Biology of Finfish and Shellfish

4.12.13. Mysis III

MTL: 3.90 mm (3.43-4.17 mm); MCL: 1.26 mm (1.12-1.37 mm).

Development of 2 segmented pleopod bud distinguishes this sub stage from mysis II, no change in spination of carapace and abdomen, but a very minute rudiment of rostral tooth may be seen in a few specimens; telson long and rectangular carrying 6 distal and 2 lateral setae on each side, cleft extending to level of origin of 3rd pair of setae.

A1 statocyst clearly seen, both flagella are of equal size, inner unsegmented, bearing 4 long slender setae apically, of which one is longer, outer flagellum 2 segmented with 6 to 7 aesthaetes and 2 setae on the distal segment and 2 aesthaetes on the proximal segment; A2 with 2 segmented endopod carrying a long seta apically, exopod with 21 to 22 plumose setae and one anterolateral spine; Md still asymmetrical, palp long, but unsegmented; Mx2with 19 setae on exopod, rudiments of gills present as protuberance on bases of protopod of Mxp; Mxp1 with 12 setae on exopod; Mxp2 with an outer distal seta added to 4th segment of endopod; Mxp3 with endopod longer than exopod, distal segment with 1 short and 3 long setae; PI with rudiment of gill developed at base of protopod, endopod 5 segmented, chela as long as the other 3 segments put together, dactylus apically bearing 2 long setae, propodus with 2 setae at its joint with dactylus; P4 and P5 are identical, exopod as long as endopod, distal segment of endopod with 2 slender setae apically; exopod with 4 apical and 3-4 subapical plumose setae; pleopods 2 segmented and non-setose; distally some pleopods have developing setae uropod with 22 setae on exopod and 21 setae on endopod. Duration of this sub stage was 24 to 48 hours.