武汉三角湖浮游甲壳动物群落结构

三角湖是长江中下游地区典型的小型城市湖泊,近年来其富营养化趋势明显。2014年7月至2015年6月对湖中浮游甲壳动物群落及其影响因子进行了调查,旨在为湖泊污染防治和生态修复提供依据。在三角湖共采集浮游甲壳动物9科17属22种。浮游甲壳动物全年平均密度为(3.7±3.6)ind/L,各月密度变化范围为0.6~13.1 ind/L,夏季和秋季密度较低,密度峰值出现在2月。浮游甲壳动物全年大部分时间(5、6月除外)以桡足类及无节幼体占优势,其比例为55.2%~95.4%。浮游甲壳动物物种丰富度变化范围为6~15,平均值为10±3,夏季浮游甲壳动物物种丰富度较低。浮游甲壳动物群落Simpson指数变化范围为0.76~0.90,平均值为0.80±0.04。Pearson相关分析表明,浮游甲壳动物总密度与水深呈显著负相关(r=﹣0.636,P0.05,n=11),显示季节性的水位波动影响浮游甲壳动物密度。典范对应分析(CCA)显示,水温和透明度是影响浮游甲壳动物物种组成季节变化的主要环境因子(P0.05)。高密度的鲢(Hypophthalmichthys molitrix)、鳙(Aristichthys nobilis)放养引起的摄食压力可能是三角湖浮游甲壳动物密度较低的主要原因之一。     

鲢中华鳋线粒体基因组的基因组成及特征分析

研究旨在测定隶属桡足亚纲(Copepoda)杯口水蚤目(Poicilostom atoida)的寄生甲壳动物鲢中华鳋(Sinergasilus polycolpus)线粒体DNA(mtDNA)序列,分析其结构特征,为节肢动物系统进化研究积累资料。利用简并引物扩增鲢中华鳋Cytb和COI基因片断,据此设计特异性引物Long-PCR扩增鲢中华鳋mtDNA序列,拼接后得到12917bp的序列(GenBank登录号为EU621723)。这段序列A、T、C、G碱基含量分别为35.0%、35.8%、14.0%和15.2%,GC-Skew和AT-Skew值分别为0.041和-0.011。通过序列同源性和结构分析,鉴定了35个基因,包括13个蛋白编码基因、21个tRNA基因和1个12SrRNA基因,推测未能扩增到的片段包含16S rRNA、tRNAArg和tRNAThr基因以及控制区序列。tRNA基因长度在54-63bp之间,均可折叠成典型的三叶草结构,但TψC臂长度变化较大,其中有三个缺少TψC臂。35个基因中,4个蛋白质编码基因和7个tRNA基因位于N链,其余的位于J链。基因间重叠有12处,重叠碱基量达159bp。进一步研究桡足类及相关类群线粒体基因组的遗传特征将有助于揭示和阐明桡足类系统发育关系。       

Cyst ornamentation in aquatic invertebrates: a defence against egg-predation

Hydrobiologia - Eggs, including encysted embryos (cysts) of aquatic invertebrates may not only be thick-walled, but also provided with various external ornamentations such as spines and...     

Patterns of prey selectivity in the cyclopoid copepod Mesocyclops thermocyclopoides

