Multiple paternity and hybridization in two smooth-hound sharks

Multiple paternity appears to be a common trait of elasmobranch mating systems, with its occurrence likely driven by convenience, due to females seeking to minimize the stress of male harassment. Here we use molecular markers to analyse the frequency of multiple paternity in two related viviparous sharks, Mustelus mustelus and Mustelus punctulatus. We first applied molecular methods to assign pregnant females, embryos and additional reference adults (N\u2009=\u2009792) to one of the two species. Paternity analysis was performed using a total of 9 polymorphic microsatellites on 19 females and 204 embryos of M. mustelus, and on 13 females and 303 embryos of M. punctulatus. Multiple paternity occurs in both species, with 47% of M. mustelus and 54% of M. punctulatus litters sired by at least two fathers. Female fecundity is not influenced by multiple mating and in 56% of polyandrous litters paternity is skewed, with one male siring most of the pups. Genetic analyses also revealed hybridization between the two species, with a M. punctulatus female bearing pups sired by a M. mustelus male. The frequency of polyandrous litters in these species is consistent with aspects of their reproductive biology, such as synchronous ovulation and possible occurrence of breeding aggregations

Reproductive traits and age of barbeled plunderfishes from the Weddell Sea

AbstractThe genus Pogonophryne is the most species-rich genus of barbeled plunderfishes (Artedidraconidae) and includes more than 25 poorly known species endemic to the Southern Ocean. In this study, we provide new data on the age and reproductive traits of some species of Pogonophryne from the southern Weddell Sea, inferred through otolith reading and histological analyses of gonads. Individual age estimates ranged between 16 and 18 years for Pogonophryne barsukovi and Pogonophryne immaculata and between 10 and 22 years for Pogonophryne scotti. As is commonly found in notothenioids, P. barsukovi followed a group-synchronous type of ovarian development, with pre-vitellogenic and vitellogenic oocytes forming two well-separated egg-size groups. A single spawning female in the sample produced ~1097 eggs and 7.9 eggs g-1. The sample of P. immaculata consisted exclusively of developing males, with testes composed of cysts of spermatogonia, spermatocytes and spermatids. Pogonophryne scotti was the most abundant species, including relatively small males at immature or developing stages of gonad development. Larger females were regressing, being characterized by ovaries with postovulatory follicles and atretic oocytes. Based on the macroscopic and histological analyses of gonads, the spawning season would take place in autumn for P. barsukovi and P. immaculata and in spring–early summer for P. scotti

Spatial distribution and habitat preferences of demersal fish assemblages in the southeastern Weddell Sea (Southern Ocean)

Our knowledge on distribution, habitats and behavior of Southern Ocean fishes living at water depths beyond scuba-diving limits is still sparse, as it is difficult to obtain quantitative data on these aspects of their biology. Here, we report the results of an analysis of seabed images to investigate species composition, behavior, spatial distribution and preferred habitats of demersal fish assemblages in the southern Weddell Sea. Our study was based on a total of 2736 high-resolution images, covering a total seabed area of 11,317 m2, which were taken at 13 stations at water depths between 200 and 750 m. Fish were found in 380 images. A total of 379 notothenioid specimens were recorded, representing four families (Nototheniidae, Artedidraconidae, Bathydraconidae, Channichthyidae), 17 genera and 25 species. Nototheniidae was the most speciose fam- ily, including benthic species (Trematomus spp.) and the pelagic species Pleuragramma antarctica, which was occasionally recorded in dense shoals. Bathydraconids ranked second with six species, followed by artedidraconids and channichthyids, both with five species. Most abundant species were Trematomus scotti and T. lepidorhinus among nototheniids, and Dol- loidraco longedorsalis and Pagetopsis maculatus among artedidraconids and channichthyids, respectively. Both T. lepi- dorhinus and P. maculatus preferred seabed habitats characterized by biogenous debris and rich epibenthic fauna, whereas T. scotti and D. longedorsalis were frequently seen resting on fine sediments and scattered gravel. Several fish species were recorded to make use of the three-dimensional structure formed by epibenthic foundation species, like sponges, for perching or hiding inside. Nesting behavior was observed, frequently in association with dropstones, in species from various families, including Channichthyidae (Chaenodraco wilsoni and Pagetopsis macropterus) and Bathydraconidae (Cygnodraco mawsoni)

Limited interspecific gene flow in the evolutionary history of the icefish genus Chionodraco

