Carbon dioxide levels and ventilation in Acromyrmex nests: significance and evolution of architectural innovations in leaf-cutting ants

Leaf-cutting ant colonies largely differ in size, yet all consume O 2 and produce CO 2 in large amounts because of their underground fungus gardens. We have shown that in the Acromyrmex genus, three basic nest morphologies occur, and investigated the effects of architectural innovations on nest ventilation. We recognized (i) serial nests, similar to the ancestral type of the sister genus Trachymyrmex , with chambers excavated along a vertical tunnel connecting to the outside via a single opening, (ii) shallow nests, with one/few chambers extending shallowly with multiple connections to the outside, and (iii) thatched nests, with an above-ground fungus garden covered with plant material. Ventilation in shallow and thatched nests, but not in serial nests, occurred via wind-induced flows and thermal convection. CO 2 concentrations were below the values known to affect the respiration of the symbiotic fungus, indicating that shallow and thatched nests are not constrained by harmful CO 2 levels. Serial nests may be constrained depending on the soil CO 2 levels. We suggest that in Acromyrmex , selective pressures acting on temperature and humidity control led to nesting habits closer to or above the soil surface and to the evolution of architectural innovations that improved gas exchanges.

Comparative analysis of mandible morphology in four ant species with different foraging and nesting habits

Mandibles of ants can be considered as one of the most vital tools for the survival and success of their colonies since these are extensively utilised for defence, nest maintenance and foraging activities. We hypothesised that mandibular design is strongly dependent on the respective ecological niche and foraging habit of an ant species. In the present study, we compared the external morphology and zinc content in the mandibles of four species of ants by using scanning electron microscopy and energy dispersive X-ray spectroscopy. The ant mandible morphology varied significantly in accordance with their species-specific foraging and nesting strategies. The sickle-shaped mandibles of the strongly predaceous, Oecophylla smaragdina worker ants were characterised by a large number of pointed teeth which would be of immense utility for subduing the prey, while the shovel-shaped, highly sclerotized mandibles of Cataglyphis longipedem ants appear to be adaptations for the solitary scavenging habit and nest maintenance in arid habitats. The large-sized mandibles of Camponotus compressus ants and the stout mandibles of the predatory, Tetraponera rufonigra forager ants, have apparently evolved for collection of sugary secretions by the former and for the solitary foraging and arboreal nesting habit of the latter. The mandibular zinc content was highest in T. rufonigra ants and the lowest in the mandibles of the sugar-loving Cm. compressus ants. The diversity in the arrangement of bristles and the type of mandibular concavities, have also evolved accordingly. Thus, this study might prove to be instrumental in evaluating the various physical mechanisms involved in the evolution of insect mandibles for their defined function.

Co-occurrence in ant primary parasitoids: a Camponotus rectangularis colony as host of two eucharitid wasp genera

Different assemblages of parasitoids may attack a given host species and non-random distribution patterns in parasitoid species assemblages have been reported on various occasions, resulting in co-occurrence at the population, colony, or even individual host levels. This is the case for different closely related species of eucharitid wasps (a family of specialized ant parasitoids) sharing similar niches and co-occurring on the same host at different levels. Here we reviewed all known associations between eucharitid wasps and the ant host genus Camponotus Mayr, 1861 and reported new ant-parasitoid associations. In addition, we report a new case of co-occurrence in eucharitid wasps, at the host colony level, involving a new undescribed species of Pseudochalcura Ashmead, 1904 and an unidentified species of Obeza Heraty, 1985, which attack the common but very poorly known neotropical arboreal ant Camponotus rectangularis Emery, 1890. Most attacks were solitary, but various cocoons were parasitized by two (16%) or three (8%) parasitoids. Globally, parasitism prevalence was very low (3.7%) but showed an important variability among samples. Low parasitism prevalence along with host exposure to parasitoid attack on host plants and overlapping reproductive periods of both parasitoid species may have allowed the evolution of co-occurrence. We also provided some additional data regarding the host ant nesting habits, the colony composition and new symbiotic associations with membracids and pseudococcids. The seemingly polydomous nesting habits of C. rectangularis could play a part in the reduction of parasitism pressure at the population level and, combined with occasionally important local parasitism rates, could also contribute to some parts of the colonies escaping from parasites, polydomy possibly representing an effective parasitism avoidance trait.

Natural history of two carpenter ants, Camponotus renggeri and C. rufipes (Hymenoptera: Formicidae), in an Atlantic Forest reserve

Widespread species face a wide variety of environmental challenges and their morphology, behavior, and natural history may change across their range. However, not rarely, natural history research is restricted to one or few locations. That is the case for Camponotus renggeri and C. rufipes. Both species occur across South America in different ecosystems, but most research on these species is restricted to the Brazilian savanna, known as Cerrado. Here, we describe the home range, nesting habits, and activity schedule of C. renggeri and C. rufipes in an Atlantic Forest reserve in SE Brazil. C. renggeri foraged exclusively during nighttime and C. rufipes remained active throughout the nycthmeron, but with little intensity during daylight hours. Most nests of both species were composed of dry straw, and home ranges varied from nearly 0.91 m2 (C. renggeri) to 1.79 mm2 (C. rufipes). Foraging areas overlapped, especially in C. renggeri. Our field study reinforces the importance of natural history and what it adds to our knowledge on the ecology and behavior of C. renggeri and C. rufipes in Atlantic Forest.

