Ultrastructural observations on rodlet-cell development in the head kidney of the southern platyfish, Xiphophorus maculatus (Teleostei: Poeciliidae)

Abstract

The enigmatic rodlet cell has been observed in tissues of marine and freshwater teleosts. The origin and function of this cell remain unclear. We describe the association of the rodlet cell with the head-kidney tissue of the southern platyfish, Xiphophorus maculatus. We have observed rodlet cells in various tissues of X. maculatus, e.g., the hemopoietic compartments of the head kidney, gill epithelia, and ovarian tissue, and in melanotic tumors. Recently, we found rodlet cells within the mesothelium and musculature. Intrigued by these observations, we began our current study of the rodlet cell – head kidney association in X. maculatus. We discerned a series of developmental stages of the rodlet cell within the hemopoietic tissue of the head kidney, including early precursor cells through degraded terminal stages. Tight junctions and desmosomes were observed between mature rodlet cells and endothelial cells. Desmosomal junctions were occasionally seen between maturing rodlet cells and neighboring cells within intertubular areas. We never observed junctional complexes between adjacent rodlet cells at any stage. Rodlet sacs were released intact and were seen to interact with other cellular components. We relate our findings to those of others who have described the development and distribution of rodlet cells in teleosts.

Development of rodlet cells in the gut of turbot (Psetta maxima L.): Relationship between their morphology and S100 protein immunoreactivity

“…In a previous study, Kramer and Potter [17] reported that the development of cellular junctions such as desmosomes was related with the absence of the apical fibrous layer and the cell capability to release the rodlets. Moreover, rodlet cells located in extra-epithelial sites, and therefore unrelated with cellular junctions, are not able to discharge the rodlets [17].…”

“…In a previous study, Kramer and Potter [17] reported that the development of cellular junctions such as desmosomes was related with the absence of the apical fibrous layer and the cell capability to release the rodlets. Moreover, rodlet cells located in extra-epithelial sites, and therefore unrelated with cellular junctions, are not able to discharge the rodlets [17]. In line with this result, Bielek [1] left open the debate about the apparent contradictory existence of cellular junctions in cells that share functional properties with leucocytes.…”

“…There are some publications on rodlet cell development [1,16,17] but little is known about the relationship between the degree of development and their function.…”

Rodlet cells in teleosts: a new insight into their nature and functions

“…Of the papers published on RCs, the majority refer to the mature cell stage; nevertheless, putative immature and developmental RC stages have been described in several accounts (Iger & Abraham, 1997; Dezfuli et al ., 1998; Kramer & Potter, 2002). Immature RCs are oval in shape with large, pale euchromatic nuclei, conspicuous rough endoplasmic reticula and peculiar small, elongated mitochondria.…”

Rodlet cells development in the intestine of sea bass (Dicentrarchus labrax)

“…As a consequence, a longstanding controversy exists in the literature regarding the origin and nature of RCs. Although the exogenous hypothesis considers them as parasites (Bannister,1966; Barber,1979; Bielek and Viehberger,1983; Mayberry et al,1979; Richards et al,1994; Viehberger and Bielek,1982), the endogenous hypothesis regards them as normal constituent of fishes animal tissue, with a potential secretory activity (Bielek,2005; Dezfuli et al,1998, 2000, 2002,2003a, b; Leino,1974, 1982, 1996; Kramer and Potter,2002; Manera et al,2001; Mazon et al,2007; Vigliano et al,2006). Several evidence over recent years have supported the hypothesis that the RC participates in the fish non‐specific immune response (Abraham et al,2001; Dezfuli et al,1998, 2000, 2003a; Leino,1996; Reite,1997; Reite and Evensen,2006 ; Sulimanovic et al,1996).…”