共查询到20条相似文献，搜索用时 15 毫秒
1.
为了解烟台多棘海盘车种群个体大小分布及繁殖特征，自2010年5月至12月及2015年3月到5月，在烟台近海对该种群分别进行逐月采样调查。利用性腺指数(GI)和幽门盲囊指数(PCI)以及解剖组织学方法预测其产卵周期。结果表明：在所有的采样月份中，体长大于143mm的个体与体长小于42mm的个体在种群中均同时存在；在5-8月期间，种群结构特征以体长小于55mm的个体为主。同时该海域不同站点的采样月份中均有小个体存在，说明种群的产卵周期存在延后现象或者由于食物短缺造成了海星生长缓慢。腕长可以很好的用来衡量还行身体湿重。性腺在2010年5月-9月发育相对缓慢但在十月份迅速到达峰值20.95，之后明显下降，表明其产卵期从10月份持续至11月份。2015年3月-5月也发现了同样的现象，表明该种群自3月-5月存在另一个产卵期，且通过对卵的组织学分析也进一步证实该产卵期的存在。性腺指数和幽门盲囊指数呈负相关关系。由于食物来源短缺，烟台近海海星种群的繁殖特征极有可能受到当地近海扇贝养殖的影响。 相似文献
2.
To obtain baseline information on the size distribution of individuals in the population and reproductive features of sea star Asterias amurensis, monthly surveys of the population were carried out from May to December 2010 and March to May 2015 in coastal waters off Yantai, China. Spawning period was predicted by gonad and pyloric caeca indices as well as anatomical and histological methods. In the A. amurensis population, both large individuals(143 mm) and small ones(42 mm) were present in all sampling months. The population size structure was driven by the appearance of big cohorts of individuals less than 55 mm from May to August. The appearance of small individuals in all months suggested a prolonged spawning period at other sites in this bay or sea stars growing slowly because of food shortage. An arm length is a good predictor to wet body weight for A.amurensis. The development of gonad was relative slow from May to September but rapidly reached a peak of20.95 in October 2010, and then dropped remarkably, indicating its spawning lasted from October to November.The same phenomenon was found from March to May 2015, suggesting another spawning during March to May,which was also verified by the results of histologic analysis on ovary. The gonad index(GI) and pyloric caeca index(PCI) tended to show a negative relationship. Due to the poor food availability, the reproductive characteristics of sea star were most likely affected by the shellfish mariculturein Yantai coastal waters. 相似文献
3.
Pablo E. Meretta Nahuel E. Farias Maximiliano Cledón Carlos Renato Rezende Ventura 《Marine Ecology》2016,37(6):1423-1433
The sea star Asterina stellifera has declined during the last decade and is currently abundant only in the southern limit of its former range. We surveyed this population over 5 years to model individual growth and explore the relationship of changes in local abundance with variation in environmental factors and the reproductive status of individuals. Our results show that A. stellifera is a species with slow growth and a relatively long lifespan. Contrary to expectations for temperate species, growth rates were fairly constant through the year and therefore models including seasonal oscillations were inappropriate. The abundance of this species increased significantly from early spring to early summer, likely due to augmented activity and small‐scale aggregation during the reproductive season that affected our estimates of abundance. No significant recruitment occurred during the 5 years studied. The lack of recruitment during long periods and the slow individual growth rates make A. stellifera particularly vulnerable to local extinction. This study was performed prior to the arrival in the study area of the invasive kelp Undaria pinnatifida and side‐gilled sea slug Pleurobranchaea maculata, species that threaten the community structure where A. stellifera lives. Therefore, the information reported here will be essential to assessing the impacts of these exotic species on this sea star population. 相似文献
4.
