Respiration of Orchomene plebs (Hurley, 1965) and Waldeckia obesa (Chevreux, 1905) from Admiralty Bay (South Shetlands Islands,Antarctic)

Metabolism of Orchomene plebs from Admirably Bay is higher than that of Waldeckia obesa, and similar to that of P. plebs from McMurdo Sound. The range of variation in respiration is highest below freezing which means that these are optimum temperatures for the Amphipoda species under study.     

Calceoli: Antennal Sensory Organs of Amphipods (Crustacea,Amphipoda, Gammaridea) from Lake Baikal

Biology Bulletin - The list of endemic calcioliferous (carrying calceoli, the antennal sensory organs) amphipods is presented for Lake Baikal. It includes 47 species and subspecies (13% of the...     

Rhythmicity of chromophore turnover of visual pigment in the Antarctic amphipod Orchomene plebs (Crustacea; Amphipoda)

1. Relative retinal amounts in the compound eye of the Antarctic amphipod Orchomene plebs were assessed during conditions of continuous summer daylight every 3 h over a period of 48 h. The habitat of the experimental animal is the bottom of the Ross Sea (78°S; 166°E) down to depths of at least 400 m; water temperature is a constant — 1.8° C. A periodicity of 12 h was detected with relative amounts of 11-cis retinal exhibiting peaks at midday and at midnight and troughs at 7.00 h and 19.00 h.
2. The result that 90% of retinoid were insoluble in n-hexane suggests that at least 90% of the measured retinoid were attached to membrane-bound proteins such as opsin.
3. Selective light adaptation showed that the visual pigments were thermostable and photoregenerable. The main absorbance peak of rhodopsin, compared with metarhodopsin, seems to be in the longer wavelengths.

     

Karyotype morphology in Hyperiella dilatata Stebbing 1888 (Amphipoda: Hyperiidae) from the Ross Sea (Antarctica)

Summary The chromosome complement and some karyological features were investigated in the pelagic amphipod Hyperiella dilatata Stebbing 1888 from the Ross Sea (Antarctica). The diploid karyotype consists of 48 metacentric and 10 submetacentric elements (2n = 58). The presence of secondary constrictions and supernumerary chromosomes is described. Available chromosome numbers of Hyperiidea exhibit a wide range of distribution, among which Hyperiella dilatata is the closest to the modal number of other amphipods.     

Marine Gammaridea (Crustacea: Amphipoda) from the Indian region; family — Ampeliscidae

The paper deals with 4 species of ampeliscid amphipods. For the first time among ampeliscids, incomplete coalescence of urosomites 2 and 3 is noticed in two of these viz. Ampelisca cyclops Walker and Amplisca scabripes Walker. It is suggested that this unique feature may be taken note of by those coming across this genus so that eventually we may be able to bring about a division of the genus Ampelisca. The study supports Pirlot's (1936) observation on the validity of A. chevreuxi Walker and points out that the distinction made by J. L. Barnard (1960) for separating this species from A. zamboangae Stebbing is only a case of sexual dimorphism.     

A new stenothoid species related to the taxonRaumahara Barnard, from Australia (Crustacea, Amphipoda, Gammaridea)

Benthic samplings along the southern temperate coast of Australia yielded stenothoid specimens related to the taxonRaumahara Barnard. ?Raumahara virdurorum sp. n. is described, illustrated, and the systematic position within the genus is discussed.Raumahara seems to be a nonmonophyletic group, as not one synapomorphic character can be discerned that exactly fits for each member of this taxon.     

Bacterium-bacterium inhibitory interactions among psychrotrophic bacteria isolated from Antarctic seawater (Terra Nova Bay, Ross Sea)

One hundred and forty bacteria isolated from Antarctic seawater samples were examined for their ability to inhibit the growth of indigenous isolates and their sensitivity to antibacterial activity expressed by one another. On the basis of 16S rRNA gene sequencing and analysis, bacterial isolates were assigned to five phylogenetically different taxa, Actinobacteria, alpha and gamma subclasses of Proteobacteria, Bacillaceae, and Bacteroidetes. Twenty-one isolates (15%), predominantly Actinobacteria, exhibited antagonistic properties against marine bacteria of Antarctic origin. Members of Bacteroidetes and Firmicutes did not show any inhibitory activity. Differences were observed among inhibition patterns of single isolates, suggesting that their activity was more likely strain-specific rather than dependent on phylogenetic affiliation. A novel analysis based on network theory confirmed these results, showing that the structure of this population is probably robust to perturbations, but also that it depends strongly on the most active strains. The determination of plasmid incidence in the bacterial strains investigated revealed that there was no correlation between their presence and the antagonistic activity. The data presented here provide evidence for the antagonistic interactions within bacterial strains inhabiting Antarctic seawater and suggest the potential exploitation of Antarctic bacteria as a novel source of antibiotics.     

