Evolutionary relationships among deep-sea mytilids (Bivalvia: Mytilidae) from hydrothermal vents and cold-water methane/sulfide seeps

A protein electrophoretic survey of mytilids inhabiting deep-sea hydrothermal vents and cold-water methane/sulfide seeps revealed electromorph patterns diagnostic of 10 distinct species. From hydrothermal vents located at sites on the Galápagos Rift, the Mid-Atlantic Ridge, and the Mariana Back Arc Basin, we detected four species of mytilids. Six additional species were detected from three cold-water seep sides in the Gulf of Mexico. The patchy distribution and temporal stability of seeps may provide a greater opportunity for mytilid diversification and persistence than vent sites Nei's genetic distances (D) between species were relatively large (range: 0.528 to ) both within and among habitat types. This pronounced degree of genetic differentiation suggests a relatively ancient common ancestor for the group. Phylogenetic trees were generated using distance Wagner and parsimony analyses of allozyme and morphological characters. The tree topologies obtained from both methods support: (1) the hypothesis that a seep ancestor gave rise to the deep-sea hydrothermal vent mytilids, (2) a historical progression from shallow-water to deep-water habitats, and (3) a co-evolutionary progression from external to internal localization of bacterial symbionts. Whether the seep mytilid taxa constitute paraphyletic or polyphyletic groups remains unresolved. Our phylogenetic hypotheses also provide a benchmark for the phylogeny of mytilid bacterial symbionts.     

Temporal adaptations in visual systems of deep-sea crustaceans

The temporal characteristics of the visual systems of deep-sea crustaceans were examined at varying light levels. Experimental organisms were collected off Hawaii and southern California in 1991 and 1992, and continually maintained in the dark. At the University of California Santa Barbara Marine Laboratory, the temporal components of both visual interneuron activity and electroretinograms (ERGs) of adult Gnathophausia ingens were tested at threshold and with background light levels up to 6 log units above threshold. To compare these responses with those of mid-water organisms inhabiting shallower depths, the temporal characteristics of the ERGs of Oplophorus spinosus and juvenile G. ingens were assessed. Adults of both species showed little or no change in the time components of their responses when light-adapted, except for the response latency. There was also no evidence of a circadian rhythm in visual sensitivity. O. spinosus, a vertical migrator, and juvenile G. ingens, which inhabit a shallower depth than the adults, exhibited more rapid responses than adult G. ingens. These varying responses are considered adaptations to the differences in light levels at the characteristic depths of the organisms.     

深海热液喷口微生物对矿物元素行为的影响

介绍了生长在深海热液喷口周围的微生物的种类及其生长繁殖的能量来源;并就其参与的矿物沉积和浸出行为做了阐述;最后在目前国内外研究现状的基础上提出了今后应该研究的方向。     

Coelenterazine distribution and luciferase characteristics in oceanic decapod crustaceans

Coelenterazine biosynthesis has recently been demonstrated in the developing eggs of the decapod Systellaspis debilis. The cellular source of coelenterazine and the potential for biosynthesis in adult decapods, however, have not been fully investigated. We have conducted a systematic study of coelenterazine content in >230 individual decapods representing 19 species of Oplophoridae and 22 species from other families. We show for the first time that coelenterazine is responsible for both secretory and photophore luminescence in the same decapod. Tissues associated with secretory luminescence (hepatopancreas and stomach) in the Oplophoridae contained almost 3 orders of magnitude more coelenterazine (mean value=2154 pmol per specimen) than cuticular photophores (mean value=8 pmol per specimen). Coelenterazine content increases by 2 to 4 orders of magnitude during the development of three species of Oplophoridae. Species of Oplophoridae contain an order of magnitude more coelenterazine than those of other families (mean value=154 pmol per specimen). Coelenterazine was also detected in 11 apparently nonluminous decapod species (mean value=200 pmol per specimen). S. debilis luciferase characterisation enabled a luciferase assay to be developed to facilitate studies of the environmental control of bioluminescence. We hypothesise that the coelenterazine requirement in secretory bioluminescence exceeds that which could be assimilated from the food-chain. The significant increase of coelenterazine during the life cycle of secretory decapods supports this hypothesis. Putative evidence for environmental control of coelenterazine luminescence is also reported.     

