Acute exposure to the conspecific alarm substance and its intergenerational consequences in Astyanax bimaculatus...

The conspecific alarm substance (CAS), a chemical compound likely based on glycosaminoglycans, purines, and nitrogen oxide-based pterins, is a natural stressor released by specialized epidermal cells damaged by injury or attack in fish, inducing hormonal and behavioral changes in conspecifics. Its effects in the reproductive context are poorly understood, but previous studies have demonstrated earlier spawning in broodstock exposed to CAS and an influence on the larval length of the offspring, potentially linked to increased cortisol transfer. In this study, 53 sexually mature specimens of Astyanax bimaculatus (18 males and 35 females) were exposed to CAS for 6 min, before hormonal induction by intraperitoneal injection of carp pituitary extract solution. The CAS substance was extracted by injuring the skin of donor conspecific animals, by superficial cuts of the epidermis, using scissors. After hormonal induction, the animals were paired for courtship. Following semi-natural reproduction, we assessed spawning time, embryonic development, hatching rate, larval anomalies in the first 18 h, initial larval linear morphometry in the first 72 h, and offspring survival for 7 days. The exposed animals spawned 1 h earlier than the non-exposed breeders. Despite this, embryonic development, hatching rate, larval anomalies, and survival were similar for the offspring resulted from the exposed and non-exposed groups, and the offspring of stressed breeders showed significantly shorter total length, improved cephalic development, a thicker dorsal muscle region, and greater yolk consumption 48 h after hatching. The scarcity of research on the physiological consequences of CAS on fish reproduction limits the interpretation of intergenerational findings. The precocity of gamete release suggests CAS as a potential trigger of reproduction in the species, but the results in the progeny remain inconclusive. Further studies, including endocrine assessments, are needed to confirm or refute the intergenerational patterns induced by CAS.