Stefano Cataudella

New developments in vertebrate cytotaxonomy III. Karyology of bony fishes: A review

Several years after the introduction of modern cytological techniques in the karyological study of the bony fishes, an attempt may be made to take stock of the results obtained, the problems raised and the difficulties encountered by workers engaged in this type of investigation. The first limitation is set by the value of the karyotype itself. Because it is purely morphological and its immediate adaptive value is unknown, karyotype transformations are difficult to interpret in analyses of populations of the same species or of related species. When related species are being compared, similar karyotypes are considered indicative of a relatively recent separation, whereas widely differing karyotypes are believed to indicate an earlier separation.However, this assumption is not always valid. In the bony fishes a karyotype composed of 48 acrocentric chromosomes occurs not only in related species but also in species that are phylogenetically further apart. In some taxa the karyotype therefore appears ‘neutral’ with respect to both speciation and phyletic evolution (Fig. 1) and it is therefore often impossible to establish a definite correlation between karyotype and karyotype transformations and to identify the processes involved. Although this situation diminishes the immediate value of the karyological evidence, it raises a series of questions that, when set in the right problematical context, make karyological analyses extremely interesting .

CMA3-banding pattern and fluorescence in situ hybridiz ation with 18S rRNA genes in zebrafish chromosomes

This study provides new data on zebrafish chromosomes, obtained from the chromomycin A3-banding pattern and mapping of18S rRNA genes by fluorescence in situ hybridization (FISH). C-banding and Ag-staining were also performed to analyse whether variation in heterochromatin and Ag-nucleolus organizer regions (NORs) exists among various commercially purchased strains. The results provide information on heterochromatin composition and on the existence of inter individual NOR polymorphism and contribute to the construction of an idiogram suitable for gene mapping.

The chromosomes of 11 species of cyprinidae and one cobitidae from Italy, with some remarks on the problem of polyploidy in the cypriniformes

The present paper gives a detailed description of the morphology of the karyotype of 11 Cyprinidae and 1 Cobitidae indigenous to Italian inland waters. The data relating to Chondrostoma toxostoma, C. soetta, Phoxinus phoxinus, Rutilus rubilio, Barbus meridionalis and Cobitis taenia are new from a karyological point of view; as regards Leuciscus cephalus, L. souffia, Alburnus alburnus, Scardinius erythrophtalmus, Tinca tinca and Barbus barbus the already known diploid numbers are confirmed and the morphology of the karyotypes is specified. The data on the morphology of the karyotype are used in discussing the problem of polyploidization of the chromosomal complement in both the Cyprinidae and the whole order Cypriniformes.

An expert system based on fish assemblages for evaluating the ecological quality of streams and rivers

Abstract Fish species have been often used as indicators of environmental quality in aquatic ecosystems, while biotic indices based on fish have become common tools in ecological monitoring. Nevertheless, such indices are far from perfect, mainly because they are based on assumptions that sometimes are not met and because they cannot be optimized from a computational point of view. As any other method, they rely upon expert judgments for selecting relevant metrics, combining metrics into a score and defining thresholds between ecological status classes in the scoring scale. Provided that no procedure can be entirely objective in evaluating ecological status, as this very concept is inherently subjective, we propose a novel approach in which the unavoidable subjective elements only play a role in the earliest steps, while the subsequent optimization of the evaluation procedure is as objective as possible. An expert system, designed after this concept for Latium (Central Italy) river basins and based on a multilayer perceptron neural network, was developed and implemented into a Graphical User Interface (GUI) in order to make it easily accessible to non-technical users. The neural network reconstructs experts judgments on the basis of a set of abiotic descriptors and fish assemblage composition, thus providing consensus estimates of ecological status for any river stretch. This approach allows easily the incorporation into the expert system of new data and new expert judgments as soon as they become available. However, the very first version of the expert system is already able to correctly classify 2 out of 3 cases, while the worst classification error does not exceed a single class of ecological status.

SMART: a spatially explicit bio-economic model for assessing and managing demersal fisheries, with an application to italian trawlers in the strait of sicily.

Management of catches, effort and exploitation pattern are considered the most effective measures to control fishing mortality and ultimately ensure productivity and sustainability of fisheries. Despite the growing concerns about the spatial dimension of fisheries, the distribution of resources and fishing effort in space is seldom considered in assessment and management processes. Here we propose SMART (Spatial MAnagement of demersal Resources for Trawl fisheries), a tool for assessing bio-economic feedback in different management scenarios. SMART combines information from different tasks gathered within the European Data Collection Framework on fisheries and is composed of: 1) spatial models of fishing effort, environmental characteristics and distribution of demersal resources; 2) an Artificial Neural Network which captures the relationships among these aspects in a spatially explicit way and uses them to predict resources abundances; 3) a deterministic module which analyzes the size structure of catches and the associated revenues, according to different spatially-based management scenarios. SMART is applied to demersal fishery in the Strait of Sicily, one of the most productive fisheries of the Mediterranean Sea. Three of the main target species are used as proxies for the whole range exploited by trawlers. After training, SMART is used to evaluate different management scenarios, including spatial closures, using a simulation approach that mimics the recent exploitation patterns. Results evidence good model performance, with a noteworthy coherence and reliability of outputs for the different components. Among others, the main finding is that a partial improvement in resource conditions can be achieved by means of nursery closures, even if the overall fishing effort in the area remains stable. Accordingly, a series of strategically designed areas of trawling closures could significantly improve the resource conditions of demersal fisheries in the Strait of Sicily, also supporting sustainable economic returns for fishermen if not applied simultaneously for different species.

