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Would the Cephalic Development in the Purebred Arabian Horse and Its Crosses Indicate a Paedomorphic Process?
Arcesio Salamanca-Carreño1, Pere M Parés-Casanova2, Néstor Ismael Monroy-Ochoa1
1Facultad de Medicina Veterinaria y Zootecnia, Universidad Cooperativa de Colombia, Villavicencio 500001, Colombia.
Insights
Paedomorphosis in horses is explored, revealing that the concave head profile in foals persists into adulthood in PAH and F1 crossbreds. This finding supports the hypothesis of retained juvenile traits in these horse breeds.
Area of Science:
- Animal Science
- Evolutionary Biology
- Morphology
Background:
- Paedomorphosis, the retention of juvenile features in adult organisms, is a significant evolutionary mechanism.
- Understanding paedomorphosis in domestic animals like horses can provide insights into developmental biology and breed characteristics.
Purpose of the Study:
- To investigate the presence and characteristics of paedomorphosis in the head profile of Pure Arabian (PAH) and F1 crossbred horses.
- To determine if the juvenile concave head profile is retained in adult PAH and F1 crossbreds.
Main Methods:
- Geometric morphometrics was employed to analyze the lateral head profiles of 99 horses (stallions, mares, geldings).
- 23 landmarks were identified, and Principal Component Analysis reduced these to 14 key variables for analysis.
- Statistical tests, including NPMANOVA and multivariate regression, were used to assess profile differences and relationships.
Main Results:
- All studied horses exhibited a concave celloid lateral left head profile.
- An isometric relationship was confirmed between the juvenile and adult concave head profiles.
- The study found that adult PAH and F1 crossbreds retain the concave celloid profile observed in juveniles.
Conclusions:
- The results support the hypothesis that PAH and F1 crossbred horses exhibit paedomorphosis.
- The retention of the juvenile concave head profile in adults is a defining paedomorphic trait in these horse populations.
Abstract:
This study examined paedomorphosis in PAH and F1 crossbreds. A sample of 99 horses was selected from 40 different breeders and consisted of three groups: stallions (n = 16), mares (n = 53), and geldings (n = 30), ranging from 10 months to 27 years in age. All horses presented a concave celloid lateral left head profile in the acquired photographic images. The hypothesis proposed in this study suggested the lateral profile of the head in juveniles was representational in the adult form due to the neonate's facial bones (part of the splanchnocranium) developing at a different rate to those of the skull. The methodology utilized geometric morphometrics to identify 23 landmarks so as to identify profile curvature indicative between the three groups (stallions, mares, and geldings). Principal component analysis reduced the number of variables to 14 examinable landmarks. Using a two-NPMANOVA and multivariate regression test, it was demonstrated that an isometric relationship between the concave celloid profile in the juvenile and its adult counterpart existed. This result supported the hypothesis that PAH and F1 crossbreds expressed a paedomorphic trait due to the adult form retaining the concave celloid profile identified in the juvenile.
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