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571.
The shore crab, Carcinus maenas L. (Portunidae), is a coastal and estuarine species, which can live and reproduce under brackish water conditions; freshly hatched larvae have been observed in the field at salinities below 15‰. In the present laboratory study, the tolerance of hypo-osmotic stress was experimentally investigated in early larvae of a marine (North Sea) population of C. maenas reared at four different salinities (15, 20, 25, 32‰). Two and 4 days after hatching, the Zoea I larvae were moult-staged microscopically, and their rates of respiration and growth (changes in dry weight, W, carbon, C, nitrogen, N, and hydrogen, H) were measured. Survival and development were monitored until the megalopa was reached: 15‰ did not allow for development beyond the first zoeal stage, while metamorphosis to the megalopa was reached at salinities ≥20‰. At 20‰, development was significantly delayed and mortality enhanced as compared with 25 and 32‰. Rates of growth and respiration decreased during exposure to reduced salinities ≤25‰. Hence, the suppression of growth could not be explained as a consequence of enhanced metabolic losses per larva. Instead, a partial C budget indicates that the Zoea I larvae suffered from decreased capabilities of assimilating ingested and subsequently converting assimilated matter to tissue growth. Net growth efficiency (K2, C-based) was at 25 and 32‰ initially high (>60% during the postmoult and intermoult stages of the Zoea I moult cycle), but decreased during the later stages (down to ≤30% in premoult). An inverse pattern of C partitioning was observed at ≤20‰, with initially low K2 values (≤21% during the first 2 days of the moult cycle), and a later increase (up to ≥46% in premoult). Thus, larval growth was initially suppressed under conditions of reduced salinity, but this was later (during premoult) partially compensated for by an increase in C assimilation and K2. Our observations indicate that Zoea I shore crab larvae react during the late stages of their moulting cycle less sensitively against reduced salinities than during postmoult and intermoult. This suggests that the transition between moult cycle stages C and D0 may be a critical point for effects of hypo-osmotic stress, similarly as already known in relation to effects of nutritional stress. Negative effects were found also when freshly hatched Zoea I shore crab larvae were exposed only transitorily (for 24–72 h) to 20‰, with significantly lower rates of survival, development, growth, respiration, and K2. These effects increased with increasing duration of initial exposure to reduced salinity. 相似文献
572.
573.
574.
Abstract The southern province of Guangdong has long been subject to endemic mosquito‐borne diseases. In recent years, this region of China has experienced rapid, extensive economic development involving environmental change, making much of the scant knowledge of its mosquito fauna obsolete. This paper reviews previous mosquito surveys, some of which may be too old to be of relevance to present‐day conditions, and presents the results of a recent survey of adult and immature mosquitoes. The main vectors of mosquito‐borne diseases endemic to the area, such as dengue and Japanese encephalitis virus, develop in container habitats. A three‐year survey was carried out, between 2004 and 2006, of 4131 breeding containers in residential areas and in open, sparsely populated areas, of which approximately 50% were positive for the presence of mosquitoes, and 10 156 larvae and pupae were collected and identified. Twelve species were found in both residential and sparsely populated areas: Aedes albopictus (Skuse) (Diptera: Culicidae), Ae. lineatopennis (Ludlow), Ae. vexans (Meigen), Tanakaius togoi (Theobald), Culex barraudi Edwards, Cx dispectus Bram, Cx malayi (Leicester), Cx pallidothorax Theobald, Cx quinquefasciatus Say, Cx sitiens Wiedemann, Lutzia fuscanus Wiedemann and Tripteroides bambusa (Yamada). Armigeres subalbatus (Coquillett) was found only in containers in villages, whereas Ae. macfarlanei Edwards, Cx mimeticus Noé, Cx sinensis Theobald, Cx vegans Wiedemann, Cx wilfredi Colless and Mansonia uniformis (Theobald) were found only in non‐ or sparsely populated areas. In residential areas, the rank order of most common species, as measured by the proportion of containers colonized, was Ae. albopictus > Cx quinquefasciatus > Lu. fuscanus, whereas in sparsely populated areas the rank order was Cx quinquefasciatus > Ae. albopictus > Lu. fuscanus. Light traps in non‐ or sparsely populated areas caught 5995 adult mosquitoes of 25 species, some of which are not container breeders. The most common species were: Anopheles sinensis Wiedemann, An. maculatus Theobald, An. minimus Theobald, Ta. togoi, Cx bitaeniorhynchus Giles, Cx malayi, Cx quinquefasciatus, Cx sinensis Theobald, Cx sitiens, Cx tritaeniorhynchus Giles and Lu. fuscanus. It is noteworthy that nine species caught had not been previously recorded in Guangdong Province, highlighting the deficient knowledge of the current composition and distribution of the mosquito fauna of this part of China. 相似文献
575.
The adaptive significance of leaf-mining pattern as an anti-parasitoid strategy: A theoretical study
Makoto Katô 《Population Ecology》1985,27(2):265-275
An adaptive significance of linear leaf mining patterns as the anti-parasitoid strategy is theoretically analysed. In the model, a leaf-miner is allowed to move in one of four ways; mining ahead in unexploited area of a leaf, backtracking, branching off from the backtracking mine, and crossing the previous mine. The model parasitoid searches for the leaf-miner by tracing the mine by the tactile cue of mine surface after detecting the mine. The average duration from detecting the mine to finding the leaf-miner host is calculated for various patterns of mining, changing numbers of branches and of crosses. This average duration becomes longer when the leaf-miner stays near either end of the mine compared with when staying near its center. It is also prolonged as the numbers of branches and of crosses increase. 相似文献
576.
