Tossup

A species of these organisms that act as pests in one ecosystem are injected with bile salts using autonomous drones like RangerBot. A relaxin-like peptide hormone found in these organisms called “gonad-stimulating substance” makes them a useful model to study oocyte maturation. They aren’t deer, but two recent studies have disproved the theory that the densovirus SSaDV caused a mysterious “wasting disease” in these organisms. (-5[2])The Triton Snail is one of the few natural predators capable of containing outbreaks of a corallivorous type of these animals in the genus Acanthaster. Studying the purple Pisaster (10[2])genus of these animals (10[1])in rocky intertidal ecosystems led Robert Paine to coin the term “keystone species.” For 10 points, what echinoderms are named for having five arms? (10[1])■END■ (10[1])

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