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1.
To investigate copepod nauplii ingestion rates on phytoplankton, we have adapted the traditional gut fluorescence technique as it can be used with lower gut pigment concentrations. With the improved technique, laboratory experiments were performed to estimate functional responses for nauplii of Calanus helgolandicus and Centropages typicus. Nauplii were raised from eggs to copepodites and the experiments were performed with stages NIV-NV. Gut evacuation rates and ingestion rates were measured on Isochrysis galbana at different concentrations. Specific ingestion rates ranged between 0.038–0.244 μg C μg−1 nauplii C d−1 for C. typicus and 0.041–1.412 μg C μg−1 nauplii C d−1 for C. helgolandicus. Both species showed a type III functional response, reaching a saturation concentration at around 600 μgC l−1 for C. typicus and 800 μgC l−1 for C. helgolandicus. An erratum to this article can be found at  相似文献   

2.
Observations from a one-person submersible (Wasp) in fall, 1982, revealed a persistent aggregation of non-migrating, Stage V copepodites of Calanus pacificus californicus Brodsky in a band 20±3 m thick at a depth of 450 m, about 100 m above the bottom of the Santa Barbara Basin, California. Copepod abundances, calculated from nearest-neighbor distances measured directly from the submersible, yielded maximum densities of 26×106 copepodites m-3. Quiescent behavior, low laminarinase activity, low protein content, high lipid content and evidence of low excretion rate all suggest that these copepodites were in a state of diapause. Diapausing C. pacificus californicus at other locations along the eastern Pacific coast were also captured in discrete depth plankton tows. Both the submersible observations and the net collections suggest that the dense aggregation of diapausing copepods we observed in the Santa Barbara Basin was a phenomenon associated with seasonal upwelling cycles, and that such aggregations occur during non-upwelling periods when food is scarce in surface waters. Numerous predators, especially the deep sea smelt Leuroglossus stilbius, were observed feeding upon the aggregated copepods; thus, in contrast to the conventional picture of surface-dominated food distribution, deep-water aggregations of C. pacificus californicus may support the mesopelagic community during periods of low food availability in surface waters.  相似文献   

3.
Patterns of feeding in a population of Heliaster helianthus (Lamarck), a common and dominant species of starfish indigenous to the Pacific South American coast, were investigated in an intertidal habitat in central Peru from October 1986 to April 1987. The H. helianthus population comprised individuals of 3.5 to 30.2 cm body size (diameter) with two modal size classes. The number of rays ranged between 18 and 40, and individuals with 31 to 33 rays accounted for ca. 42% of the total population. There was a higher rate of increase in ray number with body size amongst small individuals(<13.0 cm diam). H. helianthus is capable of feeding on more than one prey item at a time (average of 5.6 to 13.2 prey items handled, with several predators observed to hold >100), and both the number of prey individuals captured and the total prey biomass were significantly correlated with predator size. Amongst a total of 1132 feeding observations, the largest number of predators (an average of 85.4% of those feeding) were preying on the mussel Semimytilus algosus whilst another mussel, Perumytilus purpuratus, ranked second with 21,9% of predators feeding. The proportion of S. algosus in the diet increased from 65.4% in the smallest predator size-group (10.9 cm diam) to 91.2% in the largest (19.0 cm). In contrast, P. purpuratus and barnacles were more highly represented in the diet of small H. helianthus. The smallest size-group (10.9 cm) had low dietary overlap with larger sizes and less specialized prey utilization. Two geographically separated populations of H. helianthus in Peru and Chile showed contrasting patterns of prey utilization. S. algosus and P. purpuratus comprised 85.5 and 6.5% by number in the diet of the Peruvian population, respectively, whilst corresponding figures for the Chilean population were 8.3 and 60.5%, with barnacles attaining a higher share (22.6%). However, the total number of prey individuals per feeding predator was almost the same in Peru and Chile, with 10.0 and 10.7 individuals, respectively. H. helianthus individuals of different sizes occupy slightly different microhabitats within the intertidal area, which, coupled with differential spatial distribution of prey species, results in the predator population being able to utilize a wide range of resources.  相似文献   

