Cyrba algerina is a salticid (Salticidae) spider that lives on the undersides of stones. Two populations were studied, Sintra and Algarve (Portugal), and shown to have similar phenology but different dominant prey. Life cycle in the laboratory was similar for the two populations, but Sintra matured at larger size than Algarve individuals, with these differences potentially having a genetic basis. Sintra individuals used prey-specific prey-capture behaviour against allopatric (Oecobius amboseli) and sympatric (O. machadoi, Trachyzelotes bardiae) spider and insect (bristletails) species. In contrast, Algarve C. algerina only adopted specialised capture behaviour against bristletails. Sintra, but not Algarve, individuals responded to the odour of O. machadoi and T. bardiae, and showed preference for T. bardiae over O. machadoi. Interpopulation variation in the use of specific prey-capture behaviour and in sensitivity to odour cues from prey is directly related to the prey available to individuals from each population, suggesting local adaptation to local prey. Preference for oecobiids seems to be controlled by an experiencetriggered developmental switch. The optics and histology of C. algerina’s principal eye suggest that living in a microhabitat with dim ambient light has favoured sensitivity at the expense of spatial acuity. Short focal length, reduced power of the eye’s diverging lens, and wide, contiguous rhabdomeres, seem to minimise the visual constraints imposed by the low light levels in C. algerina’s microhabitat. While relying solely on vision, C. algerina can detect, identify and capture prey in dim-light conditions under which other salticids perform poorly. C. algerina’s behaviour suggest use of temporal summation to improve its visual performance in dim light.

Cyrba algerina is a salticid (Salticidae) spider that lives on the undersides of stones. Two populations were studied, Sintra and Algarve (Portugal), and shown to have similar phenology but different dominant prey. Life cycle in the laboratory was similar for the two populations, but Sintra matured at larger size than Algarve individuals, with these differences potentially having a genetic basis. Sintra individuals used prey-specific prey-capture behaviour against allopatric (Oecobius amboseli) and sympatric (O. machadoi, Trachyzelotes bardiae) spider and insect (bristletails) species. In contrast, Algarve C. algerina only adopted specialised capture behaviour against bristletails. Sintra, but not Algarve, individuals responded to the odour of O. machadoi and T. bardiae, and showed preference for T. bardiae over O. machadoi. Interpopulation variation in the use of specific prey-capture behaviour and in sensitivity to odour cues from prey is directly related to the prey available to individuals from each population, suggesting local adaptation to local prey. Preference for oecobiids seems to be controlled by an experiencetriggered developmental switch. The optics and histology of C. algerina’s principal eye suggest that living in a microhabitat with dim ambient light has favoured sensitivity at the expense of spatial acuity. Short focal length, reduced power of the eye’s diverging lens, and wide, contiguous rhabdomeres, seem to minimise the visual constraints imposed by the low light levels in C. algerina’s microhabitat. While relying solely on vision, C. algerina can detect, identify and capture prey in dim-light conditions under which other salticids perform poorly. C. algerina’s behaviour suggest use of temporal summation to improve its visual performance in dim light.

