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fgene-10-00048 February 1, 2019 Time: 17:55 # 1
REVIEW
published: 05 February 2019
doi: 10.3389/fgene.2019.00048
Edited by:
Pamela Burger,
University of Veterinary Medicine
Vienna, Austria
Reviewed by:
Pablo Orozco-terWengel,
Cardiff University, United Kingdom
Margarida Matos,
Universidade de Lisboa, Portugal
*Correspondence:
Hasan Alhaddad
hassan.alhaddad@ku.edu.kw
Specialty section:
This article was submitted to
Evolutionary and Population Genetics,
a section of the journal
Frontiers in Genetics
Received: 15 October 2018
Accepted: 21 January 2019
Published: 05 February 2019
Citation:
Alhaddad H and Alhajeri BH
(2019) Cdrom Archive: A Gateway
to Study Camel Phenotypes.
Front. Genet. 10:48.
doi: 10.3389/fgene.2019.00048
Cdrom Archive: A Gateway to Study
Camel Phenotypes
Hasan Alhaddad*and Bader H. Alhajeri
Department of Biological Sciences, Kuwait University, Kuwait City, Kuwait
Camels are livestock that exhibit unique morphological, biochemical, and behavioral
traits, which arose by natural and artificial selection. Investigating the molecular basis
of camel traits has been limited by: (1) the absence of a comprehensive record of
morphological trait variation (e.g., diseases) and the associated mode of inheritance,
(2) the lack of extended pedigrees of specific trait(s), and (3) the long reproductive
cycle of the camel, which makes the cost of establishing and maintaining a breeding
colony (i.e., monitoring crosses) prohibitively high. Overcoming these challenges requires
(1) detailed documentation of phenotypes/genetic diseases and their likely mode of
inheritance (and collection of related DNA samples), (2) conducting association studies
to identify phenotypes/genetic diseases causing genetic variants (instead of classical
linkage analysis, which requires extended pedigrees), and (3) validating likely causative
variants by screening a large number of camel samples from different populations.
We attempt to address these issues by establishing a systematic way of collecting
camel DNA samples, and associated phenotypic information, which we call the “Cdrom
Archive.” Here, we outline the process of building this archive to introduce it to other
camel researchers (as an example). Additionally, we discuss the use of this archive to
study the phenotypic traits of Arabian Peninsula camel breeds (the “Mezayen” camels).
Using the Cdrom Archive, we report variable phenotypic traits related to the coat (color,
length, and texture), ear and tail lengths, along with other morphological measurements.
Keywords: camel biobank, camel breed, camel ear, coat color, hair length, hair texture, Mezayen, tail length
INTRODUCTION
Dromedary camels (Camelus dromedarius Linnaeus, 1758) are exceptional livestock animals
because of their natural adaptations to hot sandy desert environments (Schmidt-Nielsen, 1959;
Abu-seida et al., 2012;Eshra and Badawy, 2014) and their artificially selected traits (Farah, 1993;
Khalaf, 1999;Kadim et al., 2008;Teague, 2009;Kagunyu et al., 2013).
Despite the seemingly large variation in physiological, biochemical, morphological, and
behavioral traits, the camel has received little attention with regard to the documentation of these
traits, insofar as their hereditary status and their molecular basis (Burger, 2016). Using various
genetic resources (Al-Swailem et al., 2010;Wu et al., 2014;Fitak et al., 2016), few studies have
recently started to investigate the genetic basis of camel phenotypic and behavioral traits (Holl et al.,
2017;Almathen et al., 2018;Ramadan et al., 2018); mostly using the candidate gene(s) sequencing
approach (Zhu and Zhao, 2007).
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Alhaddad and Alhajeri Cdrom Archive and Camel Phenotypes
For example, sequencing the KIT (Tyrosine kinase receptor)
gene revealed the variants associated with the white-spotting
phenotype of piebald (painted) camels (Holl et al., 2017;Volpato
et al., 2017). The candidacy of this gene was established based
on findings in other animals. The KIT gene has been identified
or implicated to be related to white color or white-spotting
in alpacas (Jackling et al., 2014), cows (Fontanesi et al., 2010),
yaks (Zhang et al., 2014), pigs (Cho et al., 2011), goats (Nazari-
Ghadikolaei et al., 2018), horses (Hauswirth et al., 2013),
donkeys (Haase et al., 2015), cats (David et al., 2014), dogs
(Wong et al., 2012), mice (Geissler et al., 1988), and rabbits
(Fontanesi et al., 2014). Thus, applying a candidate gene approach
to camels requires the presence of the phenotype in other
mammals and a manageable number of candidate genes to be
sequenced.
