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1.
The reproductive biology of some serolid isopods from the Antarctic   总被引:2,自引:1,他引:1  
Summary Several species of serolid isopod from Signy Island, South Orkney Islands and also from South Georgia were studied, and aspects of their reproductive behaviour and associated morphology are discussed. InSerolis polita Pfeffer egg-laying took place at a mean age of 28 months, and the eggs were then incubated in a ventral marsupium for a period of 20 months before the release of juveniles in the spring. The mean egg dry weight at spawning was 0.68 mg forS. polita and 3.35 mg forSerolis cornuta Studer. The egg weight increased during marsupial development due to the uptake of minerals, but the total calorific content fell. Within each species brood size was linearly related to female size and the mean number of eggs varied from 40 forS. polita to 232 forSerolis pagenstecheri Pfeffer. There was no detectable marsupial mortality.S. polita appeared to breed repeatedly at two-year intervals, butS. cornuta probably only breeds once. The reproductive biology of Antarctic serolids is compared with that of temperate isopods, and it is shown that they produce larger young which is related to their larger adult size. The extremely protracted period of marsupial incubation is associated with the need to synchronize reproduction with the seasonal nature of Antarctic primary production.  相似文献   

2.
The distributions of 24 marine and estuarine isopods have been reviewed. Lironeca ovalis, Aegathoa medialis, Olencira praegustator, and Probopyrus pandalicola were the only parasitic species found. Of the 20 free-living isopods, Asellus communis and Chiridotea almyra were the only fresh to brackish water species, and Chiridotea arenicola, C. stenops, Cirolana impressa, C. polita and Edotea montosa were the true marine species. The salinity range of Cyathura burbancki was extended and the range of Chiridotea stenops was extended northward while the ranges of Chiridotea nigrescens and C. arenicola were extended southward. The contribution of isopod distributions to the concept of a shallow water Transatlantic zoogeographic province is discussed.  相似文献   

3.
Antarctic marine invertebrates live in a cold, thermally stable environment and cannot tolerate large changes in body temperature (i.e. they are stenothermal). Their temperate relatives, by contrast, are eurythermal, living in warmer and thermally more variable environments. Have these different environments influenced how specific behaviours are affected by changes of temperature? This question was addressed in two temperate crustaceans, the decapod Carcinus maenas and isopod Ligia oceanica, and two Antarctic crustaceans, the isopod Glyptonotus antarcticus and amphipod Paraceradocus gibber. The thermal dependence of walking speed was analysed by contrasting the slopes of the linear part of each species’ behavioural curve. Over the temperature ranges analysed, the temperature sensitivity of walking speed in the stenotherms was 13–23% that of the eurytherms when measured in body lengths s?1. There was a linear relationship between walking speed and temperature up to +4.5°C in the Antarctic species G. antarcticus and P. gibber. Elevating temperature by up to 3.5°C above the maximum temperature experienced in the Antarctic (+1°C), does not lead to an acute breakdown of motor coordination. We describe for the first time the righting behaviour of G. antarcticus. The mean time-to-right tended to a minimum on warming from ?2 to+5°C, but this trend was not statistically significant. Our results suggest that the physiological adaptations which permit continued activity at low Antarctic temperatures have resulted in a lower thermal dependence of activity in Antarctic species, compared to related temperate species.  相似文献   

4.
Citrate synthase is a regulatory enzyme of the energy metabolism pathway controlling the citric acid cycle. It was studied in order to determine modes of enzyme regulation with regard to the life-style of the investigated species. Citrate synthase from crustaceans with different life-styles were compared: the pelagic euphausiids Euphausia superba from the Antarctic and Meganyctiphanes norvegica from the Scandinavian Kattegat and the Mediterranean were compared to the benthic isopods Serolis polita from the Antarctic and Idotea baltica from the Baltic. Citrate synthase was partly purified chromatographically and the influence of adenosine 5′-triphosphate on enzyme activity was examined. Mechanisms of inhibition and inhibitor constants were determined. Two different mechanisms of enzyme regulation by ATP were found. Citrate synthase from isopods was only competitively inhibited, while citrate synthase from euphausiids showed not only competitive inhibition but also activation by low concentrations of ATP. This activation is equivalent to the reversed methanism of uncompetitive inhibition. The ecophysiological relevances of the coupling of these mechanisms are discussed. The degree of competitive inhibition was different in the two groups of investigated crustaceans. Inhibitor constants were similar within the euphausiids but not in isopods, which showed higher or lower inhibition depending on the climatic zone: the colder the ambient temperature the lower the ATP inhibition. A possible mechanism of temperature adaptation through effects of varying inhibition constants is concluded.  相似文献   

