Cdrom Archive: A Gateway to Study Camel Phenotypes

Scanning electron microscopy and morphometric analysis of the hair in dromedaries with SEM-EDX in relation to age

BACKGROUND

Hair characterization is critical for determining animal individuality throughout life. This study aimed to assess the morphological features of dromedary camel hair in relation to age.

MATERIALS AND METHODS

Hair samples were obtained from the camel humps of 30 dromedary camels separated into three groups: G1 (n:10) aged one-year, G2 (n:10) aged 3-5 years, and G3 (n:10) at the age of 8-10 years. The hair was examined using light microscopy, SEM, and SEM-EDX.

RESULTS

The Maghrebi camel had varied medulla patterns and structures across the ages. In the G1 group 75% had continuous medulla patterns and amorphous medulla structures, compared to 70% in G2, and 90% in G3. The medulla index increased with age, rising from 0.3 to 0.77%. The shaft width grew in size from G1 to G2, then fell to approximately one-third of the G2 size at G3. The cortex and cuticle widths were also determined by age, and they increased in the G1 compared to G3 camels. The shape of the cuticle scales in G1 camels was wavy, like mountain tops with irregular edges, within G2 camels the scales were particularly long, oval-shaped scales with smooth, wavy borders. The scales of the older G3 camels were quite long and rectangular. SEM-EDX spectra recognized carbon, oxygen, nitrogen, sulfur, calcium, aluminum, silicon, and potassium at the medulla and cortex. Sulfur levels were highest in the G2 samples but lowest in the G1 samples.

CONCLUSION

The dromedary camel's hair structure and mineral content, particularly carbon and nitrogen, differed as camels aged.

Towards phenotyping adaptive traits in camels: A study of the influence of hypotonic saline solutions on blood cell area

Single-humped camels are livestock of physical, physiological, and biochemical adaptations to hot desert environments and to water scarcity. The tolerance of camels to water deprivation and their exceptional capacity for rapid rehydration requires blood cells with membranes of specialized organization and chemical composition. The objectives of this study are to examine the changes in the area (a proxy for volume) of camel blood cells in solutions with decreasing concentrations of NaCl and consequently identify the conditions under which blood cells can be phenotyped in a large population. Whole-blood samples from three healthy adult female camels were treated with four different concentrations of NaCl and examined at six incubation-periods. Observationally, red blood cells in all treatments remained intact and maintained their elliptical shape while white blood cells experienced some damage, lysing at concentrations below 0.90%. Average basal (in 0.90% NaCl) RBC area was ~15 μm² and swelled in the various treatments, in some cases reaching twice its original size. Excluding the damaged cells, the average area of combined WBCs, ~32.7 μm², expanded approximately three times its original size. We find that camel WBCs, like their RBCs, are adapted to hypotonic environments, and are capable of expanding while maintaining their structural integrity.

Depraved appetite in dromedary camels: Clinical, ultrasonographic, and postmortem findings

Background

Camels are subjected to a wide variety of nutritional deficiencies as they are largely dependent upon grazing desert plants. As a consequence, the syndrome of pica or depraved appetite is occasionally seen in dromedary camels. The condition is manifested as chewing or eating abnormal things such as wood, dirt, bones, stones, clothes, plastics, mud, sand, or other inanimate objects.

Aim

This study was designed to investigate the clinical, ultrasonographic, and postmortem findings in dromedary camels with pica or depraved appetite.

Methods

Twenty-five camels of 5 days to 15 years were examined. Owner complaints included depraved appetite, loss of body condition, regurgitation of stomach content, and partial or complete absence of feces. Symptoms described were present for a period varying between 3 days, up to 12 months. The stomach compartments and small and large intestines were scanned using ultrasonography from the right and left sides of the abdomen. Necropsy was carried out on six female and three male camels where the thoracic and abdominal organs were examined with special attention to the digestive system.

Results

The affected animals had a history of gradual loss of body conditions, eating foreign objects, decreased or total absence of feces, and regurgitation of stomach content. Using ultrasound, the foreign body was imaged occluding completely or partially the intestines. Foreign bodies within the rumen could not be visualized with ultrasound. In cases where the rumen is impacted by sand, small pin-points revealing acoustic enhancement were imaged. Foreign bodies were removed from the rumen at exploratory rumenotomy (n = 11), laparotomy (n = 3), or at necropsy (n = 8) in the form of plastics, cloths, sand, mud, wool balls, robes, glasses, or even metallic objects which may be blunt or sharp. Sixteen (64%) of the camels were recovered while the remaining 9 (36%) did not survive.

