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Endemic species with restricted geographic ranges potentially suffer the highest risk of extinction. If these species are further fragmented into genetically isolated subpopulations, the risk of extinction is elevated. Habitat fragmentation is generally considered to have negative effects on species survival, despite some evidence for neutral or even positive effects. Typically, non-negative effects are ignored by conservation biology. The Montseny brook newt (Calotriton arnoldi) has one of the smallest distribution ranges of any European amphibian (8 km ) and is considered critically endangered by the International Union for Conservation of Nature. Here we apply molecular markers to analyze its population structure and find that habitat fragmentation owing to a natural barrier has resulted in strong genetic division of populations into two sectors, with no detectable migration between sites. Although effective population size estimates suggest low values for all populations, we found low levels of inbreeding and relatedness between individuals within populations. Moreover, C. arnoldi displays similar levels of genetic diversity to its sister species Calotriton asper, from which it separated around 1.5 million years ago and which has a much larger distribution range. Our extensive study shows that natural habitat fragmentation does not result in negative genetic effects, such as the loss of genetic diversity and inbreeding on an evolutionary timescale. We hypothesize that species in such conditions may evolve strategies (for example, special mating preferences) to mitigate the effects of small population sizes. However, it should be stressed that the influence of natural habitat fragmentation on an evolutionary timescale should not be conflated with anthropogenic habitat loss or degradation when considering conservation strategies.

Many studies have been carried out along mighty rivers with heavily industrialized watersheds to evaluate pollutants and their effects on freshwater organisms. However, their impact on marine organisms is virtually unknown. In order to cover this gap, Solea solea, one of the most important commercial fish species, together with sediments, were sampled during 2013–2015 offshore from the Ebro Delta river mouth. Fish health indicators (condition indices, histological tissue alterations, and parasite descriptors) were used to assess the potential effect of pollutants, an issue of particular interest in the area following the dredging activities taking place in the river upstream in 2013. No major histopathological alterations were detected, but perivascular inflammatory foci (PIF) were frequently observed, especially in 2014. The most prevalent and abundant parasites were acanthocephalans and digeneans within the digestive tract and copepods on the gills. Levels of trace metals from sediments and fish muscle were below the effects range median and reference levels accepted for human consumption, respectively. However, the lower levels of the hepatosomatic index, higher numbers of PIF, and variations in the abundance of parasites in 2014 and 2015 could suggest a pollutant exposure during these years. These results warn signs of toxicity, which could be associated with sediment leaks during the dredging activities.

The current work presents new data on the pycnogonids collected during the ANTXXI/2 cruise on board of “Polarstern” R/V during December 2003 and January 2004 in the Eastern Weddell Sea (Antarctica). Twenty-eight samples were taken, with different trawls, from depths between 120 and 1,866 m. In total, 251 specimens of pycnogonids, belonging to 31 species, were collected. Five species were observed to increase their depth range while six were found for the first time in the Weddell Sea, exhibiting an expansion in their geographical distribution, and confirming the general trend toward the circumpolarity of this group (23 of 31 species were circumpolar). Pallenopsis kupei is new for Antarctic waters. The most abundant species were Colossendeis megalonyx and Nymphon australe. Current data were completed with the samples collected from the same region during Polarstern cruise ANTXIII/3 (EASIZ I) in February-March 1996. Bathymetric patterns of distribution were analyzed for the total of 1,564 specimens (82 species, 14 genera). The results showed a difference in the composition between the continental shelf (from 100 to 900 m depth) and the slope (below 900 m), where the genus Nymphon dominated. Depth seems to be an influential factor in the structure of pycnogonid assemblages.

