Siganus Research Articles

Improved Design Fixed Stake Trap With PVC Poles and Suitable Mesh Size Net Enables Sustainable White-Spotted Spinefoot, Siganus canaliculatus (Park, 1797) Fisheries in Luwu District, South Sulawesi

The traditional fixed stake trap made typically of wooden poles and thinly interwoven bamboos walls have been used for generations as fishing gear in coastal regions of South Sulawesi Province, Indonesia. In the 1980s, bamboo slats were replaced with nets of various mesh sizes as they became readily available, and currently, in the research area, no bamboo is used. Each unit of the wooden structure is made of around 300 poles that must be replaced three to four times annually and is becoming difficult due to the scarcity of wood and the high cost. Thus, this research aims to provide a feasible solution using PVC pipes and a suitable size mesh net for sustainable fisheries management of white-spotted spinefoot, Siganus canaliculatus (Park, 1797). The study was done in Karang-karangan village located on the coast of Luwu Regency where white-spotted spinefoot is the main fishing livelihood activity of fishers. The mesh size of the net used was 2.60 cm, and the results showed that the newly designed fixed stake trap unit made of PVC has been durable for the last 2.2 years and is expected to last at least 5 years. Compared to the traditional wood structure, there are no barnacles attached to the PVC pipes. The net size used allows smaller fish below 8.6 cm in length to escape, thus making white-spotted spinefoot fisheries sustainable. The estimated cost of using wood for 5 years is IDR60 million (USD4200), while PVC only requires around IDR15 million (USD1050).

Genetic divergence and phylogenetic relationship of the rabbitfish Siganus rivulatus inferred from microsatellite and mitochondrial markers

The rabbit fish, Siganus rivulatus, is a Mediterranean non-endogenous species, that has succeeded in migrating to the different coasts of the Mediterranean Sea. The success of this species in the new environment, with different trophic, biotic, and physical conditions, inspired the study of genetic variation between the Rea Sea and Mediterranean Sea populations. The current study aims to use microsatellite (SSR) and mitochondrial DNA sequence (mtDNA) markers to determine the genetic divergence and phylogenetic relationship of S. rivulatus from the Red Sea and the Mediterranean Sea. A total of 200 S. rivulatus samples (42.50 ± 3.89 gm) were collected from the Red Sea and the Mediterranean Sea. Twelve SSR loci were screened to detect genetic differentiation, in addition to those in mtDNA. The results for the SSR markers showed seventy polymorphic alleles, with an average of 5.83 alleles per locus. Additionally, the inter-population genetic diversity was 0.063. The nucleotide composition of the MT-CO1 sequences revealed clear variations between the two studied populations. Phylogenetic analyses indicated that the Red Sea samples were more versatile than the Mediterranean Sea samples. The results indicated that the mtDNA of S. rivulatus is very variable and a species-sensitive marker to detect possible genetic variations, which could be part of the eco-physiological adaptation and key to the success of the migrant S. rivulatus in the Mediterranean Sea.

Identifying volatile compounds in rabbit fish (Siganus fuscescens) tissues and their enzymatic generation

Identifying volatile compounds in rabbit fish (Siganus fuscescens) tissues and their enzymatic generation