Digestive enzymes in marine invertebrates from hydrothermal vents and other reducing environments

The present study demonstrates the potential hydrolytic activities in the symbiont-containing tissues of the vent invertebrates Riftia pachyptila, Bathymodiolus thermophilus (collected in 1991 at the East Pacific Rise) and the shallow-water bivalve Lucinoma aequizonata (collected in 1991 from the Santa Barbara Basin). Activities of phosphatases, esterases, -glucuronidase and leucineaminopeptidase were comparable to those of digestive tract tissues of other marine invertebrates. A lack in most glycosidases as well as in trypsin and chymotrypsin was observed. Activities of lysozyme and chitobiase were rather high. In all vent invertebrates with symbionts and in L. aequizonata, the symbiont-containing tissues and the symbiont-free tissues had similar levels of enzymatic activities, indicating that polymeric nutrients could be hydrolysed after release from the symbionts and cellular uptake. The high activities of -fucosidase in all vent invertebrates as well as in the shallow-water bivalve L. aequizonata could point to the existence of a yet undescribed substrate available to hydrolysation. The ectosymbionts-carrying polychaete Alvinella pompejana (collected in 1991 at the East Pacific Rise, EPR) shows high lysozyme activities in its gut, consistent with the proposed food source of bacteria. For the vent crab Bythogrea thermydron (also collected in 1991 at the EPR) hydrolytic activities were highest in the gut, dominated by esterase and peptidase activities which support their proposed carnivorous food source. A snail and a limpet collected from R. pachyptila tubes showed high levels of chitobiase suggesting a food source of grazed bacteria or ingested R. pachyptila tube.     

Metabolic diversity in epibiotic microflora associated with the Pompeii wormsAlvinella pompejana andA. caudata (Polychaetae: Annelida) from deep-sea hydrothermal vents

Specimens of alvinellid polychaetes (Alvinella pompejana Desbruyères and Laubier, 1980 andA. caudata Desbruyères and Laubier, 1986) and their tubes were sampled from deep-sea hydrothermal vents at 13°N from the manned submersible Nautile during the Hydronaut cruise (October to November 1987) on the East Pacific Rise. Samples were subjected to bacterial analysis aboard the mother ship Nadir to detect bacteria involved in the nitrogen and sulphur cycles, in non-specific heterotrophic processes, and displaying resistance to selected heavy metals. Cultures were incubated at different temperatures under atmospheric and in situ (250 atm) pressures. Bacterial growth was observed in enrichment cultures for most metabolic types screened. Heavy-metal-resistant bacteria were also detected in many samples. No filamentous bacterial form was observed in the cultures. The results demonstrate a high metabolic diversity in episymbiotic flora, indicating that the worm (A. pompejana orA. caudata), its tube and its epiflora represent a complex micro-ecosystem.     

Comparative study of behavioral-sensitivity thresholds to near-UV and blue-green light in deep-sea crustaceans

The behavioral sensitivities of five species of deep-sea crustaceans (order Decapoda: Acanthephyra curtirostris, A. smithi, Notostomus gibbosus, Janicella spinacauda and Oplophorus gracilirostris) to near-UV and blue-green light were studied during a research cruise off the coast of Hawaii in 1993. Two of the five species have electrophysiologically-measured spectral sensitivity peaks at 400 and 500 nm, while the remaining three species have a single sensitivity peak at 490 to 500 nm. In the current study, behavioral mean threshold sensitivities (defined as the lowest irradiance change to which the shrimp would give a behavioral response) were determined for tethered specimens of each species at two wavelengths, 400 and 500 nm. The mean behavioral threshold sensitivities of the two species with putative dual visual-pigment systems were approximately the same to near-UV and blue-green light, while the other three species were significantly less sensitive to near-UV vs blue-green light. Results from these experiments indicate that (1) behavioral information obtained from tethered shrimp accurately reflects their spectral sensitivity, and (2) the sensitivity of the putative dichromats to near-UV light is sufficiently low to detect calculated levels of near-UV light remaining in the down-welling field at their daytime depth of 600 m. Possible functions of this high sensitivity to short wavelength light are discussed.     

