The Natural History of Model Organisms: The untapped potential of medaka and its wild relatives

  1. Leon Hilgers  Is a corresponding author
  2. Julia Schwarzer  Is a corresponding author
  1. Zoological Research Museum Alexander Koenig, Germany
3 figures and 1 table


Oryzias latipes.

(A) Male (right) and female (left) Oryzias latipes from Kiyosu (Photo by Felix Loosli). Males can be easily distinguished from females by their elongated anal and dorsal fins. (B) A school of medaka in their natural habitat. (C) Approximate distributional limits of the ricefishes family, the Adrianichthyidae (black), following Parenti (2008) with the locations from which some of the most famous medaka strains are derived (blue). The Indonesian island Sulawesi represents a ricefish biodiversity hotspot (red).
Ricefish diversity.

(A) Combined phylogeny based on published studies from: Katsumura et al., 2019, Parenti, 2008; Magtoon, 2010; Mokodongan and Yamahira, 2015Takehana et al., 2005. Sex determination systems and linkage groups with sex determination (SD) genes are given in the gray and blue columns, respectively (based on Matsuda and Sakaizumi, 2016 and Myosho et al., 2015). Species defined as miniaturized (following Parenti, 2008) are marked with black/white fish. Detailed distribution maps are provided for the O. latipes species complex and for the celebensis species group. Divergence times in the tree are based on: 1Takehana et al., 2003; 2aKatsumura et al., 2019: scenario III; 2bKatsumura et al., 2019: scenario IV; 3Mokodongan and Yamahira, 2015; 4Hughes et al., 2018. (B) Total number of described species from the first description of a ricefish in 1822 (Hamilton, 1822) until today (red line) in relation to described Sulawesi endemics (gray bars). The high number of newly described species in recent years especially on Sulawesi points towards a largely underexplored ricefish diversity. (C) Diversity in coloration and shapes of male Oryzias. From left to right and top to bottom: O. sarasinorum*, O. woworae§, O. eversi*, O. wolasi*, O. nigrimas*, O. dancena§, O. minutillus§, O. mekongensis§ (Photos were taken by A Wagnitz* and J Geck§).
Box 2—figure 1
Overview of pelvic brooding.

(A) The pelvic brooding ricefish O. eversi carries its eggs until the fry hatches (dashed box indicates section depicted in (C)). (B) Once the fry has hatched, only the filaments remain attached to the female (Photo by Hans-Georg Evers). (C) A schematic overview of anatomic structures that likely play a role in pelvic brooding. The eggs (e) stay attached to the female via attaching filaments (af). A plug (p) anchors the attaching filaments (af) inside the female’s ovarian cavity (oc) next to the ovary (o). Compared to their non-pelvic brooding relatives, pelvic brooding species further appear to have elongated pelvic fins (pf) that cover the eggs and a heavily pigmented, enlarged genital papilla (gp), whose role in pelvic brooding is unclear.


Table 1
Medaka nomenclature.

The model organism medaka comprises several species and deeply divergent lineages from the Oryzias latipes species complex. Hence, in this article we only use the term “medaka” when we collectively refer to lineages within the Oryzias latipes species complex in the context of the model system. Common or scientific species names are used to specifically refer to individual lineages as shown in this table.
Common namesScientific name
Japanese medaka, Southern (Japanese) populationO. latipes
Northern medaka, Northern (Japanese) populationO. sakaizumii
East Korean populationN/A
China–West Korean populationO. sinensis
Chinese medakaO. sinensis
Taiwanese population, Taiwanese medakaO. cf. sinensis

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  1. Leon Hilgers
  2. Julia Schwarzer
The Natural History of Model Organisms: The untapped potential of medaka and its wild relatives
eLife 8:e46994.