The reproductive morphology and physiological age-grading of female Cyrtobagous salviniae, the salvinia weevil
Over 1000 dissections were performed on field, greenhouse and lab specimens in order to describe the reproductive system of Cyrtobagous salviniae, a biocontrol agent of Salvinia molesta (giant salvinia). The reproductive morphology of C. salviniae was described, the classes of reproductive development were characterized, and oviposition assessed. The reproductive system of C. salviniae consists of two ovaries, each of which is comprised of two membraneous ovarioles. These are each divided into a distal germarium and a proximal vitellarium that is connected to a lateral oviduct. The lateral oviducts unite to form a common oviduct through which eggs must pass for oviposition to take place. A schlerotized spermatheca and accessory glands are also present. There are 5 classes of reproductive development, 2 nonparous (no oviposition) and three parous. These are differentiated primarily by the number and maturity of follicles in the vitellarium, the presence of eggs in the oviducts, and the presence or absence of follicular relics. The number of eggs oviposited was quantified by holding one hundred C. salviniae weevils individually on sprigs of salvinia at 29.5 ° C, with 12:12 daylength, and counting the number of ovipositions per weevil each week. During the course of the five month study, over 12,000 eggs were enumerated. At the end of the study, all of the weevils were dissected, basic statistics calculated, and the data analyzed by ANOVA, Tukey-Kramer, and Chi-square procedures (p=.0001). The mean number of eggs oviposited for each of the parous classes (i.e., P1, P2, and P3) were 22.6, 84.3, and 208.3, respectively. ANOVA indicated that mean egg numbers for each class were significantly different (F=176.51, P<.0001), and Tukey-Kramer analysis (P<.0001) showed that each of the three classes were significantly different from each other (P<.0001). Values obtained from the oviposition study were related to the reproductive classes to create a physiological age-grading system, which can be used as a reference to gain a deeper understanding of the population dynamics of this important biocontrol agent.