Amongst other factors, topographic features can influence the genetic variability among populations of marine organisms. This applies to host species but also to their parasites, which are poorly ...studied regarding this aspect, as well as with regard to their use as bioindicators. In the present work, the ribosomal DNA (28S rDNA) was used to assess genetic diversity of Grillotia (Cestoda, Trypanorhyncha) larvae in one of its paratenic hosts, namely Etmopterus spinax, across five different regions (off Scotland, Celtic, Alboran and Balearic Seas and off Cyprus) belonging to three major geographic areas (Northeast Atlantic, western and eastern Mediterranean). The obtained sequences revealed a total of 18 polymorphic sites and 17 haplotypes, as well as significant values of variance throughout the five different regions. Reconstructed phylogenetic trees highlighted that all Grillotia sp. sequences formed a monophyletic group, but divergent lineages split into different main clades which were in relation to the area of origin, with a consistent cluster of sequences from the Atlantic Ocean, as well as another from the Eastern Mediterranean. In contrast, low genetic differentiation was observed between samples from Balearic and Alboran Seas, and with respect to Grillotia sp. larvae from the Gulf of Naples analysed in a previous study. Geographical differences in parasite infection descriptors (prevalence, abundance, and intensity) were assessed, revealing significant differences among the sampled regions.
The present study indicates that geographical distance and submarine barriers affect not only the connectivity of hosts but also their parasite infrapopulations by limiting interpopulation dispersal. It underlines the usefulness of parasites as biological tags for the study of susceptible and data-poor host species such as deep-water sharks and its potential implications for host population management and protection measures.
Display omitted
•Cestode larvae of Grillotia adenoplusia ex its paratenic host Etmopterus spinax.•RDNA (28S) revealed genetic diversity between NE Atlantic and Mediterranean regions.•Consistent sequence cluster for the NE Atlantic and Eastern Mediterranean.•Low genetic differentiation within Western Mediterranean.•Limited interpopulation dispersal apply not only to hosts, but also to parasites.
The parasite communities of sharks have been largely neglected despite the ecological importance and vulnerability of this group of fishes. The main goal of the present study is to describe the ...parasite communities of three deep-dwelling shark species in the NW Mediterranean. A total of 120 specimens of Galeus melastomus, 11 Etmopterus spinax and 10 Centroscymnus coelolepis were captured at 400–2200m depth at two seasons and three localities off the mainland and insular slopes of the Balearic Sea. Environmental and fish biological, parasitological, dietary, enzymatic and histological data were obtained for each specimen, and the relationships among them tested. For G. melastomus, E. spinax and C. coelolepis a total of 15, two and eight parasite species were respectively recovered. The parasite community of G. melastomus is characterized by high abundance, richness and diversity, and the cestodes Ditrachybothridium macrocephalum and Grillotia adenoplusia dominate the infracommunities of juvenile and adult specimens, respectively. A differentiation of parasite communities, linked to a diet shift, has been observed between ontogenic stages of this species. E. spinax displays a depauperate parasite community, and that of C. coelolepis, described for the first time, shows moderate richness and diversity. Detailed parasite-prey relationships have been discussed and possible transmission pathways suggested for the three hosts. Parasites were mostly related to high water turbidity and O2 levels, which enhance zooplankton proliferation and could thus enhance parasite transmission. The nematodes Hysterothylacium aduncum and Proleptus obtusus were linked to high salinity levels, as already reported by previous studies, which are associated to high biomass and diversity of benthic and benthopelagic crustaceans. A decrease of acetylcholinesterase activity and lower hepatosomatic index, possibly linked to infection-related stress, have been observed. Lesions associated to encapsulated larvae of G. adenoplusia have been observed in the muscle of G. melastomus, especially in the tail region, which can be indicative of the hunting strategy of its final host and may compromise the escape response of G. melatomus thus facilitating parasite transmission.
•Parasite community of three deep-sea shark described in the Mediterranean.•Detailed parasite-prey relationships have been discussed.•Possible transmission pathways have been suggested for the parasites recovered.•Relationships between parasites and environmental variables assessed.•Effects of parasites on host health has been evaluated.
Concern about microplastic pollution little is known about levels in deep-sea species; to fill this knowledge gap, levels of microplastics in the gastrointestinal (GI) tracts of 34 fish from eight ...different deep–sea by–catches: blackmouth catshark, lesser spotted dogfish, and velvet belly, armless snake eel, hollowsnout grenadier, phaeton dragonet, royal flagfin, and slender snipe eel were measured. All were collected at the same site (east Sardinia, Mediterranean Sea; 40°10′12.49″N, 9°44′12.31″E) using a bottom gillnet at depths between −820/250 and −1148 ft./350 m. Microplastics (MPs) were retrieved in 16 out of 34 fish. At least one microplastic item was found in 48% (33%, E. spinax - 75%, G. melastomus) of the samples. The most frequent was polyethylene (PE), with nine items (filaments, films, fragments) found in five specimens. This preliminary study of by–catches adds new data on MPs ingestion by species inhabiting a deep–sea environment of the Mediterranean.
