Novelty doesn’t need to be prohibitively expensive or have extreme care requirements. Hannah Taylor presents a quirky fish that might just work in your community.
GIVEN THE TASK of categorising the over 2,000 species found in the ornamental aquatics trade it is inevitable that compromises have to be made somewhere. One group of species which falls foul of this philia for organising are the half-beaks, who are most often found alongside the ‘oddballs’. Of the oddballs, however, they are undoubtedly something of a contrast to the living fossil bichirs and lungfish; the highly adapted molluscivore puffers; or the benthic, rheophilic gobies. A member of the order Beloniformes, their closest relatives in the trade are the ricefishes (see feature on page 22); nonetheless, they are as closely related to these as they are to the marine flying fishes, another family within the Beloniformes.
Meet the beaks
The discrete family within the Beloniformes that the halfbeaks are part of is known as the Zenarchopteridae. This group stands out as a separate entity because most of its members are viviparous.
That is to say, despite the otherwise enormous taxonomic distance between them, they give birth to live young, just as the ‘big four’ aquarium livebearers—guppies, mollies, swordtails and platies—do.
These so-called viviparous halfbeaks are divided into five genera: whilst all 61 species amongst those genera are exceptionally streamlined, predominantly top-dwelling fish displaying marked sexual dimorphism, and occupy similar ecological niches, relatively few are found within the aquarium trade. Of those that are, by far the most common is Dermogenys pusilla, also known as the wrestling halfbeak or Malayan halfbeak.
However, the D. pusilla moniker actually encompasses a group of four species able to be differentiated only by examination of the modified anal fin the male uses for insemination; the andropodium, an instrument homologous to the gonopodium found in many other viviparious fishes.
These species are D. pusilla, D. burmanica, D. siamensis, and D. collettei. Whilst visually indistinguishable from each other, they occur in separate localities, so with collection data it is possible to identify which species you have. All have also historically been used for fish fighting throughout their native range, as the male fish can be ferocious in their spats over females, locking beaks to ‘wrestle’, and giving rise to their common name.
The wild forms of all four species are
