Thermal Resilience of Feeding Kinematics May Contribute to the Spread of Invasive Fishes in Light of Climate Change

Abstract

As a consequence of global warming, tropical invasive species are expected to expand their range pole-ward, extending their negative impacts to previously undisturbed, high-latitude ecosystems. Investigating the physiological responses of invasive species to environmental temperature is important because the coupled effects of climate change and species invasion on ecosystems could be more alarming than the effects of each phenomenon independently. Especially in poikilotherms, the rate of motion in muscle-driven biomechanical systems is expected to double for every 10 °C increase in temperature. In this study, we address the question, "How does temperature affect the speed of jaw-movement during prey-capture in invasive fishes?" Kinematic analysis of invasive-fish prey-capture behavior revealed that (1) movement velocities of key components of the feeding mechanism did not double as water temperature increased from 20 °C to 30 °C; and (2) thermal sensitivity (Q10 values) for gape, hyoid, lower-jaw rotation, and cranial rotation velocities at 20 °C and 30 °C ranged from 0.56 to 1.44 in all three species. With the exception of lower-jaw rotation, Q10 values were significantly less than the expected Q10 = 2.0, indicating that feeding kinematics remains consistent despite the change in environmental temperature. It is conceivable that the ability to maintain peak performance at different temperatures helps facilitate the spread of invasive fishes globally.

Keywords: global warming; organismal performance; prey-capture; suction feeding; thermal tolerance.

Figure 1

Diagram depicting the experimental design investigating the effects of environmental temperature on the kinematic velocity to reach maximum gape, hyoid depression, cranial rotation, and lower-jaw rotation. Four individuals of each invasive species Belonesox belizanus, Pterois volitans, and Cichlasoma urophthalmus were filmed while feeding on live-fish prey at 20 °C, 25 °C, and 30 °C using high-speed video. The best four films of each individual feeding at each temperature were digitized to measure the four kinematic velocities stated above and to calculate Q10 values. Kinematic velocities and Q10 values were subjected to the appropriate statistical tests to determine the effects of temperature on prey-capture performance.

Figure 2

Diagram of the pike killifish, Belonesox belizanus (top), lionfish, Pterois volitans (middle), and Mayan cichlid, Cichlasoma urophthalmus (bottom) showing the homologous hotspots used to measure peak gape (= maximum distance measured from the anteriormost tip of the premaxilla (A) to the anteriormost tip of the dentary (C)), peak hyoid depression (= maximum distance between the center of the eye (E) to the anteriormost tip of the hyoid bar (D)), peak lower-jaw rotation (= maximum posteroventral rotation of the lower-jaw, measured as the angle formed by line segments AB (= jaw-joint) to BC), and peak cranial rotation (= maximum posterodorsal rotation of the neurocranium, measured by the angle formed by line segments AG (= dorsal tip of the pectoral-fin base) to GF (= anterior tip of the dorsal-fin base)).

Figure 3

Select frames of representative films of two lionfish showing the sequence of kinematic events during prey capture in lionfish, Pterois volitans, at 20 °C, and 30 °C. Note that all species of invasive fishes successfully captured prey in both temperatures.

Figure 4

Scatterplot showing the relationship between each of the four kinematic-velocity variables and feeding temperature 20 °C, 25 °C, and 30 °C. Results of the regression analysis that quantified the effect of temperature on each of the kinematic events are presented in Table 1.

Figure 5

Mean Q10 values for kinematic-velocity in each of the three invasive-fish species. Note that except for the mean Q10 values for lower-jaw rotation in the Mayan cichlid and lionfish, all Q10 values of kinematic velocity were significantly less than the expected Q10 value of 2.0 for fish feeding at 20 °C and 30 °C. Error bars indicate standard error of the mean.