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891.
892.
Piers Ettinger-Epstein Steve W. Whalan Christopher N. Battershill Rocky de Nys 《Marine Biology》2007,153(2):171-178
Determining the reproductive processes of benthic invertebrates is central to our understanding of their recruitment and population
dynamics. Sexual reproduction of the gonochoric and viviparous Great Barrier Reef sponge, Luffariella variabilis (Poléjaeff 1884) was quantified from histological samples collected over two reproductive seasons (2004 and 2005). Gametogenesis
commenced for females at a water temperature of 21°C, the lowest water temperature of the year. Spermatogenesis occurred above
22.5°C with sperm asynchronously developed and released from August or September to October. Oocytes developed asynchronously
from July to September, embryos from September to December, and larvae from November to December. Female reproduction terminated
in December (after larval release) prior to the highest mean annual water temperature of 30°C in January. There was a significant
(35%) decrease in female reproductive output in 2005 compared to 2004, as measured by the reproductive index (0.68 ± 0.12
female reproductive propagules mm−2 of mesohyl in 2005 compared with 1.05 ± 0.10 mm−2 in 2004). This corresponded with delayed oogenesis and spermatogenesis, and a shortened larval development cycle corresponding
with a delayed minimum temperature (21°C) in August of 2005 compared with July 2004. Accordingly, the maximum percentage of
the mesohyl occupied by female reproductive propagules (eggs, embryos and larvae) was also reduced by 60% in 2005 (overall
mean of 13.04% in October 2004 compared with 5.35% in October 2005). However, the mean sizes of individual female propagules
remained the same from year to year. Males in contrast, showed no overall difference in either reproductive index or percentage
occupation of the mesohyl between 2004 and 2005. The lowered reproductive output (∼35%) of females of L. variabilis associated with delayed minimum water temperatures may have important implications for population reproductive success where
oogenesis and spermatogenesis and larval release are cued by minimum and maximum water temperatures, respectively. 相似文献
893.
Total lipids, hydrocarbons, wax esters, triacylglycerols, and phospholipids were determined for 22 major biomass species of zooplankton and fish in an Antarctic mesopelagic community that were collected in 1982 and 1983. Lipid levels were similar to levels in more temperate mesopelagic species. Total lipid concentration was depth related, with all lipid-rich species being collected at depths greater than 230 m. Wax ester content in copepods (60 to 70% of the total lipid) was generally higher than in subtropical species. Lipids indicated three predator-prey relationships (Parandania boecki-Atolla wyvillei, Thysanoessa macrura-Calanoides acutus andEurythenes gryllus-Atolla wyvillei). These were confirmed by gut content analyses. The mesopelagic fishBathylagus antarcticus, Pleuragramma antarcticum, andProtomyctophum bolini stored most lipid intramuscularly, whereasElectrona antarctica andGymnoscopelus nicholsi contained extensive stores in subcutaneous lipid sacs. The intramuscular lipids inP. antarcticum and the subcutaneous lipid sacs ofE. antarctica were primarily wax esters, possibly used for increased buoyancy or long-term energy storage. Unlike the odd-carbon preference of aliphatic hydrocarbons which typifies terrestrial plants and temperate marine organisms, even-carbon chain-length paraffins predominate in 80% of the Antarctic species analyzed. Although the source of these even-carbon n-alkanes cannot be determined from our data, their dominance in the species analyzed suggests that an unusual biochemical pathway may be responsible for their synthesis in this ecosystem. 相似文献
894.
Changes in the level of the adenylates (ATP, ADP, AMP), arginine phosphate, arginine, octopine, D-lactate, succinate, and aspartate were determined in the foot of Cardium edule, after 12 h of anoxia and after aerobic recovery for up to 12 h. Control levels of the adenylates, the calculated energy charge and the arginine phosphate content were restored after about 1 h of recovery. On the other hand, the recovery of the D-lactate, succinate, and aspartate pools was a slow process, taking place over about 12h. 相似文献
895.
896.
We analyzed how offspring sex ratio varies with maternal condition in order to obtain evidence on the population structure in two aphid species with different life cycles. When fitness returns per unit investment differ for the production of daughters and sons, selection will favor an increasing investment into the sex with the higher returns. Therefore, the offspring sex ratios of individual mothers should become more biased towards the sex with the higher fitness returns as their condition or fecundity improves. The pattern of sex ratio adjustment we found in Uroleucon cirsii indicates local mate competition among males, while the pattern we found in Rhopalosiphum padi suggests local resource competition among sexual females. This might be the first evidence for local resource competition among females in an invertebrate species. Local mate competition means that fitness returns are limited by the availability of females as mates within local breeding groups, whereas local resource competition means that fitness returns are limited by the availability of resources for females competing within local groups. We discuss how the life cycles of both species fit to these hypotheses.
