gelatinous barrel. The barrel is asymmetrical with one aperture (entrance) having about three times the area of that of the other (exit). All sustained swimming was accomplished with the larger barrel aperture directed forwards and the significance of this is discussed. Water flow around the barrel and much of the flow through the barrel was laminar; turbulence was limited to the posterior third of the interior of the barrel and was associated with the beating of the pleopods that provide both propulsion and the respiratory current.     

A study on amphipods from the superfamily Stegocephaloidea Dana 1852 from the northeastern Pacific region: systematics and distributional ecology

Nine species (including five new to science) of non-lafystiid stegocephaloid amphipods have been recognized within the collections of the Canadian Museum of Nature from the NE Pacific (Alaska to Oregon), viz. Acanthonotozoma rusanovae Bryazgin 1974 (Acanthonotozomatidae), Iphimedia rickettsi Shoemaker 1931 (Iphimediidae), Parandania boecki (Stebbing 1888), Phippsiella cascadiensis n.sp., Stegocephalexia penelope n. gen., n. sp., Stegocephalopsis mamillidacta n. sp. (Stegocephalidae). Odius kelleri Bruggen 1907 is reallocated to Cryptodius n. gen., and C. unguidactylus n. sp. and Imbrexodius oclairi n. gen., n. sp. (Odiidae) are also described. Keys are presented which allow the genera of Odiidae of the world, and of this collection of species, to be distinguished.     

Cladistics and taxonomy of the Afrotropical Empis (Coptophlebia) chrysocera-group (Diptera,Empididae)

The Afrotropical Empis (Coptophlebia) chrysocera-group (Diptera: Empididae) is defined on the basis of two synapomorphies, namely epandrial lamellae connected anteriorly and male cerci made up of an anterior almost bare lobe and a posterior bristled lobe. This group includes 10 species: E. (C.) brazzavillensis sp. n., E. (C.) barbitos Smith, E. (C.) juxtaripa sp. n., E. (C.) lyra Smith, E. (C.) plumata sp. n., E. (C.) chrysocera Collin, E. (C.) cuthbertsoni Smith, E. (C.) machipandensis Smith, E. (C.) samaruensis sp. n. and E. (C.) singulare sp. n. All species are described and keyed. The relationships between these species are established and two complexes of species distinguished. The Empis (Coptophlebia) chrysocera-group apparently occurs everywhere in the Afrotropical region except South Africa.     

A new South American genus and species in the amaryllidid group of lysianassoid Amphipoda

Erikus dahli, a new genus and species in the amaryllidid group of lysianassoid amphipods, is described and illustrated from South American material.     

A report on the cheilostome Bryozoa of the Sudanese Red Sea

Summary

Eighty-six species of bryozoa are listed from collections from reefs in the Sudanese Red Sea, increasing the known fauna list by 30 species. The abundance, in terms of numbers of colonies, and the distribution of nineteen species has been analysed over a range of 30 metres depth. The character of the genera Calyptotheca Harmer and Emballotheca Levinsen are briefly discussed. C. thornelyae is introduced for Lepralia subimmersa Thornely not MacGillivray, and E. harmeri for E. acutirostris Harmer not Canu and Bassler. In addition, three new species of Calyptotheca, C. heteroavicularia, C. nigra and C. sudanensis, and one of Escharoides, E. longirostris, are described.     

Morphology of a calceolus,an antennal receptor of gammaridean Amphipoda (Crustacea)

The internal structure of calceoli, in the gammaridean amphipod, Eusirus perdentatus Chevreux, has been examined for the first time using fast atom etching in conjunction with scanning electron microscopy. The etching technique was used to remove surface layers of the calceolus, revealing a complex array of cuticular fibres supporting the proximal cup and distal plates. The cup was found to consist of a radial set of about 200 rod-like subunits. The results add weight to the view that calceoli may function as phonoreceptors, sensitive to water borne pressure waves.     

Taxonomic studies on Tasmanian phytal amphipods (Crustacea): the families Anamixidae,Leucothoidae and Sebidae

Three amphipods new to science from Tasmania are described herein as Leucothoe ctenochasma sp. nov., L. neptunea sp. nov. (Leucothoidae) and Seba chiltoni sp. nov. (Sebidae). The hyperadult male of ‘Leucothoides’ yarrega Barnard is described as Anamixis yarrega (Barnard) (Anamixidae). Range extensions are reported for Leucothoe boolpooli, L. commensalis and ‘Leucothoides’ yarrega. Leucothoella gracilis was also collected. The morphology of female and small male Leucothoe boolpooli is described. The Anamixis record is the first for the genus outside tropical waters. A key to the world Anamixis spp. in included.     

Extended parental care in two endobenthic amphipods

Extended parental care is described for two endobenthic amphipods which inhabit the estuarine soft-bottoms along the Gulf of Maine. The juveniles of both amphipod species, Leptocheirus pinguis and Casco bigelowi, remain in the burrow of their mother after they hatch from the brood pouch. Several consecutive clutches of L. pinguis can inhabit the female's burrow simultaneously, but in C. bigelowi there is always only one clutch of juveniles in the burrow of the female. Larger juveniles of L. pinguis start building their own small tubes at the bottom of the female's burrow. Casco bigelowi females increase the size of their burrows during the time when the juveniles grow. The juveniles of both species leave the female's burrow at about half adult size. The major tasks of female L. pinguis and C. bigelowi during the time of extended parental care is to irrigate and maintain the deep burrow. It is hypothesized that extended parental care in L. pinguis, C. bigelowi and other tube/burrow-living peracarids is a mechanism to protect small offspring from epibenthic predation.     

A population explosion of Aphis crassivora Koch following DDT application in a cowpea,plot (Vigna unguiculata) cultivar (prima) in Nigeria

Summary

A secondary outbreak of Aphis crassivora Koch pest occured in the DDT sprayed plot of a late cowpea (Vigna unguiculata) cult. (prima) crop at the International Institute for Tropical Agriculture (I.I.T.A.), Ibadan. DDT was sprayed weekly at 1 kg a.i./hec. to control leaf eating to podborer major pests of cowpea. A list of aphid predators observed during early and late cowpea crop is given.     

Coexistence of species of two amphipod genera: Niphargus timavi (Niphargidae) and Gammarus fossarum (Gammaridae)

The co‐occurrence of amphipods Niphargus timavi and Gammarus fossarum was studied. A small brook in SW Slovenia was sampled monthly for one year. Below the primary spring the brook sinks, flows for about 150 m below the surface and springs again. Gammarus fossarum never reached the stretch above the sink. Both species were found at all sampling sites below the secondary spring throughout the year, but the abundance of the two varied along the stream spatially and temporarily. Differences in life cycles between G. fossarum and N. timavi were not informative; however, the estimated reproductive potential of G. fossarum was much higher than of N. timavi. A result of the higher reproductive potential may be the dominance of gammarids in permanent waters, while N. timavi may invade a surrounding fissure system where it survives gammarid competition and summer desiccations when the gammarid population becomes extinct.