Beyond the candidate gene approach (which requires the
existence of a similar phenotype in a related mammal), genetic
investigations in camels also includes classical linkage analysis
(Ott et al., 2015), genome-wide association (Hirschhorn and
Daly, 2005), or whole-genome sequencing approaches (Petersen
et al., 2017). All these approaches provide an opportunity to
study camel-specific characteristics, and for many cases, narrow
down the number of candidate genes to investigate. However,
several challenges hinder the implementation of these approaches
in camels. These challenges include: (1) the limited camel
genetic resources (i.e., no high-density SNP array or genome-
wide STR panel), (2) the lack of multigenerational pedigrees to
conduct linkage analyses, (3) the difficulty of obtaining a pedigree
when most camel breeders rely on mental documentation of
their crosses (Köhler-Rollefson, 1993), (4) the late breeding age
(∼4 years) and the long gestation (∼12 months) and weaning
(∼9 months) periods of camels (which prevents any attempt to
start a large scale breeding experiment) (Ali et al., 2018), (5) the
absence of a detailed record of camel traits or genetic diseases
and their likely mode of inheritance (i.e., dominant, recessive,
etc.) and heritability, and (6) the lack of camel breed registry
or recorded information, especially for desired traits (i.e., milk
volume, meat quality, coat color, racing performance, etc.).
All the aforementioned genetic approaches to study camel
phenotypes, as well as validation of phenotype-genotype
association, require a large number of carefully phenotyped
individuals of known ancestry. This necessity justifies the
assembly of a camel DNA biobank, which is implemented in
other livestock animals (Groeneveld et al., 2016;Blackburn,
2018). Accordingly, we established such a biobank, which we refer
to as the C. dromedarius Archive (“Cdrom Archive”) that consists
of biological specimens (DNA source) accompanied by detailed
specimen-associated information, such as age, sex, breed/type,
pedigree, location, and a comprehensive documentation of
morphological phenotypes in the form of photographs.
In this review, we present our methodology of collecting and
organizing each camel sample in the archive. We also use the
current samples of the Cdrom Archive to characterize six camel
breeds from the Arabian Peninsula (Majaheem, Sofor, Shaele,
Homor, Shageh, and Waddeh), with an emphasis on the variation
in the coat (i.e., color, length, and texture), ear morphology (i.e.,
shape and length), and tail length.
BUILDING AND USING THE CDROM
ARCHIVE
Data Collection and Organization
Sample-specific information of the Cdrom Archive is collected
and organized in a unified format using the SamplEase
application (Alhaddad and Alhajeri, 2018). While we propose
to collect and organize our camel specimens using the
aforementioned sample collection application, data can also be
included in the Cdrom Archive manually. The archive is currently
comprised of 163 samples that were collected during 2015
(February–April), 2016 (October–December), and 2017 (March–
April) (Figure 1A and Supplementary Table S4). We plan to
continue to add more samples (and associated phenotypic data)
to the Cdrom Archive in the future. Our long-term plan is to
make the archive available in a database on the web, which
will continuously be updated with new specimens, as they are
collected. The current Cdrom Archive specimen’s information
is listed in Supplementary Table S4, both photographs and
biological material associated with each specimen is available
upon request.
Sex Information
Females (n= 131) currently represent the majority of the samples
of the Cdrom Archive. The discrepancy in the number of female
to male (n= 19) samples is a consequence of each breeder keeping
only one or two reproductively active males in their stock at each
time (Ali et al., 2018) (Figure 1A).