Conclusion

The syndrome of pica or depraved appetite is an important condition in dromedary resulting in the ingestion of objects other than normal feed. Substantial economic losses are expected as a result of this syndrome. Ultrasonography of the digestive system may help the clinician in some cases to localize of occluding foreign bodies in the intestines, while in the transabdominal scanning of the stomach is valuable only in cases of sand impaction.

Domestication of the Dromedary Revisited and Its Consequences for Legislation as to Keeping Livestock or Pet Animals

Being in an advanced stage of domestication is a newly proposed requirement to decide which animals can be safely kept by humans. Dutch legislators were the first to apply it and other European countries may be tempted to adopt a similar approach. Unexpectedly, the Dutch assessors considered the dromedary (Camelus dromedarius) as being insufficiently domesticated and this species will therefore no longer be able to be kept as a production animal from 2024 onwards. In a recent publication on this topic, we showed that the domestication of the dromedary is actually very advanced. In this paper, we apply the same criteria that were used by the Dutch assessors to determine the degree of domestication, taking into account the most recent scientific developments in this area, even though it should be noted that these criteria have neither been peer-reviewed, nor published in an international scientific journal. For the sake of comparison, and in order to validate the procedure, we also applied these criteria to the house cat. The results confirm that the dromedary is highly domesticated, but also that the house cat (Felis silvestris catus) is at most semi-domesticated. Obviously, we agree with the decision of the Dutch legislators to place the house cat on the positive list, but our analysis demonstrates that this was decided on false grounds. Our analysis makes it clear that the requirement of being in an advanced stage of domestication is not suitable. Instead of maintaining this requirement, we recommend implementing evidence-based, peer-reviewed methods to decide which animals can be kept by humans, and to include species specific-guidelines in the legislation on how this can be achieved safely.

Exploiting morphobiometric and genomic variability of African indigenous camel populations-A review

Camels (Camelus dromedarius) in Africa are adapted to arid and the semi-arid environmental conditions, and are valuable for meat, milk and fiber production. On account of the growing demand for camels in this continent, there is a need for knowledge on their phenotypic and genetic diversity. This is fundamental to sustainable herd management and utilization including the design of appropriate breeding and conservation strategies. We reviewed studies on the phenotypic and genetic characterization, breeding objectives, systems of production, productive and reproductive performances, and pathways for the sustainable rearing and use of camels in Africa. The morphological and genetic diversity, productive and reproductive abilities of African camels suggest the existence of genetic variations that can be utilized for breeds/ecotypes' genetic improvement and conservation. Possible areas of intervention include the establishment of open nucleus and community-based breeding schemes and utilization of modern reproductive technologies for the genetic improvement of milk and meat yields, sustainable management of rangelands, capacity building of the pastoralists and agro-pastoralists, institutional supports, formation of centralized conservation centres and efficient and effective marketing systems.

Mitochondrial Sequence Variation, Haplotype Diversity, and Relationships Among Dromedary Camel-Types

Dromedary camels are outstanding livestock that developed efficient abilities to tolerate desert conditions. Many dromedary camel-types (i.e., named populations) exist but lack defined specific breed standards, registries, and breeders’ governing organizations. The breed status of dromedary camel-types can partly be assessed by exploring mitochondrial DNA (mtDNA) variation. Accordingly, this study aimed to examine the breed status and the inter-population relationships of dromedary camel-types by analyzing sequence variation in the mtDNA control region and in three coding genes [cytochrome b, threonine, and proline tRNA, and part of the displacement loop (D-loop)] (867 bp region). Tail hair samples (n = 119) that represent six camel-types from Kuwait were collected, extracted, sequenced, and compared to other publicly available sequences (n = 853). Within the sequenced mitochondrial region, 48 polymorphic sites were identified that contributed to 82 unique haplotypes across 37 camel-types. Haplotype names and identities were updated to avoid previous discrepancies. When all sequences were combined (n = 972), a nucleotide diversity of 0.0026 and a haplotype diversity of 0.725 was observed across the dromedary-types. Two major haplogroups (A and B) were identified and the B1 haplotype was predominant and found in almost all dromedary-types whereas the A haplotypes were more abundant in African regions. Non-metric multidimensional scaling revealed an increased similarity among Arabian Peninsula “Mezayen” camel-types, despite their defining coat colors. The relationships among dromedary camel-types can partly be explained by mtDNA. Future work aimed at a deeper understanding of camel-type breed status should focus on a high number of nuclear markers.

