Herpyllobius Steenstrup & Lütken, 1861

Boxshall, Geoff A., O’Reilly, Myles, Sikorski, Andrey & Summerfield, Rebecca, 2019, Mesoparasitic copepods (Copepoda: Cyclopoida) associated with polychaete worms in European seas, Zootaxa 4579 (1), pp. 1-69 : 9-10

Genus Herpyllobius Steenstrup & Lütken, 1861

Diagnosis. Adult female ectosoma spherical to ovoid or dorsoventrally flattened, bilaterally symmetrical, with prominent and heavily sclerotized paired genital openings posteriorly. Stalk originating on ventral surface in midline, anterior to genital openings. Endosoma varying in shape from irregular 3-dimensional mass, with or without rounded or digitiform lobes, to elongate or discoid flattened process. No vestiges of limbs retained in adult female. Egg sacs paired, multiseriate. Adult male attached to ectosoma of female by means of frontal process; body unsegmented, limbless, bottle-shaped containing paired spermatophores.

Late male copepodid cyclopiform, comprising 4-segmented prosome and 3-segmented urosome. Antennule 3- segmented. Maxilliped subchelate. Legs 1 and 2 biramous, with 2-segmented exopods and 1-segmented endopods. Leg 3 biramous, with 1-segmented rami. Leg 4 represented by single seta. Nauplius lecithotrophic, lacking naupliar eye.

Type species: Herpyllobius arcticus Steenstrup & Lütken, 1861 , by monotypy.

Remarks. Males of Herpyllobius attach in the vicinity of the genital apertures of the female and often remain within the exuvium of the preceding final copepodid stage. They have an unsegmented, limbless and bottle-shaped body which is attached to the ectosoma of the female by the slender anterior region (the “neck” of the bottle), secured by means of a secretion produced by a frontal gland ( Lützen 1966). Males typically attach in the vicinity of the sclerotized dots in the female genital region in species such as H. polynoes ( Krøyer, 1864) and H. arcticus , or near the sclerotized swelling located between the genital apertures in species such as H. cordiformis Lützen, 1964 ( Lützen 1966) . Lützen (1966) stated that Herpyllobius males “emit two very long and slender tubes from their frontal part; these are extensions from a pair of sacs”. Levinsen (1878) and Hansen (1892, 1900) considered these sacs to be the testes whereas Jensen (1900) interpreted them as spermatophores. Lützen (1964a, 1966) interprepted them as most likely spermatophores and observed that their tubules “enter the female genital openings” and “introduce the contents of the spermatophores into the receptaculum seminalis” of the female. We support Lützen’s interpretation and we note that the spermatophores in Herpyllobius are discharged anteriorly through the frontal process of the bottle-shaped adult male. Males of Herpyllobius do not have posteriorly-located paired genital apertures.

There are currently 17 valid species of Herpyllobius ( Walter & Boxshall 2018) : H. antarcticus Vanhöffen, 1913 from Polyeunoa laevis McIntosh, 1885 (as Enipo rhombigera ) and Harmothoe fullo (Grube, 1878) (as H. gourdoni Gravier ); H. antepositus Stock, 1986 from Lagisca irritans Marenzeller, 1904 ; H. arcticus from Austrolaenilla mollis (Sars, 1872) , Gattyana cirrhosa (Pallas, 1766) , Harmothoe extenuata , H. imbricata Linnaeus, 1767 , and H. impar (Johnston, 1839) ; H. australis Lützen, 1964 from Harmothoe spinosa Kinberg, 1856 ; H. cordiformis from Eunoe nodosa (Sars, 1861) ; H. elongata Lützen, 1967 from Grubeopolynoe tuta (Grube, 1855) (as Holopidella tuta ); H. gravieri Lützen, 1964 from Harmothoe spinosa ; H. haddoni Lützen, 1964 from Harmothoe imbricata ; H. hartmanae Lützen & Jones, 1976 from Laetmonice producta Grube, 1876 ; H. lobosaccus Stock, 1986 from Lagisca irritans Marenzeller, 1904 ; H. luetzeni López-González & Bresciani, 2001 from Harmothoe cf. spinosa ; H. nipponicus Lützen, 1964 from Parahalosydna pleiolepis (Marenzeller, 1879) ; H. polasterni López-González, Bresciani & Conradi, 2000 from Eulagisca gigantea Monro, 1939 ; H. polynoes from Austrolaenilla mollis , Bylgides promamme (Malmgren, 1 867) (as Antinoe badia ), B. sarsi (Kinberg in Malmgren, 1866) (as Antinoe sarsi ), Eunoe nodosa , Gattyana amondseni (Malmgren, 1867) , G. cirrhosa , Gaudichaudius iphionelloides (Johnson, 1901) (as Gattyana iphionelloides ), Harmothoe antilopes McIntosh, 1876 , H. aspera (Hansen, 1878) , H. extenuata , H. imbricata , and H. impar ; H. rotundus Lützen & Jones, 1976 from Harmothoe sp.; H. stocki López-González, Bresciani & Conradi, 2000 from Austrolaenilla antarctica Bergström, 1916 ; and H. vanhoeffeni López-González & Bresciani, 2001 from Eulagisca corrientis McIntosh, 1885 . The great majority of these species are reported from high latitude waters ( Vanhöffen 1913; Lützen 1964a; López-González & Bresciani 2001; López-González et al. 2000, 2006) and all are recorded from polynoid hosts with the exception of H. hartmanae which utilises a polychaete host from the family Aphroditidae ( Lützen & Jones 1976) .