Species Composition and Diversity of Macrobenthos in the Intertidal Zone of Xiangshan Bay,China

Xiangshan bay is a narrow semi-closed bay and situated on the northwestern coast of the East China Sea. Over past decades, it has become to a major bay with intensive human activities, dense urbanized area, and poor water quality. The aim of this paper was to reveal the ecological status through the elucidation of the species composition, abundance, biomass and diversity of macrobenthos in this bay. Six intertidal sections were surveyed from January 2007 to November 2008 quarterly. Sections TG, HD and XH are located in the three inner bays, sections QJ and WS are located near the thermal power plants, and section XX is located at the outer part of Xiangshan Bay. Great variations in macrobenthos community were indentified, and the species composition of the community in the present study showed the dominance in the order of molluscs(bivalves and gastropods), crustaceans and others, and only few Polychaeta were recorded. Only three dominant species, Littorina brevicula, Ilyplax tansuiensis, and Cerithidea cingulata were collected in all the sections, and a total of 19 dominant species were recorded only in one section. Two-way ANOVA analyses of abundance indicated that there were significant differences among sections or seasons. Shannon-Wiener diversity index(H') had its maximum(2.45) in section QJ, and minimum(1.76) in section TG. Multiple irregular k-dominance plots clearly showed that the study area was polluted and the macrobenthos community was under stress. We conclude that the macrobenthos of Xiangshan Bay have been disturbed by human activities, especially at the interior bay.

Effects of Low Temperature Stress on the Morphology and hsp70 and hsp90 Gene Expression of Phascolosoma esculenta

Phascolosoma esculenta is an intertidal organism that has recently attracted attention because of its ability to survive at relatively low temperatures.However,the gene regulation in P.esculenta in relation to its response to low temperatures is unclear.To explore the low temperature adaptability of P.esculenta,this study analyzed the changes in the morphology and hsp70 and hsp90 gene expression of P.esculenta exposed to a low temperature gradient.At 5℃,P.esculenta stretched and softened,and some individuals moved apart from the group.Histological analysis revealed cuticle breaches,myofiber scattering,disruption of the body wall,and epithelial layer dispersion and muscle fiber rupturing in the nephridium.Furthermore,the mRNA expression levels of hsp70 and hsp90 increased under acute low temperature stress,suggesting that these genes function in low temperature tolerance.Overall,low temperature stress causes morphological changes and histological damage in P.esculenta,and hsp70 and hsp90 potentially function in the low temperature adaptability of P.esculenta.Our results provide new insights into the adaptive strategies of P.esculenta under low temperature environments.

Chlorophenols in marine organisms from the southern coast of Hangzhou Bay,China,and an assessment of risks posed to human health

The composition of chlorophenols in marine organisms from the southern coast of Hangzhou Bay, China, was analyzed and the health risks posed to humans assessed. A total of 19 chlorophenols from 16 types of marine organism were analyzed across nine survey sections in Hangzhou Bay. The chlorophenols were analyzed by gas chromatography-mass spectrometry using a DB-5MS quartz capillary column. The concentrations of monochlorophenol, dichlorophenol, trichlorophenol, tetrachlorophenol, and pentachlorophenol ranged from below the detection limit(ND) to 132 μg/kg, ND–51.0 μg/kg, ND–42.5 μg/kg, ND–69.0 μg/kg, and ND–9.06 μg/kg, respectively. Additionally, concentration differences between each type of chlorophenol were not significant( P >0.05). However, significant differences were found between monochlorophenol( F =8.13, P <0.01) and total chlorophenol(F =5.19, P <0.01) concentrations. As the noncarcinogenic risk indices were <0.1(10-5 –10-2) for all of the organisms, no high risk was posed by 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,4,5-trichlorophenol, 2,3,4,6-tetrachlorophenol, and pentachlorophenol to humans consuming marine organisms from the study area. Furthermore, the carcinogenic risks posed by 2,4,6-trichlorophenol and pentachlorophenol were lower than limits set by the International Commission on Radiological Protection and the US Environmental Protection Agency. However, the noncarcinogenic and carcinogenic risks posed by chlorophenols in marine organisms from four of the survey sections(Sizaopu, Niluoshan, Longshan Town and Xinhong zha) were higher than the other survey sections.

Environmental hypoxia induces apoptosis in large yellow croaker Larimichthys crocea via both intrinsic and extrinsic pathways

Hypoxia has become an unfavorable factor affecting the sustainable development of the large yellow croaker Larimichthys crocea,an economically important mariculture fish in China.Apoptosis is a consequence of hypoxia on fish.However,the effects of hypoxia stress on apoptosis in L.crocea remain largely unknown.We investigated the effect of environmental hypoxia on apoptosis in L.crocea.Results show that hypoxia induced apoptosis in L.crocea both in vivo and in vitro.The mitochondrial membrane potential was significantly reduced in large yellow croaker fry(LYCF)cells.The expression levels of Bcell lymphoma/leukemia-2(Bcl-2)m RNA and protein were also significantly decreased in the liver and LYCF cells during 96 h and 48 h of hypoxia stress,respectively,whereas the expression level of Bcl-2 associated X(Bax)mRNA,Casp3 mRNA,and activity of caspase-3/7/9 were significantly increased,indicating that hypoxia induced caspase-dependent intrinsic apoptosis in L.crocea.The expression level of the apoptosis-inducing factor(AIF)protein was significantly increased in the liver and LYCF cells.The level of AIF protein was significantly decreased in the cytoplasm but increased in the nuclei of L.crocea,demonstrating that hypoxia induced the AIF-mediated caspase-independent intrinsic apoptosis.In addition,the activity of caspase-8 was significantly increased,indicating that hypoxia stress induced extrinsic apoptosis in L.crocea.Therefore,hypoxia induced apoptosis in L.crocea through both the intrinsic and extrinsic pathways.The present study accumulated basic biological information to help elucidate the mechanism of hypoxia response in marine fish.