Age Information
Samples from camels of various ages were collected. However, the
majority of the samples thus far were of unknown age (n= 83)
(Figure 1B). This is in part due to the lack of a written record
of the breeding stock, and the reliance on teeth appearance and
camel behavior to determine age. Most camel breeders in the
Arabian Peninsula do not keep track of the specific age of each
of their camels (i.e., number of years), but rather label their age
class generally based on their behavior, reproductive maturity,
and teeth development (Figure 2 and Supplementary Table S1).
It is thus necessary to use age categories such as juvenile, subadult,
and adult instead of years. It is always possible to deduce the
age category of each camel sampled in the Cdrom Archive by
referring to the associated photographs (see below).
Pedigree Information
Pedigree information of Cdrom samples is mostly incomplete—it
currently contains only seven trios (parents and an offspring) and
21 half-siblings (siblings sharing a single parent) (Figure 1C). It
is difficult to obtain pedigreed camel samples because breeders
in the Arabian Peninsula (1) rely mostly on a mental record of
their breeding programs (Köhler-Rollefson, 1993), (2) assign the
same name to multiple camels (which increases the likelihood
of pedigree mistakes), (3) constantly exchange/sell camels with
other breeders, and (4) use reproductively superior bull camels
for breeding (bulls are neither owned by the breeder nor present
at the time of sample collection). It is thus easier to locate and
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FIGURE 1 | Cdrom Archive sample-specific information. General counts based on (A) sex, (B) age, (C) pedigree information, (D) biological specimen type, and
(E) breed affiliation (1: Homor and 2: Shageh).
FIGURE 2 | Terminology of Mezayen camel age classes and their
approximate age in years. Each age class represents a phase in the growth of
a female camel (male terminology is similar) and does not depend on specific
number of months/years. Outer numbers are approximate number of years for
the completion of each age stage. For details regarding the terms and their
meaning refer to Supplementary Table 1.
collect trios, siblings, half-siblings, or small pedigrees than find a
multigenerational pedigree.
Biological Specimens
The biological specimens of the Cdrom Archive presently come
from whole-blood, buccal swabs, and tail-hair (Figure 1D). We
found that the most appropriate camel DNA source for the
Cdrom Archive is tail-hair follicles—this is based on its ease
of collection, transport, and storage, and because it provided
adequate DNA quantities for genetic analyses 30 tail-hail follicles
≈6µg (Alhaddad et al., 2019). The quantity of DNA, obtained
from hair follicles, is thus expected to be successfully used in
each of PCR, STR and SNP genotyping, targeted sequencing, and
whole-genome sequencing.
In the process of establishing the Cdrom Archive, we arrived at
the following recommendations to safely collect tail-hair samples
(intended as a DNA source). To avoid startling the camel, it
should be approached slowly from the front, and then it is
advisable to pet the animal to allow it to relax, before moving
toward the tail to collect the DNA sample. It was easier to
collect tail-hair samples from females, since they tend to be
more relaxed, probably since they are used to being milked
by the breeders. Unlike horses that kick posteriorly, camels
kick sideways, and thus, it is advisable when collecting tail-hair
samples to stand behind the camel, and not to its side. To collect
hair in an optimal manner, a small bundle of long tail-hairs near
the base of the tail can be wrapped around the index finger and
plucked upward. It is recommended to bind the hair bundle using
tape and discard excess hair away from the roots (tips) (since
it does not contain any DNA), before being stored in a labeled
envelope.
Geographic Distribution
GIS coordinates are automatically assigned to each collected
specimen in the Cdrom Archive using SamplEase (Alhaddad
and Alhajeri, 2018). Most of our samples so far were collected
from Kuwait (15 locations) and only nine samples come from
Saudi Arabia (all from Alhasa) Figure 3 – map generated using
ggmap R package (Kahle and Wickham, 2013;R Development
Core Team, 2018). We acknowledge that camel herds are
generally maintained in an open environment, rather than in a
closed farm, and that camel breeders change their location several
times to prevent disease due to accumulation of fecal material and
to void depleting grazing grounds. Nonetheless, GPS coordinates
can be used to accurately reference each sample to its location of
collection—this data may allow for the construction of a camel
locality heat map, that would be helpful for national census
surveys of camel populations, along with disease management
and prevention plans e.g., managing the Middle East respiratory
syndrome-MERS (Omrani et al., 2015).
