DNA barcodes for species identification of euphausiids (Euphausiacea, Crustacea)

Many species of euphausiids (Euphausiacea, Crustacea) are distinguishedby subtle or geographically variable morphological characters,and erroneous identification of euphausiid species may be morefrequent than currently acknowledged. DNA barcodes (short DNAsequences that discriminate species and aid in recognition ofunknown species) are of use for this group. A 650 bp regionof mitochondrial cytochrome oxidase I (mtCOI) was sequencedfor 40 species of 10 euphausiid genera: Bentheuphausia, Euphausia,Meganyctiphanes, Nematobrachion, Nematoscelis, Nyctiphanes,Stylocheiron, Tessarabrachion, Thyssanoessa and Thysanopoda.mtCOI sequence variation discriminated all species; pairwisedifferences averaged 16.4% (range 7–24%); mean generalizedtime reversible (GTR) genetic distance was 26.7%. mtCOI reliablyidentified euphausiid species: variation within species wastypically < 1% and GTR distance was typically < 2%. Atlanticand Pacific Ocean populations of Euphausia brevis differed by13% (GTR genetic distance = 28%) and may deserve status as distinctspecies. mtCOI gene trees were reconstructed for five generausing maximum parsimony, maximum likelihood and Bayesian algorithms;best-fit models of nucleotide evolution were determined foreach genus. The mtCOI gene tree for 20 species of Euphausiareproduced one of three morphologically defined species groups.mtCOI resolved relationships among closely related species ofmost genera, usually in accord with morphological groupings.A comprehensive DNA barcode database for euphausiids will helpensure accurate species identification, recognition of crypticspecies and evaluation of taxonomically meaningful geographicvariation.     

The gastric mill of euphausiid crustaceans: a comparison of eleven species

The morphology of the gastric mill of 11 species in the family Euphausiidae is described. Two distinct arrangements can be recognized with respect to presence or absence of lateral teeth. One is the well-developed gastric mill of Thsanoessa gregaria, T. inermis, T. macrura and Pseudeuphausia sinica; the other is the gastric mill without lateral teeth of Nematoscelis atlantica, N. difficilis, N. megalops, Nematobrachion flexipes, N. sexspinosum, Stylocheiron abbreviatum, and S. carinatum. This supports the close relationships of the four species of both genera, Thysanoessa and Pseudeuphausia on the one hand and seven species belonging to Nematobrachion, Nematoscelis, and Stylocheiron on the other hand. The hypothesis that species in the same genus have similar gastric mill morphology, which was once rejected in the genus Thysanopoda, is accepted in all five genera examined here. Functional morphology of euphausiid foreguts is discussed.     

Vertical distribution and feeding pattern of Euphausiacea (Crustacea) in the eastern Banda Sea (Indonesia) during the SE and NW monsoons

The vertical distribution of Euphausiacea (Crustacea) in theeastern Banda Sea (Indonesia) during the SE and NW monsoon seasonswas studied. In August 1984 and February/ March 1985, stratifiedday and night sampling was carried out between 0 and 500 m atfour stations. A total of 31 species was found, of which mostwere present in both monsoon seasons. Species with a high presencein samples and performing diurnal vertical migration in bothmonsoon seasons were Euphausia diomedeae, Euphausia pseudogibba,Thysanopoda monacantha, Thysanopoda iricus-pidaia and Nematoscelismicrops. Species with a high presence in samples showing nodiurnal vertical migration in both monsoon seasons were Euphausiasimilis, Nematobrachion boopis. Nematoscelis tenella, Stylocheironmaximum and Thysanopoda orientalis. The density of Euphausiaceaat the sampled stations was higher, but more heterogeneous,in the nutrient-enriched SE monsoon period than in the relativelynutrient-poor NW monsoon season, when densities were lower andmore similar. The vertical distributions and diurnal verticalmigration of species did not show a unanimous and strong responseto seasonal hydrographic differences. The day–night depthdistribution pattern of the Euphausiacea population in the upper500 m is largely the same in both seasons, with comparable migrationranges. Some species showed a somewhat upward shifted depthdistribution in the nutrient-enriched period. For mesopelagicand bathypelagic species especially, food resources were thenfavourable in the upper layers, as indicated by rare recordsof Thysanopoda crisiata. Analyses of stomach contents snowedmainly a nocturnal feeding pattern for the diurnal verticalmigrating species and a continuous feeding pattern for the non-migratingspecies.     

