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Laminae in the teeth of the cape fur seal used for age determination
Life Sciences, Vol . 22, pp . 695-698 Priatad in the U.S .A.
Pergamon Press
LAIdINAE IN THE TEETH OF THE CAPE FUR SEAL USED FOR AGE DETERMINATION John R . Fletemeyer Department of Archaeology University of Cape Town Cape Town, South Africa (Received in final form January 9, 1978) SUMMARY A sample of 40 known age Cape fur seal, Arctocephalus pusillus , canine teeth were histologically and manually sectioned and examined for laminae to determine if these growth layers could be used for age determination in this species of seal . Results of this investigation indicate that two laminae (one opaque and one translucent) are deposited per annum and that these structures provide an accurate method for aging seals 2 years old or lesa~ agreement between age and laminae was also obtained for seals up to 8 years of age, but the small number (N - 3) of known-aged canines older than two years does not permit a definite conclusion as to the applicability of the method throughout the life span of the .Cape fur seal . Since the middle of the nineteenth century, information has been accumulating about the existence of a layering effect in the teeth of some mansoala (1,2,3) . It has been suggested that these layers (= laminae) represent an annual growth oyole . This suggestion has been subsequently documented by studies of whole and sectioned teeth representing a wide variety of pinniped species (4,5,6, 7,8,9,10) and land aiaa®als (11,12,13,14) . Tha Cape fur seal, Arctocephalue pusillus , native to the coastal and adjacent islands of South Africa, West Africa and Angola, has not bean previously subjected to this method of analysis . To study laminae in the canine teeth of this species, 40 known age teeth representing an equal number of males and females ware obtained from the South African Museum of Natural History . The age of these teeth was determined from the results of a long-term tagging program sponsored by the South African Department of Sea Fisheries involving tagging newly born "pups" at their rookeries and subsequently culling them over various predetermined periods of time . METHODS A number of unknown age canine teeth were sectioned eagittally by three methods to determine the best method to study the known age teeth for laminae. These methods includes (1) manual grindinq~ (2) hiatological sectioning ae out lined by Brain (16)~ and surface grinding with a Jones-Ship~man Grinder. The manual method produced the results which could moat easily be used for analyzing the preeenoe of laminae in the canine teeth . This method involved reducing the tooth specimen to a thickness of 500u by wet grinding on 360-grit carbide paper . Further diminution was accomplished by using pumice and whiting which was sprinkled wet on a twelve-inch diameter section of leaded plate glass . The sections ware ground in an elliptical, clockwise motion at the speed of 200 RPM until the desired thickness of 125u was reached. The section was peridically checked under low magnification to insure uniform grinding . The completed specimens were dry mounted between two microscope slides and examined under a binoc695
696
Seal Teeth Laminae in Age Determination
Vol . 22, No . 8, 1978
ulcer microscope . Sometimes a transmitted light source and a green filter wns used to increse the contrast of the tooth section. RESULTS Laminae could be defined in the dentin and cementum of all the canine tooth sections, but in the latter the laminae were easier to count (Fig . 1) . When comparing the known age of the canine section, it was found that two laminae were deposited per annum two in the one year old sections (N ~12), four in the two year old sections (N a25), eight in the four year_ .old sections (N -1), twelve in the six year old sections (N ~1) and 16 in the eight year old sections (N ~1) . In the three sections representing seals older than two years, the laminae become more difficult to define because the layers tend to coalesce : After exeminntion of the one yeas old sections, it was determined that two laminae (one translucent and one opaque) represent a year's deposition cycle . Tha translucent lamina is deposited in the South African autumn-winter months (July-December) while the opaque lamina is deposited in the spring-st,+++~+o,- months (JanuaryJune) . When attempting to find any sexual differences in the depoaitional sequence, none could be determined, suggesting that these results apply uniformly among both sexes of the Cape fur seal . FIG. 1
An example of laminae in the cementum of a six year old Capa fur seal used for age determination DISCUSSION The results of thin investigation suggests that laminae found in the canine teeth of the Cape fur seal can be used to determine the age of juvenile seals and probably the age of young adults . Since this investigation was handicapped by the lack of known age specimens older than eight years of age and since Cape fur seals may live to exceed twenty years of age, it is not known it this method can apply In some investigations involving very old seals representing difto old seals. ferent epecieq, there is some indication that the number of laminae and age does not always exactly agree . Mansfield and Fiahsr (19) were able to count 18-ZO idyers (= 36-40 laminae) in a canine tooth of a 19-year old harbor seal, Phocidae vitulina , while Hewer (20) counted 25 layers (~ 50 laminae) in a 26-year old gray seal, Halicheorous grypua caw. Additional canine Bections of known.
