Mineralized cartilage in the skeleton of chondrichthyan fishes

The cartilaginous endoskeleton of chondrichthyan fishes (sharks, rays, and chimaeras) exhibits complex arrangements and morphologies of calcified tissues that vary with age, species, feeding behavior, and location in the body. Understanding of the development, evolutionary history and function of these tissue types has been hampered by the lack of a unifying terminology. In order to facilitate reciprocal illumination between disparate fields with convergent interests, we present levels of organization in which crystal orientation/size delimits three calcification types (areolar, globular, and prismatic) that interact in two distinct skeletal types, vertebral and tessellated cartilage. The tessellated skeleton is composed of small blocks (tesserae) of calcified cartilage (both prismatic and globular) overlying a core of unmineralized cartilage, while vertebral cartilage usually contains all three types of calcification.     

Morphometric minefields—towards a measurement standard for chondrichthyan fishes

Size measurements are crucial for studies on the growth, maturation, maximum size, and population structure of cartilaginous fishes. However, researchers use a variety of measurement techniques even when working on the same species. Accurate comparison of results among studies is only possible if the measurement technique used is adequately defined and, if different techniques are used, a conversion equation can be derived. These conditions have not always been met, leading to invalid comparisons and incorrect conclusions. This paper reviews methods used for measuring chondrichthyans, and summarises the variety of constraints that influence the choice of a measurement technique. Estimates of the variability present in some measurement techniques are derived for shortfin mako shark, Isurus oxyrinchus, porbeagle shark, Lamna nasus, blue shark, Prionace glauca, Antarctic thorny skate, Amblyraja georgiana, and Pacific electric ray, Torpedo californica. Total length measured with the tail in the natural position (sharks) and disc widths (batoids) have higher variability than other methods, and are not recommended. Instead, the longest longitudinal axis should be measured where possible and practical; i.e., flexed total length for sharks, total length for batoids (excluding suborder Myliobatoidei), pelvic length for batoids of the suborder Myliobatoidei, and chimaera length (snout to posterior end of supracaudal fin) for chimaeroids (except for Callorhinchus, for which fork length should be measured from the anterior edge of the snout protuberance). Straight-line measurements are preferred to measurements over the curve of the body. Importantly, measurement methods must be clearly defined, giving information on the anterior reference point, the posterior reference point, and how the measurement was made between these two. Measurements using at least two different methods are recommended on at least a subsample of the fish in order to develop conversion regression relationships.     

Fauna and zoogeography of deep-benthic chondrichthyan fishes around the Japanese Archipelago

The deep-benthic chondrichthyan fishes collected by 584 hauls of otter-trawl from the Okinawa Trough, Kyushu-Palau Ridge, Pacific continental slope off northern Honshu Island (“Tohoku Slope”) and continental slope of Okhotsk Sea off Hokkaido (“Okhotsk Slope”) were analyzed. Sixty-one species were recorded from 200 to 1,520 m in depths; 37 species from the Okinawa Trough, 10 from the Kyushu-Palau Ridge, 18 from the Tohoku Slope, and nine from the Okhotsk Slope. The Okinawa Trough has the most varied composition, with many species of the Squalidae, Scyliorhinidae, and Rajidae (genusRaja). The Kyushu-Palau Ridge has a relatively high number of squalid species, but no species of the Rajidae or Chimaeriformes. The Tohoku Slope fauna is relatively varied, comprising six families, of which the Rajidae (genusBathyraja) is the most numerous, followed by the Squalidae. The Okhotsk Slope has the least number of species, and is characterized by a remarkable dominance of the Rajidae (genusBathyraja).     

A modern system of Fusarium taxonomy

A modern system of Fusarium taxonomy is proposed, based on the study over 30 years, of the morphology and growth characteristics of fungi of this genus, and their variability under a wide range of conditions. The system proposed here comprises 13 sections, 33 species and 14 varieties. It differs from systems published by other authors mainly in the sections Eupionnotes, Sporotrichiella, Arthrosporiella, Gibbosum, Discolor, Macroconia and Martiella.     

