Metridia princeps   Giesbrecht,  1889 (Copepod)
Organism information awaits expert curation
Class: Maxillopoda

Image copyrights: Biotech Books

A. Dorsal view

Size (male): Length 7.4 mm.
Size (female): Average length 7.75 mm.

Female: The proportional lengths of the cephalothorax and abdomen are as 24 to 19, so that the abdomen is contained only 1.26 times in the length of the cephalothorax. The head terminates anteriorly in a plumose bifid rostrum. Thoracic segments 4 and 5 are fused together and the posterior thoracic margin is not produced backwards. The abdomen consists of three segments with furcal rami. The anal segment on each side is produced outwards and backwards in a rounded prominence that overlaps the base of the furcal ramus. The furcal rami are only a little more than twice the length of the anal segment and are 4.9 times as long as broad. Each ramus bears a single seta on its external border and four setae distally; there is also a fine delicate accessory seta on the dorsal aspect. The whole of the inner border, and the proximal part of the outer margin, as far as the point of origin of the external seta is fringed with hairs.

The 1st antenna consists of 25 segments, of which the 7th, 8th and 9th are fused, as well as the 24th and 25th. Combined joint of segment 1 and 2 bears three marginal spines. The 2nd segment bears a single spine and the 3rd is devoid of any such projection. Segments 4, 5 and 6 each bear a small stout spine.

The 1st swimming leg consists of the usual basal part and three-jointed exopod and endopod. In the basal portion the 1st segment bears a single inner seta but has no marginal spine; basal 2 bears a delicate spine having a serrated inner border, an inner S-shaped seta and also a tuft of hairs distally on its curved inner margin. In the exopod the 1st segment carries a long and slender marginal spine, that is fringed with hairs on its inner side, and a single internal seta; the inner border of the segment is fringed with long hairs and a row of minute spines runs horizontally across the outer half of the distal margin. Exopod 2 bears a single internal seta and the proximal part of the inner margin is fringed with fine hair; externally it bears a delicate marginal marginal spine and the outer border is finely serrated and is fringed with hair; a row small spines runs across the surface transversely near the distal border. Exopod 3 carries two slender marginal spines and the outer border is serrated; the terminal spine is long and slender and is fringed with hair internally; the inner margin bears four setae. The proportional lengths of the distal two segments of the exopod and the terminal spine are as 19; 27; 54. The 1st segment of the endopod bears a single inner seta; the outer margin is fringed with hair and a row of needle-like spines runs across the anterior aspect. Endopod 2 bears two inner setae and endopod 3 carries five.

In the 2nd swimming leg basal 1 bears a single inner seta; basal 2 bears a scattered group of small spines on its external surface and is produced internally in a rounded prominence. Both exopod and endopod consist of three segments. Exopod 1 bears a marginal spine that is short and leaf-like; the inner margin is fringed with hairs on its distal three-fourths and carries a single seta, a group of small spines is present near the base. In exopod 2 the outer border is produced as a thin chitinous lamella that is fringed with hair; the marginal spine is leaf-like; internally there is a single seta and the proximal part of the margin is fringed with hair; exopod 3 bears three marginal spines and the outer margin is thin and lamellar; the terminal spine is broad and is finely serrated on its outer margin; there are five inner setae. The proximal segment of the endopod, bears the characteristic double recurved hook on its inner border and there is another hook-like spine, directed externally near the base; in this species the two distal hooks are of nearly equal size. Endopod 2 bears two inner setae and the outer margin of the segment is fringed with hair. Endopod 3 carries eight setae and the proximal part of the outer margin is fringed with hair.

In the 3rd and 4th swimming legs the 1st basal segment bears a plumose seta on its inner margin, and basal 2 is devoid of spines and setae. Exopod 1 bears a single leaf-shaped marginal spine and the inner margin is fringed with hairs. Exopod 2 is very similar to exopod 1. Exopod 3 exhibits certain differences in the teo legs; in the 3rd swimming leg there are three leaf-like marginal spines the terminal spine is finely serrated and five setae arise from the inner margin; in the 4th leg this segment is similar but there are slight differences in the relative lengths of the terminal spines and the end segment; in the 3rd leg the proportions of the segment and spine are as 3.74 to 1, whereas in the 4th leg they are as 4.35 to 1. In both legs the endopod reaches as far as the level of the joint between segments 2 and 3 of the exopod; endopod 1 bears a single seta and endopod 2 bears a couple; in the 3rd leg endopod 3 bears seven setae, whereas in leg 4 it carries eight. In both legs the outer margin of the two proximal segments is fringed with hair.

The 5th leg consists of a basal part and three free segments that have the proportional lengths of 13, 27, 32. The basal segment bears posteriorly a tuft of long hairs; the 1st free segment carries a long seta and the 2nd bears a small marginal spine; the distalsegment bears three setae, of which the inner is the longest.

Male: The proportional lengths of the cephalothorax and abdomen are as 23 to 18, so that the abdomen is contained 1.27 times in the length of the anterior region of the body. Segments 4 and 5 of the thorax are fused.
The abdomen consists of five segments with the furca
In males the furcal rami are but little more than twice as long as the anal segment.

The 1st antennae are asymmetrical; that on the left side being modified to form a grasping organ. In this latter case segments 1 and 2 are fused completely. Segments 7, 8 and 9 are partially fusedand segments 19-21 are fused. The knee-joint occurs between segments 18 and 19 as usual.
The combined segments 1 and 2 carries a series of spinous projections onits anterior aspect; the spine arising from that part that corresponds to segment 2 being by far the largest. Segment 3 bears no spine; but segments 4, 5 and 6 each bear a spine. Segment 17 bears a spine that extends along the anterior margin and overlaps the base of segment 18. Segment 18 bears a tooth-plate on its anterior border; this plate is about equal in length to the whole segment and is armed with about 20 claw-like teeth of unequal size, while the distal free end of the plate is bent upwards. Segment 19 bears two plates on its proximal half, each terminating in a free, spine-like projection.

Synonym (s)
Metridia princeps Wolfenden, 1908
Metridia princeps A. Scott, 1909
Metridia princeps Sewell, 1913
Metridia princeps Lysholm and Nordgaard, 1921
Metridia princeps Sars, 1925
Metridia princeps Farran, 1926
Metridia princeps Farran, 1929
Metridia atra Esterly, 1906

Common Name (s)
Economic Importance and Threats



• Bay of Bengal INDIA (Record: 21/10/1911)
• INDIA (Record: 21/04/1912)
• INDIA (Record: 23/04/1924)
• INDIA (Record: 23-04-1924)
• Kerala, Off Kochi (Lat: 10) (Long: 68.05) INDIA (Record: 14/11/1983-17/11/1983)
• Kerala, Off Kochi (Lat: 11.5) (Long: 73.11) INDIA (Record: 14/11/1983-17/11/1983)

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 -
  • Fernandes, V (2008) The effect of semi-permanent eddies on the distribution of mesozooplankton in the central Bay of Bengal Journal of Marine Research Sears Foundation for Marine Research 66 465–488 Available at - NIO,Goa
  • Madhupratap, M and Haridas, P (1990) Zooplankton, especially calanoid copepods, in the upper 1000m of the south-east Arabian Sea Journal of Plankton Research Oxford University Press 12 305-321 Available at -

Page last updated on:2011-03-15

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