4.
K. Raskoff 《Marine Biology》2002,141(6):1099-1107
Narcomedusae are the most common group of medusae in the mesopelagic depths of Monterey Bay, California. Numerous capture events of various prey taxa were recorded in situ and analyzed using the Monterey Bay Aquarium Research Institute's remotely operated vehicle "Ventana". In situ video analysis of the stomach contents of 82 Solmissus incisa and S. marshalli revealed 88 identifiable prey items. Most (88%) were gelatinous animals. Of these gelatinous prey, 60.3% were ctenophores, 20.5% were cnidarians, 12.8% were salps, 3.8% were chaetognaths, and 2.6% were polychaetes. Euphausiids accounted for 11.4% of the diet, but they were probably captured adventitiously, as the gut contents of ctenophore prey. The tentacle-first foraging behavior of the narcomedusae is an effective way to capture large, comparatively fast-moving prey, because the fluid disturbance caused by swimming is decoupled from the area of prey capture. This behavior contrasts with the prevailing models of feeding behavior in medusae. Stealth predation may be the dominant mode of capturing prey by medusae in the mesopelagic depths of the oceans.  相似文献   

5.
T. Ikeda  K. Hirakawa 《Marine Biology》1996,126(2):261-270
Life cycle of the mesopelagic copepod Pareuchaeta elongata was investigated combining laboratory rearing data on the eggs, nauplii, and early copepodites with field growth data on the late copepodites. Examination and incubation at near the in situ temperature (0.5°C) of egg sacs collected from the field indicated that the clutch size was 13 to 24 eggs (mean: 20), hatching time was 39.4d (mean), and hatchability was low (mean: 28.5%). The development time at 0.5°C was 2.4 d for Nauplius Stage 1 (N1), 4.6 d for N2, 6.2 d for N3. 7.4 d for N4, 7.1 d for N5, 20.8 d for N6, 36.7 d for Copepodite Stage 1 (C1) and 65.3 d for C2. From the numerical analysis of seasonal samples collected from the field, the development time was estimated as 1 mo for C3, 2 mo for C4 and 2.5 mo for C5. Thus, the egg hatching time plus the integrated development time by stage was 355 d or nearly 1 yr (i.e. span of one life cycle). Duration of the C6 (adult) was estimated as>2.5 mo. Combining the present data on development times of each stage with published data on the major spawning season (August to October) and ontogenetic migration, a schematic representation of the life cycle of this copepod was developed. Between-stage comparison of wet, dry, and ash-free dry weights of all developmental stages of preserved wild specimens revealed that there is almost no gain in weight during naupliar stages, and the greatest weight increment over the life cycle was during the C4 stage. The present results are compared with those for the same and related species living in other regions.  相似文献   

6.
Vertical distribution, life cycle, and developmental characteristics of the mesopelagic copepod Gaidius variabilis Brodsky in the Oyashio region were investigated by combining analyses of field copepodite populations with laboratory-rearing data of egg hatching and naupliar development. Field samplings from five discrete depths between the surface and ≤2000 m were made approximately every month for 1 year. Most populations of G. variabilis occurred between 600 and 1000 m depth. A modest degree of reversed diel vertical migration behavior and some stage-specific depth-distribution patterns were noted. All copepodite stages were observed throughout the year, suggesting a year-round spawning of G. variabilis. From a prominent abundance peak of Copepodite Stage 1 (C1) seen in June to August, together with development times of eggs and nauplii obtained in laboratory-rearing experiments, the major spawning season was extrapolated to be April to June, the phytoplankton bloom season. Tracing the peak abundance of each copepodite stage (distinguishing males and females for C4 to C6), the generation times of males and females were deduced as 2 and 1 year, respectively. All between-stage increments in terms of wet-, dry-, and ash-free dry weights were greatest in C3/C4, and least in C5/C6 for both males and females. The increments in C3/C4 and C4/C5 were greater for males than for females, reflecting a longer stage duration of the males. These weights did not increase in C5/C6 males, possibly because feeding ceased in C6 males. These results for G. variabilis are compared with those for some mesopelagic copepods previously reported from other regions. Received: 25 October 1999 / Accepted: 20 March 2000  相似文献   

