We have determined the presence of spectral cone types, and the population densities of cones and... more We have determined the presence of spectral cone types, and the population densities of cones and rods, in subterranean mole-rats of the rodent family Bathyergidae, for which light and vision seems of little importance. Most mammals have two spectral cone types, a majority of middle- to long-wave-sensitive (L-) cones, and a minority of short-wave-sensitive (S-)cones. We were interested to see whether the subterranean bathyergids show the same pattern. In three species, Ansell's mole-rat Cryptomys anselli, the giant mole-rat Cryptomys mechowi and the naked mole-rat Heterocephalus glaber, spectral cone types and rods were assessed immunocytochemically with opsin-specific antibodies. All three species had rod-dominated retinae but possessed significant cone populations. A quantitative assessment in C. anselli and C. mechowi revealed surprisingly low photoreceptor densities of 100 000-150 000/mm(2), and high cone proportions, approximately 10% (8000-15 000/mm(2)). In all three species, the vast majority of the cones were strongly S-opsin-immunoreactive; L-opsin immunoreactivity was much fainter. In C. anselli, approximately 20% of the cones showed exclusive S-opsin label, approximately 10% exclusive L-opsin label and approximately 70% strong S-opsin and faint L-opsin double label (potential dual-pigment cones). This is the first observation in any mammal of an S-opsin dominance and low levels of L-opsin across the entire retina. It contrasts starkly with the situation in the muroid blind mole-rat Spalax ehrenbergi, which has been reported to possess L-opsin but no S-opsin. Evidently, within rodents an adaptation to subterranean life is compatible with very different spectral cone properties.
Page 1. 11 Visual Systems and the Role of Vision in Subterranean Rodents: Diversity of Retinal Pr... more Page 1. 11 Visual Systems and the Role of Vision in Subterranean Rodents: Diversity of Retinal Properties and Visual System Designs Pavel Nemec, Pavla CvekovĆ”, Hynek Burda, Oldrich Benada, Leo Peichl 11.1 Introduction ...
In spite of the growing interest in rodents with subterranean activity in general and the spalaci... more In spite of the growing interest in rodents with subterranean activity in general and the spalacids (Spalacidae) in particular, little is known about the biology of most members of this clade, such as the Chinese bamboo rat (Rhizomys sinensis). Here, we analyzed the ear morphology of R. sinensis with respect to hearing specialization for subterranean or aboveground modes of communication. It is well-known that ecology and style of life of a particular species can be reflected in morphology of its ear, its hearing and vocalization, so we expect that such information could provide us insight into its style of life and its sensory environment. The ratio between the eardrum and stapedial footplate areas, which influences the efficiency of middle ear sound transmission, suggests low hearing sensitivity, as is typical for subterranean species. The cochlea had 3.25 coils and resembled species with good low frequency hearing typical for subterranean mammals. The length of the basilar membra...
ā¢Ā Was verstehen Ćkologen und Evolutionsbiologen unter einer āInselā? ā¢Ā Was ist eine Art? ā¢Ā Was... more ā¢Ā Was verstehen Ćkologen und Evolutionsbiologen unter einer āInselā? ā¢Ā Was ist eine Art? ā¢Ā Was verstehen wir unter āBiodiversitƤtā? ā¢Ā Wie viele Arten leben auf der Erde, und wie kann man sie zƤhlen? ā¢Ā Wie entstehen neue Arten, und wie trennen sie sich voneinander? ā¢Ā Was ist eine ƶkologische Nische? ā¢Ā Wie viele ƶkologische Nischen gibt es? ā¢Ā Kann man die Entwicklung der Vielfalt vorhersagen? ā¢Ā Warum sterben Arten aus? Gibt es GesetzmƤĆigkeiten im Aussterbemuster? ā¢Ā Wie hƤngen Anagenese und Kladogenese zusammen? ā¢Ā Warum sind einige Kladen artenreich und andere artenarm? ā¢Ā Was sind SchlĆ¼sselneuheiten, und wie kann man sie erkennen? ā¢Ā VerlƤuft die Evolution graduell oder erfolgt sie sprunghaft? ā¢Ā Warum gibt es in den Tropen mehr Arten als in den gemƤĆigten Zonen? ā¢Ā Wie sieht die Geschichte und wie die Zukunft der biologischen Vielfalt aus?
