Renal adaptation in relation to insectivorous feeding habit in the greater mouse‐eared bat, Myotis myotis (Chiroptera: Vespertilionidae)

Abstract

We examined the histological structure of the kidneys of Myotis myotis to better understand their structural adaptations to dietary habits. M. myotis is an insectivorous bat species that belongs to the family Vespertilionidae. The kidneys of M. myotis are unilobular, bean‐shaped, and surrounded by a renal capsule. The two parts are distinguished by a thin cortex and a thicker medulla. Renal corpuscles consist of the glomerulus and Bowman's capsule. The proximal tubule consists of cubic cells with a well‐developed brush border, whereas the distal tubule is lined with a simple cubic epithelium without a brush border. The Henle's loop, located in the medullary region, was composed of flat cells. The microvilli of proximal tubule epithelial cells and basal lamina of proximal and distal tubule epithelial cells were periodic acid Schiff (PAS)‐positive. The PAS‐positive reaction of the microvilli of proximal tubular epithelial cells and basal lamina of proximal and distal tubule epithelial cells is due to the presence of glycogen, which may be used as an energy substrate during absorption. The presence of acidic glycoconjugates in the papilla was demonstrated by Alcian blue (pH 2.5)‐PAS staining. According to the result of silver impregnation staining, it was determined that reticular fibers form a dense fibrillary network in the kidney parenchymal tissue. Reticular fibers are responsible for demarcating and supporting the borders of cells by forming a thin network of fibrils beneath the basal lamina of the cells. Structural features in the kidney, such as a thin cortex and thicker medulla, long conical papilla, and division of the thick medulla into inner and outer regions, of M. myotis may be an adaptation to produce concentrated urine, thereby reducing water loss associated with insectivorous feeding habits.

Integrative single-cell characterization of frugivory adaptations in the bat kidney and pancreas

“…S3F). This is in line with previous reports that showed that fruit bats have a larger renal cortex and a smaller renal medulla compared to insectivorous bats ( 16, 17, 58 ). Additionally, we observed fruit bats to have significantly more type A intercalated cells, which are involved in acid secretion into the urine, and type B intercalated cells (Fig.…”

“…To our knowledge, our results provide for the first time an unbiased and comprehensive analysis of the cell-type compositions that distinguish insectivorous and frugivorous mammals. For the kidney, we find that the medullary and cortical differences observed between frugivorous and insectivorous kidneys (16,17,58) are due to specific nephron composition differences in DTL, TAL, connecting tubules, principal cells, type A intercalated cells, type B intercalated cells, and proximal tubules-like cells (Fig. 6).…”

Ecomorphology and sensory biology of bats

“…Bats are considered to fulfill a critical role as natural checks on insect populations (Ramírez‐Fráncel et al, 2022), and estimates of their monetary value (e.g., in lieu of pesticides) are immense (Riccucci & Lanza, 2014). As discussed in this issue by Paksuz (2023), a potential cost of insectivory is water loss, since insects have far lower water content than other food. In a histological study, Paksuz (2023) identifies microanatomical features of the kidneys in the insectivorous bat Myotis myotis that mitigate this potential water loss, such as a relatively large medullary region, where water is reclaimed and urine is concentrated.…”

“…As discussed in this issue by Paksuz (2023), a potential cost of insectivory is water loss, since insects have far lower water content than other food. In a histological study, Paksuz (2023) identifies microanatomical features of the kidneys in the insectivorous bat Myotis myotis that mitigate this potential water loss, such as a relatively large medullary region, where water is reclaimed and urine is concentrated.…”