The means of orientation is studied in the Vietnamese pygmy dormouse Typhlomys chapensis,a poorly known enigmatic semi-fossorial semi-arboreal rodent.Data on eye structure are presented,which prove that Typhlomys(tran...The means of orientation is studied in the Vietnamese pygmy dormouse Typhlomys chapensis,a poorly known enigmatic semi-fossorial semi-arboreal rodent.Data on eye structure are presented,which prove that Typhlomys(translated as“the blind mouse”)is incapable of object vision:the retina is folded and retains no more than 2500 ganglion cells in the focal plane,and the optic nerve is subject to gliosis.Hence,Typhlomys has no other means for rapid long-range orientation among tree branches other than echolocation.Ultrasonic vocalization recordings at the frequency range of 50-100 kHz support this hypothesis.The vocalizations are represented by bouts of up to 7 more or less evenly-spaced and uniform frequency-modulated sweep-like pulses in rapid succession.Structurally,these sweeps are similar to frequency-modulated ultrasonic echolocation calls of some bat species,but they are too faint to be revealed with a common bat detector.When recording video simultaneously with the ultrasonic audio,a significantly greater pulse rate during locomotion compared to that of resting animals has been demonstrated.Our findings of locomotion-associated ultrasonic vocalization in a fast-climbing but weakly-sighted small mammal ecotype add support to the“echolocation-first theory”of pre-flight origin of echolocation in bats.展开更多
Comparative study of terrestrial locomotion of 4fish genera including Anabas,Channa,Clarias,and Monopterus,was performed in experimental setting with the substrate surface of wet clay.No special adaptations for terrest...Comparative study of terrestrial locomotion of 4fish genera including Anabas,Channa,Clarias,and Monopterus,was performed in experimental setting with the substrate surface of wet clay.No special adaptations for terrestrial locomotion were found.Everyfish uses for propulsion on land what it already has.Eel-shaped Monopterus crawls by body undulations in a serpentine or sidewinding technique,the latter of which was not previously observed beyond snakes.The other 3fish genera walk by body oscillations using stiff appendages as propulsors.When they are located anteriorly,as the serrate operculum in Anabas and the preaxial spine of the pectoralfin in Clarias,the propulsion is termed prolocomotor,when posteriorly,as the spiny analfin in Channa—metalocomotor.Channa is the heaviestfish walking out of water in our days,quite comparable in size withfirst Devonian tetrapods Acan-thostega and Tulerpeton.A theoretical calculation is suggested for the upper size limit of afish capable of terrestrial walking without special locomotor adaptations.It should be roughly 20 cm in the vertical dimension of the trunk,which is just a little above the known size of Devonian tetrapodomorphfishes Panderichthys and Elpistostege.The metalocomotor walking technique of Channa is suggested as the closest extant model for terrestrial locomotion at thefish-tetrapod transition.The major difference is that the metalocomotor propulsor in Channa is represented by the analfin,while in tetrapodomorphs by the pelvicfins.The sprawled pelvicfins were advantageous in respect of reduced requirement for side-to-side tail swinging.展开更多
基金approved by the Committee of Bio-ethics of the Lomonosov Moscow State University(research protocol no.2011-36)Video processing was performed with support of the Russian Science Foundation(project 14-50-00029“Scientific basis of the national biobank-depository of the living systems”)+1 种基金Acoustic analysis was supported by the Russian Science Foundation(project 14-14-00237)the Program of Basic Research of the Presidium of the Russian Academy of Sciences“Wildlife:Current Status and Problems of Development.”。
文摘The means of orientation is studied in the Vietnamese pygmy dormouse Typhlomys chapensis,a poorly known enigmatic semi-fossorial semi-arboreal rodent.Data on eye structure are presented,which prove that Typhlomys(translated as“the blind mouse”)is incapable of object vision:the retina is folded and retains no more than 2500 ganglion cells in the focal plane,and the optic nerve is subject to gliosis.Hence,Typhlomys has no other means for rapid long-range orientation among tree branches other than echolocation.Ultrasonic vocalization recordings at the frequency range of 50-100 kHz support this hypothesis.The vocalizations are represented by bouts of up to 7 more or less evenly-spaced and uniform frequency-modulated sweep-like pulses in rapid succession.Structurally,these sweeps are similar to frequency-modulated ultrasonic echolocation calls of some bat species,but they are too faint to be revealed with a common bat detector.When recording video simultaneously with the ultrasonic audio,a significantly greater pulse rate during locomotion compared to that of resting animals has been demonstrated.Our findings of locomotion-associated ultrasonic vocalization in a fast-climbing but weakly-sighted small mammal ecotype add support to the“echolocation-first theory”of pre-flight origin of echolocation in bats.
文摘Comparative study of terrestrial locomotion of 4fish genera including Anabas,Channa,Clarias,and Monopterus,was performed in experimental setting with the substrate surface of wet clay.No special adaptations for terrestrial locomotion were found.Everyfish uses for propulsion on land what it already has.Eel-shaped Monopterus crawls by body undulations in a serpentine or sidewinding technique,the latter of which was not previously observed beyond snakes.The other 3fish genera walk by body oscillations using stiff appendages as propulsors.When they are located anteriorly,as the serrate operculum in Anabas and the preaxial spine of the pectoralfin in Clarias,the propulsion is termed prolocomotor,when posteriorly,as the spiny analfin in Channa—metalocomotor.Channa is the heaviestfish walking out of water in our days,quite comparable in size withfirst Devonian tetrapods Acan-thostega and Tulerpeton.A theoretical calculation is suggested for the upper size limit of afish capable of terrestrial walking without special locomotor adaptations.It should be roughly 20 cm in the vertical dimension of the trunk,which is just a little above the known size of Devonian tetrapodomorphfishes Panderichthys and Elpistostege.The metalocomotor walking technique of Channa is suggested as the closest extant model for terrestrial locomotion at thefish-tetrapod transition.The major difference is that the metalocomotor propulsor in Channa is represented by the analfin,while in tetrapodomorphs by the pelvicfins.The sprawled pelvicfins were advantageous in respect of reduced requirement for side-to-side tail swinging.