Hybridization and introgression are recognized as mechanisms promoting genetic variability during evolutionary radiations. We examined the impact of introgression in the process of speciation, focusing on the Antarctic icefish genus Chionodraco. Our analyses confirmed that the three Chionodraco species (Chionodraco hamatus, Chionodraco myersi, and Chionodraco rastrospinosus) were genetically distinctive, despite signals of past interspecific gene flow between C. hamatus and C. myersi that likely occurred during interglacial periods. However, in this study, no recent hybrids were identified. The lack of contemporary hybridization may be due to life-history traits and the type of marker used in the analysis. Our study emphasizes the importance of genomic approaches to detect subtle patterns of past hybridization accurately and highlights the significance of historical climate events in the demographic and evolutionary history of Antarctic notothenioids. Polar regions, and especially the Antarctic Peninsula, are now experiencing the fastest climate changes due to global warming. Understanding the impact of past climate events is fundamental to trace current modifications in species' genetic variability and distributions and predict future evolutionary trajectories. This knowledge is also vital for conservation efforts, including the implementation of marine protected areas

Life histories and evolution: insights from notothenioids (Teleostei, Perciformes)

ABSTRACT Organisms show an extraordinary variation in their life history traits, both at inter- and intraspecific level, exhibiting phenotypic variations among populations inhabiting different habitat. The variability in life history traits has been related to environmental conditions, as a result of selective processes or phenotypic response to them. In addition to the huge diversity in life history traits, several trade-offs among them have been recognized. The variability in life history traits and in their trade-offs related to environmental conditions represents a key aspect in the study of evolutionary processes. A wide variation in life history traits is documented among teleost fishes, both among and within species, reflecting the effects of evolutionary forces acting on them over time and across environmental conditions. Several life history traits, such as growth rate, age at sexual maturity, fecundity, reproductive investment, egg size, hatching size, are strongly influenced by temperature and food availability. Notothenioid fish represent a unique example of fish adaptive radiation in marine environment. They dominate the waters surrounding the Antarctic continent both by species number, with over 120 species (47%), and biomass (90-95%). Notothenioids distribution is limited exclusively to the Antarctic and sub-Antarctic regions (South America, New Zealand and South East Australia). Variability in their life history traits at inter- and intra-specific levels has been described, with a latitudinal trends in some reproductive traits. In this framework, despite the availability of recent phylogenies of notothenioids, a comparative analysis aimed at studying habitat dependent evolution of reproductive strategies has not yet been performed. Given the particular characteristics of their habitats and the uniqueness of notothenioid fishes, they can be considered an excellent taxon model to investigate the evolution of life history traits in relation to environmental factors. The aim of this PhD project was to investigate the evolution of life history traits of notothenioid species in relation to environmental variables (such as sea water temperature, primary productivity and sea ice cover), controlling for phylogenetic relationships. The applied methodology (Independent Contrast Method) represents a key aspect in this study since its robustness can prevent the attribution of correlations between life history traits and environmental variables to evolutionary processes, being instead a consequence of phylogenetic relationships among considered species. Using life history traits estimated from collected species and reported in data available in literature, the study focused the attention on gametogenesis and, gonadal investment, such as fecundity and egg size. Such a comparative study of habitat dependent variation of life history traits is interesting for evolutionary biology, given the extreme adaptations shown by Antarctic fishes to their peculiar environment, as well as for conservation biology, because the knowledge of reproductive traits and of their sensitiveness to environmental changes is recognized as a crucial information for the sustainable management of exploited species and their resilience capacity to overcome current climate change. In the present research, life history traits of 17 species, belonging the eight notothenioid families were investigated (Papers I, II, III, IV, V, VI), providing original information on their biology and strengthening the reliability of the available literature. Intraspecific variability in life history traits was examined in three species, including in the analyses specimens sampled in different areas (Papers I, III and IV). Unpublished life history traits data of 15 species were included in the interspecific comparison (Paper VI). Species included in this study were collected during two cruises carried out onboard the German R/V Polarstern (ANT-XXVIII/4, 2012 and ANT-XXIX/9, 2014) off the Antarctic Peninsula and in the Weddell Sea. Samples, belonging to four notothenioid species, were provided by partner scientists during past Antarctic expeditions (2009, 2010 and 2011 during the austral summer) in different areas (i.e. South Orkney, South Georgia, Burdwood Bank and Western Antarctic Peninsula). Comparing the results