Distribution and microstructure of intrarenal arteries in Bactrian Camels (Camelus Bactrianus)

Abstract

Studies and reports focusing on the Bactrian camels' kidney structure from an anatomical perspective are scanty, therefore, this work aims to systemically investigate the anatomical structure of the kidney and examine the distribution and microstructure of intrarenal arteries. Ten pairs of healthy adult kidneys from male and female Bactrian camels were used in the study. The kidney of Bactrian camel appeared like a broad bean with a smooth surface. Using artery casting, we observed that the renal artery divided into dorsal and ventral branches; the dorsal branch continuously divided into a shorter anterior branch and a longer posterior branch, while the ventral branch directly divided into interlobar arteries. The number of interlobar arteries in the left and right kidneys were slightly different, 14 to 16 in left while 16 in the right kidney. No anastomosis was found between the dorsal and ventral branches or their sub-branches. To further study the microscopic structure, microanatomy and scanning microscope were used. Surprisingly, we observed two other ways afferent arteriole arose apart from the interlobular artery. They were the arcuate artery and conjoint afferent arteriole. Two afferent arterioles supplied one glomerulus and occasionally the absence of glomerulus was also observed, where the arteriole kept extending, and no typical glomerulus formed. Since branching of arteries and urologic function of kidneys are physiologically integrated, these features of Bactrian camel may help to further investigate their adaptations to desert climate.

Full text

Summary. Studies and reports focusing on the Bactrian
camels’ kidney structure from an anatomical perspective
are scanty, therefore, this work aims to systemically
investigate the anatomical structure of the kidney and
examine the distribution and microstructure of intrarenal
arteries. Ten pairs of healthy adult kidneys from male
and female Bactrian camels were used in the study. The
kidney of Bactrian camel appeared like a broad bean
with a smooth surface. Using artery casting, we observed
that the renal artery divided into dorsal and ventral
branches; the dorsal branch continuously divided into a
shorter anterior branch and a longer posterior branch,
while the ventral branch directly divided into interlobar
arteries. The number of interlobar arteries in the left and
right kidneys were slightly different, 14 to 16 in left
while 16 in the right kidney. No anastomosis was found
between the dorsal and ventral branches or their sub-
branches. To further study the microscopic structure,
microanatomy and scanning microscope were used.
Surp risingly, we obs erved two other ways affe rent
arteriole arose apart from the interlobular artery. They
were the arcuate artery and conjoint afferent arteriole.
Two afferent arterioles supplied one glomerulus and
occasionally the absence of glomerulus was also
observed, where the arteriole kept extending, and no
typical glomerulus formed. Since branching of arteries
and urologic function of kidneys are physiologically
integrated, these features of Bactrian camel may help to
further investigate their adaptations to desert climate.
Ke y w ord s: Kidney, Distribut ion, Microstr ucture,
Bactrian camel, Artery
Introduction
The Bactrian camel is one of the most important
livestock in northwestern and northern China, which
lives mainly in desert and semi-desert climates. Their
char a c t e r i s t ic tolerance to e x t r e m e temperature
differences and drought makes them the most adapted
mammals to the desert and they are colloquially known
as the boat of the desert on the Silk Road (Hasi et al.,
2018). The Bactrian camels’ adaptation manifests not
only in their contour and physique, but also closely
rela t e s to their diffe r e n t org a n st r u c t u r e s an d
idiosyncratic physiologic function (Wang and Cuisheng,
1998; Wang et al., 2000b; Laursen et al., 2016).
The kidney is the main organ of the urinary system,
and it plays an important role in metabolism and ion
balance, and its function is inseparable from the blood
vessels. Nephron is the structural and functional unit of
urine formation, when blood flows through the renal
glomerulus of the nephron, due to the pressure inside
capillaries and filtration membranes, the renal corpuscle
forms original urine by filtration, and it flows through
the renal tubule to the collecting tubule, the original
ur i ne i s rea b sorbed and the fina l uri n e is for m ed
Distribution and microstructure of intrarenal
arteries in Bactrian camels (Camelus bactrianus)
Hui Li1, Yan Cui1,2, Yali Wang1, Haiyu Qiu1, Seth Yaw Afedo1, Yufeng Huang1and Xuefeng Bai1
1College of Veterinary Medicine and 2Gansu Province Livestock Embryo Engineering
Research Center, Gansu Agricultural University, Lan Zhou, Gansu, China
Histol Histopathol (2020) 35: 279-287
http://www.hh.um.es
Offprint requests to: Prof. Yan Cui, College of Veterinary Medicine and
Gansu Province Livestock Embrio Engineering Research Center, Gansu
Agricultural University, Lan Zhou, Gansu, China. e-mail:
cuiyan369@sina.com
DOI: 10.14670/HH-18-166
Histology and
Histopathology
From Cell Biology to Tissue Engineering