7.
During a repeat grid survey and drogue study carried out in the Lazarev Sea in the austral summer of 1994 to 1995, a sudden collapse of a rich population of the tunicate Salpa thompsoni was observed at the onset of a phytoplankton bloom. This may have been related to the inability of salps to regulate their filtration rate and avoid clogging of their filtering apparatus at particle concentrations ≥1 mg (chlorophyll a) m−3. It was at this stage that large numbers of salp individuals had their branchial cavities invaded by the copepod Rhincalanus gigas. Incubations, to compare the feeding rates of R.␣gigas in the presence and absence of salps, showed that copepods are able to utilize the high concentrations of microplankton accumulated in the food strand of the salp, thus enhancing their grazing efficiency. This is likely to represent a typical form of opportunistic parasitism. However, the timing of the invasion, and the observation that most salps could survive prolonged exposure to R. gigas invasion, suggest that the association may also constitute a novel type of symbiosis. S.␣thompsoni could potentially benefit from R. gigas cleaning its filtering apparatus when clogging due to high particle concentrations occurs. Received: 15 July 1996 / Accepted: 20 July 1996  相似文献   

8.
Using the marine harpacticoid copepod Tigriopus californicus, the effects of phytoplankton feeding deterrents and toxins were differentiated and measured. Eight compounds were tested for feeding deterrence and toxicity responses: four apo-fucoxanthinoids (apo-10′-fucoxanthinal, apo-12′-fucoxanthinal, apo-12-fucoxanthinal, and apo-13′-fucoxanthinone) and four well-known phycotoxins (domoic acid, okadaic acid, microcystin-LR, and a mixture of PSP-1 toxins). Since several of these compounds exhibited both feeding deterrence and toxicity, a model was developed to deconvolute the observed toxicity response from the observed feeding deterrence response, and to classify these compounds based on the degree of toxicity and/or feeding deterrence they exhibited towards T. californicus. Microcystin-LR, the PSP-1 toxins, and the four apo-fucoxanthinoids behaved only as feeding deterrents at low concentrations. Okadaic acid exhibited both toxicity and feeding deterrence at low concentrations, with the threshold concentration for feeding deterrence at a lower level than the threshold concentration for toxicity. Domoic acid acted only as a toxin at low concentrations, with all decreases in feeding resulting from the death of the copepod. Received: 4 November 1996 / Accepted: 3 December 1996  相似文献   

9.
The feeding ecology of Maurolicus muelleri, Lampanyctodes hectoris and Diaphus danae was examined from samples collected from continental slope waters of eastern Tasmania between April 1984 and April 1985. A total of 2 232 stomachs was analysed. M. muelleri, L. hectoris and D. danae fed primarily on euphausiids and secondarily on copepods, although larger D. danae (> 60 mm standard length) fed on other lanternfish (chiefly L. hectoris). The diets of M. muelleri and L. hectoris overlapped substantially. Diet overlaps between D. danae and the former species was low, however, due to the large biomass of fish present in D. danae. The prey taxa consumed changed with time of year and predator size. Stomach fullness (feeding intensity) varied seasonally in all three species, but only M. muelleri showed significant diel differences in fullness. The synchronization of the size structure of the predator populations and their feeding intensity, with seasonal variations in preferred prey, is proposed as a mechanism whereby each species maximizes its share of the available food resources.  相似文献   

