Sagitta nairi   Casanova & Nair,  2002 (Marine Worm)
Organism information awaits expert curation
Class: Sagittoidea

Image copyrights: Taylor & Francis

Dorsal view: af, anterior fins; c, collarette; id, intestinal diverticula; o, ovaries; pf, posterior fins; sv, seminal vesicles; tf, tail fin; vg, ventral ganglion.

Max. size: 5.2 mm.

The tail constitutes 28.5-30.2% of the total body length without tail fin. The body is slender, slightly rigid and transparent. In dorsal view, the head is peculiar owing to the bases of each set of anterior teeth, right and left, that are well seen and aligned in regular rows, so that its anterior side has two more or less prominent swellings. These teeth, 11-14, are large and strong, a characteristic feature. Their shape also is curious: in ventral view, they look like flattened arrows, the outermost over-lapping the innermost; in lateral view, they are S-shaped. Their narrow base is ornamented with ridges constituted of rows of small spines. Posterior teeth, 11 and 12, are less numerous than the anterior ones, which is not common; they are long, thin, bent at their bases and in close contact with each other. Hooks are seven to eight; the base of the anterior ones is enlarged and thus their inner and outer sides have no regular curve. The vestibular organs are smooth. Two symmetrical plates enclosing the inner bases of the hooks correspond probably to the ventral plates. Such a disposition seems never to have been seen since the plates are covered by the cuticle lying on the ventral side of the head.
The eyes are large and rounded; the pigmented area is also roughly rounded, but a careful observation of some specimens allows recognition of the pigment cell looking like a stumpy star. The collarette is thin and restricted to the neck region. Corona ciliata begins behind the eyes and reaches posteriorly at least a distance equal to twice the length of the head. Two well-marked intestinal diverticula are present at the beginning of the gut, in the neck area. The ventral ganglion is large, representing about 11% of the body length. The anterior fins begin at the level of the posterior end of the ventral ganglion. The posterior fins do not reach the seminal vesicles. They lie much more on the tail than on the trunk, so that the ratio T/C (part on trunk/part on caudal segment) = 0.40-0.53. In the large specimens, the tail coelomic cavities are filled with clusters of sperm. The seminal vesicles are small and elongated; they open laterally at the anterior part that protrudes into a slight swelling. They are apart from the posterior fins, and separated from the tail fin by a distance equal to less than their mid-length when mature.

Synonym (s)
Sagitta nairi Casanova & Nair, 2002
(Senior synonym)

Common Name (s)
Economic Importance and Threats

Habitat:  Pelagic


• Lakshadweep, Agatti Lagoon (Lat: 10.83) (Long: 72.2) INDIA
• Lakshadweep, Agatti Lagoon INDIA (Record: 09/12/1988, 10/12/1988)

Literature Source(s)
  • Nair, VR Chaetognatha NIO, Goa Available at -
  • Casanova, JP and Nair, VR (2002) A new species of Sagitta (Chaetognatha) from a Laccadive lagoon (Indian Ocean) having fan-shaped anterior teeth: phylogenetical implications Journal of Natural History Taylor & Francis 36(2) 149-156 Available at -
  • Society for the Management of European Biodiversity Data (2009) World Register of Marine Species (WoRMS) Available at -
  • Sealifebase Available at -

Page last updated on:2011-06-24

Back to Search