5.
When the selective environment differs geographically, local herbivore populations may diverge in their host use ability and adapt locally to exploit the sympatric host population. We tested whether populations of the marine generalist herbivore Idotea baltica have diverged in host us ability and whether they locally adapted to exploit the sympatric population of their main host species, the bladderwrack Fucus vesiculosus. We fed isopods from three local populations reciprocally with the sympatric and two allopatric populations of the host. The bladderwrack populations varied in their quality as food for isopods suggesting variation in the selective environment. The ability to exploit the main host showed considerable divergence among the isopod populations. There was no significant interaction between host and isopod origin, indicating that the patterns observed in the reciprocal feeding experiment could be explained by differences in overall suitability of the hosts and differences in overall performance of the isopod populations. Isopod population that was sympatric to a bladderwrack population with low phlorotannin content showed high performance on the algae from the sympatric but low performance on the algae from the two allopatric populations. Performance of isopods, especially in this population, decreased quickly with the increasing phlorotannin content of food algae. We therefore hypothesize that the isopods adapted to a low phlorotannin content were unable to utilize high-phlorotannin algae efficiently. Isopod populations sympatric to the high-phlorotannin bladderwrack populations may be generally better adapted to deal with phlorotannins, being thereby able to utilize a range of bladderwrack populations.  相似文献   

6.
SUMMARY 1. We used a combination of field surveys and field and laboratory experiments to examine the effects of predatory small-mouthed salamander larvae, Ambystoma barbouri (Kraus and Petranka), on the density and microhabitat use of benthic isopods, Lirceus fontinalis (Rafinesque).
2. A survey of four field stations yielded a significant negative relationship between the densities of salamander larvae and isopods.
3. A field experimental manipulation of salamander density confirmed that salamanders reduce isopod density and isopod use of open micro-habitat. Salamanders did not significantly affect the mean or coefficient of variation in isopod size.
4. A laboratory experiment showed that in the absence of refuges for isopods, salamanders were capable of eating large numbers of isopods; small isopods were particularly vulnerable to salamander predation.  相似文献   

7.
In this study, we evaluated the effect of entomopathogenic nematodes (EPNs) Steinernema carpocapsae, Steinernema feltiae and Heterorhabditis bacteriophora, symbiotically associated with bacteria of the genera Xenorhabdus or Photorhabdus, on the survival of eight terrestrial isopod species. The EPN species S. carpocapsae and H. bacteriophora reduced the survival of six isopod species while S. feltiae reduced survival for two species. Two terrestrial isopod species tested (Armadillidium vulgare and Armadillo officinalis) were found not to be affected by treatment with EPNs while the six other isopod species showed survival reduction with at least one EPN species. By using aposymbiotic S. carpocapsae (i.e. without Xenorhabdus symbionts), we showed that nematodes can be isopod pathogens on their own. Nevertheless, symbiotic nematodes were more pathogenic for isopods than aposymbiotic ones showing that bacteria acted synergistically with their nematodes to kill isopods. By direct injection of entomopathogenic bacteria into isopod hemolymph, we showed that bacteria had a pathogenic effect on terrestrial isopods even if they appeared unable to multiply within isopod hemolymphs. A developmental study of EPNs in isopods showed that two of them (S. carpocapsae and H. bacteriophora) were able to develop while S. feltiae could not. No EPN species were able to produce offspring emerging from isopods. We conclude that EPN and their bacteria can be pathogens for terrestrial isopods but that such hosts represent a reproductive dead-end for them. Thus, terrestrial isopods appear not to be alternative hosts for EPN populations maintained in the absence of insects.  相似文献   

