PLASTICITY OF EXTERNAL SETAE DURING CLAW TRANSFORMATION IN THE SNAPPING SHRIMP, ALPHEUS ANGULOSUS MCCLURE, 2002 (DECAPODA, CARIDEA)

The snapping shrimp, Alpheus angulosus McClure, 2002, is a small crustacean with bilaterally asymmetric claws that serve distinct behavioural and sensory functions. If the large claw is lost, the organism switches handedness, transforming its small pincer claw into a large snapping claw while simultaneously developing a small claw on the contralateral side. To better understand the mechanisms required to adapt to this radical change in body composition, we examined developmental plasticity by tracing changes in sensory setae distribution on the claws throughout transformation. We observed only two broad types of setae, simple and plumose. Quantitative analysis across molt stages revealed significant alterations in setae composition and numbers that occurred primarily on the edge of the propodus, where the most drastic morphological changes also occur. These results suggest that previous developmental mechanisms are re-engaged to support the proliferation and differentiation of new setae during transformation.