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971.
Ilie S. Racotta Elena Palacios Ana M. Ibarra José Luis Ramírez Fabiola Arcos Olivia Arjona 《Marine Biology》2008,153(6):1245-1256
Induction of triploidy in aquatic organisms has increased worldwide in the last two decades, mostly because triploids have
better growth than diploids. According to a physiological hypothesis, partial or total sterility of triploids allows the accumulation
of reserves in muscle and other tissues instead of being transferred to the gonad. The present study analyzes lipid, protein,
carbohydrate, and fatty acid levels in muscle and gonads of Nodipecten subnodosus triploids and diploids over 18 months from June 2001 to December 2002. An important increase in gonadosomatic index of diploids
scallops was observed from May to June 2002 reaching the highest values in August. Such increase was not observed in triploid
scallops. Changes in biochemical composition in female gonad were in general related to the accumulation of reserves during
gonad development of diploid scallops. This accumulation was lower for triploid scallops, in accordance to their sterility,
especially for carbohydrates and acylglycerides. Adductor muscle index as well as protein and carbohydrate levels in muscle
increased in both ploidy groups during the reproductive period indicating no mobilization of reserves to sustain gonad development
in both ploidy groups. These results partially support the physiological hypothesis on the advantage of triploids: in a rich
food locality no mobilization of reserves is needed to sustain gametogenesis. This, together with a possible lower efficiency
of energy assimilation at high food concentration for triploids, may be the reason for an apparent lack of superiority of
N. subnodosus triploids in terms of adductor muscle growth. Only the levels of particular highly unsaturated fatty acids levels (namely
20:4n-6 and 20:5n-3) in muscle of diploid and triploid decreased during the reproductive period, indicating a possible transfer of selected
fatty acids to gonads, even in triploids. The muscle of triploids has a slightly but significantly higher proportion of 22:6n-3 compared to diploids, which can have implications for the nutritional and commercial value of triploid adductor muscle. 相似文献
972.
973.
A. N. Maeda-Martínez 《Marine Biology》2008,154(4):643-648
Osmotic pressure and major ions (Cl−, Na+, Mg2+, Ca2+) of the egg capsule fluid in the slipper limpet Crepidula fornicata were investigated in relation to embryonic development. Calcium permeability of the capsule wall was studied at oviposition,
by dipping freshly laid egg capsules in 45Ca as a tracer. This study also determined total calcium content of the embryos at different developmental stages. Osmolarity
and major ion concentrations in egg capsule fluid were higher than seawater at uncleaved and trochophore stages, and then
dropped to the same level as sea water at veliger stage. Concentrations of Cl− and Na+ were relatively high at oviposition, peaked at trochophore stage, and finally dropped close to concentrations of seawater
at hatching. In contrast, concentrations of Mg2+ and Ca2+ decreased steadily during capsular development. Radiotracer permeability experiments in freshly laid egg capsules confirmed
that the capsule wall is impermeable to this ion at that stage. However, because of the dissolution of the inner layer of
the wall during the final part of capsular development, the wall becomes permeable to calcium and probably to the rest of
the major ions studied. 相似文献
974.
Lorenzo Pérez-Rodríguez 《Behavioral ecology and sociobiology》2008,62(6):995-1005
Carotenoid-based ornaments act as signals of quality in many animal species. In contrast to feathers, which are relatively
stable structures, carotenoid-pigmented integuments (e.g. bills, lores, tarsi) can change colour rapidly and may better reflect
changes in physiological condition. I studied the seasonal variations in plasma carotenoids in red-legged partridges (Alectoris rufa) kept on a constant diet and free of intestinal parasites. Furthermore, I analyzed whether seasonal changes in circulating
carotenoids were mirrored by the carotenoid-based coloration of eye rings and bill of this species. Plasma carotenoids showed
seasonal variation, with higher levels coinciding with the end of the mating and the start of the laying season. Eye ring
pigmentation was related to plasma carotenoid levels, and changes in bill hue (but not changes in UV or red bill chroma) mirrored
the variation in plasma carotenoids during the breeding season. Despite the seasonal variation, individual differences in
eye ring pigmentation and bill hue, UV and red chroma were consistent throughout the breeding season. Similarly, individual
differences in eye ring pigmentation and bill hue and red chroma remained consistent between consecutive years. These results
suggest that carotenoid based integumentary colorations act as dynamic traits that accurately reflect the carotenoid-status
of individuals, thus reliably indicating consistent differences in individual quality. Furthermore, variability in signal
expression appears to have a relevant genetic/phenotypic basis independently of environmental conditions.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
975.
