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11.
Hazel Matias-Peralta Fatimah Md. Yusoff Mohamed Shariff Aziz Arshad 《Marine pollution bulletin》2005,51(8-12):722
The effects of salinity, temperature, and light conditions on the reproduction and development of harpacticoid copepod, Nitocra affinis f. californica under controlled laboratory conditions were determined. Seven different salinity levels (5, 10, 15, 20, 25, 30, 35 ppt), four temperatures (20, 25, 30, 35 °C), three different light intensities (25, 56, 130 μmol m−2 s−1) and photoperiods (24 h:0 h, 1 h:23 h, 12 h:12 h LD cycle) were employed in this study. The highest (p < 0.05) overall reproduction and fastest development time were achieved by copepods reared under 30–35 ppt salinity. The optimum temperature required for the maximum reproduction was 30 °C while under 30 °C and 35 °C the copepod development time was shortest (p < 0.05) compared to other temperature levels. The overall reproduction was highest (p < 0.05) and development rate of N. affinis was shortest (p < 0.05) under lowest light intensity (25 μmol m−2 s−1). Continuous light (24 h:0 h LD) inhibited the egg production while, continuous darkness (1 h:23 h LD) and 12 h:12 h LD significantly favoured the overall reproductive activity of the female. Photoperiods 1 h:23 h and 12 h:12 h LD yielded highest total (p < 0.05) offspring female−1 coupled with highest (p < 0.05) survival percentage. This study illustrated that although N. affinis can tolerate wide range of environmental conditions, prolonged exposure to subnormal environments affect its reproduction and development. This study showed that this species can be mass cultured for commercial purposes and has a potential to be used for toxicity studies due to its high reproductive performance fast development and a wide range of tolerance to environmental conditions. 相似文献
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Size distributions of Neocalanus cristatus, N. flemingeri and N. plumchrus were investigated in the eastern and the western subarctic gyres and three marginal seas of the North Pacific during the diapause period to examine the geographical variation in body size of Neocalanus species and to clarify the origin of the large biennial N. flemingeri which has been observed in the Oyashio region. There were significant among region variations in body sizes for all three species of Neocalanus. Generally, the body sizes of the copepods were larger in the marginal seas and marginal areas of the open ocean. In the open ocean, the body sizes increased westward. These patterns of variation in the body sizes roughly correlated with local food availability. Distribution of biennial N. flemingeri was restricted to the Sea of Japan, the Okhotsk Sea and the Oyashio region. The large-sized biennial N. flemingeri were abundantly observed in the Okhotsk Sea, and the medium-sized biennial individuals were observed in the Sea of Japan. These facts strongly suggest that the large biennial N. flemingeri in the Oyashio region are advected from the Okhotsk Sea. 相似文献
14.
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
15.
Toru Kobari Kazuaki Tadokoro Akihiro Shiomoto Shinji Hashimoto 《Journal of Oceanography》2003,59(1):3-10
Geographical variations in prosome length and body weight of Neocalanus copepods (N. cristatus, N. plumchrus and N. flemingeri) were investigated on samples from North-South and East-West transects in the North Pacific during spring to early summer
in 1998 and 1999. Southward and eastward increasing patterns were pronounced for water temperature, although no significant
pattern was observed for chlorophyll a concentrations. All Neocalanus species showed large geographical variations in prosome length and body weight, being smaller in the southern and eastern
waters. Comparing the relationship between prosome length and body weight, large deviations (lower body weight at a given
prosome length) were evident for the eastern specimens of N. cristatus and N. plumchrus. In stepwise regression analysis, the geographical variations of prosome length and body weight revealed a significantly
negative correlation with temperature variations. These results suggest that temperature is a more important environmental
