Influence of predatory reef fishes on the spatial distribution of Munida gregaria (=M. subrugosa) (Crustacea; Galatheidae) in shallow Patagonian soft bottoms

Predation by reef fishes may play an important role in structuring nearby soft-bottom communities. Here we evaluate the hypothesis that the abundance and spatial distribution of an epibenthic mobile organism, the squat lobster Munida gregaria (=M. subrugosa), is influenced by predation by fishes that shelter in temperate rocky reefs of northern Patagonia. The density of squat lobsters on sandy bottoms around three reefs, one natural and two artificial, was estimated at increasing distances (0, 5, 15 and 45 m) from the reefs. In one of the artificial reefs a sample was first collected four months after the reef was created, before it was colonized by fish, and again nine months later when a population of reef-dwelling fish had been established. An area between 5 and 19 m wide free of squat lobsters surrounded all colonized reefs, and no effect was evident at a distance of 45 m from the reefs. In contrast, the density of squat lobsters did not vary with distance from the reef in the new, uncolonized, artificial reef. A predation exclusion experiment conducted around both artificial reefs resulted in a larger presence of squat lobsters within exclusion cages than in partial and open cages. The caging experiment provides strong evidence for attributing the halo around the reefs to predation by fishes, and to confirm that off-reef foraging behaviour depletes prey abundance in nearby soft bottoms.     

The pelagic and benthic phases of post-metamorphic Munida gregaria (Fabricius) (Decapoda,Anomura)

Some post-metamorphic individuals of Munida gregaria (Fabricius) are permanent members of the benthos while others spend at least part of their time in the water column. These two types of individual are distinct, both morphologically and in the composition of the body. Pelagic specimens have a low density throughout the moult cycle, brought about by a high water content, and low ash and calcium contents. Benthic individuals have this low density for only the first few days post-moult. Normally the pelagic habit is retained only during the first summer as post-larvae but on occasions it is extended over the whole year. In captivity specimens collected at the surface quickly settle on the bottom of the tanks and do not reappear at the surface. The strong positive phototactic response, seen when the animals are collected from the surface, is lost in the first few weeks and the low density persists only until they moult.     

Daily oxygen consumption rhythms of Senegalese sole solea senegalensis (Kaup, 1858) juveniles

Senegalese sole is known to be a species with pronounced nocturnal feeding behaviour. However, as for most fish species, there is a lack of knowledge concerning the influence of such biological rhythm on metabolic rate. The aim of this study was to determine whether individual variation in routine and fed metabolic rate was affected by daily light-dark rhythms in juveniles of Senegalese sole. The individual oxygen consumption measurements in Senegalese sole juveniles were determined by flow-through respirometry, at fasted conditions and after the fish were fed a single meal, the meal time started at 0930 h and fish fed ad libitum for 30 min. The measurements were made during 22 h, of which 8 h was in the light and 14 h in the dark, and started immediately after transfer to the respiratory chambers at 1100 h. The results suggest an influence of light-dark cycles in routine metabolism. It was observed that oxygen consumption increased during the dark phase in fasted fish (FAST) but was higher during the light phase in fed fish (FEED). However, when feed is provided during the light phase, juveniles are capable of shifting oxygen consumption rhythms to respond to the energetic demands of digestion and growth. These results suggest that routine metabolism varies according to the species natural habits as Senegalese sole is known to be nocturnal. The findings of this study underline the importance of understanding the biological rhythms of the species under study before metabolic data are interpreted.     

Metabolic response of juvenile gray snapper (Lutjanus griseus) to temperature and salinity: Physiological cost of different environments

Juvenile gray snapper (Lutjanus griseus) occupy a wide range of estuarine and nearshore habitats that differ in physico-chemical properties. To quantify the energetic cost of inhabiting these different habitats, routine metabolism of individual gray snapper was measured in the laboratory at 20 combinations of temperature (18, 23, 28, and 33 °C) and salinity (5, 15, 25, 35, and 45 psu). An open, flow-through respirometer was used, enabling trials to be run for long periods (∼16 h), while maintaining water quality (dissolved O₂>70% saturation), and providing fish sufficient time to habituate to the chambers undisturbed. Video recordings of fish in the respirometer chambers were analyzed to quantify the spontaneous activity rate of individuals. Analysis of covariance, using fish weight and mean activity rate as covariates, indicated significant temperature and salinity effects on oxygen consumption. Oxygen consumption was significantly higher at high salinities, and the salinity effect was temperature dependent. A polynomial equation describing oxygen consumption as a function of temperature and salinity indicated the increase due to salinity from 5 to 45 psu at high temperatures (30-33 °C) was equivalent to a 3 °C increase in temperature. At intermediate temperatures (24-26 °C), the increase due to salinity from 5 to 45 psu was less dramatic, equivalent to a 2 °C increase in temperature. At the lowest temperatures (18 °C), salinity did not have a significant effect on oxygen consumption. The increased metabolic costs in high salinities (∼7% at the high temperature) represent a significant energy cost for juveniles, that would need to be balanced by lower predation risk or greater food availability to result in similar juvenile production compared to lower salinity environments.     

