Domestic Dog Breeds Research Articles

Whole Genome Analysis of a Single Scottish Deerhound Dog Family Provides Independent Corroboration That a SGK3 Coding Variant Leads to Hairlessness.

The breeds of domestic dog, Canis lupus familiaris, display a range of coat types with variation in color, texture, length, curl, and growth pattern. One trait of interest is that of partial or full hairlessness, which is found in a small number of breeds. While the standard for some breeds, such as the Xoloitzcuintli, requires sparse hair on their extremities, others are entirely bald, including the American Hairless Terrier. We identified a small, rare family of Scottish Deerhounds in which coated parents produced a mixed litter of coated and hairless offspring. To identify the underlying variant, we performed whole genome sequencing of the dam and five offspring, comparing single nucleotide polymorphisms and small insertions/deletions against an established catalog of 91 million canine variants. Of 325 homozygous alternative alleles found in both hairless dogs, 56 displayed the expected pattern of segregation and only a single, high impact variant within a coding region was observed: a single base pair insertion in exon two of SGK3 leading to a potential frameshift, thus verifying recently published findings. In addition, we observed that gene expression levels between coated and hairless dogs are similar, suggesting a mechanism other than non-sense mediated decay is responsible for the phenotype.

Extreme Anatomy: The Lottery Winners, Specialists, and Extreme Adaptations That Are No More.

This special issue of The Anatomical Record explores extravagant adaptions that vertebrates have evolved from their base groups to survive in the most challenging environments. It stems from a symposium entitled "Extreme Anatomy: Living beyond the edge," which was held April 23, 2017, at the annual meeting of the American Association for Anatomy, in Chicago, IL. In Part 1 of this issue, we examined extreme morphologies that allow exploration of new niches. In this issue, we return to the evolution of terrestriality by digging deeply into the fossil history of the piscine antecedent of tetrapods. These were truly "lottery winners" among vertebrates. This issue also bears on extreme specialists that once thrived but are now long extinct and some extant species that thrive in the hottest terrestrial niches. Herein, several contributions discuss developmental strategies that facilitate later demanding locomotor regimens and feeding strategies for accessing nutrients from less than ideal food sources. From mole-rats to short-faced breeds of domestic dogs, we encounter another host of the most unusual of earth's creatures, who have much to teach us about our world. Anat Rec, 2019. © 2019 American Association for Anatomy Anat Rec, 303:214-217, 2020. © 2019 American Association for Anatomy.

Abstract C098: Preclinical evaluation of eribulin in a veterinary clinical trial of metastatic spontaneous hemangiosarcoma in pet dogs

Abstract Eribulin is a microtubule dynamics inhibitor that is currently in clinical use for treatment of certain patients with advanced breast cancer or liposarcoma. FDA approval for both indications was based on extension of overall survival. Based on eribulin’s known vascular remodeling effects, its activity against at least one sarcoma type, and literature reports of taxane activity in angiosarcoma, we hypothesized that eribulin may show activity against angiosarcoma. Due to a paucity of preclinical cell-based, xenograft, and PDX models for human angiosarcoma, we sought other alternatives for preclinical testing in this disease. While rare in humans, angiosarcoma is common in some breeds of domestic dogs, where it is known in veterinary parlance as hemangiosarcoma (HSA). Accordingly, we undertook a small veterinary clinical trial to evaluate eribulin against spontaneous HSA in pet dogs. Canine HSA most frequently occurs in the spleen, so splenectomy is a common first-line treatment; however, non-splenic sites also occur and these are often unresectable. In keeping with eribulin’s clinical use in the metastatic setting, we selected metastatic canine HSA, which we defined as dogs with histologically confirmed HSA with either non-resectable or post-splenectomy residual disease confirmed by imaging (PET/CT, CT). Of 19 pets initially screened, 12 dogs were imaged; 6 of these had imageable disease and thus began eribulin treatment. Eribulin was administered using the human clinical schedule (d1,8Q21), with the first cycle at 0.3 mg/m2 followed by intra-patient dose escalation to 0.6 mg/m2 after determination of tolerability. Of the 6 dogs entering treatment, 5 completed cycle 1, 3 completed cycle 2, and 2 completed the full per-protocol 3 cycles of treatment. These 2 dogs survived 121 and 179 days after initial diagnosis, contrasting with the 0.9 month (~27 days) median survival time reported by Wendelburg et al. (JAVMA, 2015) for 52 post-splenectomy canine HSA patients with residual metastases. Although limited in scope, our results with spontaneous metastatic canine HSA in pet dogs provides a preclinical foundation for further exploration of eribulin in malignancies of vascular origin in both the veterinary and human settings. Citation Format: Christina Kelly Lopes, Gerald Post, Lindsay Lambert, Benjamin Lewis, Thaddeus David Allen, Angel Patel, Bruce A Littlefield. Preclinical evaluation of eribulin in a veterinary clinical trial of metastatic spontaneous hemangiosarcoma in pet dogs [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C098. doi:10.1158/1535-7163.TARG-19-C098

