Labelled Diagram Of Sea Urchin

Urchins are part of the phylum echinoderm and their name comes from ancient greek echinos meaning hedgehog and derma meaning skin.

Labelled diagram of sea urchin. To accurately assess gi of an individual urchin the whole urchin needs to be weighed total wet weight of sea urchin the gonads then need to be. Horstadius 1928 this embryo system has been used recently to. Body is sub globular and convex or dome shaped above and flattened below.

The pores accommodate tube feet which are slender extensible and often sucker tipped. Sea urchin any of about 950 living species of spiny marine invertebrate animals class echinoidea phylum echinodermata with a globular body and a radial arrangement of organs shown by five bands of pores running from mouth to anus over the test internal skeleton. The inside of a sea urchin is dominated by a large coiled digestive system which consists basically of a tube joining the lower mouth to the anus on the upper surface.

Measuring sea urchin gonads the size of a sea urchin gonad is measured as gonad index or gi. The sea urchin embryo initially undergoes ten cycles of cell division forming a single epithelial layer enveloping a blastocoel followed by gastrulation producing the three germ layers. There are more than 900 species of sea urchins and they come in a range of.

Sea urchins are unsegmented and penta radial as adults. They have hard rounded shells covered with sharp movable spines. They have archaically been called sea hedgehogs.

See development lab a. B see also this half shell view figure a shows the aboral opposite. Diagram of the three dimensional orientation of the first 1 second 2 and third 3 division plane.

Urchins typically range in size from 3 to 10 cm 1 to 4 in although the largest species can reach up to 36 cm 14 in. It is commonly known as sea urchin and is formed in shallow water in both rocky and sandy place in sea. Lillie 1912 spermatozoa chemotaxis.