Abstracts from the 35th Annual Meeting of The Japanese Society for Comparative Physiology and Biochemistry
第35回日本比較生理生化学会大会

2013 Hikaku seiri seikagaku(Comparative Physiology and Biochemistry)  
The glomerulus is a primary-urine producing apparatus in vertebrate kidneys, which is structurally divided into vascular and epithelial regions. The vascular region is the core structure of the glomerulus and consists of the capillary loops and mesangium. This region is surrounded by the epithelial region, a sheetlike structure, which consist of podocytes and glomerular basement membrane (GBM) and is a main portion of glomerular filtration barrier. Thus, the epithelial region keeps an
more » ... rular blood pressure within the vascular region, and the pressure is crucial as a driving force for the glomerular filtration of blood plasma. Birds and mammals can efficiently produce a large amount of primary urine in comparison with other vertebrates, since they possess quite higher intraglomerular (blood) pressure. These animals therefore need to furnish their glomeruli with some mechanical protectors to prevent the higher intraglomerular pressure from breaking down the epithelial region. To identify the mechanical protectors of the glomerulus, we compared the glomerular ultrastructure between the high-blood-pressure animals (birds and mammals) and lowblood-pressure ones (from hagfish and lamprey to reptiles). From this comparative analysis, we determined four kinds of subcellular structure as mechanical protectors of glomerulus in mammals. (1) Actin bundles in podocytes. This is a tightly-bundled actin filaments in the podocyte foot processes, by which podocytes adhere to the outer surface of GBM. The actin bundles are not direct contact with a basal plasma membrane, but it is linked the membrane via the cortical actin network. The actin bundles thus contributes to the local strengthening of GBM. (2) Actin filament condensations (AFCs) in podocytes. AFCs are found in the irregularly-shaped thick processes of podocytes, which occupied the angle between the adjacent capillary loops. AFCs link the GBM of adjacent capillary loops, and the linkage contribute to the stabilization of the folding pattern of the GBM. (3) Well-developed stress fibers in mesangial cells. These stress fibers link to the inner surface of GBM and pull it inward to prevent the over-expansion of the epithelial regions. (4) Extraglomerular mesangium. This tissue is a tectum sealing the glomerular vascular hilum, and prevents the leakage of intraglomerular pressure from the hilum and the expansion of it. These structures are peculiar to the mammalian glomerulus and are not found in the lower vertebrate glomerulus at all. To reveal the molecular mechanisms underlying the formation and maintenance of the mechanical protectors is our next future issue. Recent theories (e.g. social intelligence hypothesis) predict that selection favors enhanced social cognitive ability such as individual recognition in animals living in higher sociality. Social vertebrates recognize group members often optically, but less studied is with which visual cues and how animals use the cue for individual recognition except for some animals, e.g. apes, monkeys and sheep that can do facial recognition. Recent studies indicate that many fish species with high sociality (e.g. stable group and stable territorial neighbor) can recognize individual group members optically. Here we show for the first time the visual cue for individual recognition in fish: the cooperative breeding cichlid Neolamprologus brichardi uses facial coloration for individual identification. This fish distinguished familiar neighbors and unfamiliar strangers, and responded more aggressively against the latter (i.e. dear enemy effect). To test the facial recognition hypothesis, four types of digital fish-model, moving on a monitor display according to the same program, were exhibited to subject fish randomly: (1) neighbor, (2) neighbor face on stranger body, (3) stranger and (4) stranger face on neighbor body. The study fish were less aggressive against models (1) and (2), but were highly aggressive toward models (3) and (4) , strongly supporting the hypothesis that this fish use facial coloration for individual recognition. Our comparative study suggests that this type of facial recognition is likely to develop in group-living cichlids but rarely in non-group living fish such as monogamous pair or schooling fish, implying that not only this species but other cichlids with highly complex sociality also use facial recognition. We further confirm that this fish may discriminate the facial pattern at a glance, which would be comparable to human face recognition by means of face-neuron. We hypothesize that this fish can learn its species-specific facial color pattern easier or faster than different color patterns of similar complexity, and we assume that fish facial-recognition ability will be through special neuron-system comparable to that of human face-neuron located in the right hemisphere.
doi:10.3330/hikakuseiriseika.30.147 fatcat:x2pmh3fel5ct5i6h5okyy63nea