Histological and histochemical characterization of the secretory cells of Choeradoplana iheringi Graff, 1899 (Platyhelminthes: Tricladida: Terricola)

Abstract

The present study aims at providing a detailed description of the histology, as well as the first histochemical characterization, of the secretory cells of the epidermis, pharynx, and copulatory organs of Choeradoplana iheringi, in order to give further support to studies on the physiology of these organs. The secretory cells are distinguished on the basis of secretion morphology and its staining properties, using trichrome methods and histochemical reactions. Four cell types open through the epidermis of Ch. iheringi, three of them secreting basic protein and a fourth containing glycosaminoglycan mucins. The epidermal lining cells store glycogen. In the pharynx, four secretory cell types were distinguished. Two types produce glycoprotein, a third type secretes basic protein, and another one produces glycosaminoglycan mucins. In the male copulatory organs, the prostatic vesicle receives four secretory cell types containing basic protein, except for one type which produces glycoprotein. The two secretory cell types opening into the male atrium secrete, respectively, glycoprotein, and glycosaminoglycan mucins. In the female copulatory organs, the female atrium and its proximal diverticulum, the vagina, receive two types of secretory cells producing, respectively, basic protein and glycosaminoglycan mucins. Another secretory cell type constitutes the so-called shell glands which open into the common glandular duct, secreting basic protein. The lining cells of the male and female atria produce a mucous secretion containing glycosaminoglycans. In addition, the lining epithelium of the female atrium presents an apical secretion of a proteic nature. The occurrence of a kind of spermatophore is reported for the first time for a species of Choeradoplana. This structure is located in the male or female atria in different specimens, and characterized by erythrophil, xanthophil, and/or mixed secretions associated with sperm.

The Alkaloid Ageladine A, Originally Isolated from Marine Sponges, Used for pH-Sensitive Imaging of Transparent Marine Animals

“…This flatworm showed the highest fluorescence at the rhabdoids (Figure 5), which are described to be acidophilic [25]. The function of rhabdoids has, to my knowledge, thus far not been sufficiently described.…”

Morphology of parenchymally implanted foreign bodies indicates copulatory wounding in a planarian

“…First of all, foreign bodies share structural similarities with spermatophores of other land planarians. Such spermatophores are usually ovoid structures, 100-500 μm in size, and may be attached to the ventral wall of the male atrium [Luteostriata muelleri (Diesing, 1861), Notogynaphallia sexstriata (Müller, 1856), Amaga righii (E. M. Froehlich, 1972), C. iheringi (Graff, 1899)], or located in the copulatory bursa (Pimea monticola Winsor, 1991) or at the entrance of the gonoduct (C. onae Lago- Barcia et al, 2021;Froehlich, 1956;Froehlich, 1959;Froehlich & Froehlich, 1972;Winsor, 1991;Souza & Leal-Zanchet, 2004;Lago-Barcia et al, 2021).…”

“…Although there is some variation in their structure, land planarian spermatophores usually consist of a sperm mass partly or completely surrounded by layers of secretions with varied histochemical affinities (Froehlich, 1959;Lago-Barcia et al, 2021;Souza & Leal-Zanchet, 2004;Winsor, 1991). Although individual sperm were not discernible in the implanted foreign bodies of C. albonigra, they were also inconspicuous in the sperm ducts (Figure 3), where sperm are usually densely packed and possibly difficult to be individually recognized.…”

“…Spermatophores from congeneric and other closely related land flatworm species are transferred to the female atrium, where they are presumably attached by their layers of secreted material (Souza & Leal-Zanchet, 2004). From there, sperm presumably migrate from the spermatophore to the oviducts (Souza & Leal-Zanchet, 2004). When inside the female reproductive tract, sperm are devoid of the secreted material observed in the spermatophores (Souza & Leal-Zanchet, 2004).…”

“…From there, sperm presumably migrate from the spermatophore to the oviducts (Souza & Leal-Zanchet, 2004). When inside the female reproductive tract, sperm are devoid of the secreted material observed in the spermatophores (Souza & Leal-Zanchet, 2004). Curiously, although implanted spermatophores had hitherto never been recorded in land planarians, in at least three species (L. muelleri, N. sexstriata, and C. iheringi; Souza & Leal-Zanchet, 2004) the secreted component of the spermatophore may cause epithelial lysis at the site of attachment.…”