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The land snail taxon Helix straminea Briganti, 1825 has been reintroduced as a valid species in 2014. We provide here a comprehensive account of its taxonomy, distribution, anatomy, phylogeny and karyology in Italy. An overview of the historical views on the validity of the species is presented and faunistic data are reviewed and implemented with new records from Campania and Basilicata. A lectotype is fixed for H. straminea from the syntypes stored in the Muséum d’Histoire Naturelle of Genève, as well as for three other taxa (Helix straminiformis Bourguignat, 1876, Helix yleobia Bourguignat, 1883 and Helix straminea ssp. elongata Bourguignat, 1860). Genital system, radula and karyotype are described for the first time. Molecular analysis of two mitochondrial genes combining GenBank data and the new sequences presented in this paper showed no differentiation between the northern and southern Italian populations. The conservation status of the species and its possible threats are discussed.

The knowledge of demographic traits such as longevity, growth rates and age at sexual maturity is crucial for understanding the structure of a population in its natural environment and implementing appropriate strategies for its management and conservation. Based on counts of growth layer groups in sections of decalcified teeth using the paraffin technique, we estimated the age and growth of 25 individuals of striped dolphin (Stenella coeruleoalba) found dead stranded along the coast of Campania and Calabria (south Italy, central-western Mediterranean) from 2013 to 2018. Seven individuals, with TL of 100–110 cm, were calves under 1 year old. The oldest male and female individuals were 19 and 14 years old, respectively. Growth curve estimated using the Gompertz growth model (GGM) showed that in S. coeruleoalba male growth trajectories are partly in accordance with those reported in other studies on the same species from different Mediterranean areas. The high frequency (28%) of calves strongly suggests that females of this species use the marine area all around the south-western Italian coasts to give birth to their offspring. Furthermore, a comparison with the estimated age of striped dolphins from other Mediterranean marine areas shows that the longevity of the individuals examined in this study is much lower. Our study provides information toward understanding the demographic traits of S. coeruleoalba from Mediterranean Sea. The results reported here can be useful for future research aimed at understanding population structure, mortality patterns and the effects of anthropogenic activity on the survival of this species in this marine area.

Simple Summary The Lycian salamanders of the genus Lyciasalamandra are characterized by a debated taxonomy and phylogenetic relationships. They have been the subject of various molecular and phylogenetic analyses, but their chromosomal diversity is completely unknown. We here present a comparative cytogenetic analysis on five out of the seven described species and seven subspecies of Lyciasalamandra, providing the first karyological assessment on the genus and comparing them to closely related representatives of the genus Salamandra. We analyzed the occurrence and distribution of different conserved (chromosome number and morphology) and highly variable karyological features. We found an impressive diversity in the configuration of nucleolus organizing regions (NORs), which alternatively occur either as heteromorphic or homomorphic loci on distinct regions of different chromosome pairs. We highlight that the observed peculiar taxon-specific pattern of chromosome markers supports the taxonomic validity of the different studied evolutionary lineages and is consistent with a scenario of synchronous evolution in the Lycian salamanders. Abstract We performed the first cytogenetic analysis on five out of the seven species of the genus Lyciasalamandra, including seven subspecies, and representatives of its sister genus Salamandra. All the studied species have a similar karyotype of 2n = 24, mostly composed of biarmed elements. C-bands were observed on all chromosomes, at centromeric, telomeric and interstitial position. We found a peculiar taxon-specific NOR configuration, including either heteromorphic and homomorphic NORs on distinct regions of different chromosomes. Lyciasalamandra a. antalyana and L. helverseni showed two homomorphic NORs (pairs 8 and 2, respectively), while heteromorphic NORs were found in L. billae (pairs 6, 12), L. flavimembris (pairs 2, 12), L. l. luschani (pairs 2, 12), L. l. basoglui (pairs 6, 12), L. l. finikensis (pairs 2, 6) and S. lanzai (pairs 8, 10). Homomorphic NORs with an additional supernumerary site were shown by S. s. salamandra (pairs 2, 8) and S. s. gigliolii (pairs 2, 10). This unexpected highly variable NOR configuration is probably derived from multiple independent NOR translocations and paracentric inversions and correlated to lineage divergence in Lyciasalamandra. These results support the taxonomic validity of the studied taxa and are consistent with a hypothesized scenario of synchronous evolution in the genus.

