Evidence of an alarm signal in Ophiuroidea (Echinodermata)

• Published in: Marine biodiversity records Vol. 2
• Main Authors: Majer, Alessandra Pereira, Trigo, José Roberto, Duarte, Luiz Francisco Lembo
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.05.2009
• Subjects: Animal communication; Biochemistry; Habitats; Marine biology; Predation; Amphipholis squamata; Ophiothrix angulata; Ophionereis reticulata; Ophiactis savignyi; damage-released alarm signal
• ISSN: 1755-2672; 1755-2672
• DOI: 10.1017/S1755267209001067

Numerous marine species are able to assess predation risk through chemical signals, and this capacity is usually found among animals that experience intense predation and possess chemoreception ability, such as brittle stars. We investigated the occurrence of chemical alarm signals and responses in four species of brittle stars: Amphipholis squamata, Ophionereis reticulata, Ophiactis savignyi and Ophiothrix angulata. Additionally, the effect of microhabitat on alarm-signal recognition was tested for O. savignyi. Brittle-star homogenate was released above individuals in an aquarium, and the duration of their immediate escape response was noted and compared to the control. The broadest recognition was observed for A. squamata, which showed an escape reaction to the damage-released stimuli of all brittle stars tested. Similarly broad recognition was observed for individuals of O. savignyi that were collected from the same algal species occupied by A. squamata, a microhabitat where these individuals co-occurred with each other and with juveniles of O. angulata. The similar size and habit of these species probably expose them to the same predators, and therefore, the alarm signal of one species represents a real risk of predation to the others. In contrast, individuals of O. angulata and O. savignyi collected from sponges did not respond to stimuli from either conspecific or heterospecific individuals. The reduction in predation pressure granted by their chemically protected hosts seems to be responsible for this lack of response. The fourth species, O. reticulata, only responded conspecifically. This brittle star is found buried among rubble, and is not observed associated with other organisms; it is known for its cannibalistic and predatory habit.