Immunization of fishes: a review

Immune response in fishes, which are ectothermic animals, depends on temperature. The optimum response is at the optimum temperature for the species. It is, however, slower in coldwater fishes, such as salmonids, and faster in warmwater fishes. Serum of fishes contains proteins very similar, but not identical, with those of mammals. Immune bodies are contained in gamma, beta, and alpha globulins. Gamma globulin is absent in some fishes. Fishes can be effectively immunized by injection of antigens, however, this is not a practical method. For this reason oral immunization has been attempted repeatedly but the effectiveness is variable.     

Transgenic fishes: modern state of the problem

Transgenic fishes are the object for the specialists in different research fields. It seems very promising to cultivate the rapidly growing objects resistant to diseases and negative environmental factors as well as the indicators of pollutions, models for oncological investigations etc. Some methodical, piscicultural, medical, ecological and others aspects of investigations of transgenic fishes as well as the legislative basis of Ukraine on this problem are discussed in the article.     

Bacterial flora of fishes: A review

Bacterial floras isolated from eggs, skin, gills, and intestines have been described for a limited number of fish species. Generally, the range of bacterial genera isolated is related to the aquatic habitat of the fish and varies with factors such as the salinity of the habitat and the bacterial load in the water. In many investigations, identification of isolates to the genus level only makes it difficult to determine the precise relationships of aquatic and fish microfloras. Bacteria recovered from the skin and gills may be transient rather than resident on the fish surfaces. Microfloras of fish intestines appear to vary with the complexity of the fish digestive system. The genera present in the gut generally seem to be those from the environment or diet which can survive and multiply in the intestinal tract, although there is evidence for a distinct intestinal microflora in some species. While obligate anaerobes have been recovered from carp and tilapia intestines, low ambient temperatures may prevent colonization by anaerobes in species such as rainbow trout.     

Protist taxonomy: an ecological perspective

This is an exploration of contemporary protist taxonomy within an ecological perspective. As it currently stands, the 'morphospecies' does not accommodate the information that might support a truly ecological species concept for the protists. But the 'morphospecies' is merely a first step in erecting a taxonomy of the protists, and it is expected to become more meaningful in the light of genetic, physiological and ecological research in the near future. One possible way forward lies in the recognition that sexual and asexual protists may all be subject to forces of cohesion that result in (DNA) sequence-similarity clusters. A starting point would then be the detection of 'ecotypes'--where genotypic and phenotypic clusters correspond; but for that we need better information regarding the extent of clonality in protists, and better characterization of ecological niches and their boundaries. There is some progress with respect to the latter. Using the example of a community of ciliated protozoa living in the stratified water column of a freshwater pond, it is shown to be possible to gauge the potential of protists to partition their local environment into ecological niches. Around 40 morphospecies can coexist in the superimposed water layers, which presumably represent different ecological niches, but we have yet to discover if these are discrete or continuously variable. It is a myth that taxonomic problems are more severe for protists than for animals and plants. Most of the fundamental problems associated with species concepts (e.g. asexuals, sibling species, phenotypic variation) are distributed across biota in general. The recent history of the status of Pfiesteria provides a model example of an integrated approach to solving what are essentially taxonomic problems.     