In the shallow and eutrophic subtropical aquatic ecosystems, which it generally inhabits, the omnivorous copepod Mesocyclops thermocyclopoides encounters a wide variety of animal prey types including ciliates, rotifers, and cladocerans. We studied prey selectivity in laboratory-reared adult females of this species given a choice of (i) prey types belonging to different taxa (ciliates, rotifers, cladocerans, and cyclopoid nauplii), and (ii) different prey species within a taxonomic group differing in body size, morphology or behaviour. We also tested the effect of different proportions of prey species on its selectivity. Prey type proportion had no significant effect on selectivity of the copepod, nor was there any evidence of switching based on the relative abundance of prey. Among the ciliate prey species tested, the largest species, Stylonychia mytilus was positively selected regardless of its relative abundance, while the smallest, S. notophora was selected only when its density was higher. Offered a choice of three species of a brachionid rotifer differing in size, the copepod selected the largest of them, Brachionus calyciflorus, and avoided the smallest B. angularis. The evasive rotifer Hexarthra mira was also avoided. When prey choice included three cladoceran species Daphnia similoides, Moina macrocopa and Ceriodaphnia cornuta, the copepod selected the intermediate-sized M. macrocopa regardless of the abundance of the other two species. Although it fed on Mesocyclops nauplii when there was no choice, M. thermocyclopoides avoided them when alternative food was available. In a multispecies prey choice test, the copepod selected predominantly the rotifer B. calyciflorus and the cladoceran M. macrocopa. We suggest that the prey selectivity patterns shown by M. thermocyclopoides are adaptive in that they lead to ingestion of the most profitable prey.     

Therodamas Krøyer, 1863 (Copepoda: Ergasilidae) from the Piauí River estuary,State of Sergipe,Brazil

The pre-metamorphic female of Therodamas serrani Krøyer, 1863 is described for the first time based on new material collected from the upper reaches of Piauí River estuary, northeastern Brazil. Females are present in the plankton throughout the year, and are common during the rainy season. Five of the six currently accepted species of Therodamas are known only from metamorphic females, making identification of pre-metamorphic stages problematic. Identification of T. serrani was made on the basis of the leg setation and the very similar proportions of the two apical endopodal spines on leg 1.     

Harpacticoid copepod communities of floating seaweed: controlling factors and implications for dispersal

The structure of harpacticoid copepod communities of floating detached intertidal algae was studied by surveys and experiments. Seaweed clumps were sampled from Faxaflói, western Iceland, at various distances from the shore (0.2–14 km). Altogether 20 species of harpacticoids were found in these clumps, most of them typical phytal species. Multidimensional scaling ordination (MDS) separated the samples into three distinct clusters in which the communities were significantly different from each other. The distance from shore did not seem to affect the community structure. However, diversity and abundance of harpacticoids increased with size and complexity of the clumps. Experimental Ascophyllum nodosum fronds placed 300–600 m offshore were rapidly colonised by harpacticoids. Density and species diversity were, after 20 days afloat, higher than in the free-floating clumps. Species of the genus Harpacticus were successful colonisers, in particular Harpacticus chelifer and Harpacticus uniremis. In a survey of macrofauna (0.5-mm sieve) on floating algae clumps from various locations around Iceland, H. chelifer was present in all clumps studied, up to 117 km offshore. Its sex ratio was skewed towards females, often with a high ratio of ovigerous females. There was, however, no evidence that this species is using the algal clumps as a platform for reproduction.     

A new species of Acontiophorus Brady, 1880 (Copepoda: Siphonostomatoida) from Ushuaia,Argentina

A new species of Acontiophorus belonging to the family Asterocheridae was found in Ushuaia, Patagonia, southern Argentina. The new species is distinctive in having 9-segmented antennule, five setae on terminal endopodal segment of leg 1, seven elements on terminal segment of leg 1 and leg 4 exopods, and characteristic setation on maxillule lobes. This combination of characteristic features does not occur in any other species of the genus. The genus Acontiophorus is recorded for the first time from the South Atlantic.     

A new species of the deep‐sea copepod genus Scutogerulus (Calanoida: Arietellidae) from the hyperbenthic waters of Okinawa,Japan

A new species of the rare arietellid genus Scutogerulus is described from deep hyperbenthic waters off Okinawa, southwestern Japan. This is the second species of the genus. Phylogenetically significant characteristics known only on the basis of the type species are confirmed by the discovery of the new congener, in particular: (1) the genital system of the female exhibits the most plesiomorphic condition of any arietellid genus; (2) the well developed setae on the endopodal segments of the maxillae and maxillipeds are modified into ‘shield‐like setae’ similar to the ‘button setae’ in another arietelloidean family, the Augaptilidae; (3) the outer distal spine on the first exopodal segment of leg 1 is absent.