Stefano Bovero

Structural-functional rearrangements in chromosome G in Chironomus riparius (Diptera, Chironomidae) collected from a heavy metal-polluted area near Turin, Italy

A natural population of Chironomus riparius from the heavy metal-polluted Piedmont station (Italy) was analysed. Chromosome G, on which the Balbiani rings BRa, BRb and BRc are located, was very sensitive to the pollution. The BR system was considered to be an interesting model for studying the response of the genome to the heavy metal pollution. Together, with a standard activity of BRs (BRc>BRb), we observed a clear reversed level of activity of BRb and BRc: BRc was repressed while BRb became activated. Also, there were a number of cells in which BRb and BRc were collapsed. A change in the activity of the nucleolar organizing region (N) was found, from a very high activity till completely collapsed. For the first time it was established that there was an activation at the telomere region of chromosome G. Additional active sites in sections Dc and E2de were observed. The conjugation of both homologues was often disturbed. A high frequency of ectopic pairings was also observed. In addition, structural rearrangements as inversions and deletions were found. Some deletions led to the formation of pompon-like chromosome G. Chromosome G of C. riparius is suggested to be used to test for the presence of genotoxic concentrations of polluting agents in an aquatic ecosystem.

Fatal chytridiomycosis in the tyrrhenian painted frog.

Batrachochytrium dendrobatidis (Bd), the causative agent of the amphibian disease chytridiomycosis, is an important factor in the global decline of amphibians. Within Europe, animals that exhibit clinical signs of the disease have only been reported in Spain despite the pathogen’s wide, but patchy, distribution on the continent. Recently, another occurrence of chytridiomycosis was reported in Euproctus platycephalus, the Sardinian brook newt, on the Mediterranean island of Sardinia, but without any evidence of fatal disease. We report further evidence of the emergence of Bd on Sardinia and the first evidence of lethal chytridiomycosis outside of Spain. Unusual mortalities of the Tyrrhenian painted frog (Discoglossus sardus) were found at three sites in the Limbara mountains of northern Sardinia. Molecular and histological screens of corpses, frogs, and tadpoles from these sites revealed infection with Bd. Infection and mortality occurred at locations that are unusual in terms of the published habitat requirements of the pathogen. Given the endemicity, the IUCN Red List status of the amphibian species on Sardinia, and the occurrence of infection and mortality caused by chytridiomycosis, there is serious reason for concern for the impact that disease emergence may have on the conservation of the amphibians of the island.

Nonrandom Chromosomal Distribution of Spontaneous Breakpoints and Satellite DNA Clusters in two Geographically Distant Populations of Chironomus Riparius (Diptera: Chironomidae)

Two geographically distant populations of Chironomus riparius (syn. C. thummi) from two environmentally polluted sites (Santena, Italy and Varna, Bulgaria) show numerous somatic and inherited chromosomal aberrations (inversions, deletions and deficiencies). Fifty-five percent of the observed breakpoints occurred in at least two larvae from both populations. Breakpoints occurring twice or more were considered as ‘common’ structural chromosomal breakpoints. We tested whether such common breakpoints in larvae of the two polluted populations had a random chromosomal distribution or occurred preferentially in specific heterochromatic regions. Distribution of common breakpoints was not random, and proximal regions of first and third chromosome had significantly more common breakpoints than distal ones. By FISH we identified and mapped 56 chromosomal sections containing clusters of two tandem-repetitive satellite DNA families called Hinf and Alu elements. Like the common breakpoints, these repetitive DNA clusters appeared to be significantly more abundant in regions of constitutive heterochromatin such as the pericentromeric regions, while in distal sections of chromosomal arms they were rare or absent. Twenty-four out of 45 common breakpoints (i.e., 53.3%) occurred in cytogenetic sections where Alu and Hinf satellite DNA probes hybridized. The frequency of co-localization between common breakpoints and repetitive DNA hybridization signals was significantly higher than expected by chance. We hypothesize that spontaneous or induced breaks occur more frequently in sections containing blocks of repetitive DNA.

