Bioerosion on Late Pleistocene Marine Mollusks: A Paleoclimatological and Paleoecological Comparison of MIS 7 and MIS 5e with Modern Beaches (Río Negro, Argentina)

The Late Pleistocene littoral ridges of southern South America, especially those of the north of Argentinean Patagonia, contain remains of mollusk shells with bioerosion traces. Eleven sites from marine isotope stages (2 from MIS 7, 4 from MIS 5e) and five sites from modern beaches from northern Río Negro Province, with 40 taxa (17 bivalves and 23 gastropods) were analyzed, in the area between west of Baliza San Matías and Las Grutas (41°S). Three ichnogenera were identified in deposits of MIS 7: Entobia, Gastrochaenolites (Domichnia) and Oichnus (Praedichnia) with one ichnospecies (G. torpedo). Six ichnogenera were identified in deposits of MIS 5e: Entobia, Meandropolydora, Pinaceocladichnus, Iramena, Caulostrepsis and Oichnus with one ichnospecies (O. simplex). Seven ichnogenera were identified from modern beaches: Entobia, Meandropolydora, Iramena, Caulostrepsis, Pinaceocladichnus, Gastrochaenolites (Domichnia) and Oichnus (Praedicnia), with two ichnospecies (O. simplex and O. paraboloides). On this basis, it is inferred that Pleistocene benthic communities were constituted from cheilostome bryzoans and polychaete annelids, together with drilling bivalves, predatory gastropods and overall warm-water species of mollusks. Of these, Chama iudicai was found on Plicatula gibbosa from MIS 7 and MIS 5e. The record of warm temperature species suggests a higher sea surface temperature (SST) than the present one and/or the influence of the warm southward Brazilian Current affecting the waters of Golfo San Matías. On the modern beaches surveyed, there is an increase in polychaete annelids, cheilostome bryzoans, temperate-cold species and drilling bivalves, as well as sandy substrate species, which together with an increase of Gastrochaenolites and Caulostrepsis, suggest a colder climate due to the greater influence of the Malvinas Current during the Holocene.     

东营河口浅海贝类生态国家级海洋特别保护区大型底栖动物的群落结构特征

为了解东营河口浅海贝类生态国家级海洋特别保护区中大型底栖动物的群落结构及分布特征,于2019年对保护区内大型底栖动物进行了春、夏、秋、冬4个季度的详细调查,研究结果为:共采集大型底栖动物73种,优势种类为:彩虹明樱蛤(Moerellairidescens)、四角蛤蜊(Mactraveneriformis)、寡节甘吻沙蚕(Glycindegurjanovae)、三叶针尾涟虫(Diastylistricincta)、光滑河篮蛤(Potamocorbula laevis)、极地蚤钩虾(Pontocrates altamarimus)和马丁海稚虫(Spio martinensis)。大型底栖动物的年平均丰度为166 ind/m²,年平均生物量为14.30 g/m², Shannon-Wiener多样性指数(H′)平均值为2.14。聚类分析结果为调查区域的大型底栖动物分为两组群落(近岸区和远岸区),近岸区域形成以光滑河篮蛤和四角蛤蜊为主的群落,远岸区域形成以彩虹明樱蛤-寡节甘吻沙蚕为优势种类的群落,两者表现出不同的群落特征。ABC曲线分析表明,保护区内...     

AreAcila divaricata and Acila mirabilis One Species or Two Distinct Species？ Evidence from COI Mitochondrial DNA

Acila divaricata （Hinds, 1843） and A. mirabilis （Adams and Reeve, 1850） are common benthic bivalves in China. A number of researchers have proposed that the latter species is a junior synonym of the former species. Because of morphological similarities, it is difficult to distinguish these two species based on visual examination only. For better understanding of their taxon-omy, the mitochondrial CO1 gene fragments of five individuals of A. divaricata from the East China Sea and six individuals of A. mirabilis from the Yellow Sea were sequenced in this study. The phylogenetic relationships of the obtained COI sequences, together with nineteen sequences of three species of the genus Nucula, were analyzed. The pairwise intra- and inter-specific distances for the CO1 sequences ranged from 0.002 to 0.017 and from 0.128 to 0.134, respectively, and no overlap was found. Phylogenetically, A. divaricata and A. mirabilis form distinct clades and cluster into a sister to all other Nucula species. The results indicated that A. di-varicata and A. mirabilis are two distinct species. The differences in the morphology and distribution between the two species were briefly discussed.     