The data presented in this paper stand as supplementary information of the associated article “Karyological characterization of the common chameleon (Chamaeleo chamaeleon) provides insights on the evolution and diversification of sex chromosomes in Chamaeleonidae” [1] . This work provides (i) raw experimental data on the karyology of the common chameleon Chamaeleo chamaeleon and (ii) the results of bioinformatic analysis on sex-specific and repeated DNA sequences found in the same species. The karyological information here presented includes traditional staining method (Giemsa staining) and sequential C-banding + fluorochromes performed on Tunisian samples of the species. The sequence data include the alignments of the isolated DNA sequences with homologous sequences found in squamate Short Read Archives (SRAs) and the results of searches in public nucleic acid databases.

Simple Summary The superfamily Helicoidea is a large and diverse group of Eupulmonata. The superfamily has been the subject of several molecular and phylogenetic studies which greatly improved our knowledge on the evolutionary relationships and historical biogeography of many families. In contrast, the available karyological information on Helicoidea still results in an obscure general picture, lacking a homogeneous methodological approach and a consistent taxonomic record. Nevertheless, the available karyological information highlights the occurrence of a significant chromosomal diversity in the superfamily in terms of chromosome number (varying from 2n = 40 to 2n = 62), chromosome morphology and the distribution of different karyological features among different taxonomic groups. Here we performed a molecular and a comparative cytogenetic analysis on of 15 Helicoidea species of three different families. Furthermore, to provide an updated assessment of the chromosomal diversity of the superfamily we reviewed all the available chromosome data. Finally, superimposing all the chromosome data gathered from different sources on the available phylogenetic relationships of the studied taxa, we discuss the overall observed chromosome diversity in Helicoidea and advance a hypothesis on its chromosomal evolution. Abstract We performed a molecular and a comparative cytogenetic analysis on different Helicoidea species and a review of all the available chromosome data on the superfamily to provide an updated assessment of its karyological diversity. Standard karyotyping, banding techniques, and Fluorescence in situ hybridization of Nucleolus Organizer Region loci (NOR-FISH) were performed on fifteen species of three families: two Geomitridae, four Hygromiidae and nine Helicidae. The karyotypes of the studied species varied from 2n = 44 to 2n = 60, highlighting a high karyological diversity. NORs were on a single chromosome pair in Cernuella virgata and on multiple pairs in four Helicidae, representing ancestral and derived conditions, respectively. Heterochromatic C-bands were found on pericentromeric regions of few chromosomes, being Q- and 4′,6-diamidino-2-phenylindole (DAPI) negative. NOR-associated heterochromatin was C-banding and chromomycin A3 (CMA3) positive. Considering the available karyological evidence on Helicoidea and superimposing the chromosome data gathered from different sources on available phylogenetic inferences, we describe a karyotype of 2n = 60 with all biarmed elements as the ancestral state in the superfamily. From this condition, an accumulation of chromosome translocations led to karyotypes with a lower chromosome number (2n = 50–44). This process occurred independently in different lineages, while an augment of the chromosome number was detectable in Polygyridae. Chromosome inversions were also relevant chromosome rearrangements in Helicoidea, leading to the formation of telocentric elements in karyotypes with a relatively low chromosome count.

