Scottocalanus thomasi   Scott A,  1909 (Copepod)
Organism information awaits expert curation
Class: Maxillopoda

Female: The genital segment of the abdomen bears a finger-like, backwardly directed projection near the posterior margin a little to the left of the middle line.

The 1st antenna reaches beyond the tip of the furcal ramus by the last two segments.

In the 2nd antenna, the 1st basal segment bears a row of curved setae. The endopod is about one-half the length of the exopod. The exopod consists of 6 segments; of these. The 1st has a rounded swelling on its inner border; the 2nd bears two unequal setae distally; the 3rd -5th inclusive each bear a single long seta; the 6th segment bears one seta at about one-fourth of its length and 3 long setae distally.In the mandible the palp is well developed. Basal 1 bears a stout seta proximally and a second about half way along its length. The endopod consists of two segments; the 1st bears two setae on its inner border; the 2nd has 9 setae distally and is armed with curved spines on its outer margin. The exopod consists of 5 segments, of which the proximal four bear a single long seta and the terminal segment carries two unequal setae.

In the 1st maxilla the 2nd inner lobe bears 2 setae and the 3rd three. The 2nd basal segment carries 5 setae and is fringed with hair along the inner margin. The three segments of the endopod bear respectively 3, 4 and 4 setae and the exopod has 8. The outer lobe appears to have 9 setae.In the 2nd maxilla the 1st lobe bears 4 setae; the 2nd, 3rd and 4th each bear 3 setae and the 5th lobe bears 3 setae, of which one is very thick and stout. The terminal portion of the appendage carries, as in other members of the genus, two kinds of filaments, one kind being long and simple and the other shorter and swollen at the distal end.

In the maxilliped the 1st basal segment bears a sensory seta about the middle of its length; at its distal end it bears three setae, of which the most distal is thickened and spine like. The distal part of basal 1 and the whole length of basal 2 is armed with spinules. Basal 2 bears 2 setae about the middle of its length and 2 others distally. The endopod consists of the usual 5 segments, of which the 2nd is much the longest; segment 1 and 2 each bear 4 setae, segments 3 and 4 bear 4 and the terminal segment bears 4 setae on its inner and distal aspects and a 5th on its outer aspect.

The 1st swimming leg consists of the usual two-jointed basal portion and an inner and outer ramus, of which the outer consists of three segments, while the inner is unjointed. The 1st segment of the exopod bears no seta on its inner margin but the inner border is produced in a rounded swelling which is fringed with hair; the outer border bears distally a single marginal spine, which reaches about two-thirds the distance to the base of the spine on segment 2. In the 2nd segment the marginal spine arises from a distally –directed finger like projection and extends nearly to the base of the marginal spine on segment 3; the inner border bears a single seta-like end-spine; three setae arise from the inner margin. The outer margin of the terminal segment is fringed with hair inits proximal half. The endopod consists of a single joint, bearing 5 setae; the outer margin is produced in a rounded lobe that is armed with needle-like spinules.

In the 2nd leg the 1st basal segment bears a minute spine-like projection on its outer border; the inner margin is fringed with hair and bears a single seta. Basal 2 is produced in a sharp spine at its distal outer angle. The exopod consists of three segments and the endopod of two. The exopod bears 1, 1 and 3 marginal spines on the three segments respectively and the terminal segment also carries an end-spine; all the marginal spines are subequal. In the 2nd segment of the exopod there is horse-shoe of small spines, the two longitudinal rows consisting of somewhat larger spines than the transverse row across the distal part of the segment. The 3rd segment bears 4 inner setae and the surface is armed with two horse-shoe or U-shaped rows of spinules, those of the proximal set being much larger than the distal. The 1st segment of the endopod is produced in a spine-like projection at its distal outer angle and bears a single seta; the 2nd segment bears 5 setae and carries on its surface three pairs of spines, those of the inner row decreasing in size proximally.

In the 3rd leg the 1st segment of the basal part bears a minute marginal spine on its outer border and the inner margin is curved and fringed with hair; there is a single inner seta. The 2nd basal segment bears two unequal spines at its distal outer angle. Both the rami consist of three segments, bearing 1, 1 and 3 marginal spines respectively. Exopod 2 bears a curved row of spines along its distal border. Exopod 3, in addition to the three marginal spines, carries an end-spine, in which some of the teeth near the proximal end are reduced in size; the marginal spine exhibits a corresponding swelling on its inner margin. The surface of the segment bears two curved row of spinules, the distal row being composed of small spines. In the endopod both the 1st and 2nd segments are produced in a spine-like projection at the distal outer angle; endopod 2 bears 2 pairs of spines, the outer spines being much the larger and the inner spine of the proximal pair being reduced to a minute spicule. Endopod 3 bears 5 setae and carries 2 pairs of spines, the outer of the proximal pair being much the larger.

In the 4th leg the 1st basal segment is not produced internally and the inner margin is smooth; there is no small spine on the outer margin. Basal 2 bears two unequal spines at its distal outer angle as in the 3rd leg. The rami consist each of three segments. The surface of segments 2 and 3 in the exopod are devoid of spinules. In the endopod the 2nd segment bears a small group of needle-like spines distally and the 3rd segment bears two groups of small spinules.

The 5th leg consist of a single segment, bearing a long curved spine. The distal end of the segment is produced in a finger-like process. The spine is smooth and bare in its proximal third; then for a short distance it is armed with spinules are arranged in two rows, an inner and an outer. The inner row ceases some little way from the end but those of the outer row are considerably increased in size. These enlarged spinules give rise to the appearance of a V-shaped end to the spine.

Male: The endopod of the 2nd antenna is a little more than one-half the length of the exopod; otherwise the appendage resembles that of the female. In the mouth-parts the mandible, 1st maxilla and 2nd maxilla are as in the female; in the maxilliped the outer setae of the 4th and 5th segments of the endopod are much larger and are strongly plumose. The swimming legs are as in the female.

Synonym (s)
Scottocalanus thomasi A. Scott, 1909

Common Name (s)
Economic Importance and Threats



• INDIA (Record: 23/04/1924)

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:2010-07-19

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