Radula formation and development in Limapontia senestra (Quatrefages, 1844) (Heterobranchia, Gastropoda) from the White Sea

Abstract

Sacoglossa is a monophyletic group of small suctorial herbivorous Нeterobranchia. Due to the biology of feeding, most sacoglossans (except Cylindrobulla) have a distinctive feeding apparatus, which includes a sucking muscular organ as well as a sacoglossan-type radula with one tooth in a transverse row, which pierces algal cells. Although there is obvious interest in the radular morphology and developmental modes of Sacoglossa, as these characters may provide some insight into the evolutionary history and phylogenetic relationships of Sacoglossa, data on radula formation and morphogenesis in this group are sparse. This paper presents original data on the direct development, formation, and morphogenesis of the radula of Limapontia senestra (Quatrefages, 1844) from the White Sea. Based on the data obtained, we describe the development and formation of the radula. They fit into the general pattern of heterochrony in the radula anlage, characteristic of all gastropods. The small number of odontoblasts in the formation of the adult radula of L. senestra is a distinctive feature of the radula of Heterobranchia.