Spatangoida

Spatangus purpureus rob

Brissus latecarinatus

Eupatagus mooreanus fossil heart urchin (Eocene; Florida, USA) 1 (16765728703)

Echinocardium cordatum

Phrissocystis

Tiny maretia heart urchin (Maretia planulata)

Spatangoida is an order within the class Echinoidea, which comprises a group of sea urchins known as heart urchins due to their distinct heart-shaped form. This shape is an adaptation to their burrowing lifestyle. Spatangoida diverges significantly from the typical spherical shape associated with sea urchins, showcasing a more flattened body that aids in their movement through sandy and muddy substrates of the ocean floor.

Description

Spatangoida species possess a bilateral symmetry, which is a departure from the radial symmetry seen in many other echinoderms. Their bodies are covered with small spines that are used for locomotion and burrowing into the substrate. The mouth of a Spatangoid is located on the underside of the body, while the anus is positioned towards the rear end, facilitating the expulsion of waste without disturbing the sediment in front of them as they burrow.

Habitat and Distribution

Members of the Spatangoida order are predominantly found in marine environments across the globe, from shallow coastal waters to the deep sea. They prefer sandy or muddy bottoms where they can easily burrow. Their distribution is widespread, with species found in every ocean, from the tropics to the cold waters of the Arctic and Antarctic.

Ecology

Spatangoida play a significant role in the benthic ecosystem. As burrowers, they are important bioturbators, meaning they significantly disturb the sea floor sediment, which in turn affects nutrient cycling and the distribution of other marine organisms. Their diet primarily consists of organic matter found within the sediment, which they ingest as they burrow.

Evolution and Classification

The order Spatangoida is part of the phylum Echinodermata, which includes other marine organisms such as starfish, sea cucumbers, and crinoids. The evolutionary history of Spatangoida is marked by a significant diversification event during the Mesozoic era, which is well documented in the fossil record. This diversification has led to the wide variety of forms seen in contemporary species.

Conservation

While many species within the Spatangoida order are not currently considered to be at risk, their dependence on specific sediment types makes them vulnerable to habitat destruction and pollution. Coastal development, dredging, and sedimentation from human activities can significantly impact their habitats.

Research and Importance

Research on Spatangoida contributes to our understanding of evolutionary biology, marine ecology, and the impacts of climate change on marine ecosystems. Their unique burrowing behavior and physiological adaptations offer insights into the evolutionary pathways that have allowed echinoderms to colonize a variety of marine habitats.

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