Ecological implications of anti-pathogen effects of tropical fungal endophytes and mycorrhizae 总被引:5,自引:0,他引:5
We discuss studies of foliar endophytic fungi (FEF) and arbuscular mycorrhizal fungi (AMF) associated with Theobroma cacao in Panama. Direct, experimentally controlled comparisons of endophyte free (E-) and endophyte containing (E+) plant tissues in T. cacao show that foliar endophytes (FEF) that commonly occur in healthy host leaves enhance host defenses against foliar damage due to the pathogen (Phytophthora palmivora). Similarly, root inoculations with commonly occurring AMF also reduce foliar damage due to the same pathogen. These results suggest that endophytic fungi can play a potentially important mutualistic role by augmenting host defensive responses against pathogens. There are two broad classes of potential mechanisms by which endophytes could contribute to host protection: (1) inducing or increasing the expression of intrinsic host defense mechanisms and (2) providing additional sources of defense, extrinsic to those of the host (e.g., endophyte-based chemical antibiosis). The degree to which either of these mechanisms predominates holds distinct consequences for the evolutionary ecology of host-endophyte-pathogen relationships. More generally, the growing recognition that plants are composed of a mosaic of plant and fungal tissues holds a series of implications for the study of plant defense, physiology, and genetics. 相似文献
976.
Here we analyze herbarium records, surveys, and studies of fungal plant pathogens in tropical natural systems in order to establish a framework to study plant-pathogen interactions from a life-history perspective. We looked at how life-history traits of pathogens and their host plants affect the distribution of pathogens in different tropical habitats, and the importance of host phylogeny in determining the habitat associations of obligate fungal pathogens. Our study reveals that plant-pathogen interactions are prevalent and widespread in the tropics. Phylogenetic analysis of the distribution of obligate pathogens among plant families did not suggest a strong overall pattern of higher-level host phylogeny in pathogen host range, except that smut pathogens are particularly dominant on Poaceae and Asteraceae, and rusts are most common on Fabaceae, families that dominate disturbed areas in the tropics. 相似文献
977.
Allochthonous subsidy of periodical cicadas affects the dynamics and stability of pond communities 总被引:2,自引:0,他引:2
Periodical cicadas emerge from below ground every 13 or 17 years in North American forests, with individual broods representing the synchronous movement of trillions of individuals across geographic regions. Due to predator satiation, most individuals escape predation, die, and become deposited as detritus. Some of this emergent biomass falls into woodland aquatic habitats (small streams and woodland ponds) and serves as a high-quality allochthonous detritus pulse in early summer. We present results of a two-part study in which we (1) quantified deposition of Brood X periodical cicada detritus into woodland ponds and low-order streams in southwestern Ohio, and (2) conducted an outdoor mesocosm experiment in which we examined the effects of deposition of different amounts of cicada detritus on food webs characteristic of forest ponds. In the mesocosm experiment, we manipulated the amount of cicada detritus input to examine if food web dynamics and stability varied with the magnitude of this allochthonous resource subsidy, as predicted by numerous theoretical models. Deposition data indicate that, during years of periodical cicada emergence, cicada carcasses can represent a sizable pulse of allochthonous detritus to forest aquatic ecosystems. In the mesocosm experiment, cicada carcass deposition rapidly affected food webs, leading to substantial increases in nutrients and organism biomass, with the magnitude of increase dependent upon the amount of cicada detritus. Deposition of cicada detritus impacted the stability of organism functional groups and populations by affecting the temporal variability and biomass minima. However, contrary to theory, stability measures were not consistently related to the size of the allochthonous pulse (i.e., the amount of cicada detritus). Our study underscores the need for theory to further explore consequences of pulsed allochthonous subsidies for food web stability. 相似文献
978.
Pre-spawning reproductive biology and population structure of the sea cucumber Isostichopus fuscus were analysed at the Caamaño Island, Galápagos Islands, Ecuador on a monthly basis between January 1995 and June 1996. An average of 25 individuals of all sizes were collected each month. Using microscopic characteristics of the gonads three gonadal stages were described: (1) immature; (2) mature, and (3) spent. Mature individuals showed statistically different morphometric characteristics. I. fuscus was continuously sexually mature throughout the year independent of changes in sea water temperature. Mean oocyte diameter indicated planktotrophic larval development. Mean fecundity for this species was 567,884 (±95,528 SE) eggs per gonad. Size at first maturity was between 161.0 and 170.9 g drained weight and the smallest individual found with mature gonads had a drained weight between 121.0 and 130.9 g. The population sampled ranged between 13 and 31 cm (81.0–400.0 g) with less than 10% of the population of individuals ≥25 cm (≥300.0 g). No juveniles were recorded. 相似文献
979.
980.