Lesser-spotted Dogfish Scyliorhinus Canicula Research Articles

Localization and Characterization of Major Neurogenic Niches in the Brain of the Lesser-Spotted Dogfish Scyliorhinus canicula.

Adult neurogenesis is defined as the ability of specialized cells in the postnatal brain to produce new functional neurons and to integrate them into the already-established neuronal network. This phenomenon is common in all vertebrates and has been found to be extremely relevant for numerous processes, such as long-term memory, learning, and anxiety responses, and it has been also found to be involved in neurodegenerative and psychiatric disorders. Adult neurogenesis has been studied extensively in many vertebrate models, from fish to human, and observed also in the more basal cartilaginous fish, such as the lesser-spotted dogfish, Scyliorhinus canicula, but a detailed description of neurogenic niches in this animal is, to date, limited to the telencephalic areas. With this article, we aim to extend the characterization of the neurogenic niches of S. canicula in other main areas of the brain: we analyzed via double immunofluorescence sections of telencephalon, optic tectum, and cerebellum with markers of proliferation (PCNA) and mitosis (pH3) in conjunction with glial cell (S100β) and stem cell (Msi1) markers, to identify the actively proliferating cells inside the neurogenic niches. We also labeled adult postmitotic neurons (NeuN) to exclude double labeling with actively proliferating cells (PCNA). Lastly, we observed the presence of the autofluorescent aging marker, lipofuscin, contained inside lysosomes in neurogenic areas.

Parasitic Load, Hematological Parameters, and Trace Elements Accumulation in the Lesser Spotted Dogfish Scyliorhinus canicula from the Central Tyrrhenian Sea.

Simple SummaryThe elasmobranchs, being at the apex of the marine food chain, act as final receptors of polluting elements that are regularly discharged into the sea and, therefore, usually are considered good bioindicators of environmental pollution. The main goal of this study was to describe helminthic communities, hematological parameters, and the concentrations of trace elements in vertebrae, skin, and liver for a population of lesser spotted dogfish from the Tyrrhenian Sea. Findings suggest that there is sometimes a correlation among these parameters and between them as well as environmental pollution.Parasitological, hematological, and ecotoxicological analyses were carried out on a population of lesser spotted dogfish Scyliorhinus canicula from the central Mediterranean Sea. Parasitological analyses highlighted a poor helminthic community, highly dominated by a single taxon represented by the cestode Nybelinia sp. No differences in the parasitic load between females and males were observed. Hematological analyses showed that the number of leukocytes was significantly lower in the sharks that resulted in parasitism, and this could be due to the ability of some trace elements, such as arsenic, weakening the immune system and exposing animals to a higher risk of parasite infection, although further hematological and parasitological analyses are required on a larger number of samples. Trace elements analyses in the vertebrae, skin, and liver highlighted that the most abundant and potentially toxic elements were lead (Pb), arsenic (As), and cadmium (Cd). Other trace elements were also abundant, such as manganese (Mn), zinc (Zn), nickel (Ni), copper (Cu), and iron (Fe). Pb, As, and Mn showed the highest concentrations in vertebrae, while Cd, Cu, and Zn were the highest in the liver, probably due to their concentration in the prey items of the sharks; Fe and Ni showed the highest concentrations in the skin, due to their presence in the water column, especially along the coast where animals were collected. The concentration of some trace elements analyzed in the vertebrae decreased with the growth of the sharks. These results confirm that elasmobranchs, being predators at the apex of the marine food chain, act as final receptors for a series of polluting elements regularly discharged into the sea.

Quali-quantitative analysis of plastics and synthetic microfibers found in demersal species from Southern Tyrrhenian Sea (Central Mediterranean).

