Patterns of diversity of the north-eastern Atlantic blenniid fish fauna (Pisces: Blenniidae)

This paper presents an analysis of the distributional patterns of blenniids (Pisces: Blenniidae) in the north‐eastern Atlantic. Two peaks of species diversity were found, both in terms of number of species and number of endemics: one in the tropical African coast and another in the Mediterranean Sea. A cluster analysis of similarity values (Jaccard coefficient) among the eastern Atlantic zoogeographical areas, revealed the following groups: a north temperate group, a tropical group formed by the tropical African coast and Mauritania, another group formed by the islands of Cape Verde, a south temperate group (South Africa), and a southern Atlantic group formed by the islands of Ascension and St Helena. Within the north temperate group, the subgroups with higher similarities were: Azores and Madeira, Canary Islands and Morocco, and the Mediterranean and the Atlantic coast of the Iberian Peninsula. Based on affinity indices, the probable directions of faunal flows were inferred. The tropical coast of Africa and the Mediterranean emerged from this analysis as probable speciation centres of the north‐eastern Atlantic blenniid fauna. The Mediterranean may have also acted as a refuge during glacial periods.     

Geographic variation in reef-fish assemblages along the Brazilian coast

The species composition of reef‐fish assemblages from nine Brazilian major coastal sites and four oceanic islands are compared. Canonical correspondence analysis (CCA) was utilized to identify groups of sites based on similarity of composition, and to correlate environmental trends with such groups. Five distinct groups of sites were recognized: (1) the South and South‐eastern coastal reefs (from Guarapari Islands to Santa Catarina, the southernmost Brazilian reefs); (2) the North‐eastern coast (extending from the Manuel Luis Reefs to Abrolhos Archipelago); (3) Trindade Island; (4) Fernando de Noronha and Atol das Rocas; and (5) St Paul’s Rocks. Water temperature, coral richness, distance from mainland, primary production and shelf width strongly correlated with the diversity and composition of the reef sites.     

Thalassomonhystera traesti n.sp., Eumonhystera andrassyi and three Monhystrella species (Monhysteridae: Nematoda) from Li River, China

A new Thalassomonhystera species, i.e. T. traesti n.sp., and a new subspecies, Monhystrella lepidura chinensis n. subsp., together with Eumonhystera andrassyi (Biró, 1969) Andrássy, 1981, Monhystrella macrura (de Man, 1880) Andrássy, 1981 and Monhystrella iranica Schiemer, 1965 are described from Li River at Guiling, China. Thalassomonhystera traesti n.sp. is characterised by a combination of the following characters: expanded lip region, large and anteriorly situated amphids, prominent inner labial sensilla, and slender spicules and tube-like gubernaculum in males. Monhystrella lepidura chinensis n. subsp. belongs to Monhystrella lepidura (Andrássy, 1963) Andrássy, 1968 but differs from the three hitherto described subspecies in its possession of a pharynx that posteriorly expands into a double bulb. Monhystrella macrura, M. iranica and Eumonhystera andrassyiare reported here for the first time from China.     

On the marine sister groups of the freshwater crabs (Crustacea: Decapoda: Brachyura)

Freshwater crab sister group relationships with marine eubrachyuran families were investigated. A morphology-based cladistic analysis was conducted on representatives of the freshwater crab families Deckeniidae, Gecarcinucidae, Parathelphusidae, Potamidae, Potamonautidae, Pseudothelphusidae, and Trichodactylidae using a disparate assemblage of marine heterotreme and thoracotreme brachyurans as possible sister groups. The monophyly of the freshwater crabs sensu lato is falsified. The family Trichodactylidae and the marine portunid subfamily Carcininae form basal groups within the superfamily Portunoidea. The monophyly of the Pseudothelphusidae and the Paleotropical freshwater crab families is supported, and this clade is the sister group of the Thoracotremata (Gecarcinidae, Grapsidae s.l., and Ocypodoidea). The origin, groundplan, and diversification of freshwater crabs are discussed in the context of previously published scenarios of their evolution.     

Coherent dynamics and association networks among lake bacterioplankton taxa

Bacteria have important roles in freshwater food webs and in the cycling of elements in the ecosystem. Yet specific ecological features of individual phylogenetic groups and interactions among these are largely unknown. We used 454 pyrosequencing of 16S rRNA genes to study associations of different bacterioplankton groups to environmental characteristics and their co-occurrence patterns over an annual cycle in a dimictic lake. Clear seasonal succession of the bacterioplankton community was observed. After binning of sequences into previously described and highly resolved phylogenetic groups (tribes), their temporal dynamics revealed extensive synchrony and associations with seasonal events such as ice coverage, ice-off, mixing and phytoplankton blooms. Coupling between closely and distantly related tribes was resolved by time-dependent rank correlations, suggesting ecological coherence that was often dependent on taxonomic relatedness. Association networks with the abundant freshwater Actinobacteria and Proteobacteria in focus revealed complex interdependencies within bacterioplankton communities and contrasting linkages to environmental conditions. Accordingly, unique ecological features can be inferred for each tribe and reveal the natural history of abundant cultured and uncultured freshwater bacteria.     