ā¢Ā Wann und wo entstanden die ersten Tiere? Wie sahen sie aus? ā¢Ā Was verstehen die Biologen unte... more ā¢Ā Wann und wo entstanden die ersten Tiere? Wie sahen sie aus? ā¢Ā Was verstehen die Biologen unter einem Bauplan? ā¢Ā Wie entstanden die Wirbeltiere? ā¢Ā Kƶnnen auch heute noch neue BauplƤne entstehen? ā¢Ā Wie schnell verlƤuft die Evolution? ā¢Ā Was verstehen Zoologen unter einer āKasteā? ā¢Ā Welche Rolle spielt die Duplikation der Gene in der Evolution? ā¢Ā Womit beschƤftigt sich āEvo-Devoā? ā¢Ā Wie wird auf Grundlage der genetischen Information eine Fliege āhergestelltā? ā¢Ā Was haben FlĆ¼gel, Beine und āAugenā von Tagpfauenaugen gemeinsam? ā¢Ā Worauf beruht die morphologische Vielfalt der Pflanzen? ā¢Ā Worauf beruht die Vielfalt der Wirbeltiere? ā¢Ā Warum sind die Augen nicht vollkommen und warum ist ihre Entstehung durch graduelle Evolution durchaus plausibel? ā¢Ā Warum arbeitet die Evolution eher wie ein Bastler und nicht wie ein Konstrukteur? ā¢Ā Was sagt uns die Ontogenese Ć¼ber die Evolution und die Phylogenese? ā¢Ā Ist die frĆ¼he Ontogenese konservativ oder instabil? ā¢Ā Wie kann die Geschwindigkeit der Ontogenese die Morphologie und das Verhalten von erwachsenen Organismen beeinflussen? ā¢Ā Was verstehen die Kreationisten unter āPaleys Uhrā und ānichtreduzierbarer KomplexitƤtā?
Zambian common mole-rats are subterranean rodents that live in families with only one female bree... more Zambian common mole-rats are subterranean rodents that live in families with only one female breeding. Her offspring remain in the parental nest and do not reproduce. Behavioral experiments (Burda, '95) demonstrated that their apparent "sterility" is based on incest avoidance and individual recognition of family members. To elucidate whether some kind of morphologically apparent ovarian suppression still takes place in daughters, ovaries of females of known age, weight, and reproductive histories were examined histologically and morphometrically. The body mass of old females (more than 3 years of age) begins to decrease, and the ovaries seem to begin to atrophy at the age of about 3-6 years. Ovaries in neonates exhibited primordial and primary follicles, sometimes clustered in nests. Ovaries of adult nonbreeding females expressed all stages of the follicular development up to tertiary follicles. Many unruptured luteinized follicles were present, but true corpora lutea as a morphological sign of ovulation were missing. Unruptured luteinized follicles also could be found (additionally to true corpora lutea) in ovaries of breeding females. The number of primordial follicles dropped rapidly during the first 2 years of age; the number of primary, secondary, and tertiary follicles was subject to individual variation; and there was no clear correlation with age or reproductive status. While a tendency to form accessory unruptured luteinized follicles may just reflect taxonomic affinities of bathyergids to hystricomorphs, the otherwise complete folliculogenesis in "sterile" daughters and the presence of unruptured luteinized follicles even in breeding females are further evidence that there is no hormonal suppression of the ovarial cycle. We suggest that ovulation in nonbreeding females is not actively suppressed by the breeding female, but instead that it is not released because the triggering mechanisms, most probably repeated copulation, are missing.
Since the spatial mobility of subterranean mole-rats is restricted and their skull strongly modif... more Since the spatial mobility of subterranean mole-rats is restricted and their skull strongly modified, morpho-functional regression of their vestibular organ may be expected. On the other hand, vestibular sense may be indispensable for orientation in a world deprived of most external sensory cues. Since vestibular sensitivity is determined by the size of the labyrinth, morphometrical analysis may be employed to assess the sensitivity and to test whether the organ is degenerate or progressively specialized. We analyzed the shape and size of the membranous labyrinth of vestibular organs in toto in three species of African subterranean blind mole-rats of the genus Cryptomys (Bathyergidae) differing in body size yet not in habitats, ways of life, or employed orientation and locomotory strategies. The mechanical sensitivity of the cupula was estimated according to Oman et al. (1987. Acta Otolaryngol. (Stockh.), 103:1-13) for each of the three semicircular ducts. The size and shape of the vestibular organ changed predictably depending on species-specific (yet not individual) body mass. In some aspects, particularly the cross-sectional area, the ducts were larger than expected for a mammal of a comparable body size. In all species examined, the anterior semicircular ducts exhibited the highest sensitivity. The vestibular organs of blind subterranean mole-rats are not regressed morpho-functionally.
