Dendrochirotida

Lore & Background

Holothurians in this order are characterised by ten to thirty much branched tentacles which are sometimes digitate. They also have ring structures composed of ten calcareous plates circling the pharynx. They have both retractor and introvert muscles which means they can retract the tentacles into the mouth when not feeding. The body wall is either firm with large ossicles or of a soft consistency with few ossicles. In some genera the animals attach themselves to hard surfaces but in others they burrow into soft sediments. Prey is captured by the sticky tentacles and transferred to the mouth. The larvae are lecithotrophic, not feeding on plankton but surviving only on materials already present in the eggs until they settle and become juveniles.

Reader's Guide

Dendrochirotida are an order of sea cucumbers distinguished by their branched tentacles and suspension-feeding lifestyle. Their ability to retract tentacles using retractor and introvert muscles is a key adaptation for protection. The order includes diverse families such as Cucumariidae, Phyllophoridae, and Psolidae, among others. Their body wall varies from firm with large ossicles to soft with few ossicles, reflecting different ecological strategies—some attach to hard surfaces, others burrow into soft sediments. The lecithotrophic larvae, which do not feed on plankton but rely on egg yolk, represent a notable reproductive trait. Examples like Thyonella and Cucumaria illustrate the group's typical morphology. The order's fossil family Monilipsolidae indicates a long evolutionary history. Overall, Dendrochirotida contribute to benthic marine ecosystems as suspension feeders, and their varied forms and behaviors highlight the adaptive diversity within sea cucumbers.

Did You Know?

• Dendrochirotida have ten to thirty much branched tentacles that are sometimes digitate.
• Their larvae are lecithotrophic, surviving on materials in the eggs until settlement.