First observation of krill spawning in the high Arctic Kongsfjorden, west Spitsbergen

In the past, two euphausiid species prevailed in the high Arctic Kongsfjorden, the arcto-boreal Thysanoessa inermis (Kroeyer, 1846) and Thysanoessa raschii (Sars. 1964). Both were considered expatriates from the Barents Sea or Norwegian Sea and non-reproductive due to low temperatures. The macro-zooplankton of the fjord has been studied as a component in an ecosystem context since 2006, including baseline investigation of distribution and functional performance of key species. In recent years, three additional krill species were regularly detected in the fjord and are the focus of an intensive long-term study. Of these species, Thysanoessa longicaudata (Kroeyer, 1846) and Meganyctiphanes norvegica (Sars, 1857) are typical for the boreal Atlantic whereas Nematoscelis megalops (Sars, 1883) has a broad distribution in temperate to subtropical provinces. Their occurrence in the Kongsfjorden clearly indicates increasing Atlantic influence. During the 2011 campaign, T. raschii was observed spawning in the field for the first time and showed development up to the naupliar stage in the laboratory. Should more evidence of reproduction be encountered in any of the five krill species in the Kongsfjorden in the future, it will be taken as an indication of a changing environment concerning temperature and food web composition.     

Gymnodinioides pacifica, n. sp., an exuviotrophic ciliated protozoan (Ciliophora, Apostomatida) from euphausiids of the Northeastern Pacific

A new species of apostome ciliate, Gymnodinioides pacifica n. sp. from the euphausiid Euphausia pacifica is described. The ciliated protozoan encysts on the setae of the appendages, telson and antennae. It excysts and enters the exoskeleton of the host after moulting, where it feeds on exuvial fluid. The phoront and trophont stages of this ciliate are described. The ciliature of the trophont has the following characteristics that distinguish it from the other species of Gymnodinioides: (1) a short kinety 9a (ciliary row 9a or K9a), approximately half of the length of falciform field 8, that extends from the anterior end of the cell posteriorly to the level of K1, (2) a straight K5a, perpendicular to K5b, K6, and K7, and (3) two distinct bands of kineties, K9b-K5b and K4-K1. In addition to those on the host E. pacifica, phoront cysts of similar shape were observed on Thysanoessa spinifera, T. gregaria, T. inspinata, T. longipes, and Nematoscelis difficilis. High prevalence rates were recorded (83%) for these apostome cysts on E. pacifica and T. spinifera during summer collections from the Oregon and Washington coasts. Additionally, we report other apostome ciliate symbionts of euphausiids, including Phtorophrya sp., which preys on apostomes in the genus Gymnodinioides.     

The diet of the Southern rockhopper penguin Eudyptes chrysocome chrysocome at Beauchene Island, Falkland Islands

The diet of the Southern rockhopper penguin at Beauchene Island, Falkland Islands, was studied in the early chick-rearing period by quantitative analysis of adult stomach contents. Juvenile squid (Teuthowenia sp.) comprised on average 21% by numbers (c. 1000 per sample) and 53% by weight; crustaceans contributed 79% by numbers (c. 4000 per sample) but only 45% by weight, and fish 2% by weight. Of the crustaceans only the euphausids Euphausia lucens (66% by numbers), E. vallentini (19%) and Thysanoessa gregaria (15%) were present in significant quantities, and all are swarming species characteristic of the Patagonian shelf epipelagic zooplankton. Comparison is made with the limited dietary data available from other studies, and rockhopper penguins are suggested typically to feed opportunistically on swarming or shoaling zooplankton (particularly euphausids and young squid) and small fish. Whereas the average weight of the stomach contents was 220 g, the biomass of the individuals originally ingested was estimated to total 800 g; the c. 3000 kj this represents is consistent with the likely energy requirements of adults making daily foraging trips to rear small chicks.     