First report of Megachile (Callomegachile) sculpturalis Smith, 1853 (Apoidea: Megachilidae) from India

The giant resin bee, Megachile (Callomegachile) sculpturalis (Smith, 1853) is an invasive solitary bee that has spread all over North America and Europe in the last decade. Although native to Asia, not much is known about its distribution in this continent. In the present study, Megachile (Callomegachile) sculpturalis is reported for the first time from India. Related information about this species regarding its nesting habits, floral association, and impact in introduced range obtained through bibliographical research along with the possible dispersal route after introduction in South Eastern Asia is provided. The checklist of Megachile (Callomegachile) in India is also provided. Key words: Pollinator, giant resin bee, range extension, Northeast India

Blood Parasites in Sympatric Vultures: Role of Nesting Habits and Effects on Body Condition

Avian haemosporidians are a common and widespread group of vector-borne parasites capable of infecting most bird species around the world. They can negatively affect host condition and fitness. Vultures are assumed to have a very low prevalence of these blood parasites, likely due to their strong immunity; however, factors contributing to variation in host exposure and susceptibility to haemosporidians are complex, and supporting evidence is still very limited. We analyzed blood samples collected from nestlings of three vulture species in Spain over 18 years, and used updated nested-PCR protocols capable of detecting all haesmosporidian cytochrome b lineages typical for diurnal birds of prey (Accipitriformes). Similarly to previous studies, we found low haemosporidian prevalence in cliff-breeding species, with Leucocytozoon as the only represented blood parasite genus: 3.1% in griffon vultures (Gyps fulvus) (n = 128) and 5.3% in Egyptian vultures (Neophron percnopterus) (n = 114). In contrast, the tree-breeding cinereous vulture (Aegypius monachus) had a substantially higher prevalence: 10.3% (n = 146). By far the most common lineage in Spanish scavenging raptors was the Leucocytozoon lineage CIAE02. No effects of nestling age and sex, or temporal trends in prevalence were found, but an effect of nest habitat (tree-nest vs. cliff-nest) was found in the griffon vulture. These patterns may be explained by a preference of vectors to forage in and around trees rather than on cliffs and wide open spaces. We found an apparent detrimental effect of haemosporidians on body mass of nestling cinereous vultures. Further research is needed to evaluate the pathogenicity of each haemosporidian lineage and their interaction with the immune system of nestlings, especially if compromised due to pollution with pharmaceuticals and infection by bacterial and mycotic pathogens.

Baby tyrannosaurid bones and teeth from the Late Cretaceous of western North America

Tyrannosaurids were the apex predators of Late Cretaceous Laurasia and their status as dominant carnivores has garnered considerable interest since their discovery, both in the popular and scientific realms. As a result, they are well studied and much is known of their anatomy, diversity, growth, and evolution. In contrast, little is known of the earliest stages of tyrannosaurid development. Tyrannosaurid eggs and embryos remain elusive, and juvenile specimens — although known — are rare. Perinatal tyrannosaurid bones and teeth from the Campanian–Maastrichtian of western North America provide the first window into this critical period of the life of a tyrannosaurid. An embryonic dentary (cf. Daspletosaurus) from the Two Medicine Formation of Montana, measuring just 3 cm long, already exhibits distinctive tyrannosaurine characters like a “chin” and a deep Meckelian groove, and reveals the earliest stages of tooth development. When considered together with a remarkably large embryonic ungual from the Horseshoe Canyon Formation of Alberta, minimum hatchling size of tyrannosaurids can be roughly estimated. A perinatal premaxillary tooth from the Horseshoe Canyon Formation likely pertains to Albertosaurus sarcophagus and it shows small denticles on the carinae. This tooth shows that the hallmark characters that distinguish tyrannosaurids from other theropods were present early in life and raises questions about the ontogenetic variability of serrations in premaxillary teeth. Sedimentary and taphonomic similarities in the sites that produced the embryonic bones provide clues to the nesting habits of tyrannosaurids and may help to refine the prospecting search image in the continued quest to discover baby tyrannosaurids.

Additional notes on the life history of the Tagula Honeyeater Microptilotis vicina in Papua New Guinea

We revisited a location to study previously individually marked Tagula Honeyeaters Microptilotis vicina in 2019, 3 years after the original 2016 study on Junet Island, Louisiade Archipelago, Papua New Guinea. Re-encountered Tagula Honeyeaters indicated sedentary behaviour across years and an average annual adult survival rate of ≥0.75. We made the first observations of building and laying at two nests, and recorded nesting habits in the species. Tagula Honeyeaters showed the general trend in the honeyeater family of only the female building the nest and incubating. Nests were similar to those previously observed and to those of related species. Clutch-size in both nests was two and laying was on consecutive days. Eggs were white to off-white, with a ring of liver-brown spots and markings around the larger end. Incubation began on the day that the second egg was laid and lasted 14 days in both nests. Males visited the nest area only after the eggs hatched. At one nest, the nestling period was suspected to be 12 days. These limited observations of the only endemic island representative in Microptilotis indicate that, like plumage characters, breeding parameters remain similar within the genus.