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1.
Consistent differences in the morphology of the last metasomal segment and genital segment were found among adult female Boeckella triarticulata, B. dilatata, and B. hamata. These differences are taxonomically useful in collections where males are sparse. Distinguishing features used to classify CIII‐CV B. triarticulata, B. dilatata, and B. hamata of co‐occurring populations to species are also described. The diagnostic features of both adult female and copepodites may be used at low magnifications.  相似文献   

2.
Life histories for the dominant, larger copepods of the subartic Pacific have been constructed by sampling from weatherships patrolling Ocean Station P (50°N, 145°W) during 1980 and 1981. Neocalanus plumchrus reproduced at depths below 250 m from July through February. Copepodite stages were present in surface layers from October through August with a large peak in numbers and biomass in spring. Fifth copepodites prepared for diapuse in 38 days during spring and descended to depths below 250 m. They commenced immediately to mature, and the females reproduced without renewed feeding. This schedule contrasts with that of the population in the Strait of Georgia, which remains in diapause from July to January and matures exclusively in January and February. There appears to be a difference between the coastal and oceanic habitats in preparing the diapausing individuals for maturation.Maturation of the diapausing stock of N. plumchrus maintained constant adult populations, averaging 714 males m?2 from June through October and 1,434 females m?2 from August through January. This constancy, together with the exponential pattern of decline in the diapause stock from September through February, suggests that density of adults may regulate maturation of fifth copepodites. Offspring of individuals delaying maturation and, thus, reproduction would benefit from the resulting moderation of intraspecific competition, probably that among copepodites.Reproduction of Neocalanus cristatus also occurred below 250 m, and, while spawning was continuous through the year, there was a substantial peak in November. That resulted in a peak of abundance for early copepodite stages in mid-winter, and a peak for the fifth copepodite stage in June. Stocking of the population of fifth copepodites in diapause below 250 m occurred from July through October. Some fifth copepodites were present in surface layers through the entire summer, and some younger copepodites persisted through the summer in progressively declining abundance just below the mixed layer. In autumn 1980 resurgence of early copepodite populations was rapid, occurring during the course of a prolonged October storm. The storm may have improved the habitat either by cooling the mixed layer or by resupplying nutrients to the euphotic zone.Eucalanus bungii reproduced in the mixed layer in early May and in early July. The first event was a spawning by females that had previously spawned in 1979 and then had returned to diapause. The second, heavier spawning (more females, more eggs per female) was by newly matured females from stocks that had overwintered as fifth copepodites. Nauplii peaked sharply in abundance on 19 July, one week after the peak in spawning. First and second copepodites peaked on 1 August, and all had advanced to the third copepodite stage by September. The diapause stock was established by September, principally between 250 and 500 m, and consisted of copepodite stages from third to sixth. Duration of the E. bungii life cycle appears to be typically two years. New nauplii develop as far as the third or fourth copepodite stage during their first summer, then enter diapause. The second summer they advance to the fifth copepodite stage and reenter diapause. Fifth copepodites mature in their third summer at two years of age. The males remain at depth and mate without subsequent feeding. Females migrate at night to the mixed layer where spawning occurs. About 20% of females that had already spawned in 1980 reentered diapause. They would reproduce again in their fourth summer at three years of age. All aspects of the life cycle suggest low mortality rates for copepodite stages, particularly at depth in the habitat occupied during diapuse. There can be no premium on rapid reproduction for E. bungii in the subartic Pacific, and there must even be benefit from spreading reproduction between years. This iteroparity may amount to a “bet-hedging” tactic, the young from a given mother having more than one chance to find sustaining conditions. It also produces gene flow between the year classes of the biennial life cycle.  相似文献   

