THE BIOMETRIC CHARACTERISTICS OF DOMESTIC CAT SKULL IN THREE STAGES OF ITS GROWTH: JUVENILE, SUBADULT AND ADULT

Acta Sci. Pol., Zootechnica 9 (3) 2010, 65 78 THE BIOMETRIC CHARACTERISTICS OF DOMESTIC CAT SKULL IN THREE STAGES OF ITS GROWTH: JUVENILE, SUBADULT AND ADULT Marcin Stacharski, Katarzyna Pęzińska, Magdalena Wróblewska, Joanna Wojtas, Piotr Baranowski Western Pomeranian University of Technology in Szczecin, Poland Summary. This paper presents changes in the values of selected metric traits of domestic cat (Felis s. catus) taking place in three successive life stages: juvenile, subadult and adult. Study material consisted of 70 European domestic cat skulls being part of the museum collection of the Department of Animal Anatomy in Szczecin. The affiliation of respective skulls to age groups mentioned above was determined based on the degree of diaphyseal-epiphyseal fusion in shoulder and/or pelvic girdle long bones and comparison of these data with dental status. In total, 37 measurements were made on each skull. The carried out measurements showed large variation resulting from the rebuilding of particular skull segments as well as a change in proportions resulting from relations between the traits characterising their breadth and length. It was found that as many as 22 traits out of 37 ones examined showed significant changes (P 0.05 and P 0.01) with age. Słowa kluczowe: age class juvenile, subadult, adult, felids, metric measurements, skull development INTRODUCTION Particular role in the morphological picture of animal is played by its skull which, together with lower jaw, is the most diverse and complex part of skeleton. This bone complex is being used to explain problems of macro- and microevolutionary variation and makes determination of the way of life of an individual, its health state, environmental impact on animal during its life and interrelations between different populations inside the species as well as between species easier [Sotnikova and Nikolskiy 2006]. Both skull and its particular bone complexes show clear relationship between the structure and the functional usefulness [Krysiak et al. 2001]. Factors which determine the size and shape of skull within the species are breed, variety or utility type, age, sex, health state, rearing conditions, developmental anomalies induced by genetic or environmental factors and others. When examining ani- Corresponding author Adres do korespondencji: dr hab. Piotr Baranowski prof. nadzw., Department of Animal Anatomy, Western Pomeranian University of Technology in Szczecin, Doktora Judyma 14, 70-466 Szczecin, Poland, e-mail: Piotr.Baranowski@zut.edu.pl

66 M. Stacharski i in. mal age as one of the basic factors determining the shape of skull, particular attention should be paid to respective stages of the development of this part of skeleton. In the embryonic development of mammals, a cartilaginous cranium (cranium cartilagineum) forms first which later undergoes ossification. The skull of adult animal is composed both of replacing / endochondrial and dermal bones. Cranial skeleton bones are connected by syndesomoses and form sutures which show a tendency to fuse in older age and syndesmosis is being replaced by synostosis. Then, the skull forms a uniform box, with the lower jaw preserving mobility only as it is articulated with the skull [Kowalski 1971]. Head dimensions enlarge together with organism development and mutual proportions between visceral and neural parts undergo many changes [Kulewicz 2002]. Despite large phenotypic diversity presented by cats, common traits of the skull of this subfamily are, among others, as follows: shortening of its visceral part, placement of eyes in large orbits directed forward, hinge connection between the lower jaw and the skull (which prevents from side to side movements of the lower jaw and makes carnassials to fulfil the role of shears), loss of molars and reduction of premolars (in their number and shape), development of large canines, alignment of incisors in straight line, thin wall of the auditory tube and its division by two-layered septum; moreover, there is no internal branch of carotid artery entering the skull in other mammals in the auditory tube and inner ear region [Seidensticker and Lumpkin 1991]. The variation of skull size in felids may result from the way they catch and kill prey as well as differences in the size of captured animals. Dimensions of a hunted animal are correlated with the size of a cat itself. Large cats hunt proportionally larger prey than small ones and very often among the largest felids the weight of hunted animals exceeds that of a predator. Therefore, the degree of their jaw opening is large. The bite force estimated for three cat species African wild cat, panther and lion is inversely proportional to the length of jaw and the size of its opening. Wild cats with the skull length (Akrokranion-Prosthion) being proportionally the shortest against the same trait estimated in large cats are characterised by the greatest bite strength in relation to the energy released by masticatory muscles necessary for this action. Lion skulls being characterised by the smallest force are a distinctive example of this [Slater and Van Valkenburgh 2009]. The aim of this paper is to present changes in the values of selected metric traits of domestic cat (Felis silvestris catus) skull in three age stages: juvenile, subadult and adult. MATERIAL AND METHODS Examinations were carried out on 70 skulls of European domestic cat (Felis silvestris catus) of box sexes, belongingto the familyfelidae of of the order Carnivora, housed in the museum collection of the Department of Animal Anatomy in Szczecin. The age of cats was determined based on the degree of diaphyseal-epiphyseal fusion in shoulder and/or pelvic girdle long bones (Fig. 1) and comparison of these data with dental status [Habermehl 1975]. Based on this, 3 groups were distinguished, i.e. young cats juvenile (to 6 months of life), mature cats subadult (from 6 to 11.5 months of life), and adult cats Acta Sci. Pol.

