Are fiddler crabs potentially useful ecosystem engineers in mangrove wastewater wetlands?

The effect of different organic-rich sewage concentration (0%, 20% and 60% diluted in seawater) and absence or presence of mangrove trees on the survival, bioturbation activities and burrow morphology of fiddler crabs species was assessed. After 6 months, males of both species always showed higher survival (80%) when compared to females (20%). Crabs inhabiting pristine conditions achieved higher survival (67–87%) than those living in sewage-exposed mesocosms (40–71%). At 60% sewage loading, fiddler crabs processed less sediment (34–46%) during feeding and excavated slightly more sediment (45–80%) than at pristine conditions. While percent volume of the burrow chambers increased (13–66%) at contaminated mesocosms for both vegetation conditions, burrows were shallower (33%) in bare cells loaded with sewage. The results show that fiddler crabs presented moderate mortality levels in these artificial mangrove wetlands, but mainly in sewage impacted cells. However, they still function as ecosystem engineers through bioturbation activities and burrow construction.     

一秋龄性成熟中华绒螯蟹的生物学─2.生殖、越冬行为及脱壳的可能性

本文对池塘育成的一秋龄成熟中华绒螯蟹生殖行为的观察表明,其具有生殖洄游习性,当年１０月是其活动高峰期,而湖泊放流育成的早熟河蟹其活动高峰在当年１０月及翌年３月,在湖泊淡水水体中少数个体有交配的行为,翌年３月份发现部分雌蟹的纳精囊内有精液。     

Molting as a mechanism of depuration of metals in the fiddler crab, Uca pugnax

Metal distributions in the exoskeleton and soft tissues of the fiddler crab, Uca pugnax, were examined during intermolt and immediate postmolt to determine if distribution of the metals changed prior to molting and to determine if molting is a feasible mechanism to depurate metals. Fiddler crabs were collected from two locations in New Jersey, a highly contaminated site and a relatively clean environment. The crabs from the contaminated site had higher concentrations of metals in their soft tissues for Cu, significantly higher concentrations of Pb in their soft tissues and carapace, but did not have any significant differences in concentrations of Zn in comparison to their conspecifics from the relatively clean site during intermolt. Crabs from the contaminated site has significantly higher levels of Cu, Pb, and Zn in both their soft tissues and exuvia immediately after molting. Crabs from both sites shifted copper and zinc from the carapace into the soft tissues prior to molting. Lead distribution shifted from the soft tissues to the exoskeleton prior to molting in the population from the contaminated site but shifted from the exoskeleton into the soft tissues for the relatively clean site. Average percent of the total body burden eliminated during the molting process for the highly contaminated site varied with each metal, 12% Cu, 76% Pb, and 22% Zn. Average percent of the total body burden eliminated during molting process for the relatively clean site also varied with each metal and was significantly lower than the conspecifics from the contaminated site, 3% Cu, 56% Pb, and 8% Zn. Molting can reduce overall body burdens significantly and is a feasible mechanism to depurate lead.     

Hitching a ride on a hermit crabs home: Movement of gastropod shells inhabited by hermit crabs

There is little information on the movement and connectivity patterns for many species. The movement by shells occupied by the hermit crab Pagurus bernhardus and the organisms encrusting these shells was investigated on the south coast of Wales (UK). Hermit crabs shells moved considerable distances along the shore over 1 month periods, moving a minimum mean distance (±SE) of 148 (±8) and 174 (±9) m from release sites in the January and August respectively. Hermit crab-inhabited shells were also found to travel across habitats (sandy areas) that are unsuitable for both hermit crabs and epibionts. Through the examination of 150 of the most abundant shells used by P. bernhardus (Nucella lapillus), twelve epibiont species were found (10 animal and 2 algal species) and choice experiments demonstrated that hermit crabs preferred epibiont covered shells (84%), compared with bare shells (16%). The distance that shells were moved and the preference of hermit crabs for epibiont encrusted shells, coupled with the ability for epibionts to cross unsuitable habitats, may provide a dispersal advantage for epibiont species.     

蟹类微卫星DNA标记的筛选及其在遗传学研究中的应用

微卫星DNA标记是近年来最受研究者青睐的分子标记之一.由于其具有高度多态性、共显性遗传、基因组中含量丰富且随机分布等特点,已被应用于种群分化研究、亲缘分析、基因连锁分析、进化以及生态学研究等许多领域.近年来,蟹类微卫星的研究报道日益增多.文中对蟹类微卫星分离方法、引物设计、遗传学特性以及在种群遗传、家系分析、遗传多样性评价等方面的最新研究进展进行综述,并分析微卫星分析中无效等位基因(null allele)、"结巴"带(stutter bands)和上游等位基因"扩增丢失"现象(upper allelic dropout)的产生原因以及对微卫星基因型判读带来的影响.     

Implementing geostatistical analysis to study spatio-temporal distribution patterns of swimming crabs(Portunus trituberculatus)

This study attempted to compare the performance of local polynomial interpolation,inverse distance weighted interpolation,and ordinary kriging in studying distribution patterns of swimming crabs.Cross-validation was used to select the optimum method to get distribution results,and kriging was used for making spatial variability analysis.Data were collected from 87 sampling stations in November of 2015(autumn) and February(winter),May(spring) and August(summer) of 2016.Results indicate that swimming crabs widely distributed in autumn and summer:in the summer,they were more spatially independent,and resources in each sampling station varied a lot;in the winter and spring,the abundance of crabs was much lower,but the individual crab size was bigger,and they showed the patchy and more concentrative distribution pattern,which means they were more spatially dependent.Distribution patterns were in accordance with ecological migration features of swimming crabs,which were affected by the changing marine environment.This study could infer that it is applicable to study crab fishery or even other crustacean species using geostatistical analysis.It not only helps practitioners have a better understanding of how swimming crabs migrate from season to season,but also assists researchers in carrying out a more comprehensive assessment of the fishery.Therefore,it may facilitate advancing the implementation in the pilot quota management program of swimming crabs in northern Zhejiang fishing grounds.     

Distribution and retention of Petrolisthes armatus in a coastal plain estuary: The role of vertical movement in larval transport

Since transport of planktonic larvae is essential to the maintenance and expansion of many marine species, we examined the spatial and temporal distribution of green porcelain crab Petrolisthes armatus (Gibbes, 1850) larvae and the possible underlying physical and behavioral mechanisms using a combination of field observations and numerical modeling. The field study consisted of observations of larval abundance and distribution as well as hydrographic surveys of the Satilla River estuary on the east coast of the USA in August 2006. Larvae were found throughout the water column within the tributaries but primarily at depth in the main river. A numerical model was used to examine the effect of flow and possible larval behavior responsible for the observed distribution and the consequences for larval retention in the estuary. Model results that included downward larval movement are consistent with the field observations, supporting the hypothesis that P. armatus larvae vertically migrate within the water column, which aids in their retention within the estuary.     

Reproductive periodicity of the tropical crab Callinectes arcuatus Ordway in Central America

The Gulf of Nicoya, an estuary on the Pacific coast of Central America, contains a large population of the portunid crab Callinectes arcuatus. Results of a 12 month survey indicated that spawning activity occurs throughout the year, but with a distinct peak during the five-month dry season (December-April). Mature females were most prevalent in the upper regions of the gulf during the rainy season and appeared to migrate to the lower gulf to spawn during the dry season. Patterns of spawning and apparent migration differed from those reported in an earlier study of C. arcuatus along the Pacific coast of Mexico.