3.
The spatial distribution of stage-specific abundance and reproduction of the copepod Paracalanus parvus were studied from October 2005 to September 2006 in the Jiaozhou Bay. This copepod occurred continuously in this bay throughout the year. The species reached the lowest abundance in April and peaked in June. From October to December, distribution center mainly occurred in offshore water and at the mouth of the bay. In winter, early copepodites and adults gradually decreased and till February, most of the population was only comprised of CIV–CV stages. Overwintering copepodites matured in March and males tended to mature before female. From May to September, each stage occurred in the population and gradually reached high abundance. Temperature and chlorophyll a (Chl-a) concentration in the three stations can't clearly explain the seasonal variation in stage-specific abundance, so we surmised the important effect of the Yellow Sea. Egg production rate (EPR) reached its lowest in winter and peaked in June at 60.8 eggs female−1 day−1 in nearshore water. In the warming period, EPR in nearshore water was statistically higher and EPR > 10 eggs female−1 day−1 lasted longer than that in offshore water, showing the importance of nearshore water for recruitment of P. parvus. Our study showed that EPR was positively related to temperature and total chlorophyll a in offshore water and mouth of the bay. In nearshore water, the relationships between EPR and temperature and Chl-a in three size fractions were not the same as those in offshore water, suggesting complicated ecosystem in such a eutrophic area in warming period.  相似文献   

4.
The southeastern Bering Sea shelf ecosystem is an important fishing ground for fin- and shellfish, and is the summer foraging grounds for many planktivorous seabirds and marine mammals. In 1997 and 1998, Northern Hemisphere climate anomalies affected the physical and biological environment of the southeastern Bering Sea shelf. The resulting anomalous conditions provided a valuable opportunity to examine how longer-term climate change might affect this productive ecosystem. We compared historical and recent zooplankton biomass and species composition data for the southeastern Bering Sea shelf to examine whether or not there was a response to the atmosphere–ocean–ice anomalies of 1997 and 1998. Summer zooplankton biomass (1954–1994) over the southeastern shelf did not exhibit a decline as previously reported for oceanic stations. In addition, zooplankton biomass in 1997 and 1998 was not appreciably different from other years in the time series. Spring concentrations of numerically abundant copepods (Acartia spp., Calanus marshallae, and Pseudocalanus spp.), however, were significantly higher during 1994–1998 than 1980–1981; spring concentrations of Metridia pacifica and Neocalanus spp. were not consistently different between the two time periods. Neocalanus spp. was the only taxon to have consistent differences in stage composition between the two time periods—CV copepodites were much more prevalent in May of the 1990s than early 1980s. Since relatively high zooplankton concentrations were observed prior to 1997, we do not attribute the high concentrations observed in the summers of 1997 and 1998 directly to the acute climate anomalies. With the present data it is not possible to distinguish between increased production (control from below) and decreased predation (control from above) to explain the recent increase in concentrations of the species examined.  相似文献   

5.
As part of a broader field study examining the potentially deleterious effects of diatoms on planktonic food webs, we examined the abundance, stage composition, diet, and feeding success of the chaetognath, Sagitta elegans, and the abundance and morphometric condition of larval Pacific hake, Merluccius productus. Our objective was to look for a relationship between spring phytoplankton blooms and planktonic predators, as mediated by their copepod prey, with special reference to possible deleterious effects of diatoms. Zooplankton were collected weekly during February–May and in mid-summer of 2002 and 2003 in Dabob Bay, Washington State, USA. S. elegans abundance was high in summer of both years and was higher in spring 2003 than spring 2002. Larval chaetognaths dominated the population in early spring and remained present throughout sampling. S. elegans consumed mostly copepods. The abundance of larval S. elegans was correlated with the abundance of copepodites, although no relationship between chaetognath feeding success and prey abundance was found. Larval Pacific hake abundance was high (1200 larvae per square meter) in late February and early March of 2002 and 2003 and decreased rapidly in late spring. The morphometric condition of M. productus was not significantly related to copepod abundance. These results indicate that any deleterious effects of diatoms on copepod abundance, at the scale seen during spring 2002 and 2003 in Dabob Bay, did not greatly affect the next higher trophic level.  相似文献   

