In the water strider Aquarius remigis (Say), sexual selection favours males with longer genitalia. We used video analysis plus light and scanning electron microscopy to examine the structure, movement, and articulation of the genitalia as a first step in determining the functional basis of this selection. Male A. remigis are characterized by long, robust genital segments; a marked ventral median notch in the posterior margin of the pregenital segment; an enlarged phallus tipped with a uniquely prolonged sclerotized plate; and a large, spine-covered, membranous lobe that inflates within the female's reproductive tract. Detailed examinations of genital interactions prior to and during copulation allow us to deduce the functional significance of these distinguishing traits. We postulate that by increasing the length, mobility, strength, and rigidity of the phallus, the first three traits increase the ability of males to achieve intromission in spite of active female resistance, and to maintain intromission during the prolonged copulations characteristic of this species. Inflation of the large, spinous lobe probably contributes to the latter function, and may also directly affect fertilization success by displacing or damaging sperm from previous males. We discuss these interpretations in the context of current theories of genitalic coevolution and sexual conflict in the Gerridae.
Four types of trichoid sensilla were described on the ovipositor of the spruce budworm, Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae). Types I and III sensilla were short and long multiporous hairs, respectively. Type IV sensilla were long and aporous. Each was innervated by a single dendrite. Type II sensilla were multiporous and also had a single terminal pore. They were innervated by four dendrites. Electrophysiological responses were obtained from these type II sensilla to a range of chemical stimuli.Résumé : Quatre types de sensilles chétiformes etaient présents sur l'ovipositeur de la tordeuse des bourgeons de l'épinette Choristoneura fumiferana (Clem.) (Lepidoptera : Tortricidae). Les sensilles des types I et III étaient des soies multipores; celles de type I étaient courtes et celles de type III longues. Les sensilles de type IV etaient longues, mais sans pores. Ces trois types de sensilles abritaient tous un seul dendrite. Les sensilles de type II étaient multipores, mais elles avaient aussi un seul pore terminal et elles abritaient quatre dendrites. Avec l'électrophysiologie, nous avons dé-monté que les sensilles de type II réagissaient à divers produits chimiques. Banga et al. 2037
The ultrastructure of the osmoregulatory cells in the integument of the stonefly nymph, Paragnetina media, shows changes in media hypotonic, isotonic, and hypertonic to the hemolymph. Exposure to hypotonic concentration results in an increase in the plasma membrane folds, mitochondria, and microtubules in the cytoplasm. In isotonic and hypertonic concentrations, the cells show cellular disorganization and apparent loss in their function. These results suggest that the structural changes in the osmoregulatory cells are related to the osmotic condition of the medium, and these cells probably act as extrarenal sites for the absorption of ions from the hypoosmotic medium.
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