Small-scale Spatial Distribution of a Pyramidellid Snail Ectoparasite, Boonea impressa, in Relation to its Host, Crassostrea virginica, on Oyster Reefs

Abstract. The pyramidellid snail, Boonea (= Odostomia) impressa (SAY), is an important ectoparasite of the oyster, Crassostrea virginica (G melin ). The small-scale spatial distribution of snails was examined in 11 oyster populations in the Copano Bay - Aransas Bay area of the Texas coast. Snails were contagiously distributed (s²/>1) and positively spatially autocorrelated. Patchiness was better developed and patches were larger on enclosed reefs than on more exposed open-bay reefs, probably because higher wave energy and increased distance between oyster clumps limited clump-to-clump movement by snails on open-bay reefs. Small snails were consistently distributed differently from large snails because small snails were less host specific. As the snails grow, a narrowing of host preference results in a substantial change in spatial distribution. Snails were consistently more contagiously distributed than their hosts; however, snail distribution was not host-density dependent. Factors determining the spatial distribution of the host had surprisingly little effect on the distribution of snails. Snail aggregates apparently form randomly by chance meetings of a few snails and then grow by attraction of additional snails. Consequently, snail behavior, which determines the size and length of time a patch retains its integrity, and the age distribution of the snail population may be the two most important factors, besides population size, determining the impact of B. impressa on oyster populations.     

改性粘土絮凝法对太平洋牡蛎(Crassostrea gigas)稚贝的影响

本实验以太平洋牡蛎稚贝(Crassostrea gigas,～0.2cm)为对象,研究了HDTMA有机改性粘土和PAC无机改性粘土絮凝法治理赤潮时对海洋底栖生物的影响。96h急性毒性实验中二者对牡蛎稚贝的半致死浓度(LC50)分别为4.62g/L和2.67g/L。在能够有效去除赤潮微藻的浓度条件下(0.10g/L),经慢性毒性实验发现改性粘土对牡蛎稚贝成活率无影响,牡蛎生长速度较对照组没有明显差异,滤食率比培养实验初始时升高了3～4倍,同时在牡蛎超微组织结构中未发现机械损伤。通过模拟改性粘土去除赤潮生物(Heterosigma akashiwo和Prorocentrum donghaiense)过程中对生物体的影响,发现改性粘土絮凝法通过去除赤潮藻能显著提高牡蛎的存活率,所以HDTMA有机改性粘土和PAC无机改性粘土絮凝法在赤潮生物防控中可以作为一项有效的应急措施。     

Population dynamics of Acartia pacifica (Copepoda: Calanoida): the importance of benthic-pelagic coupling

1Introduction Benthic -pelagic coupling refers to the two -way exchange or flux of matter between benthic andpelagic environments in aquatic systems. Most stud-ies have focused on the deposition of non-living or-ganic matter to the seabed, resuspension an…     

Population genetics and evolutionary demography of Ucides cordatus (Decapoda: Ocypodidae)

Variation in a fragment of the mitochondrial control region was investigated to assess the population history of the mangrove land crab, Ucides cordatus L., based on 100 individuals from five locations throughout the Brazilian coast. There was considerable variability in the studied fragment, with every individual showing a distinct haplotype. When regions of ambiguous alignment were removed, 90 haplotypes were still recognized, of which only 1 was shared among locations. There was no statistically significant evidence for geographical structure in the pattern of genetic variability based on a nested clade analysis, even though the geographical distances among the farthest collection sites exceeded 3000 km. Moreover, the mismatch distribution of pairwise differences showed a smooth unimodal distribution that is consistent with a recent population expansion of U. cordatus, either when each location was analysed in isolation or when all samples were combined. Interestingly, the estimates for the duration of such expansion vary latitudinally, suggesting that the expansion of the population of U. cordatus proceeded in a southward direction. These results indicate a possible relationship between the growth in the population of the mangrove land crab and the dynamics of mangrove ecosystems during the Quaternary.     

Biology and Population Dynamics of Donax trunculus L. (Bivalvia: Donacidae) in the South Adriatic Coast (Italy)

Biology and population dynamics of the suspension-feeding wedge clam Donax trunculus (Linnaeus, 1758) were studied for 13 months (November 1994–April 1996) along the Italian Southern Adriatic coast near the Lagoon of Lesina. Specimens were found at depths between 0 and 2 m, mainly in fine grain bottoms. The spatial coastal distribution showed an intraspecific segregation between young and adult wedge clams. A unimodal recruitment (length >4 mm) occurred in winter (December–February). Length frequency distributions were used to determine age and growth rate. Three year classes were regularly observed and their growth pattern defined. The population showed a maximum length of 37 mm and a longevity of 4 years. Analysis of seasonal variations in the reproductive cycle showed that gametogenesis occurred in spring in females. After the spawning season (March–July) females of D. trunculus remained in a resting stage from August to January.     