10.
Quantification of feeding rates and selectivity of zooplankton is vital for understanding the mechanisms structuring marine ecosystems. However, methodological limitations have made many of these studies difficult. Recently, molecular based methods have demonstrated that DNA from prey species can be used to identify zooplankton gut contents, and further, quantitative gut content estimates by quantitative PCR (qPCR) assays targeted to the 18S rRNA gene have been used to estimate feeding rates in appendicularians and copepods. However, while standard single primer based qPCR assays were quantitative for the filter feeding appendicularian Oikopleura dioica, feeding rates were consistently underestimated in the copepod Calanus finmarchicus. In this study, we test the hypothesis that prey DNA is rapidly digested after ingestion by copepods and describe a qPCR-based assay, differential length amplification qPCR (dla-qPCR), to account for DNA digestion. The assay utilizes multiple primer sets that amplify different sized fragments of the prey 18S rRNA gene and, based on the differential amplification of these fragments, the degree of digestion is estimated and corrected for. Application of this approach to C. finmarchicus fed Rhodomonas marina significantly improved quantitative feeding estimates compared to standard qPCR. The development of dla-qPCR represents a significant advancement towards a quantitative method for assessing in situ copepod feeding rates without involving cultivation-based manipulation.  相似文献   

11.
The sea urchin strongylocentrotus drobachiensis exhibited a high degree of food selectivity, whether foods were presented singly or in combination. Foods ranked from most to least preferred were, in summer, Laminaria longicruris, Chondrus crispus, Corallina officinalis, Ascophyllum nodosum, and Agarum cribrosum, whereas in winter A. nodosum and A. cribrosum exchanged ranks. Food preference was not correlated with caloric content but, because of higher feeding rates on preferred foods, caloric intake was positively correlated with preference. Similarly, food absorption rankings were not correlated with food preference, with the exception of gravimetric efficiencies in winter. However, the absorption of L. longicruris, the most preferred alga, was highest in all measurements. Growth and reproductive development of S. drobachiensis on single species diets were positively correlated with food preference. Highest values occurred with animals fed L. longicruris. Urchins transferred from non-preferred to preferred diets showed increased somatic and reproductive growth compared to control animals on the original, non-preferred diets. Conversely, when transferred from preferred to non-preferred diets, urchins showed reduced growth compared to controls. No combination diet tested supported significantly better gonadal growth than L. longicruris: 25% C. crispus supported slightly better somatic growth than L. longicruris alone. These data support the view that S. drobachiensis has evolved a feeding strategy resulting in the maximization of growth and reproduction.  相似文献   

12.
Feeding and burrowing ecology of two East African mangrove crabs   总被引:4,自引:0,他引:4  
The behavior and ecology of two mangrove crabs,Sesarma meinerti De Man, 1887 andCardisoma carnifex (Herbst, 1794) were investigated at the beginning of the rainy season (October–November 1988) at Mida Creek, Kenya. Both species occupy upper intertidal levels, above mean high-water neap, and completely overlap in their zonation. Each burrow lasts ca. 3 wk, with no significant difference between the species. Both are more active around dusk and dawn and also follow a similar trend in their foraging activity, but differ in that burrowing is mainly diurnal inC. carnifex and nocturnal inS. meinerti. A hierarchy of food preference, established by offeringC. carnifex andS. meinerti leaves of five mangrove species, proved similar for both, withBruguiera gymnorhiza ranking first andAvicennia marina last, but significant only forC. carnifex. A rough estimate of the amount of litter consumed by these two species and of the soil mixed up by their burrowing activity indicates that they play a role of primary importance in the ecology of East African mangroves.  相似文献   

