4.2.5. Additional hypotheses
There were a few hypotheses mentioned in the literature that warranted less attention based on their obvious lack of support or generality. Koch (1978) proposed that extensive spiraling in scorpion burrows could reduce the effects of wind-blown debris entering the burrow. This is logical, but scorpions and other terrestrial animals often clear their burrows of debris including blown sand, cave-in sand and vegetation (Shorthouse and Marples, 1980). Spiral burrows produced by marine organisms may help keep the burrow free of sediment debris. Another hypothesis, raised for Gyrolithes , suggests that the helical burrow promotes anchoring of the tracemaker in the burrow in a high-energy environment (Gingras et al., 2008; see also Laing et al., 2018). However, the Gyrolithes studied by Moosavizadeh and Knaust (2021) reflected a low-energy environment. Finally, some male ghost crabs (Ocypode ) may construct spiral burrows for courtship (Schober & Christy, 1993; Clayton, 2005). However, only one species has been shown to construct burrows with more than one spiral: at least some of the burrows of Ocyopde ceratophthalmus exhibit two spirals (Parenzan, 1931, in: Eshky, 1985; Fellows, 1966, in: Vannini, 1980). Some authors have included the hypothesis that helical burrows serve(d) as domiciles (domichnia) that protect the burrows inhabitants (e.g., Laing et al., 2018). We did not consider this hypothesis because it cannot in itself explain the evolution, benefits, or function of helical structure above and beyond what the aforementioned hypotheses (e.g., antipredator) attempt to explain.