Relationship of symbiotic microorganisms to metanephridium: Phagoctic activity in the metanephridial epithelium of two species of oligochaeta

Abstract

It is known that a number of species in the annelid family Lumbricidae harbor symbiotic microorganisms in the lumen of their nephridia. The purpose of the present paper is the study of the relationship between microbes and epithelial cells lining the metanephridium of two species of Oligochaeta, which show two different patterns of microbial colonization. A new interesting feature, the phagocytosis and intracellular destruction of microorganisms by the nephridial epithelial cells, has been observed in our laboratory for the first time. In Scheroteca savignyi minor, the phagocytic activity takes place in the bladder, the most distal region of the nephridium, next to the nephridiopore, which may prevent the microorganisms from entering the more proximal regions. In Octolasion cyaneum the microbes reach the striated duct, where they live in symbiosis, adhere to the cell's surface, and are engulfed and destroyed by the cells of the middle tubule-the more proximal, neighboring region. The phagocytosis and intracellular degradation of microorganisms probably lead to the massive formation of lamellar bodies, which are observed in these cells and in the neighboring ones.

Acidovorax‐like symbionts in the nephridia of earthworms

“…3. Placement of the nephridial symbionts in the class Beta-proteobacteria is consistent with earlier microscopic observations that the symbionts were Gram-negative (Pandazis, 1931;Scott and Musgrave, 1971;Villaro et al ., 1985).…”

“…1D). A similar arrangement of cells was found in A. tuberculata and O. lacteum (data not shown), and also by electron microscopy of the nephridia of three lumbricid species including O. lacteum (Scott and Musgrave, 1971;Villaro et al ., 1985). In L. terrestris , the symbionts filled the whole lumen of the ampulla in most cases ( Fig.…”

“…The ampulla is approximately 50–500 µm long depending on the size of the worm, and bacterial colonization is usually restricted to this section. Bacteria were initially reported in the ampulla in 1926 (Knop, 1926), and more detailed functional and microscopic observations followed later (Pandazis, 1931; Scott and Musgrave, 1971; Villaro et al ., 1985) However, the putative symbionts have not yet been identified, and information about their transmission and symbiotic role is mostly speculative. The goal of this study was to: (i) identify the putative symbionts on the basis of their 16S rRNA gene sequences; (ii) confirm the origin of the sequences by fluorescence in situ hybridization (FISH), and (iii) obtain first insights into the evolutionary origin of the symbiosis by comparison of 16S rRNA gene sequences from different host species.…”

Up-regulation of Neurohemerythrin Expression in the Central Nervous System of the Medicinal Leech, Hirudo medicinalis, following Septic Injury

“…Indeed, recent works from Deloffre et al (65) showed that a hemerythrin-like peptide (MPII) isolated from the Annelid N. diversicolor was released in the blood stream after infection and possess a bacteriostatic activity. In this case, the hemerythrin expression in nephridial tissue would be important in Annelids because invading microorganisms can be excreted by nephridia (66) or engulfed by cells of the nephrostome (67). Expression of a bacteriostatic molecule, like hemerythrin, in this bacteria entrance/exit site would be crucial for the leech immunity.…”

Presence of Culturable Bacteria in Cocoons of the Earthworm Eisenia fetida

“…Few studies have examined the relationship between bacteria and cocoons or cocoon albumen. Most recent investigations of the putative bacterial symbiosis with earthworm nephridia have used only qualitative methods (30,34), and the proposed model of intergenerational transfer of symbionts via cocoons remains a hypothesis. Cocoons have been injected with laboratory-grown suspensions of bacteria isolated from nephridia, with no pathogenic effect; yet the relationship between the injected bacteria and the bacteria observed in embryonic nephridia was based solely on microscopic morphology as determined by Gram staining (23).…”