Ophiuroid soup: The effects of increased temperature on the physiology of four species of brittle stars

Climate Change has caused sea surface temperatures (SST) to increase 0.21°C in the last three decades with current predictions estimating an increase of 2°–3.5° by year 2100. The predicted increases in SST will affect the physiology of many tropical marine organisms which currently live at or near their thermal limits. Responses to increased temperature were monitored in four species of tropical shallow water brittle stars (Echinodermata, Ophiuroidea): Ophiocoma echinata, O. wendti, Ophioderma brevispinum, O. appressum. Whole animal responses were measured as righting response times and oxygen uptake rates. Expression of the chaperone, Heat shock protein 70 (Hsp 70), was used to examine molecular level effects.;Animals were exposed to temperatures ranging between 28°–37°C for approximately one hour. All four species exhibited significantly longer righting times (p=0.000) at 36°/37°C compared to the lower temperatures. Oxygen uptake rates were not significantly affected within a species as temperature increased, but there were species differences due to size; the Ophiocoma spp. were larger than the Ophioderma spp. There was no Hsp 70 detected in any of the tissue samples taken from the animals. Data from righting response and oxygen uptake experiments suggests that there is an acute thermal limit near 36°/37°C for the four brittle star species tested which was experienced briefly in their natural habitats during the two month duration of the experiment. This suggests climate change in the form of increased SST will most likely have dramatic effects on the physiology and survival of tropical brittle star species in this area.