Uric acid accumulates in the epidermis of Bombyx mori larvae and renders the larval integument opaque and white. Yamamoto translucent (oya) is a novel spontaneous mutant with a translucent larval integument and unique phenotypic characteristics, such as male-biased lethality and flaccid larval paralysis. Xanthine dehydrogenase (XDH) that requires a molybdenum cofactor (MoCo) for its activity is a key enzyme for uric acid synthesis. It has been observed that injection of a bovine xanthine oxidase, which corresponds functionally to XDH and contains its own MoCo activity, changes the integuments of oya mutants from translucent to opaque and white. This finding suggests that XDH/MoCo activity might be defective in oya mutants. Our linkage analysis identified an association between the oya locus and chromosome 23. Because XDH is not linked to chromosome 23 in B. mori, MoCo appears to be defective in oya mutants. In eukaryotes, MoCo is synthesized by a conserved biosynthesis pathway governed by four loci (MOCS1, MOCS2, MOCS3, and GEPH). Through a candidate gene approach followed by sequence analysis, a 6-bp deletion was detected in an exon of the B. mori molybdenum cofactor synthesis-step 1 gene (BmMOCS1) in the oya strain. Moreover, recombination was not observed between the oya and BmMOCS1 loci. These results indicate that the BmMOCS1 locus is responsible for the oya locus. Finally, we discuss the potential cause of male-biased lethality and flaccid paralysis observed in the oya mutants. 相似文献
577.
As part of studies investigating the influence of grazers on reef meiofauna, we assessed the density, composition and richness
of meiofauna (retained on a 100-μm sieve) on the leeward reef slope of Heron Reef, GBR, Australia using an airlift vacuum
sampling device. Estimates of meiofauna densities ranged between 40 individuals 10 cm−2 and 290 individuals 10 cm−2, which is considerably lower than many estimates from carbonate sediments and hard substrates from other reefs and marine
habitats. The 17 taxa of meiofauna were dominated by harpacticoid copepods (40%) and nematodes (32%). Varying sediment load
within algal turfs explained 37% of variation of meiofauna density. A model is proposed in which increased shelter afforded
by high living coral cover reduces meiofaunal losses from grazing and increases sediment loads, balanced by areas of low coral
cover in which sedimentation rates are lower and grazing rates higher. At none of the four sites did major differences in
abundance occur between November and March sampling events. Together these observations suggest that epilithic meiofaunal
communities are generally spatially and temporally predictable at small scales in this reef system, indicating that their
ecological services are similarly conservative.
Handling editor: I. Nagelkerken 相似文献
578.
Ishizue Adachi 《Population Ecology》1983,25(1):130-142
Summary Relative abundance of natural food resource, leaves of wild rose, ofArge migrinodosa was evaluated by comparing the food quantity which the larvae composing a colony utilized throughout the larval stage with
that which is available in the habitat. In this connection, behavioral pattern of larval feeding was also observed under natural
conditions, and its ecological significance was discussed.
It was quantitatively clarified that the larvae faced the severe shortage of food and had to disperse to other shoots with
the expense of probably high risk. Under pressures of such insufficient supply of food, the larvae follow the most efficient
pattern of feeding behavior that they move to the tip of shoot at first and feed regularly downward thereafter. Though individual
larvae behaved completely independently of each other, the aggregation appeared to be formed and maintained because all the
larvae from the same egg mass follow this fixed feeding pattern. 相似文献
579.
M. W. Miller K. L. Kramer S. M. Williams L. Johnston A. M. Szmant 《Coral reefs (Online)》2009,28(2):511-515
The generally slow and incomplete recovery of the long-spined sea urchin, Diadema antillarum, from the 1983–84 Caribbean-wide die-off, particularly in the Florida Keys, USA, raises the question of factors limiting
population recovery. This study sought to quantify larval settlement rates as an indicator of larval supply at two sites in
the Florida Keys, utilizing methods comparable to an historic study. Settlement at two sites in southwest Puerto Rico was
also examined as a comparison of present-day settlement rates at a site where D. antillarum recovery has been moderate. Monthly settlement rates were low (max < 2 m−2) and did not differ between the two sites examined in the Florida Keys. Settlement was significantly higher at only one of
the Puerto Rico sites (max 16 m−2), but still an order of magnitude lower than that reported for historic populations in Cura?ao (1982–83). Results are consistent
with the hypothesis of low larval supply limiting D. antillarum recovery in the Florida Keys. 相似文献
580.
Summary Fewer larvae ofMeloidogyne incognita invaded and fewer galls were formed when seedlings of nonresistant varieties of tomato, eggplant and chilli were growing in soil to which oilcakes of mahua, castor, neem/margosa, mustard and groundnut had been added. Chemical analysis of plant tissue showed that, compared with untreated plants, plants growing in treated soil contained greater concentrations of phenols and frequently of amino acids, proteins and carbohydrates. 相似文献