Ecological investigations on the zooplankton community in Balsfjorden,Northern Norway: seasonal changes in the lipid class composition of Meganyctiphanes norvegica (M. Sars), Thysanoessa raschii (M. Sars), and T. inermis (Krøyer)

The lipid class composition of three krill species, Meganyctiphanes norvegica (M. Sars), Thysanoessa raschii (M. Sars), and T. inermis (Krøyer), was determined throughout the year in Balsfjorden, Northern Norway. Meganyctiphanes norvegica had triglycerides as its major neutral lipid, Thysanoessa raschii had mainly triglycerides with small amounts of wax esters, whereas T. inermis had mainly wax esters with lesser amounts of triglycerides. Neutral lipids were generally accumulated by the krill during spring-early summer, maintained at high levels through to mid-winter and then declined to minimal levels during early spring. Differences in rates of deposition and mobilization of neutral lipid between males and females occurred in Meganyctiphanes norvegica and Thysanoessa raschii but not in T. inermis. T. raschii accumulated lipid somewhat later in the year than T. inermis but earlier than Meganyctiphanes norvegica. A major rôle for lipid in the elaboration of gonads is indicated. The accumulation of either wax esters or triglycerides by euphausiids is considered in terms of the feeding habits and ecological niche differentiation of the species.     

南麂列岛海洋保护区浮游动物调查

主要研究南麂列岛海洋保护区浮游动物种类组成、数量分布、多样性指数、浮游动物与浮游植物动态变化及浮游动物数量变化与营养盐的关系。经鉴定共发现,浮游动物98种,主要有2个生态类群:(1)暖温带近海类群,优势种有中华哲水蚤(Calanus sinicus)、中华假磷虾(Pseudeuphausia sinicas)、五角水母(Muggiaea atlantica)、百陶箭虫(Sagitta bedoti)、拿卡箭虫(S.nagae)等;(2)暖水性外海类群,代表性种类有肥胖箭虫(S.enflata)、精致真刺水蚤(Euchaeta concinna)等。结果表明,8月份南麂列岛浮游动物生物量和丰度出现最高值,9、10月份逐渐减少,多样性指数变化范围1.78~4.38,平均3.99;保护区内浮游动物数量与浮游植物细胞密度呈良好的正相关关系,与氮含量呈负相关关系。     

Lipid composition and trophic relationships of krill species in a high Arctic fjord

Our study deals with the lipid biochemistry of the krill community in the ecosystem of the high Arctic Kongsfjord (Svalbard). During the last decades, Kongsfjord experienced a change in krill species composition due to recent increased advection of Atlantic water masses carrying characteristic boreal as well as subtropical-boreal euphausiids into the ecosystem. The lipid biochemistry and trophic relationships of the species recently inhabiting the Arctic water masses are scarcely known, although a change in a krill population may have a significant impact on the ecosystem. A comparison of nutrition and energy storage strategies, stable isotopes, lipid profiles and fatty acid compositions showed remarkable differences between the krill species. These reflected the diverse feeding behaviours and specific adaptations to the environments of their origin: the boreal Meganyctiphanes norvegica and subtropical Nematoscelis megalops appear more carnivorous and have significantly lower mean lipid contents (29 and 10 %, respectively) and a different energy storage pattern (triacylglycerols and polar lipids, respectively) than the arcto-boreal Thysanoessa inermis, which consists of up to 54 % of lipids mainly stored as wax esters (>40 %). These differences may have significant implications for the rapidly changing marine food web of Kongsfjord—especially for higher trophic levels relying on the nutritional input of animal lipids.     

Feeding behaviour in Meganyctiphanes norvegica (M. Sars) (Crustacea: Euphausiacea)

Meganyctiphanes norvegica (M. Sars) will feed upon the centric diatom Thalassiosira weissflogii (Grunow) G. Fryxell & Hasle but cannot fulfil its energy requirement for metabolism on this food. Its daily metabolic requirement can be exceeded when the euphausiid feeds upon the copepods Calanus finmarchicus Gunner or Centropages typicus Krøeyer, but not when feeding upon the smaller copepods Pseudocalanus spp. or Acartia spp. When feeding upon a natural copepod assemblage Meganyctiphanes norvegica requires high concentrations of copepods to achieve its metabolic requirements, suggesting that the euphausiid may exploit vertically patchy concentrations of prey. Short-term predation rates on Pseudocalanus spp. were also used to estimate feeding rates. Feeding in Meganyctiphanes norvegica appears to be adapted to a spatially variable food supply and rapid exploitation of food sources concentrated into patches or layers. The filter area of the feeding basket of M. norvegica is proportionally smaller than the filter area of Euphausia superba Dana, but has the same allometric length exponent. The filter area probably reflects the difference between the primarily carnivorous diet of Meganyctiphanes norvegica and herbivorous diet of Euphausia superba.     