Photographs
SamplEase allows for the collection of an unlimited number of
photographs for each sampled camel, which are all linked to the
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FIGURE 3 | Geographic distribution of Cdrom Archive samples from Kuwait. Samples were collected during 2015 (February–April), 2016 (October–December), and
2017 (March–April). Circle size corresponds to the number of camel samples from each breeder (location). Nine samples were collected from King Faisal University,
Saudi Arabia (not shown). Map generated using the ggmap R package.
FIGURE 4 | Ear length and shape variation between Mezayen camel breeds. (A) Majaheem camels have a distinct long-pointed ear shape, referred to as “speared”
ears, whereas (B) Malaween breeds (Sofor, Shaele, Homor, Shageh, and Waddah) all exhibit shorter ears that are “folded” or “tilted” sideways and to the back. The
white and black disks are five centimeters in diameter, which were added to extract a scale factor in subsequent morphometric analyses. Images were extracted
from Cdrom Archive photos (collected by the authors).
basic information for each camel sample. The majority of the
sampled camels in the Cdrom Archive have been photographed
multiple times—these photographs allow us to subsequently
characterize the morphological features of each sampled camel.
Sampled Breeds in the Cdrom Archive
Most of our samples presently come from Kuwait and consist
of camel breeds common in the Arabian Peninsula. The breeds
currently in the Cdrom Archive are Majaheem, Sofor, Shaele,
Homor, Shageh, Waddah, and Omani (Figure 1E). Many
alternative spellings for these breeds exist in the literature; for
consistency, we have adopted the spellings used by Porter et al.
(2016).
Studying the molecular basis of any trait is more achievable
in a breed rather than in a random bred population (Karlsson
and Lindblad-Toh, 2008). This is due to the genetic similarity
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FIGURE 5 | Tail length variation between Mezayen camel breeds. (a) Majaheem camels are characterized by long tails with a narrow tail-base. (b) Shaele, and (c)
Waddah camels, which represent the Malaween breeds, display short-tails with wide tail-bases. The white disks on the tail are reference scales (five centimeters in
diameter). Images were extracted from Cdrom Archive photos (collected by the authors).
between individuals within a breed compared to an admixed
population. The genetic similarity between members of a breed
reduces the variable sites to be investigated and enables better
localization of phenotype-associated genes. However, the concept
of a breed is a subject of historic (Lloyd-Jones, 1915) and ongoing
debates (Food Agriculture Organization of the United Nations,
2013), and applying this concept to dromedary camels is even
more debatable and harder to implement (Köhler-Rollefson,
1993;Wardeh, 2004;Dioli, 2016). Animal breeds are generally
defined based on characteristics agreed upon by breeders that are
implemented using documented breed standards, which requires
an animal registry, and a governing breed association (Food
Agriculture Organization of the United Nations, 2013). The
camel breeding community suffers from the lack any breeders’
associations or organizations – such communities often set breed
defining criteria and features for other animals. The closest
to a camel breed registry or a governing body is the Camel
Race Federation in the United Arab Emirates (Khalaf, 1999).
However, the federation is mainly focused on racing camels, and
is specialized in implementing rules for fair racing, rather than
defining breed standards.
The closest to “true” Arabian Peninsula camel breeds are the
“Mezayen” camels, a term that literally means “beauty-contest”
camels. The Mezayen camel breeds are the: Majaheem, Sofor,
Shaele, Homor, Shageh, and Waddah (Abdallah and Faye, 2012;
Porter et al., 2016;Alaibil Festival, 2017). We argue for their breed
status because (1) each breed is defined by a distinct color group
and a set recognized morphological features (Köhler-Rollefson,
1993), (2) a consensus of breed standards exists among breeders
specifically for these six breeds (Teague, 2009), and because
(3) an incentive to maintain breed standards is available in the
form of camel beauty and breeding excellence competitions,
such as the highly prized camel beauty competition of the King
Abdulaziz Camel Festival (Alaibil Festival, 2017), along with
more regional/tribal competitions (Hammond, 2007).