Vol. 22, No . 8, 1978
Seal Teeth Laminae in Age Determination
697
age Cape fur seals representing the entire life span of this species are required before any inconeiatencies .can be determined . Othsr investigations aThich have focused on rhis subject of age determination in the teeth of aaaaoals found that an opaque lamina ie deposited in the spring or spring-summer months (22,23,24,25,26,27) . Different findings sere reported by Mundy & Fuller (28) for the grizzly bear, Ursw horribilis . In this animal they found that a translucent lamina is formed in the dental structure near the end of the summer . The findings of this investigation agrees with the majority of findings . Dist has been indicated as the ultimate factor responsible for this annual layering effect in the cementum and dentin of same maam~nls (29) . Since the Cape fur seal is nonmigratory and has aocess to a relatively constant supply of food, this investigation suggests that more subtle influences my be involved other than gross diet . The differential intake of certain eaaential Vitamins (30) or a significant change in hormone activity during breeding and mating eeason (31) might be responsible for this layering effect in the teeth of the Cape Fur seal as well as in many other species of land and marine mammls . ACKN09PLEDGMEDiTS This work was supported by a Graduate Research Grant from the University of Cape Town . I wish to thank N. van der Merwe and J . Deacon for their valuable assistance in this project. RF'F174AN(~S
1.
R. OWEN, Odontography or a Treatise of the Comparative Anatomy of the Teeth in the Vertebrate Animals, p . 180, London (1845) . 2 . C . S . TOMES, A Manual of Dental Anatomy, P . 590, J . A . Church111, (1898) . 3 . H . HOSCiIIdA, Temminchia 8 151-274 (1938) . 4 . V . 8 . SCHEFFER, Science 112 309-311 (1950) . 5 . H . D . FISFIBR and B . A. MAC103NZIE, J. Wildl. Mqt . 18 535-537 (1954) . 6 . R . 8 . CHIASSON, J . Maam~al. 38 310-319 (1957) . 7 . A . W . MANSFIELD and H. D . FISHER, Nature 18 92-93 (1960) . 8 . H . R. HE9~R, Nature 18 187 (1960) . 9 . K. KENYON and C. H. FISCUS, J. Maarml . 44 280-281 (1963) . 10 . E . H. McSWAN, Can. J . Zool . 41 77-104 (1963) . 11 . F . C . VAN NOSTRAI~ and A . STEPHENSON, J. Wildl . Mgt. 28 430-434 (1964) . 12 K. R. MUNDY and W. S . FULLER, J . Wildl. Mgt . 28 836-866 (1964) . 13 . 8 . MITCHEL, Nature 198 350-351 (1963) . 14 . H . JENSEN and L . 8 . NIELSON, Dan. Rev. Gem. Bio . 5 1-15 (1968) . 15 .~ R. W. RAND, Diyis . Sea Fish . Invest . Rep. 34 (1959) . 16 . E . 8 . BRAIN, The Preparation of Decalcified Sections , C. T. Thoaae, Springfield (1966) . 17 . H . MITCHEL, Nature 198 350-351 (1963) . 18 . V . W . LOWS, J. Zool . Soc . Load . 15 2 137=153 (1967) . 19 . A . W . MANSFIELD and H. D . FISHER, Nature 18 93-94 (1958) . 20 . H. D. FISHER and B . A. MAC1Q~iZIE, J . Wildl . Mgt. 18 535-537 (1954) . 21 . H . R. HEWER, Pros . Zool . Soc . Load . 14 2 593-624 (1964) . 22 . C . H . FiSCUS, J . Mammal . 42 218-223 (1961) . 23~ A. W. MANSFIELD, Flk. Isl . Dept . Surv. .Sci . Rep. 18 (1958) . 24 . B. MITCHBL, Nature 198 350-351 (1963) . 25 . D . E . SERGEANT and D. H. PINLOZT, J . Wildl. Mgt . 23 315-321 (1959) . 26 . P . H. REST, Div. Sea Fish . Invest . Rep . 79 (1970) . 27 . R. CARRICK and 3. A . INGRAM, C. S. I. R . O . Wildl. Rap. 7 102-118 (1962) . 28 . K. R. MUNDY and W. A. FULLER, J. Wildl . Mgt. 28 836-866 (1964) . 29 . B. MITCHEL, Nature 198 350-351 (1963) . 30 . E. H. MaEFD1N, Can. J. Zool . 41 77-104 (1963) . 31 . R. CARRICK and 3 . E . INGRAM, C. S. I . R. O . Wildl. Rep. 7 102-118 (1962) .