factor than chlorophyll a concentration in its effect on geographical variations in prosome length and body weight of Neocalanus copepods in the North Pacific.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Migration to deep water during diapause may contribute to the retention of several dominant oceanic calanoid copepod populations in eastern boundary current systems, where the mean flow of poleward undercurrents is in opposition to mean equatorward surface flow. The vertical distributions of Calanus pacificus late copepodid stages were measured at a 1200-m deep, open-ocean station in the Southern California Bight on 13 dates between April 2000 and March 2001 using a MOCNESS (multiple opening and closing net and environmental sensing system). Copepod vertical distribution was compared to the vertical position of the California Undercurrent. Diapausing C. pacificus were primarily found between 300 and 400 m at the beginning of the diapause season, in June and July, and between 250 and 350 at the end of the diapause season, in November and January. Depth distributions were broader from August to October, ranging from about 350 m to the maximum depth sampled, 1100 m, and the median depth of diapausing C. pacificus was deeper, up to 800-900 m, during this period. Maximal depths of diapausing C. pacificus, 1100-1000 m, were greater than have previously been reported. The mean depth of the California Undercurrent was 250 m, and its approximate depth range was 110-430 m. Diapausing C. pacificus CV were abundant in the California Undercurrent at the beginning and end of the diapause season, in June to July and late-November to January, suggesting that poleward transport of diapausing copepods in the California Undercurrent contributes to C. pacificus population retention in the California Current System. 相似文献
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胶州湾浮游桡足类18S核糖体RNA基因(18S rDNA)扩增及序列变异初步研究 总被引：3，自引：0，他引：3
采用PCR扩增、文库构建、限制性片段长度多态性分析、序列分析和系统学分析等方法，初步研究了夏季胶州湾上层海水浮游桡足类核糖体小亚基RNA基因(18S rDNA)约1．5kb片段的序列变异。从浮游生物混合DNA中选择性扩增桡足类18S rDNA，建立桡足类18S rDNA变异类型文库，并从文库中随机挑选的30个克隆进行分析。结果表明，Vsp Ⅰ限制性内切酶能将这些克隆分成频率分别为0．17、0．23和0．6的3种操作分类单元(OTUs)，遗传多样性指数达到0．95。3条OTU代表克隆序列与甲壳纲桡足亚纲核苷酸差异数在75．4—97．8之间，而与其他亚纲的差异都高于100。3条OTU代表克隆序列均属于桡足亚纲，其中，AY437861和AY437862属于哲水蚤目。3条OTU代表克隆序列可分为2个高变异区和3个相对保守区，其GC％分别为47．37％、48．16％和48．57％。研究结果表明，混合DNA提取方法简单，设计的引物可选择性地扩增浮游桡足类18S rDNA，根据18S rDNA序列序列变异描述浮游桡足类多样性是可行的。研究结果也为在浮游桡足类分类中引入18S rDNA序列奠定了基础。 相似文献
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J.Roy Robertson 《Estuarine, Coastal and Shelf Science》1983,16(1):27-36
Laboratory experiments were conducted to determine the feeding performances of Uca zoeae and the estuarine copepods Acartia tonsa and Tortanus setacaudatus when these zooplankton preyed upon the co-occurring tintinnids Favella panamensis (length 265 μm) and Tintinnopsis tubulosa (length 148 μm). Predation by Favella on Tintinnopsis was also studied. Over the range of experimental prey densities used, Acartia ingested Tintinopsis at rates linearly related to prey density. Favella was ingested by Aractia at higher rates than was Tintinnopsis. Tortamus ingested Favella more readily than did Acartia, but Tortanus did not ingest Tintinnopsis. Uca ingested both Tintinnopsis and Favella while Tintinnopsis was also ingested by the larger tintinnid Favella. Comparisons of Acartia predation on tintinnids with published data on ingestion of nauplii and phytoplankton showed that when the phytoplankton are dominated by small (diameters < 10 μm) species, tintinnids in concentrations exceeding 103 organisms 1?1 can be important items in the diets of Acartia. At lower tintinnid concentrations or when algal species with diameters > 10 μm are present in significant concentrations, tintinnids merely supplement algae in the diet of Acartia. Generally, tintinnids are more important food items for Acartia than are comparably sized nauplii. Only at concentrations exceeding 104 cop. m?3 can Acartia depress tintinid population growth. 相似文献
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Junbeom Park Soyoun Kim Jisu Yoo Jae-Seong Lee June-Woo Park Jinho Jung 《Marine pollution bulletin》2014
We investigated the effects of salinity (5‰, 15‰, 25‰ and 35‰) on metal ion (Cu and Zn) and nanoparticle (NP) CuO and ZnO toxicity to Tigriopus japonicus. Increasing the test media volume without renewal increased the 96-h LC50 for Cu (32.75 mg L−1) compared to the reported value (3.9 mg L−1). There was no significant difference in acute toxicity at different salinities between acclimated and unacclimated T. japonicus (p > 0.05). Increasing salinity decreased the dissolved concentrations of Cu and Zn ions due to the precipitation of the metal ions, consequently reducing the acute toxicity to T. japonicus. The effect of salinity on acute CuO and ZnO NP toxicity was similar to that on metal ion toxicity. Since the aggregation of NPs generally enhanced at higher salinities, both the dissolution and aggregation of CuO and ZnO NPs may control the effect of salinity on acute toxicity to T. japonicus. 相似文献