Pseudanthias emma – Emma's basslet

Pseudanthias emma – Emma's basslet ©FAO/E. D’Antoni

Emma’s basslet belongs to a large group of fishes, commonly known as fairy basslets, that are among the most beautifully coloured in the world. It inhabits the mesophotic (twilight) coral ecosystems of the eastern Indian Ocean; this type of habitat has been poorly explored in the region to date, and new and exciting discoveries are waiting to be made. The species has a quite unique coloration: the body is mostly orange with a bright pink band on the upper sides; the head displays a broad orange bar crossing the eye; and the caudal fin is bright red posteriorly. Among the most distinctive features is the presence of two long transparent trailing filaments coming off the caudal fin.

The discovery

In 2015, the EAF-Nansen Programme, in cooperation with the government of Myanmar, conducted a trawl survey using the research vessel Dr. Fridtjof Nansen off the coast of Myanmar. The goal was to obtain biological and environmental information for the study area, and identify local species diversity for the compilation of a FAO marine species identification guide for fisheries. During the cruise, several fairy basslet specimens representing five species were collected, including a distinctive new species of the genus Pseudanthias. FAO’s on-board taxonomist Peter Psomadakis secured these specimens for follow-up studies on land, and joined forces with Anthony Gill, an Australian ichthyologist, to formally describe the new species.

Features and characteristics

Emma’s basslet has a moderately deep body, a dorsal fin with 10 spines and 16 soft rays, 18 pectoral-fin rays, 42 lateral-line scales, and a weakly concave caudal fin with elongate filaments on its upper and lower lobes. It closely resembles Pillai’s anthias (Pseudanthias pillai, Heemstra & Akhilesh [2012]) in general form and coloration. Nonetheless, Pseudanthias emma differs substantially from P. pillai in having fewer gill rakers and more lateral-line scales, as well as a deeper caudal peduncle, a longer third dorsal-fin spine, a shorter head, a broader interorbital, and a more concave caudal fin (this also has no trailing filaments in P. pillai). Other differences appear in the coloration of the anal and pelvic fins, which are tipped with red in Pseudanthias emma but are more solidly coloured in P. pillai. The caudal fins are similarly diagnostic, with Emma’s being more deeply coloured in red posteriorly, while Pillai’s is solidly magenta throughout.

Like other members of the group, Emma’s basslet is a protogynous hermaphrodite, with males developing by the transformation of large females, and with different colour patterns for the male and female. Males maintain a large harem of females; removal of the male results in sex reversal of the dominant female, who changes colour pattern and takes over the harem.

No information is available on the diet of Emma’s basslet. Most likely, it feeds on large zooplankton, crustaceans and small fishes. Small anthiadids, such as Pseudanthias species, form large aggregations which rise from their rocky bottom habitats to feed on zooplankton. Away from their coral or rocky reef shelter, these small fishes are preyed upon by roving large predaceous fishes such as jacks and by resident reef predators such as groupers, scorpionfishes and morays.

In summary, with their vibrant colours, anthiadines not only contribute to the beauty and biodiversity of the reef environment but also play an important role in the coral reef ecosystem as prey for larger fish and predators.

Geographical distribution

Known only from a single male specimen trawled in the proximity of a mesophotic coral reef (105 m) off the southeast coast of Myanmar in the Andaman Sea (eastern Indian Ocean). Mesophotic coral ecosystems are characterized by the presence of light-dependant corals typically found between depths of 40 m to more than 150 m.

Pseudanthias emma, 10.7 cm Standard length, male holotype ©P. Psomadakis/FAO

Resources

• Gill, A. C.; Psomadakis, P. N. (2018). Pseudanthias emma new species, with notes on a collection of anthiadine serranid fishes from off Myanmar (eastern Indian Ocean). Zootaxa. 4455(3): 525., available online at https://doi.org/10.11646/zootaxa.4455.3.8