久效磷和林丹共同作用下对细小色矛线虫种群动态的毒性效应

采用联合暴露的方法研究久效磷和林丹共同作用下对细小色矛线虫种群动态的毒性效应。结果表明:久效磷和林丹联合暴露极显著降低了细小色矛线虫子一代和子二代种群增长率,具有剂量-效应关系;并导致子一代种群偏雌性化。与对照相比,Ⅰ(0.1μg/L久效磷和0.005μg/L林丹)、Ⅱ(1.0μg/L久效磷和0.05μg/L林丹)、Ⅲ(10.0μg/L久效磷和0.5μg/L林丹)联合暴露组子一代种群增长率分别降低了64.82%、74.90%、78.28%,联合暴露组Ⅳ(100.0μg/L久效磷和5.0μg/L林丹)子一代种群呈负增长;Ⅰ、Ⅱ联合暴露组子二代种群呈负增长。Ⅰ、Ⅱ、Ⅲ、Ⅳ联合暴露组的亲代总产卵量分别降低了68.27%、72.88%、80.81%和83.76%;Ⅰ、Ⅱ、Ⅲ联合暴露组的子代总产卵量分别降低了73.66%、78.67%和85.66%。此外,细小色矛线虫子一代和子二代卵的受精率和胚胎孵化率的降低、胚胎发育持续时间时间的延长、L1幼虫畸形率的升高与种群动态的变化密切相关。久效磷和林丹共同作用下对细小色矛线虫种群动态具有较强的毒性效应。     

太平洋牡蛎配子和精子人卵的扫描电镜观察及胚胎发育的初步研究

通过扫描电镜观察,太平洋牡蛎精子由头部、中段和尾段组成.精子全长约21.6μm,尾段长约18.2μm,末端观察到"针眼"样结构;头部最大处的直径约2.6μm;中段直径约1.1μm;未成熟精子尾段中部出现膨大,该处直径约0.3μm.卵呈梨形;卵的直径约为41.9μm.卵表面有微绒毛组成的皱折结构,可见卵黄膜孔.卵质收回时,在卵表面卵柄处可见明显的树枝状结构.受精后,受精卵表面的卵黄膜剥离处可见较多数量的皮质小泡.在水温21.2～23.5℃,精卵混合34min时,释时出第1极体;1h22min时,放出第2极体;21h55min时,胚胎发育至初期D形幼虫.     

太平洋牡蛎配子和精子入卵的扫描电镜观察及胚胎发育的初步研究

通过扫描电镜观察 ,太平洋牡蛎精子由头部、中段和尾段组成。精子全长约 2 1 .6μm ,尾段长约 1 8.2 μm ,末端观察到“针眼”样结构 ;头部最大处的直径约 2 .6μm ;中段直径约 1 .1 μm ;未成熟精子尾段中部出现膨大 ,该处直径约 0 .3μm。卵呈梨形 ;卵的直径约为 41 .9μm。卵表面有微绒毛组成的皱折结构 ,可见卵黄膜孔。卵质收回时 ,在卵表面卵柄处可见明显的树枝状结构。受精后 ,受精卵表面的卵黄膜剥离处可见较多数量的皮质小泡。在水温2 1 .2～ 2 3.5℃ ,精卵混合 34min时 ,释时出第 1极体 ;1h2 2min时 ,放出第 2极体 ;2 1h55min时 ,胚胎发育至初期D形幼虫。     

The Dynamics of an Introduced: Balanus glandula Population in the Southwestern Atlantic Rocky Shores. The Consequences on the Intertidal Community*

Abstract. This paper deals with the population dynamics of the introduced barnacle Balanus glandula in a port shelter and a rocky shore exposed of a southwestern Atlantic area. Replicated areas in both zones were denuded monthly and censused in both the high intertidal and the upper mid intertidal zone. The settlement pattern. recruitment, mortality and growth of B. glandula and a comparative successional pattern in both areas were recorded. Recruitment began in winter, i.e., July in the port and August in the rocky shore. In the port, green algae dominate up to a final community of Balanus glandula all along the intertidal, while in rocky shores the red encrusting alga Hildenbrandia lecanellieri establishes a cover that is replaced by the mytilid Brachidontes rodriguezi in the mid intertidal and by B. glandula in the high intertidal and upper mid intertidal. B. glandula densities were greater in the upper mid intertidal 19 600 and 5050 indiv. · m^-2 in the port and rocky shore, respectively than in the high intertidal 13600 and 1100 indiv.· m^-2, respectively. Mortality was greater in the port up to 62%, but heavy settlement allows a final density 4 times greater than in eulittoral rocky shores and 10 times greater than in the high intertidal. The winter reproduction of Balanus glandula, the absence of predators, the neutral or beneficial effect of algae. with spatial and temporal partitioning of substrate allows it to successfully outcompete mussels and other barnacle species from the intertidal community of both sheltered and exposed areas.     