This study highlights plastics occurrence in five demersal fish species from the Southern Tyrrhenian Sea: the Red mullet Mullus barbatus barbatus, the Piper gurnard Trigla lyra, the Blackmouth catshark Galeus melastomus, the Lesser spotted dogfish Scyliorhinus canicula and the Brown ray Raja miraletus. Overall, 125 fish were examined: 21 Red mullets, 16 Piper gurnards, 75 Blackmouth catsharks, 72 Dogfish and 1 Brown ray. The percentage of fish with ingested plastics was 14.4% with 0.24 items per specimen. The majority of the debris were fibers and the application of infrared and Raman spectroscopy allowed the identification and discrimination of plastic and non-plastic fibers. The plastic debris isolated were mainly microplastics (94.1%), while macroplastics occurrence was very low (5.9%). The plastics were identified as polypropylene, Teflon, nylon, kraton G (triblock copolymer) and polyethylene. Also cellulose was detected. S. canicula was the species with the highest number of plastic pollutants.

Bycatch and discarding patterns of dogfish and sharks taken in English and Welsh commercial fisheries.

At-sea observer programmes can provide spatio-temporal data on the sizes and quantities of fish being either discarded or retained, including for species and size categories that may not be sampled effectively during scientific surveys. Such data were analysed for English and Welsh fisheries operating on the continental shelf of the North Sea ecoregion (ICES Divisions 4a-c and 7d) and Celtic Seas ecoregion (ICES Divisions 6a, 7a-c, e-k) for the period (2002-2016). These data were collated for four main gear types: beamtrawl, nephrops and otter trawls, and nets (including gillnets, tangle nets and trammel nets). Beamtrawlers caught proportionally more smaller individuals than otter trawlers, whilst nets were the most size-selective gear for larger sharks. Size-related discarding was observed, with smaller spurdog Squalus acanthias and starry smooth-hound Mustelus asterias (< 60 cm total length, LT ) usually being discarded. Such size-based selection was not evident for lesser-spotted dogfish Scyliorhinus canicula, which was generally landed as bait. Temporal changes in the discard-retention patterns were evident for S. acanthias and porbeagle Lamna nasus, with increased regulatory discarding as management measures became restrictive. A corresponding increase in the proportion of the non-quota M. asterias retained was also observed over the study period. Knowledge of the size-based discard-retention patterns by métier can also help inform on where future studies on discard survival could usefully be undertaken.

Histochemistry on vibratome sections of fish tissue: a comparison of fixation and embedding methods

Despite improvements in imaging techniques during recent years, for many non- model systems the fixation of tissues followed by embedding and sectioning for histochemical or immunohistochemical staining remains an important technique in vertebrate histology. The pres- ent study sets out to explore the preservation of histological sections of fish tissues using different preparation techniques. The quality of transverse vibratome sections from trunk segments of the lesser-spotted dogfish Scyliorhinus canicula, Atlantic sturgeon Acipenser oxyrinchus and zebrafish Danio rerio were compared using different fixatives (formaldehyde, paraformaldehyde and zinc-formaldehyde) and embedding methods (gelatine, agarose and low-temperature melting agarose). Our data show that the quality of the vibratome sections for histochemical staining is strongly dependent upon fixation and embedding media. Although paraformaldehyde fixation results in a more pronounced shrinkage of the trunk segment than the other fixatives used , the quality of the sections and the histochemical staining was best with this fixative in zebrafish and dogfish. Additionally, the embedding methods have a strong influence on the quality of the sec- tions. In the dogfish and sturgeon samples, the preferred embedding media were agarose and low-temperature melting agarose, since gelatine often caused shrinkage of the tissues. In conclu- sion, for histochemical examinations, the processing protocols for vibratome sectioning need to be adapted individually to each study organism.

Calretinin-immunoreactive systems in the cerebellum and cerebellum-related lateral-line medullary nuclei of an elasmobranch, Scyliorhinus canicula