Biodiversity and biogeographic studies comparing the distribution patterns of benthic marine organisms across the Iberian Atlantic and Mediterranean waters are scarce. The Pycnogonida (sea spiders) are a clear example of both endemicity and diversity, and are considered a key taxon to study and monitor biogeographic and biodiversity patterns. This is the first review that compiles data about abundance and diversity of Iberian pycnogonids and examines their biogeographic patterns and bathymetric constraints using GIS tools. A total of 17,762 pycnogonid records from 343 localities were analyzed and were found to contain 65 species, 21 genera and 12 families. Achelia echinata and Ammothella longipes (family Acheliidae) were the most abundant comprising ~80% of the total records. The Acheliidae is also the most speciose in Iberian waters with 15 species. In contrast, the family Nymphonidae has 7 species but is significantly less abundant (<1% of the total records) than Acheliidae. Species accumulation curves indicate that further sampling would increase the number of Iberian species records. Current sampling effort suggests that the pycnogonid fauna of the Mediterranean region may be richer than that of the Atlantic. The Strait of Gibraltar and the Alboran Sea are recognized as species-rich areas that act as buffer zones between the Atlantic and Mediterranean boundaries. The deep waters surrounding the Iberian Peninsula are poorly surveyed, with only 15% of the sampling sites located below 1000 m. Further deep-water sampling is needed mainly on the Iberian Mediterranean side.

The Pyrenees represent a natural laboratory for biogeographic, evolutionary and ecological research of mountain fauna as a result of the high variety of habitats and the profound effect of the glacial and interglacial periods. There is a paucity of studies providing a detailed insight into genetic processes and better knowledge on the patterns of genetic diversity and how they are maintained under high altitude conditions. This is of particular interest when considering the course of past climate conditions and glaciations in a species which is considered site tenacious, with long generation times. Here we analyzed the genetic patterns of diversity and structure of the endemic Pyrenean brook newt (Calotriton asper) along its distribution range, with special emphasis on the distinct habitat types (caves, streams, and lakes), and the altitudinal and geographical ranges, using a total set of 900 individuals from 44 different localities across the Pyrenean mountain range genotyped for 19 microsatellite loci. We found evidence for a negative longitudinal and positive altitudinal gradient of genetic diversity in C. asper populations. The fact that genetic diversity was markedly higher westwards is in accordance with other Pyrenean species. However, the impact of altitudinal gradient on the genetic diversity seems to differ from other species, and mostly from other amphibians. We found that lower altitudes can act as a barrier probably because the lowlands do not provide a suitable habitat for C. asper. Regarding the distinct habitat types, caves had significantly lower values of genetic diversity compared to streams or lakes. The mean FST value was relatively high (0.304) with maximum values as high as 0.771, suggesting a highly structured total population. Indeed, populations were grouped into five subclusters, the eastern populations (cluster 1) remained grouped into two subclusters and the central-western Pyrenees (cluster 2) into three subclusters. The increase of isolation with geographical distance is consistent with the population structure detected. In conclusion, C. asper seems to be adapted to high altitude mountain habitats, and its genetic diversity is higher in the western Pyrenees. In terms of conservation priority, we consider more relevant the populations that represent a reservoir of genetic diversity.

The genus Culicoides Latreille 1809 is a well-known vector for protozoa, filarial worms and, above all, numerous viruses. The Bluetongue virus (BTV) and the recently emerged Schmallenberg virus (SBV) are responsible for important infectious, non-contagious, insect-borne viral diseases found in domestic ruminants and transmitted by Culicoides spp. Both of these diseases have been detected in wild ruminants, but their role as reservoirs during the vector-free season still remains relatively unknown. In fact, we tend to ignore the possibility of wild ruminants acting as a source of disease (BTV, SBV) and permitting its reintroduction to domestic ruminants during the following vector season. In this context, a knowledge of the composition of the Culicoides species communities that inhabit areas where there are wild ruminants is of major importance as the presence of a vector species is a prerequisite for disease transmission. In this study, samplings were conducted in areas inhabited by different wild ruminant species; samples were taken in both 2009 and 2010, on a monthly basis, during the peak season for midge activity (in summer and autumn). A total of 102,693 specimens of 40 different species of the genus Culicoides were trapped; these included major BTV and SBV vector species. The most abundant vector species were C. imicola and species of the Obsoletus group, which represented 15% and 11% of total numbers of specimens, respectively. At the local scale, the presence of major BTV and SBV vector species in areas with wild ruminants coincided with that of the nearest sentinel farms included in the Spanish Bluetongue Entomological Surveillance Programme, although their relative abundance varied. The data suggest that such species do not exhibit strong host specificity towards either domestic or wild ruminants and that they could consequently play a prominent role as bridge vectors for different pathogens between both types of ruminants. This finding would support the hypothesis that wild ruminants could act as reservoirs for such pathogens, and subsequently be involved in the reintroduction of disease to livestock on neighbouring farms.

