Reproductive cycle of Ophiopholis mirabilis (Echinodermata: Ophiuroidea) in Zhangzi Island area, northern Yellow Sea

Ophiopholis mirabilis is a common species with a high population density on the western coasts of the northern Pacifi c Ocean.The number of O.mirabilis has been increasing recently in the scallop aquaculture zone(the Zhangzi Island area,northern Yellow Sea)in China.To explore the mechanism of its population variation,the reproductive cycle of O.mirabilis was investigated in this area(39°04′N;122°51′E)from February 2017 through January 2018 and determined by the monthly gonad index(GI),histological examinations of the gonads and the oocyte size-frequency distribution.O.mirabilis had a clear annual reproductive cycle that was synchronous between males and females.Sea temperature and food availability played important roles in O.mirabilis reproduction.The GI value was less reliable for determining reproductive activity in O.mirabilis because the nutritive tissues within the gonads may be utilized to synthesize gametes,leading to a decrease in GI during maturation.The histological results also show that abundant nutritive phagocytes were present in the gonads of O.mirabilis,which,together with the germ cells,aff ected the weight of the gonads.In addition,the mature oocytes of O.mirabilis were relatively small(75–150μm),indicating that the larval development was planktotrophic.This study provided insights into the reproductive patterns and biology of O.mirabilis and is an essential basis for the quantity control of this species in aquaculture areas.

Characterization of SHARPIN knockout Syrian hamsters developed using CRISPR/Cas9 system

Background : SHARPIN (SHANK- associated RH domain interactor) is a component ofthe linear ubiquitination complex that regulates the NF- κB signaling pathway. To betterunderstand the function of SHARPIN, we sought to establish a novel geneticallyengineered Syrian hamster with SHARPIN disruption using the CRISPR/Cas9 system.Methods : A single- guide ribonucleic acid targeting exon 1 of SHARPIN gene was designedand constructed. The zygotes generated by cytoplasmic injection of the Cas9/gRNA ribonucleoprotein were transferred into pseudopregnant hamsters. Neonatalmutants were identified by genotyping. SHARPIN protein expression was detectedusing Western blotting assay. Splenic, mesenteric lymph nodes (MLNs), and thymicweights were measured, and organ coefficients were calculated. Histopathologicalexamination of the spleen, liver, lung, small intestine, and esophagus was performedindependently by a pathologist. The expression of lymphocytic markers and cytokineswas evaluated using reverse transcriptase- quantitative polymerase chain reaction.Results : All the offspring harbored germline- transmitted SHARPIN mutations.Compared with wild- type hamsters, SHARPIN protein was undetectable in SHARPIN −/−hamsters. Spleen enlargement and splenic coefficient elevation were spotted inSHARPIN −/− hamsters, with the descent of MLNs and thymuses. Further, eosinophilinfiltration and structural alteration in spleens, livers, lungs, small intestines, and esophagiwere obvious after the deletion of SHARPIN. Notably, the expression of CD94 and CD22 was downregulated in the spleens of knockout (KO) animals. Nonetheless,the expression of CCR3, CCL11, Il4 , and Il13 was upregulated in the esophagi. Theexpression of NF- κB and phosphorylation of NF- κB and IκB protein significantly diminishedin SHARPIN −/− animals.Conclusions : A novel SHARPIN KO hamster was successfully established using theCRISPR/Cas9 system. Abnormal development of secondary lymphoid organs andeosinophil infiltration in multiple organs reveal its potential in delineating SHARPINfunction and chronic inflammation.