Hyun-Sung Yang Do-Hyung Kang Heung-Sik Park Kwang-Sik Choi 《Ocean Science Journal》2017,52(4):519-526
Widely distributed from the northern coast of Vietnam to the northern Japan, the limpet Cellana grata (Gould, 1859) occurs commonly on the south and east coasts of Korea. Despite their wide distribution range, few studies have investigated the annual gametogenesis and reproductive effort of C. grata. In an attempt to understand the reproductive physiology of the limpet, we investigated the annual gametogenesis and reproductive effort of C. grata from Ulleungdo Island off the east coast of Korea. Histology revealed that the gonial mitosis commenced in January, as the female exhibited small oogonia (10–40 μm) in the follicle. From March to June, the oocyte size increased dramatically, and fully mature eggs (110–170 μm in diameter) appeared in early summer. First spawning males and females were observed in July, as the surface seawater temperature (SST) reached 22.1°C. The spawning male and females could be observed until the end of December. Gonad somatic index (GSI), a ratio of gonad mass to the total tissue weight, of the male ranged from 0.6 (April) to 17.9 (July), while the female GSI varied from 1.0 (February) to 18.3 (July). GSI of male and female declined rapidly from July to August, suggesting that the major purse of the spawning at the study site was between July and August. Our study suggested that the commercial catch of C. grata during July and August must be suspended at Ulleungdo Island, in order to protect the spawning limpets, which enhances C. grata recruitment and the population. 相似文献
5.
Barbara Niehoff 《Progress in Oceanography》2007,74(1):1-47
The present review addresses the reproductive strategies of marine calanoid copepods, as affected by their physiological preconditioning, and aims to enhance understanding of their adaptations to specific environmental conditions.Knowledge about oocyte development and internal gonad structure, especially in relation to feeding conditions, is essential for a complete understanding of the reproductive strategies of the copepods. Therefore, the foci of the review are to identify general patterns in oocyte and gonad development in calanoid copepod species from marine ecosystems worldwide and to elucidate the significance of gonad structures for reproductive strategies.Oogenesis is similar in all copepod species. During maturation, the morphology of the oocytes changes distinctly and, according to oocyte size and appearance of ooplasm and nucleus, five oocyte developmental stages are distinguished. In contrast, the gonad structure and its changes during the spawning cycle differ considerably among species, and these differences are related to specific reproductive traits.Four gonad morphology types can be distinguished: the Calanus-type, found in species from all over the world with distinctly different life history traits, is apparently most common in calanoid copepods. In this gonad type, most oocyte developmental stages are present simultaneously, and usually many oocytes mature synchronously, all of which are released in one clutch. The gonad structure allows frequent spawning and large clutches, hence, high egg production rates. This may be a preconditioning for exploiting seasonally high food supply. However, the Calanus-type was also found in species producing eggs at lower rates. In the diverticula of Pseudocalanus-type gonads, only two oocyte developmental stages are present and usually fewer oocytes mature synchronously. Accordingly, the egg production rate is generally lower as compared to the Calanus-type, and apparently only this gonad-type is structurally suitable for ovigerity. Species with Pseudocalanus-type gonads are present from polar seas to the tropics, some of them being key species. The Acartia-type was scarce, found in only one species, Acartia clausi. Here all oocyte developmental stages are present, including intermediate stages, but only a few oocytes mature synchronously and are released together. High spawning frequency compensates for the small clutches, and hence egg production rate may be as high as in Calanus-type gonads. In the Aetidius-type gonad, the total number of oocytes in the diverticula is low as is the number of oocytes maturing synchronously. Less is known about the reproductive biology of species with Aetidius-type gonads; however, their distribution and feeding patterns suggest that this type is common in species inhabiting environments of low food availability.The differences in gonad structures also lead to differences in the egg size:female size ratio, as the space available for each mature oocyte depends on the total number of oocytes. Independent from gonad-type, the eggs are relatively large in species in which the gonads contain only few oocytes, whereas small eggs are produced by species with gonads filled with many oocytes. Since all species carrying their eggs in external sacs until hatching (ovigerous species) have Pseudocalanus-type gonads, the scatter in their egg size:female size ratio is low. The broadcast spawning species are of all gonad-types, and consequently the scatter among them is high.A major factor affecting the timing and magnitude of spawning of calanoid