(Bissinger, 1995).
The final urine concentration of different animals is
quite different. Generally, animals living in humid or
water-rich areas produce more and diluted (hypotonic)
urine, whereas animals living in drought areas or marine
high - s a l t environments p r o duce less b u t highly
concentrated (hypertonic) urine. These differences are
closely related to the structural characteristics of the
kidney (Mbassa, 1988; Beuchat, 1996).
There are some reports on Bactrian camel anatomic
structures in relation to their adaptations (Wang and
Cuisheng, 1998; Wang et al., 2000a,b; Cui et al., 2004),
however, these reports rarely emphasize the anatomic
structure of the kidney, and the studies about kidney
mostly focus on the structures of the renal pelvis only
(Sheng and Yi, 2002; Chen and Liu, 2003), with scanty
data on the distribution of arteries in kidney of Bactrian
camels.
The distribution of renal artery and renal circulation
has unique anatomical and functional significance, just
as the formation and concentration of urine have a close
relationship with the renal circulation. Taking all these
into consideration, this present work aimed at studying
the structure of the kidney and the arterial system, from
the gross and microscopic perspective, to provide some
useful basic data for future studies on Bactrian camel’s
adaptation.
Materials and methods
Animals and tissue collection
Ten healthy Bactrian camels (5-12 years old) were
enrolled for the study, 6 males and 4 females, with no
apparent diseases. All Bactrian camels used in the study
were s a c rificed via e x s a nguination at t h e local
slaughterhouse in Inner Mongolia, China, and 10 pairs of
fresh kidneys were collected for use.
All procedures and protocols involving the use of
animals were in accordance with the Animal Ethics
Procedures and Guidelines of the People’s Republic of
China, and the study was approved by the Institutional
Anim a l Care and Use Committee (IACUC) (No.
GSAUAEC-2015-007) of the College of Veterinary
Medicine, Gansu Agricultural University.
Gross anatomy and vessel casting
Five fresh kidneys were used for gross anatomy, 2
from females and 3 from male Bactrian camels. The
kidneys were cut from the median sagittal plane in order
to observe their structures.
For the purpose of demonstrating the distribution
and extent of arteries in the kidney, 6 kidneys were
used for vessel casting, 2 from females and 4 from
males. Prior to vessel casting, 5% red acrylonitrile
but a d i e n e styrene (ABS)-aceto n e containi n g 5 g
acrylonitrile butadiene styrene resin (ABS ), 50 ml
acetone, 50 ml butanone and appropriate amounts of
Sudan Ⅲ were prepared for usage. In addition, 10%
and 15% red ABS-acetone containing 10g and 15g
ABS respectively were also prepared. The compounds
were agitated continuously for 3-4 d on a shaker until
the ABS dissolved completely. A blunt needle was
connected to a rubber tube at one end and the other
end of the rubber tube connected to a 20 mL syringe.
The whole needle was then inserted into th e r enal
artery, and the 5% red ABS-acetone injected into the
renal artery under high pressure, when the artery was
filled and no compound could enter any longer, the
rubbe r tube was t i g h t e n e d with a cotton cord to
prevent leakage, the set-up was left to stand for 1-2
hours, to enable an even distribution of the solution
deep within the arteries and arterioles, after this, 10%
and 1 5 % r e d ABS- a c e tone w ere i n ject e d in a
sequent ial or der, and all other steps following the
addition of 5% red ABS-acetone were repeated. After
injecting the 15% red ABS-acetone, the set-up was
quickly put under running water for at least 24 h so the
compound would solidify to make the kidney hard.
The 5% red AB S - a ceto n e e a s ily ent e r e d the
microvasculature, whereas the addition of the 10% and
15% r ed ABS- ace tone co mpo und ensured t hat the
blood vessels were completely full. After hardening,
the kidney was corroded in 25% HCL for 5-6 d. The
corroded kidney was then put into a basin filled with
water, washed with running water, and stereoscopic
microscope was used to observe the rinsed kidney to
examine if it was clean.
Scanning microscope
Nine kidneys were used for scanning microscopy
works, 4 from females and 5 from male Bactrian camels.
The protocol used was similar to that of vessel casting,
however, just 5% red ABS-acetone was injected. After
hardening in running water, the sample was allowed to
freeze for 10 h. Different parts of frozen kidney were
chosen and cut to 1.0 cm3cubes according to standard
procedure. After 3-4 days corrosion and cleansing by
running water, the samples with dense blood vessels and
clear branches were coated with gold by ion-plating
machine (Eiko-Ib-3) upon dehydration with alcohol.
Sam p l e s wer e then prepar e d for o bservatio n and
ph otog raph y u sing low va cuum scanning e lect ron
microscope (SEM) (TSM-5600LV).
Measurement and statistics
Measurements were taken for afferent arteriole,
glomerulus, and efferent arteriole that were observed to
have intact structures. Care was taken to avoid any
misidentification of the afferent and efferent arterioles,
thus the incomplete structures that were destroyed by our
operations or covered by other structures were not
measured and counted. The measurement of afferent
arteriole, glomerulus and efferent arteriole were all
performed by SEM.
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Intrarenal arteries in Bactrian camels

