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1.
Three isopod species (Crustacea: Isopoda), commonly found in the intertidal and supratidal zones of the North American Pacific coast, were studied with respect to symbiotic microbiota in their midgut glands (hepatopancreas). Ligia pallasii (Oniscidea: Ligiidae) contained high numbers of microbial symbionts in its hepatopancreatic caeca. Numbers of endosymbionts were strongly reduced by ingestion of antibiotics. By contrast, the hepatopancreas of Idotea wosnesenskii (Valvifera: Idoteidae) and Gnorimosphaeroma oregonense (Sphaeromatidea: Sphaeromatidae) did not contain any microbiota. Results of feeding experiments suggest that microbial endosymbionts contribute to digestive processes in L. pallasii, the most terrestrial of the three isopods that we studied. The acquisition of digestion-enhancing endosymbionts may have been an important evolutionary step allowing isopods to colonize terrestrial habitats where relatively indigestible leaf litter is the primary food source. By contrast, the ability to digest phenolic compounds was most developed in one of the more marine species, suggesting that this trait may have evolved independently in isopod species that consume a phenolic-rich diet, whether in marine habitats or on land. Received: 28 August 2000 / Accepted: 8 December 2000  相似文献   

2.
In the carnivorous isopod Eurydice pulchra Leach the mid-gut caeca have a pH of 5.6 and produce a strong acid proteinase, a lipase and a carbohydrase. Electron microscope studies of the digestive caeca of starved and fed animals show that secretion is merocrine and may originate from a complex involving the basal cell membrane and associated mitochondria, producing lysosomes. Absorbed materials, in fed animals, appear to take the form of neutral lipid bodies, glycogen, and proteinaceous crystals, the latter forming within the golgi complex. Digestion of both lipid and protein inclusions was observed to occur intra-cellularly by fusion with free lysosomes. Secretion and absorption may occur in the same cell, and the scheme for the sequence of epithelial cell stages is proposed.  相似文献   

3.
An analysis of the horizontal and the vertical zonation of the Antarctic Isopoda, combined with knowledge of the geological history of Antarctica and isopod phylogeny, revealed that the isopod family Serolidae and subfamily Arcturinae are likely to have evolved from ancestors that inhabited a cold-temperate Gondwanian province. Antarctic species of other families, such as the Munnopsidae, Nannoniscidae, Desmosomatidae and Ischnomesidae, are likely to have evolved from deep-sea ancestors. It is deduced that emigration of South Patagonian species into the Southern Ocean, although possible, probably did not occur very often. Evolutionary phenomena such as continental-drift vicariance, radiation of species on the continental shelf of Antarctica, and active migration, including submergence and emergence mechanisms are discussed.  相似文献   

4.
New observations on the feeding behavior of Corophium volutator, collected from the Menai Strait, Anglesey, UK in 1981, show that detritus drawn into one entrance of the U-shaped burrow is pushed out at the opposing entrance either uningested or as faeces. Periodically, the amphipod turns around in the burrow and recommences feeding, so both the uningested material and the faeces may be reworked by the mouthparts. A feeding individual produces, on average, 16 faecal pellets every 10 min, at a seawater temperature of 18°C. When fed on detritus dyed with azo-carmine, approximately 12 pellets are produced before the foregut, intestine and hindgut are completely clear of previously ingested material and the dye appears in the faeces. Dye which enters the ventral caeca takes between 12 and 48 h to clear this tissue and, furthermore, it is only cleared when the amphipod is feeding. It is concluded that ingested coarse material is subjected only to a primary phase of digestion in the stomach, and that it takes 4 to 24 min to clear the gut. Fine material which enters the ventral caeca is subjected to a secondary phase of digestion and absorption which takes 24 to 48 h. Particles of thorium dioxide and ferritin incorporated in the diet are absorbed by the B- and ageing RF-cells in the ventral caeca. Non-specific esterases occur in the apical regions of the same cells, the mature cells of the anterior dorsal caeca and the cells at the anterior of the intestine. Protease activity is greatest in the lumen of the ventral caeca and the large vacuole of the B-cells. Apart from the lumen of the posterior caeca, there is some protease activity throughout the lumen of the gut. Carbohydrates were localised primarily in the R/F-cells towards the proximal region of the ventral caeca. Lipid was confined to the R/F-cells in the same region.  相似文献   

