Euchirella orientalis   Sewell,  1929 (Copepod)
Organism information awaits expert curation
Taxonomy
Kingdom:Animalia
Phylum:Arthropoda
Class: Maxillopoda
Order:Calanoida
Family:Aetideidae

Description
Size (female): length 4.8 mm
Size (male): 3.7 mm

Female: The proportional lengths of the cephalothorax and abdomen are as 3.53 to 1. There is no frontal crest and the single pointed rostrum is stout and points vertically downwards. The posterior thoracic margin is rounded.
The abdomen consists of the usual four segments, the 1st or genital segment is as deep as long and is swollen in a rounded prominence on the dorsal aspect, the whole segment is symmetrical or but slightly asymmetrical in some cases, the left side being a little more prominent than the right.
The 1st antenna reaches back to the middle of the 2nd abdominal segment. Segments 3, 7, 9, 14 and 18 all bear long setae and segments 22 to 24 all bear posterior setae that increases in length distally. In the 2nd antenna the two branches are very unequal, a condition seems to be characteristic of the genus. The proportional length of the two branches are as 15 to 51. The endopod reaches only half way along the 1st joint of the exopod. The terminal segment of the endopod bears 6 setae on each of its two lobes. All the setae on the lobes of the endopod are short and the inner three on the inner lobe extremely so. The 1st segment of the exopod appears to be devoid of a seta, and is completely fused with the 2nd segment, which is also devoid of a seta; at the point of junction is a small rounded projection.
In the mandible the basal segment appears to have no setae; the endopod bears 9 setae, of which the inner two are short. In the 1st maxilla the basal segment bears three setae, of which the inner two are short. The endopod bears 4 setae. Of the inner lobes the 1st bears 13 to 14 setae, the 2nd lobe 4 and the third lobe a single seta. The exopod carries 11 setae. Each of the lobes of the 2nd maxilla bears 3 setae and all have a fringe of needle-like spines distally. In the exopod the 1st segment bears 2 setae and the 2nd only one and the terminal segment 4. In the 1st basal segment of the maxilliped, lobe 1 bears 2 setae and lobe 2 carries 3, of which the 1st is short and plain, the 2nd is of medium size and is finely serrated and the 3rd is also of medium length but is coarsely serrated in its middle third; lobe 3 bears 3 setae and is, in addition, fringed with spinules or stout hairs. In the 2nd basal segment the posterior margin is sinuous; the anterior border bears 3 setae about the middle of its length and two unequal setae at its distal end; the proximal half of the margin is armed with a row of fine needle-like spines. On the five segments of the endopod the number of setae are 4, 3, 3, 3, 4 respectively. In the 1st swimming leg both basal segments are fringed on their inner borders with long hairs and the 2nd segment carries the usual long seta at its inner distal angle. The exopod consists of two segments only, exopod 1 and 2 being fused, though the combined joint carries two marginal spines, of which the proximal is the more delicate. The margin between these two spines is indented and is perforated by a pore; this part of the external margin, as well as the proximal half of the margin of the distal segment, is fringed with hairs. The marginal spine of the distal segment is stout and is about three fourths the length of the segment. The endopod reaches as far as the joint between the two segments of the exopod and the rounded swelling on the outer margin is fringed with short spines. In the 2nd swimming leg, the 1st basal bears a single seta and the inner margin is fringed with hairs; basal 2 has a smooth inner margin. The exopod consists of three segments; in the 1st segment there is a marginal spine and the inner border is fringed with hairs and bears a small seta; the marginal spine on the 2nd segment may reach as far as the base of the proximal spine on the 3rd segment, the inner margin of this segment is smooth and bears a normal seta; in the 3rd segment the two proximal spines are sub-equal, while the distal spine is larger, the inner border bears four setae and the end-spine possesses 21 serration on its margin. The endopod consists of a single segment, bearing a small seta on the outer margin, two at the distal end and there on the inner margin; there is small spine like projection on the outer margin near the proximal end. In the 3rd swimming leg both exopod and endopod are three-jointed. Exopod 3 bears three equal marginal spines and the end-spine has 20 serrations on its outer border. In great majority of cases, the 4th swimming leg bears two sub-equal spines on the 1st basal segment; these spines reach as far as the level of the line of articulation between the two basal segment. In a few cases there are three spines.

Male: The cephalothorax is ovate and robust. The forehead is rounded and is devoid of any crest. The rostrum is strong and of moderate length and is directed ventrally. The cephalon and the 1st thoracic segment are fused and thoracic segments 4 and 5 also appear to be partially fused. The posterior thoracic margin is rounded. The abdomen appears to consists of only four segments owing to the anal segment being completely telescoped into the 4th segment. The posterior margins of segments 2 and 3 are armed across the dorsal aspect with a row of triangular spines. The furcal rami are short, being about three-fourths the length of the 4th segment of the abdomen.
The 1st antenna reaches back to about the middle of the abdomen. It consists of only 19 free joints; segments 8 and 9 are completely fused and the combined mass is partially fused to segment 10, the 12th and 13th segments appear to be partially fused, as also do segments 14 and 15. In the right antenna segments 20 and 21 are fused and on both sides segments 24 and 25 form a single joint. The 2nd antenna possesses an endopod that is about half the length of the exopod. Exopod 1 and 2 are clearly separated off from each other, but the 1st segment bears no seta. The terminal segment of the endopod bears 6 setae on each of its lobes.
In the 1st swimming leg the exopod consists of only two separate segments, exopod 1 and 2 being incompletely separated. The combined two proximal segments bear two very small marginal spines; the terminal segment bears a stout marginal spine that is about half the length of the segment. The endopod consists of a single segment that exhibits a rounded swelling on its external margin, this swelling being fringed with needle-like spines. In the 2nd pair of legs the exopod is 3-jointed and the endopod is composed of a single joint. The marginal spine on the 2nd segment of the exopod does not reach as far as the base of the proximal spine on the 3rd segment.




Synonym (s)
Euchirella pulchra Sewell, 1913

Common Name (s)
Economic Importance and Threats

Ecology

Biogeography


• INDIA (Record: 21/10/1911)

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:2010-07-06

Back to Search