Sperm ultrastructure and spermatodesm morphology of the spittle bug Locris transversa (Thunberg 1822) (Hemiptera: Cercopidae)

Abstract

The structure of the spermatozoon and spermatodesm of the spittlebug Locris transversa (Thunberg 1822) was investigated by light and transmission electron microscopy. Males produced only one size class of sperm, which was 93–106 μm long. During spermatogenesis groups of spermatozoa are arranged around, and attached by their acrosomes to, a small central extracellular matrix to form a ball-shaped spermatodesm. Spermatodesmata were found in the testis, vas deferens and seminal vesicle of males and spermatheca of females. The sperm are filiform, each consisting of a ~15-μm-long head containing an anteriorly positioned conical ~2-μm-long acrosome and ~13-μm-long nucleus, and a midpiece and tail with a 9+9+2 axoneme. The acrosome, which has two posterior extensions that lie along one side of the anterior region of the nucleus, contains longitudinally orientated microfilaments. The nucleus has two unequal anterior extensions, whereas posteriorly it is flattened laterally to accommodate a putative centriolar adjunct and anterior ends of the two mitochondrial derivatives. The basal body lies posterior to the nucleus. The mitochondrial derivatives are elongated and extend for almost the entire length of the tail. The tail has glycogen within its centre, and towards its terminal end large deposits of glycogen surround the mitochondrial derivatives and axoneme. Compared to other members of the Cicadomorpha, the spermatozoa and spermatodesms of cercopids so far studied have some structural features in common with cicadellids and others in common with cicadas; therefore, if sperm features are to be useful in phylogenetic studies of cicadomorphs, attention must be given to examining key taxa to establish which character states are plesiomorphic or apomorphic.