MEZAYEN PHENOTYPES
The phenotypes and breed designations of domesticated animals
are often more easily recognized by the breeder who selected
for the particular traits. As such, we sought out Mezayen camel
breeders to help in identifying and explaining the phenotypes
of their camels that have been targets of selection using their
common terminology. Mezayen camel breeders in the Arabian
Peninsula use specific names to describe each breed (see above),
breed subtype, and external phenotypes (Supplementary Tables
S2,S3). The breed names and phenotypes described here are
based on translations of the breeders’ Arabic terminology to
ensure correct breed and phenotype assignments when collecting
Cdrom Archive samples (see Supplementary Tables S2,S3 for
details).
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FIGURE 6 | Mezayen camel breeds of the Arabia Peninsula and their coat colors. The six breeds are primarily divided into black vs. Malaween breeds. This division
is based on coat color and morphological characteristics (e.g., ear shape and tail length). The black breed is Majaheem whereas the Malaween camels are further
divided into five breeds based their coat color. The Malaween breeds, ranging from dark to light, are as follows: Sofor, Shaele, Homor, Shageh, and Waddah. The
outer (small) circles represent the “sub-colors” of each breed. The Majaheem sub-colors are crow-black, black, and light. The Sofor sub-colors are smoky-brown,
syrupy, and light. The Shaele sub-colors are brown, milky, and light. The Homor sub-colors are red, blackened, and twilight. The Shageh sub-colors are wheat and
light. The Waddah sub-colors are rosy, blond, and white. Coat color circles come from the Cdrom Archive photographs and were extracted from the part of the
lateral torso that is below the hump. The white disks are reference scales (20 centimeters in diameter). Breed photos were taken by Hasan Alhaddad during Mutair
Cultural Festival 2017, Kuwait. Coat color circles were extracted from Cdrom Archive photos (collected by the authors).
Mezayen camels are divided into two main groups, the dark
colored Majaheem, and the “Malaween,” which translates to
colored breeds (Sofor, Shaele, Homor, Shageh, and Waddah)
(personal observation). The separation of these two groups is in
part based on coat color, but is also based on general features,
such as body size, ear length and shape, and tail characteristics
(Köhler-Rollefson, 1993;Abdallah and Faye, 2012). Majaheem
camels are generally larger, and have long “speared” ears
(Figure 4A), and a long tail with a narrow tail-base (Figure 5a)
(Al-Hazmi et al., 1994). On the other hand, all Malaween
breeds exhibit comparatively smaller body sizes, have short
and tilted ears (Figure 4B), and a short tail with a wide tail-
base (Figures 5b–c) (see Supplementary Table S2 for naming
details). Breeders often do not breed Majaheem camels with
any of the Malaween breeds, and when such an event occurs,
breeders can easily recognize the hybrid due to changes in body
features; such hybrids are often disqualified from competing in
beauty competitions (personal observation). The Malaween are
subdivided based on their coat color (Porter et al., 2016).
Coat Color
Each Mezayen camel breed represents a color class (major color
under which several varieties exist) (Figure 6). Broadly, the six
color classes are black (Majaheem), smoky-brown (Sofor), brown
(Shaele), red (Homor), wheat (Shageh), and white (Waddah)
(Porter et al., 2016). Within each breed, a number of subtypes
exist, which correspond to fine differences in coat color tone
(Figure 6 – outer circle) (see Supplementary Table S2 for
naming details). For example, under the broad black color
class of the Majaheem, three subgroups are recognized. The
sub-colors of Majaheem are (1) “crow-black” Majaheem, which
as the name suggests, have a black coat color similar to the
“blackness” of crow feathers, (2) “black” Majaheem are referred
to by breeders as black, but is dark-brown color, that is
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FIGURE 7 | Camel coat length and texture variation. (A) Long and short coats, respectively. (B) “Ringed” (curly) and straight camel coat textures, respectively. The
Cdrom Archive contains samples of both identified coat texture phenotypes from various Mezayen breeds (B). Images were extracted from Cdrom Archive photos
(collected by the authors).
FIGURE 8 | Dark coat “highlights” of the “Syrupy” Sofor phenotype. “Syrupy”
Sofor camels show a darker coat color, located on (a) the withers, (b) the top
of the neck, (c,d) the dorsal footpad and toes, and (e) the tip of the hump.