Results
Anatomic structure of the kidney
The kidney of Bactrian camel showed a broad bean
sh ape with a sm ooth surface (F ig. 1A). T he rena l
medulla was much thicker than the cortex (Table 1) and
the medullary/cortical thickness ratio was about 4:1, the
bound ary be tween them wa s c lea r. O n t he median
sagittal plane, about 10 conical renal pyramids were
visible and while their boundaries were unclear, these
pyramids converged to a renal crista which was concave
and par all el to the cortex (F ig. 1B). With d eta iled
observation, the me dul lar y ray was obvious at cut
surface and extended into the cortex (Fig. 1C). The renal
pyramids were separated from each other by branches of
renal pelvis at 0.5 cm away from the median sagittal
plane, where the pseudopapillae formed, after blunt
stripping the renal crista, the funnel-shaped renal pelvis
and its fan-shaped branches could be observed, the
spaces between these branches were the renal recesses.
The renal pelvis narrowed to form the ureter (Fig. 1D).
The pattern of the renal recesses is presented in Fig. 1E.
Branches of artery
The renal artery was separated from the abdominal
aorta and divided into dorsal and ventral branches at 4-8
281
Intrarenal arteries in Bactrian camels
Fig. 1. Anatomy structure of Bactrian camels’ kidney. A. Appearance the kidney. The kidney has a broad bean shape with smooth surface; the left
kidney is a little bigger. B. Median sagittal plane of kidney, renal pyramids with unclear boundary and dark red color are visible, these pyramids
converge to renal crista and the color is lighter than the pyramid. C. Renal medullary ray extends to renal cortex, and the ratio of renal cortex to renal
medulla is about 1:4. D. The renal pelvis and recesses. 0.5 cm away from the median sagittal plane, the renal pelvis branches to a fan-shaped
structure, the spaces between the branches are the renal recesses, at the end of the branch it forms a structure in the shape of a crescent that
separates renal pyramids from each other and pseudopapillae form. E. Pattern of renal recesses. RPy: Renal pyramids; RC: Renal crista; C: Renal
cortex; M: Renal medulla; RP: Renal pelvis; U: Ureter; Re: Recesses; PP: pseudopapillae; Arrowhead: Renal medullary ray.
Table 1. The thickness of cortex and medulla.
Region Maximum diameter Minimum diameter Average diameter
Cortex 1.6 1.1 1.3
Medulla 4.9 4 4.5
Note : 22 posit io ns of 5 ki dneys were selecte d for meas ur in g the
thickness of cortex and medulla. Unit: cm.

