Meeting Abstract

1.3  Sunday, Jan. 4 08:30  Plasticity in development associated with sociality in spiders: What factors influence developmental patterns in spiders? CARDILLO, MG*; RAYOR, LS; Cornell University, Ithaca, NY; Cornell University, Ithaca, NY mgc63@cornell.edu

Spiders remain in the egg sac as 1^st instars and emerge as 2^nd instars, which soon begin to hunt for prey. This ‘universal’ pattern of spider development is seen in 26 solitary Australian huntsman species (Sparassidae: Deleninae). However, the three known social huntsman species exhibit a different pattern of development, such that 2^nd instars of the social species, Delena cancerides and D. lapidicola, are non-feeding and retain 1^st instar characteristics: shorter legs and more abdominal yolk. Only in the 3^nd instar do social species morphologically resemble adult huntsman spiders and begin to hunt. We examined differences in physiological variables to determine which factors account for the developmental differences between two social and four solitary huntsman spider species. We measured the number, volume, and mass of social and solitary spider eggs and spectrophotometrically measured differences in protein, lipid, and carbohydrate content of yolk. Standard metabolic rates of 1^st, 2^nd, and 3^rd instar spiders were measured using stop-flow respirometry, along with the number of days spent in egg, 1^st, 2^nd, and 3^rd instar stages. To see whether the delayed developmental pattern of social species gives them an advantage in growth, we measured changes in leg length, carapace width, and abdomen volume. Our results indicate that social species have more egg yolk, shorter developmental periods, and lower metabolic rates, enabling them to remain non-feeding as 2^nd instars and giving them an advantage in leg length growth from 2^nd to 3^rd instar. Similar delayed developmental patterns and physiological adaptations may be found in other social carnivores that must overcome similar barriers to group living.