copepods is the energy supply for gonad development. Therefore, part of the review elucidates the role of internal and external resources in fuelling egg production. In many species, freshly assimilated food is transferred into egg material within a short period of time, and clutch size and spawning frequency are the two parameters that allow adjustment of egg production to food availability and temperature. However, internal body reserves may also fuel oocyte development. The extent to which oogenesis depends on ambient feeding conditions varies considerably among species and even within species, apparently reflecting their adaptation to specific environmental conditions. All copepod species continue to release eggs for a short period after the onset of starvation, indicating that a short-term nutrient pool fuels final oocyte maturation. Some species, especially from polar and subpolar regions, are capable of reproducing on internal reserves, either solely or in addition to freshly ingested food, hence, decoupling the reproduction to some extent from the spring bloom. The reproductive strategy of Calanus finmarchicus, which responds with extreme flexibility to variations in food supply, is presented here as an example for the complexity of the reproductive processes in a calanoid copepod.In accordance with their physiological pre-conditioning, the calanoid copepod species exhibit distinctly different reproductive patterns. Polar and sub-polar environments are characterized by strong seasonality in light regime, and hence, phytoplankton concentration. The reproductive activity of many dominant (herbivorous) species peaks during the spring bloom. However, species that utilize internal reserves or food resources other than phytoplankton, reproduce before and after the bloom, or even year-round. In the North Atlantic, presented here as an example for a boreal marine ecosystem, maximum reproduction of the dominant copepod species Calanus finmarchicus occurs during the spring bloom. However, the timing of peak spawning varies between areas, as the onset of the bloom varies with hydrography and climate. The subtropical Gulf of Aqaba, in contrast to other subtropical systems, is characterized by seasonal phytoplankton succession driven by thermal winter convection. These changing environmental conditions, however, did not affect the reproduction of two of the dominant species, Clausocalanus farrani and C. furcatus. In contrast, other calanoid species exhibit reproductive cycles, either related to temperature (Ctenocalanus vanus) or to ontogenetic migration (Rhincalanus nasutus).The information gained from studies of morphology and reproductive traits contributes to standardization of methods in reproductive studies. Based on detailed knowledge of gonad morphology and its changes during maturation and due to food supply, classification schemata have been developed allowing the identification of females ready to spawn. In a next step, egg production may be estimated from preserved females by assessing clutch size through the number of maturing oocytes in the gonads. This approach, however, is as yet applicable only to the species best studied, Calanus finmarchicus.The present review shows that morphological studies on gonad maturation processes may provide significant contributions to fundamental ecological questions. Thus, they extend our knowledge of reproductive ecology from simply relating reproductive traits to abiotic and biotic factors toward a mechanistic understanding of how reproduction is regulated in calanoid copepods. 相似文献
6.
S. Buchanan 《新西兰海洋与淡水研究杂志》2013,47(5):859-870
The annual reproductive cycle of Perna canaliculus (Gmelin) was investigated for 1 year by collecting monthly gonad samples from an intertidal population. Gonads of 50 animals were dissected and photographically recorded on video before being fixed for histological sectioning. The histological gonad sections were examined both qualitatively, using a classification and scoring system (S) and quantitatively, using image analysis technology. The quantitative measures used were the proportion of: (1) sections comprising follicles (FC); (2) sections comprising gametes (GC); and (3) the proportion of follicles comprising gametes (G/F). Significant consecutive monthly changes in the qualitative and quantitative measures indicated major spawning events. Gametogenesis occurred during winter with a spawning in August‐September. Gonad condition remained low during the spring and early summer until a development period between January and March. A second major spawning event occurred between March and April. There was a high degree of synchrony in reproductive status observed between the sexes. When comparing the four measurement methods using the f statistic as an index of power the GC measure was found to be the most reliable. A gonad visual grading system was developed for rapid assessment of gonad reproductive status and tested. Visual grades of pre‐recorded gonad samples were compared to the histological measures. Increasing visual grade correlated strongly with increases in all of the histological measurements. The visual grading was a good predictor of the spawning activity of female P. canaliculus. 相似文献
7.