1368. Species Diversity and Co-Occurrence Patterning in Bone and Soft Tissue Infections

Abstract Background Polymicrobial results from conventional cultures in bone and soft tissue infections have generally been reported as independent co-occurrences (i.e. assuming no relationship or interaction between species). The objective of this study was to identify non-random (dependent) co-occurrence in bone and soft tissue infections. Methods We used single center Theradoc (Premiere Inc., Charlotte, NC) data on microbiology specimens collected over a decade (4/2010 to 4/2020). We included only tissue, fluid and swab specimens identified as being obtained from bone, skin, soft tissue or a wound during a patient’s first episode of infection. Blood and liver biopsy specimens were excluded. Patterning involving >2 organisms was examined with factor analysis. Analyses were done with R version 3.6.1. Threshold p-values were adjusted for multiple comparisons, often to p< 0.001. Results Polymicrobial culture results were seen much more frequently in the foot (76%) and sacrum (78%) than specimens from other locations (43%). The highest Shannon diversity index was seen in sacral specimens, followed by foot and leg specimens. Pseudomonas aeruginosa and E. coli was found more frequently in sacral bone and soft tissue specimens, while S. aureus was found most often in the spine bone and foot bone and soft tissue. Corynebacterium was found more frequently in foot bone (23%) and foot soft tissue (18%) than in non-foot soft tissue specimens (11%). Analysis of pairwise species co-occurrences in foot specimens (n=765) demonstrated that S. aureus made significantly less frequent the presence of Bacteroides, Enterobacter, and other staphylococcal species (Table 1). Analysis of non-foot soft tissue specimens (n=2,647) confirmed this pairwise associations and suggested three patterns (Table 2): A, polymicrobial without S. aureus; B, Enterococcus + gram negatives; and C, streptococcal. Table 1. Pairwise co-occurrences between species in bone and soft tissue specimens from foot infections (n=765). Factor analysis results demonstrating species associated with three polymicrobial patterns in soft tissue infection specimens. Blue denotes positive association (more often occurring as part of the pattern), red or grey denotes negative associations (less often occurring as part of the pattern). Numbers denote factor weights, a measure of the strength of the association. Conclusion Species incidence and diversity vary by location and tissue type. The many non-random occurrences found suggest complex interrelationships between microbes in soft tissue and bone infections, including organisms often classified as non-pathogens. Further study may further characterize these relationships and aid in antibiotic selection. Disclosures All Authors: No reported disclosures

Characterization of a macrophagic-like cell line derived from rabbit fish (Siganus fuscescens): An illustration of anti-inflammatory responses of the herbal extract of Scutellaria baicalensis

A new cell line was isolated and characterized from the head kidney of Siganus fuscescens (rabbit fish). The new macrophagic-like cell line was named as rabbit fish macrophage (RFM), and which could be sub-cultured for over 50 cycles since the development. RFM cell line was tested for growth in different temperatures and serum concentrations: the best growing condition was optimized at 20% serum under 28 °C. In cultured RFM cells, sequencing of 18S rRNA, as well as immunostaining of cytokeratin and CD 68, confirmed the identity as macrophagic cell of S. fuscescens. Cultured RFM cells were exposed to challenge of inflammation, as triggered by LPS, showing highly sensitive responses to inflammation, including release of nitric oxide, expression of cytokine, and activation of phagocytosis. The water extract of aerial part of Scutellaria baicalensis, named as SBA, has been shown anti-inflammatory property in S. fuscescens fish. In order to extend the application of SBA in aquaculture, the extract and its effective flavonoids, i.e. baicalin and scutellarin, were applied in LPS-treated RFM cells. Application of SBA extract, baicalin or scutellarin, inhibited the expressions of LPS-induced inflammatory cytokines, i.e. IL-1β, TNF-α, as well as the signaling of transcription factor NF-κB. The results support the established RFM cell line could be an ideal in vitro model in drug screening relating to inflammation. Additionally, the notion of SBA herbal extract in fish aquaculture is supported by its efficacy against inflammation.

Feeding containing the aerial part of Scutellaria baicalensis promotes the growth and nutritive value of rabbit fish Siganus fuscescens.

