Abstract
The new species Crinoniscus stroembergi n. sp. belonging to the parasitic isopod family Crinoniscidae Bonnier, 1900, is described from a pedunculate barnacle host collected in the Mediterranean Sea. This is the first species of Crinoniscus Pérez, 1900 described from a host in the genus Heteralepas Pilsbry. The male cryptoniscus larva is distinguished from congeneric species by having a dorsoventrally flattened body with the posterolateral margins of the cephalon scarcely extending beyond the anterior margin of pereomere 1 (in contrast to C. cephalatus Hosie, 2008 with extended margins); articles 1 and 2 of the antennule being subequal in width and the anterodistal angle of antennule article being low and rounded; propodus of pereopods 6 and 7 having a sinuous dorsal margin that is distally narrowing and the posterior margin of the pleotelson being short and rounded. The mature females of species in Crinoniscus are of two basic forms: those with ventrolateral lobes on the pereomeres (C. alepadis (Gruvel, 1901) n. comb., and C. politosummus Hosie, 2008) and those lacking such lobes (C. cephalatus and C. stroembergi n. sp.). The mature females of C. stroembergi n. sp. can be distinguished from other species of Crininiscus based on their lacking lobes on the anterior end. The material examined includes the male and three female developmental stages of the parasite in the host, Heteralepas newmani Buhl-Mortensen & Mifsud. The mouthparts of the immature female are described and the feeding biology and effects on the host are discussed along with a review of feeding modes in species of the Cryptoniscoidea. Leponiscus alepadis is transferred to Crinoniscus; the latter genus now contains five species. A modified diagnosis of Crinoniscus is provided.
Highlights
Cryptoniscoidea Kossmann, 1880 contains nine families of endo- and ectoparasitic epicaridean isopod species associated with a diverse assemblage of crustacean hosts (Boyko et al, 2008 onwards); species in the genus Crinoniscus Perez, 1900 (Crinoniscidae Bonnier, 1900) specialise in parasitism of sessile and pedunculate thoracican barnacles (Hosie, 2008; Williams & Boyko, 2012)
In species of the Cryptoniscoidea, an adult female develops from a cryptoniscus larva with male characters that metamorphoses in response to contact with an appropriate host, but usually only if they are the first larva to encounter that host (Caullery & Mesnil, 1901; Caullery, 1952; Blower & Roughgarden, 1987)
The thorough description of the metamorphosis and feeding of C. equitans as reported by Bocquet-Vedrine & Bocquet (1972a, b) fits in most details with our observations on the morphology of the three female stages examined for C. stroembergi n. sp. (Fig. 3)
Summary
Cryptoniscoidea Kossmann, 1880 contains nine families of endo- and ectoparasitic epicaridean isopod species associated with a diverse assemblage of crustacean hosts (Boyko et al, 2008 onwards); species in the genus Crinoniscus Perez, 1900 (Crinoniscidae Bonnier, 1900) specialise in parasitism of sessile and pedunculate thoracican barnacles (Hosie, 2008; Williams & Boyko, 2012). Present knowledge on the development from the larva that encounters the host to the mature female stage is very limited for species in Crinoniscus, with the exception of studies by Bocquet-Vedrine & Bocquet (1972a, b) on C. equitans Perez, 1900 associated with its host, Perforatus perforatus (Bruguiere). Confirm the results of Bocquet-Vedrine & Bocquet (1972a) for C. equitans and show that female parasites in Crinoniscus are morphologically adapted to feeding on eggs and larvae of their host, and not directly on the host itself as is often the case for other epicarideans. We discuss the morphology of cryptoniscoid late immature female mouthparts and review the feeding biology in this group, one that has been largely overlooked as egg predators
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