obtained in studies dealing with individual species, the histological analyses generally indicated some similarities among notothenioids. In all the analysed species, females presented a group synchronous ovarian type, in which two clearly distinct groups of oocytes were visible. The more advanced stage of maturity in maturing or mature females were oocytes at late stage of vitellogenesis, constituting the batch of the current season, while the other group included oocytes at the cortical alveoli or previtellogenic stages, representing the next year batch. The occurrence of late vitellogenic oocytes together with others at the cortical alveoli stage supports a prolonged oogenesis, likely lasting more than one year. Testes were of the unrestricted spermatogonial testicular type. In mature males, testes were completely filled with sperm with few cysts of early-stages of spermatogenesis, indicating that sperm maturation completes before the beginning of the breeding season. Long lasting gametogenesis is likely related to the low temperature and to the high reproductive investment. The study on individual species provided new data on absolute and relative fecundity, egg size, gonadosomatic index (GSI) and age estimates and therefore information useful for the comparative analyses (Paper VI). By means of age estimates through otolith reading, growth rate, age/length relationship, maximum age and age at sexual maturity were assessed (Papers II, III, IV, V). As expected for cold water fish species, notothenioids exhibit slow growth rate, late sexual maturity (at about 50-87% of maximum size) and long life span (up to 24 years). The intraspecific comparison highlighted that the observed variation in life history traits could be addressed to local conditions (i.e. local prevailing currents linked to cold water masses and melting ice) and/or be a consequence of the species reproductive habits, including egg type, presence/absence of parental care, adult distribution and mobility. In Chaenocephalus aceratus, a benthic species with demersal eggs and parental care, fecundity was higher in the warmer study area, that is not influenced by cold water masses coming from Weddell Sea, respect to the colder area. In the Antarctic silverfish (Pleuragramma antarctica), the only species lying cryopelagic eggs (i.e. eggs laid to the lower surface of platelet pack ice), and in Notothenia rossii, in which individuals shift from benthic to bentho-pelagic habits achieving the adult phase, no differences emerged between populations, with the exception of some differences in oocyte size and GSI, likely related to temporal differences in sampling periods. The results of the interspecific comparative analyses highlighted some correlation between environmental factors and life history traits, revealing potential evolutionary forces. Differently from the other biological traits considered in this study, the maximum size did not correlate with any environmental variable. These results support the observation that the Bergmann’s rule, describing the occurrence of a positive relationship between maximum size and latitude, with larger specimens found in colder environments (higher latitudes), does not apply at high latitudes. In notothenioids egg size was negatively related to primary production. Primary production, in turn, is negatively related to latitude, and general theoretical models and relevant studies indicate a positive relationship between egg size and latitude. Food availability and temperature have been claimed as factors driving the general increasing trend in egg size with latitude. Primary production can be considered a proxy of food availability, therefore in notothenioids food availability appears to be the main factor influencing egg size. A positive relationship between egg and larval size is common, and larger larvae are expected to show enhanced competitive abilities, improved capacity to feed on a wide size range of prey items and enhanced starvation resistance, and ultimately higher survival probabilities in extreme conditions. Egg size is also positively related to the maximum parental body size. Generally, large fishes, as for instance tunas or the Ocean sunfish Mola mola, are not more likely to have large eggs than small ones, nonetheless fish size may indeed constrain, rather than determine, the range of possible egg sizes, as suggested also by the results on notothenioids. Large notothenioids could therefore have a wider range of tactics in the partition of reproductive effort between fecundity and egg size. While Low Antarctic species produce small and large eggs, High Antarctic species present only large eggs. Considering the trade-off between egg size and number, a positive relationship between relative fecundity (i.e. the number of eggs in relation to body weight) and primary production was expected but it was not found. Conversely a positive relationship was observed between relative fecundity and mean water temperature, although it remains an unsolved issue which need to be further investigated. Energetic investment in female reproductive effort, i.e. maximum female GSI, showed a positive relationship with sea ice cover. Seasonal pack ice melting, occurring in summer at intermediate Antarctic latitudes, triggers phytoplankton blooms, resulting in an increased primary production with a cascading effect on the pelagic food web. At higher latitudes, where maximum values of GSI have been detected, the sea ice cover is permanent through the year and the primary production is likely to remain low, being also influenced by the long and dark Antarctic winter. These extreme conditions may therefore trigger a higher investment in reproduction, including the investment in eggs (size and/or number) represented by the female