Euchaeta tenuis [Status Unaccepted]   Esterly,  1906 (Copepod)
Organism information awaits expert curation
Class: Maxillopoda

Size (male): length 5.0 mm.
Size (female): length 4.9-6.8 mm.

Female: The proportional lengths of the cephalothorax and abdomen are as 54 to 25, so that the abdomen is a little less than half the length of the anterior region of the body. The posterior margin of the thorax is rounded and is somewhat sparingly provided with hairs. The abdomen consists of four segments. The ventral region of the 1st segment is produced in a large prominence, which carries the genital opening and terminates in two unequal flaps, that on the right side being much the larger. The right side of the segment is traversed by a transverse groove along which the chitinous exoskeleton is thickened. There is a minute tubercle on each side in the dorso-lateral region about the middle of the length of the segments. All the abdominal segments are clad in short hairs and there is a brush of long hairs on the ventral aspect of the 3rd segment, while on each side of the 4th segment, close to the articulation with the furcal ramus, is a tuft of similar long hairs. The 1st segment bears a tuft of hairs on its dorsal aspect anteriorly and both the 2nd and 3rd segments are armed along the dorsal side of the posterior margin with minute spinules. The furcal rami terminate obliquely and the 2nd furcal seta is much thicker than the others.
The 1st antenna reaches to the furca and is composed of 23 segments; segments 8 and 9, and 24 and 25 being respectively fused. In the 1st pair of swimming legs, the exopod consists of only two joints, the 1st and 2nd segments being completely fused; there is no marginal spine on the part of the combined joint that corresponds to exopod 1. The spine on the part corresponding to exopod 2 reaches to beyond the distal margin of exopod 3. The endopod consists of a single joint that shows a swelling on the outer margin and this swelling is crowned with a row of short hairs or hair-like spines. In the 2nd pair of legs, the spine on exopod 2 is large and reaches to the end, or very nearly to the end, of the proximal spine on exopod 3 and the middle spine on exopod 3 falls short of the base of the distal spine.

Male: The proportional lengths of the cephalothorax and abdomen are as 57 to 24, so that in this sex the abdomen is contained 2.375 times in the length of the anterior region of the body. The forehead terminates anteriorly in a well marked rounded supra-rostral eminence and the rostrum, which is strong, projects downwards and slightly backwards. The posterior thoracic margins are rounded. The abdomen consists of five segments, byt owing to the complete manner in which the 5th segment is telescoped into the 4th, at first sight it appears as if there were only four. The 2nd, 3rd and 4th segments are armed across the posterior dorsal margin with a row of coarse teeth. The 2nd furcal seta is about twice as long as the others and the accessory setae are also long.

The 1st antenna reaches back to the middle of the 3rd abdominal segment. The 8th, 9th and 10th segments are completely fused together and the 12th and 13th partially so. In the 2nd antenna the endopod bears 8 setae on the inner lobe and 6 on the outer. In the mandible the exopod bears 6 setae and the endopod 9. In the 1st maxilla, the 1st inner lobe bears 11 setae, the basal segment bears 3 and the endopod carries 1 setae each on the 1st and 2nd segments and 3 on the 3rd. The 2nd and 3rd inner lobes each bear a single seta. The exopod bears 11 setae and the outer lobe 8.
In the female the 2nd basal segment of the maxilliped bears three setae on its anterior margin at the junction of the proximal and middle thirds of its length; in the male, however, these appear to be completely absent. The distal end of this segment bears 2 unequal setae. In the endopod the various segments bear the following setae; endopod 1, 2 large and 2 unequal small setae; endopod 2, 1 large and 2 unequal small; endopod 3, 1 large and 1 small; endopod 4, 1 large and 1 small on the anterior aspect and 1 small externally; and endopod 5, 2 large and 2 small. The 1st pair of swimming legs have a three-jointed exopod, of which the 1st segment bears a fine seta on its margin distally and the 2nd segment bears a spine that reaches a little beyond half-way to the base of the spine on exopod 3.
The 2nd pair of swimming legs bear three spines on the 3rd segment of the exopod; the proximal spine is short bu the second reaches about half-way to the base of the distal spine. The 5th pair of legs are of the true Euchaeta type, that is to say, the exopods of both right and left legs terminate in a long spiniform segment. The 2nd segment of the left leg bears a tooth-plate which is rounded and is armed around its circumference with a row of triangular teeth. This tooth-plate appears to be fused with the finger-like process at its base, the free portion of the digitiform process extending beyond the tooth-plate by nearly the same distance.

Synonym (s)
Euchaeta tenuis Esterly, 1906
Euchaeta tenuis A. Scott, 1909
Euchaeta solida Esterly, 1911(b)

Common Name (s)
Economic Importance and Threats

Habitat:  Estuarine, Coastal


• West Bengal, Sundarbans (Lat: 21.5) (Long: 88.17) INDIA
• Bay of Bengal INDIA (Record: 21/10/1911)
• West Bengal, South 24 Parganas INDIA

Literature Source(s)
  • Mandal, AK and Nandi, NC (1989) Fauna of Sundarban mangrove ecosystem, West Bengal, India Fauna of Conservations 3 35431 Available at - NIO, Goa
  • Tanaka, O Euchaeta of the Indian Ocean Copepod 130-139 Available at - NIO, RC Kochi
  • Madhupratap, M and Haridas, P (1986) Epipelagic calanoid copepods of the Northern Indian Ocean Copepod 105-117 Available at - NIO, RC Kochi
  • 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 -
  • Roy, MK (2010) Diversity and Distribution of Crustacea Fauna in wetlands of West Bengal Journal of Environment and Sociobiology Social Environmental and Biological Association, Kolkata, India 7(2) 147-187 Available at - NIO,Goa

Page last updated on:2011-10-27

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