The female gonad in two species of Microplana (Platyhelminthes, Tricladida, Rhynchodemidae): Ultrastructural and cytochemical investigations

Abstract

The female gonad of the land planarians Microplana scharffi and Microplana terrestris consists of two small germaria located ventrally in the anterior third of the body and of two ventro-lateral rows of oblong vitelline follicles distributed between the intestinal pouches. Both these structures are enveloped by a tunica composed of an outer extracellular lamina and an inner sheath of accessory cells. Oocyte maturation is characterized by the appearance of chromatoid bodies and the development of endoplasmic reticulum and Golgi complexes. These organelles appear to be correlated with the production of egg granules with a fenestrated/granular content of medium electron density, about 4-5 mum in diameter, which remain dispersed in the ooplasm of mature oocytes. On the basis of cytochemical tests showing their glycoprotein composition, and their localization in mature oocytes, these egg granules have been interpreted as yolk. In the vitelline follicles, vitellocytes show the typical features of secretory cells with well-developed rough endoplasmic reticulum and Golgi complexes involved in the production of eggshell globules and yolk. The eggshell globules, which appear to arise from repeated coalescences of two types of Golgi-derived vesicles, contain polyphenols and, when completely mature, they measure about 1-1,2 mum in diameter and show a meandering/concentric content pattern as is typical of the situation observed in most Proseriata and Tricladida. Mature vitellocytes also contain a large amount of glycogen and lipids as further reserve material. On the basis of the ultrastructural features of the female gonad and in relation to the current literature the two species of rhynchodemids investigated appear to be closely related to the freshwater planarians belonging to the family Dugesiidae.

Differential Evolution of Duplicated Medakafish mitf Genes

“…To perform transfection experiments in medaka ES cell line MES1, which is capable of directed melanocyte differentiation following transfection by pXmitf that expresses the Xiphophorus mitfm 34, we constructed several expression vectors (Figure 4A). pTYRluc contains the 3.3-kb medaka tyrosinase gene promoter (TYR) ahead of the luciferase 45, and pOmitf2 constitutively expresses the medaka mitf2 cDNA. In undifferentiated MES1 cells, mitf expression is not detectable by RT-PCR analysis 33, but can be activated by forced XmitfM expression 34.…”

“…Four luciferase 45 reporter plasmids were used in this study. pGL3-basic is promoterless and contains the firefly luc (Promega).…”

Ultrastructural and cytochemical aspects of the germarium and the vitellarium in Syndesmis patagonica (Platyhelminthes, Rhabdocoela, Umagillidae)

“…In S. patagonica the accessory cells, which are localized under the extracellular lamina, remain confined to the periphery of the gonad or, occasionally, partially protrude their cytoplasmic processes between oocytes and vitellocytes as is typical of most rhabdocoels (Falleni and Lucchesi, 1992;Lucchesi et al, 1995;Falleni et al, 1998Falleni et al, , 2005. Accessory cells completely enwrapping the growing oocytes and vitellocytes with their long cytoplasmic protrusions have been described in Proseriata (Sopott-Ehlers, 1994, 1995 and Tricladida (Gremigni and Nigro, 1983;Tekaya et al, 1999;Falleni et al, 2006Falleni et al, , 2009 and in the rhabdocoel temnocephalid Troglocaridicola sp., belonging to Scutariellidae, which surprisingly shares other ultrastructural characteristics of female gonad with Proseriata and Tricladida (Falleni et al, 2002) as well as similarities to Proseriata in spermiogenesis (Iomini et al, 1994). As suggested in previous papers, accessory cells are thought to play a trophic role in transferring low-molecular-weight-precursors from the surrounding tissue to the developing germ cells besides having a supporting function Falleni et al, 2002Falleni et al, , 2006Falleni et al, , 2009).…”

“…Accessory cells completely enwrapping the growing oocytes and vitellocytes with their long cytoplasmic protrusions have been described in Proseriata (Sopott-Ehlers, 1994, 1995 and Tricladida (Gremigni and Nigro, 1983;Tekaya et al, 1999;Falleni et al, 2006Falleni et al, , 2009 and in the rhabdocoel temnocephalid Troglocaridicola sp., belonging to Scutariellidae, which surprisingly shares other ultrastructural characteristics of female gonad with Proseriata and Tricladida (Falleni et al, 2002) as well as similarities to Proseriata in spermiogenesis (Iomini et al, 1994). As suggested in previous papers, accessory cells are thought to play a trophic role in transferring low-molecular-weight-precursors from the surrounding tissue to the developing germ cells besides having a supporting function Falleni et al, 2002Falleni et al, , 2006Falleni et al, , 2009). In addition, in S. patagonica the accessory cells contribute to the formation of the extracellular lamina of both the germarium and the vitellarium by releasing the content of elongated vesicles into the extracellular space through exocytosis, as has also been detected in some rhabdocoel Temnocephalida (Falleni et al, , 2002 and in some terrestrial triclads (Falleni et al, 2006).…”

“…Oocyte maturation occurs during the prophase of the first meiotic division as shown by the presence of synaptonemal complexes even in large oocytes as is typical of other neoophoran platyhelminths (Falleni et al, 2005(Falleni et al, , 2006(Falleni et al, , 2009.…”