Rugopharynx rosemariae new species (nematoda: Pharyngostrongylidae) from grey kangaroos (Macropus gig anteus and M. fuliginosus) with life cycle stages and associated pathology

Beverdge I. and Ppresidente P. J. A. 1978. Rugopharynx rosemarie sp. nov. (Nematoda: Pharyngostrongylidae) from grey kangaroos (Macropus giganteus and M. fuliginosus) with life cycle stages and associated pathology. International Journal for Parasitology8: 379–387. Rugopharynx rosemariae new species is described from the stomachs of grey kangaroos, Macropus giganteus Shaw, 1790 and Macropus fuliginosus (Desmarest, 1817) from south-eastern Australia. The new species differs from other species of the genus in spicule length and in the length and shape of the oesophagus. Parasitic life-cycle stages are described from natural infections; free-living life-cycle stages were obtained by culturing eggs from gravid females. Third stage larvae burrow into the gastric mucosa producing small elevated nodules resulting from a localized fibroplastic and inflammatory reaction in the lamina propria and submucosa. Fourth stage and adult worms occur in the stomach lumen. Rugopharynx brevis (Canavan, 1931) is made a synonym of Rugopharynx australis (Mönnig, 1926).     

Effect of different starvation and refeeding periods on macromolecules in the haemolymph,digestive parameters,and reproductive state in Aegla platensis (Crustacea,Decapoda, Aeglidae)

In the present study we assessed the effects of different periods of starvation and refeeding on macromolecule levels (glucose, proteins, triglycerides, and glycerol) in the hemolymph as well as circulating levels of cholesterol in Aegla platensis. We also studied possible changes in the distribution of stomach fullness classes (DSFC), mean stomach fullness degree (SFD), and the mean stomach fullness, hepatosomatic, and gonadosomatic indices. Animals were collected in the field, sexed and divided into groups. This was made as follows: lab control (10 days on standard diet); 5, 15, and 30 days starvation; and 5 days refeeding. During the starvation period there were differences in cholesterol, glucose, and proteins in both genders, but we observed no differences in total lipid, triglycerides, or glycerol levels. The SFD was the lowest in the 30-day starvation group in both females and males. Starvation appears to modulate gastric emptying and possibly digestive processes as well as induce preferential utilization of carbohydrates and proteins. This enables survival throughout the study period. We observed maintenance of gonadosomatic index and reduction of hepatosomatic index in females during the study period with a return to baseline after refeeding. Refeeding was insufficient to restore the DSFC, but sufficient to restore glucose and cholesterol levels.     

Variation of specific proteins, mitochondria and fatty acid composition in gill of Scylla serrata (Crustacea, Decapoda) under low temperature adaptation

The mud crab Scylla serrata is an important commercial crustacean inhabiting estuarine water along the coast of southeast China. Metabolism in the gill is affected continuously by fluctuating water temperature and, therefore, the ability to cope with temperature change is essential to maintain physiological function. This experiment was conducted to help understand the mechanism of low temperature adaptation in S. serrata gill. In this study, 40 healthy juvenile male S. serrata from the same broodstock were grouped randomly into four groups, which were kept at 5 °C, 10 °C, 15 °C and 27 °C, with the same feeding regime during a 3-week adaptation period. Two-dimensional electrophoresis of the proteome was conducted to separate the specific proteins responsible for low temperature adaptation. Variations in the mitochondria were observed using transmission electron microscopy, and fatty acid composition was determined using gas chromatography. The results showed that different numbers of specific proteins were expressed under different low temperature adaptation, with more expressed at 5 °C and 10 °C than at 15 °C. Mitochondrial morphology also varied under different low temperature adaptation, but there was no linear relationship between microbial density and adaptation temperature. The composition of different fatty acids in the gill varied considerably with adaptation temperature, but elongation of the carbon chain and transition from fatty acids occurred at lower temperatures. Thus, changes in the specific proteins, mitochondria and fatty acid composition of the gill were the positive effects of low temperature on metabolism, leading to improved adaptation ability in S. serrata.     

