Table 4 in Sub-Antarctic Freshwater Invertebrate Thermal Tolerances: An Assessment of Critical Thermal Limits and Behavioral Responses

Table 4. Behavioral responses to water temperature increase (point of thermal reactivity, PTR, and critical thermal endpoint, CTE) of sub-Antarctic macroinvertebrate taxa. Suitability ranks SR: 1 = very suitable, 2 = suitable with limitations, and 3 = not suitable, and thermal sensitivity rank TSR: 1 = very sensitive (≤25 ◦ C), 2 = moderately sensitive (≤30 ◦ C), and 3 = less sensitive (≥30 ◦ C) (adapted from Dallas and Rivers-Moore 2012).
Macroinvertebrate TaxaBehavioral ResponseSRTSRAmphipoda: Hyalellidae Hyalella sp.Before temperature increase, individuals swam intermittently in the experimental chambers, moving from bottom to top, and vice-versa. The PTR was apparent as a substantial decrease in swimming speed. The CTE was identified when individuals remained at the bottom of the chamber and stopped swimming. The only detectable movement was then from the antennae and hind legs.23Coleptera: Dytiscidae Lancetes angusticollisBefore temperature increase, individuals swam intermittently in the experimental chambers, moving from bottom to top, and vice-versa. The PTR was apparent as a substantial increase in movement, constantly grabbing air bubbles with difficulty in maintaining them. The CTE was identified as inactivity at the bottom of the chamber, or floating near the surface.33Hemiptera: Corixidae Sigara sp.Before temperature increase, individuals swam intermittently in the experimental chambers, moving from bottom to top, and vice-versa. The PTR was apparent when individuals started to accelerate their movement. The CTE was reached when individuals sank to the bottom of the chamber, or floated at the top with no detectable movement other than the palas (anterior legs).33Rhabditophora: Tricladida DugesiidaeBefore temperature increase, individuals crawled on the bottom of the chamber. The PTR was apparent when individuals start to agitate their bodies sideways. When the CTE was reached, individuals started to expose their digestive structures outside their bodies and remained almost immobile at the bottom of the chamber.21Plecoptera: Gripopterygidae Aubertoperla kuscheliBefore temperature increase, individuals crawled on the bottom of the chamber, started moving their legs and cerci. As the PTR was reached individuals lost their grip and start swimming slowly. The CTE was identified when individuals lost grip and swimming capacity, floating at the top of the chamber and remaining immobile with the exception of antennal movement.22Diptera: Chironomidae TanypodinaeBefore temperature increase, individuals crawled on the bottom of the experimental chamber. The PTR was apparent when individuals started to move and shake at the bottom of the chamber. When they reached the CTE, individuals lost the ability to remain attached to the bottom and floated virtually motionless.11