Thorectes lusitanicus

Thorectes lusitanicus is a species of medium-sized dung beetle. On average, they range from 130 to 175 mg in dry body weight. Most dung beetles have notable protective sheathed wings, or elytra. Notably, T. lusitanicus, and all other members of the Geotrupidae family, are apterous, meaning they have lost the capacity to fly. This apterism is related to unique morphological changes in the Geotrupidae family, such as the fusion of their elytra and atrophy of their wing muscles. T. lusitanicus has mandibles with well-developed scissorial and molar areas, as well as strong denticles that allow it to exploit dry dung and dung-fiber, rather than dung-juice. == Geographic range ==

Thorectes lusitanicus are native to the southern Iberian Peninsula, which is present-day Spain and Portugal. == Habitat ==

Researchers have noted the presence of Thorectes lusitanicus within oak forests. Studies illustrate that T. lusitanicus prefers the microsite of trees with no shrub understory in oak forests. This is likely due to an abundance of acorns and low competition from rodents, since rodents tend to forage under dense shrub cover to avoid predation. == Home range ==

Dung beetles utilize three primary nesting strategies. Some species tunnel directly under, or very close to, the dung deposition; these species are referred to as paracoprid. Others build their nests within the dung patch directly and are referred to as endocoprid. The last nesting strategy is building shallow tunnels several meters from the site of the dung deposition and transporting the dung into the tunnel; species that utilize this strategy, like T. lusitanicus, are referred to as telocoprid. More specifically, researchers classify T. lusitanicus as a telephagic tunneller. This species has been observed transporting dung up to several meters away from its original deposition site, where it then nests 10–15 cm deep. Dung beetles store dung underground to reduce resource competition and increase the preservation of the dung itself. Since dung beetles lay their eggs within the dung, burying the dung also serves to protect developing larvae from predators. Female dung beetles sort and arrange the dung, while males transport it through the tunnel. Because T. lusitanicus requires adequate amounts of dung for reproduction, studies found that oak forests that had large populations of deer or cattle supported higher populations of T. lusitanicus. == Food resources ==

Diet Thorectes lusitanicus is remarkably different from the other dung beetles in the Palearctic region because it is polyphagous, meaning it feeds on many different types of food. While some tropical dung species consume carrion and fruit, Palaearctic dung beetles primarily consume the dung of herbivores and omnivores. Like other Palaearctic dung beetles, T. lusitanicus has exhibited specific dung preferences. In the case of this species, T. lusitanicus prefers rabbit dung over cow dung, which researchers hypothesize is related to the relatively low water content of rabbit dung. This has important implications for the conservation of oak forests in the Mediterranean, and researchers suggest that preservation of the interactions between T. lusitanicus and oak species is essential for Mediterranean forest conservation. == Life history ==

The life cycle of Thorectes lusitanicus starts between September and November. After burying the dung of herbivores (including deer, sheep, goats, rabbits, and cattle), females lay their eggs in the dung. After the offspring develop for 6-7 months, they emerge as adults in the spring. T. lusitanicus conserves energy in the heat and aridity of the summertime by going into a dormant state. They become active again in the autumn. == Physiology ==

Flight While most dung beetles have long flight wings and can fly several miles at a time, the entire Thorectes genus is apterous, meaning these species have lost their capacity to fly. Some researchers hypothesize that dry and arid conditions facilitated the adaptation of fused elytra, as this fusion reduces water loss and allows water to be utilized for continuous respiration, which is utilized as a mechanism of thermoregulation. Other researchers are interested in the evolutionary relationship between apterism and acorn consumption in Thorectes lusitanicus. They hypothesize that the apterism may have led to the selection of alternative mechanisms to elevate body metabolism, such as the inclusion of acorns in their diet. Recent phylogenetic evidence indicates that two other dung beetles in the Geotrupidae family also consume acorns: Thorectes baraudi, a close relative of T. lusitanicus, and Mycotrupes lethroides, a very distant relative of T. lusitanicus. Since the three species are not all closely related yet all are apterous, this may provide evidence that apterism can lead to shifts in diet. Olfaction Insects heavily rely on their olfactory sense to detect and locate food. Laboratory experiments with Thorectes lusitanicus indicate that this species utilizes antennae chemoreceptors when searching for acorns. These experiments also revealed that this acorn selection is mediated by the volatile compound emitted by the acorns since T. lusitanicus was still capable of selecting acorns when the odor is mixed with dung odors. == Gut microbiome ==

Researchers have identified over 220 phenotypically different colonies of bacteria within the gut of T. lusitanicus. As symbiotic relationships between the insect gut and various microbes are crucial in facilitating polyphagy in many insect groups, it is unsurprising that the gut microbiome of this polyphagous beetle species contains a rich diversity of culturable bacteria. Enterobacterales, which have been found in the gut of T. lusitanicus, ensure amino acid synthesis by fixing nitrogen during the reproductive and diapause periods of adults and thus facilitate the acorn consumption of T. lusitanicus. Furthermore, this diazotrophic community may also detoxify the phenolic compounds within the acorns, which again permit their consumption by T. lusitanicus. Actinobacteria, which are considered defensive symbionts in insects as they produce products with antibiotic properties, have also been found within the gut of T. lusitanicus.Studies on desert locusts have shown that gut microbiome diversity is positively correlated with resistance to pathogenic bacteria invasion, leading researchers to suggest that individual T. lusitanicus who consume acorns may have higher survival rates than those who consume only dung. Firmicutes genera, including Bacillus and Lactobacillus, have also been found in the gut of T. lusitanicus. Researchers hypothesize that these genera may also be related to the polyphagy of this species. == Threats ==

A common livestock veterinary medicine, Ivermectin, poses a serious threat to Thorectes lusitanicus. Laboratory studies have indicated that when adult T. lusitanicus is exposed to non-lethal doses of ivermectin, it is biomagnified leading to acute toxicity within the beetles. When T. lusitanicus consumes dung containing ivermectin, it can alter the ovaries' morphology and decrease beetle fecundity. Even at low doses, ivermectin has been observed to have serious effects on T. lusitanicus sensorial and locomotor capacities. ==References==