Are Acila divaricata and Acila mirabilis One Species or Two Distinct Species?Evidence from COI Mitochondrial DNA

Acila divaricata (Hinds, 1843) and A. mirabilis (Adams and Reeve, 1850) are common benthic bivalves in China. A number of researchers have proposed that the latter species is a junior synonym of the former species. Because of morphological similarities, it is difficult to distinguish these two species based on visual examination only. For better understanding of their taxonomy, the mitochondrial COI gene fragments of five individuals of A. divaricata from the East China Sea and six individuals of A. mirabilis from the Yellow Sea were sequenced in this study. The phylogenetic relationships of the obtained COI sequences, together with nineteen sequences of three species of the genus Nucula, were analyzed. The pairwise intra- and inter-specific distances for the COI sequences ranged from 0.002 to 0.017 and from 0.128 to 0.134, respectively, and no overlap was found. Phylogenetically, A. divaricata and A. mirabilis form distinct clades and cluster into a sister to all other Nucula species. The results indicated that A. divaricata and A. mirabilis are two distinct species. The differences in the morphology and distribution between the two species were briefly discussed.     

缢蛏属一新种

笔者对福建省闽江口、长乐市梅花镇海区滩涂的一种蛏进行研究，发现该种的壳长与壳高比、精子细胞形态、遗传基因（另做报道）等方面有别于缢蛏．新种的贝壳壳长与壳高比值较缢蛏大，生活水域的比重较缢蛏低．精子细胞核外缘呈瓣状，具8～9瓣，顶体长度约为缢蛏的1／3，为福建河口区缢蛏属一新种（软体动物门，双壳纲，灯塔蛤科），定名为近江蛏．     

中国南沙群岛的双壳纲贝类

报道了中国南沙群岛的双壳纲贝类141种,分隶于5亚纲8目36科77属.从种类的组成中,帘蛤科有18种,蚶科15种,扇贝科11种,鸟蛤科10种,锉蛤科8种,贻贝科、海菊蛤科和樱蛤科各7种,砗磲科6种,其他各科的种类均在5种以内.按种的性质而论,大多数属于和珊瑚礁有密切联系的热带种或亚热带种,区系性质为印度-西太平洋区的印尼-马来亚区.     

非海相双壳类江西蛤（Jiangxiella）首次发现于日本

首次报道日本西南部发现的晚三叠世非海相双壳类江西蛤（Jiangxiella)，并讨论这一发现的意义。认为原产于湘、赣、粤地区的江西蛤是地理分布极有限的土著属，它在日本西南部的发现表明当时该区与华南东部的古地理关系极为密切，可能原属同一地块。     

中国海域双壳类软体动物数据库的结构与功能

于１９９１－１９９５年，运用数据库管理系统调用地理信息系统，图象处理信息系统等计算机技术，将我国海域内已查明的１０００余种双壳类动物以数据库的形式进行管理，本数据库管理系统由查询，修改、统计、打印和绘图５个子系统构成，子系统之间以层次控制管理为主。为生物学研究和科学管理实现现代化进行探索。     

南海双带蛤科(Mesodes matidae)一新种

于１９５９年１２月１４日在南海进行的全国海洋综合调查时,采到了一个罕见的双壳类标本。最近经过鉴定,认为是一个新种,属于双带蛤科、糙双带蛤属,定名为中华糙双带蛤。模式标本保存于中国科学院海洋研究所。     

Shell growth history of geoduck clam (Panopea abrupta) in Parry Passage, British Columbia, Canada: Temporal variation in annuli and the Pacific Decadal Oscillation

An assemblage of geoduck clam shells from the marine environment of coastal British Columbia was studied. Shells were cut and the widths of internal shell growth increments, annuli, were measured from the hinge plate. The largest shells showed more than one hundred annual increments. Shell growth exhibited juvenile maxima at ontogenetic ages 3–6 years. The growth maximum was followed by a distinct decline that continued until the death of each individual. Further, this ontogenetic growth trend was mathematically removed from the data in order to examine growth variations other than ageing. The longest growth records from the oldest shells were compared to monthly indices of the Pacific Decadal Oscillation (PDO). It was found that the PDO exerts the strongest influence on the shell growth during the very start of the growing season, in February and March. We also detected increased magnitude of growth variations towards the end of the 20th century. Similar trends were apparent in the PDO record. Moreover, the shell specimen displaying the strongest trend of increasing variance had the strongest PDO-linked regional growth signal. Our results support the view that PDO exerts a governing influence on the biological and ecological system along Northeast Pacific coastal areas. Incorporation of geoduck shell growth increment analyses into multi-disciplinary studies dealing with palaeoceanography and archaeology is suggested as a promising future approach.