Crinoniscus cephalatus, Hosie, Andrew M., 2008

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 : 4-9

Crinoniscus cephalatus sp. nov.

( Figs 1 A, 2–4)

Material examined: All from Amigdoscalpellum costellatum . Holotype: 1ɗ 1.98 mm, ( NIWA 35048), stn F876, 3 Oct 1968, Bay of Plenty, 37°32.50'S, 177°34.00'E, 529 m, coll R.V. Taranui.

Paratypes: 1Ψ ( NIWA 35015), 1Ψ, ( NIWA 35017), from type locality. 1Ψ immature ( NIWA 35025), 2ɗ on SEM stub ( NIWA 43477), 1Ψ, immature, attached to host prosoma on SEM stub ( NIWA 43478) stn F870, 2 Oct 1968, North of East Cape, 37°25.50'S, 178°10.80'E, 263 m, coll. R.V. Taranui.1Ψ ( NIWA 35037), 1Ψ ( NIWA 35038) 1ɗ ( NIWA 35040), 1Ψ ( NIWA 35041), 1Ψ ( NIWA 35043), 1Ψ ( NIWA 35045), 1ɗ 1.73 mm ( NIWA 35049) 1ɗ 1.78 mm ( NIWA 35051), stn KAH0001/67, 19 Feb 2001, Bay of Plenty, 37°35.11'S, 177°31.33'E, 329 m, coll. R.V. Kaharoa. 2 ɗ 1.67–1.74 mm ( WAM C40020), stn TAN0705/155, 16 Apr 2007, eastern Chatham Rise, 42°59.93'S, 176°20.90'E, 648 m, coll. R.V. Tangaroa . 1Ψ ( NIWA 35019), 1Ψ ( NIWA 35023), stn KAH0001/68, 19 Feb 2000, Bay of Plenty, 37°27.19'S, 178°2.20'E, 242 m, coll. R.V. Kaharoa. 1Ψ ( NIWA 35029), stn KAH9801/39, 25 Jan 1998, Bay of Plenty, 36°57.75'S, 176°19.32'E, 535 m, 1Ψ, coll. Kaharoa.

Diagnosis: Male: Body hemispherical in lateral view, highest and broadest at pereonites 5 and 6; tapering sharply in posterior segments, with distinct cuticular striations, less prominent on cephalon. Anterior margin of cephalon evenly rounded with distinct rim. Posterolateral angles of cephalon projecting to pereonite 2. Eyes distinct. Antennule with prominent cuticular striations, especially on article 2; article 1 with rounded anterolateral angle. Article 3 anterior and posterior rami with 3 and 4 terminal setae respectively. Antenna reaching to pereonite 5 (setae excluded). Anterior coxal plates rounded, becoming pointed in posterior pairs. Pereopods 3–5 with triangular robust seta in notch on propodus distal margin, dactylus 0.55–0.60 propodus length. Pereopods 6 and 7 propodus rounded distally, without robust seta, dactylus approximately same length as propodus. Pleotelson wider than long, forming short, narrow, bluntly pointed, straight sided, posterior lobe. Uropod exopod approximately 0.5 length and 0.4 width of endopod. Exopod with 4 terminal setae, endopod with dense tuft of terminal setae.

Mature females anteriorly globose, tapering posteriorly into anal lobe. Cephalic limbs much reduced, mouthparts present at anterior end of ventral seam.

Description: Male (holotype): Body tear-drop shaped, total length 1.98 mm, widest at pereonite 6 (0.80 mm), anterior segments similar width posterior segments tapering sharply, cephalon length 0.27 mm width 0.81 mm. Cuticular striations distinct, but absent on cephalon and reduced dorsally on pereonites 1 and 2, Anterior margin of cephalon evenly rounded with distinct rim, posterolateral angles produced into flaps extending to pereonite 2.

Eyes ovate lateral, near junction with pereonite 1, lens tinted with pinkish pigment.

Antennule with cuticular striations on articles 1 and 2. Article 1 margins entire, cuticular striations present on anterior half and near posterior margin; mesial margin straight; abutting against opposite member, lateral margin concave, overlapping some of article 2, 3 setae present near posterior and anterior margins. Article 2 with 6 setae near lateral margin, approximately evenly distributed. Article 3 with bundle of aesthetascs dorsally and 1 seta near base of two uniarticulate rami; anterior and posterior rami with 3 and 4 terminal setae respectively, posterior ramus slightly longer than anterior ramus, 2 aesthetascs near midpoint.

Antenna reaching pereonite 5, peduncular articles with prominent striations. Setal formula: 0-1-3-5-2-1-2- 1-4. Articles, except basis, cylindrical, flagellar articles approximately half as wide as terminal peduncle article.

