Multidisciplinary approach to the diagnosis of Contracaecum magnipapillatum infections in Australian black noddies, Anous minutus (Charadriiformes: Laridae)

Abstract

We provide the incidental necropsy findings associated with anisakid nematode infections of black noddy terns, Anous minutus Boie, 1844 (Charadriiformes: Laridae), from offshore islands in the southern Great Barrier Reef, Queensland, Australia. Specimens collected from the proventriculi were identified morphologically as Contracaecum magnipapillatum Chapin, 1925 (Rhabditida: Anisakidae), using light and scanning electron microscopy (SEM). The entire nuclear ribosomal DNA internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2) was amplified by polymerase chain reaction (PCR) and sequenced to provide reference sequences for morphologically well-identified voucher specimens. Interestingly, after an alignment with closely related taxa using BLAST, sequences of the ITS1 and ITS2 were 100% identical to the sequences assigned to Contracaecum septentrionale Kreis, 1955, from a razorbill, Alca torda Linnaeus, 1758 (Charadriiformes: Alcidae), from Spain. These results either raise questions about the ITS as a genetic marker for some members of Contracaecum, or the identity of the specimens assigned to C. septentrionale, given that no supporting morphological data was associated with them. We highlight the need for a combined morphological and molecular approach to parasite diagnostics and the use of multiple genetic loci to resolve the molecular taxonomy of cryptic species. Morphological identifications should be taxonomically robust, transparent and precede the deposition of molecular barcodes in public repositories. The gross and histopathological findings of our investigation concur with previous reports of widespread Contracaecum infections in black noddies and support the contention that Contracaecum spp. are an unlikely primary cause of mortality.

Gill parasites of Schizocypris altidorsalis (Pisces: Cyprinidae), a threatened freshwater fish in Iran

“…Dos Santos and Avenant-Oldewage (2020) reviewed currently available genetic data, to uncover insights from the current sequence data, suggested improvements for future studies, and highlighted potential pitfalls to be avoided. Like several other studies about other parasitic taxa (Barton et al 2022;Shamsi et al 2024), Dos Santos and Avenant-Oldewage (2020) pleaded for a more integrated taxonomic approach and the inclusion of voucher material alongside the sequence data obtained from several additional markers, and concluded that analyses of a substantial amount of further morphological and genetic data are needed before an accurate study of the taxonomy and evolutionary history of diplozoid species can be achieved. These challenges over specific identification of the existing taxa makes introducing a new species challenging.…”