Innate responses to con- and heterospecific alarm chemicals in juveniles of a freshwater shrimp

ITUARTE R.B.; NUÑEZ J.D.; SPIVAK E.D.; BAS C.C.

JOURNAL OF ZOOLOGY (1987)

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2022

0952-8369

Released substances from injured conspecifics and heterospecifics (alarm chemicals) often trigger inducible defenses (e.g., behavioral, morphological, and life-history antipredator defenses). Although there are good reasons to assume that the detection of damage-release chemicals may be inherited, immediate behaviors to alarm chemicals remain to be assessed in many aquatic taxa. This study examineschanges in locomotor activity in juveniles of a freshwater shrimp, Palaemonargentinus, in response to (1) distilled water; (2) macerated adult conspecifics, and(3) macerated adult heterospecifics (a closely related, non-coexisting species). Wetested three sets of juveniles coming from (1) alarm cues-unexposed mothers (na€ıvejuveniles), (2) mothers exposed to macerated conspecifics, and (3) mothers exposedto macerated heterospecifics. Juveniles were tested for changes in locomotor activ-ity before and after the addition of a corresponding stimulus. Locomotor activity ofna€ıve juveniles decreased in response to con- and heterospecific stimuli, while itdid not change in response to distilled-water controls. Effect size, as Cohen’s dRM(the standard mean difference between the pre- and the post-stimulus period usingthe pooled standard deviation) indicated that the reduction in locomotor activitywas strong in response to conspecific stimulus (dRM = 1.521), but it was moder-ate in response to heterospecific stimulus (dRM = 0.682). While the responses ofna€ıve juveniles indicate an innate recognition of alarm substances, the responses toheterospecifics likely arise from the recognition of chemicals with a molecularstructure partly conserved between related species, as predicted by the phylogeneticrelatedness hypothesis. Furthermore, juveniles from treated mothers behaved differ-ently than the na€ıve ones, suggesting that juvenile behavioral traits were modifiedthrough embryonic experience. As the embryonic exposure to alarm cues occursduring embryogenesis, we assume that the mothers have perceived these cues also,which might have caused part of the observed developmental effects.