Metabolism of shallow and deep-sea benthic crustaceans and echinoderms in Hawaii

Little is known about the metabolism of deep-living, benthic invertebrates, despite its importance in estimating energy flow through individuals and populations. To evaluate the effects of depth and broad taxonomic group/locomotory mode, we measured the respiration rates of 25 species of benthic decapod crustaceans and 18 species of echinoderms from the littoral zone to the deep slope of Hawaii. Specimens were collected by hand, trap, or submersible and maintained in the laboratory at temperatures close to ambient temperatures recorded at the time of collection. After acclimatization to laboratory conditions, oxygen consumption was measured for each individual in closed chambers. Overall, crustaceans had higher metabolic rates than echinoderms, and within the crustaceans, caridean shrimps had higher rates than crabs and lobsters. These differences are probably related to locomotory mode and general levels of activity. At in situ environmental temperatures, metabolic rates of deeper-living invertebrates are much lower than those of shallower living species, but this decline is explained by changes in temperature. When the data were compared with similar data sets collected off California and in the Mediterranean, Hawaiian crabs, lobsters, and echinoderms had lower metabolic rates than similar species in the other regions after adjustments for temperature were made. Some of these differences could be methodological. Regional food web models should use broad taxonomic groupings and region-specific data when possible.     

Comparative species composition and relative abundance of decapod crustaceans in marine habitats of Panamá

The community structure of the decapod crustacean fauna of 7 tropical, shallowwater, marine habitats (sandy beaches, mangrove swamps and rocky intertidal habitats on both the Pacific and Caribbean coasts of Panama, and Pocillopora damicornis coral habitat of the Bay of Panama) were examined and analyzed for species composition and relative abundances. Collections from the 7 habitats yielded 4361 individuals, representing 236 species. The number of species per habitat was (Pacific, Caribbean): sandy beach (16, 7); mangrove (20, 17); P. damicornis (53); rocky intertidal (78, 67). There were more species represented by more individuals in the Pacific habitats. An index of faunal similarity was calculated for each pair (Pacific-Caribbean) of habitats. This index is the number of ecologically similar congeneric species which occurred in both habitats expressed as a percentage of the total number of species present in the pair of habitats. For the sandy beach communities there were three Pacific species which were similar to three Caribbean species, a similarity of 6/23 or 26%. The index of similarity for the mangrove communities is 54% and for the rocky intertidal communities it is 37%. The P. damicornis community has affinities with the Pacific rocky intertidal community (18%), with that of the Caribbean rocky intertidal (16%) and with that of Indo-West Pacific pocilloporid corals (20%). A few specialized species dominated each of the communities. The habitats and the number of species accounting for over half of the individuals present are (Pacific, Caribbean): sandy beach (1, 1); mangrove (4, 4); P. damicornis (5); and rocky intertidal (3, 6). Most of the species in each community were represented by one or a few individuals.     