Understanding variability in reproductive schedules is essential to the management of recruitment limited fisheries such as that of Pecten maximus. Small scale (<5 km) variation in gonad condition and the onset of spawning of P. maximus were found among commercial scallop grounds in Isle of Man waters. Environmental and fishing drivers of these spatial patterns were investigated using a generalised additive model. Rate of change in temperature over the month prior to sampling was identified as the short term driver of gonad weight associated with the autumn spawning event. Long term drivers were average annual chlorophyll a concentration, scallop density, stratification index and shell size. The model explained 42.8% of deviance in gonad weight. Within site variation in gonad condition was high, indicating a “bet hedging” reproductive strategy which may decrease the chance of fertilisation especially at low densities. Therefore, areas protected from fishing, where scallop densities can increase may help buffer against reproductive failure. An increase in shell length from 100 mm to 110 mm equated to an increase of approximately 20% in gonad weight. Protecting scallops from fishing mortality until 110 mm (age four) compared to 100 mm (age three) may lead to an overall increase in lifetime reproductive output by a factor of 3.4. 相似文献
8.
Spatio-temporal variation of feeding intensity and diet in the red shrimp Aristeus antennatus was studied at two locations around the island of Mallorca (Balearic Islands, Western Mediterraean) in August, September, and November 2003, and in February, April and June 2004 at depths between 550 and 750 m. The two areas, with different oceanographic conditions, were respectively located in the northwest (Sóller) and the south (Cabrera) of Mallorca. Off Sóller, feeding intensity of A. antennatus showed a significant increase from February to April and June 2004 in all the three size-classes studied (small shrimps: CL < 30 mm; medium: CL between 30 and 40 mm; large: CL ? 40 mm). Off Cabrera, the highest fullness was recorded in November 2003 among small and medium shrimp, while only large specimens showed patterns similar to that found off Sóller. Off Sóller, the diet of both small (CL < 34 mm) and large (CL ? 34 mm) A. antennatus was mainly influenced by season, with three dietary groups corresponding to August-September 2003, to November 2003/February 2004, and to hauls from April to June 2004. Off Cabrera, hauls (representing diets) were grouped by depth, never by season. The most remarkable seasonal shift in the diet of A. antennatus off Sóller was the increase of mesopelagic prey in April-June relative to other months. In all size categories there was an increase off Sóller in the energy intake of prey ingested from February to June 2004, an increase not found off Cabrera. Degree of digestion of mesopelagic prey indicated nocturnal feeding on mesopelagic fauna. These prey probably have a shallower depth distribution at night than found in our daylight sampling, and possible migratory movements among prey and A. antennatus at night would explain the lack of correlation between prey abundance in guts and in the environment found during daylight periods for most micronekton mesopelagic prey (euphausiids, myctophids and sergestids). Off Sóller, fullness and diet were significantly linked to temporal changes in water column productivity (e.g., Chl a readings, fluorescence) and to changes in the shrimp biology (lipid content of hepatopancreas, Gonado-somatic Index, GSI). Off Cabrera, we found a higher dependence of fullness and diet with T and S, both variables in turn related to depth. The increase of stomach fullness and dietary energy intake in pre-reproductive females from February to April-June 2004 found off Sóller, coupled with the consumption of mesopelagic prey, was parallel to a significant increase of the gonad weight (GSI, fecundity) in June. Most individuals attain gonad development in the period May-June, after two months of the peak of primary production at the surface. The strong link found between pelagic resources and reproductive processes in a deep-sea species such as the shrimp Aristeus antennatus, situated near the top of the trophic web, suggests a rapid energy flow via mesopelagic fauna between surface primary production and bathyal megabenthic communities at oligotrophic insular areas. In contrast to mainland areas off the Catalan coasts submitted to the influence of submarine canyons, around the island of Mallorca the empoverishment of benthos biomass may enhance consumption of micronektonic prey and a possible accumulation of pre-reproductive females of A. antennatus in areas (e.g., steep slopes and persistent frontal systems found off Sóller) with high zooplankton aggregations. 相似文献
9.
