By: David Quesada
Echinodermata
Introduction
Echinodermata is a phylum that holds aquatic animals that usually have a unique five-point radial symmetry. Echinodermata are found at nearly all depths of the ocean and contains nearly seven thousand species. They all have spiny skin, hence the Greek name Echinodermata. Most animals belonging to this phylum have the ability to reproduce asexually and also to repair damaged body tissues.
Echinodermata is a phylum that holds aquatic animals that usually have a unique five-point radial symmetry. Echinodermata are found at nearly all depths of the ocean and contains nearly seven thousand species. They all have spiny skin, hence the Greek name Echinodermata. Most animals belonging to this phylum have the ability to reproduce asexually and also to repair damaged body tissues.
Red Cushion Sea Star (Oreaster Reticulatus)
The cushion sea star has separate sexes (gonochorous) and are not hermaphrodites. Within an arm of the starfish there are two gonads which release gametes through opening called gonoducts. Sperm and eggs meet to form embryos and larvae through free spawning. They then gather in a group and move with the currents. Larvae feed on plankton and other small animals. This species is also able to reproduce through fission. Fission is the process were an organism splits in fragments and regenerating. Another form of asexual reproduction this starfish is able to carry out is budding. This process is when an organism or in this case a larvae forms a outgrowth that separates from a matured adult creating a genetically identical organism. However, this delays the development of the starfish and creates scar tissue.
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Red Heart Sea Urchin (Meoma Ventricosa)
Sea Urchins are dioecious and reproduce externally. Males nest at higher locations so their sperm or milt can be carried by sea currents while females generally live in sea bottoms which are safe for larvae. The majority of urchins have five gonads with a gonoduct reaching to its gonopore. The gonopore is located near the anal plate. Muscles within the gonads allows the urchin to control its release of gametes. It is extremely rare for an urchin to have four gonads. Once fertilized eggs develops into embryos relatively quickly. Once developed, the urchin then sinks to the sea floor where is develops into an adult. The red heart sea urchin similar to the sea star also has the ability to reproduce asexually. Self amputation to escape predators, budding, and fission are common ways for urchins to reproduce.
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Leopard Sea Cucumber (Bohadschia argus)
The leopard sea cucumber has two distinct sexes (dioecious) and reproduces externally. It has a single gonad with tubules emptying into a duct near the tentacles. A cucumber can produce and release thousands of gametes at a time. Once fertilized the egg develops into a larva which can swim and move on its own by using a cilia. After 3-5 weeks the larva goes through metamorphosis and sinks to the seafloor. Similar to the other species discussed so far it can also reproduce asexually. They have the ability to regenerate broken off arms and spines.