GEOGRAPHICAL-DISTRIBUTION, HOSTS AND BIOLOGICAL CHARACTERISTICS OF TROPHONEMA-OKAMOTOI (NEMATODA, TYLENCHULIDAE)

Trophonema okamotoi populations from Florida showed intraspecific morp hometric variability and did not differ from those from Costa Rica and Venezuela. Swollen females of these populations had tapering tails wi th bluntly rounded or small rounded termini like those of T. okamotoi paratypes from Japan and unlike the pointed or minutely digitate tail termini of T. arenarium paratypes from California. Hosts of T okamotoi were Liquidambar styraciflua and an uncultivated tropical grass in Fl orida, and Gyranthera caribensis in Venezuela. At 22 +/- 2-degrees-C e mbryogenic development of T. okamotoi was completed in 14 days and the first-stage juvenile moulted in the egg 16 days after egg deposition. Swollen females, males, second-stage juveniles, and eggs (50-120 eggs per female) were covered by a soft or hardened gelatinous matrix, whi ch was produced by the secretory-excretory cell, and exuded through th e secretory-excretory pore. Histological observations of L. styraciflu a and tropical grass roots infected by T. okamotoi showed this species to be a cortical feeder. Females penetrated the epidermis of L. syrac iflua roots and also 5-6 cortical layers in the roots of the tropical grass. They established a syncytium in the cortex.