8.
Microplastic (MP) is an environmental burden and enters food webs via ingestion by macrofauna, including isopods (Porcellio scaber) in terrestrial ecosystems. Isopods represent ubiquitously abundant, ecologically important detritivores. However, MP-polymer specific effects on the host and its gut microbiota are unknown. We tested the hypothesis that biodegradable (polylactic acid [PLA]) and non-biodegradable (polyethylene terephthalate [PET]; polystyrene [PS]) MPs have contrasting effects on P. scaber mediated by changes of the gut microbiota. The isopod fitness after an 8-week MP-exposure was generally unaffected, although the isopods showed avoidance behaviour to PS-food. MP-polymer specific effects on gut microbes were detected, including a stimulation of microbial activity by PLA compared with MP-free controls. PLA stimulated hydrogen emission from isopod guts, while PET and PS were inhibitory. We roughly estimated 107 kg year−1 hydrogen emitted from the isopods globally and identified their guts as anoxic, significant mobile sources of reductant for soil microbes despite the absence of classical obligate anaerobes, likely due to Enterobacteriaceae-related fermentation activities that were stimulated by lactate generated during PLA-degradation. The findings suggest negative effects of PET and PS on gut fermentation, modulation of important isopod hydrogen emissions by MP pollution and the potential of MP to affect terrestrial food webs.  相似文献   

9.
The endogenous activity rhythms of the South African endemic isopod Exosphaeroma truncatitelson were explored. Isopods were collected on days coinciding with either a neap or spring tide. High- and low-energy beaches, which vary in the intensity of wave action, were selected as study sites. Isopods, in groups of 10–30, were placed in glass tanks with different experimental conditions: darkness + no sand, darkness with sand and natural ambient light (no sand). Activity of the isopods was measured for 50 h by recording the number of isopods swimming actively during a 30-s period. These isopods exhibited an endogenous activity rhythm which coincided with the tidal cycle even though removed from their natural habitat. Cosine curves were fitted to the observed activity data and statistical differences across variables were investigated. Peak activity was shown to occur shortly after high tide. Similar activity cycles were observed for both neap and spring tides and for different times of the year. Results also indicated that the activity cycles at both low- and high-energy beaches were similar. Two survival advantages of this rhythm are proposed: prevention of stranding on high shores and competitive avoidance with other local isopod species.  相似文献   

10.
The Australasian burrowing isopod (Sphaeroma quoianum) has been introduced to numerous embayments along the Pacific coast of North America. In some bays, populations of S. quoianum can exceed tens of thousands of individuals m−3 and bioturbation by the isopods can exacerbate shoreline erosion. Within their native range, however, studies recognize S. quoianum primarily as a woodborer. We measured the distribution, prevalence, habitat use, density, and associated fauna of S. quoianum in two bays within the native range [Tamar estuary (Tamar), Tasmania and Port Phillip Bay (PPB), VIC, Australia] and in one bay where the isopods had been introduced (Coos Bay, OR, USA). Distribution, prevalence, and habitat use were determined from shoreline surveys. Densities and the associated fauna of S. quoianum were measured in three intertidal substrata (marsh bank, wood, and friable rock). In all embayments, S. quoianum occurred primarily between 5 and 30 salinity and 55−68% of sites harbored isopods. Habitat use varied between embayments. Distributional patterns suggest salinity is the primary factor that limits the establishment and spread of S. quoianum. Isopod densities in all substrata were greater in Coos Bay than in the Tamar or PPB, although only densities within marsh banks varied significantly. Similarities in the amount of habitat and food, and the burrow dwelling lifestyle of S. quoianum suggest habitat availability/quality, food levels, predation, and competition are not responsible for the large differences in density. Lack of parasites or disease in populations of S. quoianum introduced to Coos Bay could be responsible for the prolific densities observed.  相似文献   

