1,720,973 research outputs found
Habitat use in juvenile and adult life stages of the sedentary fish Hippocampus guttulatus
Full text linkUnderstanding of the spatial distribution and habitat use in different stages of a life cycle represents the essential aspect of threatened species management and conservation. In the present paper, the spatial and temporal patterns of habitat use in juvenile and adult life stages of the long-snouted seahorse Hippocampus guttulatus in the Mar Piccolo of Taranto (Apulia—Italy) (40°28′N, 17°16′W) were examined. From October 2012 to January 2014, monthly visual censuses were conducted in six coastal habitats of a focal area (Buffoluto site). Of a total of 317 individuals of the long-snouted seahorse that were sighted, 148 were juveniles, 82 adult females and 87 adult males. Our results showed significant differences in the habitat use between adult and juvenile life stages of H. guttulatus. Adult individuals were mainly concentrated within Cladophora prolifera beds and the wood poles of a mussel farm at 2–4 m of depth, while juvenile individuals were mainly present in shallower water (0.4–1 m) on artificial hard substrates covered by a brown algae turf. Assessing and describing the habitat use within different life stages of H. guttulatus represent a useful tool to support species conservation by protecting the habitats it uses
Different behavioral strategies of two sympatric seahorses: habitat availability and increased density of Hippocampus guttulatus alter the behavior of Hippocampus hippocampus
Full text linkIn the light of future ocean warming scenarios and habitat fragmentation, coastal fishes must adjust their physiological and behavioral traits to face the combined effect of global warming and ecological interactions. Seahorses (Hippocampus spp.) are charismatic fishes with peculiar life cycle traits, which make them vulnerable to several anthropic pressures and natural disturbances. In this study, we investigated the behavior of two sympatric seahorse species, the long-snouted Hippocampus guttulatus (Cuvier, 1829) and the short-snouted Hippocampus hippocampus (Linnaeus, 1758). Specifically, we carried out two manipulative experiments to assess (i) the effect of temperature and habitat availability on both H. hippocampus and H. guttulatus behavior and (ii) the effect of temperature and an increased density of H. guttulatus (by 3x) on the activity level of congeneric species H. hippocampus. Our results showed that +3 & DEG;C warming did not affect seahorse behavior in both experiments, suggesting greater behavioral tolerance to thermal variation. However, a significant reduction of the active behavior of H. hippocampus was observed when the artificial habitat was introduced in the tank, while H. guttulatus maintained its activity. Furthermore, a significant decrease of the H. hippocampus activity was observed with an increased relative dominance of H. guttulatus. Our results suggest that both increased density of H. guttulatus and habitat availability, but not ocean warming, will affect the behavior of H. hippocampus. Therefore, different interspecific behavioral strategies may occur, thus affecting the distribution of the two species among shallow habitats when they occur in sympatry.LA/P/0101/2020info:eu-repo/semantics/publishedVersio
Trophic flexibility and prey selection of the wild long-snouted seahorse Hippocampus guttulatus Cuvier, 1829 in three coastal habitats
Full text linkThe present study examined the dietary composition of long-snouted seahorse H. guttulatus Cuvier, 1829 in Mar Piccolo of Taranto (Apulia, Italy)using a non-destructive flushing method. To assess differences in the selection of prey among different habitats, adult specimens were collected from both highly complex (Cladophora prolifera and Corallina elongata)and low complex (unvegetated Sandy bottom)habitats. Additionally, samples of benthic fauna were collected from the same habitats and were used to investigate the local availability of potential preys. Results showed significant differences in the diet composition among three studied habitats. Consistently with the results of faunal analysis, gut contents of specimens sampled on C. elongata had higher prey abundance and diversity compared to the other two habitats. Dietary composition of seahorses found in the vegetated habitats was similar, and it was mainly based on Amphipoda and Copepoda. However, small prey (<1 mm)was more consumed on C. elongata than on C. prolifera. On the sandy bottom, H. guttulatus preyed mainly on small crustaceans, but actively selected larger prey (i.e. Galathoidea and Paguroidea). Nematodes were also highly preyed in all habitats, although the high consumption could be possibly attributed to the high abundance and availability of these organisms at the investigated site. H. guttulatus showed a great ability to exploit available resources in the best possible manner among different habitats, acting as a specialist predator. With an aim to understand the use of food resources that are available in the environment, the results of this study could help to propose initiatives directed to the seahorse conservation. Since prey availability does not seem to be a limiting factor in the understanding of variability and consistency of H. guttulatus populations, further studies on other environmental and biological aspects could be useful in the assessment of the conservation status of long-snouted seahorses
Alien and native species in Italian marine and transitional waters
No full textBiological invasions are one of the major threats to the ecosystem structure and functioning. After the initial introduction, frequently mediated by human activities, alien species can overcome different biogeographical and ecological barriers and determine severe impacts on native biodiversity and socio-economic activities. The Italian peninsula is located at the intersection of large trade routes within the Mediterranean Sea. Such position, along with the intense commercial activity and the high population density of the Italian coast, are considered important drivers of alien species in Italian marine and transitional ecosystems. The Italian peninsula, however, is also one of the regions with the highest native species richness within the Mediterranean Sea and, therefore, it is crucial to account for both alien and native species diversity when estimating the impact of biological invasion. Yet, such comprehensive information is frequently scattered across several biodiversity information systems and databases.Here, two datasets with alien and native species records in Italian marine and transitional waters are described. These datasets, created for the LifeWatch Italy case study on alien species, are the result of a large-scale collaboration involving experts working across the whole range of taxonomic diversity. The marine dataset includes a total of 12,219 records belonging to 3,772 species gathered from 91 investigated sites and seven EUNIS habitats. The dataset on transitional waters biodiversity includes 3,838 records belonging to 2,019 species found in 23 locations and four EUNIS habitats. Alien species were recorded in both marine and transitional waters, accounting respectively for 140 and 171 biological records belonging to 59 and 97 species. These occurrence data can be used for further research studies or management purposes, including the evaluation of the invasion risk and the formulation of alien species control and management plans. Furthermore, these compiled datasets can be used as input data for the Biotope vulnerability case study of LifeWatch ERIC, which offers a number of ICT services for the calculation of the incidence and of the impact of alien species on European biotopes
Analysis of the Sabellaria spinulosa Bioconstruction Growth in a Laboratory
Full text linkSabellaria spinulosa (Leukhart, 1849) is a suspension feeding polychaeta that lives in tubes consisting of terrigenous particles captured by the worm itself. They form impressive reefs containing millions of worm tubes. In temperate marine areas, under optimal environmental conditions, these structures can become natural breakwaters and can play an active role in sandy beaches’ defense. In this work, we report procedures aimed to analyze the growth of S. spinulosa bioconstructions in laboratory. By collecting biological replicas from a wild reef, this study aimed to identify sedimentological characteristics of sands that induce faster tube growth. During the tank experiments, the grain size and mineralogy of the sand were modified. By employing thin sections and X-ray microtomography analyses, the structures observed and measured during and after the tests were analogous to those naturally formed. The fastest growth was recorded in the presence of bioclastic sands with a grain size between 125 and 350 μm. Defining the physical conditions that induce faster growth is fundamental for the defense of these vulnerable habitats but also the surrounding marine environment. This study also lays the foundations for coastal protection interventions in which bioconstructions grown in the tank could be directly implanted on submerged natural and artificial substrates that are already present in situ
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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