![]() ![]() Conversely, Vogt ( 1979) anecdotally reported finding live leeches attached to turtles that had been kept out of water for four days, and Hall ( 1922) reported that the leech Placobdella parasitica can survive desiccation up to a body water loss of ~92%. Given that the leeches that parasitize turtles are aquatic, this is a reasonable proposal, and there are scattered, anecdotal observations of leeches leaving basking turtles (Saumure & Livingstone, 1994 Selman et al., 2008 Selman & Qualls, 2009). obs.).Īn alternative hypothesis proposes that basking is a mechanism for removing ectoparasites, particularly leeches (Mcauliffe, 1977 Koffler et al., 1978 Reshk, 2009 Mitchell & Johnston, 2012). Nocturnal basking may, however, provide an opportunity to thermoregulate by avoiding unfavorable water temperatures (Nordberg and McKnight pers. To further complicate matters, some turtles “bask” at night (Barhadiya et al., 2020 Nordberg & McKnight, 2020), a time period when this behavior would not result in increased body temperatures from direct solar radiation. Some authors have, however, challenged the notion that basking is primarily for thermoregulation (e.g., Manning & Grigg, 1997). Therefore, it may be advantageous for turtles to engage in behaviors that remove parasites however, the fitness costs have not been well established (see Schall, 1986 and Brown et al., 2006).īasking behavior in turtles is generally thought to be thermoregulatory (specifically, increasing body temperature) and is often referred to as “sunning” due to turtles’ proclivity for sitting on sunny substrates with their limbs outstretched (Boyer, 1965 Chessman, 1987, 2020). This may have important consequences, because there is some evidence that high parasitemia of red blood cells can result in anemia or other histopathologies (Schall et al., 1982 Peirce & Adlard, 2007 Despommier et al., 2017). Leeches are a common ectoparasite for many freshwater turtles, and they can transmit hemoparasites, such as the apicomplexan protozoa of the genera Haemogregarina and Hepatozoon (Strohlein & Christensen, 1984 Siddall & Desser, 1992 Rossow et al., 2013 Arizza et al., 2016). ![]() Birds, for example, engage in behaviors such as preening, dust bathing, and sunning to remove parasites (Bush & Clayton, 2018). As a result, parasites often influence host ecology and behavior, including causing hosts to shift behaviors in an effort to remove parasites or mitigate the diseases they spread (Schall & Sarni, 1987 Main & Bull, 2000, Bower et al., 2019). ![]() Therefore, leech removal does not appear to be the purpose of the majority of basking events.Įctoparasites can adversely impact host health by absorbing nutrients and spreading diseases (Bower et al., 2019). Our data showed even the 20-min period was longer than 70.1% of natural diurnal basking events, many of which took place at cooler temperatures. However, it was only effective at unusually long basking durations in this system. These results indicate basking can remove leeches if temperatures are high or basking durations are long. Diurnal basking outdoors under direct sunlight for 20 min (mean temp = 34.5☌) resulted in a small reduction in leeches, with 50% of turtles losing leeches and an average loss of 0.7 leeches per turtle. Only 18% of turtles lost leeches (one turtle lost one leech and another lost four leeches). Similarly, “nocturnal basking” at ~23☌ for 3 hr was not effective at removing leeches. In diurnal trials, 90.9% of turtles lost leeches (mean loss of 7.1 leeches per turtle), whereas basking for 30 min under the same conditions was not effective (no turtles lost leeches, and all turtles were still visibly wet). Diurnal basking under a heat lamp for 3 hr at ~28☌ significantly reduced numbers of leeches relative to controls. Turtles had high initial leech loads, with a mean of 32.1 leeches per turtle. Therefore, we examined the number of leeches that were removed from Krefft's river turtles ( Emydura macquarii krefftii) after experimentally making turtles bask at a range of times of day, durations, and temperatures. However, the efficacy of basking, day or night, to remove leeches has not been experimentally tested. Leaving the water to bask (usually in the sun) is a common behavior for many freshwater turtles, with some species also engaging in “nocturnal basking.” Ectoparasite removal is an obvious hypothesis to explain nocturnal basking and has also been proposed as a key driver of diurnal basking. ![]()
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