An ultrastructural study of the egg assembly region of the female reproductive tract of the monogenean (platyhelminth) skin parasites Entobdella soleae and E-hippoglossi

An ultrastructural study has been made of the egg assembly apparatus of the monopisthocotylean monogenean skin parasites Entobdella soleae and E. hipp oglossi from the common sole, Solea solea, and the halibut, Hippoglossus hi ppoglossus, respectively. The ootype consists of a distal tetrahedral chamb er where the egg capsule is assembled and a proximal ootype tube where the egg appendage is made. Two types of Mehlis' gland (alpha and beta) open at the proximal end of the ootype tube, which has a non-secretory lining. In b oth species, the tetrahedral ootype chamber has a syncytial lining, which a pparently is not secretory and possesses on its luminal surface stud-like p rojections, each with vacuolated cytoplasm and an electron-dense core. The ootype chamber is enclosed by a single layer of muscle fibres and is embedd ed in a spongy "connective tissue". The uterus in E. soleae has a cellular secretory lining, with densely packed luminal microvilli.