Pergamon Press
LAIdINAE IN THE TEETH OF THE CAPE FUR SEAL USED FOR AGE DETERMINATION John R . Fletemeyer Department of Archaeology University of Cape Town Cape Town, South Africa (Received in final form January 9, 1978) SUMMARY A sample of 40 known age Cape fur seal, Arctocephalus pusillus , canine teeth were histologically and manually sectioned and examined for laminae to determine if these growth layers could be used for age determination in this species of seal . Results of this investigation indicate that two laminae (one opaque and one translucent) are deposited per annum and that these structures provide an accurate method for aging seals 2 years old or lesa~ agreement between age and laminae was also obtained for seals up to 8 years of age, but the small number (N - 3) of known-aged canines older than two years does not permit a definite conclusion as to the applicability of the method throughout the life span of the .Cape fur seal . Since the middle of the nineteenth century, information has been accumulating about the existence of a layering effect in the teeth of some mansoala (1,2,3) . It has been suggested that these layers (= laminae) represent an annual growth oyole . This suggestion has been subsequently documented by studies of whole and sectioned teeth representing a wide variety of pinniped species (4,5,6, 7,8,9,10) and land aiaa®als (11,12,13,14) . Tha Cape fur seal, Arctocephalue pusillus , native to the coastal and adjacent islands of South Africa, West Africa and Angola, has not bean previously subjected to this method of analysis . To study laminae in the canine teeth of this species, 40 known age teeth representing an equal number of males and females ware obtained from the South African Museum of Natural History . The age of these teeth was determined from the results of a long-term tagging program sponsored by the South African Department of Sea Fisheries involving tagging newly born "pups" at their rookeries and subsequently culling them over various predetermined periods of time . METHODS A number of unknown age canine teeth were sectioned eagittally by three methods to determine the best method to study the known age teeth for laminae. These methods includes (1) manual grindinq~ (2) hiatological sectioning ae out lined by Brain (16)~ and surface grinding with a Jones-Ship~man Grinder. The manual method produced the results which could moat easily be used for analyzing the preeenoe of laminae in the canine teeth . This method involved reducing the tooth specimen to a thickness of 500u by wet grinding on 360-grit carbide paper . Further diminution was accomplished by using pumice and whiting which was sprinkled wet on a twelve-inch diameter section of leaded plate glass . The sections ware ground in an elliptical, clockwise motion at the speed of 200 RPM until the desired thickness of 125u was reached. The section was peridically checked under low magnification to insure uniform grinding . The completed specimens were dry mounted between two microscope slides and examined under a binoc695
696
Seal Teeth Laminae in Age Determination
Vol . 22, No . 8, 1978
ulcer microscope . Sometimes a transmitted light source and a green filter wns used to increse the contrast of the tooth section. RESULTS Laminae could be defined in the dentin and cementum of all the canine tooth sections, but in the latter the laminae were easier to count (Fig . 1) . When comparing the known age of the canine section, it was found that two laminae were deposited per annum two in the one year old sections (N ~12), four in the two year old sections (N a25), eight in the four year_ .old sections (N -1), twelve in the six year old sections (N ~1) and 16 in the eight year old sections (N ~1) . In the three sections representing seals older than two years, the laminae become more difficult to define because the layers tend to coalesce : After exeminntion of the one yeas old sections, it was determined that two laminae (one translucent and one opaque) represent a year's deposition cycle . Tha translucent lamina is deposited in the South African autumn-winter months (July-December) while the opaque lamina is deposited in the spring-st,+++~+o,- months (JanuaryJune) . When attempting to find any sexual differences in the depoaitional sequence, none could be determined, suggesting that these results apply uniformly among both sexes of the Cape fur seal . FIG. 1
An example of laminae in the cementum of a six year old Capa fur seal used for age determination DISCUSSION The results of thin investigation suggests that laminae found in the canine teeth of the Cape fur seal can be used to determine the age of juvenile seals and probably the age of young adults . Since this investigation was handicapped by the lack of known age specimens older than eight years of age and since Cape fur seals may live to exceed twenty years of age, it is not known it this method can apply In some investigations involving very old seals representing difto old seals. ferent epecieq, there is some indication that the number of laminae and age does not always exactly agree . Mansfield and Fiahsr (19) were able to count 18-ZO idyers (= 36-40 laminae) in a canine tooth of a 19-year old harbor seal, Phocidae vitulina , while Hewer (20) counted 25 layers (~ 50 laminae) in a 26-year old gray seal, Halicheorous grypua caw. Additional canine Bections of known.
