Chaunax atimovatae – Southern frogmouth

Chaunax atimovatae – Southern frogmouth ©FAO/M. Lipperi

The Southern frogmouth is a striking member of the sea toad family (Chaunacidae), described in 2016 from the Mozambique Channel in the Western Indian Ocean. With its vivid reddish-orange coloration adorned with distinctive green spots surrounded by yellow, this beautifully patterned sea toad is a remarkable addition to the ichthyofauna of the Western Indian Ocean. Its discovery highlights how much remains to be learned about deepwater biodiversity in this region.

Features and characteristics

Chaunax atimovatae is characterized by a globose body, a broad depressed head, and a wide upturned mouth typical of toadfishes. The skin is densely covered with small spinules that give it a velvety texture. Unlike the species’ shallow-water relatives, its coloration is bright reddish-orange with distinctive round green spots surrounded by yellow, which remain visible as pale spots even after preservation. Its colour pattern, together with gill rakers and neuromasts counts, distinguishes C. atimovatae from other known species of Chaunax.

As with other chaunacids, it possesses a small illicium (modified dorsal-fin spine) on the snout, tipped with an esca (lure), which it uses to attract prey in the dimly-lit depths. The pectoral fins are broad and limb-like, allowing the fish to ‘walk’ clumsily on the seafloor in addition to swimming short distances.

The discovery

During a 2007 expedition aboard the research vessel Dr. Fridtjof Nansen, specimens of an unusual chaunacid were collected from a deep trawl station in the Mozambique Channel at depths of around 500 m. Careful examination revealed that the specimens differed from all previously described Chaunax species through a unique combination of coloration, spinule distribution, and gill rakers and neuromasts counts. The species was formally described in 2016 by the eminent ichthyologists Hsuan-Ching Ho and Wen-Chun Ma, who named it Chaunax atimovatae for the trawler Atimo Vatae (Madagascan for ‘deep south’), from which many Madagascan specimens were collected, including those in the type series.

Left/Top: Dorsal view of Chaunax atimovatae (16 cm SL, R/V Dr. Fridtjof Nansen Tanzania survey). ©FAO/S. Bogorodsky

Right/Bottom: Dorsal view of the head of Chaunax atimovatae (16 cm SL, R/V Dr. Fridtjof Nansen Tanzania survey). The arrow shows the illicium tipped with the esca. ©FAO/ S. Bogorodsky

Little is known about the ecology of C. atimovatae, but like other sea toads it is a benthic ambush predator. It is thought to feed on small fishes and invertebrates, luring them within striking distance using its esca. Its globose body and sedentary habits make it well suited to life on soft bottoms of the continental slope.

Like other toadfish species, C. atimovatae relies on camouflage and stillness, blending into the substrate to surprise passing prey.

Although direct observations are lacking, chaunacids are known to be opportunistic predators. Their diet likely consists of small fishes, shrimps, and cephalopods, which are sucked in by the powerful jaws and expandable throat.

While not targeted by fisheries, C. atimovatae forms part of the little-known deep benthic food web of the Mozambique Channel. It serves as both predator of small invertebrates and prey for larger deepwater fishes. The discovery of this species underscores the importance of deep-sea surveys in documenting biodiversity before it is impacted by fisheries or environmental change.

Geographical distribution

So far, Chaunax atimovatae has only been recorded from the Western Indian Ocean (Madagascar, Mozambique and South Africa), at depths of 146–637 m. Its restricted known range makes it a species of particular biogeographical and conservation interest.

Resources

• Ho H.C. & Ma W.C. (2016). Revision of southern African species of the anglerfish genus Chaunax (Lophiiformes: Chaunacidae), with descriptions of three new species. Zootaxa, 4144 (2): 175–194. https://dx.doi.org/10.11646/zootaxa.4144.2.2.