The root of Scutellaria baicalensis (Scutellaria Radix) has been used as herbal medicine for years, while its stem and leaf (aerial part) are considered as waste. The water extract from the aerial part of S. baicalensis (named as SBA) being included in the feeding of Siganus fuscescens (grey rabbit fish) has been shown to replace antibiotics in aquaculture with excellent outcome. To strengthen the usage of SBA in fish feeding, the total fish output and its nutritive value were determined here. Feeding the fishes with different doses of SBA for a month, the body length and weight were significantly increased after intake of standard feed containing 1% SBA. In parallel, the expressions of alkaline phosphatase and growth‐related factors in bone, liver, and muscle of 1% SBA‐fed fishes were markedly increased, suggesting the beneficial effects of SBA. The composition of amino acid and fatty acid in fish muscle, after intaking 1% SBA‐containing feed, was altered. In SBA‐fed fish muscle, the amounts of threonine and methionine were increased, while the amount of leucine was decreased, as compared with control group. The amounts of fatty acids, including docosahexaenoic acid, phosphatidylcholine, and phosphatidylethanolamine, were increased in the 1% SBA‐fed fish, while the amounts of triglycerides were decreased. The results indicated the growth‐promoting activity of SBA in an in vivo culture of S. fuscescens, as well as to increase the nutritive values of the muscle. Thus, the re‐cycle of waste products during the farming of S. baicalensis herb in serving as fish feeding should be encouraged.

LAJU PERTUMBUHAN DAN KELANGSUNGAN HIDUP IKAN BARONANG Siganus canalicalatus YANG DIBERI JENIS PAKAN DAN FREKUENSI YANG BERBEDA DI KERAMBA JARING APUNG

This research is about "Growth Rate and Survival Rate of Baronang Siganus canaliculatus Fish Given Different Types of Feed and Frequency in the Floating Net Cages. The research lasted as long as for 6 (six) months from May to October 2018.The design of this study used a factorial Completely Randomized Design (CRD) using 2 factors as treatment, namely: (1) 50% of the trash fish, 50% papaya leaves, and 25% trash fish & 75% papaya leaves. (2) the frequency of feeding once, the frequency of feeding 2 times and the frequency of feeding 3 times. This treatment is to see whether there is a significant difference between the treatment of growth rate and survival rate of baronang fish (Siganus canaliculatus) as the research sample. From the research data analyzed using ANOVA, it was found that the type of feed and the frequency of distribution had a significant effect on the growth rate. Based on statistics, the results of this study showed no significant effect between treatments on growth, survival and FCR. Feeding with a composition of 50% trash fish and 50% papaya leaves with a frequency of 3 times gave the highest growth rate, survival and FCR values for rabbit fish (Siganus canaliculatus) rearing for 120 days in Floating Net Cages

Oceanographic chaos and its role in larval self-recruitment and connectivity among fish populations in Micronesia

A 30-year time series of the recruitment of rabbit fish, a herbivorous coral reef fish, on the island of Guam in the tropical western Pacific, showed variability that ENSO alone does not explain. To help explain this variability, a high-resolution biophysical model that includes directional swimming reveals how mesoscale turbulence and ENSO-driven changes in the ocean circulation control the self-recruitment of rabbit fish. ENSO drives island wakes that enhance the capacity to retain locally spawned larvae, and mesoscale turbulence generates much variability and promotes seaward dispersion at time scales larger than the Pelagic Larval Duration. The same processes are predicted to occur for the self-recruitment of grouper fish, a carnivorous coral reef fish, in Palau, Micronesia. The models suggests that 99% of these fish larvae are exported seaward from Guam and Palau. Those larvae are the ones that could provide connectivity between reefs and islands in Micronesia. This connectivity for the grouper fish was predicted using an altimetry-driven advection-diffusion oceanography model for 40 mass spawning events spread over 10 years. The mesoscale turbulence, and not the mean oceanographic currents, is the dominant process controlling the connectivity, which is thus chaotic. This finding applies also in the Galapagos archipelago and the Coral Sea fringing the Great Barrier Reef.

