Giovanni Strona

Global-scale relationships between colonization ability and range size in marine and freshwater fish

Although fish range sizes are expected to be associated with species dispersal ability, several studies failed to find a clear relationship between range size and duration of larval stage as a measure of dispersal potential. We investigated how six characteristics of the adult phase of fishes (maximum body length, growth rate, age at first maturity, life span, trophic level and frequency of occurrence) possibly associated with colonization ability correlate with range size in both freshwater and marine species at global scale. We used more than 12 million point records to estimate range size of 1829 freshwater species and 10068 marine species. As measures of range size we used both area of occupancy and extent of occurrence. Relationships between range size and species traits were assessed using Canonical Correlation Analysis. We found that frequency of occurrence and maximum body length had a strong influence on range size measures, which is consistent with patterns previously found (at smaller scales) in several other taxa. Freshwater and marine fishes showed striking similarities, suggesting the existence of common mechanisms regulating fish biogeography in the marine and freshwater realms.

Fish parasites resolve the paradox of missing coextinctions

Models of coextinction identify parasites as one of the most menaced ecological groups. The number of host species a parasite uses should strongly affect its risk of coextinction. The naïve expectation is that the lower the number, the higher is the parasites risk of being left with no hosts. Here we analyse the coextinction risk of 12,141 fish parasite species and find that highly specific parasites are not the most endangered, because they tend to use hosts with low vulnerability to extinction. This unexpected result may explain why the number of documented host-parasite coextinctions is much lower than predicted by theoretical studies.

FishPEST: an innovative software suite for fish parasitologists

Fish Parasite Ecology Software Tool (FishPEST) integrates fish parasite information from scientific literature, internet databases and museum collections with phylogenetic, biogeographical and ecological host data coming from Fishbase (http://fishbase.org). FishPEST is a dynamic web-based system using the open source scripting language Python [1xInteractively testing remote servers using the Python programming language. van Rossum, G. and de Boer, J. CWI Q. 1991; 4: 283–303See all References][1] and the Python-based web framework Django [2xThe Definitive Guide to Django: Web Development Done Right. Holovaty, A. and Kaplan-Moss, J. CrossrefSee all References][2]. Users do not need to download software and are free to use FishPEST without fee or login.FishPEST has three sections, namely Parasite Niche Modeler (PaNic), Parasite Co-occurrence Modeler (PaCo) and Parasite List Generator (PaL). PaL creates lists of known parasites per host, lists of known hosts per parasite and lists of host/parasite records. PaL is innovative in its input and output. It allows users to filter the internal database according to parasite (taxon, area of distribution) and host features (phylogeny, habitat, ecology), making it easy to test biogeographic, co-evolutionary and ecological hypotheses. Additionally, PaL can create presence–absence matrices to be used for further analyses. PaL provides basic statistical information for each generated list. Although there are many ways to generate lists of known parasites or hosts, it has, as yet, not been possible to systematically propose probable lists of parasites or hosts. PaNic generates a list of probable hosts for a parasite [3xSee all References][3], whereas PaCo generate lists of probable parasites for a host (G. Strona and K.D. Lafferty, unpublished). These tools are based on complex and flexible algorithms.FishPEST uses an internal database including more than 16 000 validated host/parasite records for the Acanthocephala, Cestoda, Monogenea, Nematoda and Trematoda. The host–parasite records of the FishPEST internal database derive from a much bigger list containing more than 64 000 host–parasite online records, which was reduced to a quarter during the validation process.The fact that we were able to validate only 25% of the collected data emphasizes the need for a comprehensive, peer-reviewed archive of host–parasite records. FishPEST aims to be that archive and also offers researchers a rich set of statistical tools for analyzing host/parasite relationships. Researchers can easily upload their peer-reviewed records to FishPEST.FishPEST was designed to be easy. Although it is a powerful tool for researchers, its user-friendly interface makes it possible for a non-specialist to quickly obtain useful information, allowing an occasional user to hypothesize what is going on in a home aquarium or helping a fish farmer to protect stocks from potential diseases. FishPEST can be accessed at http://purl.oclc.org/fishpest.

Environmental change makes robust ecological networks fragile

Complex ecological networks appear robust to primary extinctions, possibly due to consumers tendency to specialize on dependable (available and persistent) resources. However, modifications to the conditions under which the network has evolved might alter resource dependability. Here, we ask whether adaptation to historical conditions can increase community robustness, and whether such robustness can protect communities from collapse when conditions change. Using artificial life simulations, we first evolved digital consumer-resource networks that we subsequently subjected to rapid environmental change. We then investigated how empirical host–parasite networks would respond to historical, random and expected extinction sequences. In both the cases, networks were far more robust to historical conditions than new ones, suggesting that new environmental challenges, as expected under global change, might collapse otherwise robust natural ecosystems.

Field preservation of monogenean parasites for molecular and morphological analyses

In the present work we examined the efficacy of three different chemical solutions (EtOH 70%, DMSO-NaCl solution, and Longmire buffer) in field preservation of fish gills to be subsequently screened for monogenean specimens destined to morphological and molecular analyses. Degree of difficulty in collecting monogeneans from gills, morphological state of parasites, integrity of their DNA and reliability of sequence reading were observed and qualitatively compared to those of gills and parasites stored in 5% formalin and 99% ethanol. Data were collected over a period of 2 months. Storage in Longmire buffer resulted in dissociation of gills and parasites, while both DMSO and 70% ethanol provided a fine physical and molecular preservation of gills and monogeneans, allowing rapid collection of parasites from lamellae, and easy extraction, amplification and sequencing of parasitic DNA.

