About the Black-Winged Hatchetfish
Species Type: Freshwater Fish
Care Level: Moderate. May tolerate only a narrow range of water parameters, have specific dietary requirements including frozen or even live foods, may have behaviors that severely limit potential tankmates or may require a specialized aquarium setup.
Origin: Widespread through the floodplain of the Rio Negro basin in Brazil. Gery (1977) reports this species from the upper Rio Orinoco in Venezuela but this is not certain [see Piggott et al. (2011)] . Found in small, shaded and shallow woodland streams and in flooded forest during the wet season.
Compatibility/Temperament: A peaceful, sensitive fish, must be in groups minimum six but preferably more. The second photo shows a shoal of Carnegiella marthae with a few C. strigata. Suitable with small peaceful fish such as small characins, rasbora (including the dwarf species), pencilfish, dwarf cichlids from South America, peaceful substrate fish.
The hatchetfishes are surface fish identified by their rounded keel. The family name Gasteropelecidae comes from the Greek "gaster" [=stomach] and "pelekis" [= axe], an obvious reference to the fishes' shape. The large pectoral fins are attached by powerful muscles that propel the fish from the water, enabling it to glide considerable distances of several feet through the air. Studies by Francine Weist (1995) concluded that the pectoral fins are not moved during this "flight" but are used as a powerful thruster to propel the fish from the water as well as to prevent the fish from diving too deeply upon its return to the water [reported in Weitzman & Palmer (1996)].
The aquarium must be well covered, and careful attention during maintenance is necessary as the fish will quickly jump if alarmed or frightened. The writer has lost fish overnight as the consequence of leaving the glass cover open only by an inch after feeding. Newly-imported fish are very sensitive and must be carefully acclimated but once established they are hardy. Does not do well in water that is not soft and acidic.
Very suitable to a well-planted aquarium containing floating plants with some open spaces between them. Water flow should be minimal, replicating their natural habitat [see comments under Origin]. There are no external gender differences; females are rounder when viewed from above.
The species in Carnegiella are the smallest of the hatchetfishes. An almost identical but slightly smaller species to Carnegiella marthae, C. schereri, occurs in the Peruvian Amazon basin. C. myersi, the smallest species, has a shallower keel which makes it appear much longer; it occurs in the Peruvian Amazon. All three species are basic silver with varying darker dots, dashes or lines across the keel. The marble hatchetfish, C. strigata (Guenther, 1864) is the fourth species in the genus. All these species are included in our profiles.
The family Gasteropelecidae contains three genera: Thoracocharax with two species, Gasteropelecus also with two species [G. levis is possibly a third species (Weitzman, 1996)] and the four recognized species in Carnegiella; the latter are the most derived or specialized of the hatchetfishes. Weitzman & Palmer hypothesize on the basis of their anatomy that these three genera had a common ancestor in the distant past that was related to some other characiform subgroup, making this family monophyletic. The species in Carnegiella do not possess an adipose fin.
The species in Carnegiella show geographic variations according to the locality. This has long been recognized with the marble hatchetfish which at various times had five recognized species. The subject species, the "Black-winged hatchetfish," is widespread in the Rio Negro floodplain (Brazil). Very recent research has identified highly differentiated and divergent population groups representing three cryptic species (Piggott, et al., 2011). Two colour morphs were discovered; the dark morph has 12 dark oblique lines across the body, whereas on the light colour morph these are diffused dotted lines. Other differentiating features include the number of soft anal fin rays, the number of tricuspid teeth on the dentary bone, and several morphometric measurements. The two colour morphs are shown in the last photo above that is taken from Piggott (2011).
The dark morph is the more prevalent in the Rio Negro basin, and represents genetic group C in the study, while the white morph represents genetic group A. Genetic group B fishes are morphologically similar to the dark Group C morph but the authors point out that additional sampling will be needed to test for morphological divergence between Group B and the other two groups. Fish from Groups A and C live sympatrically in at least two creeks and can even be caught together in the same net. Yet they demonstrate complete and intrinsic reproductive isolation [=not based on geographic barriers]. Partial reproductive isolation was identified for Groups B and C, with a small sampling of putative hybrids.
C. marthae was described by G.S. Meyers in 1927. The species epithet honours Dr. Meyers wife, Martha, who was especially fond of this species. The genus Carnegiella was erected in 1909 by C.H. Eigenmann for the type species C. strigata which was at that time named Gasteropelecus strigatus; the name honours Miss Margaret Carnegie and was chosen to represent the gracefulness of these fish.
Piggott, Maxine P., Ning L. Chao and Luciano B. Beheregaray (2011), "Three fishes in one: cryptic species in an Amazonian floodplain forest specialist," Biological Journal of the Linnean Society, 2011, Volume 102, Number 2, pp. 391-403.
Weitzman, Stanley H. and Lisa Palmer (1996), "Do Freshwater Hatchetfishes Really Fly," Tropical Fish Hobbyist, September 1996, pp. 195-206.
Weitzman, Stanley H. and Lisa Palmer (2003), "Family Gasteropelecidae" in Checklist of the Freshwater Fishes of Central and South America, ed. Roberto E. Reis, Sven O. Kullander and Carl J. Ferraris; Porto Alegre: Edipucrs, pp. 101-103.
Wiest, F.C. (1995), "The specialized locomotory apparatus of the freshwater hatchetfish family Gasteropelecidae," Journal of Zoology, No. 236, pp. 571-592.
Black-Winged Hatchetfish Diet
Feeds primarily on insects that are on or land on the water surface. Will accept most prepared foods that float; wingless fruit flies and ants are ideal.
Grows to 1.5 inches, but usually smaller in aquaria.
Minimum Tank Suggestion
18 inches in length
Ideal water parameters for Black-Winged Hatchetfish
Soft (hardness less than 4 dGH) slightly acidic (pH 5.5 to 6.5) water, temperature 23-27C/73-81F.