The biometric characteristics of domestic cat skull in three stages... 67 adult (over 11.5 months of life). Using an electronic slide calliper (Orion 31170 150, with accuracy to 0.01 mm), 37 metric measurements were made in respective cranial planes according to von den Driesch [1976] which are presented below: Dorsal plane measurement: 1. Akrokranion-Prosthion (A-P) Total length. 2. Akrokranion-Frontal midpoint (A-F) Upper neurocranium length. 3. Euryon-Euryon (Eu-Eu) Greatest neurocranium breadth. 4. Zygion-Zygion (Zyg-Zyg) Zygomatic breadth. 5. Least breadth aboral of the supraorbital processes / Breadth of the postorbital constriction. Lateral plane measurements: 6. Greatest inner height of the orbit. 7. Height of the auditory tube. 8. Entorbitale-Ectorbitale (Ent-Ect) Greatest inner length of the orbit. 9. Entorbitale-Prosthion (Ent-P) Length from the most oral point on the anterior edge of the orbit, Entorbitale, toprosthion. 10. Basion-Akrokranion (B-A) Height of the occipital triangle. 11. Skull height (CH) measured from Basion to the point on the highest elevation on the sagittal crest. 12. Molare-Nasion (Mol-N) Length from the intersection of the median plane with the line joining the anterior border of first molars to the intersection of the sagittal suture with the frontonasal suture, Nasion. Basal plane measurements: 13. Basion-Prosthion (B-P) Basal length. 14. Basion-Synsphenion (B-S) Basicranial axis. 15. Prosthion-Synsphenion (P-S) Basifacial axis. 16. Length of the cheektooth row, P1-M1. 17. Length of the carnassial, P4. 18. Length of the premolar row. 19. Greatest palatal breadth. 20. Greatest diameter of the auditory bulla. 21. Least diameter of the auditory bulla. 22. Breadth at the canine alveoli. Nuchal plane measurements: 23. Otion-Otion (Ot-Ot) Greatest mastoid breadth / Greatest breadth of the occipital triangle. 24. Greatest breadth of the occipital condyles. 25. Akrokranion-Opisthion (A-O) Height of the occipital squama. 26. Height of the foramen magnum. 27. Breadth of the foramen magnum. Mandibular measurements: 28. Total length. 29. Height of the vertical ramus. 30. Height of the mandible between P2 and P3. 31. Length of the mandibular base. Zootechnica 9 (3) 2010

68 M. Stacharski i in. 32. Length from the condyle process to the aboral border of the canine alveolus. 33. Length from the indentation between the condyle process and the angular process to the aboral border of the canine alveolus. 34. Length of the cheektooth row, P3-M1, measured along the alveoli. 35. Length from the angular process to the aboral border of the canine alveolus. 36. Length of the carnassial, M1, along the alveolus. 37. Height of the mandible behind M1 measured on the buccal side. Fig. 1. The age of cats was determined based on the degree of diaphyseal-epiphyseal fusion in shoulder and/or pelvic girdle long bones Rys. 1. Wiek kotów był określany na podstawie stopnia zrośnięcia nasady z trzonem kości ramiennej i/lub miednicznej Furthermore, a series of photographic images of the foramen magnum were made to calculate its area using MultiScan computer programme. Photographs were made with Canon EOS 500 D camera equipped with Canon EF 60 mm lens. Also the cranial capacity was estimated by pouring calibrated rape-seed grains into the neurocranium through the foramen magnum whereas volume measurement was done with a calibrated cylinder. The area of occipital triangle was calculated according to the following formula: P = a x h/2 where: a greatest breadth between paracondyles; h Basion-Akrokranion. Acta Sci. Pol.

