Scale formation in selected fundulid and cyprinodontid fishes

Abstract

Patterns of scale formation (onset, points of origin, completion, and spatial pattern) were examined for six species of killifishes in two families (Cyprinodontidae: Cyprinodon variegatus, and Fundulidae: Fundulus confluentus, F. heteroclitus, F. luciae, F. majalis, and Lucania parva) to determine if the patterns are another useful indicator for the transition from the larval to juvenile periods. In some species, the patterns were very similar, with scale formation originating on/near the caudal peduncle, then the dorsal surface of the head (in fundulids only), and later on the lateral surfaces of the head, and on the ventral surface of the trunk at the level of the pectoral fin. The timing of scale formation, relative to fish size, was later than or overlapped with other morphological characters (e.g., fin ray formation, juvenile/adult body shape) often used to mark the larval/juvenile transition. The onset of scale formation, across all species, occurred between 8 and 13 mm TL. Completion of scale formation occurred between 18 and 23 mm TL. At completion, scales covered 86-99% of the trunk and head. Completion of scale formation in these fishes is one of the last external morphological changes to occur during the larval to juvenile transition. For these species, and other flatfishes we have examined in detail, it appears that scale formation may be useful in helping to define the end of the larval period and the beginning of the juvenile period. Further studies, of divergent groups of teleosts, are necessary to determine if this length-based approach has broad validity.

Drastic shift in the number of lateral line scales in the common roachRutilus rutilusas a result of heterochronies: experimental data

“…In fish, they play an important role in protection and enhancement of their locomotion (Burdak, 1979). During the last two decades, extensive studies have been devoted to various aspects of scale development, including the development of scales types and scale‐like elements, squamation pattern, histological diversity, epidermal‐dermal interactions, origin and evolution of postcranial dermal skeleton of osteichthyan fishes (Park and Lee, 1988; Sire and Arnulf, 1990; Sire et al., 1997, 2009; Sire and Akimenko, 2004; Able et al., 2008).…”

Evaluation of scale development and its regeneration potency in the desert killifish under laboratory conditions

“…The microstructure characterization of regenerated scales of common carp ( Cyprinus carpio ) was recently analyzed by Ghods et al (2020) in laboratory conditions. Nevertheless, little is known about the scale regeneration processes in killifishes (Able et al, 2009). This study aimed to evaluate the scale development pattern and the scale regeneration potency in a desert killifish Aphaniops hormuzensis (family Aphaniidae) in laboratory conditions to provide basic information on these processes in killifishes.…”

Fantastically plastic: fish larvae equipped for a new world

“…In mammals, patterns of DNA methylation are established early in life, with active or passive demethylation producing pluripotent cells where all genes are potentially transcriptionally active (Able et al . ; Burdge & Lillycrop ). As in teleost development, mammalian pluripotent embryonic cells differentiate into mature tissues through changes in gene promoters and a series of de novo methylation and demethylation influencing transcription activity.…”

“…The full details of how structure is inherited from stem cells are not yet clear, but it is clear that as the original egg cell differentiates into cells of different destinies and functions, these cells respond differently to the biological and physical environment and intercellular signalling. In mammals, patterns of DNA methylation are established early in life, with active or passive demethylation producing pluripotent cells where all genes are potentially transcriptionally active (Able et al 2009;Burdge & Lillycrop 2010). As in teleost development, mammalian pluripotent embryonic cells differentiate into mature tissues through changes in gene promoters and a series of de novo methylation and demethylation influencing transcription activity.…”