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Ecological Section

Moraru, Corina [1], Maier, Camelia G.-A. [1].

Effectof Mulberry Mineral Depositson the Developmentand Performanceof Silkworm.

Plants have evolved both constitutive and inducible strategies to defend themselves against herbivores. Previous studies in our laboratory showed that female leaves contain significantly higher levels of oxalate and calcium depositions than male leaves of mulberry, Morus alba, Moraceae, the only natural food for silkworms, Bombyx mori. We used the mulberry/silkworm system, a specialist insect herbivore system, to investigate the impact of the above characteristics of sexual dimorphism in mulberry on larval feeding and development. Length and weight of individual caterpillars were estimated in two populations of silkworms, one fed exclusively with male mulberry leaves, the other one fed exclusively with female leaves, and feeding behavior on male and female leaves was observed. Not only that silkworms performed better on male than female mulberry leaves, but also they preferred male to female leaves. Total time of feeding on male leaves was twice as long as that of feeding on female leaves. Development was delayed for silkworms raised exclusively on female leaves. Although both male and female mulberry leaves contain same types of mineral depositions, calcium carbonate lithocysts, and calcium oxalate druses and prismatic crystals, at the same anatomical location, insoluble oxalate concentrations and calcium carbonate deposits were significantly higher in female than male leaves (P= 0.033 and P=0.02 respectively, alpha=0.05). In free feeding experiments, silkworms avoided chewing on female leaf veins, which contained significantly higher concentrations of calcium oxalate deposits than the male veins. Silkworms preferred and performed better on male mulberry leaves possibly due to their low content of mineral depositions, oxalate, and phytoestrogen activity. Webworm caterpillars, Hyphantria cunea Drury also preferred male mulberry leaves to female ones and the adult female laid eggs on the abaxial side of the fresh female leaves. Our results suggest a constitutive defensive role for mineral deposition and phytoestrogens against insect pests.

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1 - Texas Woman's University, Department of Biology, Denton, Texas, 76204-5799, USA

sexual dimorphism
mineral deposits

Presentation Type: Poster
Session: 33-32
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM
Abstract ID:456

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