Nutrient Flow in an Integrated Rabbit–Fish–Rice System in Rwanda

Nutrient Flow in an Integrated Rabbit–Fish–Rice System in Rwanda

Low microplastic abundance in Siganus spp. from the Tañon Strait, Central Philippines

Microplastic (MP) occurrence is a major global issue, though data on MP occurrence in the Philippines is limited and the potential effects of MPs on biota are still poorly studied. MP occurrence in fishes remains a concern, especially in economically and ecologically important species such as Siganus spp. This study determined MP occurrence in the gastrointestinal tract of wild rabbit fishes from Tañon Strait, the largest marine protected area in the Philippines. Siganus canaliculatus (n = 65), S. spinus (n = 17), S. guttatus (n = 5), S. virgatus (n = 8) and S. punctatus (n = 1) were sampled from the north and south of the strait. All MPs isolated from the gut of the rabbit fishes except for fibers were chemically analyzed by ATR-FTIR spectroscopy; an established library was used to determine the polymeric identities. Five particles were confirmed as polyester, polyamide, polyethylene or phenoxy resin MPs. The average MP abundance was 0.05 items/individual (S. virgatus > S. guttatus > S. canaliculatus > S. spinus = S. punctatus), which is comparable to studies conducted in other locations using similar methods. Fibers were counted (1556 in total), but not chemically analyzed. The low MP abundance in the samples may be attributed to the capability of rabbit fishes to discriminate food preferences. However, the risks associated with MPs should not be underestimated, especially as all parts of the fishes—including the gut—are utilized as human foods in the Philippines and many other Asian countries.

Preliminary Assessment on the Histological Changes in Juvenile Siganus guttattus (Bloch, 1787) Exposed to Plastic Debris.

Plastic debris is ubiquitous in the marine environment and many of this is polyethylene based plastic bags. Its potential effect on marine organisms is still understudied. Hence, this study determined the histological changes induced in the intestine and liver of the juvenile rabbit fish, Siganus guttatus. S. guttatus (N = 150) were sub chronically exposed to plastic bag debris suspensions (0, 0.01, 0.1, 1.0 and 10mgL-1) for 10days. In addition to histological changes, the condition factor (CF) index of the fishes were assessed. Results showed that there was no significant difference in the CF index of the fishes exposed to varying concentrations of plastic suspensions, there was however histological changes in fishes exposed to 10mgL-1. The histological changes in the intestine were hyperemia, necrosis, goblet cells hyperplasia, and shortening of the villi. Histological changes in the liver were hyperemic blood vessels and vacuolization. Fishes exposed to 10mgL-1 exhibited a higher proximal, distal, liver and total organ index as compared to those unexposed (p < 0.05).

Short term culture of wild caught juvenile rabbit fishes (Siganus javus) in open sea cages at Palk Bay

Objectives: The main objective of the study was to collect and rear the unmarketable, small sized S.javus which is mostly rejected by the traditional fisherman. During fishing activities, under sized S.javus ranging in sizes from 25 to 40 kg (&lt; 30-40 % of total catch/day) is being captured. Due to very low marketable value these small fishes (&lt;250 g) get rejected. Therefore, we utilized this as an economically viable option for utilization as seeds for rearing until they reach the necessary marketable size. Methods: Undersized juveniles (12-16 cm, 40 -55 g) were collected from nearby Olaikuda village,Rameshwaram using traditional traps made using bamboo and odai tree bark (Acacia planifrons). The collected juveniles were stocked in sea cages and fed with locally formulated plant based feed containing 28-32 % crude protein. Findings: Harvesting was successfully done after 140 days with 90 % survival. The average growth rate achieved was 2.5 g /day with FCR of 2.01. This resulted in an average harvest size of 400 g/fish from its initial stoking size of 50 g with an attracted market value of Rs. 150/kg. Novelty: Till date, no attempts were made to commercialize such harvesting techniques for the species Siganus javus in pilot scale in India (Except James, 1984). Keywords: Rabbit fish; Siganus javus; sea cage culture; rabbit fish culture; Siganidae

First record of the nematode, Huffmanela sp. infecting the broomtail wrasse (Cheilinus lunulatus) from Egypt.