许氏平鲉消化道的组织化学研究 总被引：2，自引：2，他引：2
运用组化方法对许氏平消化道碱性磷酸酶、酸性磷酸酶、羧酸酯酶和粘液物质进行了定位及半定量研究。发现幽门盲囊和肠上皮细胞顶端胞质和纹状缘具碱性磷酸酶活性 ;胃粘膜上皮细胞核上方胞质、幽门盲囊及肠上皮细胞顶端胞质中检测到酸性磷酸酶活性 ;在胃贲门部和盲囊部、幽门盲囊以及肠的上皮细胞内还检测到羧酸酯酶活性。整个消化道的粘膜层中存在许多粘液细胞。食道上皮含大量酸性粘液细胞 ,胃上皮细胞均含有中性粘液 ,而肠道由前向后中性粘液物质逐渐减少 ,酸性粘液物质逐渐增多。研究结果表明许氏平食道和直肠有润滑和微弱的吸收作用 ,胃有消化脂类和吸收二糖及短链脂肪的功能 ;幽门盲囊有较强的吸收脂类的功能 ;前肠、中肠和后肠有活跃的细胞内消化和吸收功能 相似文献
10.
The sea cucumber Holothuria scabra is a widely distributed and economically important species that has been harvested in Kenya for decades. No previous studies have been carried out on the reproduction of this species in Kenya. Standard gonad index methods were used to analyze reproductive patterns of individuals collected monthly in 1998–1999, 2000–2001 and 2006–2007. Morphological characteristics, gonad tubule lengths and fecundity were also measured. Mean monthly gonad indices were significantly correlated between males and females indicating synchronous gonad development between the sexes. Gonad indices showed a biannual pattern that was consistent in all three years with a minor spawning event occurring between August and September and a major spawning event between November and December. The pattern of gonad growth showed significant variability between years and between months. Temporal changes in gonad growth correlated significantly with gonad tubule length and absolute fecundity. Monthly gonad indices also correlated significantly with monthly measurements of air temperature and light suggesting a possible role for both factors in timing gametogenesis and spawning. There was a shift in sex ratio from unity in the 1998–1999 and 2000–2001 samples to significantly more males in the 2006–2007 samples, as well as a significant reduction in mean sizes (body wall weight) and reproductive output (gonad index) which suggests that the reproductive success of this species is potentially negatively affected by fishing. 相似文献
11.
The reproductive cycle of the abundant intertidal limpet Cellana ornata (Dillwyn 1817) was examined over 19 months, covering two breeding periods, on a rocky intertidal platform in southern New Zealand. A gonad index was calculated, and histological sections were used to count the numbers of mature and immature eggs present. Fecundity was estimated using counts of eggs before and after spawning. To determine any variation between sites, the gonad index of limpets at a second site dominated by boulders was examined over 6 months during the second breeding period. C. ornata had a single spawning period annually during summer, with greatest gonad sizes in January‐February. There were significant differences in peak gonad indices between two breeding seasons on the platform. Within the second breeding period, both the timing and magnitude of peak gonad development differed between sites, with lower reproductive output at the boulder site. Fecundity increased with increasing size, but individuals are probably capable of reproducing after their first year on the shore. The life history of this species is discussed in comparison to other limpets in New Zealand. 相似文献
12.
福建省厦门海沧沿岸滩涂的缢蛏Sinonovacula constricta 的主要生殖期是10月,其两次高峰分别出现10月的上、下旬。缢蛏的性腺和消化腺发育过程中蛋白质、脂类、糖类与17种氨基酸的组成以及它们的组织化学反应的结果表明,在生殖周期中性腺与消化腺的蛋白质和脂类的变化大,而糖类都维持在低水平上,其最高量不超过9%干重。性腺和消化腺的蛋白贮存量随着性腺发育而增加,于成熟配子排放之前蛋白质量达到最大。排放之后蛋白质量和脂量皆下降,而糖量在性腺中却略有增加。在8～9月,消化腺和性腺内的脂量变化呈相反关系,表明当性腺形成过程它们之间可能有转化作用。性腺、消化腺的组化反应结果与它们的生化成分的分析相一致。性腺与消化腺的生化组成的相互关系表明,与脊椎动物相类似,缢蛏消化腺也有储存营养物质的作用。 相似文献
13.
