harus is either an osmoconformer or a weak osmoregulator. It can reverse the direction of its ventilatory flow by adjusting the sizes of apertures located at the bases of its legs, presumed to be a means of keeping particulate matter from obstructing these apertures. The apertures lead into the branchial chamber and are covered in dense setae for filtration. Unlike in most decapods, this period of reversed flow can be sustained, and it is commonly seen when the crab is buried or at rest. Its heart is a single-chambered ventricle which ejects hemolymph to seven arteries. Five arteries, including the anterior aorta, leave the heart anteriorly and supply organs such as the cerebral ganglion, eyes, antennae, hepatopancreas, and various digestive organs. One, which leaves the heart ventrally, is called the sternal artery and accounts for nearly 70% of flow; this branches into vessels which supply its five pairs of legs, the largest of which are those supplying its rear paddles. Finally, a relatively small posterior aorta runs down the middle of the crab's abdomen. Ovalipes catharus is a stenotherm, highly sensitive to temperature. An increase in water temperature of just a few degrees substantially accelerates its growth. At summer temperatures of about , catharus' heart rate is approximately 50 bpm. Above this temperature, its heartbeats begin to shorten. Its heart rate is more than doubled to 125 bpm at 25 °C (77 °F), and temperatures around 30 °C (86 °F) are fatal. Phosphorylation of ADP during respiration also decreases at temperatures over 20 °C (68 °F), indicating reduced ability of the mitochondria to produce ATP. At temperatures around 10 °C (50 °F) – near the lower end of what it experiences in the wild. catharus needs to be actively encouraged to eat, eats less overall, and takes over three times as long to digest its food as it does at . Ovalipes catharus hears underwater by using a small canal system located under its first antenna called a statocyst. The statocyst contains an agglomerate of sand particles called the statolith and functions similarly to the otolith in vertebrates. O. cath