No abstract

The capability of the attine ant, Acromyrmex octospinosus, to digest chitin was studied. β-N-Acetylglucosaminidase, chitobiase, and chitinase activities of labial gland extracts were demonstrated. The biochemical characteristics (pH optimum, Michaelis constant, temperature influence) were investigated and the results are discussed in comparison with published data. The absence of microflora in the labial glands suggests the direct production of the chitinolytic system by labial glands. Its function in the digestion of the chitinous symbiotic fungus walls was examined. Effective degradation of this fungal material has been demonstrated in the infrabuccal pocket. Acromyrmex octospinosus appears to have adapted to a fungus diet by synthesis of specific enzymes. This result is discussed in relation to a previous hypothesis concerning mycophagous insects. Some hypotheses regarding the role of the chitinolytic activities are formulated.

Some vertebrate species in Guadeloupe are predators of free or parasitic stages of Amblyomma variegatum (Fabricius). Among birds, 1.9% of the 421 identified animals found in the stomachs of grackles (Quiscalus lugubris), 1.6% of the 364 animals found in the stomachs of free-ranging chickens, and 0.3% of the 4642 animals found in the stomach of cattle egrets (Bubulcus ibis) were A. variegatum ticks. The most efficient predator of ticks was the tropical fire ant, Solenopsis geminata, which was observed to only attack engorged stages of ticks. An average of 8% of the 564 individual ticks or batch of ticks released on the ground, mainly in a grass environment, were attacked by this ant species. Mice (Mus musculus) and mongooses (Herpestes auropunctatus) feed on engorged nymphs and female ticks. None of the 15 strains of entomophagous nematodes, genera Steinernema and Heterorhabditis, experimentally put in contact with engorged larvae and nymphs were able to parasitize them. In the laboratory, the insects Megaselia scalaris (Diptera) and Tineola sp. (Lepidoptera) were occasionally found to feed on engorged and unfed ticks, respectively.

No abstract

Description de Ichthyocephalus anadenoboli n. sp. (Rhigonematidae ; Nematoda) trouvé sur Anadenobolus politus (Porat). (Rhinocricidae ; Diplopoda) provenant de Guadeloupe. La nouvelle espèce ressemble plus particulièrement à I. egleri du fait que les deux sexes sont à peu près de même taille et les spicules très inégaux ; elle s'en distingue par le spicule droit beau coup plus long, par la forme de l'extrêmité du spicule gauche et par l'existence d'un sac vaginal débouchant dans le vagin, à la jonction avec les utérus. Certains aspects de la spermiogénèse de la nouvelle espèce sont étudiés. La maturation des spermatides se déroule suivant deux phases, la première ayant lieu dans le testicule et le réceptacle séminal du mâle, la seconde dans le sac vaginal de la femelle. Au cours de cette seconde phase la forme du spermatide subit de profonds changements en même temps que se transforme son noyau. On peut supposer que le sac vaginal observé chez certaines espèces de Rhigonema et la bourse copulatrice de certains Tetrameres et de Maupasina weissi sont, comme dans le cas de I. anadenoboli, des organes spécialisés pour favoriser les derniers stades de la spermiogénèse.