Population dynamics and condition index of natural stock of blood cockle,Tegillarca granosa(Mollusca,Bivalvia,Arcidae) in the Marudu Bay,Malaysia

The population parameters of blood cockles, Tegillarca granosa in the intertidal zone of Marudu Bay, Sabah,Malaysia were investigated based on monthly length-weight frequency data(July 2017 to June 2018). A total of 279 cockle individuals with shell length and weight ranging from 27.7 mm to 82.2 mm and 13.11 g to 192.7 g were subjected to analysis. T. granosa in Marudu Bay showed a consistent moderately high condition index 4.98±0.86 throughout the year. The exponent b of the length-weight relationship was 2.6 demonstrating negative allometric growth. The estimated asymptotic length(L_∞), growth coefficient(K) and growth performance(?) of the T.granosa population in Marudu Bay were estimated at 86.68 mm, 0.98 a~(-1) and 3.87, respectively. The observed maximum shell length was 82.55 mm and the predicted maximum shell length was 84.44 mm with estimated maximum life span(t_(max)) of 3.06 years. The estimated mean lengths at the end of 2, 4, 6, 8, 10 and 12 months of age were 21.31 mm, 31.16 mm, 39.53 mm, 46.63 mm, 52.67 mm and 57.79 mm. Total, natural, and fishing mortalities were estimated at 2.39 a~(-1), 1.32 a~(-1) and 1.07 a~(-1). The exploitation level(E) was 0.45. Results of the current study also demonstrated that T. granosa in the Marudu Bay has two major recruitment peaks; one in March and another in October. The exploitation level revealed that natural stock of T. granosa in the Marudu Bay was approaching the maximum exploitation level. If such trend continues or demand for T. granosa is increasing,coupled with no effective fisheries management in place, possibility of the T. granosa population in the Marudu Bay to collapse is likely to elevate.     

长牡蛎壳黑选育系F7代的生长规律和模型

为研究长牡蛎壳黑选育系F7的生长规律,分别采用了线性回归方程和Von Bertalanffy、Gompertz和Logistic 3种非线性模型对长牡蛎(Crassostrea gigas)壳黑选育系F7幼虫期和养成期的生长参数进行生长模型构建,并对长牡蛎壳黑选育系F7养成期的壳高、壳长、壳宽分别与总重进行曲线拟合,以研究长牡蛎壳黑选育系F7的生长规律。研究表明,幼虫期壳高、壳长对日龄的回归方程分别为y=39.723 8+11.697 2x,R^2=0.991;y=31.346 2+9.802 8x,R^2=0.986。壳高与壳长成线性相关,回归方程为y=4.867 0+1.175 0x,R^2=0.989。养成期长牡蛎壳黑选育系F7的总重增长与Von Bertalanffy生长模型最符,R^2=0.955;长牡蛎壳黑选育系F7的总重与壳高、总重与壳长、总重与壳宽分别遵循复合曲线y=0.706×1.055~x,R^2=0.991、y=1.336×1.075~x,R^2=0.983、y=1.287×1.154~x,R^2=0.944。     

自然死亡和亲体补充关系对黄鳍金枪鱼资源评估的影响

黄鳍金枪鱼（Thunnus albacares）是全球经济和生态价值最重要的鱼类之一,其资源养护和管理受到各方的高度关注。本文依据年龄结构产量模型研究了印度洋黄鳍金枪鱼的资源状态,着重探讨了其生活史特征的不确定性对资源评估结果的影响。研究结果显示,1960−1985年间印度洋黄鳍金枪鱼资源量保持相对稳定,之后开始逐渐下降,相应的捕捞死亡系数也在2010年之后迅速增加,目前其种群可能存在过度捕捞（F₂₀₂₀/F_MSY>1,SSB₂₀₂₀/SSB_MSY<1）。印度洋黄鳍金枪鱼的资源评估结果对自然死亡系数（M）和亲体−补充量关系陡度参数（h）的改变较为敏感。当h增大时,SSB_MSY和初始SSB（即SSB₀）的变化较大,分别减少了约25.53万t和34.04万t;F₂₀₂₀/F_MSY减小了1.15。当M增大时,F₂₀₂₀/F_MSY、SSB_MSY、SSB₀均减小。综上所述,今后应重视印度洋黄鳍金枪鱼资源的开发程度,重视其资源养护管理,同时充分了解黄鳍金枪鱼的生活史特征,提高自然死亡系数和陡度参数估算的准确性,以期为印度洋黄鳍金枪鱼的资源评估和渔业管理提供更准确的信息,实现该渔业的长期可持续发展。     