Vol. 22, No . 8, 1978
Seal Teeth Laminae in Age Determination
697
age Cape fur seals representing the entire life span of this species are required before any inconeiatencies .can be determined . Othsr investigations aThich have focused on rhis subject of age determination in the teeth of aaaaoals found that an opaque lamina ie deposited in the spring or spring-summer months (22,23,24,25,26,27) . Different findings sere reported by Mundy & Fuller (28) for the grizzly bear, Ursw horribilis . In this animal they found that a translucent lamina is formed in the dental structure near the end of the summer . The findings of this investigation agrees with the majority of findings . Dist has been indicated as the ultimate factor responsible for this annual layering effect in the cementum and dentin of same maam~nls (29) . Since the Cape fur seal is nonmigratory and has aocess to a relatively constant supply of food, this investigation suggests that more subtle influences my be involved other than gross diet . The differential intake of certain eaaential Vitamins (30) or a significant change in hormone activity during breeding and mating eeason (31) might be responsible for this layering effect in the teeth of the Cape Fur seal as well as in many other species of land and marine mammls . ACKN09PLEDGMEDiTS This work was supported by a Graduate Research Grant from the University of Cape Town . I wish to thank N. van der Merwe and J . Deacon for their valuable assistance in this project. RF'F174AN(~S
1.
R. OWEN, Odontography or a Treatise of the Comparative Anatomy of the Teeth in the Vertebrate Animals, p . 180, London (1845) . 2 . C . S . TOMES, A Manual of Dental Anatomy, P . 590, J . A . Church111, (1898) . 3 . H . HOSCiIIdA, Temminchia 8 151-274 (1938) . 4 . V . 8 . SCHEFFER, Science 112 309-311 (1950) . 5 . H . D . FISFIBR and B . A. MAC103NZIE, J. Wildl. Mqt . 18 535-537 (1954) . 6 . R . 8 . CHIASSON, J . Maam~al. 38 310-319 (1957) . 7 . A . W . MANSFIELD and H. D . FISHER, Nature 18 92-93 (1960) . 8 . H . R. HE9~R, Nature 18 187 (1960) . 9 . K. KENYON and C. H. FISCUS, J. Maarml . 44 280-281 (1963) . 10 . E . H. McSWAN, Can. J . Zool . 41 77-104 (1963) . 11 . F . C . VAN NOSTRAI~ and A . STEPHENSON, J. Wildl . Mgt. 28 430-434 (1964) . 12 K. R. MUNDY and W. S . FULLER, J . Wildl. Mgt . 28 836-866 (1964) . 13 . 8 . MITCHEL, Nature 198 350-351 (1963) . 14 . H . JENSEN and L . 8 . NIELSON, Dan. Rev. Gem. Bio . 5 1-15 (1968) . 15 .~ R. W. RAND, Diyis . Sea Fish . Invest . Rep. 34 (1959) . 16 . E . 8 . BRAIN, The Preparation of Decalcified Sections , C. T. Thoaae, Springfield (1966) . 17 . H . MITCHEL, Nature 198 350-351 (1963) . 18 . V . W . LOWS, J. Zool . Soc . Load . 15 2 137=153 (1967) . 19 . A . W . MANSFIELD and H. D . FISHER, Nature 18 93-94 (1958) . 20 . H. D. FISHER and B . A. MAC1Q~iZIE, J . Wildl . Mgt. 18 535-537 (1954) . 21 . H . R. HEWER, Pros . Zool . Soc . Load . 14 2 593-624 (1964) . 22 . C . H . FiSCUS, J . Mammal . 42 218-223 (1961) . 23~ A. W. MANSFIELD, Flk. Isl . Dept . Surv. .Sci . Rep. 18 (1958) . 24 . B. MITCHBL, Nature 198 350-351 (1963) . 25 . D . E . SERGEANT and D. H. PINLOZT, J . Wildl. Mgt . 23 315-321 (1959) . 26 . P . H. REST, Div. Sea Fish . Invest . Rep . 79 (1970) . 27 . R. CARRICK and 3. A . INGRAM, C. S. I. R . O . Wildl. Rap. 7 102-118 (1962) . 28 . K. R. MUNDY and W. A. FULLER, J. Wildl . Mgt. 28 836-866 (1964) . 29 . B. MITCHEL, Nature 198 350-351 (1963) . 30 . E. H. MaEFD1N, Can. J. Zool . 41 77-104 (1963) . 31 . R. CARRICK and 3 . E . INGRAM, C. S. I . R. O . Wildl. Rep. 7 102-118 (1962) .