This study examines changes in egg production rates of two co-occurring Pseudocalanus species, P. acuspes and P. minutus, in response to changing temperatures (0, 3, 6, 9 and 12°C) in the White Sea. The boreal P. acuspes (sample size >650 individuals) increased its reproductive rate gradually across the entire range of temperatures from 0 to 12°C. Significant differences in egg production rates and reaction to temperature were also observed between P. acuspes females incubated during the early vs. the mid-summer season. The sample size of the Arctic P. minutus was significantly smaller due to the low numbers at which this species occurred. However, the results suggest that this species increases its egg production rates from 0 to 3°C from 3.3 to 8.5% dry weight female–1 day–1, but at 9° its reproductive rate drops significantly and the animals demonstrate markedly reduced fitness. Our results indicate that closely related co-occurring species, and even different generations within one species, can demonstrate significantly different responses to changes in the physical environment. 相似文献
14.
The impact of overfishing and El Niño on the condition factor and reproductive success of Peruvian hake, Merluccius gayi peruanus 总被引：1，自引：1，他引：0
Michael Balln Claudia Wosnitza-Mendo Renato Guevara-Carrasco Arnaud Bertrand 《Progress in Oceanography》2008,79(2-4):300
In this study we examine physiological responses of Peruvian hake (Merluccius gayi peruanus) to changes in their population structure and physical environment during the period 1971–2004. In particular, we assess the relative investment of energy in growth and/or reproduction of small (20–35 cm) and large (35–50 cm) hake. We calculated the (i) condition (Fulton’s K), (ii) gonad and (iii) gut fullness indices for 42,761 female hakes sampled from commercial landings; these indices indicate fish somatic, reproductive and feeding condition, respectively. Using Generalized Additive Models we then examined potential relationships between these indices and sea surface temperature anomalies and date. Drastic energy exhaustion and a decrease in female hake fecundity were observed during El Niño events. The long-term trend showed a general increase in condition factor and a decrease in gonad index for large hake between 1971 and 2004. Small hake exhibited a different trend with an increase in reproductive activity, which was accompanied by an earlier maturation. We hypothesise that the observed low investment of energy in reproduction by large female hake might be related to the lack of large males, due to a sex-selective fishery and the impact of El Niño. We suggest that fishing diminished hake reproductive capacity, modified the sex ratio in favour of females and increased population vulnerability to environmental stress, in particular to the El Niño. The impact of multidecadal variability and predators like the squid, Dosidicus gigas, remain unresolved until longer time series become available. 相似文献
15.
The Senegal sole, Solea senegalensis, is a flatfish species distributed from the Bay of Biscay to the coast of South Africa. Although it is a species of high commercial value its spawning period remains poorly known. In the Tagus estuary, Portugal, two juvenile cohorts of this species colonize two independent nursery areas within the estuarine system. Left lapilli otoliths of these 0-group juveniles were used to estimate age and back-calculate hatch dates, thus allowing the estimation of S. senegalensis spawning period in the Portuguese coast. The two cohorts of S. senegalensis completed the colonization of the two nurseries in July. The ages of juveniles were estimated to range between 46 and 111 days in nursery A, and between 33 and 61 days in nursery B. Hatch dates ranged from April to early June for juveniles colonizing nursery A, and from May to early June for juveniles colonizing nursery B. The mean hatch date in nursery A was the 7th of May, while in nursery B it was the 25th of May. It was concluded that the spawning period for this species off the Portuguese coast was from April to June. 相似文献
16.
Hans-Jürgen Hirche Ksenia Kosobokova 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2729
The distribution of Calanus finmarchicus was studied on a transect across the central Greenland Sea, and on five transects from the Eurasian shelves across the Atlantic Inflow in the Arctic Ocean. Stage composition was used as an indicator for successful growth; gonad maturity and egg production were taken as indicators for reproductive activity. On the Arctic Ocean transects, these parameters were measured simultaneously from the sibling species Calanus glacialis. Response of egg production rate to different temperatures at optimal food conditions was very similar between both species in the laboratory. C. finmarchicus was present at all stations studied, but young developmental stages were only present close to the regions of submergence of Atlantic water under the Polar water. This together with a decreasing abundance and biomass from west to east along the Atlantic Inflow in the Arctic Ocean and reproductive failure indicates that C. finmarchicus is expatriated in the Arctic Ocean. We hypothesize that the late availability of food in the Arctic Ocean, rather than low temperature per se, limits reproductive success. Better reproductive success in the very low temperature regions of the Return Atlantic Current and the marginal ice zone in the Greenland Sea supports this hypothesis. The possibility for a replacement of C. glacialis by C. finmarchicus and consequences for the ecosystem after increasing warming of the Arctic are discussed. 相似文献
17.