Sexual differentiation (SD) during development results in anatomical, metabolic, and physiological differences that involve not only the gonads, but also a variety of other biological structures, such as the brain, determining differences in morphology, behavior, and response in the breeding season. In many reptiles, whose sex is determined by egg incubation temperature, such as the leopard gecko, Eublepharis macularius, embryos incubated at different temperatures clearly differ in the volume of brain nuclei that modulate behavior. Based on the premise that "the developmental decision of gender does not flow through a single gene", we performed an analysis on E. macularius using three approaches to gain insights into the genes that may be involved in brain SD during the thermosensitive period. Using quantitative RT-PCR, we studied the expression of genes known to be involved in gonadal SD such as WNT4, SOX9, DMRT1, Erα, Erβ, GnRH, P450 aromatase, PRL, and PRL-R. Then, further genes putatively involved in sex dimorphic brain differentiation were sought by differential display (DDRT-PCR) and PCR array. Our findings indicate that embryo exposure to different sex determining temperatures induces differential expression of several genes that are involved not only in gonadal differentiation (PRL-R, Wnt4, Erα, Erβ, p450 aromatase, and DMRT1), but also in neural differentiation (TN-R, Adora2A, and ASCL1) and metabolic pathways (GP1, RPS15, and NADH12). These data suggest that the brains of SDT reptiles might be dimorphic at birth, thus behavioral experiences in postnatal development would act on a structure already committed to male or female.

Chameleons display high karyological diversity in chromosome number (from 2n = 20 to 62), morphology, heterochromatin distribution and location of specific chromosomal markers, making them unique study models in evolutionary cytogenetics. However, most available cytogenetic data are limited to the description of the chromosome number and morphology. Concerning sex chromosomes, our knowledge is limited to ZZ/ZW and Z1Z1Z2Z2/Z1Z2W systems in the genus Furcifer and the isolation of sex-linked, male-specific, sequences in Chamaeleo calyptratus, but the putative XY chromosomes have still to be identified in Chamaeleo and the conservation of male heterogamety in the genus needs confirmation from other species. In this study we performed a molecular and a cytogenetic analysis on C. chamaeleon, using standard, banding methods and molecular cytogenetics to provide a throughout karyological characterization of the species and to identify and locate the putative XY chromosomes. We confirm that the chromosome formula of the species is 2n = 24, with 12 metacentric macrochromosomes, 12 microchromosomes and NORs on the second chromosome pair. Heterochromatin was detected as weak C-bands on centromeric regions, differently from what was previously reported for C. calyptratus. Fluorescence in situ hybridization (FISH) showed the occurrence of interspersed telomeric signals on most macrochromosomes, suggesting that ancient chromosome fusions may have led to a reduction of the chromosome number. Using a combination of molecular and FISH analyses, we proved that male specific Restriction site-Associated DNA sequences (RADseq) isolated in C. calyptratus are conserved in C. chamaeleon and located the putative XY chromosomes on the second chromosome pair. We also identified different transposable elements in the focal taxa, which are highly interspersed on most chromosome pairs.

The common lizard (Zootoca vivipara) displays characteristic cytogenetic, reproductive, molecular, and biogeographic variability. This species comprises oviparous and viviparous populations with disjunct distribution and sex chromosome polymorphisms, from simple ZZ/ZW to complex Z1Z1Z2Z2/Z1Z2W systems with different morphologies of the W chromosome. In this study, we used the primers SINE A and SINE B and a newly designed primer pair to (1) obtain information on the presence and distribution of transposable elements (TEs) in 8 squamate families and (2) assess the chromosomal location of SINE Squam elements in Z. vivipara. PCR amplification with SINE A and SINE B produced single or multiple products in different Z. vivipara populations, subsequently used to design the SINE-Zv primers. Using the newly designed SINE-Zv primers, we identified 2 sequences of about 700 and 300 bp (SINE-Zv 700 and SINE-Zv 300) in all the investigated populations of Z. vivipara. Fluorescence in situ hybridizations showed a preferential localization of SINE-Zv sequences in the peritelomeric regions of almost all chromosomes, with the exception of the W. Both sequences contained a distinct segment of SINE Squam2. SINE-Zv 700 appeared to be restricted to Z. vivipara, while SINE-Zv 300 contained a partial Gypsy sequence that is highly conserved among Squamata and showed high identity values (72-93%) with several transcripts from different species. Using the same primers, we also highlighted the presence of another highly conserved Gypsy-like fragment in snakes which displayed significant similarity with the stomatin-like protein 2 of colubrids. Our results suggest that SINEs and the Gypsy-like elements are widely distributed among squamates and may have played an active role in their genomic evolution and differentiation.

