Species Card of Copepod
Cyclopoida ( Order )
    Oncaeidae ( Family )
        Oncaea ( Genus )
Oncaea frosti  Heron, 2002   (F,M)
Syn.: Oncaea venusta; Ferrari, 1975 (p.225, fig.51); Boxshall, 1977 (p.124, fig.11a);
Oncaea venusta venella: Böttger-Schnack, 2001 (p.37, 45).
Heron, 2002 (p.148, figs.F,M); Böttger-Schnack & Huys, 2004 (p.2: Rem.); Elvers & al., 2006 (p.504, 511: Rem.); Böttger-Schnack & Schnack, 2013 (p. 7, Table 2: Rem.)
Species Oncaea frosti - Plate 1 of morphological figuresissued from : G.A. Heron in Hydrobiologia, 2002, 480. [p.146, Fig.1].
Female (coast of Liberia: a-b, habitus (dorsal and lateral, respectively; scale bar: u); c, anterior prosome (ventral; scale bar: v); d, right A1 (scale bar: w); e, right A2 (scale bar: x); f, labrum (ventral; scale bar: y); g, left Md (scale bar: y); h, left Mx1 (scale bar: y); i, right Mx2 (scale bar: y); j, left Mxp (scale bar: w).
The letter after the explanation of each figure (u-z) indicates the 0.05 mm scale at which the figure is shown.

Nota : Body ornamented with refractile granulations and prosome anteriorly with minute grooves. Genital segment length approximately equal to that of remainder of urosome ; gonopore on posterior of upper third of dorsal surface, each lateral area with a setule. Caudal ramus elongate, length variable but usually longer than total of 3 preceding segments, or approximately equal. A1 6-segmented with armature formula 3, 8, 4 + spinule, 3 + 1esthete, 2 + 1 esthete, 7 + 1 esthete. A2 3-segmented, 1st segment with distal inner spinulose seta ; 2nd segment with row of minute dentiform spinules along inner surface, outer rows of setules ; terminal segment with row of setules on posterior surface ; proximal inner surface with a curved spine and 3 setae ; distally 3 setae and 4 long, curved spiniform setae. Labrum posteriorly protuberant ; free margin divided into 2 rounded posteroventral lobes, each with row of dentiform setules inserted on under surface ; lobes separated by a semicircular vertex, from which a thin, hyaline lamella is suspended covered with hyaline, petaloid setules ; Two adjacent conspicuous sclerotized, spiniform protuberances anterior to vertex of labrum. Mx1 flat, bilobed ; 2setae and 1 robust spine on inner lobe ; 4 setae on outer lobe ; sclerotization on inner and outer margins. Mx2 2-segmented ; 1st segment with expanded base and sclerotized bands of support ; 2nd segment produced distally as elongate claw, with 2 inner rows of setules ; outer lateral seta ; 1 seta and 1 curved element with 2 rows of setules medially on proximal inner surface. Mxp 4-segmented ; 2nd segment robust with refractile granules on outer surface, inner surface with 2 spines ; anterior row of setules ; terminal segment consisting of long claw with row of setules on concave surface ; seta near inner base and small outer setule.

Species Oncaea frosti - Plate 2 of morphological figuresissued from : G.A. Heron in Hydrobiologia, 2002, 480. [p.147, Fig.2].
Female: a-d, P1 to P4 (scale bar: w); e, P5 (scale bar: z).
Nota : P5 a short free segment ; 2 terminal setae, distally very fine, the inner slightly longer ; seta on body near leg. P6 probably represented by spiriform setule on each external genital area.
Remark : The pediger 2 mid-dorsal dilatation obvious in lateral view, appears to circumscribe a gland-like organ ; a right and left duct originate from the gland, each directed to a small hooded dorsal pore. The gland does not preserve well in formalin, an dits shape and position varies slightly among specimens. Böttger-Schnack (2001) indicates an ‘’insignificant dorso-posterior swelling’’ on pediger 2 of the female of Oncaea venusta var. venella, also this form is considerd synonymous with O. frosti.

Male: f-g, habitus (dorsal and lateral, respectively; scale bar: v); h, 3rd segment of left A2 (scale bar: x); i, right Mxp (scale bar: w); i, right Mxp (scale bar: w); j, P5 (scale bar: w).
Nota : Body with refractile granulations more dense and conspicuous than for female ; scattered hooded pores. Urosome 1st segment with transverse sclerotized ridge dorsoposteriorly. Swimming legs as in female. P5 not delimited from thoracic segment ; lengths of setae similar to those of female ; seta on body near leg. P6 represented by posterolateral flap on ventral surface of genital segment.

Species Oncaea frosti - Plate 3 of morphological figuresissued from : G.A. Heron in Hydrobiologia, 2002, 480. [p.140, Fig.1].
The letter after the explanation of each figure (u-z) indicates the 0.05 mm scale at which the figure is shown.

Species Oncaea frosti - Plate 4 of morphological figuresissued from : G.A. Heron in Hydrobiologia, 2002, 480. [p.153, Fig.6].
Female pediger 2-4 and urosome (scale bar: v): a, Oncaea venusta; b, O. frosti; c, O. venella.

Nota: Exoskeleton with less dense cuticularization and slightly less conspicuous ornamentation than that of O. venusta. O. frosti displays a urosome flexed less often than that of O. venusta, but the two postgenital segments and anal segment are frequently telescopod; pediger 2 with conspicuous mid-dorsal dilation in lateral view; caudal ramus long, usually longer than sum of preceding three segments. Freshly collected specimens of O. frosti had bright red-orange shading on caudal rami and mouthparts.

NZ: 2

Distribution map of Oncaea frosti by geographical zones
Atlant. (coast of Liberia, G. of Mexico)
N: 1
(908) F: 0,95-1,15; M: 0,59-0,7; {F: 0,95-1,15; M: 0,59-0,70}
Rem.: This species distinguishes from O. venusta and O. venusta venella by its intermediate dimensions between these two forms. Without application of genetic analysis, it is difficult to define definitively between species (non-reproductive between each other) and simple population ecophenotypes mixed a posteriori.
After Böttger-Schnack & Schnack ( 2013, p. 7, Table 2) the species is insufficiently described.
Last update : 05/12/2016
    to add or edit your remark
By Ruth Böttger-Schnack 2013-11-25 11:12:02    ( Citation of this remark )
According to Böttger-Schnack & Huys (2004) the validity of Oncaea frosti Heron is doubted, because the morphological characters used to describe the species, an Atlantic medium-sized form variant of O. venusta, appear to be inadequate in view of the great morphology known for this ubiquitous species. Based on the detailed arguments given by Böttger-Schnack & Huys (2004), the species name is regarded as species inquirenda.

See also my comments on the taxonomic status of this species given in the database "World Register of Marine Species (WoRMS)".

 Any use of this site for a publication will be mentioned with the following reference :

Razouls C., Desreumaux N., Kouwenberg J. and de Bovée F., 2005-2024. - Biodiversity of Marine Planktonic Copepods (morphology, geographical distribution and biological data). Sorbonne University, CNRS. Available at http://copepodes.obs-banyuls.fr/en [Accessed April 18, 2024]

© copyright 2005-2024 Sorbonne University, CNRS

CNRS   Observatoire Océanologique de Banyuls sur Mer - Laboratoire Arago
Sorbonne Université


Version française
English version



On the WEB of CNRS


Marine Planktonic Copepods

Marine Planktonic Copepods


Imprimer Contact Accueil Plan du site Accès restreint Retour Une du Labo Imprimer Contact Plan du site Crédits Téléchargez les Plug-Ins