GSI. The insights provided by this study shed light on the major factors that appear to drive the evolutionary processes occurring in the Antarctic environment. The comparative method proved to be a robust tool in investigating adaptive response to different environmental conditions. Despite notothenioids demonstrated to be an excellent model group to study evolutionary process, further investigations, extending to other taxa and species geographical distributions, are necessary to trace more general and comprehensive patterns in the evolution of life history traits. In any case, shared reproductive features such as low fecundity, large egg size, high reproductive investment in gonads and, in some cases, in parental care, low growth rate and late sexual maturity, depict notothenioids as a taxon highly vulnerable to climate change and fishery re-opening scenarios.RIASSUNTO Gli organismi presentano un’enorme diversità nelle caratteristiche del loro ciclo biologico, sia a livello intra- che interspecifico, mostrando differenze tra popolazioni che vivono in habitat diversi. Tale variabilità fenotipica nel ciclo biologico, è stata messa in relazione all’influenza dei fattori ambientali, e rappresenta il risultato della selezione naturale. Uno degli aspetti chiave dello studio dei processi che hanno portato all’evolversi di queste differenze è cercare di comprendere quali siano le variabili ambientali che influenzano la variabilità dei tratti del ciclo biologico e le relazioni che tra di loro intercorrono. Diversi studi hanno messo in luce come la temperatura e la disponibilità trofica sembrano essere i parametri che meglio spiegano l’andamento dei diversi tratti come i tassi di crescita, l’età alla maturità sessuale, la fecondità, l’investimento riproduttivo, le dimensioni delle uova e delle larve. I pesci del Sottordine Notothenioidea rappresentano un esempio unico di radiazione adattativa in ambiente marino, dominano le acque che circondano il continente antartico sia nel numero di specie, superando le 120 (47%), che in biomassa (90-95%). Durante la loro evoluzione, i nototenioidei hanno subito una profonda diversificazione di alcuni caratteri, adattandosi alle nicchie ecologiche disponibili. Le rigide condizioni dell’ambiente antartico hanno contribuito a differenziare i pesci antartici dalle altre specie ittiche, rallentandone i ritmi di crescita, modificando gli aspetti riproduttivi, lo sviluppo larvale e l’ecologia. I nototenioidei sono distribuiti esclusivamente nell’Oceano Meridionale e in aree sub-antartiche quali Sud America, Nuova Zelanda e le coste più a sud-est dell’Australia. È stata descritta una notevole variabilità dei tratti del ciclo biologico tra specie e tra popolazioni della stessa specie, legata alle diverse condizioni ambientali a cui sono sottoposti gli individui. Con queste premesse, pur essendo disponibili filogenesi recenti ed aggiornate dei pesci nototenioidei, non sono mai stati applicati metodi comparativi che, tenendo conto delle relazioni filogenetiche, permettano di valutare il peso dei diversi fattori ambientali sull’evoluzione delle diverse strategie riproduttive. L’obiettivo del progetto di dottorato è stato di indagare la variabilità di alcuni tratti del ciclo biologico di specie di nototenioidei in relazione alle variabili ambientali, quali la temperatura dell’acqua, la produttività primaria e la copertura del ghiaccio. Il metodo dei contrasti indipendenti, utilizzato per controllare per le relazioni filogenetiche, rappresenta un punto di forza poiché permette di eliminare la dipendenza dei dati ed evitare quindi possibili relazioni dovute alla storia evolutiva delle specie piuttosto che a reali adattamenti evolutivi. La ricerca ha previsto lo studio della biologia delle specie campionate e la raccolta di dati da letteratura, prendendo in esame lo sviluppo dei gameti, l’investimento gonadico, la fecondità e le dimensioni degli ovociti. I risvolti del presente lavoro sono interessanti sia da un punto di vista della biologia evoluzionistica, per il peculiare adattamento mostrato dai nototenioidei nel loro ambiente, che conservazionistico, poiché la conoscenza dei tratti riproduttivi e della loro risposta ai cambiamenti ambientali è fondamentale per una efficace gestione sostenibile delle specie sfruttate dalla pesca e per valutare la loro capacità di resilienza a superare i cambiamenti climatici in corso. Infatti, alcune specie tra i nototenioidei, sono state soggette in passato a forte pressione di pesca che, in pochi anni, ha portato al collasso degli stock ittici. Nella presente ricerca sono stati studiati i tratti del ciclo biologico di 17 specie appartenenti a tutte le otto famiglie di nototenioidei (Papers I, II, III, IV, V e VI), fornendo informazioni nuove sulla biologia delle specie e rafforzando quelle disponibili in letteratura. La variabilità intraspecifica nei tratti del ciclo biologico è stata valutata in tre specie grazie alla disponibilità di campioni provenienti da popolazioni di aree diverse (Papers I, III e IV). I dati ottenuti dall’analisi delle singole specie, sono stati quindi utilizzati per il confronto interspecifico (Paper VI). I campioni disponibili sono stati raccolti durante due spedizioni antartiche a bordo della nave tedesca R/V Polarstern (ANT-XXVIII/4, 2012 e ANT-XXIX/9, 2014), lungo la Penisola Antartica e nel Mare di Weddell. Ulteriori campioni di quattro specie, provenienti da diverse aree (South Orkney, South Georgia, Burdwood Bank e versante ovest della Penisola Antartica) sono stati forniti da collaboratori di ricerca. I risultati ottenuti dallo studio sulle singole specie permettono di evidenziare delle caratteristiche comuni tra i nototenioidei. In tutte le specie analizzate, le femmine hanno presentato un ovario sincrono per gruppi in cui è possibile