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The studies on the reproductive system of P. fasciata were based on 43 specimens. Two main types of the reproductive system can be distinguished in the studied population. Two types of reproductive system were the most frequent (20.93% each): with symmetrical ejaculatory ducts without a loop and symmetrical seminal vesicles reaching the end of the first pair of testes, situated next to the testes (adult individuals) (fig. 23) and with symmetrical ejaculatory ducts without a loop (fig. 21) and symmetrical poorly developed seminal vesicles situated asymmetrically anterior to the first pair of testes (juvenile individuals). The structure of the reproductive system corresponding with the description of the type specimen (BRUMPT, 1900) was not observed in the studied population.
Piscicola brylinskae n. sp. is described from the lake Vechten in the village of Bunnik (Prov. Utrecht), The Netherlands. The characteristic features of this leeches allow to conclude that this species is a member of the subfamily Piscicolinae, probably a parasite of fish.
Piscicola geometra (L.), Piscicola respirans Troschel, 1850, and Caspiobdella fadejewi (Epshtein, 1968) find their hosts (fishes) by reacting to their shadow. Eye-like spots whose number ranges from 8 to 16 depending on a species, located on the posterior sucker are the main receptors perceiving the decrease in light intensity and thus enabling an immedaite reaction to the host's shadow. They are distributed on the perimeter of the sucker, are absent only from the section that is constantly shaded by the leech body. Experiments with a simulated shadow reveled considerable differences in the threshold light doses between the studied species: P. geometra- 12 lux, P. resprans - 4 lux and C. fadejewi-2.5 lux. Below these values the leeches do not perceive the decrease in light intensity and do not make host-searching movements. The smallest decreases in light intensity, at which the leeches still make host-searching movement, are: P. geometra - 5 lux, P. resprans - 2 lux, and C. fadejewi - 1.5 lux. In case of P. respirans and C. fadejewi such small decreases in light intensity (2-1.5 lux) may be caused only by small fishes which, according to the results of the experiment, should not be infested. This is confirmed by field observations - small fishes are mostly free from parasites. Large fishes (casting a large shadow) have much more numerous leeches.
The studies on the reproductive system of P. respirans, based on 115 specimens, have revealed its considerable variability. Two main types of the system can be distinguished: 1) ovaries reaching the first pair of testes, ejaculatory ducts symmetrical, no seminal vesicles (juvenile individuals), 2) ovaries reaching the first pair of testes, ejaculatory ducts symmetrical, seminal vesicles reaching the ends of ovaries (adults individuals). The structure of the reproductive system is correlated with the individual size and age. Because the reproductive system of P. respirans as described by BRUMPT (1900) and SKET ( 1968) based on type specimens designated by them, is found only in a small fraction (c. 4-8%) of specimens, a redescription of the species is necessary, best based on a neotype series.
Histological analysis of frontal section through the body of parasitic leeches (Codonobdella truncata, Caspiobdella fadejewi) of the subfamily Piscicolinae revealed the presence of 11pairs of subepidermal pulsatile vesicles. The vesicles of C. truncata are poorly visible on the body surface, contrary to those of C. fadejewi, which results from the fact that in the former species the vesicles are located in a layet of subepidermal connective tissue thicker (82.82 μm) than in C.fadejewi (20.6 μm). In the studied species the pulsatile vesicles have a club-like shape, are surronded by a muscular tunicle and connected with a short canal that penetrates the body wall. Some of the sections show that the vesicles are divided in two chambers (lower and upper) with an incomplete membrane.
The aim of the study was to determine leeches found on the lake fishes. From the lake Ukiel, 213 roaches (R. rutilus) and from the lake Wulpińskie 202 were examined between Nov. 1988 and Dec. 1999. From the Warniak 258 roaches and 9 tenches (Tinca tinca) were examined between May 1998 and Nov. 1999. Warniak on roach (R. rutilus) 4 Piscicola geometra and Hemiclepis marginata on the fish body were found, tench (Tinca tinca) P. geometra were found on gills. Ukiel on roach Piscicola pojmanskae on gills were found. Wulpińskie on roach P. pojmanskae and Piscicola sp. as well as 2 Caspiobdella fadejewi on gills were found. Prevalence and intensity of fish infection with leeches was low in all lakes. C. fadejewi and P. pojmanskae are the first recorded on the lake fishes. Further investigations are necessary since they can result in informations conceming inhabitation of new microhabitants with P. geometra gills.
A new species of marine fish leeches is described and compared with its congeners. Oceanobdella sakhalinica possesses a unique combination of characters: the anterior sucker is small; one of posterior transverse bands on the urosome is very dark; a wedge-shaped patch is located on the posterior sucker; posterior crop caeca are separate for their entire length; accessory glands on the atrium are lacking; five pairs of testisacs are present; the copulatory area and the conductive tissue are lacking. Hosts include a sculpin Myoxocephalus sp. and the blackline prickleback Acantholumpenus mackayi. The leeches were collected in Aniva Bay, southern Sakhalin.
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