Pseudocollinia brintoni gen. nov., sp. nov. (Apostomatida: Colliniidae), a parasitoid ciliate infecting the euphausiid Nyctiphanes simplex

A novel parasitoid ciliate, Pseudocollinia brintoni gen. nov., sp. nov. was discovered infecting the subtropical sac-spawning euphausiid Nyctiphanes simplex off both coasts of the Baja California peninsula, Mexico. We used microscopic, and genetic information to describe this species throughout most of its life cycle. Pseudocollinia is distinguished from other Colliniidae genera because it exclusively infects euphausiids, has a polymorphic life cycle, and has a small cone-shaped oral cavity whose left wall has a field of ciliated kinetosomes and whose opening is surrounded on the left and right by 2 'oral' kineties (or ciliary rows) that terminate at its anterior border. Two related species that infect different euphausiid species from higher latitudes in the northeastern Pacific Ocean, Collinia beringensis Capriulo and Small, 1986, briefly redescribed herein, and Collinia oregonensis Gómez-Gutiérrez, Peterson, and Morado, 2006, are transferred to the genus Pseudocollinia. P. brintoni has between 12 and 18 somatic kineties, and its oral cavity has only 2 oral kineties, while P. beringensis comb. nov. has more somatic kineties, including 3 oral kineties. P. oregonensis comb. nov. has an intermediate number of somatic kineties. P. beringensis comb. nov. also infects Thysanoessa raschi (a new host species). SSU rRNA and cox1 gene sequences demonstrated that Pseudocollinia ciliates are apostome ciliates and that P. brintoni is different from P. beringensis comb. nov. High densities of rod-shaped bacteria (1.7 μm length, 0.2 to 0.5 μm diameter) were associated with P. brintoni. After euphausiid rupture, high concentrations of P. brintoni and bacteria cluster to form 3 to 6 cm long filaments where tomites encyst and transform to the phoront stage; this is a novel place for encystation. P. brintoni may complete its life cycle when the euphausiids feed on these filaments.     

Seasonal dynamics and grazing rate of zooplankton in Yueqing Bay,China

The species composition,biomass,abundance,and species diversity of zooplankton were determined for samples collected from August 2002 to May 2003 from 14 stations in Yueqing Bay,China.Phytoplankton growth rate and microzooplankton grazing rate were obtained by using the dilution method developed by Landry and Hassett.The spatial and temporal variations of zooplankton and its relationship with environmental factors were also analyzed.The results showed that the zooplankton in the Yueqing Bay could be divided into four ecotypes,namely coastal low saline species,estuary brackish water species,offshore warm water species,and eurytopic species.A total of 75 species of zooplankton belonging to 56 genera and 17 groups of pelagic larva were identified in the Yueqing Bay.The coastal low saline species was the dominant ecotype in the study area,and the dominant species were Labidocera euchaeta,Acartia pacifica,Acrocalanus gibber,Pseudeuphausia sinica,and Sagitta bedoti among others.There was considerable seasonal variation in zooplankton biomass and abundance in the surveyed areas.The peak biomass appeared in August,descending in November and in May,and the lowest biomass appeared in February.Similarly,the highest abundance of zooplankton was observed in August,with the abundance descending in the following months:May,November,and February.There were similar horizontal distribution patterns for the biomass and the abundance of zooplankton.They both increased from the upper to the lower bay in February and May,but decreased from the upper to the lower bay in August.Biomass and abundance were evenly distributed in the Yueqing Bay in November.Moreover,there was marked seasonal variation in the species diversity of zooplankton,which conformed to the abundance of zooplankton.Results of the dilution experiments indicated that there was grazing pressure of microzooplankton on phytoplankton in the Yueqing Bay throughout the year though the rate of microzooplankton grazing on phytoplankton varied seasonally.Phytoplanktons were growing at 0.26-2.07/d and grazed by microzooplankton at a rate of 0.15--0.48/d in different seasons.     