POM in macro-/meiofaunal food webs associated with three flow regimes at deep-sea hydrothermal vents on Axial Volcano,Juan de Fuca Ridge

Deep-sea hydrothermal vent ecosystems host both symbiotic and non-symbiotic invertebrates. The non-symbiotic vent fauna is generally assumed to rely on free-living chemoautotrophic bacteria as their main food source but other sources such as detritus have recently been suggested to be a part of the invertebrate diets. Little is known about how food availability influences the distribution of vent organisms on a small scale. In addition, the feeding ecology and role of small, often numerically dominant invertebrates, the meiofauna is poorly understood at vents. In this study, we used stable carbon and nitrogen isotopic analysis to investigate the role of particulate detritus in the diets of macro- and meiobenthic invertebrates within three vent assemblages at Axial Volcano, Juan de Fuca Ridge, and Northeast Pacific. Particulate organic matter of a detrital origin became more important in the diet of invertebrates in assemblages typically associated with low-hydrothermal flow intensities. Meiobenthic species occupied several different feeding guilds and trophic levels in the assemblages investigated. We conclude that small-scale spatial variability in food sources is an important feature of vent food webs and that spatial patterns observed here and elsewhere are shaped by variations in hydrothermal discharge.     

Natural variation in the concentrations of haemocyanin from three decapod crustaceans, Nephrops norvegicus, Liocarcinus depurator and Hyas aranaeus

Natural variation in the concentrations of haemocyanin ([Hc]) is examined for three decapod species collected from two different locations (Gullmarsfjord and Kattegat) off the west coast of Sweden (August to September 1998). Only one of the frequency distributions for [Hc] is normally distributed, and median values differ both between and within species. Differences in [Hc] cannot be attributed to sex, reproductive condition or moulting condition (over the limited range of moult stages examined) for any of the species. While body size did not scale with [Hc] for the Norway lobster Nephrops norvegicus or the swimming crab Liocarcinus depurator, it did for the spider crab Hyas araneus. To our knowledge this is the first time a negative relationship between body size and [Hc] has been reported for any crustacean. Thus the right-skewed frequency distribution of spider crab [Hc] could be accounted for by the right-skewed body size distribution recorded. The shape of the frequency distributions for [Hc] from the other two species could not be accounted for through differences in the factors examined here, although it is suggested that the amount of food consumed (or not) may be important. Received: 19 July 1999 / Accepted: 4 October 1999     

深海热液喷口周围微氧耐压细菌的培养研究

研究采用析因实验设计,探讨了培养基的水源、培养温度和生长pH等因素对喷口细菌生长繁殖的影响,初步探索了常压下东太平洋某海底喷口周围微氧耐压细菌的生长条件。样品培养10d后,对培养液中细菌量进行显微计数,实验数据用SPSS11.0统计软件中的方差分析程序进行处理。统计结果显示:在标准大气压下,从研究样品中获得最多细菌数的较优培养条件为:培养基水源为单蒸水;生长pH为7.60;培养温度为50℃。在该条件的培养液中细菌平均浓度达2.596×10个/mL。研究结果为进一步认识、鉴定与开发利用深海喷口周围细菌资源打下了基础。     

Structure and function of Halice hesmonectes (Amphipoda: Pardaliscidae) swarms from hydrothermal vents in the eastern Pacific

Swarms of the pardaliscid amphipod Halice hesmonectes were sampled at low-temperature hydrothermal vents in the Venture Hydrothermal Fields of the East Pacific Rise. In excess of 3000 individuals were collected from a range of sites/habitats, and at two points in time (December 1991 and March 1994). The structure of swarms was described in terms of growth stages, the development of primary and secondary sex characteristics and the accumulation of nutritional reserves. The results demonstrated that swarms contained a wide range of growth stages, but that small juveniles and mature males and females were absent. Swarm structure was interpreted as an equilibrium dependent on the relative proportion of time spent by each growth stage in the swarm habitat. This equilibrium swarm structure was very similar at different sites and times. Swarms dominated by small juveniles occurred at the northern sites in December 1991 following a period of eruption and new venting in April 1991. Equilibrium swarm structure had become re-established at these sites by March 1994. The function of swarming was considered. The results indicated that swarming was not associated with reproductive activity. The available evidence, though not conclusive, suggested that swarms were associated with feeding. Received: 28 May 1999 / Accepted: 16 February 2000     

