Parasitoids physiology, development and behaviour | Boln. Asoc. esp. Ent. 21 (Supl.): 70-71 | 1997
Antennal tyloids are reléase structures of sex recognition pheromone in Pimpla turionellae (L.) (Hymenoptera, Ichneumonidae)
N. Isidoro, F. L. Wáckers, R. Romani.& F. Bin
ABSTRACT
Parasítica have antennomeres with tyloids which appear like keels or plates of different size and shape, so far inteipreted as sensory organs. The functional morphological study of these structures in Pimpla turionellae (L.) has revealed, for the fírst time in ichneumonids, that they are the reléase site of integumentary glands,
The male antenna consisting of 33 apparent aníennomeres has on the lateroventral side of the 8th and 9th antennomere tyloids consisting of longitudinally linear raised áreas with pores surrounded by some short hairs. Ultrastructural observations show that the numerous pores reléase the secretion produced by isolated bicellular secretory units. Each gland has a class 3 secretory cell, fonning a cuticular receiving canal, and a canal cell, fonning the conducting canal which connects the receiving canal to the external glandular opening. The short hairs delimiting the tyloids are innervated by a single sensory neuron ending in a typical tubular body with a tactile function.
In taxa other than ichneumonids these structures are involved in sex recognition. Behavioral observations show that once a male has detected the presence of a female, he pursues her and attempts to mount. During mounting, the male tries to stroke bis antennae against the antennae of the prospective mate. This behaviour is usually sustained for several seconds, at a rate of about four strokes per second per antenna. Jn some cases when the female seems uncooperative initially, it was observed that the antennal stroking extinguished her escape behaviour. The receptive female holds the antennae vertically with an angle of 70o- 90° between themr while the male bends its antennae from the outside around the female antennae. The male trien rapidly strokes the ventral side of its antennae against the ventral side of the female antennae, starting from 1/4 to 1/2 (calculated from the antennal base) up to the female antennal tip. During this stroking the contact área on the male antennae is restricted to approximately 3/4 of the antennal length (calculated from the antennal base). This corresponda to male antennomeres 7 to 15. After copulation the antennal stroking ceases.
These data suggest that tyloids are structures for releasing and spreading a recognition and/or aphrodisiac pheromone onto the female antennae during courtship.