distinguere nettamente due classi dimensionali di ovociti. Le femmine sessualmente mature hanno mostrato ovociti in fase avanzata di vitellogenesi, che verranno deposti nella stagione riproduttiva in corso, e ovociti in stadio di alveoli corticali o previtellogenetici, che matureranno per l’evento riproduttivo dell’anno successivo. La presenza contemporanea di ovociti in stadio avanzato di vitellogenesi, insieme ad altri allo stadio di alveoli corticali, evidenzia un’ovogenesi di lunga durata, verosimilmente, superiore ad un anno. I testicoli sono stati descritti come di tipo lobulare unrestricted e, in individui sessualmente maturi, hanno mostrato la presenza di spermatozoi nei dotti e spermatogoni localizzati soprattutto nella parte distale. Inoltre, è emerso come il processo di maturazione degli spermatozoi sia completo prima dell'inizio del periodo di riproduzione. È possibile quindi affermare che anche la spermatogenesi, come l’ovogenesi, è un processo molto lungo e, in generale, la lunga e lenta gametogenesi osservata è probabilmente correlata alla bassa temperatura e all'alto investimento riproduttivo dei nototenioidei. Lo studio della biologia delle specie ha fornito nuove informazioni sulla fecondità (assoluta e relativa), sulle dimensioni degli ovociti e sull’indice gonadosomatico (IGS), informazioni poi utilizzate per le analisi comparative (Paper VI). La stima dell’età, attraverso la lettura degli otoliti, ha permesso di valutare il tasso di crescita, la relazione tra la taglia e l’età, l’età massima e quella alla maturità sessuale (Papers II, III, IV, V). I risultati seguono le attese, infatti, come descritto in specie di acque fredde, i nototenioidei mostrano lento accrescimento, raggiungimento tardivo della maturità sessuale (circa 50-87% rispetto alla lunghezza massima) e longevità media (fino a 24 anni). Dal confronto intraspecifico emerge come la variabilità osservata nei tratti del ciclo biologico, possa essere attribuita a fattori ambientali che agiscono su piccola scala, come ad esempio correnti fredde dovute allo scioglimento del ghiaccio e/o a caratteristiche biologiche tipiche della specie. Infatti, il tipo di uova (pelagiche o demerse), la presenza o meno di cure parentali, la distribuzione degli individui adulti e la mobilità della specie, possono avere un ruolo chiave nell’influenzare l’areale di distribuzione e di dispersione di una specie. Il confronto tra le due popolazioni dell’icefish Chaenocephalus aceratus, una specie bentonica a bassa mobilità, con uova demersali e presenza di cure parentali, ha dimostrato una fecondità più alta nell’area con temperatura dell’acqua più elevata e che non risente delle correnti fredde che si originano nel Mare di Weddell. Non emergono, invece, differenze intraspecifiche nei tratti riproduttivi in Pleuragramma antarctica, una specie pelagica, con uova cryopelagiche (cioè deposte sotto lo strato di ghiaccio stagionale) e in Notothenia rossii, dove i lunghi tempi di incubazione delle uova pelagiche e della fase larvale, sembrano assicurare connettività tra le aree investigate. In generale le discrepanze emerse in termini di dimensioni degli ovociti e IGS, sono probabilmente legate a differenze temporali nei periodi di campionamento. Le analisi comparative a livello interspecifico hanno evidenziato relazioni tra fattori ambientali e tratti del ciclo biologico. La taglia massima, a differenza degli altri tratti considerati, non ha presentato nessuna relazione con le variabili ambientali. Sembra quindi che la regola di Bergmann, che descrive la relazione positiva tra taglia massima e latitudine, con individui più grandi in ambienti più freddi (latitudini più alte), non sia applicabile alle alte latitudini. Nei nototenioidei è emersa una tendenza significativa a produrre ovociti più grandi al diminuire della produttività primaria, che raggiunge i valori minimi procedendo verso il Polo, sebbene presenti variabilità stagionale. A livello interspecifico, quindi, si osservano ovociti di maggiori dimensioni in specie che occupano alte latitudini, a conferma di quanto precedentemente previsto dai modelli teorici generali e dimostrato in diversi studi sperimentali. I principali fattori ambientali individuati come possibili responsabili del generale aumento delle dimensioni degli ovociti con la latitudine sono la disponibilità di cibo e la temperatura. In questo caso, nei nototenioidei, sembra avere maggior influenza la disponibilità di cibo, considerando che la produttività primaria può esserne una misura. Inoltre, comunemente, da uova più grandi schiudono larve di maggiori dimensioni, che dovrebbero mostrare quindi migliori abilità competitive, capacità di nutrirsi di prede di diverse dimensioni e una maggiore resistenza alla carenza di cibo. Complessivamente queste caratteristiche dovrebbero garantire un’elevata probabilità di sopravvivenza delle larve in condizioni di risorse alimentari limitanti. Inoltre, la dimensione degli ovociti aumenta al crescere della taglia massima. In termini generali, però, i pesci di grande taglia non mostrano una tendenza a produrre necessariamente uova grandi, basti pensare a pesci di notevoli dimensioni, come il tonno e il pesce luna, che depongono uova molto piccole. Sembra quindi che la taglia corporea finisca più per limitare il range di dimensioni delle uova in pesci di piccola taglia, piuttosto che determinare, la dimensione massima delle uova che una specie può produrre. Questo emerge anche dai risultati ottenuti per i nototenioidei, dove le specie di maggiori dimensioni, hanno a disposizione una maggior gamma di combinazioni per ripartire lo sforzo riproduttivo, tra qualità in termini di dimensioni e quantità degli ovociti. Le specie distribuite alle basse latitudini antartiche producono ovociti sia piccoli che gran

