Species Card of Copepod
Calanoida ( Order )
    Clausocalanoidea ( Superfamily )
        Aetideidae ( Family )
            Gaetanus ( Genus )
Gaetanus secundus  Esterly, 1911   (F,M)
Syn.: Gaetanus ferox : With, 1915 (p.111, figs.M); Grice & Hulsemann, 1967 (p.15, 23, figs.M); ? Vives, 1982 (p.291); Lozano Soldevilla & al., 1988 (p.58);
Gaetanus sp. Roe, 1972 (p.277, tabl.1, tabl.2);
Gaetanus miles : Park, 1975 a (p.19, figs.F,M)
Esterly, 1911 (p.317, Descr.F, figs.F, Rem. juv.M); Sewell, 1947 (p.57, 58); Davis, 1949 (p.29, Rem.F); Brodsky, 1950 (1967) (p.167, figs.F); Vervoort, 1963 b (p.131); Park, 1975 a (p.10); Markhaseva, 1996 (p.217, figs.F,M, Rem.: p.221); Vives & Shmeleva, 2007 (p.586, figs.F,M, Rem.)
Species Gaetanus secundus - Plate 1 of morphological figuresissued from : T. Park in Bull. Mar. Sci., 1975, 25 (1). [p.18, Fig.4]. As Gaetanus miles.
Female: A, B, habitus (lateral, dorsal); C, forehead (lateral); D, posterior part of metasome and urosome (dorsal); E, idem (lateral); F, Mxp; G, P1 (anterior); H, coxa of P4 (posterior).

Male: I, J, habitus (dorsal, lateral); K, L, forehead (dorsal, lateral).

Species Gaetanus secundus - Plate 2 of morphological figuresissued from : T. Park in Bull. Mar. Sci., 1975, 25 (1). [p.20, Fig.5]. As Gaetanus miles.
Male: A, posterior part of metasome and urosome (lateral view); B, last metasomal and genital segments (dorsal); C, A2; D, mandibular palp; E, Mx1; F, Mxp; G, P1 (anterior); H, P2 (anterior); I, P5 (posterior); J, last two exopodal segments of P5 (medial). P1, P2, P5: legs.

Species Gaetanus secundus - Plate 3 of morphological figuresissued from : G.D. Grice & K. Huisemann in Proc. U.S. natn. Mus., 1967, 122 (3583). [p.51, Figs.56-59]. As .
Male (from Indian Ocean): 56, 5th thoracic segment and urosome (dorsal); 57, forehead (lateral); 58, idem (ventral); 59, P5.

Species Gaetanus secundus - Plate 4 of morphological figuresissued from : C.O. Esterly in Univ. Calif. Publs Zool., 1911, 6 (14). [Pl.26, Fig.3].
Female (from San Diego Region): 3, habitus (lateral) (urosome incomplete).
Nota: Spine of the forehead is long and directed forward and slightly downward. A1 twice the length of the body. The length of the cephalothorax from the tip of the cephalic spine to the tip of the thoracic spine is over 5 times the length of the urosome.

Species Gaetanus secundus - Plate 5 of morphological figuresissued from : C.O. Esterly in Univ. Calif. Publs Zool., 1911, 6 (14). [Pl.28, Figs.38, 43].
Female: 38, part of last thoracic segment and urosome (lateral); 43, forehead (lateral).
Nota: Rostrum short and rounded. Spines on the sides of the last thoracic segment are long and extend beyond the middle of the genital segment.

Species Gaetanus secundus - Plate 6 of morphological figuresissued from : C.O. Esterly in Univ. Calif. Publs Zool., 1911, 6 (14). [Pl.30, Figs.73, 84].
Female: 73, 1st basal (= coxopodite) of P4 showing the row of spines; 84, 1st basal of posterior Mxp to show the lamella.

Species Gaetanus secundus - Plate 7 of morphological figuresIssued from : E.L. Markhaseva in Proc. Zool. Inst. RAN, 1996, 268. [p.222, Fig.176].
Female (from 11°13'N, 141°47'E). Ce = cephalon; CP4 = coxopodite of P4.

Nota: A1 twice longer than body ( nearly of the same length as in G. miles).
Cephalothorax about 5 times longer than urosome.
Frontal spine long and robust, directed forward, its top not curved or weakly curved to rostrm.
Endopod of P2 1-segmented, with traces of subdivision between segments.

Species Gaetanus secundus - Plate 8 of morphological figuresGaetanus secundus female:
1 - Anterior part of cephalon with frontal spine.
2 - Exopodal segment 1 of A2 without seta; exopodal segment 2 with 1 seta (near distal margin). 2nd internal lobe of Mx1 with 3 (?) setae. Exopod of P1 with 2 external spines.
3 - Mxp protopodite with lateral plate.
4 - Exopodal segment 2 of A2 with 1 seta.
5 - Spines of last thoracic segment exceeding at least the midlength of genital segment. Frontal spine large.
6 -, Frontal spine straight, not curved to rostrum by its top.
7 - Spines of last thoracic segment slightly reaching the midlength of genital segment. External spine of exopodal segment 2 of P1 exceeding the midlength of the next segment.

Species Gaetanus secundus - Plate 9 of morphological figuresGaetanus secundus male:
1 - Cephalon without frontal spine.
2 - Cephalon with crest in anterior part. Body size < 6 mm.

Compl. Ref.:
Hernandez-Trujillo, 1991 (1993) (tab.I); Yamaguchi & al., 2002 (p.1007, tab.1); Galbraith, 2009 (pers. comm.); Schnack-Schiel & al., 2010 (p.2064, Table 2: E Atlantic subtropical/tropical)
NZ: 8

Distribution map of Gaetanus secundus by geographical zones
SE Atlantic, Canary Is., Bay of Biscay, G. of Mexico, W Scotland, Vancouver Is., California, Izu-Bonin & Mariana Trench, Indian.

Type locality: NE Pacific (San Diego region)
N: 10
(7) M: 3,4; (37) F: 5,2-3,8; M: 3,55-3; (40) F: 4,24-3,72; M: 3,4-3; (59) F: 5,2; (143) F: 5,2; (199) M: 3,27-3,12; {F: 3,72-5,20; M: 3,00-3,55}
Rem.: Mesopelagic, bathypelagic. For Esterly (1911, p.318) this species resembles G. unicornis but is easily distinguished by the much greater length of A1 and the character of the spines on the basals of P4.
Certain locality records are doubtful because of Markhaseva's (1996) suspicion on the synonymy of this species with Gaetanus miles.
Last update : 05/01/2015
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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 May 25, 2024]

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