The biometric characteristics of domestic cat skull in three stages... 69 The empirical data obtained were entered into Statistica 8.pl database and mean values, standard deviation, minimum and maximum values were calculated as well as correlations between selected traits. Furthermore, the values of biologically reasonable cranial indices were estimated using selected skull metric traits. In view of no normal distribution of traits, the significance of differences between cat groups was determined with nonparametric Kruskal-Wallis test, at significance levels P 0.05 and P 0.01. RESULTS The carried out measurements of cat skull metric traits in three age stages (juvenile, subadult and adult) showed large variation resulting from the rebuilding of particular skull segments as well as a change in proportions resulting from relations between the traits characterising their breadth and length. It was found that as many as 22 traits out of 37 ones examined being presented in Tables 1 5 differed statistically significantly (P 0.05 and P 0.01). The age of cats was a source of variation for the traits characterising the dorsal plane of skull, i.e. for the total length (A-P) and the upper neurocranium length (A-F). For these lengths, statistically significant differences (P 0.01) were found between juvenile and adult groups, whereas significant changes (P 0.01) in case of the zygomatic breadth (Zyg-Zyg) take place in each successive period of life (Table 1). It was also found that age was a significant source of variation (P 0.05 and P 0.01) for the traits characterising the base of skull (Table 2), i.e. for the length of the basal length (B-P), the length of the basicranial axis (B-S), the length of the basifacial axis (P-S), the breadth at the canine alveoli and the length of the premolar row. The results of measurements for the metric traits of the lateral plane of cat skulls showed that age was a source of variation for such traits as: the length of the greatest inner length of the orbit (Ent-Ect), the length from the most oral point on the anterior edge of the orbit to the intersection of the line joining the most oral points of both premaxillae with the median plane (Ent-P) and the length from the intersection of the median plane with the line joining the anterior border of first molars to the intersection of the sagittal suture with the frontonasal suture (Mol-N), as well as for the greatest inner height of the orbit and the skull height (Table 3). It was found the greatest inner height of the orbit, the greatest inner length of the orbit (Ent-Ect) and the length from the most oral point on the anterior edge of the orbit to Prosthion (Ent-P) increase significantly (P 0.05) between age stages subadult and adult. On the other hand, the height expressed with measurement B-A (Table 5) and Mol-N (Table 3) increases significantly (P 0.01) in the time period between age stages juvenile and adult. It was found in the nuchal plane that the greatest mastoid breadth / the greatest breadth of the occipital triangle (Ot-Ot) as well as the cranial capacity and the area of occipital triangle (Table 5) showed significant differences (P 0.01) between age stages juvenile and adult. Age was also a source of variation (P 0.05 and P 0.01) for cranial indices (Table 6): CH/Zyg-Zyg, Eu-Eu/A-N, Eu-Eu/A-P, Eu-Eu/B-P, least breadth aboral of the supraorbital processes / breadth of the postorbital constriction /A-P, least breadth aboral of the supra- Zootechnica 9 (3) 2010

70 M. Stacharski i in. orbital processes / breadth of the postorbital constriction /B P, height of the vertical ramus/ total length, height of the vertical ramus/length of the mandibular base, length of the cheektooth row P 3 -M 1 / total length, and Ent-Ect / greatest inner height of the orbit. Table 7 presents the values of Spearman s correlation coefficients which were found for selected metric traits in three successive age stages of the examined skulls. Table 1. The values of metric traits for the dorsal plane of domestic cat skull in three stages of postnatal development Tabela 1. Wartości cech metrycznych powierzchni grzbietowej czaszki kota domowego w trzech okresach rozwoju postnatalnego Craniometric trait Cecha kraniometryczna Juvenile Młode Subadult Dojrzałe Adult Dorosłe n x sd min max n x sd min max n x sd min max Akrokranion-Prosthion 7 68.01 A 8.43 60.89 84.34 9 84.15 8.70 70.67 95.40 45 88.79 A 6.74 63.60 100.65 Akrokranion 4 24.33 A 10.35 10.09 34.45 7 42.19 5.63 35.32 49.87 41 43.41 A 4.90 33.88 56.63 Euryon-Euryon 9 40.49 1.38 38.06 42.45 12 41.68 1.01 40.49 43.70 48 41.66 1.94 36.36 44.97 Zygion-Zygion 9 52.28 A 5.55 45.44 63.60 13 58.33 B 4.29 53.07 67.43 48 63.66 AB 4.22 51.52 72.12 Least neurocranium breadth Najmniejsza szerokość czaszki mózgowej 9 31.56 0.98 29.84 32.88 12 31.75 0.86 30.27 33.14 48 30.87 2.05 26.85 35.27 Explanations: mean values in rows marked with the same lettes differ significantly at: a. b P 0.05; A. B P 0.01. Objaśnienia do tabel: średnie w wierszach oznaczone tymi samymi literami różnią się istotnie: a. b P 0,05; A. B P 0,01. Acta Sci. Pol.