Diets of four decapod crustaceans (Linuparus trigonus,Metanephrops andamanicus,M. australiensis and M. boschmai) from the continental shelf around Australia

Linuparus trigonus (Palinuridae) was collected from northeast Australia at depths of 220 to 300 m in the austral summer of 1985–1986 and its diet was analysed for diel feeding-periodicity and composition. The sex and size of the lobsters and the depth at which they were caught were recorded. About 35% of the foreguts were less than 10% full. L. trigonus appears to be a predator of slow-moving or nearsessile benthic invertebrates; its diet is mainly bivalves, gastropods, ophiuroids, crustaceans, polychaetes, and foraminiferans. Most dietary items differed significantly between the size classes of lobster. The frequency of crustacean remains increased with depth and more gastropods were consumed by lobsters caught at 260 m than at other depths. No significant periodicity in feeding was found for L. trigonus. The foreguts of three Metanephrops spp. (Nephropidae) collected from north-west Australia in August 1983 (M. andamanicus) and January/February 1984 (M. australiensis and M. boschmai) were nearly empty, and nearly half were less than 10% full. Fish, crustaceans and squids were the most common food items eaten. The main food items varied between the species: M. andamanicus ate nearly equal amounts of fish and crustaceans; M. australiensis ate chiefly crustaceans; M. boschmai mainly ate fish and seldom fed on squid. Metanephrops spp. appear to feed by attacking mobile animals and tearing off appendages or by scavenging.     

Ecotoxicological responses to chalcopyrite exposure in a proxy for deep-sea hydrothermal vent shrimp: implications for seafloor massive sulphide mining

Deep-sea mineral prospecting has raised concerns regarding potential ecotoxicological impacts of deep-sea mineral extraction. Although metal mineral phases are predicted to exhibit low bioavailability, few data explore the relative toxicity of mineral phases and dissolved constituent metals. Acute 96?h chalcopyrite (CuFeS₂) (<250?µm grain size) exposures using the shallow-water ecophysiological model organism Palaemon varians as an ecotoxicological proxy for deep-sea hydrothermal vent shrimp revealed no effect in both lethal and sublethal assays up to 2.888?g?L^?1, suggesting that chalcopyrite is not bioavailable. Deep-sea species, therefore, appear at greater ecotoxicological risk from dissolved metals during seafloor massive sulphide (SMS) mining. Consequently, an approach combining modelling the release, and spatial and temporal dilution of dissolved metals during SMS mining, with data on sublethal effects of dissolved metals on shallow-water proxies, may best constrain the potential ecotoxicological impacts of SMS mining, and deliver ecotoxicological threshold concentrations for active SMS extraction.     

Species-specific avoidance responses by blue crabs and fish to chronic and episodic hypoxia

Although both chronic and episodic hypoxia (O₂<2 mg l^–1) alter the distribution and abundance patterns of mobile animals within estuaries, recent evidence suggests that some animals may be more likely to remain within hypoxic or anoxic water than others, due to differences in physiological tolerance and movement responses to the dynamics of hypoxia. Determining avoidance responses to hypoxia is important for identifying the species most susceptible to the direct and indirect impacts of these events. A trawl survey was used to examine the avoidance responses of blue crabs (Callinectes sapidus) and several fish [pinfish (Lagodon rhomboides), spot (Leiostomus xanthurus), Atlantic croaker (Micropogonias undulatus), bay anchovy (Anchoa mitchilli), and paralichthid flounders (Paralichthys dentatus and Paralichthys lethostigma)] to chronic hypoxia and episodic hypoxic upwelling events in the Neuse River Estuary, North Carolina, USA. Trawl collections were made in three depth strata (3.0–4.6 m, 1.7–3.0 m, and 0.9–1.7 m depth) to quantify changes in the depth-specific distribution and abundance patterns of the six most common estuarine taxa during three dissolved oxygen conditions: normoxia, chronic hypoxia, and episodic hypoxic upwelling events. Pinfish, anchovies, blue crabs, and paralichthid flounder abundance increased with increasing dissolved oxygen concentrations. The two taxa most closely associated with the bottom (blue crabs and flounder) showed the strongest avoidance response to hypoxia. All taxa showed a stronger avoidance response to chronic hypoxia as compared to episodic hypoxic upwelling events. This difference is attributed to a reduced ability to avoid the rapid intrusions of hypoxic water during episodic events, or to increased risks of injury and predation in shallow refuge habitats, which may force some individuals back into hypoxic water.Communicated by J.P. Grassle, New Brunswick     

