Megacalanus longicornis   (Sars G.O.,  1905) (Copepod)
Organism information awaits expert curation
Class: Maxillopoda

Size (male): length 9.5 mm.

The proportional lengths of the cephalothorax and abdomen are as 14 to 5. The process on the posterior margin of the head in the mid-dorsal line is well marked. The posterior thoracic margin ends in a small blunt projection. The furcal rami are symmetrical and bear five marginal setae, of which the 2nd is the longest, and an accessory dorsal seta. The inner borders of the rami are fringed with hair. The antennae on the two sides of the body are different, that on the right side being modified into a grasping organ. On the left side, the antenna consists of twenty-five segments. Segments 7, 8, and 9 are fused together, and in addition so are segments 12 and 13, and these last two segments are armed with longitudinal rows of needle-like spines. There is a distinct elbow-joint between segments 18 and 19 and the terminal part of the antenna consists of six free segments.
In the 2nd antenna, basal 1 bears a single seta and a row of hairs; basal 2 bearers two setae. The exopod bears a single seta. Endopod 1 bears a tuft of setae distally on its inner margin and has a ‘’macula cribrosa’’ on the anterior surface at the base of the distal third; endopod 2 bears a tuft of setae on its border.
The mandible is strongly armed on its biting surface with 5 large cusped teeth and three pointed teeth, and a serrated spine arises from the posterior margin; along the base of the biting teeth runs a row of needle-like spines, the 1st basal also bears a group of needle like spines on its margin near the joint with basal 2 and a tuft of hairs about half-way along the anterior margin of the masticatory lobe; basal 2 bears a single seta about the middle of its length and three setae distally on the prolongation of the segment that bears the endopod. The 1st joint of the endopod is produced in a rounded swelling and bears a tuft of hairs externally. The exopod is of the usual type. A “macula cribrosa” is situated on the basal portion of basal 1 and another is to be found on basal 2 near the articulation of the exopod. There are two maculae, each consisting of a ring of 7 pores, but in my specimen there are 14 pores arranged in an oval with three other pores enclosed within the ring.
In the maxilla the 2nd basal bears 4 setae, the 1st inner lobe bears 14 setae, the 2nd 5 and the 3rd 4; the 1st outer lobe carries 9 setae and the 2nd a single one. The endopod consists of two segments each bearing 7 setae, the exopod bears 11 setae and distally has a rounded swelling clothed with hair. A ‘macula cribrosa’ is situated near the base of the external lobe.
In the 2nd maxilla, the 1st lobe bears 6 setae, the 2nd, 3rd and 4th lobes bear 3 setae each, the 5th lobe bears 3 setae and one hook, while the 6th lobe bears one large seta and three small ones. The 5th lobe is much the largest. The terminal joints bear 7 setae. All the setae bear stiff hairs set wide apart. A ‘macula cribrosa’ is situated on the anterior surface of basal 1.
The maxilliped consists of a two-jointed basal portion and an endopod of four segments. In the 1st basal lobe 1 bears 1 seta, lobe 2 has 2 setae, lobe 3 has 4 and so has lobe 4; the 2nd basal bears a group of 3 setae on its inner border about the middle of its length and two others distally. There is a row of needle-like spines extending along its anterior margin throughout the proximal half, as far as the group of setae.
In the 1st swimming leg the 1st basal bears a tuft of long hairs on its anterior aspect. Basal 2 carries the hook and bristle that are so characteristic of this species; these are situated on the anterior aspect of the limb .
A ‘macula cribrosa’ is situated on the anterior surface of the segment and rather towards the median side near the insertion of the endopod.
Both rami are three-jointed. Exopod 1 bears a single spine externally and one seta internally. Exopod 2 bears also one seta internally and a single marginal spine; on the external margin just proximal to the spine is a tuft of hairs. A ‘macula cribrosa’ is situated on the anterior aspect near the base of the marginal spine and a little to the inner side. Exopod 3 bears two spines and there are four setae on the inner margin; the distal spine is extremely long. All the marginal spines are long and slender and are serrated on both borders and on the proximal side of each a tuft of hairs arises from the margin of the exopod. The proportional lengths of the three segments of thee exopod and the distal spine are as 26: 17: 35: 40. Endopod 1 bears a single seta; endopod 2 bears 2 setae and there is a ‘macula cribrosa’ on the anterior aspect about the middle of its length; endopod 3 bears 6 setae. The external margin of both the 2nd and 3rd segments is fringed with hairs.
In the 2nd, 3rd and 4th swimming legs the 1st basal segment bears a ‘macula cribrosa’ near the outer margin and there is a second on the 2nd basal segment situated just mesially to the articulation of the exopod. A third lies in the 1st segment of the exopod near the base of the marginal spine and a fourth is situated on endopod 2 near the distal margin. There is a tuft of fine needle-like spines on the anterior aspect of endopod 3 near the base of the proximal outer seta.
In the 5th swimming leg in the male, there is one ‘macula cribrosa’ on the 1st basal segment, but there is one on the 2nd basal near the articulation of the exopod, another ‘macula’ is situated on the 2nd segment of the exopod near the distal outer angle and a third on the 3rd segment of the same ramus near the distal outer angle and a third on the 3rd segment of the same ramus near the base of the 1st marginal spine.

Synonym (s)
Megacalanus princeps Wolfenden 1904
Megacalanus bradyi Wolfenden 1905
Macrocalanus longicornis Sars 1905
Megacalanus longicornis Pearson 1906
Megacalanus longicornis Farran 1908
Megacalanus longicornis V. Breemen 1908
Megacalanus princeps A. Scott 1909
Megacalanus princeps Wolfenden 1911
Megacalanus princeps Sewell 1913
Megacalanus princeps With 1915
Megacalanus princeps Lysholm and Nordgaard 1921
Megacalanus longicornis Sars 1925
Megacalanus princeps Farran 1926

Common Name (s)
Economic Importance and Threats



• Bay of Bengal (Record: 1910-1925)
• INDIA (Record: 1910-1925)

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 -

Page last updated on:2011-03-10

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