A total of 385 Red Sea coral reef fish representing three species; Broom tail wrasse (Cheilinus lunulatus), Blacktip grouper (Epinephelus fasciatus) and Rabbit fish (Siganus sp.). were examined for the presence of nematode Huffmanela species. The eggs of Huffmanela species were isolated and identified only from the C. lunulatus. The total prevalence of Huffmanela sp. infestation were 69.5%. The highest prevalence was observed in winter and the lowest in spring and summer. The prevalence was increased in correlation with fish body weight. Fully developed eggs of Huffmanela species were dark brown embryonated, elongated, with slightly protruding plugs. A high density of Huffmanela sp. eggs with different developmental stages packed the epithelial layer of the gas bladder. The surrounding tissue of gas bladder was hemorrhagic and sometimes necrotic associated with chronic inflammatory cell infiltration. This is the first record of Huffmanela species infestation in Broom tail wrasse C. lunulatus, Red Sea coral reef fishes.

Fish assemblage structure response to seagrass bed degradation due to overgrazing by the green sea turtle Chelonia mydas at Iriomote Island, southern Japan

The fish assemblage structure response to rapid degradation of Enhalus acoroides seagrass beds due to overgrazing by green sea turtles (Chelonia mydas) was investigated at Iriomote Island, southern Japan, by visual censusing of fish species in several microhabitats in and around the beds (i.e., dense seagrass bed, grazed bed, their boundaries, and adjacent sandy area). Fish assemblage structure differed among the seagrass microhabitats, both species and individual numbers being higher in microhabitats with seagrass compared to overgrazed beds and unvegetated sandy areas, together with different species composition. In the dense seagrass beds and boundary areas (the border area between dense seagrass beds and grazed areas), seagrass-associated fishes such as the rabbit fish Siganus fuscescens and cardinal fish Ostorhinchus ishigakiensis were abundant and comparable with those in other seagrass beds in the area. In addition, the fish assemblages in those microhabitats varied seasonally, fish abundance being greater in summer due to higher levels of recruitment. In the grazed bed, benthic gobies, such as Ctenogobiops crocineus and Cryptocentrus caeruleomaculatus, were dominant (similarly so in unvegetated sandy areas), and seasonal variations in such assemblages were relatively low compared to those in dense seagrass microhabitats. The decrease in the abundance and diversity of seagrass-associated fish in the grazed areas could be explained partly by the shortage of vegetation (< 20 cm in leaf length) for shelter and feeding throughout the year. The results suggested that the degradation of seagrass beds due to overgrazing by green turtles has a deleterious effect on fish assemblages, and that future conservation and management strategies for seagrass beds should consider both their associated fish communities and green turtles.

Hydrolytic bacteria associated with natural helminth infection in the midgut of Red Sea marbled spinefoot rabbit fish Siganus rivulatus

Fish infected with intestinal helminths or pathogenic bacteria can pose a serious risk of foodborne disease, threatening human and animal health, and require high attention. The current study investigates the diversity and composition of the microbiota in the midgut of rabbit fish Siganus rivulatus naturally infected with helminths. Six species of helminth parasites, including the digeneans Hexangium sigani and Gyliauchen volubilis, the acanthocephalans Sclerocollum rubrimaris and Neorhadinorhynchus macrospinosus, and the nematodes Procammalanus elatensis, and Ascaridoid larvae were recorded in the fish intestine. P. elatensis had the highest prevalence, occurring in 65% of infected fish; 72.2% of infected fish had concurrent infection with two or more helminth species. The total count of aerobic bacteria ranged from 1 to 305 colony-forming units (CFU)/g midgut contents. Four hydrolytic bacteria were recovered from the infected samples: Escherichia coli (ASU 31), Bacillus cereus (ASU 36) MN955553, Bacillus thuringiensis (ASU 34) MN955550, and Novosphingobium aromaticivorans (ASU 35) MN955552, which were identified using 16S rRNA genes. Bacterial richness was significantly correlated with concurrent parasitic infection and high content of extracellular hydrolytic amylases, proteases, cellulases, and lipases. The present results showed that the composition of the microbiota was affected by natural helminth infections in Siganus rivulatus, and the significant interaction between parasitic load and intestinal pathogenic bacteria, which may be primary in fish diseases etiology.