11.
  • 1.1. First-generation laboratory animals of three populations of the isopod Porcellio scaber, collected from a reference wood, a zinc smelter area and a lead mine site, were compared with respect to effects of Cd.
  • 2.2. All populations reacted differently to Cd-contaminated food: increased Cd concentrations in the food resulted in decreased consumption and growth for the reference isopods; mine isopods were not affected by Cd and for the smelter animals Cd stimulated growth at an intermediate concentration.
  • 3.3. Since Cd concentrations in the isopod did not differ between populations, adaptation is probably based on an increased detoxification capacity.
  • 4.4. The assimilation of Cd did not affect the Cu or Zn content of the isopods although the adapted isopods regulated their Cu content on a lower level than reference isopods.
  相似文献   

12.
We examined the effect of isopod size and age on the success of an acanthocephalan infection and on the effects of that infection on the growth and survival of the isopods. Groups of isopods (Asellus aquaticus) belonging to 4 size classes (juveniles, maturing adults, young adults, and older adults) were exposed to infective acanthors of Acanthocephalus lucii. At the end of the experiment, survival of the isopods, lengths of male and female isopods, and numbers of different developmental stages of A. lucii larvae in infected isopods were assessed. Acanthocephalus lucii prevalence was significantly lower in juvenile isopods than in adults. Intensity of infection increased with the size of isopods at exposure, and cystacanth intensity correlated positively with isopod size at the end of the experiment. Exposed juveniles and maturing adults survived significantly better than unexposed individuals, but the opposite was true of the 2 largest size classes. At the end of experiment, exposed isopods, and, especially, cystacanth-infected isopods, were significantly larger than unexposed isopods in every size class. We suggest that isopod size not only affects the success of A. lucii infection but also affects the ability of A. lucii to affect the survival (and perhaps the growth) of the isopod hosts.  相似文献   

13.
Populations of Serolis polita Pfeffer and S. cornuta Studer were studied over a continuous period of 2 yr at Signy Island, South Orkney Islands. Moult classes were recognized by a combination of morphology and size-frequency analysis and the method is described. The size of moult classes was very stable for S. polita but showed marked annual variation in S. cornuta. The moulting regimes of six other species of Serolis are discussed. An assessment was made of the losses associated with ecdysis and it was found that ≈25% of the dry weight and 42% of the ash content was lost at each moult. The seasonal breeding regime allowed the recognition of cohorts in the population and the growth rate was determined. In S. polita, growth in winter was significantly slower than in summer, and this is considered to be due to reduced food availability. The growth of Antarctic species of Serolis is compared with that of temperate isopods, and it is found that the former tend to show larger body size, slower growth, and greater longevity. All three features are discussed as symptoms of adaptation to the polar environment.  相似文献   

14.
Composition and spatial distribution of organic and inorganic materials within the cuticle of isopods vary between species. These variations are related to the behaviour and habitat of the animal. The troglobiotic isopod Titanethes albus lives in the complete darkness of caves in the Slovenian Karst. This habitat provides constant temperature and saturated humidity throughout the year and inconsistent food supply. These conditions should have lead to functional adaptations of arthropod cuticles. However, studies on structure and composition of cave arthropod cuticles are rare and lacking for terrestrial isopods. We therefore analysed the tergite cuticle of T. albus using transmission and field-emission electron microscopy, confocal μ-Raman spectroscopic imaging, quantitative X-ray diffractometry, thermogravimetric analysis and atomic absorption spectroscopy. The ultrastructure of the epicuticle suggests a poor resistance against water loss. A weak interconnection between the organic and mineral phase within the endo- and exocuticle, a comparatively thin apical calcite layer, and almost lack of magnesium within the calcite crystal lattice suggest that the mechanical strength of the cuticle is low in the cave isopod. This may possibly be of advantage in maintaining high cuticle flexibility and reducing metabolic expenditures.  相似文献   

