HOW TO: Dissect a Starfish

Starfish (Sea Star)

Background

These invertebrates reside in all parts of the ocean, including the Atlantic Ocean to the Indian Ocean. Starfish primarily feed on clams, oysters, sand dollars, mollusks and mussels. Starfish are able to breathe through their feet. Their feet are made of a very thin tissue in which gases can move easily. Ironically, starfish are not actually fish. They do not have gills, fins, or scales like fish do. They move with their feet while fish propel themselves through the water.

External Anatomy

Aboral Surface— side of the starfish without a mouth ("top")

Oral Surface— side of starfish with mouth ("bottom")

Eyespot— lies underneath the skin, can detect light and dark

Central Disc— center of the starfish from which the arms start from, contains the madreporite, mouth, and anus

Madreporite— used to filter water into the water vascular system of the echinoderms

Ambulacral Groove— contains the feet on the oral side and used to open up shells for food

Internal Anatomy 

Digestive glands— break down food by the use of enzymes and connected to the stomach

Ring Cartal— carries water from the stone canal to the radial canal, connects the two canals

Ossicles— forms part of the exoskeleton and provides protection and strength

Gonads— reproductive organs (ovaries or testes) that are used with reproduction by producing egg or sperm

Lateral (Radial) Canal— runs the length of the starfish arm and is part of the water vascular system

Ampulla— fills up with water and then releases water to feet

Incision Guide

Dissection Procedure