Distribution patterns of pelagic euphausiids in the East China Sea

Distribution patterns and abundance of the euphausiids were examined in the East China Sea (23°30′ –33°00′N, 118°30′ –128°00′ E) in relation to temperature and salinity. The data were collected in 4 surveys from 1997 to 2000. The density or yield density model was used to predict optimum temperature and salinity of water for euphausiid distribution, and thereafter distribution patterns of euphausiids were determined based on the predicted parameters. Of 23 species, Euphausia pacifica, E. nana, Pseudeuphausia sinica and P. latifrons were numerically dominant. The analyses indicate that Euphausia pacifica is an offshore temperate water species, E. nana is an offshore temperate warm water species, P. sinica is a coastal subtropical water species and P. latifrons is an oceanic tropical water species. The 4 species occupied 4 different water masses, respectively, namely, cold water mass, cold and warm water mixed masses in winter and spring, cold and warm water mixed masses in summer and autumn, and warm water mass, which could be the good designators of individual water masses, respectively. The predicated optimal temperatures for E. tenera, S. carinatum, E. diomedeae, Stylocheiron affine, Nematoscelis sp., N. gracilis, N. atlantica, Stylocheiron sp. and S. suhmii are all > 25°. These species are mainly distributed in southern Kuroshio in winter and spring, Kuroshio, the Taiwan Warm Current and Tsushima Current in summer and autumn, the equatorial waters of Pacific Ocean and the eastern waters of the Taiwan Strait. They are called as oceanic tropical water species. Nematoscelis tenella and T. tricuspidata are referred to as offshore subtropical water species according to their geographic distributions even if they are halobionts. Euphausia sanzoi is considered as a typical offshore subtropical water species, which inhabited waters below 25°. Stylocheiron microphthalma, occupying warm current waters where temperature and salinity are nearly 25° and 34 in summer and autumn, belongs to oceanic tropical water species. In the same way, E. similes, E. mutica, Euphausia sp., E. brevis and E. recurva are classified into offshore subtropical water species in accordance with the optimum temperature and salinity of waters as well as locations and seasons of their occurrence. Optimum temperature, rather than salinity, is a better parameter in determining the distribution patterns of euphausiids.     

The diet of blue whiting, hake, horse mackerel and mackerel off Portugal

This paper deals with the diets of blue whiting Micromesistius poutassou (Risso 1810), hake Merluccius merluccius (L. 1758), horse mackerel Trachurus trachurus (L. 1758), and mackerel Scomber scombrus (L. 1758) off Portugal and explores variations in fish length, water depth, latitude and season. All four species feed on fish; however, hake and mackerel are the first and second most important predators, respectively, blue whiting being the most important fish prey for both species. The diets of blue whiting and horse mackerel are composed mainly of crustaceans. Diet variations according to predator fish size are more important than either latitude or depth. In the diets of blue whiting, hake and horse mackerel, prey importance increases with predator size. For blue whiting and horse mackerel, diet variations with fish length and water depth are correlated: small fish are closely associated with coastal areas where they feed on copepods and decapod larvae. Seasonality in the diet is apparent for blue whiting, hake and mackerel. For blue whiting, the decapod Pasiphaea sivado is the most important prey in summer and autumn, being replaced by the euphausid Meganyctiphanes norvegica in winter. In the diet of hake, seasonality was characterised by the major importance of Macroramphosus scolopax in autumn, whereas the diet of mackerel consisted of zooplankton in summer, fish and decapods in autumn and decapod larvae in winter. Seasonal changes in the diet of horse mackerel correspond to a higher diversity of prey in autumn compared to other seasons (although euphausids are the main prey in all seasons). Seasonality in feeding activity is not as marked for the other species as it is for horse mackerel; the percentage of empty stomachs of horse mackerel is greatest in winter, when spawning takes place at the Portuguese coast.     

