Taxonomy & naming
Otopharynx argyrosoma was described in 1922 by the British ichthyologist Charles Tate Regan, originally within the broad early-twentieth-century concept of Haplochromis. The holotype (BMNH 1908.10.27.99) was collected by E.L. Rhoades and is simply labelled 'Nyasa,' the old name for Lake Malaŵi, with no finer locality — typical of material from that era. The species was later placed in Otopharynx, the genus raised by Regan in 1920 for the lake's laterally spotted, non-mbuna haplochromines and subsequently revised by Eccles and Trewavas in their 1989 classification of Malaŵian cichlid genera. Eschmeyer's Catalog of Fishes lists it as valid as Otopharynx argyrosoma (Regan, 1922), the parentheses around the authorship marking its transfer out of the genus in which it was first named. The epithet argyrosoma combines the Greek argyros, 'silver,' with sōma, 'body,' describing the fish's silvery, reflective flanks.
Morphology
Otopharynx argyrosoma is a fusiform, normally proportioned haplochromine reaching about 6 in total length. As the name suggests, the living fish is notably silvery on the flanks, with the laterally spotted melanin pattern typical of the genus — discrete dark blotches (a suprapectoral or shoulder spot and spots further back along the body) rather than the bold vertical bars of some relatives. Indeed, Oliver (2018) used the absence of distinct vertical bars below the dorsal fin as one character separating Otopharynx argyrosoma from the barred Otopharynx aletes. It carries more lateral-line scales than the small cave-dweller Otopharynx antron, which has 29–31. Detailed sexual-dimorphism notes are sparse in the older literature, but as in most Malaŵi haps, breeding males would be expected to be more strongly and colourfully marked than the silvery females and non-breeding fish.
Habitat
Otopharynx argyrosoma is a fish of sandy bottoms in Lake Malaŵi, occurring across both shallow and deeper regions of the lake over open sand. FishBase characterises it as a demersal, freshwater species ranging across the lake's tropical waters (roughly 9°S to 15°S), and the older literature (Maréchal in the CLOFFA checklist; Eccles and others) treats it as a fairly widespread Malaŵi endemic rather than a narrow-range specialist. This places it among the open-sand and sediment-associated haplochromines of the lake, distinct from the rock-dwelling mbuna and from the cave-bound members of its own genus. Its tolerance of a range of depths over sand, rather than dependence on a single narrow habitat, is consistent with the relatively secure conservation status it has been given.
Feeding
Otopharynx argyrosoma feeds on small invertebrates and plankton, taken both from the sand and from the open water. This dual strategy — gleaning small benthic invertebrates from the substrate while also picking plankton from the water column — is documented in the older Malaŵi cichlid literature and is reflected in FishBase's account. It corresponds to an estimated trophic level of about 3.5, placing the species as a small-prey carnivore/planktivore rather than a herbivore or a hard-shell crusher. Its silvery, open-water-tolerant build fits this flexible feeding mode well, allowing it to exploit both the benthos and the plankton over the sandy shelf where it lives.
Mating
Courtship behaviour has not been described in detail for Otopharynx argyrosoma, but it conforms to the reproductive pattern of Lake Malaŵi's sand-dwelling haplochromines: a polygynous maternal mouthbrooder in which males court females rather than forming pairs. Many open-sand haps of the lake breed in a lek-like system, with males establishing temporary display sites on the sand — sometimes simple cleared scrapes — over which they court passing females, who choose among competing, brightly coloured males. Spawning culminates in the female taking the eggs into her mouth, with the male's anal-fin egg-dummies mediating fertilisation. Whether Otopharynx argyrosoma males construct any spawning structure or simply display over open sand is not specifically recorded; the general picture is inferred from its many sand-dwelling relatives.
Breeding
No detailed breeding study — clutch size, egg dimensions, incubation period or fry development — has been published specifically for Otopharynx argyrosoma. By the consistent pattern of the Malaŵi haplochromine flock, it is a maternal mouthbrooder: the female incubates the fertilised eggs in her buccal cavity, typically for around three weeks, then releases free-swimming fry that may shelter back in her mouth when danger threatens. Clutches in this group of haps are moderate in size, with comparatively large, yolky eggs and well-developed fry, the standard mouthbrooder trade-off of fewer but better-provisioned young. The particulars for this species remain undocumented and are extrapolated from its relatives.
In the aquarium
Otopharynx argyrosoma has a modest place in the aquarium world: FishBase lists it as of commercial interest both as a food fish and in the aquarium trade, and it carries the local name saguga. It is not, however, a hobby staple in the way the most colourful Malaŵi 'peacocks' and mbuna are, and dedicated captive-keeping and breeding accounts are thin.
For a keeper who did obtain it, its requirements would follow those of a medium-sized Malaŵi sand-hap. It needs hard, alkaline Rift-lake water; a spacious tank with a deep sand bed and open swimming room rather than a rock-packed mbuna layout; and a varied carnivore/planktivore diet of small frozen and prepared foods reflecting its natural mix of benthic invertebrates and plankton. As an actively swimming, generally non-mbuna sand fish, it would suit a roomy community of similarly sized, comparably tempered Malaŵi haplochromines. These notes reflect the niche and the limited trade record rather than an extensive body of aquarium experience with this particular species.
Conservation
Otopharynx argyrosoma was assessed by the IUCN Red List as Least Concern in 2018. The classification reflects its status as a relatively widespread Lake Malaŵi endemic occurring over sandy habitat across a range of depths, rather than a narrow-range specialist, and the absence of evidence for a severe, range-wide decline. As with all the lake's fishes, this sits within a setting of real and growing pressures — heavy artisanal and commercial fishing (including trawl and seine fisheries that take saguga-type haps), sedimentation and nutrient loading from a developing catchment, and the longer-term effects of a warming, increasingly stratified lake. Being a sand generalist of broad depth tolerance probably buffers Otopharynx argyrosoma against these pressures relative to more specialised endemics, supporting its Least Concern listing, but the health of Lake Malaŵi's sandy-shelf fisheries warrants ongoing attention.