The demand for caviar is growing as is its price on the market. Due to the decline of true caviar production from sturgeons, eggs from other fish species and other animals have been used as substitutes for caviar. The labels on these products should indicate the species from which the eggs were derived, but the label can be misleading in some cases. In this context, species identification using DNA analysis is crucial for traceability and authentication of caviar products. In this work, we applied the COIBar-RFLP procedure to obtain species-specific endonuclease restriction patterns useful to discriminate &ldquo, caviar&rdquo, species. The tested caviar products were identified as originating from eight species: Acipenser transmontanus, A. gueldenstaedtii, A. stellatus, A. baerii, Mallotus villosus, Huso huso, Cyclopterus lumpus and Eumicrotremus orbis. The results demonstrated that 14% of the caviar products examined have a label that does not indicate the species from which the eggs were originated. The MboI restriction enzyme produced specific profiles discriminating the eight species, confirming that the COIBar-RFLP is a useful approach for routine screening of seafood products due to its ease and rapid execution, as the results of screening can be obtained within 7 h, by-passing the need for sequencing.

Due to their particular phylogenetic position and biological characteristics, squamate reptiles and, in particular, snakes are becoming an increasingly important model for fields such as evolutionary biology, molecular ecology and adaptation. Recently, during a study to analyze the evolutionary history of European whip snakes, we found a LINE1 (L1)-like sequence (GenBank accession no. LM644476), herein called TRL1L, and while there are data on the abundance of L1 in snakes, their genomic and chromosome localization is still largely unexplored. We therefore performed a study to obtain information on TRL1L abundance, distribution and conservation in snake species, belonging to the Colubridae, Lamprophiidae and Viperidae families, using quantitative dot-blot and fluorescence in situ hybridization (FISH). TRL1L showed a high identity with homologous segments of L1s of lizards the Anolis carolinensis and Lacerta agilis and the zebrafish Danio rerio. The discovered sequences are truncated L1 elements which occur with a low copy number, about 0.1% of the genome of the species studied. This evidence suggests that L1 retroposons have a similar landscape in lizard and snake genomes, probably because similar processes limited L1 distribution in their genomes. TRL1L showed a non-random chromosome distribution pattern. It was scarcely located on autosomes and on the euchromatic W chromosome of Cerastes vipera, while mostly found on the heterochromatic W chromosome of Hierophis carbonarius and Elaphe quatuorlineata. Our data support the hypothesis that a ‘purifying selection’ against the accumulation of L1 elements takes place in recombining regions and highlight the possible role of these elements in the differentiation processes of the snake heterochromatic W chromosome. Interestingly, the preferential distribution of TRL1L on the heterochromatic W chromosomes of the studied snakes appears to be similar to that observed in mammals for L1 accumulation on differentiated Y chromosomes. This finding suggests that a convergent process may have taken place in the differentiation of vertebrate heterochromatic sex chromosomes

A cytogenetic study was carried out by means of standard and NOR-FISH staining methods on the chromosomes of four Alopiinae door snails, two species of the Delimini tribe (Siciliaria paestana and Papillifera bidens) and two species of Medorini tribe (Leucostigma candidescens and Medora sp.). The two Delimini species and Medora sp. showed similar karyotypes, concerning the number of chromosomes, 2n = 62, and the first metacentric pair of chromosomes clearly bigger than the other pairs, but differed in the number of the telocentric pairs: none in P. bidens, four in S. paestana and, even, 21 in Medora sp. Leucostigma candidescens had 2n = 48, all biarmed chromosomes. Loci of NORs were on a single medium small chromosome pair in all the four studied species. The obtained results evidence a relevant degree of intergeneric karyotypic diversity in Alopiinae, concerning both chromosome number and/or shape. The data allow us to make a hypothesis on the evolutionary chromosome trends for this door snail subfamily.