Ex situ management strategies play an important role in the conservation of threatened species when the wild survival of the species cannot be ensured. Molecular markers have become an outstanding tool for the evaluation and management of captive breeding programs. Two main genetic objectives should be prioritized when planning breeding programs: the maintenance of maximum neutral genetic diversity, and to obtain “self-sustaining” captive populations. In this study, we use 24 microsatellite loci to analyze and evaluate the genetic representativity of the initial phases of the captive breeding program of the Montseny brook newt, Calotriton arnoldi , an Iberian endemic listed as Critically Endangered. The results show that the initial captive stock has 74–78% of the alleles present in the wild populations, and captures roughly 93–95% of their total genetic diversity as observed in a previous study on wild newts, although it does not reach the desired 97.5%. Moreover, the percentage of unrelatedness among individuals does not exceed 95%. Therefore, we conclude that the genetic diversity of the captive stock should be improved by incorporating genetic material from unrelated wild newts. In recognition of the previously described significant genetic and morphological differentiation between eastern and western wild populations of C. arnoldi , we suggest maintaining two distinct breeding lines, and we do not recommend outbreeding between these lines. Our comparisons of genetic diversity estimates between real and distinct sample-sized simulated populations corroborated that a minimum of 20 individuals are needed for each captive population, in order to match the level of genetic diversity present in the wild populations. Thus, the current initial stock should be reinforced by adding wild specimens. The captive stock and subsequent cohorts should be monitored in order to preserve genetic variation. In order to avoid genetic adaptation to captivity, occasionally incorporating previously genotyped individuals from the wild into the captive populations is recommended.

The Small-Spotted Catshark (Scyliorhinus canicula) is one of the most captured elasmobranchs off the Mediterranean Sea. Characterization of its sexual maturation, reproductive features, and the role of the liver in reproduction is detailed based on individuals captured off the Catalan coast (Balearic Sea, Northwest Mediterranean) between February 2022 and February 2023. Five and three reproductive stages for females and males, respectively, are described macroscopically and supported by microscopic description and changes in body size and somatic indices. The significant reduction of the hepatosomatic index when maturation is reached confirms the important role of the liver as an energy provider during reproduction, linked to lipid expenditure for vitellogenesis, spermatogenesis, or other energy-consuming activities related to reproduction. Liver color variability was associated with reproduction rather than nutritional status, as suggested by differences observed across reproductive stages and sex, along with the relatively stable values of the Le Cren condition index. The presence of mature-laying females and mature males and the similar mean values of the gonadosomatic index throughout the year confirmed a continuous reproductive period. A decreasing trend in the length at 50% maturity (L50) compared to previous estimates is observed in the Balearic Sea but could also be occurring in other areas. This is further discussed in the present study, as several hypotheses arise (e.g., a species' response to fishing pressure, ocean warming).

The Bellingshausen and Amundsen Seas are among the least studied Antarctic areas. Pycnogonids constitute a common and conspicuous component of the Antarctic marine fauna. Antarctic pycnogonids have been widely studied and are usually more abundant than elsewhere. Therefore, they represent a key taxon to understand the zoogeographic and bathymetric distributions of the fauna from these two poorly sampled seas. Furthermore, we aim to compare the diversity and composition of the pycnogonids in these areas with those in other Antarctic zones. Three main surveys were carried out in these regions ( Bentart 2003 and 2006 and Biopearl II 2008 ). In total, 879 pycnogonids belonging to 65 species were recorded in 49 stations. Two new species are described: Heteronymphon krappi n.sp. and Nymphon nakamurai n.sp. Ammothea magniceps and A. hesperidensis are recorded for the second time in the Antarctic. The most abundant family is the Nymphonidae (60.5 %), and Nymphon australe is the most abundant species (25.5 %). The biogeographic analysis revealed 39 species in the Bellingshausen Sea (16 new records) and 19 species in the Amundsen Sea (18 new records). The circumpolar pattern is the most common found. The Bellingshausen Sea seems to be a poor area in terms of abundance and species richness compared to the Amundsen Sea and other Antarctic zones. Faunal similarity was clustered into three main groups: the shallow-water stations, the outer continental shelf stations and the slope stations. The abundance of individuals likely responds to the varying amount of organic matter that reaches each bathymetric zone.