The Grass Snake, Natrix natrix, is one of the non-venomous oviparous snakes of the family Colubridae, found in Mazandaran, a northern province of Iran. In order to study the spermatogenic cycle of this species in the ...The Grass Snake, Natrix natrix, is one of the non-venomous oviparous snakes of the family Colubridae, found in Mazandaran, a northern province of Iran. In order to study the spermatogenic cycle of this species in the area, sampling was done from April to November, and twenty-six male snakes were collected by hand during daylight hours. Testes were extracted from the specimens, and were fixed and prepared for histological examination. The results indicated that the spermatogenesis started in early June, November. The mean body length of the specimens was reached its height in August and September, and ended in measured 636.21 mm, and the mean volume of testes was 524.54 rnm3 and 569.06 mm3 for the right and left ones, respectively, and the mean weight of the testes was 0.051 g Spermatogenesis in this species is aestival and sperms are stored for use in the year following production.展开更多
Ciries represent a unique ecosystem dominated by humans and highdensity man-made infrastructure,associated with modifications or entire loss of local habitats.Thus,urbanization constitutes a consid-erable challenge fo...Ciries represent a unique ecosystem dominated by humans and highdensity man-made infrastructure,associated with modifications or entire loss of local habitats.Thus,urbanization constitutes a consid-erable challenge for wildlife,and only a minority of species is able to persist in cities(Niemela et al.2011).Species that maintain popula-tions in cities are usually characterized by significant changes in life history characteristics,population structure,and ecological relations(Niemela et al.2011).展开更多
Batesian mimicry is the process in which harmless species adopt the appearance of a dangerous, aposematic species.In some prey species,both Batesian mimetic and non-Batesian morphs coexist,presupposing that both morph...Batesian mimicry is the process in which harmless species adopt the appearance of a dangerous, aposematic species.In some prey species,both Batesian mimetic and non-Batesian morphs coexist,presupposing that both morphs have to be evolutionarily advantageous.The viperine snake, Natrix maura,exhibits a zigzag dorsal pattern and antipredatory behavior that mimics European vipers.This snake also has a striped dorsal pattern that coexists with the zigzag pattern.We have examined whether individuals belonging to different geographically structured clades were more likely to exhibit a certain dorsal pattern,and whether the zigzag pattern has a protective function by exposing artificial snakes to predation in natural environments,in addition to comparing antipredatory behavior between zigzag and striped snakes also in natural environments.Our results indicate that the striped pattern was not geographically structured,but habitat-dependent.Aerial predators less frequently attacked zigzag plasticine models than striped or unpatterned models.We detected a shift in antipredator behavior between the 2 morphs,as Batesian mimicking N.maura responded to an approaching potential predator by remaining immobile or fleeing at shorter distances than did striped ones.We conclude that Batesian mimics maintain the cryptic and aposematic value by resembling vipers,whereas in open habitats the non-Batesian mimic has altered its antipredator behavior to maintain its fitness.展开更多
文摘The Grass Snake, Natrix natrix, is one of the non-venomous oviparous snakes of the family Colubridae, found in Mazandaran, a northern province of Iran. In order to study the spermatogenic cycle of this species in the area, sampling was done from April to November, and twenty-six male snakes were collected by hand during daylight hours. Testes were extracted from the specimens, and were fixed and prepared for histological examination. The results indicated that the spermatogenesis started in early June, November. The mean body length of the specimens was reached its height in August and September, and ended in measured 636.21 mm, and the mean volume of testes was 524.54 rnm3 and 569.06 mm3 for the right and left ones, respectively, and the mean weight of the testes was 0.051 g Spermatogenesis in this species is aestival and sperms are stored for use in the year following production.
基金This study was financially supported by a grant from the National Science Centre in Poland awarded to S.B.(grant no.UMO 2016/21/N/NZ8/00959)grant from Jagiellonian University in Krakcew awarded to B.Z.(grant no.DS/MND/WBiNoZ/INoS/24/2014).
文摘Ciries represent a unique ecosystem dominated by humans and highdensity man-made infrastructure,associated with modifications or entire loss of local habitats.Thus,urbanization constitutes a consid-erable challenge for wildlife,and only a minority of species is able to persist in cities(Niemela et al.2011).Species that maintain popula-tions in cities are usually characterized by significant changes in life history characteristics,population structure,and ecological relations(Niemela et al.2011).
文摘Batesian mimicry is the process in which harmless species adopt the appearance of a dangerous, aposematic species.In some prey species,both Batesian mimetic and non-Batesian morphs coexist,presupposing that both morphs have to be evolutionarily advantageous.The viperine snake, Natrix maura,exhibits a zigzag dorsal pattern and antipredatory behavior that mimics European vipers.This snake also has a striped dorsal pattern that coexists with the zigzag pattern.We have examined whether individuals belonging to different geographically structured clades were more likely to exhibit a certain dorsal pattern,and whether the zigzag pattern has a protective function by exposing artificial snakes to predation in natural environments,in addition to comparing antipredatory behavior between zigzag and striped snakes also in natural environments.Our results indicate that the striped pattern was not geographically structured,but habitat-dependent.Aerial predators less frequently attacked zigzag plasticine models than striped or unpatterned models.We detected a shift in antipredator behavior between the 2 morphs,as Batesian mimicking N.maura responded to an approaching potential predator by remaining immobile or fleeing at shorter distances than did striped ones.We conclude that Batesian mimics maintain the cryptic and aposematic value by resembling vipers,whereas in open habitats the non-Batesian mimic has altered its antipredator behavior to maintain its fitness.