Life histories and evolution: insights from notothenioids (Teleostei, Perciformes)

ABSTRACT Organisms show an extraordinary variation in their life history traits, both at inter- and intraspecific level, exhibiting phenotypic variations among populations inhabiting different habitat. The variability in life history traits has been related to environmental conditions, as a result of selective processes or phenotypic response to them. In addition to the huge diversity in life history traits, several trade-offs among them have been recognized. The variability in life history traits and in their trade-offs related to environmental conditions represents a key aspect in the study of evolutionary processes. A wide variation in life history traits is documented among teleost fishes, both among and within species, reflecting the effects of evolutionary forces acting on them over time and across environmental conditions. Several life history traits, such as growth rate, age at sexual maturity, fecundity, reproductive investment, egg size, hatching size, are strongly influenced by temperature and food availability. Notothenioid fish represent a unique example of fish adaptive radiation in marine environment. They dominate the waters surrounding the Antarctic continent both by species number, with over 120 species (47%), and biomass (90-95%). Notothenioids distribution is limited exclusively to the Antarctic and sub-Antarctic regions (South America, New Zealand and South East Australia). Variability in their life history traits at inter- and intra-specific levels has been described, with a latitudinal trends in some reproductive traits. In this framework, despite the availability of recent phylogenies of notothenioids, a comparative analysis aimed at studying habitat dependent evolution of reproductive strategies has not yet been performed. Given the particular characteristics of their habitats and the uniqueness of notothenioid fishes, they can be considered an excellent taxon model to investigate the evolution of life history traits in relation to environmental factors. The aim of this PhD project was to investigate the evolution of life history traits of notothenioid species in relation to environmental variables (such as sea water temperature, primary productivity and sea ice cover), controlling for phylogenetic relationships. The applied methodology (Independent Contrast Method) represents a key aspect in this study since its robustness can prevent the attribution of correlations between life history traits and environmental variables to evolutionary processes, being instead a consequence of phylogenetic relationships among considered species. Using life history traits estimated from collected species and reported in data available in literature, the study focused the attention on gametogenesis and, gonadal investment, such as fecundity and egg size. Such a comparative study of habitat dependent variation of life history traits is interesting for evolutionary biology, given the extreme adaptations shown by Antarctic fishes to their peculiar environment, as well as for conservation biology, because the knowledge of reproductive traits and of their sensitiveness to environmental changes is recognized as a crucial information for the sustainable management of exploited species and their resilience capacity to overcome current climate change. In the present research, life history traits of 17 species, belonging the eight notothenioid families were investigated (Papers I, II, III, IV, V, VI), providing original information on their biology and strengthening the reliability of the available literature. Intraspecific variability in life history traits was examined in three species, including in the analyses specimens sampled in different areas (Papers I, III and IV). Unpublished life history traits data of 15 species were included in the interspecific comparison (Paper VI). Species included in this study were collected during two cruises carried out onboard the German R/V Polarstern (ANT-XXVIII/4, 2012 and ANT-XXIX/9, 2014) off the Antarctic Peninsula and in the Weddell Sea. Samples, belonging to four notothenioid species, were provided by partner scientists during past Antarctic expeditions (2009, 2010 and 2011 during the austral summer) in different areas (i.e. South Orkney, South Georgia, Burdwood Bank and Western Antarctic Peninsula). Comparing the results obtained in studies dealing with individual species, the histological analyses generally indicated some similarities among notothenioids. In all the analysed species, females presented a group synchronous ovarian type, in which two clearly distinct groups of oocytes were visible. The more advanced stage of maturity in maturing or mature females were oocytes at late stage of vitellogenesis, constituting the batch of the current season, while the other group included oocytes at the cortical alveoli or previtellogenic stages, representing the next year batch. The occurrence of late vitellogenic oocytes together with others at the cortical alveoli stage supports a prolonged oogenesis, likely lasting more than one year. Testes were of the unrestricted spermatogonial testicular type. In mature males, testes were completely filled with sperm with few cysts of early-stages of spermatogenesis, indicating that sperm maturation completes before the beginning of the breeding season. Long lasting gametogenesis is likely related to the low temperature and to the high reproductive investment. The study on individual species provided