FGF5 missense mutation is associated with dromedary hair length variation

Several FGF5 mutations are associated with hair length variation in many domestic animals, including New World camelids. The dromedary was investigated in the present study with breeds exhibiting marked variations in hair length. This study aimed to: (1) identify the molecular variation(s) in the three exons of FGF5 of a diverse group of breeds (Mejaheem, Shaele, Sofor, Waddah and Omani; n = 28); (2) examine the association of the identified variants with hair length; (3) validate the association via genotyping the polymorphism in a large population of diverse camels (n = 113); and (4) test the segregation of the identified variant with hair length in a pedigree. A non-synonymous mutation (c.779 C > T) was identified that changes the amino acid from proline to leucine and was found to be associated with different hair length in dromedaries. The variants at c.779 displayed a co-dominance mode of inheritance and three hair length phenotypes: short (C/C), intermediate (C/T) and long (T/T). Across the examined dromedary breeds, both alleles were present, which is probably due to the breeders' preference for an intermediate hair length. When compared with other camelids, the identified variant was found exclusively in dromedaries with the ancestral allele at c.779 being 'C'. This study constitutes the first thorough exploration of the FGF5 gene in dromedaries.

Genetic Diversity and Population Structure of Dromedary Camel-Types

The dromedary camel is a unique livestock for its adaptations to arid-hot environments and its ability to provide goods under extreme conditions. There are no registries or breed standards for camels. Thus, named camel populations (i.e., camel-types) were examined for genetic uniqueness and breed status. Camel populations are generally named based on shared phenotype, country or region of origin, tribal ownership, or the ecology of their habitat. A dataset of 10 Short-Tandem Repeat markers genotyped for 701 individual camels from 27 camel-types was used to quantify genetic diversity within camel-types, compare genetic diversity across camel-types, determine the population genetic structure of camel-types, and identify camel-types that may represent true breeds. Summary statistics (genotyping call rate, heterozygosity, inbreeding coefficient FIS, and allelic frequencies) were calculated and population-specific analyses (pairwise FST, neighbor-joining tree, relatedness, Nei's genetic distance, principal coordinate analysis [PCoA], and STRUCTURE) were performed. The most notable findings were 1) little variation in genetic diversity was found across the camel-types, 2) the highest genetic diversity measure was detected in Targui and the lowest was in Awarik, 3) camel-types from Asia (especially the Arabian Peninsula) exhibited higher genetic diversity than their counterparts in Africa, 4) the highest DeltaK value of population structure separated camel-types based on geography (Asia vs. Africa), 5) the most distinct camel-types were the Omani, Awarik, and the Gabbra, 6) camel-types originating from the same country did not necessarily share high genetic similarity (e.g., camel-types from Oman), and 7) camel-type names were not consistently indicative of breed status.

Old World camels in a modern world - a balancing act between conservation and genetic improvement

Old World camels have served humans in cross‐continental caravans, transporting people and goods, connecting different cultures and providing milk, meat, wool and draught since their domestication around 3000–6000 years ago. In a world of modern transport and fast connectivity, these beasts of burden seem to be out‐dated. However, a growing demand for sustainable milk and meat production, especially in countries affected by climate change and increasing desertification, brings dromedaries (Camelus dromedarius) and Bactrian camels (Camelus bactrianus) back onstage and into the focus of animal breeders and scientists. In this review on the molecular genetics of these economically important species we give an overview about the evolutionary history, domestication and dispersal of Old World camels, whereas highlighting the need for conservation of wild two‐humped camels (Camelus ferus) as an evolutionarily unique and highly endangered species. We provide cutting‐edge information on the current molecular resources and on‐going sequencing projects. We cannot emphasise enough the importance of balancing the need for improving camel production traits with maintaining the genetic diversity in two domestic species with specific physiological adaptation to a desert environment.