Bradophilidae Marchenkov 2002

Family Bradophilidae Marchenkov, 2002

Marchenkov (1999) suggested that the monotypic genus Bradophila belonged in a separate family and formally established it a few years later (Marchenkov 2002). The Bradophilidae is one of six families of mesoparasitic copepods which have adult females that are highly transformed and live partially embedded in their polychaete hosts, the other five being the Herpyllobiidae, Jasmineiricolidae, Phyllodicolidae, Saccopsidae and Xenocoelomatidae (Boxshall et al. 2015). Members of the latter family are radically different, mostly internal, parasites maintaining only a small aperture through the host’s body wall through which paired egg sacs are extruded. Adults of both sexes lack all trace of appendages and the three known species are cryptogonochoristic, with males reduced to a functional testis housed within a receptaculum masculinum inside the female body (Bresciani & Lützen 1974). In the Saccopsidae both the ovaries and digestive system are contained within the external sac-like body which connects via a short stalk with the internal holdfast or frontal bulla. The latter is a simple ring-shaped thickening of the cuticle surrounding the oral region and penetrates the blood vessels of the host’s gills (Bresciani & Lützen 1961) or opens into the connective tissues of the body wall (Bresciani & Lützen 1975). Adult females of the other four families share a bipartite body comprising an ectosoma lying external to the body wall of the host, and an endosoma which is embedded within the host. In the sole member of the Jasmineiricolidae the female reproductive organs are located in the endosoma (Boxshall et al. 2015) while in adult females of the Herpyllobiidae and Phyllodicolidae the ectosoma is essentially the reproductive tagma, containing the ovaries. The condition in the Bradophilidae remains equivocal (see below). Adult females in the family Phyllodicolidae have a unique type of endosoma, represented by a pair of elongate rootlets, and, rather than producing genuine egg sacs, attach their eggs separately to an axial filament originating at the genital aperture (Delamare-Deboutteville & Laubier 1960a; Laubier 1961). Members of the remaining two families, Herpyllobiidae and Bradophilidae, differ from each other primarily in the structure of the female endosoma and the gross morphology of the male (e.g. Lützen 1966; Marchenkov 2002, López-González et al. 2006). Males of Bradophila have large prehensile antennae, robust subchelate maxillipeds and conspicuous caudal processes, all of which are used to attach to the ectosoma of the female (Marchenkov 2002; this study). The highly reduced males in the Herpyllobiidae all lack appendages (except for a pair of putative maxillipeds in Gottoniella López-González, Bresciani & Conradi, 2006). While herpyllobiids have dwarf males, typically being at least an order of magnitude smaller than the female, such extreme size sexual dimorphism is not encountered in the Bradophilidae. Unlike in Bradophila, male attachment in the Herpyllobiidae appears to be by means of a secretion in the vicinity of the genital apertures of the female. In addition to the type genus, the poorly known genera Trophoniphila and Flabellicola Gravier, 1918a are here also included in the family on the basis of the absence of cephalic appendages in the adult female, the shape and size of the egg sacs and their utilization of bristle-cage worms (Flabelligeridae) as hosts. Since both genera are only known from the less informative mesoparasitic female it is possible that they will be relegated to junior subjective synonyms of Bradophila when information about their respective males becomes available. Bradophilids are very rarely reported but it is known that other as yet undescribed species occur in European waters (Boxshall et al. 2015).