Tortanus (Atortus) tropicus     (Copepod)
Organism information awaits expert curation
Class: Maxillopoda

Size (female): length 2.71 mm; (male): 2.289 mm

Female: The proportional lengths of the cephalothorax and abdomen are as 93 to 29, so that the abdomen is contained 3.172 times in the length of the anterior region of the body.
The forehead is produced towards in a rounded prominence. The head and 1st thoracic segment are separate, but thoracic segments 4 and 5 are fused together. When viewed from the side a well-marked groove can be seen to pass across the dorsal neck region. The posterior thoracic margins are rounded and devoid of any spines, that on the right side being produced backwards in a wing-like process.
The abdomen consists of only two segments; segments 1-4 being fused together. Segment 5 is fused with the furcal rami. The genital opening forms a well-marked rounded prominence on the ventral aspect of the anterior abdominal segment. The furcal rami are somewhat asymmetrical, that on the left being distinctly stouter at its base than that on the right. Of the five furcal setae the 2nd is considerably stouter than the others and about twice the length. The outer seta arises from the external margin about two-thirds from the base.
The 1st antenna reaches back to about the middle of the furcal ramus.
In the maxilliped, there are only two long setae present in the 1st segment
The terminal segment of the endopod of the 2nd , 3rd and 4th legs bears only six setae.
The 5th pair of legs are asymmetrical, the appendage of the left side being considerably larger than that of the right. Each consists of a basal segment and a single long free segment or exopod; about half-way along the outer margin of this segment there is a sharp constriction, the distal part from this point on being narrower than the proximal part. Each segment is capped by a long spine and at the extremity of the free segment of the left leg there is an additional small triangular spinous process.
Male: The proportional lengths of the cephalothorax and abdomen are as 72 to 31, so that the abdomen is contained 2.326 times in the length of the anterior region.
The cephalothorax closely resembles that of the female.
The abdomen is composed of 4 segments with the furcal rami.
The posterior thoracic margins are rounded and symmetrical. The 2nd abdominal segment bears on its right side a posteriorly- directed spinous process. The furcal rami are elongated by symmetrical; they are considerably broader at their distal extremities than at the base. The furcal setae are all uniform thickness.
The 1st antenna on the right side is, as is usual, modified to form a grasping organ, while that on the left resembles that of the female.
In the grasping antenna segments 14-17 are somewhat swollen and segments 15 and 17 each bear a stout spinous process on their anterior margins, that on segment 17 being situated at the proximal end of the joint. Segment 18 bears a very elongated tooth-plate, that is extended proximally along nearly the whole length of segment 17 and comes into close relationship at its extremity with the spinous process on that segment. Segment 19-2 1 bears two tooth plates that are, however, devoid of any denticulations; the distal tooth-plate is prolonged for a considerable distance beyond the distal extremity of the segment. The terminal three segments 22-25 are fused together.
The 2nd antennae, mouth-parts and swimming-legs appear to resemble those of the female.
In the 5th pair of legs, on the left side basal 2 is a short and almost cylindrical segment and is succeeded by a three-jointed ramus of which the 1st segment is considerably longer than either the second or third; a stout seta arises from its inner aspect near the proximal end. The 2nd segment is produced near its base into a long and curved process that is nearly half the length of the segment itself. The 3rd or distal segment is curved and bears at its tip a row of small curved spines; on the proximal side of this row arises a single small seta. On the right side the 2nd basal segment appears to be fused with basal 1. The free ramus consists of only two segments, segment 2 and 3 being fused together. The 1st segment is considerably thickened and bears on its inner aspect a rounded lobe; segments 2 and 3 together form a curved tapering process.

Synonym (s)

Common Name (s)
Economic Importance and Threats



Literature Source(s)
  • Sewell, RBS (1999) The copepoda of Indian seas Biotech Books, Delhi, India 407 pp Available at - NIO, Goa
  • Society for the Management of European Biodiversity Data (2009) World Register of Marine Species (WoRMS) Available at -

Page last updated on:2009-08-13

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