Calretinin immunohistochemistry was used to study the organization of some cerebellar structures and lateral line medullary nuclei of an elasmobranch, the lesser-spotted dogfish Scyliorhinus canicula. In the cerebellar molecular layer, stellate cells are strongly calretinin-immunoreactive (CR-ir). Perikarya and dendrites of Purkinje cells are contacted by numerous stellate cell small CR-ir boutons. Some Purkinje cell perikarya are contacted by CR-ir climbing fibers forming complex axo-somatic contacts. In the granular layer, numerous CR-ir mossy fibers exhibited large swellings. Notable differences in density and diameter of mossy fibers are observed between the auricles and cerebellar body. Thin beaded CR-ir fibers are also present in the granular layer of the body. The lateral line nuclei of the octavolateralis region are comprised of a molecular-like cerebellar crest that covers the dorsal (electroreceptive) and the medial octavolateralis nuclei (mechanoreceptive). The cerebellar crest exhibited numerous CR-ir stellate cells. In the dorsal octavolateralis nucleus, the presence of conspicuous CR-ir cells and neuropil closely associated to the region of primary fiber terminals distinguishes it clearly from the medial nucleus, revealing major differences between the electroreceptive and mechanoreceptive primary nuclei of elasmobranchs. Moreover, CR distribution in the dogfish cerebellum showed interesting differences with those reported in cerebella of other vertebrates, indicating a high variability of cerebellar CR expression in phylogeny.

Feeding ecology of five commercial shark species of the Celtic Sea through stable isotope and trace metal analysis

In order to trace their feeding habits, stable carbon and nitrogen isotope ratios (delta15N and delta13C), as well as trace metal concentrations (Zn, Cd, Fe, Cu, Se and Hg) were analysed in the tissues of five commercial shark species from the Celtic Sea: the tope shark Galeorhinus galeus, the black-mouthed catshark Galeus melastomus, the starry smooth hound Mustelus asterias, the spiny dogfish Squalus acanthias and the lesser-spotted dogfish Scyliorhinus canicula. Our results were compared to previously described stomach contents and isotopic composition of potential preys. Isotopic ratio delta15N suggested that tope sharks fed at a higher trophic level (16.7 per thousand in the muscle) than the other species, reflecting its piscivorous diet. The lower values of spiny dogfish (11.6 per thousand in the muscle) might be explained, amongst other things, by either its migratory behaviour or its preference for preys from lower trophic levels. Cd and Hg were correlated with isotopic ratios delta13C and delta15N, and were shown to be diet-related whereas Zn, Fe and Cu seemed much more linked to species-specific metabolism. Although this multidisciplinary approach is revealed as a useful tool for the study of shark ecology, the lack of known trophic fractionation suggests that isotopic data be compared to traditional diet analyses.

Temporal and spatial organization of tyrosine hydroxylase-immunoreactive cell groups in the embryonic brain of an elasmobranch, the lesser-spotted dogfish Scyliorhinus canicula

We have studied the development of catecholaminergic (CA) neuronal groups in the brain of the dogfish Scyliorhinus canicula using immunohistochemistry to tyrosine hydroxylase (TH). The earliest TH-immunoreactive (THir) cells were detected in the primordia of the posterior tubercle and suprachiasmatic nuclei (PTN and SCN, respectively) of stage 26 embryos. At stage 28, THir cells were also seen extending between the SCN and the PTN at ventral thalamic levels. At stage 30, some THir cerebrospinal fluid-contacting neurons and migrated THir cells were found in the walls of the posterior recess, and a few weakly THir cells also appeared at the isthmus level (locus coeruleus) and in the caudal rhombencephalic tegmentum. At stage 31, further THir cell groups appeared in the synencephalon and midbrain (ventral tegmental area/substantia nigra, VTA/SN), and the rhombencephalon (viscerosensory and visceromotor columns). At stage 32, the first THir cells appeared in the pallium, the olfactory bulb and the preoptic area. THir cells are seen in the retina from stage 33. The developmental sequence of THir cell groups in dogfish appears to be rather similar to that described for teleosts, apart from the appearance of the VTA/SN and pallial cells, which lack in teleosts.

Scaling of rectal gland mass in the European lesser-spotted dogfish

In the European lesser-spotted dogfish Scyliorhinus canicula, rectal gland mass in mg (M-Rg) followed the allometric relationship: M-Rg = 1.15 M-0.68, where M is body mass (g). The concept of allometric scaling is an important consideration in studies investigating the function Of osmoregulatory organs. (C) 2003 the Fisheries Society of the British Isles.

