Evolution & Systematics
Figure 5. Phylogeny tree of the evolutionary relationship of Holothuria hilla with other organisms in the Echinodermata phylum.
Phylum Echinodermata: Echinoderms are marine-dwelling organisms with skeletons which are made of numerous ossicles or calcareous plates. The presence of tube feet and water vascular system are distinctive characteristics for echinoderms (Wray 1999).
Class Holothuroidea: Unlike animals in other classes, they have elongated bodies with leathery skin unlike animals in other classes (Hui 2008).
Order Aspidochirotida: Animals in this order have shield-shaped buccal podia and respiratory trees. They have soft body walls and are flexible (Kerr 2000).
Family Holothuriidae: This family of aspidochirotida has well demarcated body with five rows of tube feet for locomotion on the ventral side. The body wall is usually coated with spiny papillae. In times of danger, most of the members have the ability to either eject cuiverian tubules or eviscerate to distract predators.
Genus Holothuria: All of the animals in this genus have presence of tables in their body wall. Most of them are found on coastal areas such as reef flats and lagoons. |