Genetic differences between two spider crabs Pisoides bidentatus (A. Milne-Edwards, 1873) and Pugettia quadridens (de Haan, 1839) (Decapoda: Brachyura: Majoidea) from the Sea of Japan

Biochemical genetics was applied to elucidate the taxonomic position of the spider crab Pisoides bidentatus. Two morphologically similar spider crabs, P. bidentatus and Pugettia quadridens, were compared with four sympatric brachyuran species, Eriocheir japonicus, Hemigrapsus sanguineus, Hemigrapsus penicillatus (Varunidae), and Cancer amphioetus (Cancridae), using 20 allozyme loci. High genetic identity-value between P. bidentatus and P. quadridens (I = 0.758 ± 0.092) suggests that they should evidently be placed to one genus. This conclusion is supported by the similar identity-value between two species of the genus Hemigrapsus (I = 0.821 ± 0.078) and the low genetic similarity (I = 0.125 ± 0.05) between different genera, Hemigrapsus and Eriocheir, within the family Varunidae.     

Patterns of morphological and genetic variability in UK populations of the shore crab, Carcinus maenas Linnaeus, 1758 (Crustacea: Decapoda: Brachyura)

Previous research has identified extensive inter-population variability in the morphology of the shore crab (Carcinus maenas L.). To determine the source of this variation (genetic or environmental), morphological and genetic data were analysed from crabs collected from eight sites around the coast of the UK. Ten morphometric traits were measured from over 800 crabs and the degree of morphological similarity among sites was calculated using multivariate techniques. Allozyme electrophoresis was used to investigate patterns of genetic similarity. Extensive morphological variability was detected: eight out of the ten morphometric traits analysed were useful when discriminating between crabs from each site. Discriminant function analysis revealed that over 35% of individuals could be classified to their site of origin on the basis of their morphology. In contrast, the allozyme analysis revealed low levels of genetic variability, both within the meta-population and among the crab population at each site. Pairwise comparisons revealed a moderate correlation between the degree of morphological and genetic similarity of crabs at each site, which suggests that the observed phenotypic variability has a genetic component. However, only around 20% of the phenotypic variability detected was associated with the patterns of genetic similarity. This means that patterns of morphological variability in this species are largely determined by the local environmental conditions: local factors could have a within-generation selective influence on mean trait values or C. maenas may exhibit phenotypic plasticity.     

Ligand-Induced Structural Transitions, Mutational Analysis, and ‘Open’ Quaternary Structure of the M. tuberculosis Feast/Famine Regulatory Protein (Rv3291c)

Rv3291c is a member of the feast/famine regulatory protein family that is known to form stable protein-DNA complexes. We report a specific oligomeric transition between hexadecameric and octameric/lower-order oligomers in the presence of Phe that supports an effector-mediated model for the disassembly of a nucleosome-like particle. We had generated two mutants, Gly102Thr and Glu104Ala, which are part of the essential 100-106 effector-binding loop. The Gly102Thr mutant adopts an unusual ‘open’ quaternary structure and offers interesting functional insights co-related to the binding of an effector. This is similar to the previously reported Escherichia coli Lrp co-crystallized in the presence of DNA where the interactions of the substrate with the N-terminal DNA binding domain presumably lead to symmetry deviations to the oligomeric association. The present structure represents a direct evidence to support that changes made to the effector-binding domain at the C-terminus also result in a functionally relevant quaternary structural change. Conversely, the Glu104Ala mutant retains the closed quaternary association observed in the native protein and reveals nonsymmetrical interaction effects in the two subunits of the dimer. We also report that the native protein unexpectedly binds Lys but does not recognize Arg and offer a structural explanation for it. Error-scaled difference distance matrix analysis suggests that the protein has a relatively flexible core that is presumably needed to mediate the structural changes necessary for the protein's regulatory functions.     

Characterization of a novel nm23 gene and its potential roles in gametogenesis in the prawn Macrobrachium rosenbergii (de Man, 1879) (Crustacea: Decapoda)

Nm23 is a family of genes encoding the nucleoside diphosphate (NDP) kinase, which functions in a wide variety of biological processes, including growth, development, differentiation and tumor metastasis. In this study, a novel nm23 gene, designated as Mrnm23, was identified from the freshwater giant prawn Macrobrachium rosenbergii. The full-length cDNA was 776 bp in length, encoding for a protein of 176 amino acids with one typical NDP kinase domain that harbored all the crucial residues for nucleotide binding and enzymatic activity. Like human novel nm23-H1B, the putative protein contained a unique 21-amino-acid NH₂-terminal extension as compared to human nm23 (nm23-H1) homologs. Further, 3 extra amino acid residues prolonged the COOH-terminus. The Mrnm23 was ubiquitously expressed in all tissues examined, including androgenic gland, gill, heart, liver, muscle, ovary, and testis. In situ hybridization to gonad sections indicated that the Mrnm23 mRNA was localized in the cytoplasm of cup-base of differentiating spermatids, in the spike of the umbrella-shaped spermatozoa and in the cytoplasm of the early previtellogenic oocytes, suggesting that the Mrnm23 has potential roles in spermiogenesis and early differentiation of oocyte.     