Hif-1α/Hsf1/Hsp70 signaling pathway regulates redox homeostasis and apoptosis in large yellow croaker(Larimichthys crocea)under environmental hypoxia

Oxygen is an essential molecule for animal respiration,growth,and survival.Unlike in terrestrial environments,contamination and climate change have led to the frequent occurrence of hypoxia in aquatic environments,thus impacting aquatic animal survival.However,the adaptative mechanisms underlying fish responses to environmental hypoxia remain largely unknown.Here,we used large yellow croaker(Larimichthys crocea)and large yellow croaker fry(LYCF)cells to investigate the roles of the Hif-1α/Hsf1/Hsp70 signaling pathway in the regulation of cellular redox homeostasis,and apoptosis.We confirmed that hypoxia induced the expression of Hif-1α,Hsf1,and Hsp70 in vivo and in vitro.Genetic Hsp70 knockdown/overexpression indicated that Hsp70 was required for maintaining redox homeostasis and resisting oxidative stress in LYCF cells under hypoxic stress.Hsp70 inhibited caspase-dependent intrinsic apoptosis by maintaining normal mitochondrial membrane potential,enhancing Bcl-2 mRNA and protein expression,inhibiting Bax and caspase3 mRNA expression,and suppressing caspase-3 and caspase-9 activation.Hsp70 suppressed caspaseindependent intrinsic apoptosis by inhibiting nuclear translocation of apoptosis-inducing factor(AIF)and disturbed extrinsic apoptosis by inactivating caspase-8.Genetic knockdown/overexpression of Hif-1αand dual-luciferase reporter assay indicated that Hif-1αactivated the Hsf1 DNA promoter and enhanced Hsf1 mRNA transcription.Hsf1 enhanced Hsp70 mRNA transcription in a similar manner.In summary,the Hif-1α/Hsf1/Hsp70 signaling pathway plays an important role in regulating redox homeostasis and anti-apoptosis in L.crocea under hypoxic stress.

Scavenging reactive oxygen species is a potential strategy to protect Larimichthys crocea against environmental hypoxia by mitigating oxidative stress

The large yellow croaker(Larimichthys crocea),which is an economically important mariculture fish in China,is often exposed to environmental hypoxia.Reactive oxygen species(ROS)homeostasis is essential for the maintenance of normal physiological conditions in an organism.Direct evidence that environmental hypoxia leads to ROS overproduction is scarce in marine fish.Furthermore,the sources of ROS overproduction in marine fish under hypoxic stress are poorly known.In this study,we investigated the effects of hypoxia on redox homeostasis in L.crocea and the impact of impaired redox homeostasis on fish.We first confirmed that hypoxia drove ROS production mainly via the mitochondrial electron transport chain and NADPH oxidase complex pathways in L.crocea and its cell line(large yellow croaker fry(LYCF)cells).We subsequently detected a marked increase in the antioxidant systems of the fish.However,imbalance between the pro-oxidation and antioxidation systems ultimately led to excessive ROS and oxidative stress.Cell viability showed a remarkable decrease while oxidative indicators,such as malondialdehyde,proteincarbonylation,and8-hydroxy-2 deoxyguanosine,showed a significant increase after hypoxia,accompanied by tissue damage.Nacetylcysteine(NAC)reduced ROS levels,alleviated oxidative damage,and improved cell viability in vitro.Appropriate uptake of ROS scavengers(e.g.,NAC and elamipretide Szeto-Schiller-31)and inhibitors(e.g.,apocynin,diphenylene iodonium,and 5-hydroxydecanoate)may be effective at overcoming hypoxic toxicity.Our findings highlight previously unstudied strategies of hypoxic toxicity resistance in marine fish.

Population structure and genome‑wide evolutionary signatures reveal putative climate‑driven habitat change and local adaptation in the large yellow croaker

The large yellow croaker(Larimichthys crocea)is one of the most economically valuable marine fsh in China and is a notable species in ecological studies owing to a serious collapse of wild germplasm in the past few decades.The stock division and species distribution,which have important implications for ecological protection,germplasm recovery,and fshery resource management,have been debated since the 1960s.However,it is still uncertain even how many stocks exist in this species.To address this,we evaluated the fne-scale genetic structure of large yellow croaker populations distributed along the eastern and southern Chinese coastline based on 7.64 million SNP markers.Compared with the widely accepted stock boundaries proposed in the 1960s,our results revealed that a climate-driven habitat change probably occurred between the Naozhou(Nanhai)Stock and the Ming-Yuedong(Mindong)Stock.The boundary between these two stocks might have shifted northwards from the Pearl River Estuary to the northern area of the Taiwan Strait,accompanied by highly asymmetric introgression.In addition,we found divergent landscapes of natural selection between the stocks inhabiting northern and southern areas.The northern population exhibited highly agminated signatures of strong natural selection in genes related to developmental processes,whereas moderate and interspersed selective signatures were detected in many immune-related genes in the southern populations.These fndings establish the stock status and genome-wide evolutionary landscapes of large yellow croaker,providing a basis for conservation,fsheries management and further evolutionary biology studies.