Meeting Abstract

P3.35  Tuesday, Jan. 6  Muscle mechanics in mantis shrimp MENDOZA BLANCO, M/A*; PATEK, S/N; Univ. of California, Berkeley; Univ. of California, Berkeley marco_mendoza@berkeley.edu

Mantis shrimp (Stomatopoda) capture a wide range of prey depending on the particular morphology of their thoracic appendages. Smasher mantis shrimp have hammer-like appendages used to deliver powerful blows while spearers have elongated, spiny appendages for piercing or grabbing prey. The lateral extensor muscle powers these strikes and occupies up to 90% of the muscle weight inside the merus segment. The extensor muscle compresses springs and linkages which are then rapidly released by latches controlled by flexor muscles. One fundamental question in this system is whether the lateral extensor muscle limits strike performance across species, given the dramatic variation in feeding strategies. Our goal was to compare the physiological cross-sectional area (PCSA) of the lateral extensor muscle in the raptorial appendage of a smasher (Gonodactylaceus falcatus) and a spearer (Pseudosquilla ciliata) and to examine body size scaling in PCSA within these two species. PCSA was calculated by measuring the apodeme area and the mean pinnation angle of the lateral extensor muscle. The pinnation angle was similar in both species (37-38) and it did not vary across a nearly two-fold range of body lengths in each species. The relationship between PCSA, apodeme area and merus length were indistinguishable between the two species. PCSA and apodeme area were positively correlated with body size in P. ciliata and approached significance in G. falcatus. Interestingly, the merus was larger relative to body size in the smasher, G. falcatus, than in the spearer, P. ciliata, resulting in a gradeshift in all parameters relative to body size except for pinnation angle. Thus, the smasher has larger appendages and greater PCSA than in a similar-sized spearer, but the muscle mechanics remain similar across appendage sizes in these two species.