Maturation of overy,embryonic and post-embryonic larval development of macrobrachium canarae (TIWARI,1958)

Abstract- M. canarae (Tiwari, 1958) is a medium sized prawn which has been reported to occur widely throughout the Kerala. The present study is on the reproductive biology of the species such as the determination of maturity stages based on the external observation, time taken for transforming to different maturity stages, breeding behavior, embryonic development, larval development and the importance of the species as a candidate species for aquarium.

The re-examination of maturity stage is done mainly by observing the external morphology of the ovary through the carapace. The maturity stages are determined mainly by looking the colour of the ovary, the distribution of chromatophores over the ovary, the shape of the ovary, the space occupied by the ovary in the cephalothorax and the appearance of the egg. Seven maturity stages of ovary are distinguished in M. canarae. They are immature ovary, early maturing ovary/spent recovering ovary, partially matured ovary I, partially matured ovary II, late maturing ovary, fully matured ovary and spent ovary. Along with this the time taken for transforming to different maturity stages has been noted. The average time taken for transforming to different maturity stages are: Stage I: approximately 155-180 days, Stage II: 5 days, Stage III: 6 days, Stage IV: 6 days, Stage V: 7 days, Stage VI: 7 days, Stage VII: 2 days.

The breeding behaviour of the species has been studied. The breeding behavior of the species is classified into premating behavior, mating behavior, post-mating behavior, spawning and post spawning activity.

The incubation period of the species is found to be 26-28 days in aquarium condition at a temperature of 24ºC to 28ºC. The embryonic development of this species is classified into 7 stages based on the morphological features, yolk content, appearance of appendages, initiation of the heart-beat, appearance of eye pigmentation, condensation of eye pigment, etc. The stages are post fertilization/precleavage egg (0-3 hours), cleavage egg (3 hours- 5TH day), gastrulation (6th -9th day), fully embryonized naupliar stage (10th -11th day), embryonized protozoeal stage (12th day), embryonized zoeal stage (13th day – 25th day), prehatching stage (any day in between 26th -28th day). The gastrulation is again divided into early gastrulation, blastopore stage and V- shaped germinal disc stage. Embryonized zoeal stage is also divided into early zoeal stage and progressing zoeal stage.

There are 3 zoeal stages for M. canarae and then it transforms into postlarvae. The larval phase is completed in 12 days. A detailed study on the larval characters has been made and fully illustrated.

The aquarium importance of the species is also studied. The species possesses brilliant orange red spot on its 2ndcheliped and the dark bands on the carapace and hence this species can be considered to have ornamental value.