Lipolytic activity of Antarctic cold-adapted marine bacteria (Terra Nova Bay, Ross Sea)

AIMS: The aim of this study was to investigate the lipolytic activity of cold-adapted Antarctic marine bacteria and, furthermore, the combined effect of some environmental factors on this enzymatic process. METHODS AND RESULTS: Strains were assayed for lipolytic activity on a basal medium amended with seven individual fatty acid esters. A significant activity was observed for 148 isolates (95.5% of the total screened). The interactive effect of pH, temperature and NaCl concentration on the substrates was tested for six representative isolates, identified as Pseudoalteromonas, Psychrobacter and Vibrio. Differences between strains according to NaCl and pH tolerances were observed. Only one strain degraded the substrate more efficiently at 4 degrees C than at 15 degrees C. CONCLUSIONS: Our findings demonstrate that the lipolytic activity of Antarctic marine bacteria is rather variable, depending on culture conditions, and occurs in a wide range of salt concentration and pH. SIGNIFICANCE AND IMPACT OF THE STUDY: Isolation and characterization of bacteria that are able to efficiently remove lipids at low temperatures will provide insight into the possibility to use cold-adapted bacteria as a source of exploitable enzymes. Moreover, research on the interactive effects of salt concentration, pH and temperature will be useful to understand the true enzyme potentialities for industrial applications.     

Two new species of Urothoe (Crustacea, Amphipoda, Gammaridea) from the East Johor Islands Archipelago, Malaysia

Two new species of urothoid amphipods from Pulau Sibu and Pulau Tinggi, Johor are described and illustrated. The specimens of Urothoe sibuensis new species were collected by vertical haul plankton net and is distinctively different from other existing Urothoe species by these combination of special characters; similar gnathopods 1-2 with short and stout propodus expanded into poorly defined palms; large eyes and epimeron 3 smooth. Urothoe tinggiensis new species as collected using an airlift suction sampler at seagrass area is characterized by its different gnathopodal configuration with setose dactylus of 5th pereopod; eyes minute; carpus is wider than merus in the 5th pereopod; subquadrate coxa 4; merus and carpus of pereopods 6-7 are linear.     

Planktivory in Pagothenia borchgrevinki (Pisces: Nototheniidae) in McMurdo sound,Antarctica

Summary Specimens of the Antarctic fish P. borchgrevinki were collected from just beneath the sea-ice in McMurdo Sound over the period 8 November to 6 December, 1985. The stomach contents of 200 fish were analysed and compared with the co-occurrence of the prey species in the plankton. Numerically, the dominant prey was a thecosomatid pteropod Limacina helicina (83%), followed by a hyperiid amphipod Hyperiella dilatata (5%). Other prey species in decreasing order of occurrence were Euphausia crystallorophias, Euchaeta antarctica, other copepods, a decapod crustacean larva, chaetognaths, the amphipods Orchomene plebs and Epimiriella macronyx, and unidentified juvenile fish. The order of frequency of occurrence of these prey in the guts of all the fish was H. dilatata (in 73% of the fish), L. helicina (71%), calanoid copepods (55%), chaetognaths (51%), E. crystallorophias (42%), decapod crustacean larva (32%), O. plebs (27%), juvenile fish (20%), and E. macronyx (14%). In volumetric terms, the dominant diet contributors were O. plebs (38%), L. helicina (17%) and chaetognaths (15%). All prey except O. plebs and E. macronyx were taken in concurrent plankton samples. Although planktivory of Pagothenia borchgrevinki is confirmed, it is not certain whether feeding is confined to the immediate sub-ice environment.     

A new species of Caprellinoides (Crustacea: Amphipoda: Phtisicidae) from the Antarctic

A new caprellid species, Caprellinoides singularis, is described and illustrated based on the material collected on the Polarstern Cruise ANT XVII/3 from the Branfield Strait. The most striking characteristic of this species is the presence of bilobed gills on pereonites 3 and 4. The genus Caprellinoides is revised. Caprellinoides antarctica Schellengerg, 1926 and Caprellinoides spinosus Barnard, 1930 are considered junior synonyms of Caprellinoides tristanensis Stebbing, 1888 and Caprellinoides mayeri (Pfeffer, 1888), respectively. The new species, C. singularis, is compared with the remaining species in the genus Caprellinoides: C. tristanensis and C. mayeri, which are illustrated in detail. Received in revised form: 4 June 2001 Electronic Publication     

Mental barbel and meristic variation in the Antarctic notothenioid fish Dolloidraco longedorsalis (Perciformes: Artedidraconidae) from the Ross Sea

A collection of 58 specimens of Dolloidraco longedorsalis from the southwestern Ross Sea was studied for intraspecific variation in the number of second dorsal and anal rays, number of vertebrae, and length and shape of the mental barbel - a key diagnostic and taxonomic character in this family. Ranges for meristics are compact and extend documented values to 13 for anal rays and 37 for vertebrae. There is a nearly twofold difference in the relative length of the mental barbel. There are no significant differences between the sexes in any meristic or morphometric feature. The terminal expansion of the barbel exhibits four types, documented with illustrations and histology: typical expanded form (43%), not expanded or tapered (33%), slightly expanded (22%), and large expansion (2%). There is no relationship between absolute and relative barbel length and sex or barbel type and sex. There is no relationship between barbel type and size of the specimen. Twenty-five percent of specimens have the epidermis of the terminal expansion arranged as broad ridges or mounds. The mental barbel of D. longedorsalis is therefore individually variable with no evidence of sexual dimorphism, and the type of barbel does not vary ontogenetically. Histological analysis of the barbel reveals that the terminal expansion consists of a thick epidermis and that dermal papillae are responsible for the pattern of surface projections sometimes present. The epidermis near the tip of the barbel is twofold thicker in specimens with a terminal expansion. The distal morphology of the barbel, whether straight or expanded, probably has little functional significance. The barbel is richly supplied with nerves and blood vessels and the core consists of pseudocartilage. The barbel is probably a somatosensory organ.