Otopharynx pachycheilus

Otopharynx pachycheilus (`rubberlip`), a new species of three-spot hap;
photos by Matt Arnegard, used by permission

Above: Three preserved specimens of Otopharynx sp. "rubber lips," now formally named Otopharynx pachycheilus.
Dr. Matt Arnegard, then a student at Chancellor College in Malawi, collected a novel "three-spotted" cichlid with enlarged lips in 1996. (Matt's photos, above, show variation in three preserved specimens in the type series. The holotype of the new species is shown in more detail in his black-and-white photo below. Special thanks to Matt for permission to display these photos.) Otopharynx "rubber lips," as Matt provisionally called this new species, was bottom-trawled in really deep water (78-135 meters; 256-443 feet) near Ngara, on the rocky northwestern Malawi shore (over a hard substrate with some loose cobbles), and southeast of Mbenji Island off the south-central Malawi shore of the lake (over coarse sand).
A description of the new species, by Arnegard and Snoeks (2001), has now been published. Besides describing, naming, and illustrating this distinctive new species, that publication also explores the histology and function of those lips, and suggests that they represent an accessory gustatory (taste) organ because they are provided with numerous taste buds.
Other Malawi cichlids with hypertrophied lips, in both the "hap" flock and the mbuna flock, are crevice feeders on rocky shores and are thought to use their thickened lips to seal the mouth over the crevice so it can suck out small invertebrates. Little information is known about the diet of O. pachycheilus, and nothing is known about its behavior. Arnegard and Snoeks (2001) noted that one of the paratypes contained parts of one or more shrimps (presumably Caridina nilotica), an ostracod, several minute invertebrates, and coarse sand grains. The lower pharyngeal bone has a group of enlarged teeth; these and the form of the jaw teeth and the gill rakers led the authors to suggest that O. pachycheilus may have a diet of various invertebrates, perhaps including crabs.
Arnegard and Snoeks (2001) reported the apparent breeding coloration of a male paratype, as recorded immediately after it was collected:
"Body ground color gray with metallic, powder-blue sheen. Three prominent black spots on side of body, and a series of five small dark spots along base of dorsal fin. This pattern of spots underlain by six faint gray bars along side of body and one on side of caudal peduncle. Cheek and operculum with purple-pink and metallic powder blue highlights. Snout gray-brown. Lips dusky with powder-blue sheen. Gular and chest dusky gray. Dorsal fin gray-brown with thin, black submarginal band, white lappets, and yellow-orange tips. Interradial membranes in rayed portion of dorsal fin contain yellow spots, each with dark halo. Pelvic fins black with white leading edges. Interradial membranes of caudal fin with dusky yellow spots. Dorsal and ventral margins of caudal fin black. Anal fin dusky with wide, black submarginal band and six yellow-white ocelli." (p. 711)

I have not had the opportunity to examine specimens of Otopharynx pachycheilus. However, because of its deep body shape, the relatively large total length of at least 20 cm (7.9 inches), and the size, shape, and placement of its spots, I strongly suspect that this unusual new form is the sister species of the shallow-water rocky shore cichlid Otopharynx heterodon.

The Cichlid Fishes of Lake Malawi, Africa: MalawiCichlids.com