15.
1. We examined whether the isopod, Lirceus fontinalis, an important facultative shredder in low-order streams in the eastern United States, responded to chemical cues of the skin mucus of five fish species varying in relatedness and feeding habits, and if fish-induced alterations in the foraging activity of isopods indirectly affected leaf processing. 2. In the laboratory, isopods generally responded to the presence of fish mucus by reducing their activity. Isopods were most responsive in water containing the skin mucus of predatory sunfish (Lepomis) and least responsive in water treated with mucus from algivorous stonerollers (Campostoma anomalum). 3. Rates of leaf disc breakdown by isopods in the laboratory were significantly reduced when isopods were exposed to chemical cues of confined green sunfish (L. cyanellus). 4. The rate of leaf processing in a fishless reach of a headwater stream was four to five times greater by isopods 7—10mmTL (total length) than those ≤ 5mm TL. Rates of leaf processing by isopods in low-order streams may be affected directly by the size structure of the isopod population and indirectly by the presence of fish.  相似文献   

16.
Summary The feeding behaviour of four sympatric isopods from a Hong Kong forest has been investigated. The study included two armadillids (Formosillo raffaelei and Orodillo maculatus) and two philosciids (Burmoniscus ocellatus and Burmoniscus sp.). When given a choice of eight types of litter, all isopod species showed significant dietary selection, and food preferences were similar. Berchemia racemosa (Rhamnaceae) was most readily consumed, followed by Celtis sinensis (Ulmaceac), while feeding rates on Cinnamomum camphora (Lauraceae) were low. The armadillids exhibited a narrower dietary spectrum than the philosciids. All isopods showed significant differences in consumption rates when each litter type was presented separately to them. Cinnamomum camphora was eaten the slowest, while Celtis sinensis and Berchemia racemosa were the top-ranked species. Although patterns of litter ranking based on percentage eaten or feeding rates were similar, all isopods ate more food when given a mixture of leaves than when presented with a single litter type. Assimilation rates were, in general, positively related to feeding rates. On this basis, it appears that assimilation may influence food preference. There were no clear relationships between food preference or feeding rates and ash, calcium, copper, soluble tannin or energy content of the litter. This finding may indicate the benefits of isopods maintaining a mixed diet, consuming certain litter species to meet their calcium or copper requirements and then switching to others so as to meet daily energy needs and to avoid excessive injection of tannins or plant allelochemicals.  相似文献   

17.
The marsupium of the Antarctic giant isopod, Glyptonotus antarcticus Eights 1853, has unique characteristics. It deviates in its proportions and construction from the so called Idotea type of brood pouch found in other marine isopod species; some features even remind you of the so called Porcellio type of marsupium which is typical of terrestrial isopods. Details are described by scanning electron microscopy. From our observations and from reviewed data, we suggest that, during the prolonged incubation of brood, adelphophagy contributes to the nourishment of the developing young, and assume that additional nutrition is provided by maternal secretion. These suggestions would partly explain marsupial conditions in G. antarcticus as an adaptation to slow development in an adverse environment. Two species of epizoa, a turbellarian and a fish leech, were found to occur on G. anarcticus in the vicinity of the marsupium.Contribution No. 561 of the Alfred-Wegener-Institute of Polar and Marine Research (AWI Bremerhaven)  相似文献   

