Thanatosis in the Brazilian seahorse Hippocampus reidi Ginsburg, 1933 (Teleostei: Syngnathidae)

Freret-Meurer, Natalie Villar; Fernández, T.; Lopes, Daniela A.; Vaccani, Amanda do Carmo; Okada, N.

doi:10.1007/s10211-016-0247-y

Cited by 7 publications

(4 citation statements)

References 24 publications

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“…We found at least one article for all the branches of the cladogram. Two articles were selected for Arachnida, 31 , 32 Hexapoda, 29 , 33 Crustacea, 34 , 35 Chondrichthyes, 36 , 37 Actinopterygii, 38 , 39 Amphibia, 40 , 41 Bifurcata, 21 , 42 Metatheria, 17 , 43 Artiodactyla, 44 , 45 Canidae, 46 , 47 Rodentia, 23 , 48 Leporidae, 49 , 50 Cercopithecoidea 51 , 52 and Homo sapiens . 25 , 26 Three articles were selected for the Aves class.…”

Section: Resultsmentioning

confidence: 99%

The evolutionary origin of near-death experiences: a systematic investigation

Peinkhofer

Martial

Cassol

et al. 2021

Brain Communications

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Near-death experiences are known from all parts of the world, various times and numerous cultural backgrounds. This universality suggests that near-death experiences may have a biological origin and purpose. Adhering to a preregistered protocol, we investigate the hypothesis that thanatosis aka. death-feigning, a last-resort defense mechanism in animals, is the evolutionary origin of near-death experiences. We first show that thanatosis is a highly preserved survival strategy occurring at all major nodes in a cladogram ranging from insects to humans. We then show that humans under attack by animal, human and “modern” predators can experience both thanatosis and near-death experiences, and we further show that the phenomenology and the effects of the two overlap. In summary, we build a line of evidence suggesting that thanatosis is the evolutionary foundation of near-death experiences and that their shared biological purpose is the benefit of survival. We propose that the acquisition of language enabled humans to transform these events from relatively stereotyped death-feigning under predatory attacks into the rich perceptions that form near-death experiences and extend to non-predatory situations.

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Section: Resultsmentioning

confidence: 99%

The evolutionary origin of near-death experiences: a systematic investigation

Peinkhofer

Martial

Cassol

et al. 2021

Brain Communications

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“…At night, seahorses displayed higher perch heights and upright body postures and changes in holdfast preferences. During the day, Sweetings Pond seahorses displayed more cryptic behaviors, with animals lying prone on the substrate, similar to the thanatosis (death‐like horizontal posture) behaviors observed in the slender seahorse ( Hippocampus reidi , Freret‐Meurer et al, 2017). Factors driving this shift in the water column and changing body position remain unclear.…”

Section: Discussionmentioning

confidence: 54%

“…This high‐density, male‐biased population provides a unique system to assess interactions between the sexes and their behaviors over a 24‐h diel cycle. Previous work included formal population sampling during the day (Masonjones et al, 2019) with animals observed engaging in cryptic behaviors in groups fewer than four seahorses (animals camouflage and tuck themselves away within the structure of the habitat) consistent with the behavior of other seahorse species (Freret‐Meurer et al, 2017). Both formal nocturnal fish census using baited remote underwater video (BRUV) and informal nighttime observations in Sweetings Pond suggest that this population of H. erectus may be nocturnal, engaging in noncryptic behaviors, including congregating in large social groups of up to 14 animals, perching on the top of vegetation, and performing courtship displays (Mason, unpublished data; O'Brien et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Nocturnal surveys of lined seahorses reveal increased densities and seasonal recruitment patterns