Relationships between environment and mountain riparian plant communities associated with two rare tertiary-relict tree species, Euptelea pleiospermum (Eupteleaceae) and Cercidiphyllum japonicum (Cercidiphyllaceae)

Euptelea pleiospermum and Cercidiphyllum japonicum are dominant relictual tree species of the riparian plant communities in the subtropical region of Shennongjia Mountains, central China. Community survey and multivariate analysis were carried out to characterize their ecological ranges and regeneration characteristics, and further to explore the factors determining their present distribution boundaries and the barriers restricting their range expansion. We recorded 303 woody species, among which there were 14 relictual, rare and/or endemic woody species. Results obtained from cluster analysis corroborated the results from non-metric multidimensional scaling (NMS) ordination, classifying the 42 plots into three well-defined associations. Correlation analysis revealed that variation in species composition among associations was partly explained by some physical (altitude, slope, soil temperature) and chemical (available K, NH₄, pH) properties. Multiple regression analyses with data of adults and seedlings with physical and chemical variables revealed contrasting patterns of the two dominant relictual species. Both taxa have a high resprouting rate that keeps the stands stable irrespective of scarcity of seedlings. However, expansion of the distribution range is difficult in such a situation. E. pleiospermum prefers riparian habitats with poor nutrients in the south-facing slope of the Shennongjia Mountains, which may indicate that this species is light-demanding at some life stages and well adapted to a nutrient-poor habitat where competition from other species is limited. The Cercidiphyllum japonicum population was more scattered and fragmented, and preferred riparian habitats on gentle slopes. Both species are favored by the mild and moist microclimate, but the current conditions in these subtropical mountain riparian habitats probably do not really provide optimal ecological conditions for the two relictual species.     

The feeding, growth, and energetics of two rocky intertidal predators (Pisaster ochraceus and Nucella canaliculata) under water temperatures simulating episodic upwelling

Although most upwelling regions are marked by strong fluctuations in water temperature, few studies have examined how episodic cold-water events affect the physiology and ecology of benthic marine invertebrates. I tested the hypothesis that upwelling-related variation in water temperature regulates the feeding, growth, and energetics of two rocky intertidal predators, the sea star Pisaster ochraceus (Brandt, 1835) and the whelk Nucella canaliculata (Duclos, 1832). Sea stars and whelks were maintained in laboratory tanks at a constant 9 °C, a constant 12 °C, and a treatment that simulated the Oregon coast upwelling regime by cycling between 14-day periods of 12 and 9 °C. Early in the experiments, sea stars and whelks held at 9 °C consumed about 30% fewer mussels (Mytilus trossulus) than those in warmer tanks. Despite lower consumption by whelks in colder tanks, 9 and 12 °C individuals attained the same final size. Similarly, sea stars in 9 °C tanks showed greater growth per gram of mussel tissue consumed than individuals held at 12 °C. These results suggest that reduced consumption under colder conditions was balanced by reduced metabolic costs. Moreover, there appeared to be an energetic advantage to living in the temperature regime characteristic of intermittent upwelling. Sea stars alternately exposed to 12 and 9 °C had a significantly higher growth rate, conversion efficiency, and storage of reserves in the pyloric caeca than individuals in the constant 12 °C tanks. Whelks maintained under fluctuating temperatures tended to grow faster than those held at constant 12 or 9 °C, although this trend was not statistically significant (p=0.069). These results suggest that benthic consumers experiencing cyclic temperatures may feed intensely during periods of warmer water while benefiting from reduced metabolic costs during cold-water intrusions. Because the fecundity of Pisaster and Nucella is a function of energy stored during the upwelling season, interannual variability in upwelling patterns could alter the reproductive output of these species.     

Description of a new species of Parasesarma (Crustacea; Decapoda; Brachyura; Sesarmidae) from the Persian Gulf, based on morphological and genetic characteristics

The genera Parasesarma and Perisesarma are common inhabitants of mangroves and estuaries of the Indo-West Pacific. These, overall similar, genera of sesarmid crabs can be told apart by the presence or absence of an anterolateral tooth, but recent and ongoing studies show that they are not reciprocally monophyletic. In recent years, detailed morphological studies have revealed a surprising number of undescribed new species within these genera. In the present paper, we describe a new species of the genus Parasesarma from the relatively poorly studied Persian Gulf. So far, these specimens had been referred to as Parasesarma plicatum (Latreille, 1803), but morphological and genetic characteristics clearly allow separation of the two species. Consequently, the species from the Persian Gulf is here described as new and morphological and mitochondrial genetic characters are provided that allow recognition of the species.     

