Merycism or Rumination Disorder

Parry-Jones, Brenda

doi:10.1192/bjp.165.3.303

Cited by 34 publications

(2 citation statements)

References 36 publications

(18 reference statements)

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“…Although regurgitation/reingestion has been described in gorillas (Gorilla gorilla) [24], it is not linked to an adaptive physiological process but is considered pathological, and does not occur in free-ranging animals. In humans, 'merycism' or 'rumination disorder' is considered an abnormal condition that affects adults, but in particular infants or intellectually handicapped individuals, and is sometimes related to eating disorders [25]. R/R or merycism, as a physiological phenomenon, has so far only been investigated systematically in koalas [11], where it represented on average 3.9 per cent of total feeding time.…”

Section: Discussionmentioning

confidence: 99%

Regurgitation and remastication in the foregut-fermenting proboscis monkey ( Nasalis larvatus )

et al. 2011

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Although foregut fermentation is often equated with rumination in the literature, functional ruminants (ruminants, camelids) differ fundamentally from non-ruminant foregut fermenters (e.g. macropods, hippos, peccaries). They combine foregut fermentation with a sorting mechanism that allows them to remasticate large particles and clear their foregut quickly of digested particles; thus, they do not only achieve high degrees of particle size reduction but also comparatively high food intakes. Regurgitation and remastication of stomach contents have been described sporadically in several non-ruminant, non-primate herbivores. However, this so-called 'merycism' apparently does not occur as consistently as in ruminants. Here, to our knowledge we report, for the first time, regurgitation and remastication in 23 free-ranging individuals of a primate species, the foregut-fermenting proboscis monkey (Nasalis larvatus). In one male that was observed continuously during 169 days, the behaviour was observed on 11 different days occurring mostly in the morning, and was associated with significantly higher proportions of daily feeding time than on days when it was not observed. This observation is consistent with the concept that intensified mastication allows higher food intake without compromising digestive efficiency, and represents an expansion of the known physiological primate repertoire that converges with a strategy usually associated with ruminants only.

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Section: Discussionmentioning

confidence: 99%

Regurgitation and remastication in the foregut-fermenting proboscis monkey ( Nasalis larvatus )

et al. 2011

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“…This behaviour is referred to by the Greek term for ‘rumination’ as merycism [89], or as regurgitation and remastication or reingestion [90]. Both terms are also used for the behaviour when it is considered pathological, in humans and in captive great apes [91,92].…”

Section: Ruminationmentioning

confidence: 99%

Teeth and the gastrointestinal tract in mammals: when 1 + 1 = 3

Clauss,

Fritz,

Hummel

2023

Phil. Trans. R. Soc. B

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Both teeth and the digestive tract show adaptations that are commonly interpreted in the context of trophic guilds—faunivory, herbivory and omnivory. Teeth prepare food for the digestive tract, and dental evolution focuses on increasing durability and functionality; in particular, size reduction of plant particles is an important preparation for microbial fermentative digestion. In narratives of digestive adaptations, microbes are typically considered as service providers, facilitating digestion. That the majority of ‘herbivorous’ (and possibly ‘omnivorous’) mammals display adaptations to maximize microbes' use as prey—by harvesting the microbes multiplying in their guts—is less emphasized and not reflected in trophic labels. Harvesting of microbes occurs either via coprophagy after separation from indigestible material by a separation mechanism in the hindgut, or from a forestomach by a ‘washing mechanism’ that selectively removes fines, including microbes, to the lower digestive tract. The evolution of this washing mechanism as part of the microbe farming niche opened the opportunity for the evolution of another mechanism that links teeth and guts in an innovative way—the sorting and cleaning of not-yet-sufficiently-size-reduced food that is then re-submitted to repeated mastication (rumination), leading to unprecedented chewing and digestive efficiency. This article is part of the theme issue ‘Food processing and nutritional assimilation in animals’.

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