González-Paredes, Daniel, Ariel, Ellen, David, Maria Florencia, Ferrando, Virginia, Marsh, Helene, and Hamann, Mark (2021) Gastrointestinal transit times in juvenile green turtles: an approach for assessing digestive motility disorders. Journal of Experimental Marine Biology and Ecology, 544. 151616.

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Abstract

The ingestion of anthropogenic marine debris can lead to injuries in the digestive system of marine turtles through blockages, lacerations and enteritis, as well as sub-lethal effects from bioaccumulation of adhered chemicals and toxic substances leached out into tissues and blood. The early detection of these impacts is central for the treatment and recovery of turtles in a rehabilitation setting. In this study, we provide baseline data on gastrointestinal transit times in healthy green turtles (Chelonia mydas) to enable non-intrusive detection of digestive motility disorders. We conducted two experiments with juvenile green turtles (N = 14) (curved carapace length range 33.7–47.0 cm) using inorganic (inert plastic discs) and organic (corn kernels) markers respectively, in order to estimate gastrointestinal transit times and assess the effectiveness of each marker type in recording them. Gastrointestinal transit times for the inorganic marker trial group (n = 6 turtles) ranged from 14.6 ± SD 3.6 days for the first markers recovered to 22.5 ± SD 4.2 days for the last markers recovered. The corresponding data for the organic marker trial group (n = 8 turtles) ranged from 6.63 ± SD 1.6 days to 17.3 ± SD 3.3 days respectively. We obtained 96% recovery success of markers in the inorganic marker trial versus 72.5% in the organic marker trial. Thus, inorganic markers proved to be more efficient in reporting gastrointestinal transit times because they do not degrade or discolour as they pass along the digestive process, enabling higher recovery success. Opportunistically, veterinarians diagnosed an obstruction caused by plastic fragments, which had been swallowed in the wild prior to the trial, in one of the experimental animals after we failed to recover any markers. This incident is evidence that gastrointestinal transit time assessment is a useful approach for providing early warning of digestive system blockages. Furthermore, this knowledge on transit times could be of interest for toxicology studies regarding exposure to chemicals lixiviated from debris ingested, as an index of the time spent by these substances inside the organism.

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