The biometric characteristics of domestic cat skull in three stages... 71 Table 2. The values of metric traits for the basal plane of domestic cat skull in three stages of postnatal development Tabela 2. Wartości cech metrycznych podstawy czaszki kota domowego w trzech okresach rozwoju postnatalnego Craniometric trait Cecha kraniometryczna Juvenile Młode Subadult Dojrzałe Adult Dorosłe n x sd min max n x sd min max n x sd min max Basion-Prosthion 3 61.90 a 9.12 53.33 71.48 7 74.50 5.90 64.91 82.10 40 77.33 a 4.01 69.25 86.38 Basion-Synsphenion 3 21.63 a 1.87 19.78 23.51 7 25.77 2.17 22.07 28.60 39 26.78 a 1.61 22.89 30.51 Prosthion-Synsphenion 4 38.62 A 6.79 33.55 47.97 9 49.01 4.08 42.84 54.67 41 50.47 A 2.78 45.92 56.25 Breadth across canines Szerokość kłów 5 18.69 A 3.09 15.19 22.95 10 22.17 2.15 19.28 25.85 44 23.38 A 1.56 19.12 26.32 Length of the cheektooth row Długość zębów policzkowych 5 17.17 A 3.21 11.97 20.07 11 19.59 1.58 17.74 21.76 43 21.29 A 2.61 5.63 21.69 Length of the carnassial P 4 Długość zęba przedtrzonowego P 2 2.26 0.11 2.18 2.33 2 9.94 0.21 9.79 10.09 39 10.29 0.93 8.96 14.12 4 Length of the premolar row Długość trzech zębów 4 14.85 3.35 11.17 19.21 11 18.13 1.74 15.44 20.22 44 18.81 2.58 12.31 28.72 przedtrzonowych Palatal breadth Szerokość podniebienia Breadth of the tympanic bulla Szerokość puszki bębenkowej Length of the tympanic bulla Długość puszki bębenkowej 5 29.63 5.02 24.95 35.71 10 36.68 2.03 33.60 39.94 44 37.75 2.94 30.60 47.07 9 13.89 2.20 11.48 17.95 13 14.39 3.17 10.79 20.23 48 15.26 13.19 10.16 21.26 9 14.41 2.99 10.24 18.71 13 15.38 3.06 11.26 19.27 48 15.85 3.56 10.64 21.76 Explanations: see Table 1. Objaśnienia jak w tab. 1. Zootechnica 9 (3) 2010