The name of this breed is inspired by the camel breeders’ imagination, where
the camel extremities “seem” as if they were “dipped in date syrup.” Photo
was taken by Hasan Alhaddad during Mutair Cultural Festival 2017, Kuwait.
similar to darkly roasted coffee beans, and (3) “light” Majaheem
have a dark brown coat color with scattered light-colored
hairs.
Camel coat colors have been recently investigated by
sequencing two candidate genes MC1R (melanocortin 1 receptor)
and ASIP (agouti signaling protein) (Almathen et al., 2018).
Polymorphisms within the two candidate genes are found to be
associated with broad color classifications (i.e., a single variant for
black and dark brown colors) (Almathen et al., 2018). The color
classifications presented here are more refined and are suspected
to identify additional associated variants within MC1R and ASIP
of each color (if they exist) or unravel a more complex genetic
basis of coat color in camels.
Hair Length
Two hair length varieties (short and long) exist in each of the six
Mezayen camels (Figure 7A). Breeders least favor the long-haired
variety of each breed, especially when the hair texture is straight
(personal observation). Thus, the identification of the molecular
basis of hair length in camels may aid breeders in selecting camels
to breed based on their genotype.
Fibroblast growth factor-5 (FGF5) has been identified to be
associated with, or responsible for, long hair in many mammals,
including llamas (Daverio et al., 2017), alpacas (Pallotti et al.,
2018), donkeys (Legrand et al., 2014), sheep (Zhang et al., 2015),
goats (Wang et al., 2016), cats (Drögemüller et al., 2007), dogs
(Dierks et al., 2013), rabbits (Mulsant et al., 2010), mice (Hébert
et al., 1994), and humans (Higgins et al., 2014). It is thus
justifiable to consider FGF5 as a strong candidate gene for long
hair in Mezayen camels, and this hypothesis can be investigated
via direct sequencing.
Hair Texture
The hair texture of Mezayen camel coats comes into two varieties,
straight and ringed (Figure 7B). These two varieties occur in all
six breeds. Breeders select for curly hair that appear as rings,
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especially in the torso region, which are considered signs of
beauty and health (personal observation). To achieve the most
desirable coat for beauty competitions, breeders often select
for a combination of short and ringed coat hairs (personal
observation). The Crdom Archive currently contains 66 straight
hair camels and 47 ringed hair camels, which we aim to use
in genetic association studies—this relatively large sample size
is optimal since a large number of genes are expected to be
responsible for a curly coat (Figure 7B).
“Syrupy” Sofor Coat Color
The “Syrupy” Sofor displays a unique coat color phenotype
(see Supplementary Table S2 for naming details). This Sofor
camel subtype shows a darker coat pigmentation at some body
extremities, such as the withers, upper neck, dorsal footpad, nails,
tip of the hump, and the tail (Figure 8). This phenotype does
not occur in light colored breeds (Homor, Shagah, Waddah), but
occasionally occurs in the Shaele breed, due to its intercrossing
with the Sofor breed. This color phenotype has equivalents in
other mammals, such as the “points” coat phenotype of Siamese
and Burmese cats (Lyons et al., 2005), California rabbits (Aigner
et al., 2000), and mice (Beermann et al., 2004).
Mutations in the Tyrosinase (TRY) gene have been associated
with darker coloration in specific body parts, which arises
due to the temperature sensitivity of gene production (Lyons
et al., 2005). The close resemblance in coat phenotype between
Syrupy Sofor camels, Siamese and Burmese cats, California
rabbits, and mice, suggests that the TYR gene could be a
strong candidate for this phenotype. Direct sequencing of
the Syrupy Sofor camel genes, and the sequencing of the
genes of their counterparts of the same breed (smoky-brown
and light Sofor) could be a direct approach to study this
phenotype.
CAMEL MORPHOMETRICS
Several studies have examined the variation in body
measurements among camel breeds (Al-Hazmi et al., 1994;
Abdallah and Faye, 2012). So far, most published studies
that investigate this theme use traditional, distance-based
approaches, using calipers and measuring tape. While including
such data along with each Cdrom Archive sample would
provide valuable insights into the extent of the morphometric
differentiation among the breeds, based on our personal
experience, collecting such data manually is time-intensive
and imprecise, given the temperamentality of most of the
camels that we handled. Consequently, we developed a
standardized method of photographing the sampled camels
using the SamplEase application, where photographs are
taken in such a way as to allow for the extraction of both
linear and geometric morphometric data. We attach a
scale bar to each sampled camel prior to photography to
allow for the extraction of a scaling factor, which allows
for the conversion of pixels to real units (i.e., centimeters).