13.
S. M. Haq 《Marine Biology》1972,15(3):221-235
The breeding of Euterpina acutifrons, a marine harpacticid copepod, was studied both in the laboratory and in the natural population round Anglesey, England, with special reference to dimorphic males. As a result of successful rearing of the species under laboratory conditions, rates of development at different temperatures, and survival and maturation of all types of adults were studied. The dimorphic males developed faster than the females, and the small males had a shorter development time than the larger individuals. Laboratory observations clearly indicated that the males differ markedly in sexual behaviour, the small male being more potent, readily copulating with females, and always very active in breeding. In natural populations, temperature was found to have a limiting influence on the breeding period. Breeding began when the temperature reached 15° to 16°C, and ceased when it fell to 8°C. The most significant feature was the production of small males in nature; they increased in number with the onset of breeding, and always formed a high proportion of the actively breeding population. Both laboratory and field investigations have shown that the small male is a breeding form, and is apparently an adaptation of the species for carrying out successful breeding in the colder areas of its distribution.  相似文献   

14.
We examine the feeding ecology of characteristic micronekton species inhabiting the mid-slope region (~700 to 1,500 m depths) off southern Tasmania. Five fishes, Diaphus danae, Hygophum hanseni, Lampanyctus australis (Myctophidae), Phosichthys argenteus (Phosichthyidae) and Chauliodus sloani (Chauliodontidae), were sampled by depth-stratified midwater trawling on a diel and seasonal basis. Overall, 74 prey taxa were identified from 2,132 stomachs. Euphausiids (mostly Euphausia spinifera and E. similis) and calanoid copepods (mostly Pleuromamma species) were the main prey of the three myctophids; P. argenteus ate fishes and decapods in addition to the euphausiids, while C. sloani ate only fishes. Copepods were less important in the diets of larger D. danae, L. australis and P. argenteus and were replaced by euphausiids in the myctophids and by fishes in P. argenteus. In autumn, when euphausiid biomass increased six-fold, all three myctophids and P. argenteus fed most intensively and consumed a high proportion of euphausiids. The three myctophids appeared to feed nocturnally. Differences in the timing and duration of feeding corresponded to differences in their spatio-temporal overlap with key prey. Daily rations of H. hanseni (1.93% dry-weight biomass) and L. australis (1.43%), estimated from data on stomach fullness, were typical for temperate myctophids and higher than that of the non-migratory P. argenteus (0.43%). The vertical flux of near-surface plankton production to the mesopelagic food web is based primarily on diel feeding in the upper water column (<500 m) rather than consumption of species that migrate seasonally into the deeper mesopelagic zone. Because species such as P. argenteus and C. sloani feed above the third trophic level, their predators, including the commercially important orange roughy, are feeding between levels four and five.  相似文献   

15.
Fricke  H.  Hissmann  K. 《Marine Biology》2000,136(2):379-386
One concept of evolutionary ecology holds that a living fossil is the result of past evolutionary events, and is adapted to recent selective forces only if they are similar to the selective forces in the past. We describe the present environment of the living coelacanth Latimeria chalumnae Smith, 1939 at Grande Comore, western Indian Ocean and report depth-dependent cave distribution, temperature, salinity and oxygen values which are compared to the fish's distribution and its physiological demands. We studied the activity pattern, feeding behaviour, prey abundance and hunting success to evaluate possible links between environmental conditions, feeding ecology and evolutionary success of this ancient fish. Transmitter tracking experiments indicate nocturnal activity of the piscivorous predator which hunts between approximately 200 m below the surface to 500 m depth. Fish and prey density were measured between 200 and 400 m, both increase with depth. Feeding tracks and feeding strikes of the coelacanth at various depths were simulated with the help of video and laser techniques. Along a 9447 m video transect a total of 31 potential feeding strikes occurred. Assuming 100% hunting success, medium-sized individuals would obtain 122 g and large females 299 g of prey. Estimates of metabolic rates revealed for females 3.7 ml O2 kg−1 h−1 and for males 4.5 ml O2 kg−1 h−1. Today coelacanths are considered to be a specialist deep-water form and to inhabit, with their ancient morphology, a contemporary environment where they compete with advanced, modern fish. Received: 5 July 1999 / Accepted: 11 November 1999  相似文献   