18.
Chifu Huang  Andrew Sih 《Oecologia》1991,85(4):530-536
Summary We used a complete block design to experimentally study direct and indirect interactions in a three trophic-level freshwater system consisting of a top predator, the green sunfish, Lepomis cyanellus, an intermediate predator, small-mouthed salamander larvae, Ambystoma barbouri, and prey, hatchling isopods, Lirceus fontinalis. This system occurs naturally in small stream pools in central Kentucky; experiments were done in laboratory pools. Salamander larvae ate isopods and thus had a direct, negative effect on isopod survival. Accordingly, isopods responded to the presence of salamander larvae by increasing their tendency to bury themselves in the sand substrate. Fish ate salamanders and thus had a direct, negative effect on salamander survival. Salamanders responded to fish presence by increasing their time spent under plexiglass plates that simulate refuge rocks. The overall effect of fish on isopods depended on the presence of salamanders. In the absence of salamanders, fish predation on isopods had a direct, negative effect on isopod survival; isopods thus responded to the presence of fish by burying themselves in the sand. With salamanders present, fish had a positive overall effect on isopod survival; i.e., direct, negative effects of fish on isopods were outweighed by indirect, positive effects. Indirect positive effects of fish on isopods came through a reduction in salamander predation rates on isopods in the presence of fish. The mechanism involved both a decrease in the number of salamanders (a trophic-linkage indirect effect; cf. Miller and Kerfoot 1987) and a reduction in the feeding rate of individual salamanders on isopods (a behavioral indirect effect). The decrease in individual salamander feeding rates on isopods was due to reductions in both salamander activity and in spatial overlap between salamanders and isopods in the presence of fish. The latter effect reflected the fact that salamanders and isopods used different refuges from fish; salamanders went under refuge plates, whereas isopods primarily buried themselves in sand. Estimates of the relative importance of various direct and indirect effects of sunfish on isopods suggested that positive, behavioral indirect effects were of roughly the same magnitude as direct, negative effects, both of which were more important than were trophic-linkage indirect effects. Contrary to expectations, the presence of isopods did not affect the refuge use or survival of salamanders in the presence of fish.  相似文献   

19.
Abstract Granivory (seed feeding) evolved in many animal groups. Field observations hint at the existence of granivory in terrestrial isopods (Crustacea: Isopoda: Oniscidea), for which it was previously unknown. In this paper granivory in terrestrial isopods is addressed for the first time, focusing on (i) seed acceptance in the presence of plant litter and (ii) size as a constraint for acceptance and consumption. In a laboratory choice experiment, Armadillidium vulgare consumed seeds of Capsella bursa‐pastoris and Poa annua when plant litter was present. In a no‐choice experiment, seeds of seven plant species were offered to four isopod species giving 13 combinations in total [A. vulgare (seven species of seeds), Oniscus asellus (two), Porcellio scaber (two), and Porcellionides pruinosus (two)]. The tested isopods differed in their acceptance (proportion of individuals consuming seeds) and consumption (both number and amount of seeds eaten) of seed species. Size as a constraint was demonstrated in A. vulgare offered Cirsium arvense seed, since the probability that this large seed was eaten increased with body size of the isopod. In the other 10 seed–isopod pairs, seed consumption increased linearly with isopod body size. Granivory is thus widespread in terrestrial isopods, although the tendency to eat seeds differs between species.  相似文献   

20.
The aerial prop roots of the neotropical red mangrove,Rhizophora mangle L., begin growing well above highest high water (HHW) and often extend well below lowest low water (LLW) before rooting in the benthic substratum. In Belize, Central America, prop roots growing below LLW are colonized by diverse assemblages of organisms, including macroalgae, hydrozoans, ascidians, sponges, anemones, hard corals, and isopod crustaceans. Mangroves, root-fouling epibionts, root herbivores, and benthic predators engage in complex interactions that are major determinants of mangrove growth and production. Species richness of root epibionts increases with distance from the mainland and with proximity to the barrier reef. Species richness decreases with variability in water temperature and salinity. Ascidians and sponges transplanted from Lark Cay into the coastal Placencia Lagoon failed to survive, but anemones from Lark Cay survived in Placencia Lagoon. Reciprocal transplants survived off-shore. The gastropod predator,Melongena melongena L., present only in mainland estuaries, reduced local barnacle abundance and epibiont species richness in Placencia Lagoon. Isopod species richness also increases with distance from shore, but the number of roots bored by these species decreases. These isopods can reduce root relative growth rate (RGRroot) by 55%. On off-shore cays, sponges and ascidians ameliorate negative effects of isopods. In mainland estuaries where epibionts are less common, isopod damage to roots is more severe. Experimental studies in mangrove swamps throughout the world would clarify the importance of plant-animal interactions in these widespread tropical ecosystems.  相似文献   

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