Galactosomum otepotiense n. sp. (Trematoda: Heterophyidae) infecting four different species of fish-eating birds in New Zealand: genetically identical but morphologically variable

Abstract

Trematodes of the genus Galactosomum are cosmopolitan parasites that infect the intestines of fish-eating birds and mammals. Adults of named Galactosomum species have not been recorded from bird hosts in New Zealand, despite their cercarial stage being known from various studies of the first intermediate host, Zeacumantus subcarinatus. Here we describe a new species of Galactosomum infecting four different piscivorous birds in New Zealand: Caspian terns, red-billed and black-backed gulls and little blue penguins. Specimens from each of these hosts are genetically identical in the genes sequenced, but show considerable morphological variability. Galactosomum otepotiense n. sp. is distinguished from most other members of the ‘bearupi-group’ in having a single circle of spines on the ventral sucker, and spines, as opposed to scales, over most of the body. It is most similar to G. bearupi and G. angelae, both from Caspian terns in Australia, but differs in the relative sizes of the reproductive organs and in the possession of a very long forebody. Molecular data confirm that G. otepotiense is not conspecific with G. bearupi, but 28S and ITS2 phylogenies show its close relationship to G. bearupi and other Australian species. We use the cox1 sequence to confirm identity with the larval stage infecting Z. subcarinatus, as previously described in the literature. We discuss briefly the relationships between Australian and New Zealand Galactosomum spp. and their hosts, variability between genetically identical specimens found in different hosts and their potential for harm to mariculture economy.

Annotated checklist and genetic data for parasitic helminths infecting New Zealand marine invertebrates

“…References . Leung, Donald, et al (2009); Lloyd and Poulin (2011); Martorelli et al (2008); Presswell and Bennett (2020).…”

“…Remarks . Before its description in 2019 (Presswell & Bennett, 2020), Galactosomum otepotiense was called Galactosomum sp. by the above authors.…”

“…The adult of this species was described from four different piscivorous birds: Caspian tern, Hydroprogne caspia ; red‐billed gull, Chroicocephalus scopulinus ; kelp gull, Larus dominicanus ; and little penguin, Eudyptula novaehollandiae (Presswell & Bennett, 2020). Type specimens are deposited at the Te Papa Museum, Wellington (accession numbers W.003498–W.003502) and the Otago Museum, Dunedin (accession numbers IV107611–IV107616).…”

“…This also means that they usually cannot be matched to parasite species already known from their adult forms. Genetic tools are increasingly overcoming this limitation, allowing parasitologists to match larval forms from intermediate hosts with adult forms from definitive hosts (e.g., Bennett & Presswell, 2019; Presswell & Bennett, 2020). This is a crucial next step in the discovery of invertebrate parasite biodiversity, which will allow resolution of complete life cycles, provide appropriate taxonomic identifications, and compare between closely related species, geographic areas, and other life stages within multiple hosts (Blasco‐Costa & Poulin, 2017).…”

Decay of parasite community similarity with host phylogenetic and geographic distances among deep-sea fish (grenadiers)

“…DNA was extracted using the Chelex extraction method (Walsh et al, 1991). We used primers T16 and T30 from Harper and Saunders (2001) to resolve a partial fragment of the 28S gene for digeneans (∼600 bp length) and cestodes (∼700 bp length) following the PCR conditions from Presswell and Bennett (2020). For nematodes, a partial fragment of the 18S gene was resolved (∼800 bp length) using primers Nem18SF and Nem18SR from Wood et al (2013) following PCR conditions of Prosser et al (2013).…”