Occurrence and molecular identification of nematodes from blue mackerel Scomber australasicus Cuvier in Australian waters

This study determines the occurrence and molecular identification of nematodes from blue mackerel Scomber australasicus Cuvier (Perciformes: Scombridae), an edible fish from Australian waters. A total of 150 fish were sourced from the New South Wales and Victorian coasts. Nematodes were initially classified morphologically as 10 morphotypes belonging to the families Anisakidae (Anisakis morphotypes I and II, Contracaecum morphotype II, Terranova morphotypes I and II), Raphidascarididae (Hysterothylacium morphotypes IV, VI, VIII, and XIV), and Capillariidae (Capillaria sp.), followed by molecular identification through sequencing of their internal transcribed spacer (ITS-1, 5.8S, ITS-2) region. Anisakis morphotype I was confirmed as A. pegreffii Campana-Rouget & Biocca, 1955 and A. berlandi Mattiucci, Cipriani, Webb, Paoletti, Marcer, Bellisario, Gibson & Nascetti, 2014. Anisakis morphotype II and Contracaecum morphotype II were confirmed as A. physeteris Baylis, 1923 and C. ogmorhini Johnston & Mawson, 1941, respectively. Terranova morphotypes I and II were identified as Pulchrascaris australis Shamsi, Barton & Zhu, 2020 and Euterranova pectinolabiata n. comb. (Shamsi, Barton & Zhu, 2019) Moravec & Justine, 2020, respectively. The specific identification of Hysterothylacium morphotypes IV, VI, and VIII was not possible as no comparable adult Hysterothylacium species sequences were available in GenBank, with the exception of morphotype XIV which was confirmed as H. persicum Shamsi, Ghadam, Suthar, Mousavi, Soltani & Mirzargar, 2016. Seven nematode morphotypes were identified for the first time in Australian blue mackerel. The outcomes of the study provide a basis for future research into the community structure, life cycles, and distribution of nematode species in Australian mackerel and to analyse and clarify their importance for public health.