Meeting Abstract

P1.86  Friday, Jan. 4  Functional morphology in chitons (Polyplacophora): influences of environment and ocean acidification GREEN, P.A.*; CROFTS, S.; SIGWART, J.D.; Univ. Massachusetts, Amherst; Univ. Washington, Seattle; Queen’s Univ. Belfast, Marine Station pagreen@bio.umass.edu

Polyplacophoran molluscs show low morphological diversity compared to other marine invertebrates, yet chitons are important algal foragers that occupy distinct ecological niches. We investigated potential functional correlates of niche separation in three species of co-occurring mopallid chitons that have total ranges across differing environments (Mopalia muscosa, Mopalia lignosa, Katharina tunicata). We measured force required to fracture the protective valves of each species, and found significant variation between species. Katharina tunicata, considered to have “reduced” valves, is more fracture resistant than the two Mopalia species (mean K. tunicata = 31.5 N; mean M. muscosa = 22.6 N; mean M. lignosa = 13.9 N; F(2,30)=27.0, p<<0.01). Terminal valves in Mopalia spp. are significantly more fracture resistant than intermediate valves (F(1,370)=164.0, p<0.01), while all valves in K. tunicata appear to be functionally equivalent. To see if future pCO₂ changes predicted under ocean acidification (OA) will affect species differently, we measured the change in force to fracture valves after 10 days of exposure to raised pCO₂ (Control = 8.0pH [374.52+/-110.9 pCO₂], Raised = 7.5pH [1507.77+/-163.10 pCO₂). Although previous experimental OA work found significant impacts on mollusc shells over similar timescales, we saw no consistent reduction in total fracture resistance related to treatment in acidified water. Our data demonstrate functional implications of diversity in chiton valve morphologies, and show that physical changes in local topology and wave exposure may have stronger impacts on chitons than changes in ocean chemistry under future climate change.