72 M. Stacharski i in. Table 3. The values of metric traits for the rostral (lateral) plane of domestic cat skull in three stages of postnatal development Tabela 3. Wartość cech metrycznych części rostralnej (bocznej) czaszki kota domowego w trzech okresach rozwoju postnatalnego Craniometric trait Cecha kraniometryczna Juvenile Młode Subadult Dojrzałe Adult Dorosłe n x sd min max n x sd min max n x sd min max Entorbitale-Ectorbitale 9 22.38 A 2.78 18.09 26.44 12 26.47 a 1.68 23.60 29.05 47 28.09 Aa 1.64 22.69 32.34 Entorbitale-Prosthion 5 11.74 A 2.02 9.73 14.53 10 15.40 a 1.88 12.53 18.36 46 17.04 Aa 1.62 13.18 20.68 Molare-Nasion 3 13.12 A 1.07 11.94 14.03 7 16.66 1.52 14.79 19.00 36 18.05 A 1.67 14.95 24.29 Cranial height Wysokość czaszki 9 42.38 A 2.14 38.92 44.51 12 44.03 2.24 40.15 48.38 48 45.43 A 2.36 40.83 52.75 Height of the orbit Wysokość oczodołu Height of the tympanic bulla Wysokość puszki bębenkowej Explanations: see Table 1. Objaśnienia jak w tab. 1. 6 19.58 AB 2.52 15.84 21.86 11 23.95 A 1.80 21.05 26.43 45 24.00 B 1.35 21.14 27.76 9 11.65 0.58 10.67 12.47 12 12.20 0.97 10.70 13.83 48 12.25 1.12 10.36 14.97 Table 4. The values of metric traits for domestic cat mandible in three stages of postnatal development Tabela 4. Wartości cech metrycznych żuchwy kota domowego w trzech okresach rozwoju postnatalnego Craniometric trait Cecha kraniometryczna Height of the mandibular ramus Wysokość gałęzi żuchwy Greatest length of the mandible Największa długość żuchwy Length of the mandibular base Długość podstawy żuchwy Height of the mandibular corpus Wysokość trzonu żuchwy Explanations: see Table 1. Objaśnienia jak w tab. 1. Juvenile Młode Subadult Dojrzałe Adult Dorosłe n x sd min max n x sd min max n x sd min max 9 19.71 A 3.10 15.75 26.28 13 23.68 3.72 17.87 29.58 46 26.04 A 2.97 10.14 33.81 9 46.67 A 4.52 39.52 53.40 13 55.44 a 5.92 48.82 66.70 46 59.68 Aa 4.15 46.71 67.66 9 44.56 A 3.86 38.99 51.34 13 52.48 a 5.39 46.07 62.36 46 56.19 Aa 3.53 44.83 64.70 9 7.07 Aa 1.14 5.72 9.43 12 8.76 a 1.22 7.09 10.75 46 9.70 A 1.12 7.15 11.87 Acta Sci. Pol.

The biometric characteristics of domestic cat skull in three stages... 73 Table 5. The values of craniometric traits for the nuchal plane and the cranial capacity of domestic cat skull in three stages of postnatal development Tabela 5. Wartości cech metrycznych powierzchni karkowej oraz pojemność czaszki kota domowego w trzech okresach rozwoju postnatalnego Craniometric trait Cecha kraniometryczna Juvenile Młode Subadult Dojrzałe Adult Dorosłe n x sd min max n x sd min max n x sd min max Akrokranion-Opisthion 6 13.45 1.57 11.45 16.03 10 14.11 1.68 11.10 16.63 48 15.16 1.59 11.26 18.28 Basion-Akrokranion 7 32.06 A 2.09 29.26 34.54 9 34.27 3.16 30.18 39.80 48 36.13 A 2.22 31.73 39.82 Otion-Otion 9 35.32 A 3.76 28.35 39.69 12 38.35 2.20 35.01 42.56 48 40.27 A 3.52 28.14 50.56 Greatest breadth of the occipital condyles 6 19.20 A 0.75 18.17 20.44 10 20.54 1.06 19.05 22.05 48 20.96 A 1.20 18.36 23.66 Szerokość kłykci potylicznych Cranial capacity, cm 3 Pojemność czaszki, cm 3 A 9 98.75 3 A 15.72 77.55 122.28 12 118.97 14.12 100.27 146.67 48 131.08 A 17.60 95.27 173.48 Breadth of the foramen magnum Szerokość otworu wielkiego 5 11.79 0.42 11.44 12.46 10 12.61 0.67 11.00 13.37 48 12.55 0.70 11.21 13.93 Height of the foramen magnum Wysokość otworu wielkiego 5 9.33 0.70 8.51 10.28 10 9.47 1.04 7.91 11.27 48 9.69 0.78 8.02 11.65 Area of the foramen magnum, mm 2 Pole powierzchni 5 78.57 7.82 70.86 90.93 10 86.28 10.76 65.36 102.21 48 89.58 9.54 72.22 109.65 otworu wielkiego, mm 2 Area of the occipital triangle, mm 2 Pole powierzchni 6 207.17 A 14.27 183.84 222.37 9 240.89 30.47 205.52 292.27 47 264.93 A 27.09 197.00 320.36 trójkąta potylicznego, mm 2 Explanations: see Table 1. Objaśnienia jak w tab. 1. Zootechnica 9 (3) 2010