Fish community structure and environmental correlates in the highly altered southern Sacramento-San Joaquin Delta

We sampled 11 sites in the southern Sacramento-San Joaquin Delta from 1992–1999, to characterize fish communities and their associations with environmental variables. Riparian habitats were dominated by rock-reinforced levees, and large water diversion facilities greatly influenced local hydrodynamics and water quality. We captured 33 different taxa, only eight of which were native. None of the native species represented more than 0.5% of the total number of individuals collected. The abundance of native species was consistently low but typically peaked during high outflow periods. Fish communities were predominantly structured along environmental gradients of water temperature and river flow. Native species (tule perch, Hysterocarpus traski, & Sacramento sucker, Catostomus occidentalis) were associated with conditions of high river flow and turbidity, while the majority of the non-native species were associated with either warm water temperature or low river flow conditions. The exceptions were the non-native striped bass, Morone saxatilis, and white catfish, Ameiurus catus, which were positively associated with relatively high river flow. Variation in fish community structure was greater among river locations within years than within river locations among years, thus fish communities at each river location were consistently different each year. Differences in fish communities among river locations were correlated with river flow and turbidity. We predict that the fish communities of this region will remain numerically dominated by non-native species if the environmental conditions we observed persist in the future.     

Observations on the biology and seasonal variation in feeding of the east coast round herring Etrumeus wongratanai (Clupeiformes), off Scottburgh,KwaZulu-Natal,South Africa

The basic biology and ecology of the South African east coast round herring Etrumeus wongratanai was investigated from samples of fish collected between 2013 and 2016. This species is short-lived and reaches a maximum of 3 years of age, with rapid growth in its first year of life. It reproduces from June to December (austral summer) and condition factor was lowest in May through to August and increased from September, probably reflecting the physiological strain before and during spawning. Fish larvae were the most important food items consumed during summer, whereas eucalanid copepods were the most important prey at other times of the year. Stable-isotope data suggest that there are gradual changes in the trophic level with increasing fish size, δ¹⁵N and δ¹³C values also differed between seasons. The results obtained here are compared with those of other Etrumeus species, regionally and globally.     

Freshwater protozoa: biodiversity and ecological function

The purpose of this article is to pull together various elements from current knowledge regarding the natural history of free-living protozoa in fresh waters. We define their functional role, set the likely limits of biodiversity, and explore how the two may be related. Protozoa are unicellular, phagotrophic organisms, and 16 phyla of protists contain free-living freshwater protozoan species. They are the most important grazers of microbes in aquatic environments and the only grazers of any importance in anoxic habitats. In sediments, ciliates are usually the dominant protozoans. Benthic ciliate biomass accounts for slightly less than 10% of total benthic invertebrate biomass, but ciliate production may equal or even exceed invertebrate production. Freshwater protozoan species are probably ubiquitous, although many may persist locally for long periods in a cryptic state – as potential rather than active biodiversity. As protozoa are among the largest and most complex of micro-organisms, it follows that bacteria and all other smaller, more numerous microbes are also ubiquitous. The number of protozoan species recorded in local surveys (232) is about 10% of the estimated global species richness (2390). The 'seedbank of protozoan (and microbial) species ensures that local microbial diversity is never so impoverished that it cannot play its full part in ecosystem functions such as carbon fixation and nutrient cycling.     

鳜类鱼类的线粒体DNA控制区结构及其系统发育分析

鳜类为低等鲈形目鱼类,是东亚特有类群。然而,关于其系统位置、分类以及一些物种的有效性等尚有争议。采用PCR扩增直接测序的方法,获得了鳜、大眼鳜、斑鳜、暗鳜、波纹鳜、长体鳜、中国少鳞鳜线粒体DNA控制区基因的序列。对比其他已报道鱼类控制区的结构识别序列,对鳜类鱼类控制区的结构进行了分析,识别了终止序列区、中央保守区和保守序列区,并找到了DNA复制终止相关的序列ETAS和中央保守区的保守序列CSB-F、CSB-E、CSB-D以及保守序列区的保守序列CSB1、CSB2、CSB3。几种鳜鱼间共有191个变异位点,其中,终止序列区的变异最高,占总变异的61．3％,中央保守区和保守序列区占总变异的38．7％。这一结果可为全面了解鱼类线粒体DNA控制区的结构特征提供资料。同时,利用高度变异的控制区序列,以鲈科和错科作为外群,使用邻接法和最大简约法构建了这几种鳜鱼的系统发育树。结果表明：鳜类为一单系类群,鳜、大眼鳜、斑鳜、暗鳜、波纹鳜、长体鳜构成一支鳜鱼群,其中,鳜与大眼鳜为姐妹种;中国少鳞鳜为另一支少鳞鳜群;长体鳜未单独成一支,而是聚入鳜鱼群内,应更名为Siniperca roulei。研究结果支持将现生鳜类分为两个类群的观点。     

Vicariance and dispersal across Baja California in disjunct marine fish populations

Abstract.— Population disjunctions, as a first step toward complete allopatry, present an interesting situation to study incipient speciation. The geological formation of the Baja California Peninsula currently divides 19 species of fish into disjunct populations that are found on its Pacific Coast and in the northern part of the Gulf of California (also called the Sea of Cortez), but are absent from the Cape (Cabo San Lucas) region. We studied the genetic makeup of disjunct populations for 12 of these 19 fish species. Phylogeographic patterns for the 12 species can be separated into two major classes: a first group (eight species) showed reciprocal monophyly and high genetic divergence between disjunct populations. A second group (four species) displayed what appeared to be panmictic populations. Population structure between Pacific Coast populations, across the Punta Eugenia biogeographic boundary, was also evaluated. While dispersal potential (inferred by pelagic larval duration) was a poor predictor of population structure between Gulf of California and Pacific populations, we found that population genetic subdivision along the Pacific Coast at Punta Eugenia was always positively correlated with differentiation between Pacific and Gulf of California populations. Vicariant events, ongoing gene flow, and ecological characteristics played essential roles in shaping the population structures observed in this study.