Cereudorsum, Harris, 2014

Harris, Vernon A., 2014, Porcellidiidae of Australia (Harpacticoida, Copepoda). III. Synopsis of Genera and Species, Records of the Australian Museum 66 (2), pp. 167-196 : 168

Genus Cereudorsum gen. nov.

Type species. Cereudorsum verrucosum sp. nov.

Diagnosis. Dorsal organs present (trough-like depressions in cuticle), surrounded by massive honeycomb-like cuticle ( Figs 1A , 4F ); male antennule unique, no denticle on segment 3, segment 4 with group of four or five swollen finger-like structures in place of typical cuticular denticles; maxilliped coxal lobes wide apart; no ridge plates on labrum; male and female caudal ramus rectangular, T1 small pinnate, deeply recessed, setae T2, T3 and T4 large pinnate, equally spaced (not pinnately clavate); maxillule with six setae on endopod; male P5 trapezoid, no reduction in number of terminal setae; spermatophore elongate, ephemeral on female.

Species composition. Only the type species is known, Cereudorsum verrucosum sp. nov. Recorded from Sydney, NSW, Australia .

Etymology. Cereudorsum , (L. cereus = waxen, honeycomb + dorsum = the back).

Remarks. Dorsal organs surrounded by massive honeycomb-like growth of cuticle are not known elsewhere in the Porcellidiidae ; their presence is considered an autapomorphic character that defines the genus.

SuperficiallY, the large pinnate terminal setae (T2–T4) on the caudal rami resemble the pinnately clavate setae of Clavigofera but in the latter genus the pinnae arise from a flattened expansion of the seta shaft, not the shaft itself ( Fig. 12R ), and T1 is the same size and shape as T2–T4.

The maxillipeds of Cereudorsum resemble those of Dilatatiocauda , which do not meet in the midline or possess a fimbriate process, but the basis is elongated tYpical of other Porcellidiidae .

Figures

Figure 1. Cereudorsum verrucosum sp. nov. Female: (A) adult; (C, E) genital double-somite (E detail of posterior lobe); (D, F) caudal rami (D detail of terminal setae). Male: (B) adult. Scale bar:A, B = 0.5 mm. C = 0.03 mm. D = 0.08 mm. F = 0.14 mm.

Figure 4. Cereudorsum verrucosum sp. nov. (A) P5 and caudal ramus of pharate stage V female copepodid, showing difference in type of setae between adult and juvenile; (B) stage V female copepodid; (C) lateral view of adult male; (D) border of male cephalosome, note absence of micro-tubules (hy.m. hyaline membrane; hy.so. hyaline sense organ; mg.d. duct of marginal gland; mg.o. opening of marginal duct); (E) border of female cephalosome (left superficial focus showing micro-tubules, right deep focus showing branched ducts of marginal glands, lettering as for D; d.pits, dorsal pits); (F) dorsal organs and cuticular honeycomb of stage V copepodid (dorsal view). Scale bar:A, F = 0.14 mm. B = 0.55 mm. C = 0.35 mm. D, E = 0.08 mm. F = 0.14 mm.

Figure 12. TYpes of female left caudal ramus and terminal setae found in the Porcellidiidae (α and β seta not shown).(A, B) Porcelloides.(C) Kensakia.(D) Clavigofera.(E, F) Porcellidium, Tectacingulum, Murramia and Dilatatiocauda. (G) Kushia. (H) Brevifrons and Cereudorsum.(I) Mucrorostrum, Geddesiaand Clunia. (J) Synurus.(K, L) Ravania.(M, N, O) Acutiramus. (P) Kushia, female right P5 ventral view (VE, ventral expansion;FR, falciform ridge).(Q) Kensakia, male antennule (ventral view; Br P, Brush-pad). (R) Clavigofera, pinnate clavate terminal seta from caudal ramus.