Within the scope of a project on the characterization of satellite DNAs in polar mollusks, the Antarctic chiton Nuttallochitonmirandus (Thiele, 1906) was analyzed. Two novel families of tandemly repeated DNAs, namely NmH and NmP, are described in their structure and chromosomal localization, and, furthermore, their presence was analyzed in related species. Data reported here display a particular variability in the structural organization of DNA satellites within this species. Processes driving satellite evolution, which are likely responsible for the intriguing variability of the identified satellite DNAs, are discussed.

Microdissection, DOP-PCR amplification and microcloning were used to study the large Y chromosome of Chionodraco hamatus, an Antarctic fish belonging to the Notothenioidei, the dominant component of the Southern Ocean fauna. The species has evolved a multiple sex chromosome system with digametic males showing an X1YX2 karyotype and females an X1X1X2X2 karyotype. Fluorescence in situ hybridization, performed with a painting probe made from microdissected Y chromosomes, allowed a deeper insight on the chromosomal rearrangement, which underpinned the fusion event that generated the Y. Then, we used a DNA library established by microdissection and microcloning of the whole Y chromosome of Chionodraco hamatus for searching sex-linked sequences. One clone provided preliminary information on the presence on the Y chromosome of the CHD1 gene homologue, which is sex-linked in birds but in no other vertebrates. Several clones from the Y-chromosome mini-library contained microsatellites and transposable elements, one of which mapped to the q arm putative fusion region of the Y chromosome. The findings confirm that interspersed repetitive sequences might have fostered chromosome rearrangements and the emergence of the Y chromosome in Chionodraco hamatus. Detection of the CHD1 gene in the Y sex-determining region could be a classical example of convergent evolution in action.

A karyological analysis on six Italian populations the slow worm (Anguis veronensis Pollini, 1818) was performed and their genetic differentiation at the mitochondrial 16S rRNA gene fragment from a Spanish sample has been assessed. The Italian populations were karyologically uniform, all showing 2n= 44 elements, of which 20 were macrochromosomes and 24 microchromosomes. Comparison with literature data on Central European populations showed a difference on the morphology of the 10th chromosome pair: submetacentric in Italian populations and telocentric in the Central European ones. Our analysis showed the presence of a fragile site on chromosomes of this pair, suggesting its propensity for structural rearrangements. Analysis of the 16S rRNA gene fragment showed uniformity among Italian populations (uncorrected genetic distance of 0.4%), and their genetic distinctness from the Spanish individual (uncorrected genetic distance of 4.2%). Our results confirm the existence of two different Anguis fragilis Linnaeus, 1758 lineages, each one characterized by a different cytotype.

Glycoconjugates secreted by the pedal system of the rayed limpet, Patella caerulea, were characterised in situ by histochemical and lectin-histochemical methods in individuals collected around the annual cycle, in November, March, and June. Stainings with periodic acid-Schiff (PAS), Alcian blue pH 2.5 (AB pH 2.5), Alcian blue pH 1.0 (AB pH 1.0), high-iron diamine-Alcian blue pH 2.5 and lectin binding assays with 9 lectins (Con A, WGA, succinylated-WGA, PNA, DBA, SBA, AAA, UEA-I, LTA) were performed. Four secreting cell types were observed in the sole, one in the peripheric region, and two in the sidewall. Glycoconjugate composition varied among cell types and also in one and the same cell type throughout the year. β-Elimination followed by PAS and AB pH 2.5 stainings indicated that most saccharidic chains were O-linked to the protein backbone. Secretion by sole and peripheric region was acidic, carboxylated and/or sulfated, whereas that of the sidewall was neutral. Glucosaminylated and 1,4-fucosylated residuals were predominant in the cell types along the year, 1,2-fucosylated residuals being observed only in the sidewall cells in June. Mannosylated and/or glycosylated residuals were observed in all cells mostly in November. Galactosylated/galactosaminylated residuals were present mostly in the sidewall cells and in the sole subepidermal mucocytes in June. Mannosylated and/or glycosylated residuals in November are probably linked to gonad maturation or to higher locomotion and foraging activity, whereas galactosaminylation in the sole cells and 1,2-fucosylation and glucosaminylation in the sidewall cells in June are linked to a prolonged stationary state, increasing water adsorption to counteract dehydration and/or to modulate microbial interactions.