cm away from the renal hilum; they extended forward to
the renal parenchyma and kept branching. (Fig. 2A). No
anastomosis was found between the dorsal and ventral
branches or their sub-branches (Fig. 2B). The dorsal
branch divided into a shorter anterior branch and a
longer posterior branch in both left and right kidneys.
The anterior a n d poste r i o r branch a p peared t o
continuously branch to form the interlobar artery, but the
number of interlobar arteries was different in the left and
right kidneys; there were 6 to 8 in the left while there
were 8 in the right kidney (Fig. 2C). Unlike the dorsal
bran c h , th e ventral branc h di r e ctly divided to 8
interlobar arteries in the left and right kidneys with no
anterior and posterior branches. As branching continued,
the arcuate artery divided, appeared slanted, and not
parallel to the surface of the kidney. Interlobular artery
shot off from the arcuate artery at an acute angle and
ap pear ed s mooth an d or derly (F ig. 2D), it pas sed
thr ough th e r enal co rtex an d s hot out th e a ffe rent
arteriole.
Afferent arteriole
The afferent arteriole extended forward in a spiral
manner with lots of narrowing toroidal rings seen on the
surface (Fig. 3A). Through measurements and statistics,
it was found that the diameter and length of afferent
arterioles changed significantly in different zones of the
renal cortex. At the superficial zone, the terminal of the
interlobular artery extended to the afferent arteriole
directly and resulted in an afferent arteriole with the
shortest length, having an average diameter of 42.8 μm
(r ange : 3 6 μm ~7 1 μ m). There was more s teno sis
compared to the other zones (Fig. 3B). At the deep zone,
afferent arteriole separated from interlobular artery at a
right angle or an acute angle, with the length being a
282
Intrarenal arteries in Bactrian camels
Fig. 2. Artery distribution of Bactrian camels’ left kidney through renal artery vasculature casting, illustrating the branching patterns of the renal artery.
A. The renal artery divides into dorsal branch and ventral branch at a place 4-8cm away from the renal hilum, they branch forward to the renal
parenchyma, and the arteries of kidneys are sparsely internal and densely surfaced. B. Separate from dorsal branch and ventral branch, the kidney
artery can be divided into two unbroken parts. C. Branches of dorsal branch, it divided to anterior branch and posterior branch first, and progressively
branches to interlobar artery, arcuate artery and interlobular artery. D. The ventral branch divides into the interlobar artery directly, and then branches
to arcuate artery and interlobular artery. R.A: Renal artery; D: Dorsal branch; V: Ventral branch; RH: Renal hilum; White arrow: Anterior branch; Black
arrow: Posterior branch; IA: interlobar artery; AA: Arcuate artery; Arrowhead: Interlobular artery.

little longer than in the superficial zone (Fig. 3C) and the
diameter was 46.7 μm (range: 33-65 μm). The afferent
arteriole had the longest length and the largest diameter
(54.0 μm) at the juxtamedullary zone. The diameter
ranged from 37-66 μm (Fig. 3D, Table 2).
In our study, the number of afferent arterioles in
glomerulus was not consistent, most of them had just
one afferent arteriole, but occasionally two were also
observed to supply a glomerulus (Fig. 4A). We also
found that apart from the interlobular artery, arcuate
artery could also give rise to afferent arteriole (Fig. 4B).
An afferent arteriole divided into two branches before
su p p lying the glom e r ulus, one bran c h sup p l ied a
glomerulus and the other extended forward to supply a
different glomerulus (Fig. 4C). This means some of the
afferent arterioles arose from other afferent arterioles
that connected them, rather than from the interlobular
283
Intrarenal arteries in Bactrian camels
artery or arcuate artery. In other words, we found three
ways that afferent arteriole arose in Bactrian camels. In
addition to interlobular artery which is well known,
afferent arteriole could also arise from the arcuate artery,
and a conjoint afferent arteriole.
Fig. 3. Characteristic structures of afferent arteriole. A. Appearance of afferent arteriole, it shoots forward spirally with lots of narrowing toroidal rings
(×130). B-D, Diameter and length of afferent arteries in superficial (×60), deep (×50) and juxtamedullary zone (×30). AA: Arcuate artery; IA: Interlobular
artery; Af: Afferent arteriole; Gl: Glomerulus; Ef: Efferent arteriole.
Table 2. The diameter contrasts of afferent arteriole.
Region Afferent arteriole
Maximum diameter Minimum diameter Average diameter
Superficial zone 71 36 42.8
Deep zone 65 33 46.7
Juxtamedullary zone 66 37 54.0
Note: 100 Bactrian camel afferent arterioles were observed, measured
and quantitatively analysed. Unit: μm.