6.
Resource partioning among the planktivorous stages of eight fish species occurring in a Mediterranean coastal lagoon was studied. Five species were migratory mullets that spawned in the sea (Liza ramada, L. aurata, L. saliens, Chelon labrosusandMugil cephalus), while the other three species were resident and spawned in the lagoon (Atherina boyeri, Cyprinus carpioandGambusia holbrooki).Mullet fry exhibited similar diets, based on the consumption of zooplanktonic Crustacea such as copepods and cladocerans, although adult chironomids were also important.Gambusia holbrookiandA. boyerifed on small prey such as copepod nauplii, copepodites and rotifers, whileC. carpioconsumed larger prey preferentially (cladocerans and copepods).According to the trophic overlap and niche width results, seven species pairs could be competing in the estuary, although further experimental evidence is still required.  相似文献   

7.
Surface distributions of zooplankton were surveyed with simultaneous measurements of temperature, salinity, chlorophyll and nitrate, around the Izu Islands in July 1988. Several phytoplankton patches, which had developed in the upwelled waters, were encountered around the islands. Zooplankters collected with a 20µm mesh mainly consisted of copepods including eggs, nauplii, copepodites and adults.Paracalanus parvus dominated among the copepod females. High concentrations of all copepod stages were associated with the phytoplankton patches. The increase in reproductive activity of female copepods was considered as a possible process to form the copepod patches associated with the phytoplankton patches.  相似文献   

8.
海带苗绿烂病暴发严重威胁海带养殖生产,给海带养殖业造成巨大经济损失.研究发现,海带中的多酚化合物可以抵御海带病害初期病原体侵入.为研究多酚对绿烂海带表面附生菌的抑菌效果,在病烂部位分离出一株细菌,通过16s rRNA基因测序的方法,证实该细菌为小孔芽孢杆菌(Bacillus foraminis).进一步以健康海带为原料...  相似文献   

9.
The impact of the scyphomedusa Aurelia sp. on planktonic assemblages was experimentally studied in enclosures incubated in situ in the sea lake of Mljet Island (Big Lake, Southern Adriatic), where jellyfish are present throughout the year. In situ feeding experiments using plankton at natural densities indicated a reduction in abundance for small calanoid and cyclopoid copepods, copepodites, nauplii and ciliates in the presence of Aurelia sp. In addition to direct predatory pressure, Aurelia sp. exerted an indirect cascading effect on autotrophic and heterotrophic microbial plankton. Phytoplankton biomass increases of up to 0.5 μg C·l?1·h?1 were mainly related to 19′‐hexanoyloxyfucoxanthin‐ and 19′‐butanoyloxyfucoxanthin‐containing phytoplankton. Bacterial production was about twice as high in the presence of Aurelia sp. and biomass was also consistently higher. It appears that the top‐down effect of predation along with material release by Aurelia sp. results in increases in microbial biomass and production.  相似文献   

10.
The distribution of five dominant calanoid copepods was related to different water masses in the Angola-Benguela Front system. Five water bodies were identified by principal component analysis, on the basis of abiotic parameter such as temperature, salinity, dissolved oxygen, phosphate, silicate, nitrate and nitrite. These parameters were reduced to single factors and arranged along two principal component axes. The copepod species incuded females and copepodites C5 of Calanoides carinatus and females of Metridia lucens, Centropages brachiatus, Nannocalanus minor and Aetideopsis carinata. The water bodies identified in the frontal system were related to currents, upwelling processes, an oxygen minimum layer and biological modification. The different copepod species, as well as the two ontogenetic stages of C. carinatus, showed clear preference for specific water bodies, and their behavioural and physiological adaptations to the environment are discussed.  相似文献   