Glaucoma-causing ADAMTS17 mutations are also reproducibly associated with height in two domestic dog breeds: selection for short stature may have contributed to increased prevalence of glaucoma

BackgroundIn humans, ADAMTS17 mutations are known to cause Weill-Marchesani-like syndrome, which is characterised by lenticular myopia, ectopia lentis, glaucoma, spherophakia, and short stature. Breed-specific homozygous mutations in ADAMTS17 are associated with primary open angle glaucoma (POAG) in several dog breeds, including the Petit Basset Griffon Vendeen (PBGV) and Shar Pei (SP). We hypothesised that these mutations are associated with short stature in these breeds.MethodsTwo hundred thirty-three PBGV and 66 SP were genotyped for their breed-specific ADAMTS17 mutations. The height of each dog was measured at the withers. We used linear (per allele) regression to assess the association between ADAMTS17 mutations and height as a continuous variable, and linear regression and likelihood ratio tests to assess the shape of the association by comparing a general model with a linear (per allele) model.ResultsThe adjusted mean heights of affected, carrier, and clear PBGV were 33.49 cm (n = 21, 95% CI 32.78–34.19 cm), 34.88 cm (n = 85, 95% CI 34.53–35.25 cm), and 34.92 cm (n = 121, 95% CI 34.62–35.21 cm), respectively. The mean heights of affected, carrier, and clear SP were 43.96 cm (n = 9, 95% CI 41.88–46.03 cm), 47.56 cm (n = 28, 95% CI 45.50–48.63 cm), and 48.95 cm (n = 23, 95% CI 47.80–50.11 cm), respectively. There was a significant difference between the height of affected and clear animals in the PBGV (P = 0.001) and the SP (P = < 0.0001).ConclusionsADAMTS17 POAG mutations are significantly associated with height in these breeds.

Whole genome sequencing of canids reveals genomic regions under selection and variants influencing morphology

Domestic dog breeds are characterized by an unrivaled diversity of morphologic traits and breed-associated behaviors resulting from human selective pressures. To identify the genetic underpinnings of such traits, we analyze 722 canine whole genome sequences (WGS), documenting over 91 million single nucleotide and small indels, creating a large catalog of genomic variation for a companion animal species. We undertake both selective sweep analyses and genome wide association studies (GWAS) inclusive of over 144 modern breeds, 54 wild canids and a hundred village dogs. Our results identify variants of strong impact associated with 16 phenotypes, including body weight variation which, when combined with existing data, explain greater than 90% of body size variation in dogs. We thus demonstrate that GWAS and selection scans performed with WGS are powerful complementary methods for expanding the utility of companion animal systems for the study of mammalian growth and biology.

Genome-wide association analysis uncovers variants for reproductive variation across dog breeds and links to domestication.

