Huffmanela lusitana sp. n. (Nematoda: Trichosomoididae) infecting pouting, Trisopterus luscus (Teleostei: Gadidae) off the Atlantic coast of Portugal

Paula Ramos,Raquel Carvalho,Graça Alexandre-Pires,Fernanda Rosa,David Huffman,Fernanda Seixas,Alexandra Esteves

doi:10.1016/j.ijppaw.2019.05.010

Abstract

Some pouting caught off the Atlantic coast of Portugal are discarded as unmarketable due to a dark discolouration of the skin and muscle. This study investigates the cause of this condition, describes the new parasite species responsible, and highlights the importance of educating those in charge of premarket inspection of food fish in order to reduce likelihood that consumers will eat infected fish. Macroscopically, infected fish showed considerable heterogeneity in darkening of the skin and hypaxial and epaxial muscles. Microscopical observation revealed bipolar nematode eggs in varying stages of development arranged in a linear pattern along muscle fibers. Histopathology confirmed the presence of eggs of a nematode of the genus Huffmanela Moravec, 1987 as the cause of muscle darkening and established a relationship between infection intensity and consequent darkened appearance of the tissues. The eggs are oval or barrel-shaped, with a smooth surface and polar plugs at opposite ends. The thin outer vitelline membrane is smooth and lacks ornamentation. Under light microscopy, the main eggshell of older eggs exhibits the outermost delicate and smooth vitelline membrane, and a thicker layer, correspondent to chitinous and chondroitin proteoglycan layers. Scanning electron microscopy of eggs confirmed light microscopic studies, namely the presence of a smooth vitelline membrane surrounding the egg. Microscopic and ultrastructural characteristics of eggs, and a new host family in a new geographic area, all suggest that a new species, herein named Huffmanela lusitana sp. n. is involved.

Highlights

Fish consumption in Portugal is reported as 62 kg/year/person (FAO, 2010), which makes Portugal the largest consumer of fish in the European Union (EU)
Muscle infecting Huffmanela species are distinct from H. lusitana sp. n. based on one or more of: size and morphology of eggs, host, taxonomy, infected tissue, and geographic locality
In H. banningi the vitelline membrane is spinous, but it is smooth in H. lusitana sp. n

Summary

Introduction

Fish consumption in Portugal is reported as 62 kg/year/person (FAO, 2010), which makes Portugal the largest consumer of fish in the European Union (EU). (Trichinelloidea: Trichosomoididae) nematodes infecting muscles of pouting was reported by Ramos (IPMA Report, 2002; unpublished data) This first data was presented in a scientific meeting (Mendes et al, 2005) and afterwards resulted in an MSc thesis by Mendes (2006), who described a “range of colour change” of infected pouting to support veterinarian control of fishery products. Later, this Huffmanela infection was revisited (Esteves et al, 2009), but the species remained unidentified. Another population of Huffmanela sp. was discovered (Esteves et al, 2016) in a fish from a new host and family, Microchirus azevia (Pleuronectiformes: Soleidae) caught off the Portuguese coast, which possibly represents yet another species

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