Morphological and molecular identification of ascaridoid nematodes (Nematoda: Ascaridodea) in mackerel scad, Decaptures macarellus (Cuvier, 1833 [manuscript]
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Date
2018
Authors
Aries Paul D. Padron
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Abstract
The study aims to identify and determine the prevalence (P), mean intensity (ml) and abundance (Ab) of anisakid nematodes present in mackerel scad, Decapterus macarellus, a common fish food in Bolinao, Pangasinan. Identification was based in morphological and molecular approaches. Morphological approach was used to identify in genus level while molecular approaches were employed to identify at species level based on cytochrome oxidase subunit 1 (COI) region of mitochondrial DNA (mtDNA). Subsequent analysis such as, density of nematodes based on length and weight classes, Pearson correlation between length and weight of fish to number of nematodes, curvilinear regression analysis and phylogenetic analysis were also executed. Significant findings in this study were; four genera of anisakid nematodes were identified namely, Anisakis sp. (P=18%,ml=2.28, Ab=0.41), Terranova sp. (P=31%,ml=2.71, Ab=0.84),Raphidascaris sp. (P=7%, ml=1.29,Ab=0.09), Hysterothylacium sp. (P=7%, ml=1.14, Ab=0.08) and an unidentified nematodes (P=14%, ml=1.86, Ab=0.26), correlation and regression analysis between weight of fish to number of nematodes revealed an inverse/negative relatioship. Furthermore, a zoonotic parasite species, A. simplex, were identified base on molecular techniques, unidentified parasite species, A. simplex, were identified base on molecular techniques, unidentified nematodes remained unidentified even at molecular level that is suspected to be a different species of ascaridoid nematodes. Phylogenetic analysis revealed that A. simplex (sample V4), sample V3 (unidentified), and sample VI (morphologically identified as Terranova sp.) were monophyletic, that is, they were originated from one ancestor.