Background and objectivesThe diversity of eutherian reproductive strategies has led to variation in many traits, such as number of offspring, age of reproductive maturity and gestation length. While reproductive trait variation has been extensively investigated and is well established in mammals, the genetic loci contributing to this variation remain largely unknown. The domestic dog, Canis lupus familiaris is a powerful model for studies of the genetics of inherited disease due to its unique history of domestication. To gain insight into the genetic basis of reproductive traits across domestic dog breeds, we collected phenotypic data for four traits, cesarean section rate, litter size, stillbirth rate and gestation length, from primary literature and breeders' handbooks.MethodologyBy matching our phenotypic data to genomic data from the Cornell Veterinary Biobank, we performed genome-wide association analyses for these four reproductive traits, using body mass and kinship among breeds as covariates.ResultsWe identified 12 genome-wide significant associations between these traits and genetic loci, including variants near CACNA2D3 with gestation length, MSRB3 and MSANTD1 with litter size, SMOC2 with cesarean section rate and UFM1 with stillbirth rate. A few of these loci, such as CACNA2D3 and MSRB3, have been previously implicated in human reproductive pathologies, whereas others have been associated with domestication-related traits, including brachycephaly (SMOC2) and coat curl (KRT71).Conclusions and implicationsWe hypothesize that the artificial selection that gave rise to dog breeds also influenced the observed variation in their reproductive traits. Overall, our work establishes the domestic dog as a system for studying the genetics of reproductive biology and disease.LAY SUMMARYThe genetic contributors to variation in mammalian reproductive traits remain largely unknown. We took advantage of the domestic dog, a powerful model system, to test for associations between genome-wide variants and four reproductive traits (cesarean section rate, litter size, stillbirth rate and gestation length) that vary extensively across breeds. We identified associations at a dozen loci, including ones previously associated with domestication-related traits, suggesting that selection on dog breeds also influenced their reproductive traits.

Whole genome variant association across 100 dogs identifies a frame shift mutation in DISHEVELLED 2 which contributes to Robinow-like syndrome in Bulldogs and related screw tail dog breeds.

Domestic dog breeds exhibit remarkable morphological variations that result from centuries of artificial selection and breeding. Identifying the genetic changes that contribute to these variations could provide critical insights into the molecular basis of tissue and organismal morphogenesis. Bulldogs, French Bulldogs and Boston Terriers share many morphological and disease-predisposition traits, including brachycephalic skull morphology, widely set eyes and short stature. Unlike other brachycephalic dogs, these breeds also exhibit vertebral malformations that result in a truncated, kinked tail (screw tail). Whole genome sequencing of 100 dogs from 21 breeds identified 12.4 million bi-allelic variants that met inclusion criteria. Whole Genome Association of these variants with the breed defining phenotype of screw tail was performed using 10 cases and 84 controls and identified a frameshift mutation in the WNT pathway gene DISHEVELLED 2 (DVL2) (Chr5: 32195043_32195044del, p = 4.37 X 10−37) as the most strongly associated variant in the canine genome. This DVL2 variant was fixed in Bulldogs and French Bulldogs and had a high allele frequency (0.94) in Boston Terriers. The DVL2 variant segregated with thoracic and caudal vertebral column malformations in a recessive manner with incomplete and variable penetrance for thoracic vertebral malformations between different breeds. Importantly, analogous frameshift mutations in the human DVL1 and DVL3 genes cause Robinow syndrome, a congenital disorder characterized by similar craniofacial, limb and vertebral malformations. Analysis of the canine DVL2 variant protein showed that its ability to undergo WNT-induced phosphorylation is reduced, suggesting that altered WNT signaling may contribute to the Robinow-like syndrome in the screwtail breeds.

Phenotypic disparity of the elbow joint in domestic dogs and wild carnivores.

In this article, I use geometric morphometrics in 2D from a sample of 366 elbow joints to quantify phenotypic disparity in domestic dog breeds, in wild canids, and across the order Carnivora. The elbow joint is a well-established morphological indicator of forearm motion and, by extension, of functional adaptations toward locomotor or predatory behavior in living carnivores. The study of the elbow joint in domestic dogs allows the exploration of potential convergences between (i) pursuit predators and fast-running dogs, and (ii) ambush predators and fighting breeds. The results indicate that elbow shape disparity among domestic dogs exceeds than in wolves; it is comparable to the disparity of wild Caninae, but is significantly lower than the one observed throughout Canidae and Carnivora. Moreover, fast-running and fighting breeds are not convergent in elbow joint shape with extreme pursuit and ambush wild carnivores, respectively. The role of artificial selection and developmental constraints in shaping limb phenotypic disparity through the extremely fast evolution of the domestic dog is discussed in the light of this new evidence.

