4 resultados para Womens studies|Nursing|Individual
em Plymouth Marine Science Electronic Archive (PlyMSEA)
Resumo:
Chemical interactions play a fundamental role in the ecology of marine foodwebs. Dimethyl sulfide (DMS) is a ubiquitous marine trace gas that acts as a bioactive compound by eliciting foraging behavior in a range of marine taxa including the copepod Temora longicornis. Production of DMS can rapidly increase following microzooplankton grazing on phytoplankton. Here, we investigated whether grazing-induced DMS elicits an increase in foraging behavior in the copepod Calanus helgolandicus. We developed a semi-automated method to quantify the effect of grazing-mediated DMS on the proportion of the time budget tethered females allocate towards slow swimming, typically associated with feeding. The pooled data showed no differences in the proportion of the 25 min time budget allocated towards slow swimming between high (23.6 +/- 9.74%) and low (29.1 +/- 18.33%) DMS treatments. However, there was a high degree of variability between behavioral responses of individual copepods. We discuss the need for more detailed species-specific studies of individual level responses of copepods to chemical signals at different spatial scales to improve our understanding of chemical interactions between copepods and their prey.
Resumo:
Nematodes from a mud-flat in the river Lynher estuary, Cornwall, U.K., have a population density ranging between 8 and 9 106 m2 in the winter months, corresponding to a dry weight of 14 and 16 g m2. They reach a peak abundance of 2286 106 m2 (34 g) in May. About 40 species are present, and the species composition remained seasonally stable over the period of study. Analysis of age-structure suggests that the major species have continuous asynchronous reproduction. Respiration rates of 16 species have been determined at 20 C using Cartesian diver respirometry. For five species, respiration/body size regressions were obtained in the form log10R = log10a+b log10V, where R = respiration in nl O2 ind1 h1 and V = body volume in nl: Mesotheristus setosus (log10a = 004,b = 074), Sphaerolaimus hirsutus (log10a = 011, b = 068), Axonolaimus paraspinosus (log10a = 000, b = 079), Metachromadora vivipara (log10a = 059, b = 107), Praeacanthonchus punctatus (log10a = 000, b = 055). For the remaining 11 species, several animals were used in each diver and, by assuming b = 075, log10a values were calculated: Viscosia viscosa (log10a = 0188), Innocuonema tentabundum (0012), Ptycholaimellus ponticus (0081), Odontophora setosa (0092), Sphaerolaimus balticus (0112), Dichromadora cephalata (0133), Atrochromadora microlaima (0142), Cylindrotheristus normandicus (0150), Terschellingialongicaudata (0170), Sabatieria pulchra (0197), Terschellingia communis (0277). These values are compared with recalculated values for other species from the literature. Annual respiration of the nematode community is 2801 O2 m2, equivalent to 112 g carbon metabolised. Community respiration is compared with figures from N. American saltmarshes. At 20 C, a respiration of about 61 O2 m2 year1 g1 wet weight of nematodes appears to be typical. Annual production is estimated to be 66 g C m2. The correlation between feeding-group, body-size, habitat and the repiration rate of individual species is discussed.
Resumo:
Certain physiological differences between individuals in different populations of the mussel, Mytilus edulis, are described. In particular, the scope for growth differs in space and time and may be used to assess the animals' physiological condition. When the required measurements are made in the field, the rates of growth predicted from the physiological data agree well with observed rates of growth. An alternative approach utilizes mussels transplanted to various waters, with indices of condition then measured in the laboratory under standard conditions; an example of this approach is illustrated. Laboratory experiments are used to equate various levels of physiological condition with fecundity, in an attempt to equate physiological effects on the individual with likely population damage. A cytochemical index of stress is described, based on the latency of lysosomal enzymes; spatial variability in this index, and its relation with the scope for growth, are discussed. Finally, the results of some experiments on the effects of petroleum hydrocarbons on mussels are described and the presence of inducible activity of NADPH-dependent tetrazolium reductase in the blood cells is demonstrated. Certain considerations that apply in adopting similar measurements of biological effects of pollution in environmental monitoring programmes are discussed.
Resumo:
Many established models of animal foraging assume that individuals are ecologically equivalent. However, it is increasingly recognized that populations may comprise individuals who differ consistently in their diets and foraging behaviors. For example, recent studies have shown that individual foraging site fidelity (IFSF, when individuals consistently forage in only a small part of their population's home range) occurs in some colonial breeders. Shortterm IFSF could result from animals using a winstay, loseshift foraging strategy. Alternatively, it may be a consequence of individual specialization. Pelagic seabirds are colonial centralplace foragers, classically assumed to use flexible foraging strategies to target widely dispersed, spatiotemporally patchy prey. However, tracking has shown that IFSF occurs in many seabirds, although it is not known whether this persists across years. To test for longterm IFSF and to examine alternative hypotheses concerning its cause, we repeatedly tracked 55 Northern Gannets (Morus bassanus) from a large colony in the North Sea within and across three successive breeding seasons. Gannets foraged in neritic waters, predictably structured by tidal mixing and thermal stratification, but subject to stochastic, windinduced overturning. Both within and across years, coarse to mesoscale (tens of kilometers) IFSF was significant but not absolute, and foraging birds departed the colony in individually consistent directions. Carbon stable isotope ratios in gannet blood tissues were repeatable within years and nitrogen ratios were also repeatable across years, suggesting longterm individual dietary specialization. Individuals were also consistent across years in habitat use with respect to relative sea surface temperature and in some dive metrics, yet none of these factors accounted for IFSF. Moreover, at the scale of weeks, IFSF did not decay over time and the magnitude of IFSF across years was similar to that within years, suggesting that IFSF is not primarily the result of winstay, loseshift foraging. Rather, we hypothesize that site familiarity, accrued early in life, causes IFSF by canalizing subsequent foraging decisions. Evidence from this and other studies suggests that IFSF may be common in colonial centralplace foragers, with farreaching consequences for our attempts to understand and conserve these animals in a rapidly changing environment.