Originalmente, a teoria de nicho ecológico fundamenta-se em indivíduos de uma espécie sendo ecologicamente equivalentes por utilizarem os recursos de forma similar. Portanto, o nicho de uma espécie é definido em termos do uso médio de recursos. Porém, a qualidade e abundância de recursos consumidos, sexo, idade ou morfotipo do consumidor influenciam o comportamento alimentar individual. Estudos recentes sobre forrageamento ótimo tem foco de interesse na variação interindividual no uso de recursos. Ao longo da sua área de distribuição são reconhecidas populações da toninha Pontoporia blainvillei (Cetacea) e no litoral paulista, possivelmente hajam três subpopulações dessa espécie: norte, centro e sul. Meu primeiro objetivo foi investigar se há variação na dieta entre essas três subpopulações de toninha. Adicionalmente, investiguei quais fatores entre sazonalidade, sexo e idade dos indivíduos poderiam estruturar a dieta em uma dessas subpopulações (central). Utilizei 58 indivíduos provenientes de captura acidental no litoral paulista, com representantes das regiões norte, centro e sul. A amostra incluiu juvenis e adultos de ambos os sexos, capturados em todas as estações do ano. Identifiquei as espécies nos conteúdos estomacais usando os otólitos de peixes e os bicos de lulas. Estimei o tamanho das presas utilizando regressões com as medidas dessas estruturas e investiguei a estruturação da dieta usando um índice de variação da dieta. Houve uma clara variação na dieta ente as subpopulações paulistas, possivelmente devido à diferença espacial na disponibilidade de presas. Para a subpopulação central não houve variação na dieta decorrente da sazonalidade ou do sexo. A ausência de variação sazonal pode ser devido à pouca alteração na abundância da principal presa, P. harroweri, no ambiente ao longo do ano. A ausência de variação decorrente do sexo pode ser devido a seleção de presa estar mais relacionada a características de corpo mole e fácil digestão e não ao tamanho da presa, sendo essa seleção comum para ambos os sexos. Indivíduos de idades diferentes possuem dietas distintas, com juvenis consumindo mais espécies que os adultos. Essa mudança de nicho alimentar pode ser devida ao período de aprendizado. Finalmente, mesmo descontando os efeitos da disponibilidade temporal e espacial de presas, do sexo e da idade, houve variação interindividual da dieta na subpopulação central. Somente estudos com marcadores isotópicos poderão investigar se essa variação é devida à especialização individual em toninhas / Ecological niche theory is originally based on the assumption that individuals of a species use similar resources and therefore are ecologically equivalents. Under this framework, the niche of the species can be defined in terms of average resource use. However, factors such as quality and quantity of prey resources in the environment, consumer gender, age or morphotype may influence the individual feeding behavior. Considering that possible interindividual variation, recently studies under optimal foraging theory have variation among individuals as a focus of interest. The species P. blainvillei is partionated in populations along its range and probably, subpopulations can be found in the Sao Paulo state coast: northern, central and southern. Hence, my first goal was to investigate if there is diet variation among the three franciscana subpopulations from Sao Paulo coast. Additionally, I searched for which factors would be the diet structure defined within one of the subpopulations (the central one). I have considered the seasonality, individual gender and sex as possible factors influencing the diet structure within the central subpopulation. I had 58 franciscana specimens obtained from bycatch in the Sao Paulo coast, being them from northern, central and southern regions. They were juveniles and adults of both genders and bycaught in all the seasons. I identified the prey species from the gut contents with fish otholits and squid beaks. I estimated prey length and weight using regressions with that structures measures and I investigated the diet structure using a diet variation index. Within the central subpopulation I found no diet variation based on seasonality or individual gender, instead I found diet variation for individuals from different ages. Probably, most of the diet variation among subpopulations is due to prey availability spatial difference. The lack of diet variation based on seasonality may be due to little seasonal variation in the abundance of the main prey, P. harroweri. The lack of variation due to gender is probably related to the prey selection on soft body and easy digestion instead of prey size, being this type of selection common for both genders. Juveniles franciscana preyed on more species than the adults and that niche shift as an age effect can be consequence of forraging skills development. Enclosing, even discarding the effects of the spacial and temporal prey availability, individual gender and age, I found interindividual-level diet variation within the central subpopulation, which can points out to franciscana individual specialization, but isotopic studies are required to infer that specialization