The Impact of Selection for Facial Reduction in Dogs

Through artificial selection, humans have altered the morphology of domestic dogs and produced the broad range of morphological variation seen in modern dog breeds. The purpose of this study was to analyze the effects of artificial selection for short faces in domestic dogs (Canis lupus familiaris). The morphological characteristics associated with years of selection in favor of smushed, paedomorphic faces often result in Brachycephalic Airway Syndrome (BAS), which is characterized by problems with olfaction, respiration, and thermoregulation. We used clinically obtained CT scans of dogs representing brachycephalic breeds (pugs and bulldogs), normocephalic breeds (beagles), and dogs of unknown breed. We established two groups of dogs (brachycephalic and normocephalic) based on cephalic index. In both groups, we recorded a total of 62 cranial and mandibular landmarks. Through geometric morphometric analysis, we determined that the greatest shape variation in this sample was correlated with cephalic index. The shape changes in the crania and mandibles co‐vary, and are both associated with cephalic index. Within the hard palate, the majority of the shape change associated with brachycephaly is centered on the maxilla, specifically at the carnassials. The shape change seen on the hard palate is a unique lateral displacement and rotation of the carnassials, associated with shortening of the hard palate. In contrast, the shape change seen in the mandible is mainly a uniform rostral‐caudal shortening and a medial‐lateral widening. In addition, the soft palate does not appear to be reduced in these breeds. From a functional perspective, the maxillary and mandibular carnassials become malaligned in brachycephalic dogs. The shape change seen in the carnassials demonstrates that morphological integration of the carnassial complex is disrupted in brachycephalic dogs. Despite the facial reduction observed in these breeds, the soft palate does not appear to be reduced, and these soft tissues may crowd the reduced pharyngeal space. Selection for the aesthetic traits associated with brachycephaly in domestic dog breeds results in changes to the carnassial complex and pharynx that are functionally suboptimal and might limit survival outside of a domesticated environment.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Size Variation under Domestication: Conservatism in the inner ear shape of wolves, dogs and dingoes

A broad sample of wolves, dingoes, and domesticated dogs of different kinds and time periods was used to identify changes in size and shape of the organs of balance and hearing related to domestication and to evaluate the potential utility of uncovered patterns as markers of domestication. Using geometric morphometrics coupled with non-invasive imaging and three-dimensional reconstructions, we exposed and compared complex structures that remain largely conserved. There is no statistically significant difference in the levels of shape variation between prehistoric and modern dogs. Shape variance is slightly higher for the different components of the inner ear in modern dogs than in wolves, but these differences are not significant. Wolves express a significantly greater level of variance in the angle between the lateral and the posterior canal than domestic dog breeds. Wolves have smaller levels of size variation than dogs. In terms of the shape of the semicircular canals, dingoes reflect the mean shape in the context of variation in the sample. This mirrors the condition of feral forms in other organs, in which there is an incomplete return to the characteristics of the ancestor. In general, morphological diversity or disparity in the inner ear is generated by scaling.

Genomic Analyses Reveal the Influence of Geographic Origin, Migration, and Hybridization on Modern Dog Breed Development

There are nearly 400 modern domestic dog breeds with a unique histories and genetic profiles. To track the genetic signatures of breed development, we have assembled the most diverse dataset of dog breeds, reflecting their extensive phenotypic variation and heritage. Combining genetic distance, migration, and genome-wide haplotype sharing analyses, we uncover geographic patterns of development and independent origins of common traits. Our analyses reveal the hybrid history of breeds and elucidate the effects of immigration, revealing for the first time a suggestion of New World dog within some modern breeds. Finally, we used cladistics and haplotype sharing to show that some common traits have arisen more than once in the history of the dog. These analyses characterize the complexities of breed development, resolving longstanding questions regarding individual breed origination, the effect of migration on geographically distinct breeds, and, by inference, transfer of trait and disease alleles among dog breeds.