Verbreitung von Makrozooplankton in der Grönlandsee im Spätherbst 1988 (Crustacea: Ostracoda, Hyperiidea [Amphipoda], Euphausiacea)

The horizontal and vertical distribution and the abundance of ostracods, hyperiids (amphipods) and euphausiids in the Greenland Sea along a transect parallel 74°45′N (from 15°45′E to 08°30′W) are described. The samples were taken by RV “Meteor” in late autumn of 1988. 8 species of the above named groups have been recorded in two different water masses which were touched by the transect. 5 stations were situated in the realm of the Atlantic waters of the Spitsbergen Current. HereDiscoconchoecia elegans, Meganyctiphanes norvegica, andThemisto compressa are indicators for the southern Atlantic water. 6 stations belong to the Arctic area dominated by Arctic Surface Water, whereBoroecia borealis, Themisto abyssorum, Thysanoessa longicaudata, andThysanoessa inermis are quite abundant as borealsubarctic species, whereasThemisto libellula is a true species of pure Arctic water.

---

---

Mitarbeiterin der Taxonomischen Arbeitsgruppe an der Biologischen Anstalt Helgoland     

三门湾浮游动物的季节变动及微型浮游动物摄食影响

2002年8月、11月、2003年2月和5月,在三门湾进行了4个航次生物、化学和水文等专业综合调查。根据采集的浮游动物样品的分析鉴定及海上现场实验结果,对浮游动物的群落组成、生物量、丰度、多样性指数的分布和季节变动及其浮游动物对浮游植物的摄食影响进行研究。结果表明,三门湾浮游动物有67属,89种,16类浮游幼体,主要可划分为4个生态类群：以近岸低盐类群为主,其优势种为中华哲水蚤Calanus sinicus、真刺唇角水蚤Labidocera etwhaeta、捷氏歪水蚤Tortanus derjugini、太平洋纺锤水蚤Acartiapacifica、中华假磷虾Pseudeuphausia sinica和百陶箭虫Sagitta bedoti等。半咸水河口类群、暖水性外海类群和广布种相对较少。浮游动物生物量和丰度的平面分布趋势除了夏季有所差异外,其它季节基本一致。2月份和5月份,浮游动物生物量和丰度,从湾顶向湾口呈逐渐增加趋势;8月份,湾口区生物量最高,而丰度高值区出现在湾顶部;11月份,生物量和丰度的平面分布相对均匀。浮游动物种类多样性指数有明显的季节变化,其动态变化与浮游动物种数和丰度的变化一致。微型浮游动物对浮游植物存在摄食压力,且有季节变化,摄食率的变化在0．18．0．68d^-1,微型浮游动物的摄食率低于相同季节的浮游植物生长率。微型浮游动物对浮游植物摄食压力的变化范围为16．1％-49．1％d^-1,对初级生产力摄食压力的变化在58．3％-83．6％d^-1。11月份,微型浮游动物对浮游植物和初级生产力的摄食压力均出现最高值。     

Distribution and reproduction strategies of krill (Euphausiacea) on the Norwegian shelf

Meganyctiphanes norvegica and Thysanoessa inermis were the dominant krill species that were observed on the Norwegian shelf. T. inermis and M. norvegica were found in abundances of up to 14 and 22 no. m^?2, respectively, on the mid Norwegian shelf (Møre plateau, Halten, Sklinna, Træna banks) and up to the Lofoten area. The main distribution of the krill indicates that they are mostly restricted to the Atlantic waters of the shelf region in April and little krill was observed south of 62°N. The two dominant krill species appeared to have different strategies for the timing of spawning, thus avoiding direct overlap of spawning products. The majority of the T. inermis females were in the spawning condition in April. Meganyctiphanes norvegica appeared to spawn at least a month later. The sizes of the first time spawners of T. inermis were around 11–16 mm, and they were approximately 1 year old. The sizes of the second time spawners were around 17–22 mm. The spawning of krill on the Norwegian shelf coincides with the blooming of the spring phytoplankton in this region . Advection of eggs and larvae of krill, as well as other plankton, is important not only to the shelf and slope region, but also for the functioning of the wider Norwegian Sea ecosystem and the adjacent areas.     

