Comprehensive Description

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Diagnostic characteristics:

Body is highly transparent, flaccid, flexible and wider at the centre. The longitudinal muscles are thin and weak. The lateral fields are wide. Conspicuous constriction is observed at the tail septum. Intestinal diverticula are absent. Head is small compared to body and wider than long. Neck is narrow and well marked. Tail percentage to total length 14-17. Eyes placed closer to each other than sides of the head. Eyes oval and pigmented region shaped like five pointed star with tips truncated and two arms longer than other three. Collarette absent. Corona ciliata short and placed almost entirely in head. Ventral ganglion is situated about midway between head and anterior fins. Anterior fins are short and narrow and placed about midway between neck and tip of the tail. Fin rays are absent in the inner part. Posterior fins are slightly longer than anterior fins, wider at caudal septum, extend more on trunk than tail segment and do not reach seminal vesicles. Inner most part of the posterior fins ray less.

Sex attributes:

Hermaphrodite. Male gonads being located in the tail segment, the female in the posterior part of the trunck. Though hermaphrodite cross - fertilization by copulation is the rule.

Descriptive characters: When fully mature ovaries reach either up to two thirds of posterior fins on trunk or to anterior end of posterior fins or up to anterior fins depending on the first, second or last maturity cycle. Ova are large round and arranged in three rows. Seminal vesicles separated from posterior fins and close to tail fin. Seminal vesicles are spherical, small and break open by a fissure at anterolateral margin through which sperms are liberated. Testis occupies the posterior part of tail segment extending from tip of tail and extend the tail to about half the length of tail.

Meristic characteristics:

Hooks vary from 8 to 10 on each side with wide base and short curved sheath. Anterior teeth range between 4 and 8 at each side. Posterior teeth number 4 to 13 per set.

Additional remarks: Representatives of different sizes belonging to 3 maturity cycles often represented in same sample indicating the presence of different populations in which maturity reached at various length-sizes. This indicates the species undergoes consecutive cycles of maturity corresponding with their increase in size.


Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Census of Marine Zooplankton

Source: Census of Marine Zooplankton

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