The herbal extract deriving from aerial parts of Scutellaria baicalensis shows anti-inflammation and anti-hypoxia responses in cultured fin cells from rabbit fish

A new cell line derived from dorsal fin of rabbit fish Siganus fuscescens was developed and characterized. The cell line was isolated from the dorsal fin, named as rabbit fish fin (RFF) cell line, and which was sub-cultured for 50 cycles since the development. This cell line was tested for growth in different temperatures and serum concentrations, and the best growing condition was at 20% serum at 28 °C. In cultured RFF cells, amplification of 18S rRNA from genomic DNA and immunostaining of cellular cytokeratin confirmed the proper identity of S. fuscescens fish. After 30th passage of cultures, the cells were exposed to challenge of inflammation, triggered by LPS, and hypoxia, mimicked by CoCl2. Cultured RFF cells showed robust sensitive responses to inflammation and hypoxia in directing the expressions of cytokines and hypoxia inducible factor-1α (HIF-1α). The water extract of aerial part of Scutellaria baicalensis (SBA) has been shown in rabbit fish to prevent inflammation. Here, we extended this notion of testing the efficacy of SBA extract in the developed cultured RFF cells. Application of SBA extract inhibited the expression of LPS-induced inflammatory cytokines, i.e. IL-1β, IL-6, as well as the signaling of NF-κB. The application of CoCl2 in cultured RFF cells triggered the hypoxia-induced cell death and up regulation of HIF-1α. As expected, applied SBA extract in the cultures prevented the hypoxia-induced signaling. Our results show the established RFF cell line may be served as an ideal in vitro model in drug screening relating to inflammation and hypoxia. Additionally, we are supporting the usage of SBA herbal extract in fish aquaculture, which possesses efficacy against inflammation and hypoxia.

Identification compound content of rabbit fishes (Siganus sp.) by using GCMS

ObjectiveThis study aims to identify the content of compounds contained in flesh, skin, and liver in rabbit fishes (Siganus sp.). MethodsThe study was conducted in several stages namely: the first stage, sampling of rabbit fishes (Siganus sp.); the second step, sample preparation on the flesh, skin, and liver; and the third stage, sample analysis using Pyrolysis Gas Chromatography-Mass Spectroscopy (Py-GCMS) with Shimadzu P2010 type. ResultsFormamide, which is also known as methanamide, is an amide derived from formic acid, found in the flesh of rabbit fishes (Siganus sp.) with a concentration of 13.09%, and the skin of rabbit fishes (Siganus sp.) with a concentration of 8.34%. In addition, the compound methenamine is found in the skin of rabbit fishes (Siganus sp.) with a concentration of 13.71%. While on the skin of rabbit fishes (Siganus sp.) also the composition of methyl maltol with a concentration of 14.36%, and 1,4-diaza-2,5-dioxobicyclo[4.3.0]nonane with a concentration of 17.07%. In addition, the liver of rabbit fishes (Siganus sp.) contained ammonium carbamate compound with a concentration of 24.77%, dodecanoic acid with a concentration of 5.98%, and ketone with a concentration of 6.48%. ConclusionThe concentration of compounds in flesh, skin, and liver in rabbitfish (Siganus sp.) can be identified using Pyrolysis Gas Chromatography-Mass Spectroscopy (Py-GCMS) where there are a number of useful compounds, but further research is still needed.

