Dipleurula

Dipleurula

A diagram of a Dipleurula larva

The Dipleurula is a type of larva that is commonly found in the development of certain marine invertebrates, particularly within the phylum Echinodermata. It is characterized by its bilateral symmetry and ciliated bands, which aid in locomotion and feeding. The name "Dipleurula" is derived from the Greek words "di" meaning two, "pleura" meaning side, and "ula" meaning small, referring to its two-sided body structure.

Anatomy

The Dipleurula larva typically has a pear-shaped body with two distinct sides. It possesses a well-defined anterior-posterior axis, with the anterior end being slightly narrower than the posterior end. The larva is covered in cilia, which are hair-like structures that help in movement and feeding. These cilia create a characteristic banding pattern along the body, allowing the larva to swim and capture food particles.

Development

The development of a Dipleurula larva begins with the fertilization of an egg. After fertilization, the zygote undergoes several cell divisions, forming a hollow ball of cells called a blastula. The blastula then undergoes gastrulation, a process in which the cells rearrange and differentiate to form distinct germ layers.

During gastrulation, the blastula invaginates, forming a structure known as the archenteron. The archenteron eventually develops into the larval gut. As the development progresses, the larva elongates and acquires its characteristic bilateral symmetry. The ciliated bands also start to form, aiding in the larva's locomotion and feeding.

Role in Echinoderm Development

The Dipleurula larva plays a crucial role in the development of echinoderms, a diverse group of marine invertebrates that includes starfish, sea urchins, and sea cucumbers. After the Dipleurula stage, the larva undergoes metamorphosis, transforming into the adult form of the respective echinoderm species.

The Dipleurula larva serves as a dispersal stage, allowing the larvae to move away from their parent organisms and colonize new areas. It also provides an opportunity for genetic mixing and adaptation to different environmental conditions. The larva feeds on planktonic organisms, contributing to the transfer of energy within marine ecosystems.

Importance in Evolutionary Biology

The study of Dipleurula larvae has provided valuable insights into the evolutionary relationships among different animal phyla. The presence of similar larval forms across various phyla suggests a common ancestry and shared developmental pathways.

The Dipleurula larva is believed to represent an ancestral form that gave rise to the diverse body plans seen in echinoderms and other related phyla. By studying the development and morphology of Dipleurula larvae, scientists can gain a better understanding of the evolutionary processes that have shaped the animal kingdom.

See Also

• Echinodermata
• Metamorphosis
• Gastrulation