11.
为研究两种经济红藻红毛菜(Bangia fucscopurpurea)和坛紫菜(Pyropia haitanensis)的光合作用和品质差异,选取一株野生型红毛菜CY和一株野生型坛紫菜NSD35作为实验材料,分别测定二者在相同培养条件下的关键光合参数和营养成分指标。结果显示：红毛菜的最大电子传递速率、净光合速率、藻红蛋白含量分别比坛紫菜高29.6%、96.8%、60.5%;必需矿质元素钾、钙、镁、铁、锌的含量分别比坛紫菜高59.5%、39.5%、34.1%、86.2%、68.4%;红毛菜的必需氨基酸和风味氨基酸含量都高于坛紫菜。此外,二者的呼吸速率、最大光量子产率、叶绿素a、总糖、总蛋白和碘含量没有显著差异。研究结果表明,与坛紫菜NSD35相比,红毛菜CY的光合速率更快,矿质元素积累能力更强,必需氨基酸和风味氨基酸含量更高。研究结果有助于了解红毛菜和坛紫菜的光合作用和品质特点,为开发红毛菜种质资源提供数据参考。  相似文献   

12.
Landlocked sockeye salmon (Oncorhynchus nerka), ranging in fork length (FL) from 105 to 313 mm, were captured in fine‐mesh gill nets set in the limnetic zone of the Waitaki hydro lakes (44° 30′ S, 170° 10’ E) in the South Island, New Zealand. A total of 443 stomachs was examined and the frequency of occurrence, volume and weight of prey items calculated. In the Ahuriri Arm of Lake Benmore the principal food (54% by weight) was zooplankton (Boeckella dilatata) whereas in the Haldon Arm of Lake Benmore it was larval and juvenile common bullies (Gobiomorphus cotidi‐anus) (73% by volume). In Lake Waitaki in winter, salmon had eaten insects (43% by volume) with smaller amounts of snails (Potamopyrgus antipo‐darum, 23%) and bullies (24%). In Lake Ohau adult insects may be an important food. There were also variations in diet with season and fish size. The stomachs of 147 brown trout (Salmo trutta) and 181 rainbow trout (S. gairdnerii) caught in the same gill nets were also examined. In contrast to sockeye salmon stomachs they contained negligible amounts of zooplankton (< 1% by weight) and large amounts of aquatic insects (50–58% by weight in the Ahuriri Arm of Lake Benmore). Comparisons with juvenile sockeye salmon and kokanee in North American lakes are made. The impact of introductions of sockeye salmon into other New Zealand lakes is discussed.  相似文献   

13.
Transects were made with the Video Plankton Recorder (VPR) in different water masses on the southern flank of Georges Bank in May 1992. CTD-data, chlorophyll fluorescence, and attenuation were measured simultaneously. Images were recorded at a rate of 60 fields per second, as the instrument was towed at 2 m s−1 (4 knots). Tapes from high and low magnification cameras (imaging volumes of 0.62 ml and 33 ml, respectively) were analyzed with respect to the distribution of copepods and other grazers, as well as invertebrate predators. This paper describes the differences in patterns of occurrence of important zooplankters in well-mixed and stratified waters on the Bank and in Slope Water south of these stations. Planktonic taxa were sampled over the same range of scales as the fluorescence and hydrography, allowing direct visual comparisons of the spatial distributions of these variables. Late copepodites of Calanus finmarchicus were strongly concentrated near the surface in the stratified area, while a dense belt of Limacina sp. and Oikopleura sp. occurred below the pycnocline. Other fragile forms were also found to be dominant. Colonies of hydroid polyps were very abundant at the mixed station, especially deeper in the water column, indicating that they may have been transported up from the bottom. Colonies of the diatom Chaetoceros socialis were abundant in the cold bottom water in the stratified region and also in the mixed area. These colonies may have been in the process of sedimenting out of the water column, as similarly sized and shaped marine snow was abundant in the same area. In the Slope Water, acantharia and Trichodesmium were found in the chlorophyll maximum above the pycnocline. Other important genera encountered were: Pseudocalanus, Oithona, Centropages, Obelia, Pleurobrachia and Sagitta. Taxa that occurred in all three areas were often differently distributed with respect to depth and physical parameters, indicating that vernal stratification is an important structuring factor of plankton populations.  相似文献   