本文根据1987.12～1989.4对舟山朱家尖岛南沙沙滩逐月采集标本进行研究。结果表明,等边浅蛤Gomphina veneriformis的性腺发育可分为5期:增殖期、生长期、成熟期、排放期和休止期。在舟山海区,等边浅蛤一年中为一个繁殖周期,繁殖期为8月下旬至9月中旬。有雄性早熟现象。 相似文献
18.
Despite the large body of work published in the last two decades on the reproduction of the sea urchin Paracentrotus lividus, the reproductive aspects linked to hydrodynamic conditions and their influence on gonad production remain poorly understood. The present paper aims to evaluate the effect of hydrodynamism on the reproductive cycle of P. lividus. Variability in the gonadosomatic index (GSI) of P. lividus was estimated seasonally from 2007 to 2008 at two shallow sub-littoral flat basaltic areas at Ustica Island (Western Mediterranean). GSI was higher in the sites characterized by low hydrodynamism than in those with high hydrodynamism. Results also suggest a possible role for hydrodynamism in triggering processes of resource limitation (food shortage), probably by interfering with P. lividus feeding activity. 相似文献
19.
Joana F.M.F. Cardoso Johannes IJ. Witte Henk W. van der Veer 《Estuarine, Coastal and Shelf Science》2009
Cerastoderma edule and Mya arenaria are two common bivalve species in European waters. Longevity and maximum size are much greater in the latter species. Because comparison of species life-history strategies states that a long life span (i.e. high annual survival) generally goes with lower fecundity, we hypothesise that reproductive output would be lower in M. arenaria than in C. edule. In the present paper, we studied the reproductive strategies of these two species in an intertidal and a subtidal area of the western Dutch Wadden Sea, by following seasonal changes in absolute and relative weights of somatic and gonadal tissues in these bivalves. Starting of spawning was similar in the two species, around May, except for intertidal M. arenaria, which initiated spawning in August. Individual energy investment in reproduction was similar for the two species but, unlike M. arenaria, C. edule spawned completely, releasing all energy of gonadal mass in the form of gametes. Mya arenaria used the gonad not only for reproduction but also for storage. In the intertidal area, we found a trade-off between longevity and reproduction, i.e. maximum reproductive output (expressed as a proportion of body mass) was higher in C. edule than in M. arenaria. However, since body size is larger and life span longer in M. arenaria than in C. edule, mean lifetime reproductive output per individual must be higher in the first than in the latter. Based on the differences in reproductive strategies of these two species, we hypothesise that the negative effects of warming climate on bivalve population dynamics in the Wadden Sea will be stronger in C. edule than in M. arenaria. 相似文献
20.
Reproductive cycles of the Pacific oyster Crassostrea gigas (Thunberg) from the Marlborough Sounds, New Zealand, were followed between June 1998 and January 2000. Histological examination of the gonad confirms an annual cycle with a winter inactive period followed by rapid gonad development and a single short spawning period. The population gonad index correlated with seawater temperature and changes in tissue dry weight, condition index, and biochemical components. In winter, few individuals with early gametogenic stages were present and rapid development of primary oocytes (diam. 11 μm) occurred during spring (September‐November). The developmental rate and the diameter of mature oocytes (37 μm) was similar for the 1998 and 1999 seasons. For a standard 110‐mm‐length oyster, maximal tissue body weight and condition index were recorded in December. Rapid weight loss in January was length dependent and was attributed to spawning. Temperature was the environmental variable which best correlated with the timing of gametogenesis. Food availability (phytoplankton biomass) may have been responsible for inter‐annual variations. The biochemical composition (% glycogen, lipid, protein) of separated gonad and somatic tissues were variable seasonally and annually. Gametogenesis (oocyte diameter) was associated with increased gonad protein and glycogen and a decrease in lipid concentrations. These changes are similar to those in Pacific oyster populations from other parts of the world. 相似文献