Caste-specific maturation of the endocrine system in the female honey bee larva

Abstract

The endocrine system of female honey bee larvae has been studied through postembryonic development with histological and autoradiographic techniques. During larval development, brain and retrocerebral complex proceed from immature cells to an active endocrine system. Caste-specific retardation occurs in the worker during this process. In the developing queen, the differentiation of the neurosecretory cells (NSC) and the outgrowth of their axons occurs from the second instar onward and is nearly completed in the fourth, whereas in the worker larva these processes are delayed by more than one instar. In the queen, RNA synthesis starts in the NSC at the end of the third instar and in the worker at the fifth instar. Stainable neurosecretory material is present only in fifth instar queen larvae. The queen's corpora cardiaca become active at the end of the fourth, those of the worker in the fifth instar. In the corpora allata (CA), nuclei undergo several phases of endomitosis. These phases of polyploidization end at the beginning (queen) or at the end (worker) of the fifth instar respectively. CA volume in the queen is twice that of a worker at its height at the end of larval development. these data demonstrate a caste-specific maturation of the endocrine organs which results in differences in hormone titres.

Epigenetic integration of environmental and genomic signals in honey bees: the critical interplay of nutritional, brain and reproductive networks

“…We reasoned that if methylation was repeatedly used to direct developmental processes, interfering with its role by elimination of a key component was likely to have a strong effect on the phenotypic development of larvae. Since larval growth is based on rapid increase in cells sizes associated with extremely high level of DNA replication, but virtually no cell division, 21,22 we did not expect any perturbed CpG methylation to be lethal to the larva. Indeed, interfering with CpG methylation by silencing the expression of the Dnmt3 gene in newly born larvae did not prevent larval growth, but lead to a profound shift in the developmental trajectory.…”

The ontogenetic saga of a social brain

“…These differences promote the establishment of caste-specific hormonal environments, which in turn drive the expression of different groups of effector genes (Ulrich and Rembold 1983;Hartfelder and Engels 1998;Barchuk et al 2007;Maestro et al 2009;Mutti et al 2011;Moda et al 2013). These may be considered to be the molecular responsible for the development of the initially larger brain seen in queen larvae.…”

Polyphenism in insects and the juvenile hormone

“…It remains to be investigated in what way feeding regulates the functioning of CA." Ulrich and Rembold (1983) studied maturation of the endocrine system in female honeybee larvae. They noted that polyploidization of CA cells through endomitoses is complete at the beginning of the fi fth instar in a queen larva and at the end of the fi fth instar in a worker larva.…”