Morphological and Molecular Diagnosis of Anisakid Nematode Larvae from Cutlassfish (Trichiurus lepturus) off the Coast of Rio de Janeiro, Brazil

Abstract

Anisakid nematode larvae from Trichiurus lepturus off coast of Rio de Janeiro were studied using light, laser confocal and scanning electron microscopy, in addition to a molecular approach. Mitochondrial cytochrome c-oxidase subunit 2 (mtDNA cox-2), partial 28S (LSU) and internal transcribed spacers (ITS-1, 5.8S, ITS-2) of ribosomal DNA were amplified using the polymerase chain reaction and sequenced to evaluate the phylogenetic relationships between the nematode taxa. The morphological and genetic profiles confirmed that, of the 1,030 larvae collected from the 64 fish examined, 398 were analysed, of which 361 were Hysterothylacium sp. and 37 were Anisakis typica. Larvae of Hysterothylacium sp. were not identified to the species level due to the absence of similar sequences for adult parasites; however, the ITS sequence clustered in the phylogenetic tree with sequences of H. deardorffoverstreetorum, whereas an mtDNA cox-2 and LSU concatenated phylogenetic analysis demonstrated the presence of two clades, both of them under the same name as the larval H. deardorffoverstreetorum. Data on the occurrence of parasites during the winter and summer months were compared using the t-test. The greatest prevalence and intensity of infection were recorded for larval Hysterothylacium, with a prevalence of 51.56% and an intensity of up to 55 parasites per fish. The larval Anisakis exhibit a higher abundance and intensity of infection in the winter months, and those of Hysterothylacium during the summer. However, the t-test indicated no significant differences between the abundance and intensity of infection recorded during the months of collection for either of these larval nematodes. All sequences generated in this study were deposited in GenBank.

Genetic identification of anisakid nematodes isolated from largehead hairtail (Trichiurus japonicus) in Korea

“…The high prevalence of Anisakis species in fish hosts in this study is therefore thought to reflect the richness of micro/macroinvertebrates and possibly subsequently have relations with the biomass of other predators such as pinnipeds and cetaceans in waters investigated. Several papers also reported relatively a high prevalence of anisakid nematodes larvae in the largehead hairtail (Borges et al 2012;Kong et al 2015;Umehara et al 2010), as in this study. The low number of the nematodes larvae in the previous study (Lee et al 2009) may just reflect the low abundance of micro/macroinvertebrates in the areas where the largehead hairtail were caught.…”

“…Several papers described anisakid nematodes L3 from the largehead hairtail (Borges et al 2012;Kong et al 2015;Lee et al 2009;Shih 2004;Umehara et al 2010;Zhang et al, 2013), but there was no report in which T. japonicus was mentioned as host species, except for our study. It is not clear if the host species mentioned was in fact T. japonicus or other Trichiurus species in their studies because the identification of host species was not clearly conducted.…”

“…There have been many papers regarding anisakid nematodes isolated from Trichiurus species (Borges et al 2012;Kong et al 2015;Lee et al 2009;Shih 2004;Umehara et al 2010;Zhang et al 2013). But, the identification of host species was not clearly conducted, and several scientific names (e.g., Trichiurus lepturus, Trichiurus haumela, Trichiurus sp.)…”

Parasite community of Pagrus pagrus(Sparidae) from Rio de Janeiro, Brazil: evidence of temporal stability

“…by Paraguassú et al (2002). In species of Hysterothylacium, the excretory pore is located in the region of the nerve ring, thus differing from species of Contracaecum, in which it is located near the ventral interlabia (DEARDORFF; OVERSTREET, 1981;RUKERT., 2005;KLIMPEL et al, 2007;KNOFF et al, 2012;BORGES et al, 2012). According to Smith and Wooten (1978), although it is difficult to identify species based on morphological characters alone, it is even more difficult in relation to the larval stages.…”

Molecular and morphological characterization of Contracaecum pelagicum (Nematoda) parasitizing Spheniscus magellanicus (Chordata) from Brazilian waters

“…Genomic DNA was extracted using a ChargeSwitch gDNA Mini Tissue Kit (Invitrogen, Carlsbad, CA, USA) and in order to amplify gene fragments of Contracaecum; the primers 211F/210R for mtDNA cox-2 (NADLER; HUDSPETH, 2000) were used in PCR reactions following Borges et al (2012). Amplified PCR products were purified with Wizard® SV gel and PCR clean up system kit (Promega, Madison, USA), and sequenced using the same primer set.…”