The nature and development of sex attractant specificity in cockroaches of the genus Periplaneta. II. Juvenile hormone regulates sexual dimorphism in the distribution of antennal olfactory receptors

Abstract

Sexual dimorphism of antennal sense organs appears only at the adult stage during normal development of the cockroach, Periplaneta arnericana. Adult males acquire approximately twice as many olfactory sensilla as females at the terminal ecdysis. When terminal instar larvae are subjected to unilateral antennectomy, most ecdyse to supernumerary larvae rather than adults. Sexual dimorphism is not evident in the intact (unamputated) antenna during the extra larval stage, but appears at the following ecdysis which leads to the adult stage. Allatectomy of male and female larvae in the penultimate instar produces adultoids which show antennal sexual dimorphism. Whole-body treatment of terminal instar larvae with exogenous juvenile hormone-mimic (JH-M) results in supernumerary larvae which lack antennal sexual dimorphism. When these superlarvae are removed from the influence of JH-M, they ecdyse to adults with antennal sexual dimorphism. Topical application of JH-M to male antennae early in the terminal larval instar results in the emergence of adults which lack the total male complement of antennal sensilla, but are otherwise normal-appearing. These results indicate that an inhibitory action of juvenile hormone prevents the appearance of antennal sexual dimorphism during normal larval development.The postembryonic development of antennal olfactory receptors in cockroaches is regulated, in part, by the juvenile hormone (JH) (Schafer and Sanchez, '74). In the African woodroach, Leucophaea maderue, the density of antennal olfactory sensilla remains constant at about 400 sensilla per mm2 during each stage of larval development, because olfactory sensilla are added at each ecdysis in direct proportion to the increase in antennal surface area. However, at the terminal ecdysis leading to the adult stage, the density of olfactory receptor organs increases to 620 sensilla per mm2 in both males and females. Exogenously applied juvenile hormonemimic (JH-M) prevents this increase; or, the increase can be induced precociously by removing the corpora allata, endocrine organs which produce juvenile hormone in larval insects (Schafer and Sanchez, '74).J. EXP. UXIL., 198: 323-336.We chose to perform similar experiments on the American cockroach, Periplaneta americana, since the antennae show distinct sexual dimorphism related to the pheromone-dependent sexual behavior of males of this species. For example, the initial step in courtship behavior of P. americam is the male's reception of a femaleproduced sex attractant (Roth and Willis, '52; Barth, '70; Simon, '71). Of particular interest was the possibility that the differentiation of sex attractant receptors is inhibited by juvenile hormone during larval development. There are approximately twice as many olfactory sensilla on adult male P. americana antennae as on adult female antennae (Schafer and Sanchez, '73). In contrast, no sexual dimorphism is seen in the antennae of Leucophaea at any

Two types of sensory proliferation patterns underlie the formation of spatially tuned olfactory receptive fields in the cockroach Periplaneta americana

“…The transformation from sw‐ A to sw‐ B sensilla specifically occurred at the final molt and led to sexual dimorphism of the adult antenna. In the cockroach, surgical removal of the corpora allata and application of juvenile hormone (JH) to males in the LI stage indicated that JH prevents the appearance of antennal sexual dimorphism (Schafer & Sanchez, ). This suggests that the transformation from sw‐ A to sw‐ B sensilla might be controlled by JH state.…”

“…Olfactory sensilla and OSNs emerge concomitantly with the addition of new flagellomeres to the proximal end of the flagellum (Schafer & Sanchez, ). The cockroach becomes adult via 11 molts from the first instar (Schafer & Sanchez, , ). In the AL of the cockroach, all glomeruli are already present at the first instar and the sensory axonal entries to individual glomeruli are conserved from the first instar to adult, while their volumes increase due to increased sensory inputs at every molt (Nishino, Yoritsune, & Mizunami, , ; Prillinger, ).…”

Postembryonic development of sexually dimorphic glomeruli and related interneurons in the cockroach Periplaneta americana

“…This leads to "sexual dimorphism" in neural pathways for pheromone-processing. For example, the adult male antennae are characterized by a larger number of sensilla housing pheromone-receptive neurons than the adult female antennae [20,21].…”

“…In contrast, adult females retain nymph-like shorter type sw B sensilla [21]. The topical application of juvenile-hormone-mimic to the male antenna in late larval instars prevents both differentiation of shorter type sw B sensilla and the increase in number of male-specific sensilla [20] suggesting an inhibitory action of juvenile hormone to the formation of male-specific sensilla.…”

Pheromone Detection by a Pheromone Emitter: A Small Sex Pheromone-Specific Processing System in the Female American Cockroach

“…Maturation of the male B-PN may be achieved by extension of additional branches to the anterodorsal region of the lateral horn. It has been shown that formation of male-specific long single-walled B sensilla is promoted by suppression of juvenile hormone released from corpola allata (Schafer and Sanchez 1976). The effect of juvenile hormone stimulation on development of the male B-PN needs investigating because this would answer how the neural circuits that control sex-specific behaviors are remodeled during postembryonic development in this primitive slowly developing insect.…”