Originalmente, a teoria de nicho ecológico fundamenta-se em indivíduos de uma espécie sendo ecologicamente equivalentes por utilizarem os recursos de forma similar. Portanto, o nicho de uma espécie é definido em termos do uso médio de recursos. Porém, a qualidade e abundância de recursos consumidos, sexo, idade ou morfotipo do consumidor influenciam o comportamento alimentar individual. Estudos recentes sobre forrageamento ótimo tem foco de interesse na variação interindividual no uso de recursos. Ao longo da sua área de distribuição são reconhecidas populações da toninha Pontoporia blainvillei (Cetacea) e no litoral paulista, possivelmente hajam três subpopulações dessa espécie: norte, centro e sul. Meu primeiro objetivo foi investigar se há variação na dieta entre essas três subpopulações de toninha. Adicionalmente, investiguei quais fatores entre sazonalidade, sexo e idade dos indivíduos poderiam estruturar a dieta em uma dessas subpopulações (central). Utilizei 58 indivíduos provenientes de captura acidental no litoral paulista, com representantes das regiões norte, centro e sul. A amostra incluiu juvenis e adultos de ambos os sexos, capturados em todas as estações do ano. Identifiquei as espécies nos conteúdos estomacais usando os otólitos de peixes e os bicos de lulas. Estimei o tamanho das presas utilizando regressões com as medidas dessas estruturas e investiguei a estruturação da dieta usando um índice de variação da dieta. Houve uma clara variação na dieta ente as subpopulações paulistas, possivelmente devido à diferença espacial na disponibilidade de presas. Para a subpopulação central não houve variação na dieta decorrente da sazonalidade ou do sexo. A ausência de variação sazonal pode ser devido à pouca alteração na abundância da principal presa, P. harroweri, no ambiente ao longo do ano. A ausência de variação decorrente do sexo pode ser devido a seleção de presa estar mais relacionada a características de corpo mole e fácil digestão e não ao tamanho da presa, sendo essa seleção comum para ambos os sexos. Indivíduos de idades diferentes possuem dietas distintas, com juvenis consumindo mais espécies que os adultos. Essa mudança de nicho alimentar pode ser devida ao período de aprendizado. Finalmente, mesmo descontando os efeitos da disponibilidade temporal e espacial de presas, do sexo e da idade, houve variação interindividual da dieta na subpopulação central. Somente estudos com marcadores isotópicos poderão investigar se essa variação é devida à especialização individual em toninhas / Ecological niche theory is originally based on the assumption that individuals of a species use similar resources and therefore are ecologically equivalents. Under this framework, the niche of the species can be defined in terms of average resource use. However, factors such as quality and quantity of prey resources in the environment, consumer gender, age or morphotype may influence the individual feeding behavior. Considering that possible interindividual variation, recently studies under optimal foraging theory have variation among individuals as a focus of interest. The species P. blainvillei is partionated in populations along its range and probably, subpopulations can be found in the Sao Paulo state coast: northern, central and southern. Hence, my first goal was to investigate if there is diet variation among the three franciscana subpopulations from Sao Paulo coast. Additionally, I searched for which factors would be the diet structure defined within one of the subpopulations (the central one). I have considered the seasonality, individual gender and sex as possible factors influencing the diet structure within the central subpopulation. I had 58 franciscana specimens obtained from bycatch in the Sao Paulo coast, being them from northern, central and southern regions. They were juveniles and adults of both genders and bycaught in all the seasons. I identified the prey species from the gut contents with fish otholits and squid beaks. I estimated prey length and weight using regressions with that structures measures and I investigated the diet structure using a diet variation index. Within the central subpopulation I found no diet variation based on seasonality or individual gender, instead I found diet variation for individuals from different ages. Probably, most of the diet variation among subpopulations is due to prey availability spatial difference. The lack of diet variation based on seasonality may be due to little seasonal variation in the abundance of the main prey, P. harroweri. The lack of variation due to gender is probably related to the prey selection on soft body and easy digestion instead of prey size, being this type of selection common for both genders. Juveniles franciscana preyed on more species than the adults and that niche shift as an age effect can be consequence of forraging skills development. Enclosing, even discarding the effects of the spacial and temporal prey availability, individual gender and age, I found interindividual-level diet variation within the central subpopulation, which can points out to franciscana individual specialization, but isotopic studies are required to infer that specialization