Metridia macrura   Sars G.O,  1905 (Copepod)
Organism information awaits expert curation
Taxonomy
Kingdom:Animalia
Phylum:Arthropoda
Class: Maxillopoda
Order:Calanoida
Family:Metridinidae

Description
Size (male): length 8.9 mm.
Size (female): length 7.78-9.11 mm.

Female: The proportional lengths of the cephalothorax and abdomen are as 1.17 to 1.

The head terminates anteriorly in a bifid rostrum, bearing a pair of rostral spines that are slender and plumose. Thoracic segments 4 and 5 are fused and the posterior thoracic margin is rounded. The abdomen consists of three segments and the furcal rami.

The genital segment is moderately swollen ventrally. Segments 4 and 5 each bear a tuft of long hair on the anterior part of the ventral aspect. The anal segment is somewhat produced laterally in a rounded lobe. The furcal rami are slightly asymmetrical, that of the right side being a trifle longer than that of the left. The furcal rami are six times as long as broad and are 2.6 times the length of the anal segment. The rami are fringed with fine hair throughout the whole length of the inner border and there is a row of hairs on the proximal part of the outer border.

The 1st antenna over-reaches the posterior end of the abdomen by about the last three or four segments. Segments 7, 8 and 9 are fused together and in some specimens segment 10 appears to be partly fused to segment 9; segments 12 and 13 are partly fused and segments 24 and 25 completely so.

The anterior margin of sgment 1 carries three short spines; segment 2 bears a single larger spine; segment three is devoid of a spine and segments 4, 5 and 6 each bear a single spine.

In the 2nd antenna the endopod and exopod are of equal length. The 1st maxilla possesses the usual structure. The basal segment bears 5 setae; the 2nd inner lobe possesses 5 and the 3rd lobe 4; in the endopod the 1st segment carries 6 setae, and the 2nd and 3rd 5 each; the outer lobe has 8 setae and the exopod bears 11.

In the maxilliped, on the 1st basal segment there is a group of fine spines at the distal anterior angle; basal 2 bears three setae on its anterior margin and 2 distally; a row of needle-like spine runs along the anterior margin as far as the 2nd lobe. The endopod consists of 5 segments, bearing respectively 4, 4, 4, 3 and 4 setae.

The endopod reaches only just to the joint between the segments 2 and 3. The proportional lengths of the terminal spine to the combined length of the last two segments of the exopod are as 48 to 36, and as 48 to 31 to the 3rd segment. Both the 2nd segment and the proximal part of the 3rd segment of the exopod are fringed with fine hairs.

The 5th pair of legs are composed of a basal part and three free segments; the proportional lengths of these segments are as 15, 11 and 5. The proximal segment bears a well developed marginal seta; the 2nd segment carries a small marginal seta distally and the terminal segment bears three setae of nearly equal length. The basal segment carries a tuft of long hairs on its posterior aspect.

Male: The proportional lengths of the cephalothorax and abdomen are as 1.04 to 1. The 4th and 5th segments of the thorax are fused together
The abdomen possesses five segments.

The furcal rami are thus nearly three times the length of the anal segment and are six times as long as wide; they bear 5 setae, 4 being at the distal end, and a single one arises from the external margin. The right ramus bears a fringe of hairs on the proximal part of its margin.

The 1st antenna is asymmetrical on the two sides; it reaches to just beyond the tip of the furcal ramus. On the right side the antenna resembles that of the female; segments 7 and 8 are completely and 8 and 9 are partially fused; the 1st, 2nd, 4th, 5th and 6th segments all bear small spines that are less developed. The left antenna is modified to form a grasping organ.In the left antenna, segments 1 and 2 are fused together as also are segments 7, 8 and 9; the spines on the proximal segments are weak. The knee-joint is situated between segments 18 and 19, in the usual situation. The 17th segment bears a toothed plate, which is produced distally over the 18th segment and is armed with small teeth. The 18th segment is also armed with a toothed plate, that bears about 55 curved teeth; the plate is not as long as the segment and is not upturned at the end. The 19th to 21st segments are fused together into a single piece from which two tooth plates arise near the proximal end; of the two plates the proximal is armed with small teeth, while the distal is plain. Segments 22 and 23 are fused together and are not separate.

In the 5th pair of legs, each leg consists of a basal portion and four free joints. In the left leg the proportional lengths of these free segments are as follows: 27, 13, 19 and 41. The 1st segment bears a single seta and internally is rounded at its distal end, the prominence being fringed with hair. The 2nd segment is fringed with hair internally. The 3rd segment bears a small spine on its external border and is fringed with hair on its inner margin. The 4th segment is spoon-shaped and bears two small spines distally, as well as a small spine on its outer and posterior margin. The basal segment bears a scattered tuft of hairs on its posterior aspect. On the right side the proportional lengths of the segments are as 32, 12, 19 and 37. The 1st segment bears a single seta posteriorly; the 2nd segment carries a small external marginal spine and a long curved process internally; the 3rd segment has a small spine anteriorly and the 4th segment is spoon-shaped and bears a small spine on its external and anterior aspect and two small spines distally.



Synonym (s)
Metridia macrura Sars, 1905
Metridia macrura A. Scott, 1909
Metridia princeps Wolfenden, 1911
Metridia macrura Sewell, 1913
Metridia macrura Sars, 1925

Common Name (s)
Economic Importance and Threats

Ecology

Biogeography


• Bay of Bengal (Lat: 7.35) (Long: 85.12) INDIA (Record: 21/10/1911)
• Kerala, Off Kochi (Lat: 10.43) (Long: 74.54) INDIA (Record: 28/04/1925)

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 - http://www.marinespecies.org

Page last updated on:2011-03-15

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