Reproductive traits of Gnathophylloides mineri Schmitt, 1933, a minute ectosymbiotic shrimp associated with the sea urchin Tripneustes ventricosus

Abstract Numerous studies on the reproduction of decapods have revealed that the female energy investment in embryo production is generally around 10% of the female weight. In decapods living together with other organisms, however, the reproductive output (RO) may be substantially higher. Here we tested the hypothesis that decapods living in association with other organisms allocate more energy in embryo production than free-living ones. We studied the shrimp Gnathophylloides mineri , which lives among the spines of the sea urchin Tripneustes ventricosus . Shrimps were collected between October 2011 and April 2013 along the southern Caribbean coast of Costa Rica. A total of 45 ovigerous females were analyzed; female size ranged from 1.44 to 2.14 mm carapace length. Females carried on average 37 ± 16 SD embryos. The embryo volume increased during the incubation period by 200% (from 0.04 ± 0.01 to 0.08 ± 0.01 mm 3 , mean ± SD). The RO was not related to female size, and comprised on average 27.5 ± 16.0 SD % of the dry weight of the females. In summary, G. mineri produces few and small embryos, but these embryos are relatively large when compared to similar-sized caridean species. Moreover, RO of this ectosymbiotic species was higher than in free-living species, but lower than in endosymbiotic decapods. These results support the hypothesis that energy investment in embryo production of decapods increases with the level of protection associated with the symbiosis.