Scale development in fish: a review, with description of sonic hedgehog (shh) expression in the zebrafish (Danio rerio).

Abstract

In the first part of this paper we review current knowledge regarding fish scales, focusing on elasmoid scales, the only type found in two model species, the zebrafish and the medaka. After reviewing the structure of scales and their evolutionary origin, we describe the formation of the squamation pattern. The regularity of this process suggests a pre-patterning of the skin before scale initiation. We then summarise the dynamics of scale development on the basis of morphological observations. In the absence of molecular data, these observations support the existence of genetic cascades involved in the control of scale development. In the second part of this paper, we illustrate the potential that scale development offers as a model to study organogenesis mediated by epithelial-mesenchymal interactions. Using the zebrafish (Danio rerio), we have combined alizarin red staining, light and transmission electron microscopy and in situ hybridisation using an anti-sense RNA probe for the sonic hedgehog (

Postembryonic staging of wild‐type goldfish, with brief reference to skeletal systems

“…Comparative studies of ontogenetic process require not only embryonic, but also postembryonic staging tables, as several important morphogenetic processes which form characteristic features of each species (for example, internal and external skeletal structures and scale patterns) are known to proceed during postembryonic stages (Arratia et al, 1990, 1991; Cubbage and Mabee, 1996; Schilling and Kimmel, 1997; Van der Heyden and Huyssune, 2000; Van der Heyden et al, 2000; Witten et al, 2001; Yelick and Schilling, 2002; Mabee et al, 2002; Bird and Mabee, 2003; Sire and Huysseune, 2003; Webb and Shirey, 2003; Elizondo et al, 2005; Sire and Akimenko, 2004; Thorsen and Hale, 2005; Patricia et al, 2007; Patterson et al, 2008; Parichy et al, 2009; Kimmel et al, 2010; Budi et al, 2011; Bensimon‐Brito et al, 2012). However, at present there is no widely available postembryonic developmental staging table for goldfish, in practice.…”

Epidermal transient down‐regulation of retinol‐binding protein 4 and mirror expression of apolipoprotein Eb and estrogen receptor 2a during zebrafish fin and scale development

“…apoeb transcripts were subsequently restricted to the posterior margin epidermis of the papilla (Monnot et al, 1999), a pattern also observed with esr2a (Fig. 4G,M) and sonic hedgehog (shh; Sire and Akimenko, 2004). Ultrastructural studies suggested that epidermal-dermal interactions continued to occur in the posterior region of the formed scale (Sire et al, 1997a).…”

“…In zebrafish, the first scales appear on the lateral and posterior part of the fish at the midregion of the caudal fin and squamation then spread forward, downward, and laterally (Waterman, 1970;Sire et al, 1997a;Sire and Akimenko, 2004). Starting from a homogeneous rbp4 expressed epidermal cover (Fig.…”

“…Consequently, the transient down-regulation of rbp4 in epidermal cells occurs according to a restrictive mode of molecular expression and does not appear to play a role in the early specification or positioning of the placodes, but rather to be a downstream responsive early element in the inducible wave of epidermal placode formation. Morphological studies have revealed that scale formation takes place in the dermis after condensation below the epidermal basement membrane of a scale dermal papilla from invading fibroblast-like cells, by around 1 month postfertilization (Le Guellec et al, 2004;Sire and Akimenko, 2004). Each scale-forming cell population in a scale papilla gives rise to a single scale.…”

“…This metamorphosis entails changes in a variety of organ systems, including resorption of the larval fin fold and development of adult unpaired fins, development of scales in the integument, and formation of an adult pigment pattern (Brown, 1997;Sire et al, 1997a). Numerous studies have illustrated the morphogenesis of scales in teleost fish, including zebrafish (Waterman, 1970;Sire et al, 1997a,b;Sire and Akimenko, 2004).…”