The inheritance of alternative nest architectural traditions in stingless bees

The transmission of complex behavior and culture in humans has long been attributed to advanced forms of social learning,1,2 which play a crucial role in our technological advancement.3 While similar phenomena of behavioral traditions and cultural inheritance have been observed in animals,1,2,4,5,6 including in primates,7 whales,8 birds,9 and even insects,10 the underlying mechanisms enabling the persistence of such animal traditions, particularly in insects, are less well understood. This study introduces pioneering evidence of enduring architectural traditions in the stingless bee Scaptotrigona depilis, which are maintained without any evidence for social learning. We demonstrate that S. depilis exhibits two distinct nest architectures, comprising either helicoidal or flat, stacked horizontal combs, which are transmitted across generations through stigmergy11,12,13,14,15,16,17-an environmental feedback mechanism whereby the presence of the existing comb structures guides subsequent construction behaviors-thereby leading to a form of environmental inheritance.18,19,20 Cross-fostering experiments further show that genetic factors or prior experience does not drive the observed variation in nest architecture. Moreover, the experimental introduction of corkscrew dislocations within the combs prompted helicoidal building, confirming the use of stigmergic building rules. At a theoretical level, we establish that the long-term equilibrium of building in the helicoidal pattern fits with the expectations of a two-state Markov chain model. Overall, our findings provide compelling evidence for the persistence of behavioral traditions in an insect, based on a simple mechanism of environmental inheritance and stigmergic interactions, without requiring any sophisticated learning mechanism, thereby expanding our understanding of how traditions can be maintained in non-human species.

Immune response in paper wasp workers: Task matters more than age

Workers of social hymenopterans (ants, bees and wasps) display specific tasks depending on whether they are younger or older. The relative importance of behavior and age in modulating immune function has seldom been addressed. We compared the strength of encapsulation-melanization immune response (hereafter melanotic encapsulation) in paper wasps displaying age polyethism or experimentally prevented from behavioral specialization. Foragers of Polybia paulista had higher melanotic encapsulation than guards, regardless of their age. Nevertheless, melanotic encapsulation decreased with age when wasps were prevented from behavioral specialization. Thus, in this species, worker melanotic encapsulation seems more sensitive to task than age. Foraging is considered one of the riskier behaviors in terms of pathogen exposure, so upregulating melanotic encapsulation in foragers can possibly improve both individual and colony-level resistance against infections.

Distinct Colony Types Caused by Diploid Male Production in the Buff-Tailed Bumblebee Bombus terrestris

The buff-tailed bumblebee Bombus terrestris presents two distinct colony phenotypes in which some colonies already start producing males very early in the season, while others switch to producing sexuals much later in the season, and specialize mainly in the production of virgin queens. Despite having been extensively investigated in the past, the mechanisms underlying these two distinct phenotypes remain poorly understood. Here we use a combination of behavioral and genetic data to demonstrate that early switchers are in fact diploid male producing colonies, while late switchers produced normal, haploid males. Hence, at a proximate level, early switching to male production was caused by queens mating with males that by chance carried the same sex allele. These patterns were not the result of strong inbreeding within the study population, as the average inbreeding coefficient was very low and in fact slightly negative (−0.11). Moreover, an effect of inbreeding was further excluded because hybrids produced by crossing two distinct outbred populations also produced diploid males in early switching colonies. Finally, we found that diploid males only emerged after a first cohort of workers was produced, while we would have expected diploid males to be produced simultaneously with workers in a 50:50 ratio. We demonstrate that adult diploid males had a distinct cuticular hydrocarbon profile and propose that queens likely cull diploid males during early colony development to reduce the cost of diploid male production.

Hormonal modulation of reproduction and fertility signaling in polistine wasps

In social insects, it has been suggested that reproduction and the production of particular fertility-linked cuticular hydrocarbons (CHC) may be under shared juvenile hormone (JH) control, and this could have been key in predisposing such cues to later evolve into full-fledged queen pheromone signals. However, to date, only few studies have experimentally tested this "hormonal pleiotropy" hypothesis. Here, we formally test this hypothesis using data from four species of Polistine wasps, Polistes dominula, Polistes satan, Mischocyttarus metathoracicus, and Mischocyttarus cassununga, and experimental treatments with JH using the JH analogue methoprene and the anti-JH precocene. In line with reproduction being under JH control, our results show that across these four species, precocene significantly decreased ovary development when compared with both the acetone solvent-only control and the methoprene treatment. Consistent with the hormonal pleiotropy hypothesis, these effects on reproduction were further matched by subtle shifts in the CHC profiles, with univariate analyses showing that in P. dominula and P. satan the abundance of particular linear alkanes and mono-methylated alkanes were affected by ovary development and our hormonal treatments. The results indicate that in primitively eusocial wasps, and particularly in Polistes, reproduction and the production of some CHC cues are under joint JH control. We suggest that pleiotropic links between reproduction and the production of such hydrocarbon cues have been key enablers for the origin of true fertility and queen signals in more derived, advanced eusocial insects.

Inheritance of seedlessness and the molecular characterization of the INO gene in Annonaceae

The inheritance of the seedless fruit characteristic of Annona squamosa has not yet been explained. Molecular techniques may aid breeding programs, mainly in the assisted selection of the target gene. The INO gene may be related to seed development in these fruits. The objective of the present paper was to investigate the inheritance of seedlessness in the 'Brazilian seedless' sugar apple and INO gene conservation in Annona squamosa and Annona cherimola x Annona squamosa genotypes by assessing their homology with the INO database genes. The F1 generation was obtained by crossing the mutant 'Brazilian seedless' (male genitor) (P1) with the wild-type A. squamosa with seeds (M1 and M2, female genitors). The INO gene was studied in mutant and wild-type A. squamosa (P1, M1, M2 and M3) and in the Gefner atemoya (A. cherimola x A. squamosa) (M4) cultivar. The DNA was extracted from young leaves, and four sets of specific primers flanking the INO gene were amplified. The seedless characteristic was identified as stenospermatic in the fruits of parental P1, suggesting monogenic inheritance with complete dominance. High sequence similarity of the INO gene amplifications in the sugar apple accessions (M1, M2, M3) and the atemoya cultivar Gefner (M4) reinforces the hypothesis of their conservation.

Clinical evaluation of hydroxyapatite-coated single-tooth implants: a 5-year retrospective study

The use of implants to replace missing single teeth has become a valuable treatment option. This study presents a 5-year retrospective clinical analysis of single teeth replaced with hydroxyapatite-coated implants. Of the 271 cylinder and screw implants placed over this period, 12 were lost (survival rate = 95.57%). In addition to aesthetic compromise, the most frequent complication was loosening of the abutment screw. These results corroborate findings from the literature and suggest that the described procedure can be safely performed in daily restorative procedures.

The production of hemicellulases by aerobic fungi on medium containing residues of banana plant as substrate

Trichoderma harzianum strains T4 and T6, Acrophialophora nainiana, and Humicola grisea var. thermoidea were screened for their ability to produce carbohydrate-degrading enzyme activities in a medium containing banana plant residue as the carbon source. The best balance of enzyme activities was obtained from cultures of H. grisea var. thermoidea. Xylanase activity from crude extract of A. nainiana had a maximum activity at pH 5.5-7.0 and a temperature range of 50-55 degrees C. It was stable up to 55 degrees C at pH 7.0 for at least 2 h. The fungi were also able to produce xylanase and pectinase activities when grown on extractives as substrate.