74 M. Stacharski i in. Table 6. The values of selected cranial indices for domestic cat in three stages of postnatal development Tabela 6. Wartości wybranych indeksów czaszkowych kota domowego w trzech okresach rozwoju postnatalnego Cranial indices Juvenile Młode Subadult Dojrzałe Adult Dorosłe Indeksy czaszkowe n x sd n x sd n x sd Zygion-Zygion / Akrokranion-Prosthion 7 74.84 7.07 9 70.97 3.95 45 71.81 3.13 Euryon-Eurryon / Akrokranion-Nasion 9 81.55 A 5.64 12 75.14 4.68 48 71.55 A 4.25 Euryon-Eurryon / Akrokranion-Prosthion 9 71.23 A 5.85 12 64.71 a 4.17 48 65.58 Aa 3.43 Euryon-Eurryon / Basion-Prosthion 7 59.63 A 5.92 9 50.22 4.98 45 47.00 A 3.65 Cranial height / Zygion-Zygion Wysokość czaszki / Zygion-Zygion 3 64.77 a 7.03 7 56.90 4.66 40 53.89 a 2.35 Least neurocranium breadth Najmniejsza szerokość czaszki mózgowej / Akrokranion-Prosthion 7 46.48 A 5.15 9 38.11 4.10 45 34.78 A 3.67 Least neurocranium breadth Najmniejsza szerokość czaszki mózgowej / Basion-Prosthion Greatest breadth of the occipital condyles Szerokość kłykci potylicznych / Otion-Otion Otion-Otion/ Basion-Prosthion Height of the orbit Wysokość oczodołu / Entorbitale-Ectorbitale Height of the mandibular ramus / Greatest length of the mandible Wysokość gałęzi żuchwy /Długość żuchwy Height of the mandibular ramus / Length of the mandibular base Wysokość gałęzi żuchwy / Długość żuchwy Length of the cheektooth row P3-M1/ Greatest length of the mandible Długość szeregu zębodołowego P3-M1 /Długość żuchwy Height of the mandibular corpus / Height of the mandibular ramus Wysokość trzonu żuchwy / Wysokość gałęzi żuchwy 3 50.66 a 5.70 7 43.11 3.97 40 39.81 a 2.91 6 53.40 7.21 10 53.24 2.60 48 52.32 4.14 3 54.00 6.81 7 53.28 1.99 40 52.14 4.29 6 88.22 3.68 11 89.68 5.74 45 85.18 5.36 9 42.68 a 9.32 13 42.59 3.69 46 43.72 a 4.42 9 44.59 a 9.12 13 44.95 3.49 46 46.35 a 4.35 9 35.78 A 2.20 13 35.35 B 2.29 46 32.82 AB 1.89 9 42.00 7.17 13 39.19 3.79 46 37.91 6.40 Acta Sci. Pol.

The biometric characteristics of domestic cat skull in three stages... 75 cont. Table 6 cd. tab. 6 Height of the mandibular corpus at the border of M1/ Height of the mandibular ramus Wysokość trzonu żuchwy przy krawędzi zęba M1 / Wysokość gałęzi żuchwy 9 40.45 7.16 13 40.15 2.99 46 39.95 6.23 Akrokranion-Prosthion / Cranial capacity 7 0.07 0.01 9 0.07 0.00 45 0.07 0.01 Pojemność czaszki Area of the occipital triangle Pole powierzchni trójkątra potylicznego 2 297.86 5.66 6 336.45 24.58 39 340.15 22.59 Basion-Prosthion Basion-Prosthion / Area of the foramen magnum Pole powierzchni otworu potylicznego 2 33.58 0.64 6 29.86 2.29 39 29.53 2.03 Entorbitale-Entorbitale / Height of the orbit 6 Wysokość oczodołu 70.60 7.04 10 67.41 a 4.68 45 72.34 a 7.26 In the group of mature cats (subadult), significant correlations (P 0.5 and P 0.01) were found between the area of occipital triangle and the the total length (A-P) (r = 0.84), the greatest breadth of the occipital condyles (r = 0.93) and the the skull height (r = 0.87). The value of correlation coefficient between the cranial capacity and the total length (A-P), the greatest mastoid breadth / the greatest breadth of the occipital triangle (Ot-Ot) and the skull height amounted to r = 0.81, r = 0.83 and r = 0.88, respectively. It was found in the group of adult cats (adult) that the values of correlation coefficients between the area of occipital triangle and such traits as the total length (A-P), the basal length (B-P), the greatest neurocranium breadth (Eu-Eu), the greatest mastoid breadth / the greatest breadth of the occipital triangle (Ot-Ot), the zygomatic breadth (Zyg-Zyg), the greatest breadth of the occipital condyles and the the skull height were high and statistically significant (P 0.05 and P 0.01). Also in the same group, there are significant correlations between the cranial capacity and the total length (A-P), the length of the basal length (B-P), the greatest neurocranium breadth (Eu-Eu), the greatest mastoid breadth / the greatest breadth of the occipital triangle (Ot-Ot), the zygomatic breadth (Zyg-Zyg), the greatest breadth of the occipital condyles and the skull height. No differences were found between the values of correlation coefficients between skull groups. No correlation was calculated in age group juvenile due to small number of specimens. Zootechnica 9 (3) 2010