Changes in the population structure of Calanus sinicus during summer–autumn in the southern Yellow Sea

Calanus sinicus is a calanoid copepod widely distributed in coastal waters of China and Japan, and oversummering strategies may have major impacts on their population dynamics which in turn affect local marine food web structure. The abundance, stage composition, and sex composition of the planktonic copepod C. sinicus were studied from August to October 2002 in the southern Yellow Sea to understand how its population recovers from the over-summering state. Results showed that C. sinicus had low reproduction in August due to high temperature, except in waters near the Cheju Island with rich food and moderate bottom temperature, but the reproduction rates here decreased in September–October as food availability declined. When temperature dropped in September–October, C. sinicus actively propagated in coastal shallow waters. However, reproduction rates of C. sinicus individuals inhabiting the Yellow Sea Cold Water Mass(YSCWM) remained low during the three months of the study. The percentage of C. sinicus females was high during the reproductive period, which suggests that the sex composition of adult C. sinicus may reflect whether or not the population is in the reproductive mode.Numerous fifth copepodite stage(CV) C. sinicus aggregated in the YSCWM in a suspended developmental stage during the three months of this study, and they potentially served as the parental individuals for population development when conditions became optimal for reproduction later in the year.

Role of intraspecific competition in intrinsic growth rate regulation in an Oikopleura dioica(Tunicata)population

Planktonic Oikopleura dioica respond almost instantly to opportunistic algal blooms,but it is unknown whether the population increase can change from an exponential to a logistic model to avoid a final sudden collapse.To test the hypothesis that intraspecific competition regulates the intrinsic rate of natural increase(r),density-dependent effects on growth and reproduction performance were investigated in O.dioica via laboratory incubations.Over a large food concentration range,batch maturation was observed above the per capita food supply(PFS)of 8.1µgC/ind.in 4.5 d.Somatic growth was saturated beyond this PFS value,whereas gonad length increased continuously.Below this threshold,individuals reached small body and gonad lengths,and maturation was rarely observed during the incubation period.The gonad/body volume and maturation ratios also increased with the PFS.Instead of the food concentration,the r values were regulated by competition pressure via variability in maturation duration and the proportion of mature individuals in the cohorts.When the minimum food demand was satisfied in the designated generation time,the r value tended to be regulated by the spawning proportion in the population.Otherwise,prolonged development duration and decreased r values were expected.

Accelerated biogenic silica dissolution by marine invertebrate digestion:in comparison with phosphorus and iron

Herbivore digestion in aquatic ecosystems is usually considered a method of nutrient repackaging rather than recycling,as recalcitrant and low-level nutrients are presumed for their egesta.We hypothesize that this opinion holds only for nutrients recycled by excretion and egestion,not for those elements recycled overwhelmingly by fecal decomposition.In this study,we compared the dissolution of biogenic silica(BSi),phosphorus(P)and iron(Fe)between two food items and fecal pellets of two marine invertebrates fed on artificial seawaters free of bacteria.Relative to raw food materials,the mass proportion in fecal pellets of BSi increased,while that of P and Fe decreased.During the 21 days of incubation,the total dissolution rate of BSi was 13.9–36.0 times higher in fecal pellets than food items,followed by P(1.5–4.2 times)and Fe(1.1–2.4 times).While the dissolution of BSi and Fe occurred mostly in the first few days,P was mostly released in the last ten days.Regarding BSi dissolution,a higher rate was observed in oyster Crassostrea gigas than the Echiuran Urechis unicinctus,but no significant difference was found between fecal pellets in either species under naturally available diatom food(Phaeodactylum tricornutum)and introduced terrestrial food(rice husk powder),respectively.Our results show direct evidence of digestion-associated nutrients mobilization.BSi dissolution after animal digestion may be similarly efficient to that caused by bacteria colonization in natural seawater.

A simple and facile iodination method of didechlorotiacumicin B and aromatic compounds

Tiacumicin B(also known as fidaxomicin or difimicin)is a marketed 18-membered macrolide antibiotic for the treatment of Clostridium difficile infections.Tiacumicin B is structurally characterized with two chlorine atoms substituted on the aromatic ring,which is installed by the halogenase Tia M.During the study on halide compatibility of Tia M,a facile and nonenzymatic iodination method of didechlorotiacumicin B was discovered,requiring Na I,acid and air for iodination at room temperature.This method was also amenable to other 9 aromatic substrates with electron-rich sites for iodination.