We have determined the presence of spectral cone types, and the population densities of cones and... more We have determined the presence of spectral cone types, and the population densities of cones and rods, in subterranean mole-rats of the rodent family Bathyergidae, for which light and vision seems of little importance. Most mammals have two spectral cone types, a majority of middle- to long-wave-sensitive (L-) cones, and a minority of short-wave-sensitive (S-)cones. We were interested to see whether the subterranean bathyergids show the same pattern. In three species, Ansell's mole-rat Cryptomys anselli, the giant mole-rat Cryptomys mechowi and the naked mole-rat Heterocephalus glaber, spectral cone types and rods were assessed immunocytochemically with opsin-specific antibodies. All three species had rod-dominated retinae but possessed significant cone populations. A quantitative assessment in C. anselli and C. mechowi revealed surprisingly low photoreceptor densities of 100 000-150 000/mm(2), and high cone proportions, approximately 10% (8000-15 000/mm(2)). In all three species, the vast majority of the cones were strongly S-opsin-immunoreactive; L-opsin immunoreactivity was much fainter. In C. anselli, approximately 20% of the cones showed exclusive S-opsin label, approximately 10% exclusive L-opsin label and approximately 70% strong S-opsin and faint L-opsin double label (potential dual-pigment cones). This is the first observation in any mammal of an S-opsin dominance and low levels of L-opsin across the entire retina. It contrasts starkly with the situation in the muroid blind mole-rat Spalax ehrenbergi, which has been reported to possess L-opsin but no S-opsin. Evidently, within rodents an adaptation to subterranean life is compatible with very different spectral cone properties.
Page 1. 11 Visual Systems and the Role of Vision in Subterranean Rodents: Diversity of Retinal Pr... more Page 1. 11 Visual Systems and the Role of Vision in Subterranean Rodents: Diversity of Retinal Properties and Visual System Designs Pavel Nemec, Pavla CvekovĆ”, Hynek Burda, Oldrich Benada, Leo Peichl 11.1 Introduction ...
In spite of the growing interest in rodents with subterranean activity in general and the spalaci... more In spite of the growing interest in rodents with subterranean activity in general and the spalacids (Spalacidae) in particular, little is known about the biology of most members of this clade, such as the Chinese bamboo rat (Rhizomys sinensis). Here, we analyzed the ear morphology of R. sinensis with respect to hearing specialization for subterranean or aboveground modes of communication. It is well-known that ecology and style of life of a particular species can be reflected in morphology of its ear, its hearing and vocalization, so we expect that such information could provide us insight into its style of life and its sensory environment. The ratio between the eardrum and stapedial footplate areas, which influences the efficiency of middle ear sound transmission, suggests low hearing sensitivity, as is typical for subterranean species. The cochlea had 3.25 coils and resembled species with good low frequency hearing typical for subterranean mammals. The length of the basilar membra...
ā¢Ā Was verstehen Ćkologen und Evolutionsbiologen unter einer āInselā? ā¢Ā Was ist eine Art? ā¢Ā Was... more ā¢Ā Was verstehen Ćkologen und Evolutionsbiologen unter einer āInselā? ā¢Ā Was ist eine Art? ā¢Ā Was verstehen wir unter āBiodiversitƤtā? ā¢Ā Wie viele Arten leben auf der Erde, und wie kann man sie zƤhlen? ā¢Ā Wie entstehen neue Arten, und wie trennen sie sich voneinander? ā¢Ā Was ist eine ƶkologische Nische? ā¢Ā Wie viele ƶkologische Nischen gibt es? ā¢Ā Kann man die Entwicklung der Vielfalt vorhersagen? ā¢Ā Warum sterben Arten aus? Gibt es GesetzmƤĆigkeiten im Aussterbemuster? ā¢Ā Wie hƤngen Anagenese und Kladogenese zusammen? ā¢Ā Warum sind einige Kladen artenreich und andere artenarm? ā¢Ā Was sind SchlĆ¼sselneuheiten, und wie kann man sie erkennen? ā¢Ā VerlƤuft die Evolution graduell oder erfolgt sie sprunghaft? ā¢Ā Warum gibt es in den Tropen mehr Arten als in den gemƤĆigten Zonen? ā¢Ā Wie sieht die Geschichte und wie die Zukunft der biologischen Vielfalt aus?
