Crinoniscidae Bonnier, 1900

Hosie, Andrew M., 2008, Four new species and a new record of Cryptoniscoidea (Crustacea: Isopoda: Hemioniscidae and Crinoniscidae) parasitising stalked barnacles from New Zealand, Zootaxa 1795, pp. 1-28 : 3

Family Crinoniscidae Bonnier, 1900

Composition: Crinoniscus Perez, 1900 ; Proteolepas Darwin, 1854 .

Diagnosis: Male body tear-drop shaped, approximately 2.5 times longer than wide. Cuticular striations, variably pronounced. Cephalon wider than long. Oral cone anteriorly directed. Eyes forming hyaline lens. Antennule article 1, coxal plates and pleotelson without posterior teeth. Antenna arising from beneath posterior margin of antennule, flagellar articles of similar length. Propodus of pereopods 3–5 quadrate with broad stout seta in notch on distal margin, dactylus 0.5–0.7 propodus length. Dactylus of pereopods 6 and 7 approximately as long as propodus. Pleopod rami in line with each other; endopod with internal cuticular ring present basally. Pleotelson posterior margin entire, posterior lobe width not exceeding 0.5 posterior margin. Uropod exopod 0.35–0.50 as long as exopod and 0.30–0.45 as wide. Anal tube absent.

Immature female segments fused, lacking limbs except for uniarticulated antennae, mouthparts and modified pereopod 2. Mature female fusiform or anteriorly globose, posteriorly annulated, cephalic limbs further reduced or absent, pereopod 2 absent.

Remarks: The Crinoniscidae is so far only known to parasitise sessile and pedunculate barnacles. Male crinoniscids are distinguished from those of Hemioniscidae by less prominent cuticular striations, the absence of posterior teeth on the antennule and the small exopod of the uropods. During gender transition crinoniscids lose all traces of the male form, including limbs, eyes, mouthparts and segmentation, whereas hemioniscids, the first 3 anterior segments, at least, remain differentiated. The families Cryptoniscidae Kossman, 1880 (= Liriopsidae Bonnier, 1900 ) and Asconiscidae Bonnier, 1900 also lack teeth on the antennule article 1, coxal plates and pleotelson. The males of the former possess a long styliform dactylus and very short propodus on pereopods 6 and 7. Female Cryptoniscidae also lose all trace of the male morphology; instead the body is divided into two sections connected by a narrow neck, the anterior section embedded into the host while the posterior remains exposed ( Altes 1981; Caullery 1908; Peresan & Roccatagliata 2005; Sars 1899). The sole species of Asconiscidae , Asconiscus simplex Sars, 1899 , has relatively large exopods on the uropods and heavy sculpturing on antennule article two, forming four posteriorly directed teeth; the anterior margin of the antennule is straight and perpendicular to a long straight mesial margin which abuts onto its opposite member. In contrast, antennule article 1 in crinoniscids the anterior and mesial margins are more rounded. Asconiscid females still retain the empty exuviae of the male, with which it remains attached to the host ( Sars 1899).

Bocquet-Vedrine (1985, 1987) considered Crinoniscidae to be a subfamily within the Cryptoniscidae , citing the similarities between the antennule and between the epicaridium larvae. However, because the two proposed subfamilies Cryptoniscinae and Crinoniscinae can be readily distinguished in both the larval and adult stages, I have followed Bonnier’s (1900) arrangement of the Cryptoniscoidea , with the nomenclatural corrections made by Grygier & Bowman (1991) and kept the Crinoniscidae separate from the Cryptoniscidae . The family contains two genera – Crinoniscus Perez, 1900 and Proteolepas Darwin, 1854 , but a third genus, Leponiscus Giard, 1887 , was proposed to belong within the family by Bocquet-Vedrine & Bocquet (1972) on the basis of L. alepadis Gruvel, 1902 . However, the type species, L. anatifae (Hesse, 1867) (and original placement) for this genus is currently placed within Hemioniscidae (see remarks for Hemioniscidae below). The sole species of Proteolepas , P. b i v i n c t a Darwin, 1854, was mistakenly described as a cirripede based on a single (immature?) female specimen parasitising Paralepas cornuta ( Darwin, 1851) collected from St Vincent, Caribbean Sea. Bocquet-Vedrine (1972) transferred the species to the Crinoniscidae based on the similarities with immature female C. equitans . It is presently impossible to assess the identity and position of Proteolepas without knowledge of mature females or males. Presently Proteolepas bivincta is species inquirendum. If P. bivincta and C. equitans proved to be congeneric, then Proteolepas would have priority.