An overview of the thermal biology of selected species of the genus Thanatophilus (Coleoptera: Silphidae) in Central Europe: carrion beetles as an important tool for the forensic sciences

Santiago Montoya-Molina

Disertační práce

Abstract:

This thesis is the summary of the scientific work I have contributed to the knowledge of two important Thanatophilus (Coleoptera: Silphidae) species in Central Europe. All the chapters and articles aim to broaden the knowledge regarding the thermal biology (Thermal summation Model, Chill coma recovery time) for the selected species. Physiology and subsequently ecology of Silphids are bounded to environmental temperature. The temperatures experienced by beetles, will significantly change the species developmental times and thermal performance parameters. Carrion beetles of the genus Thanatophilus are an important group of necrophagous insects, widely distributed and attracted to large carcasses. The combination of the previous characteristics matches the requirements for the species to be considered of great potential in the forensic entomology worldwide. Nevertheless, developmental information for most of the Thanatophilus species is still unknown. Changes in the developmental times as response to difference in diet quality and photoperiod regime is missing. Furthermore, the responses to short periods of low temperatures and the changes in their ecological functions were still unstudied. Consequently, in the next chapters, we will analyse the knowledge gaps above mentioned in two species of the genus Thanatophilus. Chapter 1 gives an insight of the forensic entomology and the factors affecting ectotherms thermal biology. In Chapters 2 and 3 of this thesis, we provide the Thermal Summation Models for the two most common species of the genus Thanatophilus in Central Europe: T. sinuatus and T. rugosus. We bred the species at different ecological relevant temperatures and times of development and thermal summation parameters were calculated. In these manuscripts we present a novel methodology to breed Silphinae under constant laboratory conditions having into account previously suggested methodologies in the literature. As expected, T. sinuatus and T. rugosus development was faster at higher temperatures. In all the cases, development of both Thanatophilus species were faster than other forensically important species of Coleoptera. Chapters 4 and 5 explores T. rugosus and T. sinuatus developmental responses to different diets and photoperiods (in T. sinuatus). To examine the effects of different diets on the development times, different types of diet for larvae were tested (Pork muscle, Pork liver and Chicken muscle). Surprisingly, the impact of contrasting diets was different between the species. Thanatophilus rugosus times of development were faster when the species was fed under pork liver, followed by pork muscle. On the other hand, T. sinuatus developmental times were faster when larvae were fed with pork muscle followed by pork liver. Overall, chicken muscle prolonged the development in both species. Survival rate was also affected by the diet quality among the studied species. In T. rugosus survival rate decreased significantly when fed solely with chicken muscle (30.4%) compared to the highest pork liver (50.3%). In the case of T. sinuatus, survival rate was not affected by any of the studied diets. Also, no effect of the two tested photoperiods (16 h Light: 8h Dark and 12 h Light: 12h Dark) was found. In Chapter 6, Thanatophilus sinuatus cold tolerance was tested measuring the Chill Coma Recovery times (CCRt). Cold response in ectotherms depends on species life history traits. In order to quantify the CCRt, adult beetles of three physiological ages (10, 20 and 30 days-old) were subject of two exposure times (2 hours and 16 hours) at zero degrees Celsius. Results showed that younger beetles recover faster than old ones. In general, females recovered slower than males. Unexpectedly, weight had no significant effect on the CCRt. The results here presented provides an approximation on the species biology unveiling ecological and distributional temperature requirements. Thanatophilus sinuatus and T. rugosus

Abstract:

developmental biology can be used during criminal investigations complementing the entomological evidence when collected with Diptera. Moreover, beetles might be beneficial when other forensically important species are absent due to successional (left the carcass during late stages of decomposition) or environmental factors.

Keywords

Forensic Entomology, Silphinae, Thermal Summation Models, Developmental times

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 23. 3. 2023

Obhajoba závěrečné práce

• Vedoucí: doc. Mgr. Jan Růžička, Ph.D.

Česká zemědělská univerzita v Praze

Fakulta životního prostředí

Doktorský studijní program / obor:
Ecology / Ecology