Population Structure of Blennius incognitos BATH 1968 (Pisces: Teleostei: Blen-niidae) during the Reproductive Period with Comments on Age and Growth of Small Benthic Littoral Fishes

Abstract. Length frequency distribution, condition factor and parasite infection of Blennius incog-nitus from three different areas near Rovinj, Yugoslavia have been investigated. Differences between considered parameters in three populations of B. incognitus have been found and discussed. Fishes were aged by otolith reading. Mean life span, growth rate, sex ratio and a sexual dimorphism in body size were noted in this littoral blenny. Our findings are discussed and compared with data on comparable littoral fishes.     

Growth dynamics and bioactivity variation of the Mediterranean demosponges Agelas oroides (Agelasida, Agelasidae) and Petrosia ficiformis (Haplosclerida, Petrosiidae)

Growth dynamics and bioactivity variation of the Mediterranean demosponges Agelas oroides and Petrosia ficiformis were investigated over 15 months at Paraggi and Colombara within the Marine Reserve of Portofino Promontory (Mediterranean Sea, Ligurian Sea, Italy). For both species, growth rates varied between individuals and were unaffected by initial sponge size. The two species showed a different trend in growth pattern: A. oroides did not vary significantly between seasons, sites and depths; in contrast, some individuals of P. ficiformis showed a seasonal pattern, shrinking during winter as water temperature decreased and growing during summer when water temperature increased. Differences in growth between the two species may result from different reproductive cycles, food availability, species-specific thermophily and patterns of spatial competition. Moreover, spatial competition probably induced sponges to produce bioactive secondary molecules. Spatial and temporal variation of bioactivity of both species was examined for the first time by studying its effect on human neuroblastoma cells. The bioactivity of A. oroides extracts differed significantly between seasons, sites and depths, whereas the cytotoxicity of P. ficiformis differed significantly between seasons and depths (differences for sites were not determined). These results suggest the possible influence of environmental factors on bioactive metabolite biosynthesis.     

Influence of Particle Mixing on Vertical Profiles of Chlorophyll a and Bacterial Biomass in Sediments of the German Bight, Oyster Ground and Dogger Bank (North Sea)

In May and September 1999 11 stations were sampled in the southern and central North Sea, located in the German Bight, eastern Oyster Ground and Dogger Bank. The study focused on the influence of particle mixing on transport of chlorophyll a to deeper sediment layers and vertical bacterial distribution (max. DEPTH=10 cm). The sampling stations were chosen to reflect a gradient in environmental conditions in the North Sea. The sampling stations differed in respect to redox potential (eH up to −243 mV in the German Bight and up to 274 mV in the offshore regions), silt content (up to 54% in the German Bight and 0·34% at the northern Dogger Bank) and different proportion of fresh organic material on total organic matter content (C/N ratios ranging from 9·27 in the German Bight up to 1·72 in the offshore sediments). Although bacterial densities (8·55×10⁹ g⁻¹in the German Bight up to 0·35×10⁹ g⁻¹in offshore sediments) were significantly correlated to chlorophyll a content in the sediment (P<0·01), inconsistencies in the temporal pattern of both variables in the surficial sediment layer suggested, that the dynamics of bacterial densities is generally controlled by food supply but also by other variables. The chlorophyll a content in the surficial sediments of the German Bight (up to 1·84 μg g⁻¹) was significantly higher than in the Oyster Ground (up to 0·58 μg g⁻¹) and the Dogger Bank area (up to 0·68 μg g⁻¹). With increasing chlorophyll a input to the benthic realm a subsequent enhanced burial of this compound into deeper sediment layers was expected either by biological (bioturbation) or by physical sediment mixing. However, the vertical profile of chlorophyll a decreased steeply in the sediments of the German Bight. Contrary, subsurface peaks were measured in the offshore areas. It was concluded from these results, that the vertical distribution of organic matter in sediments is less limited by the quantitative input from the water column but concomitant with particle mixing itself. The extent and possible mechanisms of particle mixing in the different study areas in relation to specific environmental factors is discussed.