DNA methylation patterns of behavior-related gene promoter regions dissect the gray wolf from domestic dog breeds.

A growing body of evidence highlights the relationship between epigenetics, especially DNA methylation, and population divergence as well as speciation. However, little is known about how general the phenomenon of epigenetics-wise separation of different populations is, or whether population assignment is, possible based on solely epigenetic marks. In the present study, we compared DNA methylation profiles between four different canine populations: three domestic dog breeds and their ancestor the gray wolf. Altogether, 79 CpG sites constituting the 65 so-called CpG units located in the promoter regions of genes affecting behavioral and temperamental traits (COMT, HTR1A, MAOA, OXTR, SLC6A4, TPH1, WFS1)-regions putatively targeted during domestication and breed selection. Methylation status of buccal cells was assessed using EpiTYPER technology. Significant inter-population methylation differences were found in 52.3% of all CpG units investigated. DNA methylation profile-based hierarchical cluster analysis indicated an unambiguous segregation of wolf from domestic dog. In addition, one of the three dog breeds (Golden Retriever) investigated also formed a separate, autonomous group. The findings support that population segregation is interrelated with shifts in DNA methylation patterns, at least in putative selection target regions, and also imply that epigenetic profiles could provide a sufficient basis for population assignment of individuals.

Analysis of large versus small dogs reveals three genes on the canine X chromosome associated with body weight, muscling and back fat thickness.

Domestic dog breeds display significant diversity in both body mass and skeletal size, resulting from intensive selective pressure during the formation and maintenance of modern breeds. While previous studies focused on the identification of alleles that contribute to small skeletal size, little is known about the underlying genetics controlling large size. We first performed a genome-wide association study (GWAS) using the Illumina Canine HD 170,000 single nucleotide polymorphism (SNP) array which compared 165 large-breed dogs from 19 breeds (defined as having a Standard Breed Weight (SBW) >41 kg [90 lb]) to 690 dogs from 69 small breeds (SBW ≤41 kg). We identified two loci on the canine X chromosome that were strongly associated with large body size at 82–84 megabases (Mb) and 101–104 Mb. Analyses of whole genome sequencing (WGS) data from 163 dogs revealed two indels in the Insulin Receptor Substrate 4 (IRS4) gene at 82.2 Mb and two additional mutations, one SNP and one deletion of a single codon, in Immunoglobulin Superfamily member 1 gene (IGSF1) at 102.3 Mb. IRS4 and IGSF1 are members of the GH/IGF1 and thyroid pathways whose roles include determination of body size. We also found one highly associated SNP in the 5’UTR of Acyl-CoA Synthetase Long-chain family member 4 (ACSL4) at 82.9 Mb, a gene which controls the traits of muscling and back fat thickness. We show by analysis of sequencing data from 26 wolves and 959 dogs representing 102 domestic dog breeds that skeletal size and body mass in large dog breeds are strongly associated with variants within IRS4, ACSL4 and IGSF1.

The bald and the beautiful: hairlessness in domestic dog breeds.

An extraordinary amount of genomic variation is contained within the chromosomes of domestic dogs, manifesting as dramatic differences in morphology, behaviour and disease susceptibility. Morphology, in particular, has been a topic of enormous interest as biologists struggle to understand the small window of dog domestication from wolves, and the division of dogs into pure breeding, closed populations termed breeds. Many traits related to morphology, including body size, leg length and skull shape, have been under selection as part of the standard descriptions for the nearly 400 breeds recognized worldwide. Just as important, however, are the minor traits that have undergone selection by fanciers and breeders to define dogs of a particular appearance, such as tail length, ear position, back arch and variation in fur (pelage) growth patterns. In this paper, we both review and present new data for traits associated with pelage including fur length, curl, growth, shedding and even the presence or absence of fur. Finally, we report the discovery of a new gene associated with the absence of coat in the American Hairless Terrier breed.This article is part of the themed issue ‘Evo-devo in the genomics era, and the origins of morphological diversity’.

