Collector Urchins, Tripneustes gratilla
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Description & Behavior
One of the "prettiest" sea urchins is Tripneustes gratilla (Linnaeus, 1758), which are commonly known as collector, cake or Parson's hat sea urchins. Other common names include Halloween urchins, Hawaiian sea urchins, priest-hut urchins, pincushion, pin-cushion or hairy sea urchins and their names mainly come from their habit of collecting debris in their spines. T. gratilla has many different color morphs that vary throughout the visible color spectrum (the most morphs of all the 700 or so sea urchin species). Mature or adult collector sea urchins have test (body shell) diameters of between 10-15 centimeters. These urchins are typically found at a minimum depth of two meters down to thirty meters or more. T. gratilla is venomous but doesn't inflict the severe stings like flower urchins (Toxopneustes pileolus). The main predators of T. gratilla are pufferfishes, octopuses, and humans.
World Range & Habitat
T. gratillaiare are known to live in a of range of tropical habitats, including coral reefs, sea grass meadows, macroalgae forests and on bare sediments.
Currently T. gratillai is found mainly off Australia and its surrounding islands, collectively know as Oceania. They are very common on the Great Barrier Reef. They are also found in the Northern and Western parts of the Indian Ocean as well as in the Red Sea. They are usually found in sheltered and moderately exposed reefs.
Feeding Behavior (Ecology)
Collector urchins are normally found feeding on a variety of seagrasses (such as Thalassodendron ciliatum and Syringodim isoetifolium), epibenthic micro and macroalgaes, and various detritus. Unlike most, these urchins graze around the clock, while most usually graze during the day or night only. T. gratillai also grazes on coralline algae when kelp is not available as a food source. Sea urchins have a chewing organ formerly called the “Aristotle's Lantern” which consists of five self-sharpening teeth and the muscles that intertwine with those teeth.
These urchins spawn once a year. Annually they spawn during the winter or the cooler months of the year and each clutch consists of approximately 2 million eggs. The eggs meet the male's sperm in the water column, where they develop. The fertilized eggs develop into pluteus larvae, which then remain in the water column for approximately a month. They then settle to the sea floor and undergo metamorphosis and become juveniles. The urchins then take about two to five years to become a reproducing adult.
Conservation Status & Comments
In 1993 the Bolinao Marine Laboratory of the University of the Philippines Marine Science Institute opened a T. gratilla hatchery at the reef flats of Bolinao, Pangasinan. Their goal was to take the pressure off of the wild stock. Each year the hatchery would produce roughly 40,000 collector urchins. Most of the sea urchins were then used to reseed protected areas and allow the population to increase.
References & Further Research
Research Tripneustes gratilla » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS
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