The energetic costs of living in the surf and impacts on zonation of shells occupied by hermit crabs

Abstract

Crashing waves create a hydrodynamic gradient in which the most challenging effects occur at the wave breaking zone and decrease towards the upper protected tide pools. Hydrodynamic forces depend on the shape of the submerged body; streamlined shapes decrease drag forces compared with bluff or globose bodies. Unlike other animals, hermit crabs can choose their shell shape to cope with the effects of water flow. Hermit crabs occupy larger and heavier shells (conical shape) in wave-exposed sites than those used in protected areas (globose shape). First, we investigated whether a behavioral choice could explain the shells used in sites with different wave action. Then, we experimentally tested whether the shells most frequently used in sites with different wave action reduce the energetic cost of coping with water flow. Metabolic rate was measured using a respirometric system fitted with propellers in opposite walls to generate bidirectional water flow. The choice of shell size when a large array of sizes are available was consistent with the shell size used in different intertidal sites; hermit crabs chose heavier conical shells in water flow conditions than in still water, and the use of heavy conical shells reduced the energetic cost of coping with water motion. In contrast to conical shells, small globose shells imposed lower energy costs of withstanding water flow than large globose shells. The size and type of shells used in different zones of the rocky shore were consistent with an adaptive response to reduce the energetic costs of withstanding wave action.

Doors to the Homes: Signal Potential of Red Coloration of Claws in Social Hermit Crabs

“…Determining what, if any, components of diet contribute to the accrual and retention of red coloration in this species will require experiments with controlled feeding regimens. Future experiments can also separately consider crabs’ ages, which need not be equivalent to their body sizes, given that hermit crabs metabolically control their growth (e.g., Alcaraz and García-Cabello 2017 ; Alcaraz et al. 2020 ), growing only when they acquire larger shells.…”

Metabolic and behavioural effects of hermit crab shell removal techniques: Is heating less invasive than cracking?

“…We captured 80 Calcinus californiensis (Bouvier 1898 ) hermit crabs of similar size occupying shells of Nerita scabricosta (Lamarck 1822 ) with no apparent damage or epibionts in Troncones, Guerrero, Mexico. The length of the chela (4–6 mm) was used as a preliminary measure to estimate the body size of the hermit crabs (Alcaraz et al 2020 ). We kept the hermit crabs in an individual glass flask, which was also used as respirometric chamber (0.03 L), in a circulating seawater system at 27°C and 34 practical salinity unit (PSU).…”

“…This increases the shell’s weight and modifies its centre of mass, making walking uncomfortable for the crab and most probably costly energetically; consequently, the hermit crabs ‘voluntarily’ swap to the alternative refuge provided, even when this is not ideal (e.g. too small or large; Arce & Alcaraz 2013 ; Alcaraz et al 2020 ). However, there are experimental procedures which require the hermit crabs to be ‘naked’ for specific measurements or manipulations prior to starting the trials or after experimentation.…”

Hefting Heavy Shells: Sustenance Demands Caused by Various Abodes of the Hermit Crab Pagurus granosimanus

“…Vance [3] experimentally demonstrated that individuals of P. granosimanus that inhabited smaller shells were at higher risk of crab predation, and Spight [12] postulated that hermit crabs rarely used the species Lirabuccinum dirum's available shells due to its thin walls. Shell weight can also provide hydrodynamic advantages in wave-exposed areas [13,14].…”

“…Heavier shells display slow growth [5] and references therein, [17]. In hypoxic conditions, some hermit crabs shift to significantly lighter choices [18], and others shift from heavier, conical shells to smaller, lighter, globose ones when moving to areas of slower-flowing water [14]. Female hermit crabs of some species tend to utilize lighter shells than do the males, perhaps due to the additional weight of eggs [19,20].…”