Two behavioral experiments were performed to test that A. franciscana shows specifi c courtship patterns, which in part, would be governed by semiochemicals released by females. The courtship ethogram, based on 30 adult virgin pairs (1 female v/s 1 male) individually video recorded for 1 hour, revealed that males display four independent activity patterns: 1) approach and touch, 2) swim behind, 3) riding attempt, and 4) riding success. The analysis of the transitions among the observed patterns suggested two ways to achieve riding success, both requiring female touch. In one, males approach and touch females followed by riding attempt (27% probability of occurrence), but if the latter fails, males start over from approach and touch (23% probability of occurrence) to fi nally achieve riding success (19% probability of occurrence). The alternative route is approach and touch, swimming behind (7% probability of occurrence) and riding success (5% probability of occurrence). The role of semiochemicals released from females was assessed by using the polar solution (PS) extracted from water conditioned with 40 adult virgin females. Virgin males were soaked with PS for obtaining pseudo females. Afterwards, we confronted 1 pseudo female, 1 female, or 1 control male to either 1 male or 5 male. In all cases the behavior was recorded for 1 hour (N=10), and the frequencies of occurrence of each courtship patterns were analyzed. The most important results showed that: 1) virgin female and pseudo female elicited the same frequency of response in 1 male in all four courtship patterns (P˃0.05); b) virgin female and pseudo female elicited the same response when tested against 5 males in approach and touch, swim behind and riding attempt (P˃0.05). The fact that in all the cases control male always elicited the lowest frequency value in each courtship patterns, strongly suggests the possible role of sexual semiochemicals in the courtship behavior of A. franciscana. The combination of behavior and chemical cues suggests an elaborate premating recognition. KEYWORDS: ethogram, courtship, Artemia, polar fraction, chemical cue RESUMENSe realizaron dos experimentos conductuales para evaluar que A. franciscana muestra patrones de cortejo específi cos, que en parte, serían gobernados por semioquímicos liberados por hembras. El etograma del cortejo, construido a partir de la grabación individual de 30 parejas adultas vírgenes (1 hembra v/s 1 macho) durante 1 hora, reveló que los machos mostraron cuatro patrones de actividad independientes: 1) acercamiento y toque, 2) nado en retroceso, 3) intento de monta, y 4) éxito de monta. El análisis de las transiciones entre los patrones observados sugirió dos maneras de conseguir una monta exitosa, en ambas el patrón acercamiento y toque fue fundamental. La primera transición consistió en que una vez que los machos se acercan y tocan a las hembras, intentan montar a las hembras (27% de probabilidad de ocurrencia), pero si esto no ocurre los machos comienzan nuevamente a acercarse y tocar a la...

Previous researches have established that the swim speed of some microcrustaceans is infl uenced by chemical compounds emitted by conspecifi cs. We examined the hypothesis that cuticular compounds present on the body surface of A. franciscana, the most widespread member of Artemia genus, play a role in the swim speed of conspecifi c males. The movements (swim) of one male confronted to a sponge soaked with female or male cuticular extract, were recorded during 30 minutes and the swim speed was determined using a behavioral tracking software (Ethovision 3.1, Noldus Technologies). As a control, the movements of one male confronted to a sponge soaked with salty water or with a mixture of the solvents used in the extraction (chloroform-methanol), was recorded. The results showed that cuticular compounds from either female or male increase 1.5 (ca.) times the swim speed of males in comparison with the controls treatments salty water and the solvents. There was no a signifi cant difference between the controls (salty water and chloroform-methanol). Chemical characterization was developed by sterifi cation of the cuticular extracts and analyses by GC-FID and GC-MS. Four saturated fatty acid (myristic acid, palmitic acid, estearic acid, arachidic acid) and fi ve insaturated fatty acids (oleic acid, linoleic acid, linoleic acid 3n3, cis-11-eicosanoic acid, euric acid) were identifi ed. Myristic acid was found in female cuticular extract, but not in male cuticular extract. Results suggest that chemical compounds present in the cuticular surface of A. franciscana females could have an important role in the intra-specifi c recognition in this specie. KEYWORDS:Artemia, swimming speed, cuticular compounds, fatty acids, chemical communication. RESUMENInvestigaciones anteriores han establecido que la velocidad de nado de algunos microcrustáceos se encuentra infl uenciada por compuestos químicos emitidos por conespecífi cos. Nosotros examinamos la hipótesis de que los compuestos cuticulares presentes sobre la superfi cie corporal de A. franciscana, el miembro con mayor distribución mundial del genero Artemia, juega un rol en la velocidad de nado de machos conespecífi cos. Los movimientos nado de un macho confrontado a una esponja empapada con extracto cuticular de una hembra o de un macho, fueron grabados durante 30 minutos y la velocidad de nado fue determinada usando un software de rastreo conductual (Ethovision 3.1, Noldus Technologies). Como control, fueron grabados los movimientos de un macho confrontado a una esponja empapada con agua de mar artifi cial o con una mezcla de los solventes usados en la extracción (cloroformo-metanol). Los resultados mostraron que los compuestos cuticulares tanto de hembras como de machos incrementan 1,5 veces (aproximadamente) la velocidad de nado de los machos, en comparación con los experimentos control donde se uso agua de mar artifi cial y los solventes de la extracción. No hubo diferencias signifi cativas entre los controles (agua de mar artifi cial y cloroformo-metanol). La cara...