Display omitted
•Microplastics (MPs) in the deep–sea environments: submarine canyons.•Eight deep–sea species were collected from the Gulf of Orosei (east Sardinia, Italy)•The study measured MPs levels and characteristics in deep–sea by–catches.•MPs varied in shape and colors across species.
Lantern sharks are small shark species that can be seen at depths between 70 and 2000 meters. Due to their luminescent characteristics, they have been called “Lantern shark”. In total eleven ...specimens of the velvet belly lantern shark, Etmopterus spinax (Linnaeus, 1758), were caught in the deep seas of Northern Cyprus by using a bottom trawl. Sampling was carried out using 13 trawling operations. The collected samples were placed in 4% formalin and stored at the Museum of the Systematic, Faculty of Fisheries, Mersin University, (catalogue number: MEUFC-18-11-082). As a sampling area, the depths between 274 and 641 m were selected. Other cartilaginous fish caught during sampling except E. spinax were Galeus melastomus (1 individual), Squalus acanthias (4 individuals), Scyliorhinus canicula (85 individuals). E. spinax made up 10.89% of all cartilaginous fishes which were caught. Species identification for all fishes caught is made with the help of morphological features.
Fener köpekbalıkları 70 - 2000 m arasındaki derinliklerde görülebilen küçük köpekbalığı türleridir. Lüminesan özellikleri nedeniyle “Fener köpekbalığı” olarak anılmaktadırlar. Kuzey Kıbrıs derin denizlerinde 13 adet trol operasyonu yapılarak, dip trolü yöntemi ile toplam 11 adet kadife fener köpekbalığı, Etmopterus spinax (Linnaeus, 1758) yakalanmıştır. Yakalanan örnekler %4’lük formalin içerisine konularak; Mersin Üniversitesi, Su Ürünleri Fakültesi, Sistematik Müzesine (Katalog numarası: MEUFC-18-11-082) yerleştirilmiştir. Örnekleme alanı olarak 274 ve 641 m arasındaki derinlikler seçilmiştir. Örneklemeler sırasında E. spinax haricinde yakalanan diğer kıkırdaklı balıklar Galeus melastomus (1 birey), Squalus acanthias (4 birey), Scyliorhinus canicula (85 birey) şeklindedir. E. spinax yakalanmış olan tüm kıkırdaklı balıkların %10.89’luk bir bölümünü oluşturmaktadır. Yakalanan tüm balıklar için tür teşhisi morfolojik özellikler yardımı ile yapılmıştır.
Debris has been recognized as a global environmental problem including within deep habitats. From 26 fish species (1504 specimens) caught in the Eastern Ionian Sea during deep-water long-line ...surveys, plastic debris was found in 24 individuals of Galeus melastomus (3.2%) and single individuals of Pteroplatytrygon violacea, Squalus blainville, Etmopterus spinax, and Pagellus bogaraveo. The occurrence of debris among their food was infrequent. Ingested debris included primarily plastics (86.5%) and to a lesser extent pieces of metal and wood. Among ingested plastics, fragments of hard plastic material constituted the highest proportion (56.0%), followed by plastic bag fragments (22.0%), fragments of fishing gears (19.0%) and textile fibers (3.0%). Among the species with ingested debris, G. melastomus swallowed all debris categories; P. violacea and S. blainville ingested plastic bag fragments, whereas pieces of hard plastics were found in E. spinax and P. bogaraveo.
► We studied debris ingestion in fish of the Eastern Mediterranean deep-waters. ► Debris occurrence was not common in fish guts. ► Elasmobranchs ingested debris more frequently than teleosts. ► P. violacea, G. melastomus, S. blainville, E. spinax and P. bogaraveo ingested debris. ► Plastics were the most frequent debris category ingested.
The capture of a female specimen of the velvet belly lantern shark Etmopterus spinax with abnormal skin coloration is reported. The specimen was captured off northern Spain (Bay of Biscay, ...North‐eastern Atlantic) in 2021 by bottom trawling. The lack of dermal melanophores combined with a normal retinal pigmentation, lead us to considerate the specimen as leucistic. This is the first case of leucism in E. spinax and the second record of colour aberration in the family Etmopteridae. A comprehensive updated review of published literature on albinism and leucism in chondrichthyans is also provided.
