Molecular characterization of Hysterothylacium aduncum (Nematoda: Raphidascaridae) from different fish caught off the Tunisian coast based on nuclear ribosomal DNA sequences

Abstract

Larval forms of the genus Hysterothylacium have been previously reported in teleost fish from the North African coasts of central Mediterranean Sea by morphological analysis. In the present study, samples identified morphologically as Hysterothylacium aduncum (n = 62), from Merluccius merluccius, Trachurus mediterraneus and Pagellus erythrinus from different geographical locations of the Tunisian coasts, were genetically characterised by sequences of the first (ITS-1), the 5.8S and second (ITS-2) Internal Transcribed Spacers (ITS) of nuclear ribosomal DNA (rDNA). Comparison of the sequences obtained with those available in public gene databases confirmed that all the samples from the Tunisian coasts belong to a single species, namely H. aduncum. All specimens from the Tunisian coasts showed one indel in position 787 in ITS-2 sequences not reported by any of the previously published sequences from the Atlantic and Pacific Oceans, Adriatic Sea (Mediterranean Sea) and the East Greenland Sea, suggesting the existence of a population-specific pattern exhibiting a low differentiation of this parasite in this area. This is the first molecular characterization of H. aduncum from the Tunisian coasts using ITS rDNA sequences which allows the definition of genetic markers for their unequivocal identification, and provides further biological data on these nematodes in marine fish off the Tunisian coasts, improving the picture of the occurrence of these taxa in the North African coasts of central Mediterranean Sea.

Molecular identification of Hysterothylacium aduncum specimens isolated from commercially important fish species of Eastern Mediterranean Sea using mtDNA cox1 and ITS rDNA gene sequences

“…Nucleotide sequences of L4 stage larvae of H. aduncum specimens isolated from three commercially important fish species caught off the Eastern Mediterranean cost are also shown to be effective in molecular identification at species level, using both ITS rDNA and mtDNA cox1 regions. Results indicated that the ITS rDNA sequences from our study are highly similar to those already submitted to GenBank in previous studies [1,19,26,42,[45][46][47]. We were not able to compare mtDNA cox1 sequences, as this is the first molecular study using mtDNA cox1 sequences in identification of H. aduncum.…”

“…Previous studies based on nucleotide sequences of ITS rDNA gene clearly demonstrated the effectiveness of this genetic marker in molecular identification of ascaridoid species [1,19,26,[39][40][41][42][43][44]. Nucleotide sequences of L4 stage larvae of H. aduncum specimens isolated from three commercially important fish species caught off the Eastern Mediterranean cost are also shown to be effective in molecular identification at species level, using both ITS rDNA and mtDNA cox1 regions.…”

“…Klimpel et al [1], Amor et al [26], and Farjallah et al [11] determined population-specific patterns with the different localities off the Tunisian coasts. Vardić Smrzlić et al [17] provided some data on the molecular characterization of Anisakidae larvae from Adriatic Sea and recently Guo et al [27] used molecular methods by sequencing and analyzing the internal transcribed spacer (ITS) of nuclear ribosomal DNA (rDNA).…”

Morphological and genetic characterization of Hysterothylacium Ward & Magath, 1917 (Nematoda: Raphidascarididae) larvae in horse mackerel, blue whiting and anchovy from Spanish Atlantic and Mediterranean waters

“…Hysterothylacium constitutes a large number of described species, approximately 70, which have been recorded in marine fishes worldwide (Li, Gibson et al., ; MacKenzie et al., ; Pekmezci et al., ; Shamsi et al., ). In Mediterranean and North‐East Atlantic waters, H. aduncum (Rudolphi, 1802) is the most frequently reported species in many teleost fishes, but other species such as H. fabri (Rudolphi, 1819) Deardorff & Overstreet, 1980; H. corrugatum Deardorff & Overstreet, ; H. incurvum (Rudolphi, 1819) Deardorff & Overstreet, 1980; and H. petteri Sheenko, 1991 have also been recorded (Amor, Farjallah, Merella, Said, & Slimane, ; MacKenzie et al., ; Mattiucci et al., ; Ternengo, Levron, Mouillot, & Marchand, ). Up to 17 Hysterothylacium larval morphotypes have been described, based mainly on the anterior digestive tract and the caudal end of larvae, the first description in Australian marine waters being by Cannon ().…”

Ege Bölgesi Akarsularında Yakalanan Avrupa Yılan Balıklarında (Anguilla anguilla Linnaeus, 1758) Raphidascaris acus Bloch, 1779 (Nematoda: Anisakidae)’un İlk Moleküler Karakterizasyonu

“…However, to date there has not been any study regarding molecular characterization of R. acus from fish caught off the Turkish waters. Recently, molecular techniques, using DNA sequencing of the nuclear ribosomal DNA spacers, have been proven to be particularly useful for the accurate identification of ascaridoid nematodes at the species level for eggs, larvae, and adults [5][6][7][8][9][10][11][12] . Nevertheless, before the present study, there had been no reports of characterizing the R. acus from the Turkish waters using well-defined internal transcribed spacers (ITS1 and ITS2) and 5.8S region sequence.…”