Anatomical reorganization within the hand and forelimb of Perodicticus potto

Abstract

Historical behavioral accounts note extraordinarily high grip strength in Perodicticus potto. Anatomical analysis of the potto’s hand and forelimb reveal several specializations that may facilitate this enhanced gripping ability, including a specialized vascular bundle (the retia mirabilia) within the wrist, a hyper‐abducted pollex, and a highly reduced second digit. The myological correlates of grip strength (i.e., the contractile potential of the hand and wrist musculature) of P. potto, however, have yet to be quantitatively evaluated. The current study contrasts the myology of the hand and forearm muscles within P. potto to a series of closely‐related strepsirrhines (Nycticebus coucang, Otolemur crassicaudatus, Hapalemur griseus, and Eulemur mongoz), as well as comparing the forearm musculature to a broader (n= 41) primate sample. Despite reports of the potto’s high grip strength, our findings demonstrate relatively below‐average force capacity (relatively low physiological cross‐sectional area) within the digital flexors of this species, which suggests that the gripping ability of this species may be less extraordinary than previously hypothesized. In addition to this observation, we report a number of unusual myological features within the potto, including the largest brachioradialis (an elbow flexor) of any taxon within our sample. Even more surprisingly, we identified an independent extensor indicis within P. potto, despite the vestigial nature of the second digit, and the absence of this muscle within ~25% of other taxa within our sample ‐ all of which possessed a more substantial second digit than the potto. These data underscore the curious nature of the potto’s antebrachial musculature, but suggest that adaptations within the potto’s forelimb may be more related to maximizing endurance grip potential than towards increasing myological force.Support or Funding InformationNational Science Foundation (IOS‐15‐57125 and BCS‐14‐40599)