new data on absolute and relative fecundity, egg size, gonadosomatic index (GSI) and age estimates and therefore information useful for the comparative analyses (Paper VI). By means of age estimates through otolith reading, growth rate, age/length relationship, maximum age and age at sexual maturity were assessed (Papers II, III, IV, V). As expected for cold water fish species, notothenioids exhibit slow growth rate, late sexual maturity (at about 50-87% of maximum size) and long life span (up to 24 years). The intraspecific comparison highlighted that the observed variation in life history traits could be addressed to local conditions (i.e. local prevailing currents linked to cold water masses and melting ice) and/or be a consequence of the species reproductive habits, including egg type, presence/absence of parental care, adult distribution and mobility. In Chaenocephalus aceratus, a benthic species with demersal eggs and parental care, fecundity was higher in the warmer study area, that is not influenced by cold water masses coming from Weddell Sea, respect to the colder area. In the Antarctic silverfish (Pleuragramma antarctica), the only species lying cryopelagic eggs (i.e. eggs laid to the lower surface of platelet pack ice), and in Notothenia rossii, in which individuals shift from benthic to bentho-pelagic habits achieving the adult phase, no differences emerged between populations, with the exception of some differences in oocyte size and GSI, likely related to temporal differences in sampling periods. The results of the interspecific comparative analyses highlighted some correlation between environmental factors and life history traits, revealing potential evolutionary forces. Differently from the other biological traits considered in this study, the maximum size did not correlate with any environmental variable. These results support the observation that the Bergmann’s rule, describing the occurrence of a positive relationship between maximum size and latitude, with larger specimens found in colder environments (higher latitudes), does not apply at high latitudes. In notothenioids egg size was negatively related to primary production. Primary production, in turn, is negatively related to latitude, and general theoretical models and relevant studies indicate a positive relationship between egg size and latitude. Food availability and temperature have been claimed as factors driving the general increasing trend in egg size with latitude. Primary production can be considered a proxy of food availability, therefore in notothenioids food availability appears to be the main factor influencing egg size. A positive relationship between egg and larval size is common, and larger larvae are expected to show enhanced competitive abilities, improved capacity to feed on a wide size range of prey items and enhanced starvation resistance, and ultimately higher survival probabilities in extreme conditions. Egg size is also positively related to the maximum parental body size. Generally, large fishes, as for instance tunas or the Ocean sunfish Mola mola, are not more likely to have large eggs than small ones, nonetheless fish size may indeed constrain, rather than determine, the range of possible egg sizes, as suggested also by the results on notothenioids. Large notothenioids could therefore have a wider range of tactics in the partition of reproductive effort between fecundity and egg size. While Low Antarctic species produce small and large eggs, High Antarctic species present only large eggs. Considering the trade-off between egg size and number, a positive relationship between relative fecundity (i.e. the number of eggs in relation to body weight) and primary production was expected but it was not found. Conversely a positive relationship was observed between relative fecundity and mean water temperature, although it remains an unsolved issue which need to be further investigated. Energetic investment in female reproductive effort, i.e. maximum female GSI, showed a positive relationship with sea ice cover. Seasonal pack ice melting, occurring in summer at intermediate Antarctic latitudes, triggers phytoplankton blooms, resulting in an increased primary production with a cascading effect on the pelagic food web. At higher latitudes, where maximum values of GSI have been detected, the sea ice cover is permanent through the year and the primary production is likely to remain low, being also influenced by the long and dark Antarctic winter. These extreme conditions may therefore trigger a higher investment in reproduction, including the investment in eggs (size and/or number) represented by the female GSI. The insights provided by this study shed light on the major factors that appear to drive the evolutionary processes occurring in the Antarctic environment. The comparative method proved to be a robust tool in investigating adaptive response to different environmental conditions. Despite notothenioids demonstrated to be an excellent model group to study evolutionary process, further investigations, extending to other taxa and species geographical distributions, are necessary to trace more general and comprehensive patterns in the evolution of life history traits. In any case, shared reproductive features such as low fecundity, large egg size, high reproductive investment in gonads and, in some cases, in parental care, low growth rate and late sexual maturity, depict notothenioids as a taxon highly vulnerable to climate change and fishery re-opening scenarios