16.
The feeding ecology of lanternfish Benthosema pterotum (Alcock) from the north Arabian Sea, Mozambique and the Bay of Bengal was studied. Samples were collected on cruises carried out by R.V. Dr. Fridtjof Nansen during the period 1978 to 1983. A wide variety of zooplankton organisms were identified in the diet of B. pterotum with crustanceans dominating the diet. Copepods constituted ca. 40 to 90% of the diet. Dry weight analyses of the stomach contents from the Gulf of Oman in February 1983 showed copepods to be 35 to 55% in weight (average in samples). Ontogenetic differences were observed in the diet. Prey size increased as the fish length increased, but the largest fish did not exclude the smaller prey organisms from their diet. Regional variation in diet was also shown in B. pterotum. The degree of filling and the state of digestion of stomach contents revealed that this species feeds intensively at night in the epipelagic layer. All copepods indentified were epipelagic species, providing additional evidence of diurnal pattern in the feeding chronology of B. pterotum. Identification of copepods from the Gulf of Oman in February 1983, revealed that herbivorous species dominated in biomass. Quantitative analyses show that B. pterotum probably have a daily food intake of ca. 4.5% of the body weight.  相似文献   

17.
Feeding ecology of Greenland halibut (Gr. halibut) (Reinhardtius hippoglossoides) and sandeel (Ammodytes sp.) larvae on the West Greenland shelf was studied during the main part of the productive season (May, June and July). Copepods were the main prey item for larval Gr. halibut and sandeel, constituting between 88 and 99% of the ingested prey biomass. For both species, absolute size of preferred prey increased during ontogeny. However, preferred copepod size in relation to larval length differed markedly. In Gr. halibut, the relative size of the prey declined during growth of the larvae, while it remained constant for sandeel at a level of 2.7% of larval length. This led to a reduction in prey niche overlap between the two species. The available prey copepod biomass differed distinctly across the shelf area. In May, the prey density of Gr. halibut was the highest in the off-shelf area in Davis Strait. In June and July, the prey-rich areas for both species were mainly located at the slopes of the banks and at the shelf break area. Gut fullness was higher in these areas than in neighbouring areas, suggesting that the larval food resource could be scarce. The feeding ecology of Gr. halibut and sandeel could explain why larval abundance indices of the two species have historically shown opposite responses to yearly environmental conditions and total zooplankton occurrence.  相似文献   

18.
The gut contents of dominant deep-sea benthic boundary layer zooplankton (primarily copepods and mysids) and the vacuole contents of phaeodarians collected and preserved in situ at four depths (from 724 to 3112 m) on an eastern tropical Pacific seamount (Volcano 7; 13°23N, 102°27W) between 23 November and 4 December 1988 were analyzed using transmission electron microscopy (TEM). Suspended, and sinking plus resuspended particles, were quantitatively sampled to characterize potential food sources. The broad oxygen minimum characteristic of this region intersects the summit of the seamount and affects the feeding ecology of these organisms. Several copepods and mysids and an amphipod contained guts packed with what appeared to be gram-positive bacteria, an unusual finding. We hypothesize that the source of these bacteria-like bodies was a mat or aggregate that originated in the oxygen minimum or at its upper or lower interface. The presence of the bacteria-like bodies in 43 to 100% of the particlefeeding zooplankton that were sectioned and that had gut contents, suggests that the bacteria-like bodies are an important food source. The diverse gut and vacuole contents of other detritivores were similar among depths. Particles and microorganisms from the depths were also similar. This finding can be explained by the rapid sinking of particles and aggregates from surface waters and their relatively intact transit through the broad oxygen minimum with its reduced populations of zooplankton. The presence of algal cells in guts and vacuoles of benthic boundary-layer zooplankton suggests that these zooplankton select particles of recent surface origin for consumption. The presence of the guts filled with bacteria-like bodies shows that some deep-sea copepods and mysids that are normally generalist feeders can specialize opportunistically. The similarity of gut contents of crustaceans and vacuole contents of phaeodarians suggests that these two very different groups of particle feeders utilize similar food sources in the deep sea.  相似文献   

