Variability in diel and seasonal in situ metabolism of the tropical gastropod Tectus niloticus

Abstract

Researchers often use metabolic measurements in the field over narrow time periods to estimate an organism's metabolism over large time scales. Here, we measured in situ respiration, calcification and excretion rates of the tropical gastropod Tectus niloticus L. through benthic chamber experiments. Our samples spanned a 21 h time frame and were taken during both the warm and cool seasons. We assessed diel and seasonal variability in metabolic rates, as well as the effect of individual size and the contribution of shell epi-and endobionts. Our results show that metabolic rates vary through time at both diel and seasonal scales, as measured fluxes for respiration and calcification were significantly higher at night during the warm season. This nocturnal pattern was not significant in the cool season. Size effects were significant with higher respiration and calcification rates for small individuals regardless of the season, although the difference tended to be more pronounced in the warm season. We also found that shell epi-and endobionts made an important contribution to respiration, as 40 and up to 100% of total measured fluxes for night and day, respectively, could be attributed to the shell community. More importantly, the direction of the measured flux was occasionally opposite that of the individual trochus, highlighting that the contribution of shell epi-and endobionts must be accounted for in order to achieve an accurate understanding of individual metabolism. Lastly, depending on the time of day and season when measurements are taken, ignoring diel or seasonal variations in metabolic rates could result in important under-or overestimation of the contributions of gastropods to carbon and calcium carbonate fluxes in coastal ecosystems.

Circadian behaviour of Tectus (Trochus) niloticus in the southwest Pacific inferred from accelerometry

“…Moreover, the small topshells from Vanuatu have also depicted a higher activity than the small specimen from New Caledonia. These results were comparable to the measurements of respiration made by Lorrain et al [ 40 ] on topshells from New Caledonia during the warm and cool seasons. Indeed, the large specimens had similar respiration rates during the night between the warm and cool seasons (9.9 vs 8.6 μmol.C.g −1 ).…”

“…In addition, during our study, the tagged topshells did not experience the extreme temperatures that can occur in their environment or within their geographical distribution. Indeed, the temperatures measured in Vanuatu are comparable to those found in New Caledonia during the warm season [ 40 ]. Thus, in the present study, we were not able to measure the activity corresponding to the thermal performance curve of this species as reported by Gannon et al [ 48 ].…”

“…Small trochus had respiration rates higher than large specimens with a maximum during the warm season (17.6 vs 12.7 μmol.C.g −1 ). Previous studies have demonstrated that oxygen consumption correlates with temperature [ 40 , 68 , 69 ]. Body size would be one of the most important factors affecting metabolism.…”

“…Here, we applied accelerometry technology to characterise the duration and intensity of T. niloticus activity in their natural environment in New Caledonia and Vanuatu. We also compared T. niloticus activity to metabolic measurements performed simultaneously and published in a companion paper [ 40 ].…”

Tectus niloticus (Tegulidae, Gastropod) as a Novel Vector of Ciguatera Poisoning: Detection of Pacific Ciguatoxins in Toxic Samples from Nuku Hiva Island (French Polynesia)

“…Tectus niloticus Linnaeus, 1767 (Gastropoda, Trochoidea, Tegulidae), a large, herbivorous marine snail widespread throughout Southeast Asia and the Western Pacific, is commonly known as trochus or top shell [ 1 , 2 , 3 ]. It can be found in both intertidal and subtidal reef habitats, generally in high energy sections of the reef.…”