Maretia

Maretia is a genus of heart urchins belonging to the family Brissidae. These echinoderms are burrowing organisms typically found in sandy or muddy seabeds. They are characterized by their elongated, heart-shaped test (shell) and posterior truncation. Maretia species exhibit a bilaterally symmetrical appearance superimposed on their basic pentaradial symmetry, an adaptation to their burrowing lifestyle.

The genus is distinguished by the presence of petaloid ambulacra on the aboral surface, although these are less developed compared to other echinoids. The periproct (anus) is located on the posterior end, within the posterior truncation. The peristome (mouth) is located anteriorly. Maretia species are detritivores, feeding on organic matter within the sediment. They play a role in bioturbation, the reworking of marine sediments, which contributes to nutrient cycling and sediment aeration.

Species within the genus Maretia have a widespread geographic distribution, occurring in various marine environments, from shallow coastal waters to deeper ocean basins. Identification of specific Maretia species often relies on subtle differences in the shape and ornamentation of the test, as well as the arrangement of tubercles and spines. Fossil records of Maretia indicate a long evolutionary history.