Cats and dogs cross the line: domestic breeds follow Rensch’s rule, their wild relatives do not

The domestication syndrome already recognized by Darwin shows that domesticated species acquire a number of novel morphological, physiological and behavioral characteristics not present in their wild ancestors. Because body size and sexual size dimorphism (SSD) are essential characteristics of species that affect most aspects of their life histories, we studied the effects of domestication on body size and SSD in domestic dogs and cats in comparison with their wild relatives: the Canidae and Felidae, respectively, and also analyzed the occurrence of Rensch’s rule within both domestic species. We studied maximum body mass and maximum height at withers of 64 and 89 domestic dog breeds respectively, and maximum body mass of 37 domestic cat breeds as well as body mass data for 36 wild Canidae and 36 wild Felidae from our previous studies. Our results have shown that domestic dogs maintain a level and range of body mass which largely exceeds that of the Canidae as a whole while maintaining a similar degree and range of SSD. On the contrary, domestic cats show a much reduced body mass range within the limits of their ancestor species while showing comparable levels of SSD as shown by the Felidae. Regarding Rensch’s rule, both Reduced Major Axis and Ordinary Least Squares regressions showed that both domestic species present a scaling of male and female body sizes consistent with Rensch’s rule while their wild relatives do not. We discuss these findings in the light of present knowledge about the domestication of Canis familiaris and Felis catus.

Owner-reported behavioural characteristics of dingoes (Canis dingo) living as companion animals: A comparison to ‘modern’ and ‘ancient’ dog breeds

During the domestication of canids, humans have selected for particular traits and selected against others. Wild canids and phylogenetically primitive breeds might then be expected to show less ‘desirable’ traits than more recently derived European breeds of dog. In order to examine this, we divided domestic dog breeds according to their apparent genetic relatedness to the wolf, and compared them to a wild canid, the dingo, using a validated behavioural assessment tool (C-BARQ). Our sample included 49 dingoes, 6935 modern dogs, and 673 ancient dogs. Overall, a number of differences were discovered between the breed groups, after accounting for demographic effects and variability between breeds. Dingoes were significantly less trainable than both ancient and modern dogs, and displayed greater stranger-directed fear and non-social fear than modern dogs. Dingoes were also more prone to escaping/roaming and urinating against objects than modern dogs, and tended to exhibit compulsive ‘staring’ and rolling in animal droppings more than both ancient and modern dogs. Using a multivariate test, we found that dingoes represented a significant outlier from the range of typical between-breed variation of domesticated dogs. Taken together, these results provide some evidence that (1) selective processes during domestication are reflected in the behaviour of dog breeds, and (2) primitive breed behaviour tends to reflect earlier and different selection pressures (natural rather that artificial selection).

Brown dog tick, Rhipicephalus sanguineus sensu lato, infestation of susceptible dog hosts is reduced by slow release of semiochemicals from a less susceptible host

Domestic dog breeds are hosts for the brown dog tick, Rhipicephalus sanguineus sensu lato, but infestation levels vary among breeds. Beagles are less susceptible to tick infestations than English cocker spaniels due to enhanced production of 2-hexanone and benzaldehyde that act as volatile tick repellents. We report the use of prototype slow-release formulations of these compounds to reduce the burden of R. sanguineus s. l. on English cocker spaniel dogs. Twelve dogs were randomly assigned to two groups with six dogs each. The treated group received collars with slow-release formulations of the compounds attached, while the control group received collars with clean formulations attached. Five environmental infestations were performed, with the number of ticks (at all stages) on the dogs being counted twice a day for 45days. The counts on the number of tick stages found per dog were individually fitted to linear mixed effects models with repeated measures and normal distribution for errors. The mean tick infestation in the treated group was significantly lower than in the control group. For larvae and nymphs, a decrease in tick infestation was observed at the fifth count, and for adults, lower average counts were observed in all counts. The compounds did not interfere with the distribution of the ticks on the body of the dogs, as a similar percentage of ticks was found on the anterior half of the dogs (54.5% for the control group and 56.2% for the treated group). The biological and reproductive parameters of the ticks were not affected by the repellents. This study highlights for the first time the potential use of a novel allomone (repellent)-based formulation for reduction of tick infestation on susceptible dogs.