The “geometric morphometric” approach of examining
morphological variation is commonly employed to extract
data from zoological specimens (Zelditch et al., 2004;
Alhajeri, 2018), and has recently been used to characterize
morphological variation in live horses (Druml et al., 2015). More
advanced methods of quantifying morphometric variation in
camels in three-dimensions may also be implemented in the
future.
CONCLUSION
This review focused on outlining the framework of building
and sample collection of our recently developed Cdrom Archive.
This outline was intended to provide an example of how to
establish a biobank that would be useful for genetic studies,
thus we hope it would encourage others to establish similar
camel biobanks elsewhere. Using the samples collected thus
far, we introduced six camel breeds of the Arabian Peninsula
that are used in camel beauty competitions and referred to
as the Camel Mezayen contest. Using the photographs of the
Cdrom archive, we discussed the coat color variations and their
naming, as well as ear and tail variation. Where applicable,
we outlined possible genetic approaches to study the genetics
of these phenotypes and suggested likely candidate genes.
Lastly, we introduced the possibility of applying morphometric
tools to extract data from the photographs of the Cdrom
Archive, which would allow us to investigate body size and
shape variation. This review aimed to provide an example
of what can be done across camel research laboratories to
collect and characterize camel phenotypes, and possibly traits
associated with production and adaptation for future genetic
studies.
AUTHOR CONTRIBUTIONS
HA and BA collected the samples and wrote the manuscript.
FUNDING
No part of this work, including travel and sample collection,
received support from grant funding.
ACKNOWLEDGMENTS
We are grateful to Mohsen Bin Fawaz Alshaibani, the camel
expert and judge in Mezayen festivals, for his valuable
information and clarifications of the breed types, subtypes,
and phenotypes. We also thank the organizers of the Mutair
cultural festival (2017) for granting us access to the camel
shows and the judging arena. We are indebted to Kuwaiti
camel breeders (Abdulatif Alhedari, Anwar Alfadhli, Mohammed
Alefasi, Nawaf Alienizi, Adel Alothman, Waleed Alqallaf, Theyab
Alhajeri, Abdullah Alefasi, Saad Alajmi, Mutlaq Alsegyani,
Adnan Alshawaf, and Saree Alhajeri) and Faisal Almathen (King
Faisal University) for providing camel samples and information.
Frontiers in Genetics | www.frontiersin.org 8February 2019 | Volume 10 | Article 48
fgene-10-00048 February 1, 2019 Time: 17:55 # 9
Alhaddad and Alhajeri Cdrom Archive and Camel Phenotypes
SUPPLEMENTARY MATERIAL
The Supplementary Material for this article can be found
online at: https://www.frontiersin.org/articles/10.3389/fgene.
2019.00048/full#supplementary-material
TABLE S1 | Camel terminology used to describe female camel age classes. Age
terms were translated from original Arabic terms and the Arabic pronunciation is
shown in italics. Similar names are given to male camels with slight differences
related to gender changes to original terms in Arabic.
TABLE S2 | Names of “Mezayen” camel breeds and their subtypes. Names of
breeds and subtypes were translated from original Arabic terms and the Arabic
pronunciation shown in italics. The translations are near exact to what is offered by
the breeders, and in some cases the names do not exactly reflect the actual
appearance. For visual comparison refer to Figure 6.
TABLE S3 | Terminology of Mezayen camel coat texture and ear shape.
Phenotype terminologies were translated from original Arabic terms and the Arabic
pronunciation shown in italics.
TABLE S4 | Current sample list and information of the Cdrom Archive.
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Conflict of Interest Statement: The authors declare that the research was
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be construed as a potential conflict of interest.
The handling Editor and reviewer PO-tW declared their involvement as co-editors
in the Research Topic, and confirm the absence of any other collaboration.
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