Ultrastructural investigation of coelomocytes in representatives of Naidinae and Rhyacodrilinae (Annelida, Clitellata, Tubificidae)

Abstract

Various types of free-floating cells are found in the coelomic fluid of representatives of several annelid groups. The ultrastructure of these "coelomocytes," however, has been studied to a limited degree. In this study, we used a transmission electron microscope to investigate the coelomocytes in specimens of five species of Naidinae and three species of Rhyacodrilinae (all oligochaetous clitellates within the family Tubificidae). These were compared with each other and with previously described coelomocytes of representatives of other oligochaete taxa. Only one distinguishable coelomocyte type was found in the studied specimens: a round to oblong cell without pseudopodia or other appendages, primarily containing membrane-bound granules of varying electron density, a prominent network of rough endoplasmic reticulum, and free ribosomes. This type differs to a great extent from most of the previously described coelomocytes, but shows similarities to certain types found in members of Enchytraeidae and Megascolecidae. Although we noticed some variation, we did not find any ultrastructural characters in these cells obviously useful for phylogenetic studies within Tubificidae.

Ovary micromorphology and oogenesis in a rhyacodriline oligochaete (Clitellata: Naididae, Rhyacodrilinae)

“…Another cytological approach described the ultrastructure of coelomocytes and provided support for a close relationship of the Naidinae and the rhyacodriline group that is formed by Rhyacodrilus, Monopylephorus, and Ainudrilus spp. (Envall et al, 2008). Moreover, both Rhyacodrilinae and Naidinae typically have the so-called diffuse prostate glands on the male duct as opposed to other conditions in many other groups (Erséus et al, 2017).…”

Morphology, cytogenesis and functions of Annelida coelomocytes

“…Клетки, сходные по морфологии с мукоцитами энхитреид и мегасколецид, описаны для представителей семейства Tubificidae (Envall et al, 2008). Авторы выделили только один тип целомоцитов у изученных восьми видов: пяти представителей подсемейства Naidinae и трех представителей подсемейства Rhyacodrilinae.…”