Species Card of Copepod
Calanoida ( Order )
    Diaptomoidea ( Superfamily )
        Tortanidae ( Family )
            Tortanus ( Genus )
                Atortus ( Sub-Genus )
Tortanus (Atortus) sigmoides  Nishida, Anandavelu & Padmavati, 2015   (M)
Nishida & al., 2015 (p.225, Descr.M, figs.M, Rem.); Francis & Bijoy Nandan, 2019 (p.434, Table 5).
Species Tortanus (Atortus) sigmoides - Plate 1 of morphological figuresIssued from : S. Nishida, I. Anandavelu & G. Padmavati in Crustaceana, 2015, 88 (2). [p.226, Fig.5] .
Male (from 11°33'N, 92°43'E): A-B, habitus (dorsal and lateral, respectively); C, 1st abdominal somite (right lateral); D, E, A1 (segments XIX and XX are indicated by star); F, P5 (posterior view); G, right P5 (anterior view); H, left P5 (anterior view).
Abbreviations: Cox, coxa; Bas, basis; Exp, exopod; Exp1, 1st exopodal segment.

Nota: Prosome about 2.5 times as long as urosome
- Posterior corners of 5th pediger rounded and asymmetrical with left side more produced posteriorly than right.
- Urosome 5-segmented; proportional lengths of urosomites and caudal ramus 15 : 16 : 14 : 8 : 32.
- 1st abdominal somite with posterolateral and posteroventral processes on right side, of which latter smaller, each with minute seta on tip, and tip of former reaching about middle of 2nd somite in both dorsal and lateral view.
- Caudal rami symmetrical.
Appendage similar to those of male Tortanus andamanensis except features in right A1 and P5.
- Right A1: anteroproximal process on segment XIX triangular, reaching middle of segment; serrated ridge on segment XX curved sigmoid and produced proximally to middle of segment XIX, close to tip of triangular process; anterodistal seta on segment XX also curved sigmoid.

Species Tortanus (Atortus) sigmoides - Plate 2 of morphological figuresIssued from : S.V. Francis & S. Bijoy Nandan in Turkish J. Zool., 2019, 43. [p.435, Table 5].
Differential diagnosis of T. sigmoides male. Compare with other species of the subgenus Atortus species from the Indian Ocean.

Morphological characters male:
- Left P5 with subdistal short seta. Right P5 coxa semicircular with small bilobed medial process, basis semicircular with fingerlike medial process.

NZ: 1

Distribution map of Tortanus (Atortus) sigmoides by geographical zones
NE Indian (South Andaman Island, Burmanallah).

Type locality: 11°33' N, 92°43' E.
N: 1
(1180) M: 1,96-2,08; {M: 1,96-2,08}
Rem.: For Nishida & al. (2015, p.227, 228) this species is assignable to the tropicus species-group, but T. sigmoides is distinguished from the other members of the tropicus group by the serrate ridge and the anterodistal seta on segment XX of the right A1, both of which are strongly curved sigmoid; these characteristics are autoapomorphies in the tropicus group.
The males of T. sigmoides closely resembles those of the longipes group (T. longipes and T. giesbrechti) defined by Ohtsuka & Kimoto (1989), especially in the posterior process of prosome with left end produced more posteriorly than right, the triangular anteroproximal process on the segment XIX of right A1, the expanded basis of right P5, and the prominent medial triangular process on the basis of left P5
Last update : 11/02/2020
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Razouls C., Desreumaux N., Kouwenberg J. and de Bovée F., 2005-2022. - Biodiversity of Marine Planktonic Copepods (morphology, geographical distribution and biological data). Sorbonne University, CNRS. Available at http://copepodes.obs-banyuls.fr/en [Accessed September 27, 2022]

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