Biologia e desenvolvimento de galhas de Neotrioza cf. tavaresi Crawf.(Hemiptera: Psylloidea) na superhospedeira Psidium myrsinoides O. Berg (Myrtaceae)

Abstract

Insect galls are the result of specific interaction between an inducer and its host-plant, in which the parasite obtains shelter and nutrition. The growth of the structure is coordinated by the gall inducer, which manipulates plant tissues for their own benefit. During this process, there may be accumulation of substances from the primary and secondary metabolism in the tissues of the gall, being this accumulation the result of the physiological impact of the feeding action of the gall inducer on the host tissues. In the gall, these substances are used for nutrition and protection of the insect as well as to maintain the newly-formed structure. To the system Psidium myrsinoides O. Berg (Myrtaceae) - Neotrioza cf. tavaresi (Hemiptera: Psyllidae) the diversity of galls associated with P. myrsinoides and the biology Neotrioza cf. tavaresi were notified, focusing on phenology, relations with other trophic levels and macroscopic characteristics of the galls. Still, we reported the structural changes resulting from the induction of galls, besides physiological and histochemical aspects. Neotrioza cf. tavaresi has five instars and univoltine annual life cycle, with high synchrony with the phenology of P. myrsinoides. The increase in volume of the galls was proportional to the gall insect growth, which, throughout the year, had parasitism and mortality rates of 15.7% and 29.8% respectively. The red color of the gall could be related to the non parasitized inductor being an important character of macroscopic diagnosis. The development of non galled leaves was common to simple leaves. In gall, the epidermis is derived from the inner and outer protoderm, the inner cortex from the adaxial meristem, the cortex is derived from the median meristem and outer cortex is derived from the abaxial meristem. The increased thickness of the mesophyll due to hyperplasia and hypertrophy, together with tissue lignification, increase the protection of the galler against natural enemies. The neo formation of vascular bundles near the gall chamber increases their feeding sites, while the essential oil glands on the outside possibly repel the action of pathogens, parasitoids or cecidophagus. The direction of cell elongation and cell division patterns of each layer in the gall were essential in determining the final shape of the structure. Still, the galls showed a low concentration of chlorophylls, carotenoids and anthocyanins indicating an impairment of the photosynthetic apparatus in the structure, a fact corroborated by the low total nitrogen content. The high carbohydrate content, in turn, validates the claim of being the galls stronger sinks of photoassimilates. It was observed the formation of an anatomical and physiological continuum between the leaf and the gall, as the nutritional options of the insect and its protection against natural enemies progressively increase from the leaves towards the gall. The features related to the system Psidium myrsinoides - Neotrioza cf. tavaresi bring new perspectives and approaches that can be investigated more deeply in the ecological, anatomical, physiological and chemical areas. Many of the characteristics found corroborate standards already set for development and physiology of Neotropical galls induced by sucking-insects, while others, because they are different, show the uniqueness and specificity of the relationship between the galling insect and its host plant