The Clodia database: a long time series of fishery data from the Adriatic Sea

Long-term time series of species abundances can depict population declines and changes in communities in response to anthropogenic activities, climate changes, alterations of trophic relationships. Here we present a database of historical marine fishery landing data, covering a remarkably long time series (1945–2013) and referring to one of the most exploited areas of the Mediterranean Sea, the Adriatic Sea. The database includes two time series of landing data, 1945–2013 and 1997–2013, from the official statistics of the fish market of Chioggia, where the major fishing fleet of the area operates. Comparisons between the landing data of the database and landing data from other fisheries or data from scientific surveys support the reliability of the time series in depicting changes in species abundances. The database is expected to be used by fishery biologists and ecologists interested in depicting and understanding temporal variations in species abundances and community composition, in relation to environmental and anthropogenic factors

Gain or Loss for the Inshore Trawling Ban within Three Miles? Preliminary Data

From 1 June 2010 in the Italian coastal waters of the Northern Adriatic Sea, trawl fishery within three nautical miles became banned. This activity was previously allowed for some species as an exception to legislation. In order to evaluate the consequences both on demersal resources and economic yields of the trawl which will oblige fishermen to trawl beyond three miles, a pilot study was performed. Twenty hauls comparing catch discard and income between hauls within and external to three nautical miles were performed. Results highlighted differences in catch composition both for landing and discard. Landing per unit of effort and discard per unit of effort did not differ in relation to distance from the coast, while income was higher for offshore hauls than inshore ones even if not significantly. Fishery management is a complex task, and the results of this study can contribute to the debate providing new insights into the consequences of the regulation on the trawling within three nautical miles. Considering the high amounts of discard, the habitat damages caused by otter trawling, the presence of juveniles in coastal waters and data regarding fishermen income, this study supports the actual European Community regulation on coastal trawling

Fisherman cooperation: the key for a successful conservation

Artisanal fishery often offers the best opportunities for impact mitigation but it\u2019s also the most traditional and difficult to change. Trap fishery, an artisanal method that targets cuttlefish spawning adults in spring, exploits cuttlefish female attraction to traps for egg laying. The present study estimated the impact of traps on cuttlefish eggs and tested the efficacy and suitability of a management measure to mitigate this impact in the Northern Adriatic Sea. Results showed that over 3 millions of eggs, in less than 3 miles of coast, are likely destroyed by this fishery. The use of ropes, attached inside traps, allowed to collect on average 23.7% of the eggs, without affecting catch rate of adults. The efficacy of this mitigation measure is discussed considering fishermen attitude towards it