Pereopods 1 and 2 dactylus short, aquiline, approximately 0.4 propodus length, terminus opposing large teeth on propodus. Propodus large, egg-shaped tapering distally. Carpus triangular, tuft of fine setae at distal angle. Merus subtriangular, long distal seta originating from groove on inner face, single shorter seta present medially. Cuticular striations prominent on all articles, propodus with ctenae.

Pereopods 3–5 ambulatory, dactylus elongate, about 0.55–0.60 propodus length. Propodus distally quadrate and flattened, ventral margin somewhat concave, with triangular robust seta present in notch, 1 single short sharp seta present medially. Carpus and merus triangular, as in pereopods 1 and 2. Ischium with deep groove with subequal sides. Dactylus without cuticular striations, remaining articles as in pereopods 1 and 2.

Pereopods 6 and 7 with more slender articles than preceding pereopods, dactylus 0.85–0.90 and 0.90– 1.05 propodus length, respectively. Propodus tapering distally to rounded junction with dactylus, a single seta submedial and supramedial on pereopod 6 and 7, respectively. Merus, carpus, ischium and cuticular striations as in pereopods 3–5.

Coxal plates without posterior teeth, pereopods 1 and 2 rounded, remainder pointed, all with cuticular striations and lateral comb of short fine setae.

Pleopods becoming progressively smaller posteriorly. Pleopods 1–5 basis with 2 flattened, mesially directed trifurcate setae; distal margin forming submedially lobed lamella covering bases of rami. Exopod with 5 sparsely plumose setae; lateral seta approximately one-third length of others; exopod quadrate distally, tapering in basal half. Endopod ovate with 5 (3 in pleopod 5) sparsely plumose setae, and internal cuticular ring occupying basal two-thirds. All articles with prominent cuticular striations and ctenae.

Ventral abdominal lobe between first pair of pleopods apically rounded with medial notch.

Pleotelson twice as wide as long; posterior margin entire, forming blunt, narrow, nearly straight-sided lobe. Uropod basis quadrate, with 2 setae at posterolateral angle. Exopod cylindrical, 0.46–0.50 length and 0.39–0.43 width of endopod, with 4 terminal setae. Exopod triangular dorsoventrally flattened, 6 small setae present basally on dorsal surface, mesial margin with profuse comb of fine setae, terminally with dense tuft of fine setae.

Mature females segments fused, comma-shaped with long tapering posterior annulated anal lobe and a bulbous anterior section. Two small rounded lobes close together directly anterior to the remnants of the mouth parts; paired lobe-like maxillae, fused with labrum and possibly the mandibles which are rounded mounds. From the base of this structure the seam emerges and extends along ventral margin to the base of the annulated anal lobe.

Immature female segments fused and becoming globose, medially inflated. Pereopod 2 with dactylus and propodus as in males, but carpus, merus and ischium fused and extremely elongate forming ‘guy-lines’ up to as long as body. All other limbs absent. Eyes absent, pigment spots in ocular position, first and second antennae uniarticulate. Mandibles multifid.

Hosts: Amigdoscalpellum costellatum ( Withers, 1935) . Specimens of A. costellatum were attached to the spines of Goniocidaris sp. (Echinoida, Cidaridae ). Specimens of Paralepas minuta were also present in the samples but none were found to be infested with C. cephalatus .

Remarks: Crinoniscus cephalatus sp. nov. males can be distinguished from C. equitans by the absence of the anteriorly directed point on the anterolateral margin of antennule article 1, the projecting posterolateral angles of the cephalon; and the small, angular pleotelson posterior lobe. Crinoniscus cephalatus also possesses flat triangular setae on the distal margin of pereopod 3–5 propodus, whereas C. equitans has an acute seta. Females can be distinguished from the type species in having a globular anterior section without lobes, rather than the four-lobed ‘fleur de lis’ shape that characterises female C. equitans . Characters distinguishing C. cephalatus and C. politosummus are discussed below under the account of the latter.

Cephalic structures in mature females bear little resemblance to those present in the male form. The two small lobes near the mouthparts of C. cephalatus are possibly the remnants of the antennae, and the peculiar structure of the mature female mouthparts have probably rendered them non-functional.

Etymology: From the Greek kephalon, meaning head and the Latin alatus, meaning wing; named in reference to the wing-like projections on the cephalon.

Figures

FIGURE 1. Map of New Zealand showing localities of where the current specimens of A, Crinoniscus cephalatus sp. nov. (Ο), C. politosummus sp. nov. (Π); B, Scalpelloniscus nieli sp. nov. (Ο), S. cf. penicillatus Grygier, 1981 b () and S. vomicus sp. nov. (Π) were collected.