76 M. Stacharski i in. Table 7. Correlations for selected metric traits of domestic cat skull Tabela 7. Korelacja wybranych cech metrycznych czaszki kota domowego Correlations Korelacja Area of the foramen magnum Pole powierzchni otworu wielkiego juvenile młode subadult dojrzałe adult dorosłe Area of the occipital triangle Pole powierzchni trójkąta potylicznego juvenile młode subadult dojrzałe adult dorosłe juvenile młode Cranial capacity Pojemność czaszki subadult dojrzałe Akrokranion-Prosthion 0.29 0.22 0.84 * 0.77 ** 0.81 * 0.79 ** Basion-Prosthion 0.29 0.18 0.80 0.78 ** 0.76 0.73 ** Euryon-Euryon 0.09 0.24 0.52 0.73 ** 0.74 0.86 ** Otion-Otion 0.15 0.09 0.80 0.58 ** 0.83 * 0.57 ** Zygion-Zygion 0.18 0.30 0.74 0.74 ** 0.75 0.79 ** Greatest breadth of the occipital condyles Szerokość kłykci potylicznych Cranial height Wysokość czaszki adult dorosłe 0.79 ** 0.49 ** 0.93 ** 0.92 ** 0.80 0.58 ** 0.42 0.42 0.87 * 0.54 ** 0.88 * 0.85 ** Correlations for age group Juvenile was not calculated due to small number of specimens. Z powodu małej liczby osobników w grupie juvenil młode nie obliczono wartości współczynników korelacji. Acta Sci. Pol.

The biometric characteristics of domestic cat skull in three stages... 77 DISCUSSION The analysis of findings referring to domestic cat (Felis s. catus) allowing for three age groups showed statistically significant increase of the traits characterising the length of skull in the time period to 11.5 month of life as well as after maturation, i.e. in the adult stage. This suggests that increase of the length and the breadth of viscerocranium take place not only during cat maturation but also after this period in adult animals. In the time period between age stages subadult and adult, the height and the breadth of skull still increases which approximates its shape to a sphere. This allows a statement that brain dimensions and the same neurocranium ones increase together with animal development. The statistical analysis of cranial indices which shows changes in the skull structure approximating its shape to a sphere furthered probably the selection towards brachycephalisation. Craniometric examinations carried out on Persian, Siamese and European shorthair cats showed that skulls of Persian cats were much broader than those of Siamese cats. The indices characterising the cranium breadth confirmed that the visceral part of skull was much narrower in cats with the head approximating a sphere. The indices showed also that the appearance of spherical skull shape was intensified by disproportions between the skull breadth and the narrowing visceral part. Short but high neurocranium makes the whole head look like a sphere. The reduction of neurocranium length is correlated with the increase of its breadth and height [Künzel et al. 2003]. The analysis of cranial indices shows that the ratio of the total cranium breadth to the total cranium length does not change in three age stages of domestic cat. However, the ratio of the cranial base length to that of neurocranium increases. The neurocranium itself start to broaden out in the time period between age stages subadult and adult in relation to its height. In this connection, the skull can be already slightly flattened in age stage adult. Also the ratio of the least breadth between the orbits to their height increases, which excludes the narrowing of visceral part. It was found in the study on domestic and wild cat skulls carried out on 58 animals from Thuringia that cranial index: the greatest cranium length [the total length] / the cranial capacity was the smallest in domestic cat, which is evidence of the reduction of trait proportions in wild cat. Higher value of the cranial capacity of wild cat is induced by the fact that the frontal part of skull is more arched [Küger et al. 2009]. CONCLUSION The skull of domestic cat changes dynamically together with age, which is expressed in respective proportions between its neural and visceral parts. The elongation of both viscerocranium and mandible in respective age stages may be the result of adaptation to predatory way of life. Zootechnica 9 (3) 2010

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