1. preserved Nereis The proboscis may be extended. It is divisible into an oral

Question

1. preserved Nereis

The proboscis may be extended. It is divisible into an oral ring nearest the peristomium, bearing tiny, horny paragnaths, and the more distal maxillary ring, also bearing paragnaths and at its tip a pair of horny jaws. The extended, but not everted part of the gut opening at the jaws, is the pharynx. If the proboscis is not extended try to evert it yourself. Using a blunt object like the back end of your forceps, press on the segments about a centimeter posterior to the peristomium. If you've hit the right spot, you ought to be rewarded by seeing the eversible pharynx of the worm pop out of the mouth. You everted the pharynx more or less like the

worm does it by increasing the pressure of coelomic fluid in the surrounding segments, eventually pushing it out. How does the worm reinvert it?

2. differences in external anatomy/ morphology between Nereis sp. and Glycera sp.

3. descrive the flow of blood in the intact tentacles of Phragmatopoma and the nature of the circulation.

Explanation / Answer

Ans-1 the worm reinvert themselves by creating the pressure diffrence in the celoemic fluid. By creating this pressure difference their body parts start to move according to this internal pressure and help in reinverting.

Ans-2 neris body is divided into segments externally while the glycera body is not as much segmented. Neris have seatea and perapodia for the locomotion while the glycera have only perapodia. Neris are smaller in length as compare to glycera species .

Ans-3 the nature of circulation in the phragmatopoma is closed central circulatory system. The blood flow from the heart which is undivided and through six arches into diffrent tentacles via artries and cappillaries.

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