5.
A total of 38 219 specimens representing 63 species of marine isopods (Crustacea) from deep and shallow Arctic waters were studied in a search for epizoic foraminifers (Protozoa). Foraminifers occurred on 21 species, and their frequency was generally low. A total of 290 foraminifer individuals were found, of which 289 belonged to Cibicides wuellerstorfi, C. refulgens and Cibicides spp. (juveniles) (Cibicidae), while only a single individual belonged to Cornuspira sp. (Cornuspiridae). The foraminifers were most frequent on species of the families Munnidae, Ischnomesidae (suborder Asellota) and on Gnathia stygia (suborder Gnathiidea), but were totally absent from the asellote families Janiridae, Haploniscidae, Nannoniscidae and from the suborder Epicaridea. The foraminifers were mainly located on the legs (Munna acanthifera), the anterior part of the body (Haplomesus quadrispinosus, heteromesus frigidus), or on the head (G. stygia adults). The epizoic foraminifers occur mainly on epibenthic isopods, which do not or only rarely clean themselves. The foraminifers are known to prefer elevated substrata, and in this the habitat of the isopods and the foraminifers coincide. The size of individual isopods was not related to the presence or absence of foraminifers.  相似文献   

6.
Colidotea rostrata (Benedict, 1898) is the only known commensal idoteid isopod, living on and mimicking the color of two northeastern Pacific sea urchins of the genus Strongylocentrotus. The population dynamics and reproductive biology of C. rostrata on its host urchins were studied at a low rocky intertidal area in southern California (33°40N; 118°30W) from December 1984 to December 1986. Isopod populations remained relatively stable throughout the 2 yr study, with isopods inhabiting an average of 56.1% of the urchins at 6.1±0.6 (x±2 SE) isopods per urchin. Female isopods reach sexual maturity at a length of 6.8 mm. Fecundity in C. rostrata averaged 11.8±0.9 (x±2 SE) embryos per brood, and increased with female body size. Breeding occurs all year long in C. rostrata, with a main reproductive period between the warmer spring and summer months. Newly released mancas and juvenile isopods were present during all months of the study. C. rostrata differs from the free-living Idoteidae in its smaller maximum size, reduced fecundity, 1:1 sex ratio, and low juvenile mortality. These features may represent adaptations to a commensal life style that reflect a reduced mortality pressure on these isopods.  相似文献   

7.
8.
The coexistence of three idoteid species in Posidonia oceanica litter raises the question of trophic diversity and their role in the litter degradation process. Hence, diet composition of Idotea balthica, Idotea hectica and Cleantis prismatica was studied using a combination of gut contents and stable isotopes analysis. Gut content observations indicate that P. oceanica dead leaves are an important part of the ingested food for the three species, although their tissues are constituted of only a small to medium fraction of P. oceanica carbon. Our results also underlined the potential role of these species in the degradation of P. oceanica litter by mechanically fragmenting the litter and by assimilating a small to medium fraction of carbon. Moreover, we showed that there were considerable inter- and intra-specific differences in diet composition. Diet differed between juveniles and adults for I. balthica. Crustaceans are an important food source for adults of I. balthica, while I. hectica indicated a major contribution of algal material. C. prismatica showed an intermediate diet. This trophic diversity is probably one of the factors allowing these species to coexist in the same biotope.  相似文献   

9.
Structure and ultrastructure of the digestive tract of the ectoparasitic stages of the Antarctic isopod Gnathia calva, collected in the Weddell Sea and around the Antarctic Peninsula in the 1984–1985 season, are briefly described. There are only two digestive glands, with an ultrastructure similar to that of other isopods. The gut is divided into six regions: oesophagus, stomach, dilatable reservior for sucked-in blood, sphincter, rectal vesicle with symbiontic bacteria, and rectum. The highly dilatable anterior hindgut (reservoir) takes part in the resorption of nutrients and stores lipids and glycogen. The rectal vesicle has an epithelium with all the features of an organ with high metabolism and the capacity for the transportation of small molecules. The surface is increased by irregular microvilli. A very thin intima and a basal labyrinth are present. The presence of symbiontic bacteria is discussed in correlation with the haematophagous nutrition of G. calva.  相似文献   

10.
M. B. Jones 《Marine Biology》1972,14(3):264-270
The mouthparts of Jaera albifrons Leach, Jaera ischiosetosa Forsman, Jaera praehirsuta Forsman and Jaera forsmani Bocquet were examined with the light microscope and the Stereoscan electron microscope, and were found to be identical in all species. The structure of the mouthparts indicate that all four species feed by scouring and abrading algal or bacterial films from rocks or Fucus. Food, therefore, does not seem to be an isolating factor involved in the microdistribution of the four species on a shore.  相似文献   

