Morphometric study of embryonic development ofMacrobrachium borellii(Arthropoda: Crustacea)

Summary Embryo morphometry and developing time from just-laid eggs until hatching were described in the palaemonid prawn, Macrobrachium borellii, using a rapid non-invasive staging method. Embryos were kept in the laboratory under controlled conditions and development divided into seven stages according to major morphological characteristics. This lecithotrophic, freshwater shrimp has a highly abbreviated type of hatching development after 39 ± 2 days as postlarvae at 24°C. Morphometry was recorded using a stereoscopic microscope with an image analyzer. Area, perimeter, maximum and minimum diameters and shape were measured in yolk sac, egg-coat and eye, respectively, and they were statistically selected as the best to define the stages. Eggs are ovoid with a maximum diameter that varies from the moment of oviposition to the time of hatching from 1.5 to 2.0 mm, respectively. Water content and egg size increase along with development, whereas egg shape only varies just before hatching when the egg becomes s...