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Description
ABSTRACT: This study compared the concentrations of major and trace elements in the enamel of incisors from moose (Alces alces andersoni) in Cape Breton Highlands, where the incidence of incisor tooth breakage was believed to be unusually high, and moose in southwest Nova Scotia (A. a. americana) where there was no evidence of breakage. Our goal was to determine which elements, if any, might be related to the incisor breakage in moose from Cape Breton Highlands. There was a positive relationship between age and frequency of incisor breakage, and most moose had a broken 12 incisor by 4 years of age in the Cape Breton Highlands. We analyzed I2 incisors for 51 trace elements with Inductively Coupled Plasma-Mass Spectrometry. Concentrations of 8 elements, including barium, beryllium, cadmium, cobalt, lead, tin, strontium, and yttrium, were lower (P < 0.05) in incisors from Cape Breton Highlands; gallium had a higher concentration. Reduced intake of barium, beryllium, and strontium is linked to depressed growth and reduced calcification of bones and teeth.
Key words: Alees alces, barium, beryllium, cadmium, cobalt, gallium, incisor, Inductively Coupled Plasma-Mass Spectrometry, lead, moose, Nova Scotia, strontium, teeth, trace elements, yttrium
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The role that major and trace elements play in the metabolism of organisms has been the focus of intense, well-documented research (Underwood 1977, Prasad 1993, Underwood and Suttle 1999, Bogden and Klevay 2000). Disease may result from either a toxic or a deficient dietary intake of elements, and is often a reflection of geo-environmental factors (Maisironi 2000). Teeth are good indicators of the abundance of many elements (Brown et al. 2004, Kang et al. 2004, Dolphin et al. 2005) due to the crystal structure of enamel (Sharaway and Yeager 1991, Simmelink 1994). Major and trace elements are incorporated within the hydroxyapatite crystal framework during the mineralization period (Sharaway and Yeager 1991, Simmelink 1994) and, due to the semi-permeable nature of hydroxyapatite, small ions and molecules are able to pass through the enamel framework preceding eruption (Cutress 1983). Therefore, to an extent, teeth remain in chemical equilibrium with the oral environment (Zimmerman 1976, Driessens 1982).
Strength and solubility of enamel is influenced by the concentration of major and trace elements (Zimmerman 1976), which is affected by various factors such as normal wear, food composition, and regional geochemistry (Cutress 1983). Therefore teeth are an excellent bio-indicator of local environmental conditions (Lee et al. 1999, Lochner et al. 1999, Gdula-Argasinska et al. 2004). This is especially true for non-migratory ruminant herbivores such as moose (Alces alces) that obtain their entire dietary mineral intake from distinct regional geological localities (Cederlund and Okarma 1988, Lepitch and Gilbert 1989, Hundertmark 1998).
Observations of physical and behavioral anomalies suggest that the moose population is stressed in the Cape Breton Highlands (A. a. andersoni) in Nova Scotia, Canada. Wildlife authorities have observed osteophagia (Roger and Nette 2002), an increased incidence of bark stripping, and tooth breakage (Fig. 1) in Cape Breton Highlands moose where densities are high and heavy browsing of preferred vegetation is evident. Distinct browse lines 2-3 meters off the ground extend several kilometers through the forest (Basquill and Thompson 1997).
The only previously reported case of incisor breakage was in a moose (A. a. gigas) population on the Seward Peninsula, Alaska. Smith (1992) documented 'incisiform breakage' over a 2-year period (1988-1990), which closely resembles the breakage observed in Cape Breton Highlands moose. The breakage observed in the Cape Breton Highlands is markedly different from the tooth wear frequently reported in other ungulate species (Hewison et al. 1999, Loe et al. 2003). It also differs from the incisiform wear reported in Kenai Peninsula moose by Peterson et al. (1982), and the unusual wear described by Young and Many (1986) in a Manitoban moose population. The distinctive incisor breakage begins as a brown stained crack on the tooth surface (Fig. 1) that is a precursor to breakage. Where breakage has occurred, the tooth is subsequently rounded down and stained brown. This rounded, staining characteristic is important because it indicates that breakage occurred during the lifetime and not at, or after, death.
The purpose of this study was to determine whether concentrations of... |
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