# Lobosorchis labri n. sp. (Trematoda: Cryptogonimidae): a host switch from snappers (Lutjanidae) to wrasses (Labridae)

## TL;DR

A new species of trematode was found in wrasse fish, indicating a recent host switch from snapper fish, with new species and genetic data reported.

## Contribution

The first cryptogonimid trematode with adults in wrasses is described, along with two new species and evidence of a recent host switch.

## Key findings

- Lobosorchis labri is the first cryptogonimid with adults in wrasses, showing a host switch from snappers.
- Two new species of Lobosorchis were identified, and uncharacterized genetic diversity was detected.
- Piscivory in Hemigymnus wrasses is confirmed through gut content analysis and parasite infection patterns.

## Abstract

The first cryptogonimid trematode with adults parasitic in wrasses (Labriformes: Labridae) is proposed. Lobosorchis labri n. sp. was recovered at a substantial combined prevalence (63%, 15 of 24) from the thicklipped wrasses Hemigymnus melapterus (Bloch) and H. fasciatus (Bloch) at Ningaloo Reef, Western Australia. Definitive hosts for all other Lobosorchis spp. are exclusively tropical snappers, Lutjanus spp. (Lutjaniformes: Lutjanidae). Novel material for Lobosorchis spp. collected from snappers is also reported, including for L. tibaldiae Miller & Cribb, 2005 and L. polygongylus Miller et al., 2009, a new species L. milleri n. sp., and novel genetic data and host-locality combinations for what are interpreted as uncharacterised species, from Ningaloo Reef, the Great Barrier Reef off eastern Australia, French Polynesia, and Okinawa, Japan. Lobosorchis labri has evidently speciated following a host switch from snappers into wrasses. Based on comparison of genetic differences among Lobosorchis spp., this switch has occurred recently, in evolutionary terms, yet sufficiently distantly such that L. labri is now apparently specific for Hemigymnus spp. and no longer infects snappers; infections of Lobosorchis spp., but not L. labri, were detected in sympatric snappers at Ningaloo Reef. Cryptogonimids were not detected in our examinations of 98 individuals of Hemigymnus spp. on the Great Barrier Reef; L. labri seemingly does not occur there, and thus the host switch which gave rise to this species likely occurred somewhere in the Indian Ocean. Piscivory in Hemigymnus spp. is reported, implied by infection of cryptogonimids and confirmed via examination of gut contents.

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•First cryptogonimid trematode with sexual adult parasitic in wrasses.•Host switch of a trematode from snappers to wrasses.•Two new Lobosorchis spp. proposed, and further uncharacterised richness detected.•Substantial and widespread piscivory reported in Hemigymnus wrasses.

First cryptogonimid trematode with sexual adult parasitic in wrasses.

Host switch of a trematode from snappers to wrasses.

Two new Lobosorchis spp. proposed, and further uncharacterised richness detected.

Substantial and widespread piscivory reported in Hemigymnus wrasses.