The shelter defense dynamics of reproductively active (Form I) male red swamp crayfish Procambarus clarkii (Girard) were investigated by staging serial intrusions by male, maternal or non-maternal female conspecifics after one day of residence. The male residents showed a direct contest advantage only against non-maternal females, and won a significantly higher proportion of the encounters against non-maternal females than against either male or maternal female intruders. However, there was no significant difference in success against male or maternal female intruders. Further experiments against male intruders showed that increasing male prior residence to either 2 or 4 days did not significantly improve the residents' proportion of successful encounters. A final experiment revealed extremely low shelter fidelity in male P. clarkii, the most likely reason why male shelter defense against conspecific males and maternal females is not successful. These results, combined with those of past research, suggest that non-maternal females, juveniles and recently molted conspecifics are most vulnerable to predation and cannibalism, since males and maternal females easily out-compete non-maternal females for shelter, and adults out-compete juveniles. These findings may have implications for P. clarkii aquaculture and general management. 相似文献
The troglobitic amphipod crustacean Crangonyx antennatus occupies mud-bottom pools and small, gravel-bottom streams in caves in the southern Appalachians. One large, mud-bottom pool
population in Lee Co., Virginia was observed periodically from 1967 to 1975. Amphipods in this population frequently burrowed
into the soft mud substrate, where they were able to survive desiccation during periods when the pool dried up. Animals kept
in the laboratory also burrowed and survived desiccation during an experiment which simulated drought conditions similar to
those observed in caves. Amphipods collected from both pool and stream habitats burrowed, thereby indicating that stream-adapted
populations of this species still retain sufficient flexibility to survive under variable environmental conditions that might
be encountered in nature. It is concluded that burrowing provides a means of survival for C. antennatus when it is sometimes exposed to drought conditions in cave pool habitats and also provides protection from potential terrestrial
predators under similar conditions. Burrowing also offers amphipods protection from aquatic predators (such as salamander
larvae) during normal water levels and possibly allows juveniles a means of escaping cannibalism by adults. 相似文献
Some properties of gonad-inhibiting hormone (GIH) from the eyestalks of male Cancer magister have been examined with normal and eyestalkless female Crangon crangon as test animals. GIH is neither sex- nor species-specific, is thermostable and is dialyzable through cellophane membranes. It has a molecular weight of about 2000. 相似文献
Metabolic rates provide an estimate of the cost of living for different organisms that can readily be compared across species to provide an estimate of their relative requirements for survival. As such, metabolic rates have been measured for decades on a wide range of organisms. Here, we review published estimates of metabolic rates for brachyuran crabs, a ubiquitous and ecologically and economically important group of consumers. Consistent with ecological theory and results in many other groups of animals, and after controlling for phylogenetic relationships, crab metabolic rates scale with body mass with a scaling exponent of 0.65. Similarly, as with other groups of poikilotherms, crab metabolic rates increase strongly with temperature, with a Q10 of 1.26. Additionally, we found that metabolic rates were correlated with ecological niche, varying with both the diet strategy and the habitat occupied. These results help clarify the relative risk to crabs from environmental changes that impose metabolic stress, including climate change and the proliferation of hypoxic zones. 相似文献
In 2012 and 2015, blooms of Alexandrium tamarense occurred in Tasmania, Australia, and paralytic shellfish toxins (PST) were identified in the hepatopancreas of Southern Rock Lobsters. The human health risk was unclear, because consumption data were not available for lobster hepatopancreas. Thus, the aim of this study was to investigate the types of lobster tissues consumed, hepatopancreas portion size, and consumption format (boiled, steamed, raw, etc.), for Tasmanian and South Australian recreational harvesters.