相似文献
Joachim L. DaggEmail: Phone: +49-551-393730Fax: +49-551-3912105 |
897.
Sergio Rodríguez Xavier Querol Andrés Alastuey Jesús de la Rosa 《Environmental Chemistry Letters》2007,5(1):1-7
This article synthesises the results obtained in several projects on atmospheric aerosol (particulate matter – PM) pollution
developed during the last years in the Western Mediterranean. It focuses on particulate matter sources and the strategies
for suitable monitoring in ambient air. The article has been structured in several sections that give response to the main
questions that prompted these studies. After analysing the main PM features in the Mediterranean, a brief review of the main
factors differentiating the particulate matter composition with respect to Central Europe is presented. Finally, the suitability
of the different metrics or parameters for monitoring ambient air PM levels in different types of environments is discussed.
Selected article from the 6th European Meeting on Environmental Chemistry, University of Belgrade, Serbia and Montenegro organized
by Prof. Dr. Branimir Jovancicevic (www.research.plymouth.ac.uk/ace). 相似文献
898.
Summary We investigated the role of the iridoid glycoside, catalpol, as a deterrent to the predator,Camponotus floridanus. Four laboratory colonies of this ant were offered buckeye caterpillars (Junonia coenia: Nymphalidae) raised on diets with and without catalpol. The same colonies were offered sugar-water solutions containing varying concentrations of catalpol, in both no-choice and choice tests. Regardless of diet, buckeye caterpillars appeared to be morphologically protected from predation by the ants, possibly because of their large spines or tough cuticle. However, buckeyes raised on diets with catalpol had high concentrations of catalpol in their hemolymph; extracts of this high-catalpol hemolymph proved to be an effective deterrent to the ants. When starved ants were not given the choice of food items, they were more likely to consume sucrose solutions that contained 5 mg catalpol/ml or 10 mg catalpol/ml than they were to consume solutions with 20 mg catalpol/ml. When they were given a choice of sugar solution or a sugar solution containing catalpol, the ants avoided solutions with catalpol at any of these concentrations. Ant colony responses to catalpol in sucrose solutions varied considerably over time and among colonies. 相似文献
899.
Fleur E. Champion de Crespigny Nina Wedell 《Behavioral ecology and sociobiology》2007,61(8):1229-1235
The maternally inherited bacterium Wolbachia pipientis generates strong reproductive incompatibilities between uninfected females and infected males (cytoplasmic incompatibility),
significantly reducing both female and male reproductive success. Such fitness costs are thought to place selective pressure
on hosts to evolve pre-copulatory preferences for mating with compatible mates, thereby enabling them to avoid the reproductive
incompatibilities associated with Wolbachia. Therefore, uninfected females are predicted to prefer mating with uninfected males, whereas infected males are predicted
to prefer mating with infected females. Despite these predictions, previous investigations of pre-copulatory mate preferences
in Wolbachia-manipulated Drosophila have not found evidence of female preference for uninfected or compatible males. However, none of these studies utilised
a design where focal individuals are provided with a simple choice in a relatively non-competitive situation. We examined
both female and male pre-copulatory mate preference based on mate infection status in Drosophila simulans and D. melanogaster using simple choice assays involving between 30–50 replicates per treatment. Although we found no evidence of female pre-copulatory
mate preferences in either species, male D. simulans exhibited some preference for mating with females of the same infection status. However, this preference was not evident
when we repeated the experiment to confirm this finding. Consequently, we conclude that neither male nor female D. melanogaster and D. simulans exhibit significant Wolbachia-associated pre-copulatory mate preferences. 相似文献
900.
Bert?H?lldoblerEmail author E.?David Morgan Neil?J.?Oldham Jürgen?Liebig Yue? Liu 《Chemoecology》2004,14(2):101-106
Summary. Dufour gland secretions of the harvester ants
Pogonomyrmex barbatus, P. rugosus
and P. maricopa were
investigated. The glandular blends exhibit species specific
patterns, but more importantly, based on indiviual profiles of
Dufour gland contents of colony members it is possible to
separate the colonies from each other in each species. It is
possible that these collective colony specific cues serve as
longer lasting trunk route markers. Behavioral tests demonstrate
that workers of P. rugosus
prefer homing routes marked by members of their own colony to routes marked
by a foreign conspecific colony. 相似文献