Responses of the black sea urchin Tetrapygus niger to its sea-star predators Heliaster helianthus and Meyenaster gelatinosus under field conditions

Sea urchin Tetrapygus niger distribution on elevated surfaces represents a strategy for avoiding predatory sea stars

“…In contrast H. heli anthus is a generalist feeder that most frequently consumes mussels, barnacles and small gastropods (Barahona & Navarrete 2010). Responses of T. niger to the 2 sea star species provide further evidence that M. gelatinosus represents a stronger threat than H. helianthus; the urchin severs contact faster with M. gelatinosus than with H. helianthus when subjected to simulated attacks, and the urchin detects M. gelatinosus at greater distances than H. helianthus (Urriago et al 2011).…”

“…On all 3 types of bottoms, the urchins first responded to simulated attacks by raising their spines, and then moved away in the opposite direction to the point of contact with the predator (these responses are described in greater detail in Urriago et al 2011). The time for the urchins to sever contact with the sea stars did not vary with the sea star predator (Heliaster helianthus or Meyenaster gelatinosus) but varied with the type of bottom (p < 0.0001; Fig.…”

“…Under laboratory conditions, the urchin increased its rate of displacement in the presence of M. gelatinosus or the predatory fish Pinguipes chilensis and a higher proportion of individuals responded in trials with M. gelatinosus (92%) than with P. chilensis (67%) (Rodriguez & Ojeda 1998). Finally, Urriago et al (2011) showed that the urchin could differentiate between predatory (Heliaster helianthus and M. gelatinosus) and non-predatory (Stichaster striatus) sea stars, could distinguish between different threat levels associated with predatory sea stars and could detect predatory sea stars at a distance. They indicated that M. gelatinosus presented a stronger predatory threat to urchins than H. helianthus.…”

Covering behavior of deep-water echinoids in Antarctica: possible response to predatory king crabs

“…In nearshore, shallow waters of tropical and temperate regions, predators of echinoids include fish (McClanahan & Shafir 1990, Sala & Zabala 1996, spiny lobsters (Tegner & Levin 1983), crabs (Scheibling & Hamm 1991, Agatsuma 2001, Gudimov et al 2003, sea stars (Urriago et al 2011), and sea otters (Estes & Palmisano 1974). In the Southern Ocean, however, there are few durophagous (skeletonbreaking) predators (Aronson et al 2007(Aronson et al , 2015.…”

“…Mann et al (1984) established that echinoids are able to detect water-borne cues from predatory crabs and respond by changing their behavior. Additionally, Urriago et al (2011) demonstrated that echinoids are able to differentiate between species of predatory seastars using distance chemodetection and respond according to the risk of predation. Although manipulative inclusion/exclusion experiments would be necessary to demonstrate causality, chemodetection of lithodids could be responsible for the increased incidence of echinoid covering at deeper depths, coincident with the greater abundance of king crabs.…”