Teleostei (teleosts) >
Argentiniformes (Marine smelts) >
Opisthoproctidae (Barreleyes or spookfishes)
Etymology: Monacoa: The name constructed by Whitley was without any etymological reason; however, it is likely referring to the state of Monaco, in which the research expedition that sampled the two syntypes originated; niger: Name from Latin 'niger' for 'black'; referring to the black streak of pigmentation present on the sole.
Environment: milieu / climate zone / depth range / distribution range
Ecology
Marine; bathypelagic; depth range 0 - 520 m (Ref. 111070). Deep-water
Distribution
Territories | FAO areas | Ecosystems | Occurrences | Point map | Introductions | Faunafri
Eastern Central Pacific: off American Samoa and possibly Australia.
Size / Weight / Age
Maturity: Lm ?  range ? - ? cm
Max length : 4.8 cm SL male/unsexed; (Ref. 111070)
Short description
Identification keys | Morphology | Morphometrics
This species is distinguished by having black pigmentation along the entire sole and possibly have a darker or more blackish body color compared to congeners (scale pockets are darker); and the black streak on the sole possibly consists of distinct patches posteriorly . The holotype is slightly damaged on the sole and variation of its pigmentation pattern must be assessed with future fresh material (Ref. 111070).
Body shape (shape guide): short and / or deep; Cross section: other (see remarks).
Life cycle and mating behavior
Maturity | Reproduction | Spawning | Eggs | Fecundity | Larvae
Poulsen, J.Y., T. Sado, C. Hahn, I. Byrkjedal, M. Moku and M. Miya, 2016. Preservation obscures pelagic deep-sea fish diversity: doubling the number of sole-bearing opisthoproctids and resurrection of the genus Monacoa (Opisthoproctidae, Argentiniformes). Plos One 11(8):1-23. (Ref. 111070)
IUCN Red List Status (Ref. 130435: Version 2025-2)
Threat to humans
Harmless
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