(Sponges and Rotifers) Marine Invertebrates (Sponges and Rotifers)

Sponges Sponges are multi-cellular, and come in many sizes, colors, and shapes. Sponges have few specialized structures, and are found in warmer, tropical waters. Sponges are made up of 2 layers: Endoderm- inner layer Ectoderm- outer layer Between the 2 layers is a jelly-like material called mesenchyme.

Sponges belong to the phylum Porifera, which means “pore bearing”. Sponges are considered Benthic organisms, they are bottom dwelling.

Sponge Anatomy

How do Sponges Feed? Sponges are sessile- they spend their lives attached to an object. Sponges bodies contain many holes. Sponges bodies are elastic. All parts of a sponge are the same. They feed by taking in the plankton and algae found in water through small pores called ostia. Water and wastes exit through a large hole called the osculum.

7. Collar Cells line the inside of the sponge and have flagella that sweep food into and pump water out of the sponge. Digestion takes place inside the food vacuoles in each individual cell. Gases are also exchanged at the cellular level. Sponges have no nervous tissue, they do not respond to touch, and will not move.

How do Sponges Reproduce? Sponges can be male, female, or both (hermaphroditic). They can also reproduce asexually by regeneration.

Rotifers Rotifer means “wheel bearer”. Rotifers live in the moist sands along the shore, as well as, in freshwater. They belong to the phylum Rotifera. They can change the shape of their bodies and telescope them to make it easier to move their cilia. They are both sessile and motile.

How do Rotifers Eat? They are predators…they create a current by beating their cilia and take food in. Food passes through a one way digestive tract. Food is digested in the stomach or the intestines. Wastes are eliminated through the anus.

How do Rotifers Reproduce? Rotifers can be male or female. Males produce sperm in the testes. Females produce eggs in the ovaries. Gametes are released into the water where they fuse. Rotifers fertilize externally. They can also reproduce asexually by a method called parthenogenesis ( a complete egg is produced w/o fertilization and has a complete set of chromosomes).

Rotifers

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