RESUMO
Imprinting is a specific form of long-term memory of a cue acquired during a sensitive phase of development. To ensure that organisms memorize the right cue, the learning process must happen during a specific short time period, mostly soon after hatching, which should end before irrelevant or misleading signals are encountered. A well-known case of olfactory imprinting in the aquatic environment is that of the anadromous Atlantic and Pacific salmon, which prefer the olfactory cues of natal rivers to which they return after migrating several years in the open ocean. Recent research has shown that olfactory imprinting and olfactory guided navigation in the marine realm are far more common than previously assumed. Here, we present evidence for the involvement of olfactory imprinting in the navigation behaviour of coral reef fish, which prefer their home reef odour over that of other reefs. Two main olfactory imprinting processes can be differentiated: (1) imprinting on environmental cues and (2) imprinting on chemical compounds released by kin, which is based on genetic relatedness among conspecifics. While the first process allows for plasticity, so that organisms can imprint on a variety of chemical signals, the latter seems to be restricted to specific genetically determined kin signals. We focus on the second, elucidating the behavioural and neuronal basis of the imprinting process on kin cues using larval zebrafish (Danio rerio) as a model. Our data suggest that the process of imprinting is not confined to the central nervous system but also triggers some changes in the olfactory epithelium.
Assuntos
Peixes/fisiologia , Fixação Psicológica Instintiva , Reconhecimento Psicológico , Olfato , Navegação Espacial , Animais , Recifes de Corais , OdorantesRESUMO
The marine plathyhelminth Macrostomum lignano was recently isolated from Adriatic shore sediments where it experiences a wide variety of environmental challenges, ranging from hypoxia and reoxygenation, feeding on toxic algae, to exposure to anthropogenic contaminants. As multidrug resistance transporters constitute the first line of defense against toxins and toxicants we have studied the presence of such transporters in M. lignano in living animals by applying optical methods and pharmacological inhibitors that had been developed for mammalian cells. Application of the MDR1 inhibitor Verapamil or of the MRP1 inhibitors MK571 or Probenecid increased the intracellular fluorescence of the reporter dyes Fura-2 am, Calcein am, Fluo-3 am in the worms, but did not affect their staining with the dyes Rhodamine B, CMFDA or Ageladine A. The marine sponge alkaloid Ageladine A remained intracellularly trapped for several days in the worms, suggesting that it does not serve as substrate of multidrug resistance exporters. In addition, Ageladine A did not affect multidrug resistance-associated protein (MRP)-mediated dye export from M. lignano or the MRP1-mediated glutathione (GSH) export from cultured rat brain astrocytes. The data obtained demonstrate that life-imaging is a useful tool to address physiological drug export from intact marine transparent flatworms by using multiphoton scanning microscopy.
Assuntos
Corantes/metabolismo , Corantes Fluorescentes/metabolismo , Proteínas Associadas à Resistência a Múltiplos Medicamentos/metabolismo , Platelmintos/metabolismo , Pirróis/metabolismo , Compostos de Anilina/metabolismo , Animais , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Transporte Biológico/efeitos dos fármacos , Transporte Biológico/fisiologia , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Células Cultivadas , Fluoresceínas/metabolismo , Fura-2/análogos & derivados , Fura-2/metabolismo , Glutationa/metabolismo , Probenecid/farmacologia , Ratos , Ratos Wistar , Rodaminas/metabolismo , Verapamil/farmacologia , Xantenos/metabolismoRESUMO
Zebrafish larvae imprint on visual and olfactory cues of their kin on day 5 and 6 postfertilization, respectively. Only imprinted (but not non-imprinted) larvae show strongly activated crypt (and some microvillous) cells demonstrated by pERK levels after subsequent exposure to kin odor. Here, we investigate the olfactory bulb of zebrafish larvae for activated neurons located at the sole glomerulus mdG2 which receives crypt cell input. Imprinted larvae show a significantly increased activation of olfactory bulb cells compared to non-imprinted larvae after exposure to kin odor. Surprisingly, pERK activated Orthopedia-positive cell numbers in the intermediate ventral telencephalic nucleus were higher in non-imprinted, kin odor stimulated larvae compared to control and to kin-odor stimulated imprinted larvae and control. Moreover, DiI tracing experiments in adult zebrafish show a neuronal circuit from crypt/microvillous olfactory sensory neurons via dorsomedial olfactory bulb and intermediate ventral telencephalic nucleus (thus, arguably the teleostean medial amygdala) to tuberal hypothalamus, demonstrating for the first time an accessory olfactory system in teleosts.
Assuntos
Tonsila do Cerebelo/fisiologia , Larva/fisiologia , Bulbo Olfatório/fisiologia , Condutos Olfatórios/fisiologia , Neurônios Receptores Olfatórios/fisiologia , Peixe-Zebra/fisiologia , Tonsila do Cerebelo/anatomia & histologia , Tonsila do Cerebelo/citologia , Animais , Carbocianinas/química , Corantes Fluorescentes/química , Expressão Gênica , Fixação Psicológica Instintiva , Larva/anatomia & histologia , Larva/citologia , Microscopia Confocal , Proteína Quinase 3 Ativada por Mitógeno/genética , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Odorantes/análise , Bulbo Olfatório/anatomia & histologia , Bulbo Olfatório/citologia , Condutos Olfatórios/anatomia & histologia , Condutos Olfatórios/citologia , Neurônios Receptores Olfatórios/ultraestrutura , Fosforilação , Olfato/fisiologia , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Peixe-Zebra/anatomia & histologia , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismoRESUMO
Zebrafish larvae imprint on visual and olfactory kin cues at day 5 and 6 postfertilization, respectively, resulting in kin recognition later in life. Exposure to non-kin cues prevents imprinting and kin recognition. Imprinting depends on MHC class II related signals and only larvae sharing MHC class II alleles can imprint on each other. Here, we analyzed which type of olfactory sensory neuron (OSN) detects kin odor. The single teleost olfactory epithelium harbors ciliated OSNs carrying OR and TAAR gene family receptors (mammals: main olfactory epithelium) and microvillous OSNs with V1R and V2R gene family receptors (mammals: vomeronasal organ). Additionally, teleosts exhibit crypt cells which possess microvilli and cilia. We used the activity marker pERK (phosphorylated extracellular signal regulated kinase) after stimulating 9 day old zebrafish larvae with either non-kin conspecific or food odor. While food odor activated both ciliated and microvillous OSNs, only the latter were activated by conspecific odor, crypt cells showed no activation to both stimuli. Then, we tested imprinted and non-imprinted larvae (full siblings) for kin odor detection. We provide the first direct evidence that crypt cells, and likely a subpopulation of microvillous OSNs, but not ciliated OSNs, play a role in detecting a kin odor related signal.