Invertebrate Reproduction: A Comprehensive Look

Invertebrate Reproduction

Porifera (Sponges)

They perform both types of reproduction:

• Asexual Reproduction: A small piece of sponge breaks off, anchors to a surface, and regenerates into a complete organism.
• Sexual Reproduction: This requires two individuals of opposite sex. They form sexual cells (sperm and ovum) that join together and produce a larva. The larva then anchors to a surface and grows, forming a new individual.

Polyps

They reproduce both asexually and sexually:

• Asexual Reproduction: A small bud forms and remains attached as it grows. It separates from the parent organism only when mature and then anchors to a surface.
• Sexual Reproduction: This requires two individuals of opposite sex. They form sexual cells (sperm and ovum) that join together and produce a larva. The larva then anchors to a surface and grows, forming a new individual.

Jellyfish

Sexual Reproduction: This requires two individuals of opposite sex. They form sexual cells (sperm and ovum) that join together and produce a larva. The larva then grows, forming a new individual. Some species perform alternating reproduction, which includes both asexual and sexual reproduction.

Flatworms and Nematodes

• Asexual Reproduction: This is only performed by flatworms. They split into several pieces (scission), and each piece regenerates the missing parts to form new individuals.
• Sexual Reproduction: This requires two individuals of opposite sex. They form sexual cells (sperm and ovum) that join together. Fertilization is usually internal, and then they lay fertilized eggs.

Annelids

• Asexual Reproduction: By scission.
• Sexual Reproduction: Earthworms are hermaphrodites with cross-fertilization. They have both male and female reproductive organs. During sexual intercourse, they align their bodies and exchange sperm. Thus, the eggs of both individuals become fertilized.

Molluscs

They perform sexual reproduction by internal fertilization and are oviparous. Some species, such as snails, are hermaphroditic, but it generally requires two individuals of opposite sex. They form sexual cells (sperm and ovum) that join together. Fertilization is usually internal, and then they lay fertilized eggs.

Echinoderms

• Sexual Reproduction: They perform sexual reproduction with external fertilization. This requires two individuals of opposite sex. They form sexual cells (sperm and ovum) that join together in the water, forming a mobile larva.
• Asexual Reproduction: Starfish also have asexual reproduction by fragmentation. They regenerate the missing parts to form new individuals.