Blindsnakes are poorly studied reptiles from the karyological point of view since chromosomal data are only known for eight out of more than 420 species. The present paper shows the results of a karyological study conducted by means of standard and banding staining (Ag-NOR-banding and C-banding plus CMA and DAPI fluorochromes) on three typhlopid species, Madatyphlops arenarius, Xerotyphlops vermicularis and the parthenogenetic blindsnake, Indotyphlops braminus . Madatyphlops arenarius has conserved the primitive snake karyotype of 2n = 36 with 16 biarmed macro- and 20 microchromosomes and NORs on a microchromosome pair. The karyotype of X . vermicularis differed in showing a reduced number of microchromosomes (16) and NORs on the long arms of the third macrochromosome pair. The parthenogenetic I . braminus exhibited a triploid karyotype of 3n = 42 with seven macro- and seven microtriplets and NORs on a microtriplet. Comparison with chromosome data from the available literature suggests that the primitive snake karyotype of 2n = 36 occurred in the common ancestor of Leptotyphlopidae + Typhlopidae and in the common ancestor of Typhlopidae. In the latter family chromosome evolution may well have proceeded towards a decrease in the chromosome number from 2n = 36, 34, 32 until it reached 2n = 28, mainly involving micro- to microchromosome and/or macrochromosome translocations. Furthermore, these chromosome rearrangements occurred independently and repeatedly in the different evolutionary lineages of this family and are partially concordant with phylogenetic relationships. Cytologically identifiable sex chromosomes were not revealed by either standard or C-banding staining.

A karyological study conducted by both conventional and banding staining methods (Ag-NOR-, CMA3, and C-banding) evidenced a peculiar heterochromatin pattern on chromosomes of Moldovan specimens of the agile frog, Rana dalmatina. As is normal for all agile frogs, the Moldovan population presented 2n = 26 chromosomes, with NOR loci on the short arms of the third chromosome pair, but differed in showing heavy centromeric, CMA3 positive C-bands on the seventh chromosome pair, and light centromeric, DAPI positive C-bands on five chromosome pairs. In contrast, Moldovan specimens showed no significant difference in two segments of the 16S mitochondrial rRNA gene and in the S1 satellite DNA sequence and organization, in comparison with the GenBank deposited 16S rDNA and S1 DNA satellite sequences of R. dalmatina. Molecular similarity and chromosomal differences between agile frogs from Moldovan and extra-Moldovan populations are discussed.

Karyological studies continue to clarify the evolutionary history of many taxa. We report here on the first chromosome survey of the frog Pseudhymenochirus merlini (Pipidae) in comparison with the related species Hymenochirus boettgeri . In addition to the 2 n = 20 regular (A) chromosomes (eight metacentric and two subtelocentric pairs), H. boettgeri has an accessory B chromosome in about half of the scored karyotypes (2 n = 21). P. merlini showed a karyotype of 2 n = 20 chromosomes, differing from the set of A chromosomes of H . boettgeri by three inversions. Other differences are in the location of the nucleolus organizer regions (NORs), on the 10th chromosome pair in P. merlini instead of the 4th pair in H. boettgeri . Heterochromatin is less abundant in P. merlini , and localized in centromeric and telomeric regions of all chromosomes. The patterns in H. boettgeri resemble those of another pipid species, Silurana tropicalis , as to chromosome number (2 n = 20), morphology, and G-banding patterns. We propose that these characteristics are symplesiomorphic in Pipidae, allowing us to present a scenario for the chromosome evolution in this family. Our results identify a third mechanism of increase in chromosome numbers among pipid frog species, the addition of B chromosomes in Hymenochirus , besides the known processes of polyploidization in Xenopus / Silurana , and centric fission in Pipa .

