Thermal dependency of burrowing in three species within the bivalve genus Laternula: a latitudinal comparison

The upper thermal limits for burrowing and survival were compared with micro-habitat temperature for anomalodesmatan clams: Laternula elliptica (Antarctica, 67A degrees S); Laternula recta, (temperate Australia, 38A degrees S) and Laternula truncata (tropical Singapore, 1A degrees N). Lethal limits (LT50) were higher than burrowing limits (BT50) in L. elliptica (7.5-9.0 and 2.2A degrees C) and L. recta (winter, 32.8-36.8 and 31.1-32.8A degrees C) but the same range for L. truncata (33.0-35.0 and 33.4-34.9A degrees C). L. elliptica and L. truncata had a BT50 0.4 and 2.4-3.9A degrees C, respectively, above their maximum experienced temperature. L. recta, which experience solar heating during midday low tides, had a BT50 0.7-2.4A degrees C below and a range for LT50 that spanned their predicted environmental maximum (33.5A degrees C). L. recta showed no seasonal difference in LT50 or BT50. Our single genus comparisons contrast with macrophysiological studies showing that temperate species cope better with elevated temperatures.