of 291.7 μm (range: 252-339 μm), but the number was
slightly reduced. The glomerulus with average diameter
of 317.7 μm (range: 267-383 μm) had the largest volume
at the juxtamedullary zone whereas the number was
significantly reduced (Table 3). While comparing and
Glomerulus
Renal glomerulus of Bactrian camel were mostly
round (92%) or oblate (7%), and occasionally irregular
in shape (1%), with a shape of “grape-string” on the
dis t a l end o f inte r l o b u lar ar t e r y. The g l omerular
capillaries were wrapped loops in renal capsule and their
diameters ranged from 5 μm to 25 μm. Studies under
microanatomy and scanning microscopy have shown
that differences in glomeruli exist in different cortical
zones, not only in their shapes and sizes, but also in their
densities. The glomerulus at superficial zone had the
smallest volume, its average diameter was 273.1 μm
(range: 221-369 μm), and with the highest distribution
density, most glomeruli in the kidney were concentrated
here. It was bigger at deep zone with average diameter
284
Intrarenal arteries in Bactrian camels
Fig. 4. Character of afferent arteriole and glomerulus. A. Two afferent arterioles supplying a glomerulus (arrow) were observed occasionally in Bactrian
camels (×100). B. The afferent arteriole arises from the arcuate artery, there is some man-made damage (big arrow) in arcuate artery and impression
of endothelial cell nucleus (small arrow) (×55). C. The afferent arteriole arise from another afferent arteriole (arrow) (×30). D. Disappearance of the
glomerulus, the arteriole kept extending but no afferent arteriole and typical glomerulus formed (×100). AA: Arcuate artery; IA: Interlobular artery; Af:
Afferent arteriole; Gl: Glomerulus; Ef: Efferent arteriole; Pt: Post-glomerular capillary.
Table 3. The diameter contrasts of glomerulus.
Region Maximum diameter Minimum diameter Average diameter
Superficial zone 369 221 273.1
Deep zone 339 252 291.7
Juxtamedullary zone 383 267 317.7
Note: 300 Bactrian camel renal glomerulus were observed, measured
and quantitatively analysed. Unit: μm.

coun t i n g the g l omeruli, w e found it d i s a p peared
so metimes in the kidne y, w here th e arter iole ke pt
exte n d i n g b u t n o af f e r ent a rteriole and typical
glomerulus formed (Fig. 4D).
Efferent arteriole
The appearance of efferent arteriole was similar to
the afferent arteriole which extends forward in a spiral
manner, but the diameter was smaller compared to the
afferent arteriole (Fig. 5A). The diameter also changed
regularly in different zones of the renal cortex (Table. 4).
The efferent arteriole at superficial and deep zone
su ppli ed b ranc hes and for med the po stglo meru lar
capillary that surrounded proximal and distal tubules.
The efferent arteriole at the juxtamedullary zone was
extraordinarily different; the branches extended from the
efferent arteriole divided into two types according to its
number and length, the first type (fewer and shorter) was
distributed in the cortex and formed the postglomerular
capillary with branches, whereas the second type (many
and longer) extended directly down to the renal medulla,
285
Intrarenal arteries in Bactrian camels
and formed the descending vasa recta (DVR). The DVR
kept branching in the renal medulla and constituted the
postglomerular capillary which surrounded the renal
tubules, after that the postglomerular capillary gathered
into ascending vasa recta (AVR) and drained the venous
blood of the renal medulla (Fig. 5B).
Discussion
The kidney is mainly composed of renal tubules,
rena l artery, a n d the r e n a l vein, a n d Stephe n s o n
(Stephenson et al., 1976) emphasized that they were
integrated functionally. The branching and distribution
of renal artery not only determines the blood supply to
the kidney, but also affects its function to a large extent.
Although all mammalian kidneys are somewhat similar,
there are several species-specific differences in terms of
organization, microstructure and function (Horacek et
al., 1987).
Came l s have ph y s i o l o g ical, an a t o m i c a l and
beha v i o r a l ad a p t a t ion mechanisms to the desert
environment (Berlyne et al., 1978; Gebreyohanes and
Assen, 2017). The Bactrian camel and the Dromedary
are extant Old World camelids, although the qualitative
difference between them is subtle, they are considered to
be two species (Martini et al., 2018). The anatomical
struc ture of the k idn eys in th e d rome dar y and the
Bactrian camel are almost the same, both have a renal
crista and the same medullary/cortical thickness ratio.
The medu llary/cort ical thick nes s ratio is the most
important factor in relation to the ability to generate
concentrate urine, rather than the short and long looped
nephrons with similar structure and function (Schmidt-
Nielsen and O’Dell, 1961; Abdalla and Abdalla, 1979).
The g rea ter the ratio , t he higher osmoti c p ress ure
Table 4. The diameter contrasts of efferent arteriole.
Region Efferent arteriole
Maximum diameter Minimum diameter Average diameter
Superficial zone 51 25 33.4
Deep zone 57 27 36.5
Juxtamedullary zone 56 27 42.6
Note: 100 Bactrian camel efferent arterioles were observed, measured
and quantitatively analysed. Unit: μm.
Fig. 5. Characteristic structures of efferent arteriole and post-glomerular capillary. A, Appearance of efferent arteriole, it extends forward spirally and
has a smooth surface (×120). B. Post-glomerular capillary extends from efferent arteriole (×50). Af: Afferent arteriole; Gl: Glomerulus; Ef: Efferent
arteriole; Pt: Post-glomerular capillary.