Understanding how marine predators interact is a scientific challenge. In marine ecosystems, segregation in feeding habits has been largely described as a common mechanism to allow the coexistence of ...several competing marine predators. However, little is known about the feeding ecology of most species of chondrichthyans, which play a pivotal role in the structure of marine food webs worldwide. In this study, we examined the trophic ecology of 3 relatively abundant chondrichthyans coexisting in the Mediterranean Sea: the blackmouth catshark Galeus melastomus, the velvet belly lanternshark Etmopterus spinax and the rabbit fish Chimaera monstrosa. To examine their trophic ecology and interspecific differences in food habits, we combined the analysis of stomach content and stable isotopes. Our results highlighted a trophic segregation between C. monstrosa and the other 2 species. G. melastomus showed a diet composed mainly of cephalopods, while E. spinax preyed mainly on shrimps and C. monstrosa on crabs. Interspecific differences in the trophic niche were likely due to different feeding capabil ities and body size. Each species showed different isotopic niche space and trophic level. Specifically, C. monstrosa showed a higher trophic level than E. spinax and G. melastomus. The high trophic levels of the 3 species highlighted their important role as predators in the marine food web. Our results illustrate the utility of using complementary approaches that provide information about the feeding behaviour at short (stomach content) and long-term scales (stable isotopes), which could allow more efficient monitoring of marine food-web changes in the study area.
Anelasma squalicola Darwin 1852, is a barnacle that occurs on elasmobranchs from the Atlantic, Pacific, Arctic and Indian Ocean. It infects sharks of the families Etmopteridae and Pentanchidae. The ...barnacle attaches sub-dermally to its hosts, relying on its interstitial fluid for its nourishment. Herein we present the first record of this species in the Mediterranean Sea, from Etmopterus spinax (Linnaeus, 1758) caught during a bottom-trawl survey in the Alboran Sea (western Mediterranean) in 2017. The overall prevalence of infection was very low (0.22%). The calculated HSI index for the parasitized individual was lower compared to overall means of other individuals and could indicate a potential physiological alteration in the host.
Abstract
The velvet belly lanternshark,
Etmopterus spinax
, uses counterillumination to disappear in the surrounding blue light of its marine environment. This shark displays hormonally controlled ...bioluminescence in which melatonin (MT) and prolactin (PRL) trigger light emission, while α-melanocyte-stimulating hormone (α-MSH) and adrenocorticotropic hormone (ACTH) play an inhibitory role. The extraocular encephalopsin (Es-Opn3) was also hypothesized to act as a luminescence regulator. The majority of these compounds (MT, α-MSH, ACTH, opsin) are members of the rapid physiological colour change that regulates the pigment motion within chromatophores in metazoans. Interestingly, the lanternshark photophore comprises a specific iris-like structure (ILS), partially composed of melanophore-like cells, serving as a photophore shutter. Here, we investigated the role of (
i
) Es-Opn3 and (
ii
) actors involved in both MT and α-MSH/ACTH pathways on the shark bioluminescence and ILS cell pigment motions. Our results reveal the implication of Es-Opn3, MT, inositol triphosphate (IP
3
), intracellular calcium, calcium-dependent calmodulin and dynein in the ILS cell pigment aggregation. Conversely, our results highlighted the implication of the α-MSH/ACTH pathway, involving kinesin, in the dispersion of the ILS cell pigment. The lanternshark luminescence then appears to be controlled by the balanced bidirectional motion of ILS cell pigments within the photophore. This suggests a functional link between photoreception and photoemission in the photogenic tissue of lanternsharks and gives precious insights into the bioluminescence control of these organisms.
The velvet belly lanternshark (Etmopterus spinax) is a small deep-sea shark commonly found in the Eastern Atlantic and the Mediterranean Sea. This bioluminescent species is able to emit a blue-green ...ventral glow used in counter-illumination camouflage, mainly. In this study, paired-end Illumina HiSeqTM technology has been employed to generate transcriptome data from eye and ventral skin tissues of the lanternshark. About 64 and 49 million Illumina reads were generated from skin and eye tissues respectively. The assembly allowed us to predict 119,749 total unigenes including 94,569 for the skin transcriptome and 94,365 for the eye transcriptome while 74,753 were commonly found in both transcriptomes. A taxonomy filtering was applied to extract a reference transcriptome containing 104,390 unigenes among which 38,836 showed significant similarities to known sequences in NCBI non-redundant protein sequences database. Around 58% of the annotated unigenes match with predicted genes from the Elephant shark (Callorhinchus milii) genome. The transcriptome completeness has been evaluated by successfully capturing around 98% of orthologous genes of the « Core eukaryotic gene dataset » within the E. spinax reference transcriptome. We identified potential "light-interacting toolkit" genes including multiple genes related to ocular and extraocular light perception processes such as opsins, phototransduction actors or crystallins. Comparative gene expression analysis reveals eye-specific expression of opsins, ciliary phototransduction actors, crystallins and vertebrate retinoid pathway actors. In particular, mRNAs from a single rhodopsin gene and its potentially associated peropsin were detected in the eye transcriptome, only, confirming a monochromatic vision of the lanternshark. Encephalopsin mRNAs were mainly detected in the ventral skin transcriptome. In parallel, immunolocalization of the encephalopsin within the ventral skin of the shark suggests a functional relation with the photophores, i.e. epidermal light-producing organs. We hypothesize that extraocular photoreception might be involved in the bioluminescence control possibly acting on the shutter opening and/or the photocyte activity itself. The newly generated reference transcriptome provides a valuable resource for further understanding of the shark biology.
PDF