The aim of this work is to investigate the sequence conservation and the evolution of repeated DNA in related species. Satellite DNA is a component of eukaryotic genomes and is made up of tandemly repeated sequences. These sequences are affected by high rates of mutation that lead to the occurrence of species-specific satellite DNAs, which are different in terms of both quantity and quality. In this work, a novel repetitive DNA family, named PjHhaI sat, is described in Pecten jacobaeus. The quantitative analyses revealed a different abundance of this element in the molluscan species investigated in agreement with the "library hypothesis" even if, in this case, at a high taxonomic level. In addition, the qualitative analysis demonstrated an astonishing sequence conservation not only among scallops but also in six other molluscan species belonging to three classes. These findings suggest that the PjHhaI sat may be considered as the most ancients of DNA described so far, which remained "frozen" during molluscan evolution. The widespread distribution of this sat DNA in molluscs as well as its long evolutionary preservation open up questions on the functional role of this element. A future challenge might be the identification of proteins or molecules which interact with the PjHhaI sat.

Two new high repetitive DNAs were isolated from Discoglossus pictus genomic DNA digested with StuI. Sequence analysis of clones indicated two types of repetitive units 143–148 bp and 170–177 bp long, respectively. Southern blot analyses show ladders of bands indicating that both repetitive units are organized in long tandem arrays and belong to two different satellite DNAs that were named Dp-sat2 and Dp-sat3. A similar ladder of bands was also produced when genomic DNA was digested with ClaI in the case of Dp-sat2, or with ScaI in the case of Dp-sat3. Quantitative dot-blot analyses indicate that Dp-sat2 and Dp-sat3 account for about 2.6% and 2.2%, respectively, of the D. pictus genome. Considering that D. pictus has a genomic DNA content of 10.5 pg/N, our data indicate that Dp-sat2 and Dp-sat3 repetitive units are present in about 2.3 millions and 1.6 millions copies per diploid genome, respectively. Dp-sat2 and Dp-sat3 probes produced the same patterns of hybrid bands in Southern blots and the same genomic content in dot-blots in all the other Discoglossus species, except D. montalentii which showed a different band pattern and genomic content. The chromosomal distribution of the two StuI satellites shows some similarities: both Dp-sat2 and Dp-sat3 probes mainly labelled the pericentromeric regions of the large chromosome pairs 1–5 and 7. Moreover, probes from both satellite DNAs also produced faint fluorescent mini-spots along almost all chromosome pairs. These data suggest that both satellite DNAs have two types of organization, one in long arrays localized in pericentromeric positions, and the other in short arrays dispersed in the genome.

We describe the karyotype, location of nucleolus-organizing regions (NORs) and heterochromatin composition and distribution in Lepidochitona caprearum (Scacchi, 1836). The examined specimens had 2n=24 chromosomes; the elements of pairs 1 – 4 were metacentric, subtelocentric those of the fifth pair, telocentric the elements of other pairs. NOR-FISH, AG-NOR- and CMA3 banding showed NORs localized on pericentromeric regions of a medium small sized, telocentric chromosome pair. After C-banding or digestions with restriction enzyme NOR associate heterochromatin only was cytologically evident, resulting CMA3 positive. The comparison with other chitons chromosome data, other than to evidence a karyotypic similarity of L. caprearum to species of suborder Acanthochitonina, allows also to infer that chromosome evolution in the suborder mainly occurred via reduction of the number of the chromosomes by centric fusions, which took place repeatedly and independently in the different lineages of Acanthochitonina.

The present paper shows the results of chromosome banding and rDNA-FISH study performed on several specimens of different populations of Patella caerulea, Patella rustica and Patella ulyssiponensis. The taxonomic attribution of specimens was ascertained by the molecular phylogenetic analysis of the mitochondrial 16S rRNA gene. P. caerulea and P. rustica had 2n = 18 chromosomes with first seven of biarmed pairs and the remaining two uniarmed pairs. P. ulyssiponensis had 2n = 16 with all biarmed chromosomes. Ag-NOR loci were on the short arms of the first metacentric pair in the three studied limpets, whereas they showed a different pattern of heterochromatin distribution and composition. A chromosome mosaicism was observed in several P. caerulea specimens, which exhibited an unpaired metacentric element and loss of a telocentric pair. The obtained results suggest that in the genus Patella specific diversification was accompanied by variations in heterochromatin distribution and composition and reduction of chromosome number by Robertsonian centric fusion.