structure in Bactrian camel needs to be explored and
researched further. Attention should also be paid to the
two other ways (via arcuate artery and conjoint afferent
arteriole) from which the afferent arteriole arise apart
from the interlobular artery. This means the glomerulus
can sometimes connect to each other directly through
afferent arteriole. Since this character has not been
observed in other species, further studies need to be
conducted to ascertain whether this phenomenon in
Bactrian camel relates to function or not.
In conclusion, although some results in our data need to
be explore d furth e r, we ha v e co n d u cted a mo r e
systematic and in-depth study on the general structure of
intrarenal arteries in Bactrian camels. It gives us a
clearer and more detailed understanding of the Bactrian
camels' environmentally adaptive nature. These results
will not only provide an understanding of the kidney
st ructure of Bactri an camels a nd insi ghts in to the
diversity of species, but are also helpful for further
investigations into adaptations to desert climate.
Acknowledgements. This research was funded by the National Science
Foundation of China with Grant No. 31772691.
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environmental adaptability of the Bactrian camel.
The anatomical structure and branching of artery in
Bactrian camel’s kidney are different from humans. In
humans, a renal artery always has branches which can be
identified as posterior (P), upper (U) and lower (L). It
will also have some or all (rarely none) of the following
branches: intermediate (I), middle (M) and suprahilar
(Fine and Keen, 1966). The anatomical structure of
Bactrian camels’ kidney is like that of a horse, sheep,
dog, or rabbit (Pfeiffer, 1968; Bragulla et al., 2006;
Marques-Sampaio et al., 2007). But in the horse, the
renal medulla heals completely while in the Bactrian
came l , it heal s incompletely an d has so m e
pseudopapilla. This feature makes it more similar to the
kidn ey structure in sheep, but the number of rena l
pyramids is different from Bactrian camel’s. The renal
artery in Bactrian camel divides into dorsal and ventral
branches, and it is the same as in sheep (Michalczyk et
al., 1985; Buys-Goncalves et al., 2016), and rabbit
(Shalgum et al., 2012).
The numbers of interlobar arteries in the left and
right kidneys are different in different Bactrian camels
(14 to 16), and our result is also different from previous
reports (12 or 13) (Sheng and Yi, 2000). Numerous
reports have indicated the common variation of arteries
in kidneys (Khamanarong et al., 2004; Pereira-Sampaio
et al., 2004; Marques-Sampaio et al., 2007; Daescu et
al ., 2 012), we als o sp ecula te t hat this ana tomic al
variation in arteries may exist in multiple species, and
the variation in Bactrian camel is mainly reflected in
interlobar artery. The distinction in numbers is not a
pathological phenomenon or experimental error, but due
to individual differences. Anastomosis and distribution
of the renal artery are key points during clinical local
resection of the kidney. The multiple variation s of
arteries in different species further remind us about the
need for preoperative angiography.
In our research on microstructure, the afferent
arter iole, efferen t a rteriol e, glomeru lus, and p ost-
glomerular capillary, all have linear changes in different
zo nes in the ki dney, and it’s th e sa me as i n ot her
mammals. Our interest rests on the sometimes
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Accepted September 19, 2019