14.
Neocalanus tonsus, C. macrocarinatus, and C. australis, three calanids which potentially occur together in New Zealand waters, were raised from eggs and their developmental stages described. All naupliar stages apparently have identical setation. Naupliar stages I—III are very similar. Neocalanus tonsus can be easily identified from naupliar stage IV onwards, whereas C. macrocarinatus and C. australis can be identified with certainty only in the copepodite stages, because their nauplii overlap in size and body proportions. Development at 15 °C from egg to copepodite V took 24 days for N. tonsus, 20.2 days for C. macrocarinatus, and 23.8 days for C. australis. Neocalanus tonsus is the smallest species during early developmental stages but by copepodite III stage is larger than the other two species.  相似文献   

15.
This study compares vertical distributions of Penilia avirostris and Temora turbinata with vertical distributions of chlorophyll a over short time periods at a station in the north-western Gulf of Mexico in the summer and early fall of 1978. In June and July 1978 chlorophyll a and turbidity increased below the thermocline. In September 1978 chlorophyll a was concentrated in the upper mixed layer while turbidity was greatest near the bottom.In June and July P. avirostris and copepodites of T. turbinata were concentrated within the subsurface chlorophyll a layer. Adult T. turbinata were more widely distributed than the copepodites in June but apparently migrated diurnally in July. In September, abundance of all animals generally decreased slightly with depth. This change in animal distribution reflected changes in biotic and abiotic varlables between this cruise and previous cruises. In all cruises, animal distributions were positively correlated with chlorophyll a suggesting that food was the primary influence on distributions of these animals.  相似文献   

16.
采用RT-PCR、RACE等方法,获得了拟穴青蟹PP2A调节亚基B(PP2A-B)的cDNA全序列,全长2040bp,开放阅读框(ORF)为1332bp,可编码443个氨基酸残基。同源分析显示,该基因编码的蛋白与其它一些物种具有很高相似性,推测PP2A-B基因具有很高的保守性。经荧光定量PCR检测,PP2A-B基因在拟穴青蟹多个组织中有表达,且在脑、卵巢、鳃中表达量较高。在拟穴青蟹卵巢发育过程中,PP2A-B基因在卵巢未发育期(I期)表达量最高,此后各期逐渐下降,推测PP2A-B在卵巢中可能以PP2A全酶的形式存在,抑制卵巢发育。  相似文献   

17.
Neocalanus flemingeri, Neocalanus plumchrus, Neocalanus cristatus and Eucalanus bungii are large and dominant mesozooplankton occurring throughout the subarctic Pacific. They are an important trophic link and transporter of organic matter to the mesopelagic zone. Vertical distributions of these copepods were investigated from March to October 2000 in the Oyashio region of the western subarctic Pacific. Neocalanus plumchrus and N. flemingeri were distributed in the surface layer (0–50 m) and N. cristatus and E. bungii in the subsurface layer (50–100 m). However, when examined in detail, clear seasonal and vertical differences were observed. Neocalanus plumchrus was concentrated in the top 20 m from late April to the end of July, and N. flemingeri showed a little deeper distribution from May to July. Neocalanus cristatus showed a deeper distribution than that of grazing individuals of E. bungii from April to early July, but grazing individuals of E. bungii (C3–C6) showed a deeper distribution than that of N. cristatus from the end of July to October. Early copepodites of E. bungii were distributed much shallower than late copepodite stages and overlapped with copepodites of N. plumchrus and N. flemingeri. These results suggest that the four species of large copepods have established habitat segregation by season, vertical distribution and food resource partitioning in the Oyashio region as well as other regions of the North Pacific.  相似文献   

