Cenozoic Brittle Stars(Ophiuroidea) from the Hagjeon Formation and the Duho Formation,Pohang Basin,Korea

About 40 specimens of fossil ophiuroids were collected from two formations of the Cenozoic marine deposits,Duho Formation and Hagjeon Formation, Pohang Basin,Korea.A few specimens were three-dimensionally preserved:most of them were remained flattened and articulated.Although a gross morphology is well preserved in some specimens,the details such as disk shape and plates which are the most important diagnostic features were not observed.

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.

Morphological description and population structure of an ophiuroid species from cobalt-rich crust seamounts in the Northwest Pacific:Implications for marine protection under deep-sea mining

Many seamounts are covered with cobalt-rich ferromanganese crusts,and are increasingly attracting interest for the potential extraction of valuable mineral resources from deep seabed environments.However,the impacts of potential mining activities on the vulnerable seamount ecosystem remain unclear.To enhance the understanding of connectivity in benthic invertebrate populations in the Northwest Pacific,several seamounts were surveyed and biological samples collected.In the present study,the ophiuroid species Ophioplinthaca defensor is reported for the first time from four deep seamounts in the Northwest Pacific,and described,providing more detailed morphological diagnosis characters.To assess the population structure of the species between and within seamounts,two mitochondrial markers(COI and 16 S)were sequenced.In total,20 haplotypes from 32 COI sequences and 8 haplotypes from 3716 S sequences were recovered.The star-shaped TCS networks and nonsignificant pairwise population differences reveal the absence of distinct population structures between and within seamounts.In addition,the O.defensor population seemed to have undergone a demographic expansion in history.This is the first study on the genetic population structure of a benthic invertebrate from seamounts in the Northwest Pacific,and this results suggest a potentially high,long distance dispersal capacity in O.defensor between seamounts,which could inform the development of the Regional Environmental Management Plans for the cobalt-rich crust seamounts in the area.

Ophiuroid fauna of cobalt-rich crust seamounts in the Northwest Pacific Ocean

Seamounts are vulnerable ecosystems in the deep sea and can be heavily impacted by human activities,such as bottom fishing and deep-sea mining.The species composition and distribution patterns of benthic fauna is key information for the designation of marine protected areas and environmental management plans.Three contracts for cobalt-rich crust exploration have been granted to China,Japan and Korea in the Northwest Pacific Ocean by the International Seabed Authority.However,our knowledge of benthic biodiversity in this area is extremely insufficient.During 2013–2020,eight Chinese Ocean Mineral Resources R&D Association(COMRA)cruises were conducted to investigate the benthic assemblages of nine seamounts in this region.In this study,191 ophiuroids collected from seamounts in the Northwest Pacific were identified into 29 species in 11 families.Ophiacanthidae and Euryalidae were the two most dominant families with 12 and 6 species,respectively.Ophiotomidae and Ophiopyrgidae were represented by two species each,while seven families were represented by only one species.Four species were widely distributed among 4–5 seamounts,and 17 species were found only at a single site.An integrated regional taxonomic dataset of Ophiuroidea was generated and analyzed.A total of 23 and 14 species were obtained from the Magellan Seamount Chain(MSC)and the Marcus-Wake seamounts(MWS),respectively,with 8 species shared between the two seamount groups.The individual-based rarefaction curves did not reach an asymptote,suggesting that the sampling effort was inadequate for either the entire region or each single seamount.Most species distributed in a narrow depth range,and the species composition was different between water depths above and below 2000 m.Our results greatly improve the understanding of megafaunal biodiversity from seamounts in the Northwest Pacific Ocean,and highlight the necessity of further surveys to provide more robust information for environmental protection and management in this region.

蛇尾纲生物学研究进展

综述了国内外蛇尾纲生物学研究成果,包括形态特征、区系分布情况、遗传分化与行为生态学、活性物质开发研究及分子系统发生等研究进展;分析和总结蛇尾纲生物物种今后研究开展方向,以期为我国蛇尾纲各领域研究提供参考.

南海中部深海海山汁蛇尾属(Ophiurothamnus)二新记录种(蛇尾纲,棘蛇尾科)

通过对2018年4—5月在南海中部黄岩海山采集的蛇尾样品进行形态学分类研究,鉴定发现棘蛇尾科Ophiacanthidae汁蛇尾属Ophiurothamnus两个新记录种:(1)双环汁蛇尾Ophiurothamnus discycla(H.L.Clark,1911);(2)短简汁蛇尾Ophiurothamnus clausa(Lyman,1878)。本文分别对这两个新记录种的外部形态特征和内部骨骼进行了描述,并与相似种进行了分类学讨论。