Fish culture technology using double net system for hybrid grouper (brown marbled grouper Epinephelus fuscoguttatus × giant grouper Epinephelus lanceolatus) and rabbitfish (Siganus canaliculatus)

Fish culture technology using double net system based on trophic level predicted can improve productivity. The aim of this research was to evaluate a fish culture technology of grouper and rabbitfish using double net system based on trophic level. This research was conducted with different stocking density. The net used was double net system. The Outer net HDPE with four cage with size of 4 × 4 × 4 m/cage and inner net HDPE with size of 3 × 3 × 3 m/cage. Inner net cage was stocked 20 grouper fish/m3 while outer net was stocked with different density of rabbit fish, 6 fish and 12 fish/m3. Each treatment was duplicated. The result showed the hybrid grouper production up to 205 kg with an individual final weight of 743 g while production of rabbit fish with stocking density 6 and 12 fish/m3 consequently was 10 kg with an individual final weight of 143 g and 15 kg with an individual final weight of 148 g. N and P content in hybrid grouper meat from feed consumed were 25% total N and 11 % total P, however 52 % of N and 74 % of P were released as faeces and excretion to the water. Rabbitfish with stocking density of 12 fish/m3 was the most effective production using double net system.

The anti-bacterial effects of aerial parts of Scutellaria baicalensis: Potential application as an additive in aquaculture feedings

The root of Scutellaria baicalensis (Scutellaria Radix) is a medicinal part being used as a herbal drug; while its stem and leaf (aerial part) are considered as waste. Several reports have shown that aerial part of S. baicalensis (SBA) has chemical similarity with its root, suggesting the possible usage of this non-medicinal part. Thus, the usage of SBA as an additive in aquaculture feeding could be a new way to recycle the waste. The water extract of SBA inhibited the growth of several common pathogenic bacteria in aquaculture, e.g. Aeromonas hydrophila, Edwardsiella tarda, Vibrio alginolyticus and Vibrio harveyi. In cultured macrophage cells (RAW 264.7), application of SBA extract showed strong anti-inflammation effect, which inhibited the expression of inflammatory cytokine, i.e. IL-1β, as induced by LPS. Similarly, SBA extract suppressed the LPS-induced transcriptional activity mediated by NF-κB. When applied in fish aquaculture, the extract of SBA was mixed into the feedings of Siganus fuscescens (rabbit fish) that was cultured with a mixture of pathogenic bacteria. The expression levels of COX-2, IL-1β and TNF-α were markedly reduced in the present of SBA extract. Our investigations show the anti-bacterial effect of SBA extract, as well as its potential anti-inflammation effects both in vitro and in vivo, which therefore suggest the possible development of S. baicalensis aerial part in fish aquaculture.

Molecular circumscription of new species of Gyrocotyle Diesing, 1850 (Cestoda) from deep-sea chimaeriform holocephalans in the North Atlantic

Chimaeras, or ratfishes, are the only extant group of holocephalan fishes and are the sole host group of gyrocotylidean cestodes, which represent a sister group of the true tapeworms (Eucestoda). These unique, non-segmented cestodes have been known since the 1850s and multiple species and genera have been erected despite a general agreement that the delineation of species on the basis of morphology is effectively impossible. Thus, in the absence of molecular studies, the validity of gyrocotylid taxa and their specific host associations has remained highly speculative. Here we report the presence of Gyrocotyle spp. from rarely-caught deep-sea chimaeras collected in the North-East Atlantic, and describe two new species: G. haffii n. sp. from the bent-nose chimaera, Harriota raleighana Goode & Bean, and G. discoveryi n. sp. from the large-eyed rabbit fish, Hydrolagus mirabilis (Collett). Nuclear ribosomal sequence data were generated for individual parasites taken from different host species collected on different dates and from different localities and were combined with previously published sequences. Phylogenetic analyses supported the recognition of independent lineages and clusters, indicative of species, but were indecisive in recovering the root of the tree in analyses that included non-gyrocotylid outgroup taxa. The molecular data reveal variation not reflected in morphology and point to a complex picture of genetic divergence shaped by both isolation and migration in the deep-sea environment.