19.
The trophic ecology of the stomiid assemblage (Pisces, Stomiiformes, Stomiidae) in the eastern Gulf of Mexico, a region with physical and biological characteristics typical of oligotrophic low-latitude regimes, was investigated. Over 1400 specimens representing 69 species and 17 genera were examined. Four patterns of feeding were evident among the abundant stomiids: (1) myctophid predation; (2) zooplankton/small micronekton predation; (3) penaeidean shrimp predation; and (4) copepod/micronekton predation. One rare species preyed on cephalopods. Il was concluded that stomiids exhibited a high level of prey-selectivity, particularly considering the broad range of prey types available in the eastern Gulf of Mexico. The absence of numerically dominant potential prey (e.g.Cyclothone spp., sternoptychids) in the diets of piscivorous stomiids is possibly a function of feeding periodicity coupled with stomiid vertical migration. Stomiids may feed at night in the upper 200 m on vertically migrating myctophids while disregarding co-occurring nonmigrating prey during the daytime. Integration of stomiid abundance and diet data suggests that: (1) stomiids are the dominant upper trophic-level predators of the Gulf of Mexico mesopelagial, (2) stomiids inflict the highest predation impact on myctophids in low-latitude midwater ecosystems, and (3) the historic use of predation-avoidance arguments to explain certain mesopelagic phenomena (e.g. vertical migration, ventral photophores) appears to be substantiated by estimates of stomiid predation-impact. The stomiids may serve as key trophic mediators in the transfer of energy from the mesopelagial to the bathyand benthopelagial.  相似文献   

20.
T. Ikeda 《Marine Biology》1990,107(3):453-461
The abundance and vertical distribution pattern of a halocyprid ostracod,Conchoecia pseudodiscophora, were investigated in the Japan Sea in 1985, 1987 and 1989. Vertical sampling from 500 m depth to the surface in the water around Yamato Rise revealed that this ostracod was second in dominance by number and third to fourth by biomass of the total zooplankton collected with a 0.35 mm mesh Norpac net. Horizontal net tows in Toyama Bay indicated that the major population ofC. pseudodiscophora was distributed below 250 to 300 m depth. No diel migration pattern was evident. Its contribution to total zooplankton there was 5 to 10% or more in terms of biomass. A total of five subadult instars (II to VI) and adult males and females were identified from instar analysis based on sizes and morphological characteristics of specimens collected with 0.10 mm mesh Norpac nets. Data on body length, wet weight and dry weight of each instar are presented. Carbon content of 35 to 48% of dry weight, and nitrogen content of 5.3 to 7.3% of dry weight, were recorded on fresh, freeze-dried specimens of selected instars (subadult Instars IV to VI, adult females). Water and ash contents of mixed specimens of these four instars were 76% of wet weight and 25% of dry weight, respectively. Feasibility of laboratory maintenance ofC. pseudodiscophora was tested, and it produced characteristic J shaped faecal pellets. Oxygen consumption rates of subadult instars V and VI, and adult female ranged 0.011 to 0.021µl O2 ind.–1 h–1 at 1 °C, or 2.9 to 6.1µl O2 (mg body N)–0.85 h–1 in terms of Adjusted Metabolic Rate (AMRo 2). There was no appreciable metabolic reduction inC. pseudodiscophora compared to other ostracods, despite their mesopelagic life mode. Subdominance in total zooplankton and nonreduced metabolic activity ofC. pseudodiscophora suggest that this species may be an important link in mesopelagic energy-flow and matter cycling in the Japan Sea.  相似文献   

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