Pattern formation in development of chondrichthyan dentitions: a review of an evolutionary model

The mode of tooth development displayed in Chondrichthyans (sharks, rays and holocephalans), one of frequent tooth replacement, was possible once a dental lamina had evolved, and since 1982 this has been known as the odontode regulation theory after Reif. Today, Reif's concepts need to be transformed into those of modern biology, the crosstalk between epithelium and mesenchyme, for the regulation of timing, spacing and shape of vertebrate teeth. Although Reif's proposed ‘primordial tissue’ may be the only site of progenitor cells, to restrict odontogenic potential to time-specific sites (protogerms), as has been suggested in the sequential addition tooth (SAT) model, very little data are available. Here, his model of alternate tooth replacement files has been interpreted as an integrated tooth addition unit of two adjacent files (SAT) unit for alternate replacement of teeth, regulated by putative, precisely timed gene expression for activation and inhibition. We have provided new data on patterns of tooth succession in dentitions of extant sharks and rays to compare with those of Reif. Using a phylogeny combined from molecular and morphological data, it is suggested that the alternate tooth addition and replacement model is derived within Chondrichthyes, and diversified from single file tooth addition of the stem chondrichthyans.     

黏细菌资源及其系统分类

黏细菌是一类捕食性革兰氏阴性菌,广泛分布在土壤、海洋和淡水等生境中,是多类环境的优势类群。根据16S rRNA基因序列,黏细菌被归属于变形菌门的δ分支黏细菌目(Myxococcales)。新近根据120个保守性的单拷贝标识基因和16S rRNA基因序列,对变形菌门的系统分类学研究将黏细菌类群单列为黏细菌门(Myxococcota)。本文介绍了黏细菌资源的特性,并围绕从目到门的分类地位变迁,系统简述了黏细菌分类学研究的历史演变,对黏细菌资源的应用和发展进行了展望。     

Spatial scales in the study of reef fishes: A theoretical perspective

Abstract Theoretical models imply that spatial scale derives its greatest importance through interactions between density-dependent processes and spatial variation in population densities and environmental variables. Such interactions cause population dynamics on large spatial scales to differ in important ways from predictions based on measurements of population dynamics at smaller scales, a phenomenon called the scale transition. These differences can account for large-scale population stability and species coexistence. The interactions between density dependence and spatial variation that lead to the scale transition can be understood by the process of non-linear averaging, which shows how variance originating on various spatial scales contributes to large-scale population dynamics. Variance originating below the scale of density dependence contributes less to the scale transition as the spatial scale of the variation declines, while variation originating on or above the scale of density dependence contributes independently of the spatial scale of the variation.     

A lineage perspective on hominin taxonomy and evolution

An uncritical reliance on the phylogenetic species concept has led paleoanthropologists to become increasingly typological in their delimitation of new species in the hominin fossil record. As a practical matter, this approach identifies species as diagnosably distinct groups of fossils that share a unique suite of morphological characters but, ontologically, a species is a metapopulation lineage segment that extends from initial divergence to eventual extinction or subsequent speciation. Working from first principles of species concept theory, it is clear that a reliance on morphological diagnosabilty will systematically overestimate species diversity in the fossil record; because morphology can evolve within a lineage segment, it follows that early and late populations of the same species can be diagnosably distinct from each other. We suggest that a combination of morphology and chronology provides a more robust test of the single-species null hypothesis than morphology alone.     

A phylogenetic perspective on the evolution of Mediterranean teleost fishes

The Mediterranean Sea is a highly diverse, highly studied, and highly impacted biogeographic region, yet no phylogenetic reconstruction of fish diversity in this area has been published to date. Here, we infer the timing and geographic origins of Mediterranean teleost species diversity using nucleotide sequences collected from GenBank. We assembled a DNA supermatrix composed of four mitochondrial genes (12S ribosomal DNA, 16S ribosomal DNA, cytochrome c oxidase subunit I and cytochrome b) and two nuclear genes (rhodopsin and recombination activating gene I), including 62% of Mediterranean teleost species plus 9 outgroups. Maximum likelihood and Bayesian phylogenetic and dating analyses were calibrated using 20 fossil constraints. An additional 124 species were grafted onto the chronogram according to their taxonomic affinity, checking for the effects of taxonomic coverage in subsequent diversification analyses. We then interpreted the time-line of teleost diversification in light of Mediterranean historical biogeography, distinguishing non-endemic natives, endemics and exotic species. Results show that the major Mediterranean orders are of Cretaceous origin, specifically ~100-80 Mya, and most Perciformes families originated 80-50 Mya. Two important clade origin events were detected. The first at 100-80 Mya, affected native and exotic species, and reflects a global diversification period at a time when the Mediterranean Sea did not yet exist. The second occurred during the last 50 Mya, and is noticeable among endemic and native species, but not among exotic species. This period corresponds to isolation of the Mediterranean from Indo-Pacific waters before the Messinian salinity crisis. The Mediterranean fish fauna illustrates well the assembly of regional faunas through origination and immigration, where dispersal and isolation have shaped the emergence of a biodiversity hotspot.     

