The pattern of the lower jaw dentition in farmed Atlantic salmon (Salmo salar): a tool to study mechanisms of tooth replacement?

Abstract

We investigated the tooth pattern on the lower jaw of adult farmed Atlantic salmon (Salmo salar L.) to elucidate whether this pattern is more regular, with less variations, than that observed in wild Atlantic salmon studied previously. A highly regular and predictable tooth pattern, in combination with the availability of Atlantic salmon in near unlimited numbers, should provide us with an ideal model to test the hypothesis whether field or local control regulates the process of tooth replacement. In 30 animals a tooth was damaged, or partially or nearly completely extracted. The animals were sacrificed after a recovery period varying between 1 and 12 weeks. X-rays were taken prior to and at various time points after manipulation. After sacrifice, dissected jaws were cleared and stained. Surprisingly, farmed Atlantic salmon do not display a regular pattern of tooth replacement and rather resemble the marine life stage of wild Atlantic salmon. While the irregularity of the tooth replacement pattern speaks against general (field) regulation of the replacement process, it impedes its use as a tool with which the nature of this control mechanism can be studied experimentally. Our observations nevertheless provide the first preliminary data on tooth growth and turnover in Atlantic salmon

Tooth Removal in the Leopard Gecko and the de novo Formation of Replacement Teeth

“…We found that the functional tooth was retained in the mouth for longer than expected and was not replaced until a replacement tooth was present to resorb it. The importance of tooth resorption in maintaining tooth cycle timing has also been shown in studies where the functional tooth was broken, but not removed, in fish (Huysseune et al, 2012) and iguanas (Brink et al, 2020). The timing of tooth replacement in iguanas was not affected by breakage of the tooth crown, since the base still needed to be resorbed before being shed.…”

“…Many studies have investigated potential mechanisms for the establishment of this alternating wave replacement pattern in polyphyodont animals. In fish, there is strong evidence for signals that originate with an initiator tooth at the front of the jaw and pattern the tooth row or rows ( Huysseune et al, 2012 ; Gibert et al, 2019 ; Sadier et al, 2020 ). This mechanism has also been suggested for reptiles, however, it has not been tested ( Edmund, 1969 ).…”

Continuous tooth replacement: what can teleost fish teach us?

“…A valid test for local control would be the capacity at a specific tooth locus to accelerate the development of the replacement tooth after extraction of the predecessor. Such an experiment requires teeth that are large enough and easily accessible (oral, rather than pharyngeal teeth) and a highly predictable pattern of replacement in case the extraction site cannot be labelled appropriately (Huysseune et al ., 2012). Detailed analyses of teleost dentitions have led to the suggestion that general control sets up the initial pattern (consistent with a field model, cf .…”

Interdisciplinary approaches in fish skeletal biology

“…Common carp ( Cyprinus carpio ), Atlantic salmon ( Salmo salar ) and gilthead seabream ( Sparus aurat a) are also used for fish farming, available for experiments and often a good reason to start a collaboration between developmental biologists and aquaculture experts since in many ways their interests can merge. From experiments with fish we learn about the regenerative capacities of dermal skeletal elements (teeth, scales and fin rays) (Huysseune et al., 2012; Metz et al., 2012; Vandenplas et al., 2012; de Vrieze et al., 2012) and about the mechanisms of skeletal mineralisation (Conceição et al., 2012; Fazenda et al., 2012; Viegas et al., 2012). Pathological low mineralisation and ectopic mineralisation exemplify that skeletal development is plastic and much influenced by epigenetic factors (Danos and Staab, 2010).…”