11.
The food of four species of asellote isopods (Crustacea, Malacostraca), Haploniscus rostratus, Haploniscus unicornis, Acanthocope galatheae and Betamorpha fusiformis, was evaluated by analysis of their gut contents. The isopods were sampled at several stations on the abyssal plains of Guinea Basin, Angola Basin and Cape Basin (southeast Atlantic), the Weddell Sea abyssal plain and the Antarctic continental slope during the DIVA and ANDEEP expeditions in 2000, 2001 and 2005. While all species had mineral particles in their guts and mucus material was the most frequent food item, the remaining gut contents differed among species. Betamorpha fusiformis fed mostly on phytodetritus, especially in the Southern Ocean basins and ingested along with it whole calcareous foraminifers. Acanthocope galatheae showed some differences in gut contents between basins, but in the Guinea Basin, the contents were to a large extent stercomata, i.e., waste pellets of soft-walled foraminifers, i.e., the Komokiaceae. Indications were that the haploniscids were feeding on detritus and agglutinating foraminifers (stercomata). This indicates spatial differences in food availability for this diverse group of deep-sea isopods and the importance of poorly known foraminiferal groups, like the Komokiaceae, as a food source in the deep sea.  相似文献   

12.
The effects of cadmium (3CdSO4·8H2O), zinc (ZnSO4·7H2O) and lead [Pb (NO3)2] on mortality, and cadmium, zinc and mercury (HgCl2) on osmoregulation, have been recorded for marine and estuarine species of isopods (Crustacea). The marine species studied were Idotea baltica, I. neglecta, I. emarginata and Eurydice pulchra, which were adapted to 100, 80, 60 and 40% sea water (SW) (100% SW э 34‰ S). The estuarine species used were Jaera albifrons sensu stricto and J. nordmanni, which were adapted to 100, 50, 10 and 1% SW. Both groups of isopods have low mortalities in 100% SW with 10 and 20 ppm of cadmium, zinc and lead, but a decrease in salinity caused an increase in the toxicities of these metals and reduced the LT50 values (time, in hours, to 50% mortality). Mortalities at 10°C were generally higher than those recorded at 5°C. Cadmium had no significant effect on the osmoregulation of I. baltica and I. emarginata in 100 and 80% SW at 5°C, but this metal significantly lowered the blood osmotic concentration of I. neglecta in 80% SW. Zinc did not alter the haemolymph osmotic concentration of I. neglecta in 100 and 80% SW, but significantly lowered the blood osmotic concentration of I. baltica in 100% SW. Cadmium, zinc and mercury also significantly altered the osmoregulatory ability of J. albifrons in dilute saline.  相似文献   

13.
The male secondary sex characters of Jaera albifrons Leach, Jaera ischiosetosa Forsman, Jaera praehirsuta Forsman and Jaera forsmani Bocquet are described with the Stereoscan electron microscope (S.E.M.). These characters, which are present on the peraeopods, are the only means of identification for these Jaera species which together form the Jaera albifrons group (Isopoda, Asellota). The male praeoperculum (modified, fused, first pair of pleopods) and appendix masculinae (modified endites of the second pair of pleopods) have also been studied with the S.E.M. and possible functions of the various sex characters are discussed. Both the male operculum and appendix masculinae are similar for each species, suggesting that copulation with females of a different species is anatomically possible. The fact that hybrids are rarely collected in ecological investigations is discussed with reference to the present known information. Two methods of copulation for the members of this group have been proposed and these are discussed. A method of sperm transfer along the male operculum is outlined.  相似文献   

14.
The elementary composition (C, H, N) of Sphaeroma serratum and Sphaeroma hookeri has been studied in different natural populations and also in individuals maintained in laboratory cultures. Changes in elementary composition have been observed in the natural communities. Laboratory experiments demonstrated that food may influence the isopod's chemical composition. These results provide an explanation fom the intraspecific differences which appear to characterize natural populations.  相似文献   

15.
《Ecological modelling》1997,102(1):33-53
A population dynamics model was developed to simulate the effects of benthic macroalgae blooms (mostly Enteromorpha spp.) on the productivity of Cyathura carinata (Crustacea: Isopoda), a possible keystone species in the benthic communities of the Mondego estuary. The model describes C. carinata population dynamics, as well as the relationships between Enteromorpha biomass, Enteromorpha decaying rates, organic matter content in the sediments and detritus consumption by C. carinata, a detritic feeder. Model results support the idea that seasonal blooms of Enteromorpha determine a significant increase of organic matter content in the sediments, due to macroalgae decay, which initially contributes to enhance C. carinata consumption and growth rates, determining a significant increase in the biomass. Nevertheless, later, following the algae bloom, C. carinata biomass decreases, and reaches its lowest value, close to 0, when the algae crash. This effect is probably related with strong anoxic conditions, especially during night, due to high algal decomposition rates. In accordance with the model, migration of new individuals from adjacent areas must occur in order to recolonise the area affected by the algae bloom. Therefore, it seems reasonable to conclude that macroalgae blooms that are limited in space may favour C. carinata populations, but extensive blooms affecting the whole area of distribution of this species will determine its disappearance.  相似文献   