Phylogenetic analysis and taxonomy of the poecilioid fishes (Teleostei: Cyprinodontiformes)

Evidence from morphology is used to infer the phylogeny of the superfamily Poecilioidea using other cyprinodontoid fishes as outgroups. The three equally most parsimonious trees resulting from the phylogenetic analysis support the monophyly of the families Anablepidae and Poeciliidae with respect to each other, but the previous taxonomy within the Poeciliinae is not consistent with the resultant phylogenetic trees. The Poeciliidae is recognized with three subfamilies: the Aplocheilichthyinae containing solely Aplocheilichthys spilauchen , the Procatopodinae containing Fluviphylax (Fluviphylacini) and the African lamp-eyed killifishes (Procatopodini), and the Poeciliinae. The inferred hierarchical relationships of included suprageneric taxa are: ((Oxyzygonectinae, Anablepinae) (Aplocheilichthyinae ((Fluviphylacini, Procatopodini) (Alfarini (Priapellini (Gambusini (Heterandrini (Cnesterodontini (Girardini, Poeciliini))))))))). The tribe Alfarini is resurrected and a new tribe, the Priapellini, is described. Tomeurus gracilis is not the most basal poeciliine, and facultative viviparity in Tomeurus is not a plesiomorphic intermediate condition of viviparity retained from the common ancestor of poeciliines. Facultative viviparity in Tomeurus is the result of an evolutionary loss of obligate viviparity. Tomeurus gracilis is recognized as a member of the tribe Cnesterodontini. Lamprichthys tanganicus and Micropanchax pelagicus are not sister taxa, and the pelagic lacustrine habits of these two species are inferred to have evolved independently. Based on the principles of vicariance biogeography, the origin of the Poecilioidea is inferred to have occurred before the separation of Africa and South America.     

川蔓藻属系统分类和演化评述

川蔓藻属Ruppia为沉水单子叶植物,世界广布,主要为咸水和盐水生境,具有重要的生态价值、环境指示作用以及植物系统学研究意义.长期以来,川蔓藻属内种的数目以及属的系统位置一直存在争议.根据已有研究资料,目前川蔓藻属共有5个种--R.maritima、R cirrhosa、R. tuberosa、R, megacarpa和R.tuberosa、R.megacarpa和R.palycarpa得到多数学者的认可.关于其系统位置,主要有隶属于眼子菜科Potamogetonaceae和独立成川蔓藻科Ruppiaceae两种观点.尽管目前许多被子植物分类系统都承认了川蔓藻科.近年来分子系统学研究显示川蔓藻属与丝粉藻科cymodoceaceae和波喜荡科Posidoniaceae有近的亲缘关系,但对川蔓藻属和眼子菜属Potamogeton区别特征的比较结果倾向于支持将其放在眼子菜科.本文还结合川蔓藻属及相关类群的化石记录和果实特征对其演化进行了初步探讨,化石属Limnocarpus和Midravalva被认为是川蔓藻属较早的祖先类群,并认为该属植物应该是由淡水祖先逐渐演变成现在的咸水生长植物.最后,提出了在川蔓藻属未来研究中有待进一步解决的问题.