Note in the histograms on the near Right that the preferred size of sea-urchin prey for Pycnopodia is 6-8cm test diameter (bottom histogram), suggesting that red urchins larger than this have reached size refuge. The author estimates that it takes about 28h for Pycnopodia to capture, eat, and digest an urchin in this preferred size range.
Anatomy and supply. The palmar interossei are three muscles located in the metacarpus. They arise from the metacarpal bones of the index, ring and little finger. The origin surfaces of these muscles are facing towards the middle finger:1  Palmar interosseous muscle I: ulnar side of the index finger.unctionally, the palmar interossei act antagonistically to the dorsal interossei in the MCP (mnemonic: DAB = Dorsals ABduct, PAD = Palmars ADduct). However both muscle groups perform common functions, as they flex the fingers in the MCP and extend in the proximal and distal interphalangeal joints (PIP and DIP).
The four dorsal interossei muscles connect the joints in your fingers to your palm, help to move your fingers away from your thumb and contribute to moving them toward your palm. The three palmar interossei muscles serve the same functions, but move the fingers toward your thumb.