Skin extract from Rhamdia quelen(Siluriformes: Heptapteridae) does not promote stress in conspecifics

Abstract

Chemical communication is widely used in aquatic environments, where visual or auditory signals may not be always effective. Fish of the superorder Ostariophysi are known to display epidermal cells (club cells) that produce and store alarm substances, which are released to the water when the skin is damaged. Responses to alarm substances range widely, between active searches for refuge to a complete stop in any locomotor activity. In this study a large number of binucleated club cells (average density of 11 cells /µm 2 ) were histologically observed in the skin of the catfish Rhamdia quelen (known as jundiá). Skin extract (2, 5, and 10% w/v) applied for 15 minutes to conspecifics elicited increase in swimming activity and in the area visited by the fish inside the tank. However, exposure to the epithelial alarm cue did not evoke any stress response: plasma osmolality, ions (sodium, chloride, magnesium, and potassium), glucose and cortisol remained unchanged. In conclusion, the conspecific alarm cue of the jundiá induces behavioral responses but not an acute stress response upon short-term exposure, compatible with its role in fostering physical integrity without representing major stress activation. Considering that in the natural environment such stimuli must quickly disappear due to dilution and that rapid protection responses may be necessary upon the possibility of an approaching predator, a faster mechanism to assure survival may come into play, such as sympathetic nervous system activation.Comunicação química é amplamente utilizada por animais que vivem em ambiente aquático, onde sinais visuais e auditivos nem sempre são facilmente identificados. Os Ostariophysi são conhecidos por apresentarem células club na epiderme, as quais produzem e estocam substância de alarme que são liberadas para o ambiente quando a pele é lesionada. As respostas dos peixes a substância de alarme variam entre exploração ativa por refúgios até a parada completa de atividade locomotora. Neste estudo, grande número de células club binucleadas (densidade média de 11 células/µm2) foram histologicamente observadas na epiderme do jundiá, Rhamdia quelen. Peixes expostos a extrato de pele de conspecíficos (2, 5, e 10% peso/vol) por 15 minutos apresentaram aumento da atividade locomotora e da área de dispersão. No entanto, essa exposição não promoveu nenhuma resposta de estresse -osmolalidade plasmática, íons (sódio, cloreto, magnésio e potássio), glicose e cortisol não sofreram alteração. Concluímos que a exposição aguda a extrato de pele de conspecíficos promovem respostas comportamentais de fuga, que essa espécie apresenta grande concentração de células club, as quais devem estar envolvidas nessas respostas e que a exposição aguda ao estímulo não promoveu respostas bioquímicas indicativas de estresse. Considerando que no ambiente natural tais estímulos devem desaparecer rapidamente dados a diluição do meio e que respostas rápidas de proteção devem ser desencadeadas frente à possibilidade de presença de predador, vias rápidas de suporte ...

Conspecific and heterospecific alarm substances induce behavioral responses in juvenile catfish Rhamdia quelen

“…Apparently, the silver catfish larvae seek concealment because of their small body size, whereas the juvenile increase their amount of movement probably to avoid predator's odor stimulus. However, when adult silver catfish were exposed to conspecifics alarm cues they remained immobile in the first minutes and then increased swimming activity (Souza-Bastos et al, 2014), as observed in the present study. Furthermore, Rivulus hartii (currently Anablepsoides hartii) and yellow perch also demonstrated significant size-dependent trends in response to heterospecific and conspecific alarm cues, respectively, with smaller individuals exhibiting antipredator responses and larger individuals shifting their behavior to increased levels of activity consistent with a foraging or predatory response (Harvey, Brown, 2004;Elvidge et al, 2010).…”

Conspecific injury raises an alarm in medaka

“…Activation of the primary stress response pathway in reaction to CSE exposure, as seen in medaka, has also been reported in many other species4142435152. There are examples, however, ( Brycon cephalus and Rhamdia quelen ) where conspecific injury elicits an anti-predator behaviour, but cortisol changes are undetectable5354. It is possible that alternate stress response pathways are triggered in some species, or in specific contexts643.…”

Mucosal responses of brown‐marbled grouper Epinephelus fuscoguttatus (Forsskål, 1775) following intraperitoneal infection with Vibrio harveyi

“…Sacciform cells have been described as “alarm cells,” with similar morphology and content as club cells, since the presence of these cells and their secretions is thought to serve as signals to other fish to alert them of danger (Bryer, Mirza, & Chivers, 2001; Commens & Mathis, 1999; Smith, 1992; Souza‐Bastos et al, 2014). Sacciform cells described in the present study are located on the superficial layer of the epidermis and discharge their contents directly on the tissue surface, thus differentiating them from club cells, which are usually present in the middle layers of the epidermis and release their contents upon epidermal injury (Elliott, 2011).…”