ā¢Ā Wann und wo entstanden die ersten Tiere? Wie sahen sie aus? ā¢Ā Was verstehen die Biologen unte... more ā¢Ā Wann und wo entstanden die ersten Tiere? Wie sahen sie aus? ā¢Ā Was verstehen die Biologen unter einem Bauplan? ā¢Ā Wie entstanden die Wirbeltiere? ā¢Ā Kƶnnen auch heute noch neue BauplƤne entstehen? ā¢Ā Wie schnell verlƤuft die Evolution? ā¢Ā Was verstehen Zoologen unter einer āKasteā? ā¢Ā Welche Rolle spielt die Duplikation der Gene in der Evolution? ā¢Ā Womit beschƤftigt sich āEvo-Devoā? ā¢Ā Wie wird auf Grundlage der genetischen Information eine Fliege āhergestelltā? ā¢Ā Was haben FlĆ¼gel, Beine und āAugenā von Tagpfauenaugen gemeinsam? ā¢Ā Worauf beruht die morphologische Vielfalt der Pflanzen? ā¢Ā Worauf beruht die Vielfalt der Wirbeltiere? ā¢Ā Warum sind die Augen nicht vollkommen und warum ist ihre Entstehung durch graduelle Evolution durchaus plausibel? ā¢Ā Warum arbeitet die Evolution eher wie ein Bastler und nicht wie ein Konstrukteur? ā¢Ā Was sagt uns die Ontogenese Ć¼ber die Evolution und die Phylogenese? ā¢Ā Ist die frĆ¼he Ontogenese konservativ oder instabil? ā¢Ā Wie kann die Geschwindigkeit der Ontogenese die Morphologie und das Verhalten von erwachsenen Organismen beeinflussen? ā¢Ā Was verstehen die Kreationisten unter āPaleys Uhrā und ānichtreduzierbarer KomplexitƤtā?
Zambian common mole-rats are subterranean rodents that live in families with only one female bree... more Zambian common mole-rats are subterranean rodents that live in families with only one female breeding. Her offspring remain in the parental nest and do not reproduce. Behavioral experiments (Burda, '95) demonstrated that their apparent "sterility" is based on incest avoidance and individual recognition of family members. To elucidate whether some kind of morphologically apparent ovarian suppression still takes place in daughters, ovaries of females of known age, weight, and reproductive histories were examined histologically and morphometrically. The body mass of old females (more than 3 years of age) begins to decrease, and the ovaries seem to begin to atrophy at the age of about 3-6 years. Ovaries in neonates exhibited primordial and primary follicles, sometimes clustered in nests. Ovaries of adult nonbreeding females expressed all stages of the follicular development up to tertiary follicles. Many unruptured luteinized follicles were present, but true corpora lutea as a morphological sign of ovulation were missing. Unruptured luteinized follicles also could be found (additionally to true corpora lutea) in ovaries of breeding females. The number of primordial follicles dropped rapidly during the first 2 years of age; the number of primary, secondary, and tertiary follicles was subject to individual variation; and there was no clear correlation with age or reproductive status. While a tendency to form accessory unruptured luteinized follicles may just reflect taxonomic affinities of bathyergids to hystricomorphs, the otherwise complete folliculogenesis in "sterile" daughters and the presence of unruptured luteinized follicles even in breeding females are further evidence that there is no hormonal suppression of the ovarial cycle. We suggest that ovulation in nonbreeding females is not actively suppressed by the breeding female, but instead that it is not released because the triggering mechanisms, most probably repeated copulation, are missing.
Since the spatial mobility of subterranean mole-rats is restricted and their skull strongly modif... more Since the spatial mobility of subterranean mole-rats is restricted and their skull strongly modified, morpho-functional regression of their vestibular organ may be expected. On the other hand, vestibular sense may be indispensable for orientation in a world deprived of most external sensory cues. Since vestibular sensitivity is determined by the size of the labyrinth, morphometrical analysis may be employed to assess the sensitivity and to test whether the organ is degenerate or progressively specialized. We analyzed the shape and size of the membranous labyrinth of vestibular organs in toto in three species of African subterranean blind mole-rats of the genus Cryptomys (Bathyergidae) differing in body size yet not in habitats, ways of life, or employed orientation and locomotory strategies. The mechanical sensitivity of the cupula was estimated according to Oman et al. (1987. Acta Otolaryngol. (Stockh.), 103:1-13) for each of the three semicircular ducts. The size and shape of the vestibular organ changed predictably depending on species-specific (yet not individual) body mass. In some aspects, particularly the cross-sectional area, the ducts were larger than expected for a mammal of a comparable body size. In all species examined, the anterior semicircular ducts exhibited the highest sensitivity. The vestibular organs of blind subterranean mole-rats are not regressed morpho-functionally.
Uploads
Papers