Two new species of Pseudogymnoascus with Geomyces anamorphs and their phylogenetic relationship with Gymnostellatospora

Two new psychrophilic Pseudogymnoascus species with Geomyces anamorphs are described from a Sphagnum bog in Alberta, Canada. Pseudogymnoascus appendiculatus has long, branched, orange appendages and smooth, fusoid to ellipsoidal ascospores with a faint longitudinal rim. Pseudogymnoascus verrucosus has short, subhyaline appendages and warty peridial hyphae and ascospores, and both smooth to asperulate and irregularly warty conidia. Both species produce asci in chains, a feature that supports the distinction between this group and Myxotrichum, which produces asci singly. The discovery of species intermediate between Pseudogymnoascus and Gymnostellatospora, in having both ornamented ascospores and Geomyces anamorphs, prompted a re-evaluation of the genera. Sequence analysis of the internal transcribed spacer regions (ITS) of the nuclear ribosomal DNA indicates that the two genera remain distinct and comprise a monophyletic group. Pseudogymnoascus species have smooth to warty or lobate-reticulate ascospores while species of Gymnostellatospora have walnut-shaped spores with distinct longitudinal crests and striations. Anamorphs assignable to the form genus Geomyces are allied with both genera. A key is provided to the four species and varieties of Pseudogymnoascus.     

The diel migrations and vertical distributions of zooplankton and micronekton in the Northwestern Mediterranean Sea. 1. Euphausiids, mysids, decapods and fishes

Vertical distributions and diel migrations of the main speciesof micronekton, four euphausiids, one mysid, one decapod andthree fishes, were described in detail in the 0–1000 mwater column on a fixed station in the Northwestern MediterraneanSea. The euphausiids Euphausia krohni and Thysanopoda aequalis,the decapod Gennadas elegans and, to a lesser extent, the fishArgyropelecus hemigymnus were shown to perform clear diel verticalmigrations. Results of horizontal hauls at a given depth aroundsunrise and sunset showed a marked diurnal symmetry of the migratorycycles, particularly for E.krohni, T.aequalis and G.elegans.The behaviour of the euphausiid Nematoscelis megalops was morecomplex: it presented a repetitive bimodal day distributionand only part of its population migrated. As very weak or non-migratorswe found the euphausiid Stylocheiron longicorne and the bathypelagicmysid Eucopia unguiculata, for which migration concerned onlysome of the older individuals. The fishes Cyclothone braueriand Cyclothone pygmaea appeared to be non-migrants. As depthincreased, C.braueri was replaced by C.pygmaea, with maximumconcentrations at 350–550 and 550–700 m depth, respectively.     

Seasonal dynamics and grazing rate of zooplankton in Yueqing Bay, China

The species composition, biomass, abundance, and species diversity of zooplankton were determined for samples collected from August 2002 to May 2003 from 14 stations in Yueqing Bay, China. Phytoplankton growth rate and microzooplankton grazing rate were obtained by using the dilution method developed by Landry and Hassett. The spatial and temporal variations of zooplankton and its relationship with environmental factors were also analyzed. The results showed that the zooplankton in the Yueqing Bay could be divided into four ecotypes, namely coastal low saline species, estuary brackish water species, offshore warm water species, and eurytopic species. A total of 75 species of zooplankton belonging to 56 genera and 17 groups of pelagic larva were identified in the Yueqing Bay. The coastal low saline species was the dominant ecotype in the study area, and the dominant species were Labidocera euchaeta, Acartia pacifica, Acrocalanus gibber, Pseudeuphausia sinica, and Sagitta bedoti among others. There was considerable seasonal variation in zooplankton biomass and abundance in the surveyed areas. The peak biomass appeared in August, descending in November and in May, and the lowest biomass appeared in February. Similarly, the highest abundance of zooplankton was observed in August, with the abundance descending in the following months: May, November, and February. There were similar horizontal distribution patterns for the biomass and the abundance of zooplankton. They both increased from the upper to the lower bay in February and May, but decreased from the upper to the lower bay in August. Biomass and abundance were evenly distributed in the Yueqing Bay in November. Moreover, there was marked seasonal variation in the species diversity of zooplankton, which conformed to the abundance of zooplankton. Results of the dilution experiments indicated that there was grazing pressure of microzooplankton on phytoplankton in the Yueqing Bay throughout the year though the rate of microzooplankton grazing on phytoplankton varied seasonally. Phytoplanktons were growing at 0.26–2.07/d and grazed by microzooplankton at a rate of 0.15–0.48/d in different seasons. __________ Translated from Acta Ecologica Sinica, 2005, 25(8): 1853–1862 [译自: 生态学报, 2005, 25(8): 1853–1862]