Gaetanus pileatus   Farran,  1903 (Copepod)
Organism information awaits expert curation
Class: Maxillopoda

Size (female): length 4.1 mm.

The proportional lengths of the cephalothorax and abdomen are as 5 to 1, taking the length of the cephalothorax to include the frontal spine.The 4th and 5th thoracic segments are fused and the 5th segment bears on each side a sharp spine. The abdomen consists in both immature sexes of four segments, of which the most posterior appears to consist of two segments. The furca is nearly as broad as long; the 5th or external seta is extremely small. The posterior margins of the 2nd and 3rd segments of the abdomen are armed with minute spines.

The 1st antenna reaches back beyond the tip of the furcal ramus by about the last seven segments; the whole antenna is nearly twice as long as the body, the proportion being 118 to 66. The maxilla in its general form closely resembles that of the adult but differs in a few details. In these immature forms the three segments of the endopod bear 4, 4 and 6 setae respectively, whereas in the adult only 4, 3, and 6. In both the adult and immature forms the basal segment bears 5 setae and is fringed with hairs along its inner margin. In both forms also the 2nd inner lobe bears 3 setae. In the adult the 3rd inner lobe bears 4 setae and is described as being very much broader than the 2nd lobe but in immature forms , while the number of setae agrees, the lobe is not very much broader than the 2nd. The exopod in these immature forms bears only 10 setae, whereas in the adult it bears 11.

The 2nd maxilla and maxilliped of immature ones appear to agree exactly with those in the adult, except as regards the lamella on basal 1 of the 2nd maxilliped is shorter and more rounded than in the adult.The 1st swimming leg consists of a two-jointed exopod and a single jointed endopod . The 2nd swimming leg possesses a three-jointed exopod and the endopod consists of only a single joint. The 3rd and 4th swimming legs are each composed of a three-jointed exopod and endopod, but in the 4th leg the 1st basal is merely fringed with fine hairs on its inner margin and appears to be without the characteristic row of hairs that is found across the face of the segment in the adult. There is no trace of 5th leg in immature form. At this stage no distinction can be drawn between males and females , as both sexes appear to possess rudimentary fifth feet, which are lost by the female in the final ecdysis at any rate in this genus. In the young male the general structure of the body and appendages agrees closely with that of the females. The antennae, mouth-parts and swimming legs are identical with those of the female, but in addition there is present a rudimentary 5th pair of legs, which agree closely in shape.

Synonym (s)
Gaetanus pileatus Farran, 1903
Gaetanus caudani Wolfenden, 1904
Gaetanus pileatus Farran, 1905
Gaetanus unicornis Esterly, 1906
Gaetanus pileatus Farran, 1908
Gaetanus caudani van Breemen, 1908
Gaetanus caudani A. Scott, 1909
Gaetanus pileatus Wolfenden, 1911
Gaetanus pileatus With, 1915
Gaetanus pileatus Sars, 1925
Gaetanus pileatus Farran, 1926

Common Name (s)
Economic Importance and Threats



• Andaman sea INDIA

Literature Source(s)
  • Manakadan, R and Pittie, A (2002) Standardized english and scientific names of the Indian subcontinent-2002 Newsletter for Birdwatchers S. Sridhar 42 p 35
  • 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 -
  • Padmavati, G; Haridas, P; Nair, KKC; Gopalakrishnan, TC; Shiney, P and Madhupratap, M (1998) Vertical distribution of mesozooplankton in the central and eastern Arabian Sea during the winter monsoons Journal of Plankton Research Cambridge University Press 20 343-354 Available at -
  • Boltovskoy, D (Ed.) Zooplankton of the South Atlantic Ocean Marine Species Identification Portal Available at -

Page last updated on:2011-09-12

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