18.
Vigtorniella flokati, a new species of polychaete worm associated with decaying whale remains, is described. Three separate V. flokati populations were sampled using submersibles: two associated with implanted gray whale carcasses in the San Diego Trough (1240 m depth) and the Santa Cruz Basin (1670 m) off California, and one from sperm whale and balaeanopterid bones implanted on the slope of Oahu, Hawaii at 1000 m. Extraordinarily large numbers of live specimens were observed and videotaped in situ using submersibles in the San Diego Trough and the Santa Cruz Basin. The populations on the carcass implanted for 4 months in San Diego Trough, and on the bones implanted for 2 years off Oahu, were composed only of small sized individuals (including juveniles). V. flokati most closely resembles the poorly known V. zaikai Kiseleva, 1992, described from the Black Sea. Forty-six morphological characters were used in a phylogenetic analysis of selected nereidiform polychaetes. The resulting most-parsimonious trees indicate sister taxon status between V. flokati and V. zaikai, and that this clade is sister to the putatively ancient polychaete clade Chrysopetalidae. Whale falls, which are intense point sources of organic enrichment at the deep-sea floor, pass through three successional stages. V. flokati appears to colonize the middle, “enrichment opportunist” stage, inhabiting organic-rich bones and sediments 4–24 months after carcass arrival. V. flokati exhibits remarkable behavior, clinging posteriorly to whale bones or nearby sediments to form a writhing carpet at densities exceeding 8000 m−2. Its extraordinary abundance on whale falls, and apparent absence from other habitats, suggests it to be a whale-fall specialist. The precise feeding mechanism of the worm remains unknown, but we hypothesize that it may utilize dissolved organic carbon derived from the organic-rich setting of whale falls. The widespread occurrence of V. flokati on ephemeral, food-rich habitat islands in the Pacific suggests life-history strategies analogous to those for hydrothermal-vent and cold-seep species.  相似文献   

19.
The distribution and demography of Calanus finmarchicus, C. glacialis and C. hyperboreus were studied throughout their growth season on a basin scale in the Norwegian Sea using ordination techniques and generalized additive models. The distribution and demographic data were related to the seasonal development of the phytoplankton bloom and physical characteristics of water masses. The resulting quantified relationships were related to knowledge on life cycle and adaptations of Calanus species. C. finmarchicus was the numerically dominant Calanus species in Coastal, Atlantic and Arctic waters, showing strong association with both Atlantic and Arctic waters. C. hyperboreus and C. glacialis were associated with Arctic water; however, C. glacialis was occasionally observed in the Norwegian Sea and is probably an expatriate advected into the area from various origins. Demography indicated one generation per year of C. finmarchicus, a two-year life cycle of C. hyperboreus, and both one- and two-year life cycles for C. glacialis in the water masses where they were most abundant. For the examined Calanus species, young copepodites of the new generation seemed to be tuned to the phytoplankton bloom in their main water mass. The development of C. finmarchicus was delayed in Arctic water, and mis-match between feeding stages and the phytoplankton bloom may reduce survival and reproductive success of C. finmarchicus in Arctic water. Based on low abundances of C. hyperboreus CI–III in Atlantic water and main recruitment to CI prior to the phytoplankton bloom, we suggest that reproduction of C. hyperboreus in Atlantic water is not successful.  相似文献   

20.
哈维氏弧菌被观察到与海洋寄生性纤毛虫刺激隐核虫具有内共生现象,其作为一种致病性细菌,可导致感染刺激隐核虫的大黄鱼产生严重的继发性细菌感染。我们通过16s宏测序技术对刺激隐核虫的细菌群落进行鉴定,并通过标准的细菌培养方法分离鉴定出哈维氏弧菌。通过透射电镜和荧光原位杂交方法,在刺激隐核虫的细胞胞质中,均观察到内共生的哈维氏弧菌的存在;而在其细胞核中,则没有相关信号存在。哈维氏弧菌与刺激隐核虫的相关关系以及内共生的哈维氏弧菌对刺激隐核虫的影响作用,仍需要深入进行研究。  相似文献   

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