Tortanidae Sars, 1902

Francis, S V, Purushothaman, J, Siddique, A, Bhowal, A & Prasad, H, 2023, Taxonomic description of the male Tortanus (Atortus) murrayi Scott A., 1909 (Copepoda, Calanoida, Tortanidae) from the Great Nicobar Island, Indian Ocean, Indian Journal of Geo Marine Sciences 52 (6), pp. 307-311 : 308-309

Family: Tortanidae Sars, 1902

Genus: Tortanus Giesbrecht & Schmeil, 1898 Tortanus (Atortus) murrayi Scott A., 1909 ( Fig. 2 ) Material examined: Two adult males, one dissected (TL: 2.34 mm) and mounted on a glass slide and the other intact male preserved in a vial ( Fig. 2 ; TL: 2.26 mm)

Diagnosis: Pr around three times longer than Ur ( Fig. 3a ). Posterior edges of Pdg 5 produced into circular and symmetrical processes. Ur of 5 somites, genital somite without any lateral processes. CR symmetrical. Right A1 geniculate ( Fig. 3b, c ), 15-

segmented; ancestral segment I-VIII (segment 1), XXI-XXIII (segment 14) and XXIV-XXVIII (segment 15) totally or partially fused; segments XVI- XIX expanded. Armatures as stated: 1, (I-VIII) = 9+3ae; 2, (I) = 1; 3, (X) = 2+ae; 4, ( XI) = 0; 5, ( XII) = 0; 6, ( XIII) = 1; 7, ( XIV) = 1; 8, ( XV) = 0; 9, ( XVI) = 2+ae; 10, ( XVII) = 1; 11, ( XVIII) = 2+ae; 12, ( XIX) = 1+ae+P; 13, ( XX) = 1+P; 14, ( XXI-XXIII) = 2; 15, ( XXIV-XXVIII) = 1+7+ae. Segment XX anterior surface with a serrated ridge ( Fig. 3d ). Between segment XX and fused segments XXI-XXIII, a hinge junction is developed. Indent on anterior surface towards a proximal end of the latter segment. A lengthy spine-like process that spans nearly whole length of the fused segments XXIV-XXVIII located at the distal end. Antennule, antenna, mandible palp, mandible gnathobase, maxillule, maxilla and maxilliped (mouth appendages) similar to female specimens described from the South Andaman 9. First to fourth swimming legs exhibit similarities to those observed in recently described congeners from the Indian Ocean 9,14-16. Right P5 ( Fig. 3e ) CO swollen, irregular pentagon-shaped with large triangular

process; BA swollen, curves medially; small triangular process anteriorly; large, sharply pointed process emerges near inner proximal end; medial margin with three lamellae - proximal with three rounded processes; middle lamella triangular with rounded process proximally and seta at the base; distal lamella digitiform with rounded tip and subterminal seta. Claw-like Re; primary curve at 1/3 rd proximally; two finger-like processes on medioproximal margin; subdistal spinule on lateral margin; medial margin with subdistal triangular process short of distal end; segment terminates in a pointed tip; features one minute seta on mid-anterior. Left leg ( Fig. 3f ) CO devoid of processes; BA medial margin swollen near proximal and distal ends, one seta each near distal 1/3 rd of lateral and medial margins; Re-1 exhibits a digitiform process, terminal seta near proximal 1/3 rd of medial margin; Re-2 displays a rounded process on proximomedial margin with seta at its base, hirsute lateral margin, medial margin features lamellae at distal end and subterminal spine, apex possesses a long sinuate spine.

Figures

Fig. 2 — Tortanus (Atortus) murrayi Scott A., 1909, male dorsal view

Fig. 3 — Tortanus (Atortus) murrayi Scott A., 1909, male (a) habitus dorsal view; (b – d) antennule; (e) right leg anterior view; and (f) left leg 5 anterior view