Reactions of hydrogen and oxygen with Photosystem I of isolated heterocysts from Anabaena variabilis (ATCC 29413)

Isolated heterocysts from Anabaena variabilis show high rates of light- and hydrogen-dependent acetylene reduction. This heterocyst preparation also shows light-induced redox reactions of cytochromes f-556 and b-564. Both cytochromes are reversibly oxidized by light or by oxygen (in the dark). Oxygen-oxidized cytochromes assume their initially reduced state by addition of dithionite or flushing the reaction vessel with hydrogen or argon. All three agents remove oxygen from solutions more or less efficiently, thereby creating reducing conditions; hydrogen-induced reduction is slow and generally completed after about 10 min. No evidence has been obtained for a direct electron donation of hydrogen to either of the cytochromes measured. Photoreduction of nitrogen in the presence of hydrogen is explained by a combined operation of properly poised cyclic photophosphorylation providing ATP, and a light-independent hydrogenase reaction providing reductant.     

Larval and early juvenile development of Lithodes santolla (Molina, 1782) (Decapoda: Anomura: Lithodidae) reared at different temperatures in the laboratory

The southern king crab, Lithodes santolla Molina, is distributed in cold-temperate and subantarctic waters ranging from the southeastern Pacific island of Chiloé (Chile) and the deep Atlantic waters off Uruguay, south to the Beagle Channel (Tierra del Fuego, Argentina/Chile). Recent investigations have shown that its complete larval development from hatching to metamorphosis, comprising three zoeal stages and a megalopa, is fully lecithotrophic, i.e. independent of food. In the present study, larvae were individually reared in the laboratory at seven constant temperatures ranging from 1 to 18 °C, and rates of survival and development through successive larval and early juvenile stages were monitored throughout a period of 1 year. The highest temperature (18 °C) caused complete mortality within 1 week; only a single individual moulted under this condition, 2 days after hatching, to the second zoeal stage, while all other larvae died later in the zoea I stage. At the coldest condition (1 °C), 71% of the larvae reached the zoea III stage, but none of these moulted successfully to a megalopa. A temperature of 3 °C allowed for some survival to the megalopa stage (17-33% in larvae obtained from two different females), but only a single individual passed successfully, 129 days after hatching, through metamorphosis to the first juvenile crab instar. At all other experimental conditions (6, 9, 12 and 15 °C), survival through metamorphosis varied among temperatures and two hatches from 29% to 90% without showing a consistent trend. The time of nonfeeding development from hatching to metamorphosis lasted, on average, from 19 days at 15 °C to 65 days at 6 °C. The relationship between the time of development through individual larval or juvenile stages (D) and temperature (T) was described as a power function (D=aT^b, or log[D]=log[a]blog[T]). The same model was also used to describe the temperature dependence of cumulative periods of development from hatching to later larval or juvenile stages. One year after hatching, the 7th (6 °C) to 9th (15 °C) crab instar was reached. Under natural temperature conditions in the region of origin of our material (Beagle Channel, Argentina), L. santolla should reach metamorphosis in October-December, i.e. ca. 2 months after hatching (taking place in winter and early spring). Within 1 year from hatching, the crabs should grow approximately to juvenile instars VII-VIII. Our results indicate that the early life-history stages of L. santolla tolerate moderate cold stress as well as planktonic food-limitation in winter, implying that this species is well adapted to subantarctic environments with low temperatures and a short seasonal plankton production.     

Ultrastructure of the antennal sensorial appendage of larvae of Ophonus ardosiacus (Lutshnik, 1922) (Coleoptera, Carabidae) and possible correlations between size and shape and the larval feeding habits

The antennal sensory appendage morphology was studied in 19 species of carabid beetle larvae using scanning electron microscopy. Shape and size of the organ has been re-examined in selected taxa and are compared to figure out possible correlations between antennal sensory structures and larval morphoecological types. Morphometric analysis shows no correlation between antennal sensory appendage dimension and the four most common behavioural types. The ultrastructure of this sensory organ is described for larvae of Ophonus ardosiacus and the possible function is discussed. Olfactory function has been indicated as the most probable. The high number of chemosensory neurons of this multiporous organ suggests a possible ability of fine odour discrimination related to prey choice or host location.