Sperm Transfer Through the Vector Tissue in Piscicola Respirans (Clitellata, Hirudinea, Piscicolidae)

Abstract

In fish leeches (Piscicolidae) indirect (hypodermic) insemination has evolved, thus the spermatophores are released in the specialised region of the body wall known as a copulatory area or a copulatory region. The way in which the spermatozoa reach the ovaries is not fully understood. In piscicolids beneath the copulatory area there is a specialized connective tissue (vector tissue), which is thought to guide the spermatozoa toward the ovaries. To date the structure of the vector tissue has not been observed in copulating specimens, which have spermatophores implanted in their coplulatory area. Here we present the first ultrastructural observation of massive sperm transfer from the spermatophore throughout the vector tissue to the ovaries. Our results show that the sperm transfer is both massive and rapid. The migrating spermatozoa form huge aggregations which push aside the vector tissue cells, in such a way that between these cells voluminous gaps are formed. Unexpectedly to our previous suggestions, the ultrastructural pictures show that the long cytoplasmic processes of granular cells, which constitute the main mass of the vector tissue, are not engaged in sperm transport. We suggest that the sperm is pumped with a high pressure from the spermatophore into the vector tissue, and as a result the vector tissue cells are pushed aside and spermatozoa can freely pass between them.

Reproductive strategies of the kangaroo leech, Marsupiobdella africana (Glossiphoniidae)

“…This is the so called hypodermic implantation found in Glossiphoniidae and Eropobdellidae ( Bielecki, 2004 ). In leeches with indirect insemination, the spermatophores may be implanted anywhere in the body and the mechanism of migration by which the spermatozoa must reach the ovary through the body wall and internal spaces is unknown ( Swaitek et al., 2009 ).…”

“…Most members of the family Piscicolidae have specialized body regions near the gonopores where spermatophores are implanted, and just beneath this copulatory area a specialized form of connective tissue is found, i.e. vector tissue ( Swaitek et al., 2009 ). For Piscicolidae, the route taken by the sperm is well described.…”

Diversity of features of the female reproductive system and other morphological characters in leeches (Citellata, Hirudinida) in phylogenetic conception

“…Vector tissue is an important feature of the female reproductive system (Figs f, g,h), particularly in the piscolids. Vector tissue was found and described in Acanthobdella peledina (Epstein, ) and piscicolid leeches only (Brumpt, ; Sawyer, ; Świątek et al., , ; Fig. f); however, there are some suggestions that vector tissue occurs also in representatives of Glossiphoniidae (Brumpt, ; Bielecki, ).…”

“…Cytochemical and microscopic methods were used as described elsewhere (Świątek, ,b, , ; Świątek et al., , , ,b, ; Spałek‐Wołczyńska et al., ; Ben Ahmed et al., , ; Urbisz et al., ). All specimens were fixed with 2.5% glutaraldehyde in 0.1 m phosphate buffer (pH 7.4), then dissected.…”

“…Several studies devoted to ovarian morphology and the course of oogenesis in true leeches have been published recently (Świątek, ,b, , ; Spałek‐Wołczynska et al., ; Świątek et al., , ,b; Ben Ahmed et al., , ), providing substantial new comparative data about the internal ovarian organization in leeches. Specifically, these new data include the non‐polarized ovary cords in Glossiphoniidae, egg follicles in Piscicolidae, polarized ovary cords in Hirudinidae and Haemopidae and in Erpobdellidae, as well as detailed descriptions of oogenesis (i.e.…”