Unaltered sequence of dental, skeletal, and sexual maturity in domestic dogs compared to the wolf.

BackgroundIt has been hypothesised that domestication altered the sequence of dental, skeletal, and sexual maturity of dogs when compared to their wolf ancestor. To test this we investigated a comprehensive sample of domestic dogs.MethodsWe documented the timing of completed eruption of permanent dentition into occlusion (dental maturity) and the timing of growth plate closure at the proximal humerus (skeletal maturity) in ontogenetic series of wolves and 15 domestic dog breeds. Data for 137 domestic dog and 64 wolf individuals were collected based on radiographs and examination of macerated bones.ResultsOur analyses show that domestic dogs exhibit a similar sequence of dental and skeletal maturity as the ancestral wolf. Although the absolute change of the age at attainment of sexual maturity is great in domestic dogs as compared to the wolf, the sequence of dental, skeletal, and sexual maturity is not altered as extensively, contradicting one previous hypothesis. Moreover, our data suggest that the chondrodystrophic dachshund attains skeletal maturity earlier than the non-chondrodystrophic breeds examined here.ConclusionsDomestic dogs are more wolf-like in terms of the sequence of dental, skeletal, and sexual maturation than previously hypothesised. This implies that the domestication process and/or breed formation did not have a major impact on this sequence, although the absolute values of life history variables do have a greater range of variation than in the wild wolf.Electronic supplementary materialThe online version of this article (doi:10.1186/s40851-016-0055-2) contains supplementary material, which is available to authorized users.

Ontogeny of domestic dogs and the developmental foundations of carnivoran domestication

Whereas hundreds of breeds of domestic dogs are known, only several dozen domestic cat breeds are currently recognized, and the ferret is not classified into specific breeds. We studied pre- and postnatal patterns of development and growth in the domesticated forms of these three carnivoran species. We present the most comprehensive staging system for domestic dog embryos to date and define qualitative characters for phylogenetic comparisons. For postnatal development, we present analyses of new and literature measurements of cranial and limb proportions. We analyze changes in the progress of growth among different domestic dog and domestic cat breeds. All three domesticated forms drastically differ in the relative timing of prenatal development. This is correlated with ontogenetic plasticity at birth, which enables artificial selection to act. For postnatal development, we detected a greater shape variance in domestic dog ontogeny when compared to that of the domestic cat. We conclude that ontogenetic preconditions as well as body size constrain the species’ capability for artificial selection in domestic dogs and cats. However, we speculate that the human requirements for functional performance of their domesticates might render some developmental biases substantially. Although ferrets would be preferable for artificial selection given their plastic embryonic development, they have been of less interest for domestication due to their small body size - by which they were already well adapted for hunting in burrows - and due to the fact that other relevant tasks were already assumed by domestic cats and dogs since earlier phases of human cultural evolution.

Observations of sacrocaudal fusion in Greyhounds and other dogs.

To describe the incidence and forms of nonpathological sacrocaudal fusion in racing Greyhounds and compare them with those in a variety of other domestic dog breeds. This retrospective observational study used archived anatomical specimens from 81 racing Greyhounds and 10 Beagles, and archived clinical radiographs from 81 non-Greyhound dogs representing 37 other breeds. Dogs less than two years of age and dogs with evidence of soft tissue or osseous pathology involving the sacrocaudal region were excluded. The incidence of osseous sacrocaudal fusion (any type and complete fusion) was compared between Greyhounds and all of the other dogs combined, using the Fisher's exact test. Sacrocaudal fusion of some type was found in 33 (41%) of 81 Greyhounds but in only 14 (15%) of 91 non-Greyhound dogs (p <0.01). Complete fusion (osseous fusion of vertebral bodies and both transverse and articular processes) between the sacrum and the first caudal vertebra was the most common form in Greyhounds, found in 27 (33%) of 81 Greyhounds, but in only three (3.3%) of 91 non-Greyhound dogs (p <0.01). Sacrocaudal fusion appears to be more prevalent in Greyhounds than in other domestic dog breeds and may be attributable to selection pressure for speed on a region of the spine that is naturally prone to variation. Its significance for performance and soundness requires further study.