Masonjones

Rose

Gonzalez

et al. 2023

Ecology and Evolution

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Although the nighttime ecology of organisms remains understudied, nocturnal surveys play an integral part in assessing fish assemblages and the selective forces shaping them. Eleuthera (Bahamas) contains an unusual population of lined seahorses (Hippocampus erectus) in an anchialine lake, possessing morphological characteristics distinct from those found in the ocean. Population surveys for seahorses and their potential predators were conducted at midnight and midday during wet and dry seasons, with belt transects perpendicular to the shoreline that increased in depth away from shore. Nocturnal surveys uncovered seahorse densities 259% higher than daytime transects on average. Sex ratios were consistently male-biased, and the frequency of animals from different reproductive categories varied significantly by time of day, with gravid males observed around the clock but females and nongravid males observed more often at night. Spatial and seasonal recruitment was detected for the first time in this species, with an increase in juveniles detected in the shallow ends of transects during dry season surveys. Juvenile recruitment is poorly understood across syngnathid fishes, so the detection of early recruits at night has broad implications for this fish family. Seahorses from all reproductive categories were perched significantly higher in the water column during the night regardless of their depth or season. Predator densities followed a similar pattern with higher densities observed at night, indicating that elevated nocturnal perch height may be a response to predator presence. However, the selective agents driving these nocturnal behaviors have yet to be identified. Considering H. erectus is listed on the IUCN Red List as "Vulnerable," the increase in nocturnal population size and the detection of juveniles has crucial implications for understanding their ecology, recruitment, and conservation.

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“…In the invertebrates, it has been suggested to occur (at least) in: crustaceans, stick insects, spiders, butterflies, stoneflies, water-scorpions, cicadas, crickets, mites, beetles, damselfly larvae, ants, bees and wasps (see Cassill et al 2008 for a partial list and references, and the following for a few more recent invertebrate examples: Coutinho et al 2013 ; Ritter et al 2016 ; Cadena-Castañeda et al 2016 ; Neves and Pie 2017 ). In the vertebrates, it has been recorded in mammals, birds, reptiles, amphibians and fish (again, see Cassill et al 2008 for a partial list and references, and the following for a few more recent vertebrate examples: Gally et al 2012 ; Marques et al 2013 ; Sannolo et al 2014 ; Batista et al 2015 ; Muscat et al 2016 ; Sanchéz Paniagua and Abarca 2016 ; Patel et al 2016 ; de Castro et al 2017 ; Freret-Meurer et al 2017 ). Even within well-studied vertebrate groups, though, the precise distribution of the behaviour is unclear—there are probably a few reasons for this.…”

Section: Taxonomic Distributionmentioning

confidence: 99%

A review of thanatosis (death feigning) as an anti-predator behaviour

Humphreys

Ruxton

2018

Behav Ecol Sociobiol

149

118

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Thanatosis—also known as death-feigning and, we argue more appropriately, tonic immobility (TI)—is an under-reported but fascinating anti-predator strategy adopted by diverse prey late on in the predation sequence, and frequently following physical contact by the predator. TI is thought to inhibit further attack by predators and reduce the perceived need of the predator to subdue prey further. The behaviour is probably present in more taxa than is currently described, but even within well-studied groups the precise taxonomic distribution is unclear for a number of practical and ethical reasons. Here we synthesise the key studies investigating the form, function, evolutionary and ecological costs and benefits of TI. This review also considers the potential evolutionary influence of certain predator types in the development of the strategy in prey, and the other non-defensive contexts in which TI has been suggested to occur. We believe that there is a need for TI to be better appreciated in the scientific literature and outline potentially profitable avenues for investigation. Future use of technology in the wild should yield useful developments for this field of study.Significance statementAnti-predatory defences are crucial to many aspects of behavioural ecology. Thanatosis (often called death-feigning) has long been an under-appreciated defence, despite being taxonomically and ecologically widespread. We begin by providing much-needed clarification on both terminology and definition. We demonstrate how apparently disparate observations in the recent literature can be synthesised through placing the behaviour within a cost-benefit framework in comparison to alternative behavioural choices, and how aspects of the ecology differentially affect costs and benefits. Extending this, we provide novel insights into why the evolution of thanatosis can be understood in terms of coevolution between predators and prey. We offer further novel hypotheses, and discuss how these can be tested, focussing on how emerging technologies can be of great use in developing our understanding of thanatosis in free-living animals.

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Thanatosis in the Brazilian seahorse Hippocampus reidi Ginsburg, 1933 (Teleostei: Syngnathidae)

Cited by 7 publications

References 24 publications

The evolutionary origin of near-death experiences: a systematic investigation

The evolutionary origin of near-death experiences: a systematic investigation

Nocturnal surveys of lined seahorses reveal increased densities and seasonal recruitment patterns

A review of thanatosis (death feigning) as an anti-predator behaviour

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