Development of an in situ perfused kidney preparation for elasmobranch fish: action of arginine vasotocin

Acclimation of the European lesser-spotted dogfish Scyliorhinus canicula to reduced environmental salinity [85-70% seawater (SW)] induced a significant diuresis in addition to a significant decrease in plasma osmolality in vivo. The threshold for this diuresis was determined to be 85% SW. Therefore, S. canicula acclimated to 85% SW was selected for further study as a diuretic model in the development of an in situ perfused kidney preparation. The renal role of arginine vasotocin (AVT) in the in situ perfused trunk preparation was investigated. In SW, perfusion of 10(-9) and 10(-10) M AVT resulted in a glomerular antidiuresis and decreases in tubular transport maxima for glucose and perfusate flow. In 85% SW, 10(-10) M AVT had no significant effect on these renal parameters with the exception of transport maxima for glucose and perfusate flow. Tubular parameters remained unchanged by either 10(-9) or 10(-10) M AVT. The results demonstrate that the perfused kidney preparation was a viable tool for the investigation of renal parameters in elasmobranch fish and that AVT induced a glomerular antidiuresis.

Changes in chloride secretion rate and vascular perfusion in the rectal gland of the European lesser-spotted dogfish in response to environmental and hormonal stimuli

Chloride secretion rates of rectal glands taken from the European lesser-spotted dogfish Scyliorhinus canicula adapting to 70% and 120% sea water (SW) were significantly greater and less than, respectively, those in the control 100% SW group. C-type natriuretic peptide (CNP) significantly increased chloride secretion rates above basal values in 100% SW although angiotenisn II (ANG II) had no effect. Perfusion of the secretory epithelia in rectal glands from 70% SW lesser-spotted dogfish was significantly higher than in rectal glands from 100% and 120% SW lesser-spotted dogfish. Perfusion of rectal glands with ANG II had no effect on perfusion of the secretory epithelia, although CNP perfusion induced significantly greater perfusion of the secretory epithelia than all other treatments. It remains to be determined if a reduction in environmental salinity induces an increase in plasma concentration of CNP and hence an increase in rectal gland activity.

Metazoan parasites of the lesser-spotted dogfish Scyliorhinus canicula and their potential as stock discrimination tools

The metazoan parasites of 101 lesser-spotted dogfish Scyliorhinus canicula from locations off the coast of England (Plymouth and the eastern Solent) and Wales (Cardigan Bay) were surveyed and assessed for their potential as stock discrimination tools. A total of ten parasite species was found using a relatively rapid host examination technique suitable for non-parasitologists. On the basis of established criteria, larval anisakid nematodes and the copepod Lernaeopoda galei were selected as being potentially useful as stock discrimination tools. The monogeneans Leptocotyle minor and Hexabothrium appendiculatum may be suitable as markers following further investigation of their response to handling stress.

Fish scavenging behaviour in recently trawled areas

The diets of gurnards Aspitrigla cuculus and Eutrigla gurnardus, lesser-spotted dogfish Scyliorhinus canicula and whiting Merlangius merlangus were examined to determine whether they migrated into recently trawled areas to feed on animals that may be damaged or dislodged by the action of a 4 m beam trawl. Gurnards and whiting increased their intake of prey after an area had been fished. In particular, they increased the proportion of the amphipod Ampelisca spinipes in their diets. Beam trawling damaged the purple burrowing heart urchin Spatanguspurpureus, scallop Aequipecten operculans, Ensisspp. and Laevocardium sp., exposing internal tissues which were then eaten by whit- ing. Some mobile invertebrate scavengers, such as Pandalusspp., only occurred in diets after the area had been fished, suggesting that these animals were also scavenging over the trawl tracks. Observa- tions of the seabed using a side-scan sonar revealed a greater concentration of fish marks around the trawl tracks than in adjacent unfished areas. Our results indicate that fish rapidly migrate into beam trawled areas to feed on benthic animals whlch have been either damaged or disturbed by fishing or on scavenging invertebrates. In areas where certain benthic communities occur, beam trawling inten- sity may be such that it creates a significant food resource for opportunistic fish species. This is a possi- ble mechanism whereby long-term community structure could be altered by fishing activity.