Shakurova N.V., Gataullina A.R. 2017. A comparative ultrastructural analysis of eyes in leeches (Hirudinea: Rhynchobdellida, Arhynchobdellida) // Invertebrate Zoology. Vol.14. No.2: 190–196 [in English].
Kazan Federal University, Kazan, 420008, Russian Federation. E-mail: email@example.com
ABSTRACT: The hirudineas seem to be unique among the Clitellata because of presence of a complete phaosomal organs — pigmented eyes — that are widespread only in leeches. The last works on the ultrastructure of leech eyes were done in the 60’s. The ultrastructure of eyes of the rhynchobdellids, Glossiphonia complanata L., 1758; Helobdella stagnalis L., 1758 at two developmental stages (larva / adult), and the arhynchobdellids, Erpobdella octoculata L., 1758; E. nigricollis Brandes, 1900, was investigated. The differences between the two orders of leeches are revealed in the ultrastructure of the rhabdom, the rhabdomeres, periphaosomal zone, and pigmented granules. The rhynchobdellid eyes are characterized by a compact rhabdom, ovoid-spherical phaosomal rhadbomeres, relatively short microvilli, and one type pigment granules in supported pigmented cells of eyes. The unique characteristic of the Rhynchobdellida is the apical centrioles in the phaosomal photoreceptoral cells. For the Arhynchobdellida the features are the less compact rhabdom which separated by an extracellular matrix, ovoid-flattened rhabdomeres, and two types of pigment granules. The unique characteristics of the Arhynchobdellida are distinct zones in the periphaosomal cytoplasm: inner, reticular and outer, mitochondrial layers. The successive events of development of eyes after hatching are as follows: formed clusters of phaosomal photoreceptor cells, associated with pigmented cells or not, move, gradually, rhabdom constitutes compact and becomes surrounded by the pigmented cells of the eye cup. Meanwhile, the phaosomal rhabdomers become rounded up, microvilli elongate, and a stalk appears. Pigmental cells undergo structural changes as well.
KEY WORDS: Rhynchobdellida, Arhynchobdellida, ultrastructure, eye cup, phaosome, larval eyes.