Morphology and molecular phylogeny of Heterobothrium lamothei (Monogenea: Diclidophoridae), a gill parasite infecting the tiger puffer fish Lagocephalus sceleratus (Tetraodontidae)

K Morsy,A Ali,J.S Al-Malki,H Hamdi,A Adel,S.B Dajem

doi:10.1590/1678-4162-12303

Abstract

ABSTRACT Members of the family Diclidophoridae are potentially dangerous species for the puffer fish aquaculture worldwide. They are parasitic polyopisthocotyleans, with a posterior haptor equipped with clamps for attachment to the host's surface, allowing the worm to resist the flow of water to maintain its position on gills. The anterior body of the worm is deformable, allows the worm to feed on blood sucked from fish gills. The present study is the first description of a Heterobothrium species from the gills of the tiger puffer Lagocephalus sceleratus (Tetraodontidae) from the coasts of the Arabian Gulf at Jubail, Saudi Arabia morphologically by light microscopy as well as by molecular analysis of the parasite partial 28S rRNA through multiple sequence alignments and phylogeny by maximum likelihood analysis which is provided for the first time for the described species. Seventeen tiger puffer fish were captured alive from marine water off Saudi Arabia; gills were separated and further examined for parasitic infection. Nine fish were found infected with a monogenean parasite which was robust, equipped by two buccal organs at the tapered anterior end; the posterior haptor was rectangular with four symmetrically arranged clamps, with no isthmus. Marginal hooks absent. Ovary elongated, U-shaped, testes numerous, irregularly shaped and extended from the posterior part of the ovary to the anterior margin of the haptor. Copulatory organ muscular, as a spherical cup armed with 12 to 15 genital hooks. The molecular analysis of the parasite 28s rRNA and phylogeny revealed a percentage of identities between 87.47-89.09%, with Diclidophoridae species within the monophyletic clade of Mazocraeidea where a maximum percentage of 89.09% were obtained for the morphologically different sister taxon H. okamotoi. The results obtained from molecular analysis are consistent with the conclusions drawn from morphological classification where that the parasite recorded was morphologically similar to H. lamothei which was not characterized by molecular analysis before. The recovered sequences were deposited into the GeneBank under accession number MT322610.

Highlights

Monogeneans are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish
The present study is the first description of a Heterobothrium species from the tetraodontid L. sceleratus from coasts of the Arabian Gulf at Jubail, Saudi Arabia morphologically by light microscopy as well as molecular analysis of the parasite partial 28S rDNA which is provided for the first time for the recovered species
H. okamotoi has been found to be a problem for Japanese aquaculture of the puffer fish Takifugu spp., it is morphologically different from the present species; it is longer (45–67.7), with a haptor separated from the body proper by a slender isthmus

Summary

Introduction

Monogeneans are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. The genus Heterobothrium Cerfontaine (1895) of family Diclidophoridae Sproston (1946), is highly specific to tetraodontid fishes (Actinopterygii: Tetraodontidae), including 11 blood-feeding species of monogeneans infecting the gills (Williams, 1986; Ogawa, 1997) with high species diversity and host specificity (Boeger and Kritsky, 2001; Desdevises et al, 2002; Šimkova et al, 2006) Immature worms of these parasites attach to the gill filaments of their hosts, feeding on the blood, causing impaired breathing and anemia to their hosts, and migrate to the buccal cavity wall for maturation (Matsui et al, 2020). The present study is the first description of a Heterobothrium species from the tetraodontid L. sceleratus from coasts of the Arabian Gulf at Jubail, Saudi Arabia morphologically by light microscopy as well as molecular analysis of the parasite partial 28S rDNA which is provided for the first time for the recovered species

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