16.
Endo  Y. 《Marine Biology》1984,79(3):269-276
Biological characteristics of daytime surface swarming of Euphausia pacifica were investigated. Swarms in the Sanriku coastal waters consisted almost exclusively of mature individuals and seemed to be related to breeding behavior. Although maturation of ovarian eggs occurred both at the beginning and the end of the swarming period, females with attached spermatophore were most frequent at the end of the period. Since stomachs of swarming individuals were nearly empty throughout this period, swarming behavior was probably not related to feeding. Swarming individuals did not seem to be transported to the surface by vertical water movement caused by tidal streams, because the daily catch per boat did not differ between spring and neap tides.  相似文献   

17.
During submersible surveys along the continental slope (summers of 1991 and 1992, 184–847 m) between False Cape, Virginia, and Cape Hatteras, North Carolina, USA, we observed the aegid isopod, Syscenus infelix Harger, attached to the macrourid Nezumia bairdii (Goode and Bean). This is the first report of S. infelix attached to fishes in the western North Atlantic. The association of this blind isopod with its host appears species specific. The large, conspicuous isopod always attached to a fish in the same location, the dorsal midline, immediately behind the first dorsal fin. Attachment appears to be long term, with the isopod forming a characteristic scar consisting of a distinct discolored oval depression with seven small, dark impressions that coalesce as the fish grows. Only one S. infelix was found on each host fish. The isopod occurred on 23.7% of N. bairdii observed from submersible on the middle continental slope off Virginia and North Carolina, compared with 16.6% of 1236 museum specimens of the same species (based on inspection for scars) collected at latitudes 26°–64°N. Prevalence of the fish–isopod association was not correlated with depth or latitude. We also found identical scars on preserved specimens of N. aequalis (2.6% of 660 specimens), N. sclerorhynchus (1.2% of 86 specimens), and N. suilla (14.3% of 7 specimens), mostly from areas outside the range of N. bairdii. No scars were found on museum specimens of N. atlantica (n=27), N. cyrano (n=57), or N. longebarbata (n=7). The low incidence of isopod attachment on these species suggests that N. bairdii is the preferred host. Infestation by the isopod appears to result in erosion of host fish scales and tissue. We propose that S. infelix is an obligate associate of its host fish and should be considered parasitic. Received: 9 June 2000 / Accepted: 21 October 2000  相似文献   

18.
Group orientation in Neomysis mirabilis (Mysidacea: Crustacea)   总被引:2,自引:0,他引:2  
The orientational behaviour of the neritic mysid Neomysis mirabilis in a swarm is considered under natural and experimental conditions. In nature, the swarms exhibit elements of inner integration, such as homogeneous age structure, collective behaviour, and relative constancy of inter-individual spacing. The mysids are guided by combined optomotor and vibrotactile cues, determining their disposition in aquaria of different shapes. Maximum accuracy of spatial arrangement is observed in round vessels. It is suggested that the stress encountered in an aquarium produces responses comparable to those elicited by the presence of a predator. The rigid spatial arrangement at the supra-individual level is interpreted as evolutionally-optimized prey strategy. These elements in the geometrical distribution of individuals in mysid swarms are inherent in other pelagic crustaceans also, and are not controlled by random taxes stimulated by hydrological factors.  相似文献   

19.
Numerous stranding events of the euphausiid Nyctiphanes australis Sars on the coast of south-east Tasmania during the winter months of 1984/1985 are documented. The krill were at a reproductive stage of their life cycle. Strandings almost always occurred on calm, sunny days on beaches with a northerly aspect. Typically, barometric pressure was greater than and wind speed was less than the monthly average. No significant differences were found between stranded euphausiids and those from surface swarms, and the relationship between the two forms of behaviour in this area is discussed. A new form of behaviour termed matting was observed, in which the euphausiids aggregate dorsal-side down on the substrate in shallow water. Matting usually occurs synchronously with stranding. Laboratory experiments showed that N. australis responds to changes in both the plane of polarization and intensity of light with behaviour typical of that observed in stranding and matting events. Light appears to be a key factor mediating these types of behaviour. Hypotheses for the relationship between stranding and matting are offered.  相似文献   

20.
The ocypodid crab Ilyoplax pingi, observed in Kanghwa I., Korea in 1992, builds a mound at the burrow entrance, by piling mud dug out from the burrow. The mounds were made by both waving and non-waving males, and by both ovigerous and non-ovigerous females. The burrow diameter at the widest part tended to be larger in crabs with mounds than in crabs without mounds, whereas the burrow depth was not different between them. The mound density increased in the late exposure period, when the crabs' surface activities declined. Mound removal and rebuilding experiments revealed that the presence of the mounds has the effect of keeping neighboring crabs away.  相似文献   

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