Three Unique Experimental Fish Stories: Poecilia (the Past), Xiphophorus (the Present), and Medaka (the Future)

Abstract

These three stories exemplify the uniqueness of fish models in their abilities to answer important biological questions. The first one identifies the major UV-induced damage (pyrimidine dimers) that is responsible for tumor induction. Thyroid cells from isogenic fish ( Poecilia formosa) were exposed to UV in vitro, then either exposed or not to photoreactivating light that monomerizes dimers, and the cells were injected into isogenic recipients. In the absence of photoreactivating light, the recipients developed tumors; in its presence, there were very few tumors. The second story describes our use of backcross hybrids of Xiphophorus as a model for melanoma induction by several UV and visible wavelengths. All the wavelengths were effective. (Squamous cell carcinomas in mice are induced preferentially by wavelengths <320 nm.) The data strongly suggest that light absorbed by the black pigment melanin damages DNA. The third story is designed to determine the mutagenic effects on sperm of the high atomic number, high-energy (HZE) nuclei present in cosmic rays by measuring mutations in progeny of exposed male medaka.

lnterspecific Variation in UV Defense Mechanisms Among Temperate Freshwater Fishes

“…Although PER has been found in many fish species (11–14, 31–34), we failed to detect evidence of PER in northern pike, brook trout and rainbow trout larvae. Because we only examined a single early life stage, we cannot rule out the possibility that other life stages of these species may be capable of PER, as has been demonstrated in other species (35).…”

“…However, the extent to which this observation holds for temperate freshwater fishes is not known because it is based on relatively few species and because those that have been studied are primarily tropical (e.g. Poecilia Formosa and Carassius auratus ) (11, 12) or marine ( eg. Engraulis mordax and Gadus morhua ) (13, 14).…”

Use of the Japanese Medaka (Oryzias latipes) and Guppy (Poecilia reticulata) in Carcinogenesis Testing Under National Toxicology Program Protocols

“…Each model species has attributes and disadvantages. Several other whole fish carcinogenesis models are available including the well-developed rainbow trout model (Williams, this volume), the platyfish/swordtail hybrid model (13), medaka and guppies (7).…”

Genomics and mapping of Teleostei (bony fish)

“…Medaka is also being using in tumour genetics (Rotchell et al, 2001), but has been promoted more specifically for the study of germ cell mutagenesis and genomic instability (Shima and Shimada, 2001). One example of the latter is its use to estimate germ cell mutations in Astronauts exposed to high atomic number, high-energy (HZE) nuclei present in cosmic rays (Setlow and Woodhead, 2001). In addition to these specific medical uses, fish are also valuable tools for deciphering essential biological processes (Bolis et al, 2001;Clark et al, 2002;Grunwald and Eisen, 2002;Korpi et al, 2002).…”