PREDICTING WHAT HELMINTH PARASITES A FISH SPECIES SHOULD HAVE USING PARASITE CO-OCCURRENCE MODELER (PaCo)

Abstract:u2003 Fish pathologists are often interested in which parasites would likely be present in a particular host. Parasite Co-occurrence Modeler (PaCo) is a tool for identifying a list of parasites known from fish species that are similar ecologically, phylogenetically, and geographically to the host of interest. PaCo uses data from FishBase (maximum length, growth rate, life span, age at maturity, trophic level, phylogeny, and biogeography) to estimate compatibility between a target host and parasite species–genera from the major helminth groups (Acanthocephala, Cestoda, Monogenea, Nematoda, and Trematoda). Users can include any combination of host attributes in a model. These unique features make PaCo an innovative tool for addressing both theoretical and applied questions in parasitology. In addition to predicting the occurrence of parasites, PaCo can be used to investigate how host characteristics shape parasite communities. To test the performance of the PaCo algorithm, we created 12,400 parasite lists by applying any possible combination of model parameters (248) to 50 fish hosts. We then measured the relative importance of each parameter by assessing their frequency in the best models for each host. Host phylogeny and host geography were identified as the most important factors, with both present in 88% of the best models. Habitat (64%) was identified in more than half of the best models. Among ecological parameters, trophic level (41%) was the most relevant while life span (34%), growth rate (32%), maximum length (28%), and age at maturity (20%) were less commonly linked to best models. PaCo is free to use at www.purl.oclc.org/fishpest.

Host range, host ecology, and distribution of more than 11 800 fish parasite species

Our data set includes 38u200a008 fish parasite records (for Acanthocephala, Cestoda, Monogenea, Nematoda, Trematoda) compiled from the scientific literature, Internet databases, and museum collections paired to the corresponding host ecological, biogeographical, and phylogenetic traits (maximum length, growth rate, life span, age at maturity, trophic level, habitat preference, geographical range size, taxonomy). The data focus on host features, because specific parasite traits are not consistently available across records. For this reason, the data set is intended as a flexible resource able to extend the principles of ecological niche modeling to the host–parasite system, providing researchers with the data to model parasite niches based on their distribution in host species and the associated host features. In this sense, the database offers a framework for testing general ecological, biogeographical, and phylogenetic hypotheses based on the identification of hosts as parasite habitat. Potential applications of the data set are, for example, the investigation of species–area relationships or the taxonomic distribution of host-specificity. The provided host–parasite list is that currently used by Fish Parasite Ecology Software Tool (FishPEST, http://purl.oclc.org/fishpest), which is a website that allows researchers to model several aspects of the relationships between fish parasites and their hosts. The database is intended for researchers who wish to have more freedom to analyze the database than currently possible with FishPEST. However, for readers who have not seen FishPEST, we recommend using this as a starting point for interacting with the database.

Monogenoidean parasites of Italian marine fish: An updated checklist

Abstract An updated checklist of the monogenoids infecting Italian marine fish is provided, including seven new records (Diplectanum simile on Sciaena umbra; Diplectanum sp. on Scorpaena porcus; Lamellodiscus elegans, L. ergensi, L. fraternus on Diplodus vulgaris; L. virgula on Pagellus erythrinus; Pseudanthocotyloides heterocotyle on Engraulis encrasicolus). The number of monogenoidean species recorded in Italian marine ichtyofauna is therefore increased to 141, harboured by 93 host species.

A protocol to compare nestedness among submatrices

Searching for nestedness has become a popular exercise in community ecology. Significance of a nestedness index is usually evaluated using z values, and finding that a matrix is nested is typically a common result. However, nestedness is not likely to be spread uniformly within a matrix of species presence/absence per site. Selected parts of the matrix may show a degree of nestedness significantly higher (or lower) than expected from the overall pattern. Here we describe a procedure to assess if a particular submatrix (i.e., a peculiar combination of rows and columns extracted from the complete matrix) is more or less nested than expected for an assortment of sites and species taken at random from the same overall matrix. The idea is to obtain several submatrices of different sizes from the same overall matrix and to calculate their z values. A regression is then performed between z values of submatrices and their sizes. A nestedness index independent of matrix size is suggested as the deviation of the z value of a particular submatrix from that expected according to the regression line. We applied our protocol to 55 matrices with different nestedness indices under various null-models and, for purpose of demonstration, we discussed in detail a single case study regarding various animal groups of the Aegean Islands (Greece). The obtained results strongly encourage further research to focus not only on the question whether a matrix is nested or not, but also on where and why nestedness is confined.

Monogenoidean parasites of fishes associated with coral reefs in the Ras Mohammed National Park, Egypt: preliminary results

SummaryA parasitological survey of the monogenoids of 14 species of common fishes associated with the local coral reefs of the Ras Mohammed National Park, National Parks of Egypt South Sinai Sector, Egypt, was carried out from May 2003 to May 2005. The monogenoids collected during the survey included 17 species: 8 previously described species, 7 new species in established genera, and 2 new species belonging to new genera.