Body size determines the number of scales in cyprinid fishes as inferred from hormonal manipulation of developmental rate

Abstract

Summary In experiment with hormonal manipulation of developmental rate (alteration of thyroid status) of two cyprinid species, Abramis brama and Rutilus rutilus, we found that number of scales strongly correlates with body size at the moment of first scale appearance. If squamation development starts earlier and at a shorter body length, it results in reduction of scale numbers. If squamation development starts later and at a larger body length, the number of scales is increased. Calculated distances between scales at the moment of their appearance are the same in the different experimental groups despite of acceleration or retardation of developmental rate and a corresponding change in the number of scales (decreasing and increasing). It suggests that size of body at the moment of scale initiation determines the number of scales. Induced heterochrony in initiation of squamation is one of the mechanisms, which is evidently responsible for intraspecies variability in scale numbers and might be considered a relevant reason for differences between close‐related species in case of evolutionary fixed heterochronies of scale initiation. Another plausible path for diversity in scale number is a change in distance between forming scales that seems to be more appropriate for species represented phylogenetically more distant lineages.

Poly- and oligomerization of scales in the blue bream Ballerus ballerus (Cyprinidae) as a consequence of thyroid status regulation

“…Together with already known dependence of scale numbers on dosage of treatment (Levin, ; Levin et al., ), this study shows that the time of beginning and duration of treatment also affect number of scales. Also thyroid regulation of development is thought to be a perspective approach to mark periods of determination of the number of serial elements including period of skin patterning, which precedes scale initiation (Sire and Akimenko, ).…”

Supernumerary teeth in the pharyngeal dentition of slow-developing zebrafish (Danio rerio , Hamilton, 1822)

“…In particular, retardation of the caudal fin endoskeleton was prominent, as revealed by comparison to the developmental table provided by Bensimon-Brito, Cancela, Huysseune, and Witten (2012) (data not shown). These data are consistent with earlier published reports regarding the effects of thiourea treatment in cyprinids, and its qualification as heterochrony (Bolotovskiy & Levin, 2011;Levin, Bolotovskiy, & Levina, 2012;Shkil et al, 2010).…”

Effects of thyroid hormones on vertebral numbers in two cyprinid fish species:Rutilus rutilus(Linnaeus, 1758) andAbramis brama(Linnaeus, 1758)

“…Although the somite numbers significantly foreshadow vertebral numbers (Gorodilov, ; Richardson, Allen, Wright, Raynaud, & Hanken, ), it is still possible that other factors can determine the definitive number of vertebrae, especially in caudal region (Yamahira, Nishida, Arakawa, & Iwaisaki, ). Our earlier study on the effect of TH‐manipulation on the scale numbers in the lateral line in two cyprinid species revealed a highly positive correlation between the number of serially‐repeated elements and fish body size (Levin, Bolotovskiy, & Levina, ).…”