VMSbase: An R-Package for VMS and Logbook Data Management and Analysis in Fisheries Ecology

VMSbase is an R package devised to manage, process and visualize information about fishing vessels activity (provided by the vessel monitoring system - VMS) and catches/landings (as reported in the logbooks). VMSbase is primarily conceived to be user-friendly; to this end, a suite of state-of-the-art analyses is accessible via a graphical interface. In addition, the package uses a database platform allowing large datasets to be stored, managed and processed vey efficiently. Methodologies include data cleaning, that is removal of redundant or evidently erroneous records, and data enhancing, that is interpolation and merging with external data sources. In particular, VMSbase is able to estimate sea bottom depth for single VMS pings using an on-line connection to the National Oceanic and Atmospheric Administration (NOAA) database. It also allows VMS pings to be assigned to whatever geographic partitioning has been selected by users. Standard analyses comprise: 1) métier identification (using a modified CLARA clustering approach on Logbook data or Artificial Neural Networks on VMS data); 2) linkage between VMS and Logbook records, with the former organized into fishing trips; 3) discrimination between steaming and fishing points; 4) computation of spatial effort with respect to user-selected grids; 5) calculation of standard fishing effort indicators within Data Collection Framework; 6) a variety of mapping tools, including an interface for Google viewer; 7) estimation of trawled area. Here we report a sample workflow for the accessory sample datasets (available with the package) in order to explore the potentialities of VMSbase. In addition, the results of some performance tests on two large datasets (1×105 and 1×106 VMS signals, respectively) are reported to inform about the time required for the analyses. The results, although merely illustrative, indicate that VMSbase can represent a step forward in extracting and enhancing information from VMS/logbook data for fisheries studies.

Shape Changes during the Growth of the Sea Bass, Dicentrarchus labrax (Teleostea: Perciformes), in Relation to Different Rearing Conditions

Thin-plate spline regression analysis is applied to sample of sea bass Dicentrarchus labrax, reared at two different salinities, i.e., marine and freshwater, in order to show shape changes and to test statistically morphological differences. All specimens were derived from the same breeding stock and were sampled at five different ages. Centroid size is used as the independent variable in the thin-plate spline regression analysis, and splines at extreme values of centroid size are computed and plotted. Differences in centroid size, for Bookstein’s uniform components (UI and U2) as well as for the pure nonuniform components of shape change are tested for significance. These analyses allow a visualization of allometry and description and testing of significance of the morphological plasticity of the sea bass. In this sense they can be valuable tools in the study of shape change during ontogeny.

A chromosome study of eight Mediterranean species of Sparidae (pisces, perciformes)

A cytotaxonomic study was made of eight Mediterranean species of Sparidae. It revealed a high degree of homogeneity in chromosome number and morphology. In fact, 7 out of 8 species have 2n = 48 (Sparus aurata, Pagellus acarne, P. erythrinus, Lithognathus mormyrus, Diplodus annularis, D. sargus and Sarpa salpa) and only Oblada melant~ra has 2n = 46. All species have a karyotype consisting mainly of acrocentric chromosomes; biarmed chromosomes are either absent or present to a maximum of 4 pairs. The data are discussed in the light of the groups taxonomy.

Cytogenetical characterization of Odontesthes bonariensis (Pisces, Atherinidae), an Argentine species introduced in Italy

Giemsa and Ag-staining techniques and C-banding were performed on cytological preparations of 22 specimens of silversides (Odontesthes bonariensis) in order to extend the karyological knowledge on the family Atherinidae, to contribute cytotaxonomically to the systematics of the species and to identify possible cytogenetical markers of the introduced population.The karyotype is conservative, 2n being 48, and 44 chromosomes being uniarmed. The remaining four biarmed chromosomes show intraindividual morphological variability. This variability is sex-independent. Ag-stanining techniques reveal that NORs are located on the short arms of biarmed chromosomes and that the morphological variability is partially due to NOR activity. C-banding revealed the associations between NORs and constitutive heterochromatin which could be responsible for some apparent structural differences. The differences found could be cytogenetical markers of the introduced population.

Testing Species Delimitations in Four Italian Sympatric Leuciscine Fishes in the Tiber River: A Combined Morphological and Molecular Approach

Leuciscine fishes represent an important component of freshwater ichthyofauna endemic to northern Mediterranean areas. This lineage shows high intra-specific morphological variability and exhibits high levels of hybridization, two characteristics that contribute to systematic uncertainties, misclassification of taxa and, potentially, the mismanagement of biodiversity. This study focused on brook chub, Squalius lucumonis, an endemic taxon of Central Italy. The taxonomic status of this species has long been questioned, and a hybrid origin from sympatric leusciscines (S. squalus x Rutilus rubilio, or S. squalus x Telestes muticellus) has been hypothesised. A phenotypic (evaluating shape and meristic counts) and genetic (using mitochondrial and nuclear markers) investigation of these four taxa was conducted to test species delimitation in sympatric areas and to evaluate the taxonomic status of S. lucumonis. One hundred and forty-five individuals of all four taxa were collected within streams of the lowest portion of the Tiber River basin and analysed; this region encompasses a large portion of the S. lucumonis distribution. The different morphological and genetic approaches were individually examined, compared, and then combined in a quantitative model to both investigate the limits of each approach and to identify cases of misclassification. The results obtained confirm the cladogenetic non-hybrid origin of S. lucumonis, highlight the need for immediate conservation actions and emphasise the value of an integrated approach in the study of leuciscines evolution.