Kryptolebias marmoratus(Poey, 1880): a potential model species for molecular carcinogenesis and ecotoxicogenomics

Abstract

Kryptolebias marmoratus (Rivulus marmoratus till 2004, order Cyprinodontoformes; family Rivulidae) is the only known self-fertilizing hermaphrodite vertebrate. Because of this uniqueness, there has been great interest in its biology, physiology, developmental biology and genomics along with other basic and applied areas of environmental genomics and molecular carcinogenesis. In laboratory studies, K. marmoratus has shown susceptibility to a number of xenobiotics including carcinogens. Toxicologists are interested in the mechanisms of action of environmental chemicals of contemporary interest such as endocrine disruptors and may consider this as a suitable fish model for the study of chemically induced carcinogenesis. Single short-term exposure to model chemical carcinogens is sufficient to induce tumourigenesis in K. marmoratus in a relatively short time span. In recent years, considerable data have been generated about gene sequences of K. marmoratus. Laboratory maintenance of K. marmoratus is relatively easy. Gene bank data are readily available, though not as extensive as for zebrafish Danio rerio or Japanese madaka Oryzias latipes. The expressed sequence tag (EST) data, differential display real-time reverse-transcriptase polymerase chain reaction and Gene Sequencer 20Ô sequencing data have recently been helpful in understanding the genomics and proteomics of this species. Recently, sequences of the oncogene, ras, and tumour suppressor gene, p53, have been reported in K. marmoratus. The expression of these important genes that play significant roles not only in carcinogenesis but also in other signal transduction pathways was observed to be modulated by environmental endocrine-disrupting chemicals. Having a large sequence database (cDNA sequences and ESTs), it is expected that the use of a microarray in the near future will open new vistas for this fish with applications in cancer research, aquatic toxicology, endocrinology and genomics. This review discusses potential uses of K. marmoratus in new biotechnological approaches of aquatic toxicology.

Embryonic development of the self‐fertilizing mangrove killifish Kryptolebias marmoratus

“…marmoratus represents a very unique genetic model system due to its hermaphroditic nature, established clonal lines, and its androdioecious reproductive system which allows mixing between strains by outcrossing using primary or secondary gonochoristic males. Laboratory use of K. marmoratus has already been suggested in a variety of fields such as carcinogenicity testing (Koenig and Chasar, 1984) and aquatic toxicology studies (Lee et al, 2008). We further support that K. marmoratus, with its easily obtainable and handled embryos, can be used in a variety of embryological research fields in the same light as other species such as the zebrafish or the medaka.…”

“…Adults grow up to 75 mm and maturity is achieved 3 to 4 months after hatching (Kanamori et al, 2006;Lee et al, 2008). Late in their life cycle (3-4 years), approximately 60% of the hermaphroditic individuals transform into secondary males (Lee et al, 2008).…”

“…Late in their life cycle (3-4 years), approximately 60% of the hermaphroditic individuals transform into secondary males (Lee et al, 2008). Harrington (1968) reported that true males could be induced directly by exposing embryos to low temperatures (below 20 C) during late stages of embryonic development (Harrington, 1967(Harrington, , 1968.…”

“…marmoratus is widely distributed in North, Central, and South America, although often locally rare (Tatarenkov et al, 2009), located throughout the eastern coasts of Florida (Indian River to Key West) and found from the Bahamas to Cuba, Jamaica, Cayman Island, Brazil, Mexico, Puerto Rico, and throughout the Caribbean (http://fishbase.org). K. marmoratus is found in marine and brackish water or hypersaline pools, and is capable of surviving rapid and extreme salinity changes (Lee et al, 2008). It is an extremely tolerant euryhaline and thermohaline species, enduring salinities ranging from freshwater to 114% (King et al, 1989) and temperatures of 7 to 38 C (Taylor et al, 1995).…”

“…Due to their unique ability to selffertilize, mangrove killifish offer a vast potential as model fish species, with a recent review suggesting their use in toxicity studies (see Lee et al, 2008), and great interest being displayed for their physiology, ecology, and developmental biology. Asynchronies in embryonic development are known to occur even in eggs within a single clutch, and such delays can be intensified in K. marmoratus due to internal self-fertilization and oviposition at various stages.…”