Patterns and mechanisms for larval aggregation in carrion beetle Necrodes littoralis (Coleoptera: Silphidae)

Mądra‐Bielewicz

2019

Preprint

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14Insects regulate their body temperature mostly behaviorally, by changing posture or 15 microhabitat. These strategies may be ineffective in some habitats, for example on carrion. 16 Carrion beetles create a biofilm-like matrix by applying to cadaver surface anal or oral 17 exudates. We tested the hypothesis that biofilm formed by communally breeding Necrodes 18 littoralis L. beetles (Silphidae) produces heat, that enhances beetle fitness. We demonstrated 19 that heat produced in the biofilm is larger than in meat decomposing without insects. Beetles 20 regularly warmed up in the biofilm. Moreover, we provide evidence that biofilm formation by 21 adult beetles has deferred thermal effects for larval microhabitat. We found an increase in heat 22 production of a biofilm and a decrease in development time and mortality of larvae, after 23 adult beetles applied their exudates on meat. Behavioral strategy revealed here for N. littoralis 24 is basically a new form of thermoregulation and parental care in insects. 25 26 Keywords 27 Insect thermoregulation; Animal behavior; Parental care; Carrion ecology; Insect-microbe 28 interactions; Resource competition 29 30 31Temperature is a key component of animal environment. Insects usually use external 32 heat to regulate their body temperature (1, 2). By changing body orientation or selecting 33 microhabitat with specific thermal characteristics, insects may maintain their body 34 temperature within thermal optima (3, 4). These mechanisms may be ineffective at certain 35 developmental stages (e.g. larvae) and in some microhabitats (e.g. carrion or dung), indicating 36 that other thermal options may be important for some insect ectotherms. 37Carrion is an example of a "bonanza" resource, i.e. very rich but at the same time 38 scattered and ephemeral (5). There is severe competition between microbes, insects, and 39 vertebrates over carrion resources (6)(7)(8)(9)(10)(11)(12). Insects, e.g. blow flies (Calliphoridae) or carrion 40 beetles (Silphidae) use carrion for breeding and their larvae are main carrion reducers in 41 terrestrial environments (11, 13, 14). Necrophagous larvae usually feed in aggregations (15). 42Larval aggregates on carrion may have much higher inner temperature than ambient air (by 43 10-30°C), an effect originally discovered in aggregations of larval blow flies (4, 16-20). Heat 44 in these aggregates was hypothesized to derive from microbial activity (21, 22), larval 45 exothermic digestive processes (19) or larval frenetic movements (20, 23). However, the 46 specific mechanisms involved are not known. 47 Carrion beetles, in particular burying beetles (Silphidae: Nicrophorus), create a 48 biofilm-like matrix on cadavers by applying to its surface anal and oral exudates (24). In case 49 of Nicrophorus the behavior was hypothesized to moisturize carrion (25), facilitate digestion 50 (25-27), suppress microbial competitors (24, 28-31), deter insect competitors by reducing 51 carrion-originating attractants (25, 32, 33), support larval aggregation (25) or...

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Heat production in a feeding matrix formed on carrion by communally breeding beetles

Mądra‐Bielewicz

2019

Preprint

Self Cite

“…The maximum temperature of the aggregation probably overestimates the true temperatures experienced by the larvae. Perhaps the heat benefit of the aggregated larvae is somehow related to the temperatures selected by the larvae along a thermal gradient [ 143 , 154 , 156 ]. Further research using tracking techniques to monitor heat benefits and the development time of individual larvae within large aggregations will be necessary to find the minimum development times or the optimal temperatures for the larvae that develop in an aggregation.…”

Section: Temperature Conditionsmentioning

confidence: 99%

Post-Mortem Interval Estimation Based on Insect Evidence: Current Challenges

2021

Insects

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During death investigations insects are used mostly to estimate the post-mortem interval (PMI). These estimates are only as good as they are close to the true PMI. Therefore, the major challenge for forensic entomology is to reduce the estimation inaccuracy. Here, I review literature in this field to identify research areas that may contribute to the increase in the accuracy of PMI estimation. I conclude that research on the development and succession of carrion insects, thermogenesis in aggregations of their larvae and error rates of the PMI estimation protocols should be prioritized. Challenges of educational and promotional nature are discussed as well, particularly in relation to the collection of insect evidence.

“…The egg stage of N. littoralis lasts on average 3.4 days at 22°C and 4.9 days at 18°C (Gruszka, personal communication). Necrodes larvae feed in aggregations, which form in the warmest place and relocate in response to changes in the heat source location [14]. This indicates that heat plays an important role in the formation and maintenance of larval aggregations in Necrodes [14].…”

mentioning

confidence: 99%

Heat production in a feeding matrix formed on carrion by communally breeding beetles

Mądra‐Bielewicz

2021

Front Zool

Self Cite

Insects regulate their body temperature mostly behaviourally, by changing posture or microhabitat. Usually they use heat that is already present in the environment. Sometimes, however, they may manipulate the environment to affect, focus or benefit from thermogenesis. Carrion beetles create a feeding matrix by applying to cadaver surface anal or oral exudates. We tested the hypothesis that the matrix, which is formed on carrion by communally breeding beetle Necrodes littoralis L. (Silphidae), produces heat that enhances insect fitness. Using thermal imaging we demonstrate that heat produced in the matrix formed on meat by adult or larval beetles is larger than in meat decomposing without insects. Larval beetles regularly warmed up in the matrix. Moreover, by comparing matrix temperature and larval fitness in colonies with and without preparation of meat by adult beetles, we provide evidence that formation of the matrix by adult beetles has deferred thermal effects for larval microhabitat. We found an increase in heat production of the matrix and a decrease in development time and mortality of larvae after adult beetles applied their exudates on meat in the pre-larval phase. Our findings indicate that spreading of exudates over carrion by Necrodes larvae, apart from other likely functions (e.g. digesting carrion or promoting growth of beneficial microbes), facilitates thermoregulation. In case of adult beetles, this behaviour brings distinct thermal benefits for their offspring and therefore may be viewed as a new form of indirect parental care with an important thermal component.