O. G. Dely szerk.: Vertebrata Hungarica 21. (Budapest, 1982)

Berger, L., Uzell, Th. ; Hotz, H.: Crossing experiments between some Western Palearctic species of water frogs (Salientia: Ranidae) 33-46. o.

anus (L), tibia length (T), length of first toe (DP), and length of callus internus (CI) were measured on each frog. The individuals were marked by cutting digits; some were put outdoors in the rearing area. A blood streak was obtained as each froglet was marked. The size of erythrocytes In the air-dried streaks was used to determine their ploidy (cf. UZZELL & BERGER 1975, GÜNTHER 1977, BERGER & ROGUSKI 1978). Eggs that were laid relatively late In the year were usually not saved for development. Rearing of tadpoles was mostly finished by the end of July. RESULTS Eggs. Among the 28 females, only three (one R. lesscoae

. two Italian hybrids) laid eggs that formed two or three discrete size-classes (cf. BERGER & UZZELL 1980). The eggs of the R. lessona

e female 9/79 (Table 1, cross 24) formed two size classes. Among 2059 gametes, five (0.24%) were large (1.94-2.00 mm In diameter, mean 1.98). The remaining eggs were medium-sized; a sample of 30 measured 1.68-1.82 mm In diameter, mean 1.74. The Italian hybrid females (Table 1, crosses 6, 7) laid 1422 and 902 eggs. In the first set, there was one large egg (diameter 1.86 mm) and 1421 medium-sized ones (range In a sample of 50, 1.46-1.56 mm, mean 1.51). The eggs of the second set formed three discrete size classes: small (two eggs, 1.12 and 1.16 mm In diameter), large (one egg, 1.60) and the remainder medium-sized (1.301.44 mm in diameter, mean 1.38 In a sample of 50). Vitality. The 30 sets of progeny came from 12 types of crosses (Table 1). Although there was considerable variation in the fertilization of eggs and vitality of the zygotes, there are some general patterns. In all but two of the 13 crosses Involving Italian females (Table 1, crosses 1-13) nearly all eggs cleaved, the two exceptions were eggs fertilized by hybrid males (crosses 9, 10). Two other crosses (24 and 27) involving one of these males also produced low percentages of cleaved eggs. Usually far more that 90 per cent of the cleaved eggs reached stage 25 (tadpole stadium). Further development, however, was very variable. The progeny saved for further development mothered by Italian non-hybrid females (crosses 1-4, 8-11) completed metamorphosis; In the other five crosses, Involving hybrid females, further development of the progeny was very poor. Many of the cleaved eggs from crosses in which both parents were Italian hybrids (crosses 5-7) reached stage 25, although even by stage 22 all larvae from the medium-sized and large eggs showed abnormal features: the became "argulus-llke" (cf. BERGER 1967); their development was Inhibited and eventually all died (Plate I: Flg. 1). Vitality of progeny fathered by R. perez

l males (crosses 12, 13) was also very low, but all of the larvae that reached stage 25 were normal In appearance. The larvae fathered by Portuguese male (cross 12) were divided into three groups. All were reared outdoors: groups of 20 and 30 in two separate aquaria, the others In a 300 liter outdoor basin. The tadpoles did not grow and soon began to die. In the aquarium with 30 larvae, all died within 30 days at lengths of 9-10 mm (one reached 11 mm). In the aquarium with 20 larvae, which was placed In a sunny room (Table 1), 17 larvae died within 25 days at lengths of 9-10 mm; three others grew very slowly, and measured 17, 21 and 24 mm in length on the 52nd day of development; the smallest was "argulusllke". These three tadpoles were killed. In the large basin, no living tadpoles were seen after day 30. The progeny fathered by French male (cross 13) were divided Into two groups. Thirty tadpoles developed In an aquarium outdoors; 23 Individuals died within 58 days; the others measured 22-24 mm. All of these were killed. Eight tadpoles developed in a sunny room; they grew very slowly (cf. Table 3, cross 9), but reached metamorphosis (Table 1, cross 13). Each of them died during resorption of the tail. They were placed In an Incubator at 28°C; the water was changed daily with room-temperature aged water. In the replacement water they became quite stiff, and only began to move again as the water warmed or if they were held In a warm hand. PLATE I. Fig. 1. Abnormal larvae "argulus-llke" of Italian hybrid before their death (Table 1, cross 5). Phot.: Z. PNIEWSKI - Fig, 2. Froglets from cross: R. lessona

e x Italian non-hybrid (Table 4, Fig. 1, cross 8). Phot.: Z. PNIEWSKI