On the edge of extinction? The spadefoot Pelobates fuscus insubricus in the Po Plain, and a glimpse at its conservation biology

The Italian spadefoot toad, Pelobates fuscus insubricus, is said to be in decline throughout its range (Po Plain, N Italy), and for this reason it has been object of conservation campaigns and included in conservation papers and projects. We have reviewed its distribution, and compared historical and current findings. These data support only partly the idea of a decline in numbers over the past century. Most likely, the species has always been quite localised in northern Italy, and also difficult to detect: the inferred rarefaction is likely the consequence of growing anthropisation and rapid habitat destruction in some areas of the Po Plain. In any case, in light of the most recent findings, the species sometimes appears to be locally abundant. The most critical area in terms of presence and biodiversity is the central-eastern part of the Po Plain, as is the case for many other amphibians and reptiles. We also present migration and biometrie data regarding a population near Ivrea (Turin Province). Over a period of about 40 days, we captured more than 300 individuals using pitfall devices, which indicated that the population is particularly abundant (500–1000 individuals). The sex-ratio was approximately 2:1 in favour of males, which is in accordance with former literature. A skeletochronological analysis indicated an individual mean age of 3 38 ± 0.77 years in males, and 4.00 ± 0.77 in females. A review of conservation initiatives suggests that the campaigns were useful in terms of educating the general public, but much remains to be done with regards to habitat protection and conservation. Special importance is given to studies regarding several little known aspects of the life history of the Italian populations.

The pandemic pathogen of amphibians, Batrachochytrium dendrobatidis (Phylum Chytridiomycota), in Italy.

Abstract Worldwide amphibian declines and species losses are global problems and emerging infectious diseases have been identified as one of the major threats. The worst of these is chytridiomycosis, an amphibian disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd). Here we review what is known of the distribution of Bd and chytridiomycosis in Italy. We critically summarize the evidence in support of the hypothesis that Bd is an invasive pathogen in Italy. Last we provide recommendations for immediate research needs, both for basic science and applied conservation.

Sexual selection and facultative paedogenesisin the Alpine Newt, Triturus alpestris apuanus (Bonaparte, 1839)

Abstract Paedogenetic and metamorphosed speciments of Triturus alpestris apuanus exhibit great morpho-functional differences, possibly environmentally induced. In order to evaluate the relative fitness of paedogenetic and metamorphosed males we looked for possible differences at the level of their reproductive behaviour and success. Metamorphosed males showed a higher probability to reach the final phase of spermatophore deposition. The two samples of males differed both in morphology and in reproductive efforts. Therefore the higher reproductive success of metamorphosed males may be the result of either their more striking morphology, or of their more strenuous efforts in courtship activity, or of a combination of both. This negative selective pressure on paedogenetic males in the sexual context may explain why the percentage of gilled breeding males is so low in the natural population that we studied.

Islands within an island: Population genetic structure of the endemic Sardinian newt, Euproctus platycephalus

Abstract The identification of historic and contemporary barriers to dispersal is central to the conservation of endangered amphibians, but may be hindered by their complex life history and elusive nature. The complementary information generated by mitochondrial (mtDNA) and microsatellite markers generates a valuable tool in elucidating population structure and the impact of habitat fragmentation. We applied this approach to the study of an endangered montane newt, Euproctus platycephalus. Endemic to the Mediterranean island of Sardinia, it is threatened by anthropogenic activity, disease, and climate change. We have demonstrated a clear hierarchy of structure across genetically divergent and spatially distinct subpopulations. Divergence between three main mountain regions dominated genetic partitioning with both markers. Mitochondrial phylogeography revealed a deep division dating to ca. 1 million years ago (Mya), isolating the northern region, and further differentiation between the central and southern regions ca. 0.5 Mya, suggesting an association with Pleistocene severe glacial oscillations. Our findings are consistent with a model of southward range expansion during glacial periods, with postglacial range retraction to montane habitat and subsequent genetic isolation. Microsatellite markers revealed further strong population structure, demonstrating significant divergence within the central region, and partial differentiation within the south. The northern population showed reduced genetic diversity. Discordance between mitochondrial and microsatellite markers at this scale indicated a further complexity of population structure, in keeping with male‐biased dispersal and female philopatry. Our study underscores the need to elucidate cryptic population structure in the ecology and conservation strategies for endangered island‐restricted amphibians, especially in the context of disease and climate change.

Karyotypes of four species of chironomids ( Diptera, Chironomidae ) from Northern Italy

Karyotypes of four chironomid species were studied: Cryptochironomus obreptans Walker, Cryptochironomus sp., Chironomus plumosus Linnaeus, and Stictochironomus rosenscholdi Zetterstedt. All these species belong to the subfamily Chironominae. Each species is characterized by a specific karyotype structure. The first species in the list has 2n = 4, while the three other species have 2n = 8.