External morphology and anatomy of the foliar bivalve gall induced by Rhopalomyia sp. (Diptera: Cecidomyiidae) on Prosopis caldenia (Fabaceae).

Abstract

External morphology and anatomy of the foliar bivalve gall induced by Rhopalomyia sp. (Diptera: Cecidomyiidae) on Prosopis caldenia (Fabaceae). An undescribed species of Rhopalomyia (Diptera: Cecidomyiidae) induces galls on the leaves of Prosopis caldenia. The aims of this work are: to describe the external morphology of these galls, to differentiate its developmental stages and to describe the modifications induced on the foliar tissues. Normal and galled leaves were collected between February 2014 and November 2015 in a fragment of P. caldenia forest located in a peri-urban area in Santa Rosa, La Pampa, Argentina. The external morphology of the gall was studied by dissecting some galls under the stereomicroscope. Gall tissues were examined in temporal and permanent microscopic slides containing free hand and microtome sections respectively. The gall is composed of two coalescent adjacent leaflets, originating a bivalve and unilocular structure, with bilateral symmetry, containing the larva of the inducer. The gall presents a continuous layer of nutritive tissue covering the inner wall of the larval chamber, and also has protective and support tissues derived from epidermal and parenchymatic cells modified as sclereids. The tissue that suffers the most important modification is the foliar epidermis.