Evolutionary relationships of deep-sea hydrothermal vent and cold-water seep clams (Bivalvia: Vesicomyidae): results from the mitochondrial cytochrome oxidase subunit I

Phylogenetic relationships among vesicomyid clams (Bivalvia: Vesicomyidae) and their placement within the order Heterodonta were examined using mitochondrial encoded cytochrome oxidase subunit I (COI) DNA sequences. The presently analyzed vesicomyids represent a recent monophyletic radiation that probably occurred within the Cenozoic. Nucleotide phylogenetic analyses resolved discrete clades that were consistent with currently recognized species: Calyptogena magnifica, C. ponderosa, Ectenagena extenta, C. phaseoliformis, Vesicomya cordata, Calyptogena n. sp. (Gulf of Mexico), C. kaikoi, C. nautilei, C. solidissima and C. soyoae (Type-A). However, specimens variously identified as: V. gigas, C. kilmeri, C. pacifica, and V. lepta comprised two “species complexes”, each composed of multiple evolutionary lineages. Most taxa are limited to hydrothermal-vent or cold-seep habitats, but the “vent” versus “seep” clams do not constitute separate monophyletic groups. Current applications of the generic names Calyptogena, Ectenagena, and Vesicomya are not consistent with phylogenetic inferences. Received: 24 July 1997 / Accepted: 22 August 1997     

Bite forces and evolutionary adaptations to feeding ecology in carnivores

The Carnivora spans the largest ecological and body size diversity of any mammalian order, making it an ideal basis for studies of evolutionary ecology and functional morphology. For animals with different feeding ecologies, it may be expected that bite force represents an important evolutionary adaptation, but studies have been constrained by a lack of bite force data. In this study we present predictions of bite forces for 151 species of extant carnivores, comprising representatives from all eight families and the entire size and ecological spectrum within the order. We show that, when normalized for body size, bite forces differ significantly between the various feeding categories. At opposing extremes and independent of genealogy, consumers of tough fibrous plant material and carnivores preying on large prey both have high bite forces for their size, while bite force adjusted for body mass is low among specialized insectivores. Omnivores and carnivores preying on small prey have more moderate bite forces for their size. These findings indicate that differences in bite force represent important adaptations to and indicators of differing feeding ecologies throughout carnivoran evolution. Our results suggest that the incorporation of bite force data may assist in the construction of more robust evolutionary and palaeontological analyses of feeding ecology.     

Temporal resolution in the eyes of marine decapods from coastal and deep-sea habitats

 Temporal responses of eyes from four decapod species taken from sublittoral (Pandalus montagui Leach), coastal [Nephrops norvegicus (L.)] and deep-sea [Paromola cuvieri (Risso) and Chaceon (=Geryon) affinis A. Milne Edwards and Bouvier] habitats were examined. The electroretinogram responses to a range of sinusoidal intensity modulations between 0.5 and 40 Hz were recorded. Recordings were made from individuals adapted successively to two background light intensities. The sublittoral and coastal species showed faster responses when adapted to the higher light level and they also responded best to intermediate frequencies. When adapted to the lower light level, all species responded most strongly to low-frequency stimuli. Physiological and ecological reasons for the differences in responses are suggested. Received: 2 July 1999 / Accepted: 26 October 1999