Embryogenesis of the sea urchin strongylocentrotus purpuratus (stimpson, 1857) under normal and bioactive conditions

Adults of Strongylocentrotus purpuratus were collected during September to June (2012) and July to August (2014) along the northern estruarineharbor of the Arabian Gulf – Saudi Arabia. Procurement of gametes has been carried out by potassium chloride injection using a one ml tuberculin syringe equipped with a 26 or 30 gauge needle. Gentle shaking of the animal anticlockwise 90◦ after few minutes of injection aided in gamete shedding. Gently sperm and eggs were mixed with a clean stirring rod. The different embryonic stages till the complete metamorphic plutei were described. The time schedule for different stages has been tabulated. Embryonic stages were stained with Nile blue and were placed on glass slides with embedding mixture of PBS / glycerol / DABCO. Immediate viewing and photographing were performed under an Axiomicroscope (ZEISS-Axiophot). Sperm are very small and extremely motile while the egg (70 to 180 µm in ϕ) had yellow to orange jelly-coat. Zygote (3 min. after fertilization) has undergone radial holoblastic cleavage till the blastula stage (3.50-4.15 hrs. after fertilization).The early blastula had a blastoderm enclosing a central blastocoel (6 hr 20 min. after fertilization). Cilia were developed on the exterior of the blastoderm and gradually this embryonic stage hatched and became a free-swimming blastula (8 hr 40 min. after fertilization). At the animal pole an apical plate was formed in the form of a thickened region of epithelium with a tuft of long cilia while the epithelium at the vegetal pole flattened and thickened to form the vegetal plate (16hr 45min.. after fertilization). Ingression of primary mesenchyme cells into the blastocoel took place and a new cavity was formed referred to enteron. The larval mouth was formed (19hr 15min. after fertilization). The blastopore developed into the anal opening of the digestive tract. During the prism stage the embryo took the shape of a rounded pyramid (21 hr 20 min. after fertilization). Pluteus larva with two arms was developed (24hr 30 min. after fertilization). A pluteus larva developed into four-armedpluteus (29hr 40 min. after fertilization). The later fed and developed into eight-armed pluteus (145 hr 50 min. after fertilization). A period of extensive feeding and continued larval development was required before metamorphosis to a juvenile sea urchinr. Free swimming blastulae were subjected to certain bioactive inducers which had been claimed to induce metamorphosis, involved in signaling systems, serve in neuronal control, control morphogenetic and behavioral reactions or interact with members of several signal transduction proteins pathways under normal physiological conditions. Results of these trails were introduced to One-way analysis of variance (ANOVA) with P < 0.05 and Dunnett's Multiple Comparison Test with P > 0.05 or P < 0.01. It has been concluded that Acetyl choline 0.5 mM, Serotonine10 g/ml, NOS 2.5 mM, C81 µ M, NH4ClNH4Cl and cGMP 1 g/ml accelerated the transformation of blastula stage to an advanced pluteus larval stage with 8 arms whereas Acetyl choline 30 µ g/ml & 1 mM, NOS 1.5 mM, C8 10 µM and NH4Cl 300 µM exereted no role in metamorphosis and antibiotic sea water had negligible effect.