A significant proportion of harvesters (15%) eat lobster hepatopancreas, with the majority consuming it as a dipping sauce for cooked (boiled or steamed) lobster meat. Two different methods were used to estimate portion size, a recollection-based food consumption questionnaire (FCQ) and a prospective Food Diary – mean portion size estimates showed good agreement: 3.4 g and 4.8 g, respectively. These results are critical for assessing the exposure of recreational harvesters to acute contaminants, such as PST, in lobster hepatopancreas. Results from the FCQ showed that lobster hepatopancreas is not consumed as often as white meat, suggesting that exposure to contaminants in hepatopancreas may be less frequent than white meat. This should be considered when evaluating human health risk from repeated or long term (chronic) exposure to contaminants in lobsters. 相似文献
The dorsal heart of the Indian stick insect, Carausius morosus, is responsible for the anterograde flow of hemolymph to the aorta and into the body cavity. The contraction frequency of the insect heart is known to be influenced by several substances of neural source. Here, a semi‐exposed heart assay was employed to study the effect of an aminergic substance (octopamine) and three neuropeptides (C. morosus hypertrehalosemic hormone [Carmo‐HrTH], crustacean cardioactive peptide [CCAP], and proctolin) on heart contraction. The contraction frequency was measured as beats per minute in adults ligated between the head and the prothorax. All three investigated neuropeptides had a stimulatory effect on heart contraction that lasted approximately 6 min, after which the normal heart beat rate was restored. Proctolin and CCAP stimulated the rate of heart beat also in unligated stick insects, whereas Carmo‐HrTH was active only in ligated insects. The latter could suggest that when the stick insect is not ligated, a competing substance may be released from the head of C. morosus; the competing substance is, apparently, not physiologically active but it binds or blocks access to the receptor of Carmo‐HrTH‐II, thereby rendering the HrTH peptide “not active.” In ligated stick insects, 6.7 × 10?8 M Carmo‐HrTH‐II significantly increased the heart beat rate; higher doses resulted in no further increase, suggesting the saturation of the HrTH receptor. Octopamine inhibited the rate at which the heart contracted in a dose‐dependent manner; inhibition was achieved with 10?4 M of octopamine. 相似文献
Chitosan is a partially deacetylated polymer of N-acetyl glucosamine. It is essentially a natural, water-soluble, derivative
of cellulose with unique properties. Chitosan is usually prepared from chitin (2 acetamido-2-deoxy β-1,4-D-glucan) and chitin
has been found in a wide range of natural sources (crustaceans, fungi, insects, annelids, molluscs, coelenterata etc.) However
chitosan is only manufactured from crustaceans (crab and crayfish) primarily because a large amount of the crustacean exoskeleton
is available as a by product of food processing. Squid pens (a waste byproduct of New Zealand squid processing) are a novel,
renewable source of chitin and chitosan. Squid pens are currently regarded as waste and so the raw material is relatively
cheap. This study was intended to assess the functional properties of squid pen chitosan. Chitosan was extracted from squid
pens and assessed for composition, rheology, flocculation, film formation and antimicrobial properties. Crustacean chitosans
were also assessed for comparison. Squid chitosan was colourless, had a low ash content and had significantly improved thickening
and suspending properties. The flocculation capacity of squid chitosan was low in comparison with the crustacean sourced chitosans.
However it should be possible to increase the flocculation capacity of squid pen chitosan by decreasing the degree of acetylation.
Films made with squid chitosan were more elastic than crustacean chitosan with improved functional properties. This high quality
chitosan could prove particularly suitable for medical/analytical applications.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
Protozoan epibionts were found on specimens of the mysid Mysis relicta collected in Lake Lü?iai (Lithuania). These protozoans belong to three genera of ciliates: Vorticella, Dendrosoma and Tokophrya, and were located on the antennae, carapace, appendages and abdomen of the basibiont. The ciliates of the genus Vorticella had a bell‐shaped body, with concave‐type striations and a very long contractile stalk. The stalk joined the body via a truncated and overlapping zone. The macronucleus was J‐shaped, and the contractile vacuole was anterolateral. Only one ciliate species of Vorticella has been found on mysids, although on species other than M. relicta, and this is therefore the first record of Vorticella on M. relicta, and the second on the order Mysidacea. The ciliates of the genus Dendrosoma had an irregular body directly attached to the substrate. Finger‐like actinophores arose from the body, with a bundle of tentacles at their ends. The macronucleus ramified into branches that followed the actinophores. These ciliates were included in the species D. astaci. The presence of this ciliate represents the first record of this genus on Mysis relicta. The ciliates of the genus Tokophrya had a pyramidal body, the apical surface of which showed two conspicuous actinophores, with a short, longitudinally striated stalk joining to the body via a narrow unstriated band. The macronucleus was spherical or ovoid, centrally located, and there was an apical contractile vacuole. Only one previous study has referred to the presence of this genus on Mysis relicta, and the data contained in it were compared with those of the present study. The biometrical data and taxonomical position of the ciliate epibionts was considered. 相似文献