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Trophic Adaptations

ne of the reasons evolutionary biologists are so enchanted by the cichlid species metaflock of Lake Malawi is that, because of intense competition for food, the hundreds of species have evolved many (presumed) specializations to exploit a seemingly endless array of diets. Some species eat foods typical of "ordinary" fish communities vascular plants; insects; small fish. But others are unusual, even unique, in the novel foods exploited, peculiar structural adaptations, bizarre feeding behavior, use of aggressive mimicry, and other features. By "adaptation", I mean "...an anatomical, physiological, or behavioral trait that contributes to an individual's ability to survive and reproduce ('fitness') in competition with conspecifics in the environment in which it evolved" (G.C. Williams, 1966. Adaptation and Natural Selection. Princeton Univ. Press).

Some examples of Malawi cichlids' trophic (feeding) adaptations, both ordinary and extraordinary, are showcased in the tables below. I hope that this section will be of interest and value to students and teachers of biology classes as well as to more general visitors. For each species, there is a photograph (by M.K. Oliver, unless noted) along with the scientific name of the fish; the species flock to which it belongs (Mbuna or "Hap"); its primary food(s); a brief summary of known or suspected trophic adaptations of behavior, anatomy, and coloration; and pertinent literature. Clicking on any photo will take you to my page for that species, where there may be larger photos and more information. Sufferers of ichthyophobia, a fear of fish, may be uncomfortable looking at these Cichlid photos. Mental health experts at Morningside Recovery may use fish photos to aid in the recovery of ichthyophobia patients.

Piscivores   Zooplankton feeders   Lepidophages   Fin biters   Ectoparasite cleaners   Molluscivores   Crevice feeders   Periphyton collectors   Aufwuchs feeders   Paedophages  

Piscivores (Fish-eating Predators)
Picture
(click for species page)
Cichlid species Group Food Adaptations Reference

Photo: F. Panis
Aristochromis christyi "Hap" flock Ambush predator of small cichlids; also crevice feeder on fry Behavior: On rocky and intermediate shores. Approaches prey slowly, rolls onto side, observes prey with one eye, and suddenly strikes head sideways. Also feeds on fry hiding in horizontal cracks in rocks. Anatomy: Head compressed; jaws narrow, beaklike (can reach into narrow cracks), but mouth can widen greatly when open. Ribbink et al. (1983)
Konings (1995c: 114-115)

Photo: F. Panis
Champsochromis caeruleus "Hap" flock Pursuit predator of small fish Behavior: Found over sandy or soft substrate in open water. Chases and eats usipa (small silvery shoaling minnows resembling anchovies) and other small fish. Anatomy: Body elongate, streamlined. Teeth in outer row of jaws widely spaced, slightly incurved, conical. Eccles & Trewavas (1989)
Dimidiochromis compressiceps "Hap" flock Ambush predator of small fish Behavior: Hunts head-down in Vallisneria weed beds, keeping narrow body outline toward prey. Coloration: Pale green stripes on flanks and one on dorsal midline of head camouflage the head-down fish among straplike Vallisneria leaves. Anatomy: Head and body strongly compressed laterally, minimizing width presented to prey. Fryer & Iles (1972)
Melanochromis melanopterus Mbuna flock Omnivorous, but specialized as a predator of fish fry Behavior: Hunts for fry of Mbuna and other fishes among rocks; also eats zooplankton, insect larvae, benthic crustaceans, loose Aufwuchs, and filamentous algae. Coloration: Dark coloration probably renders fish inconspicuous while hunting. Anatomy: Head and body elongate for an Mbuna. Ribbink et al. (1983)
Nimbochromis livingstonii "Hap" flock Ambush predator of small fish Behavior: Feigns death, lying motionless on its side. Coloration: Mimics a rotting fish, luring small fish within range. Fryer & Iles (1972)
McKaye (1981)
Rhamphochromis `long fin yellow' "Hap" flock Pursuit predator of small fish Behavior: Has not been observed. Coloration: Countershading and silvery flanks may render fish inconspicuous to prey over brightly lit sandy substrate. Anatomy: Large, widely spaced conical jaw teeth retain captured fish. Turner (1996)
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Zooplankton Feeders
Picture
(click for species page)
Cichlid species Group Food Adaptations Reference
Copadichromis mloto
(and others)
"Hap" flock (utaka group) Zooplankton Behavior: Shoaling species. Anatomy: Highly protrusible mouth shoots forward to form a tube; resulting negative pressure in mouth pulls in plankter. Fryer & Iles (1972)
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Lepidophages (Scale Eaters)
Picture
(click for species page)
Cichlid species Group Food Adaptations Reference
Corematodus shiranus "Hap" flock Cichlid scales Behavior: Swims among schools of tilapia cichlids of the genus Oreochromis, of which it is an aggressive mimic. Coloration: Remarkably like that of its vertically barred prey. Anatomy: Broad bands of filelike teeth in both jaws rasp victim's scales from caudal peduncle. Trewavas (1947)
Fryer & Iles (1972)
Corematodus taeniatus "Hap" flock Cichlid scales Behavior: Swims among oblique-striped "haps." Coloration: Oblique dark stripe; an aggressive mimic of numerous silvery, oblique-striped species. Anatomy: Same as C. shiranus (above): jaw teeth in wide, filelike bands. Fryer & Iles (1972)
Docimodus evelynae "Hap" flock Cichlid & cyprinid scales; catfish skin Behavior: Juveniles thought to behave as cleaners. Adult scale- and skin-feeding behavior unknown (but confirmed by stomach contents and by finding trawled catfishes with holes in skin). Anatomy: Jaw teeth stout, simple, slightly recurved. Eccles & Lewis (1976)
Ribbink et al. (1983:249)

Photo: A.J. Ribbink
Melanochromis lepidiadaptes Mbuna flock Cichlid scales Behavior: Nonterritorial; schools at rocky reefs over sand-rock interface. Feeding behavior unknown, but stomach contents consistently contain cichlid scales only. Anatomy: No obvious anatomical specializations for lepidophagy. Ribbink et al. (1983:204)
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Fin Biters
Picture
(click for species page)
Cichlid species Group Food Adaptations Reference
Genyochromis mento Mbuna flock Cichlid fins & scales Behavior: Skulks close to Mbuna, bites pieces from caudal or anal fin; sometimes rasps scales from flanks or caudal peduncle. Coloration: Polymorphic, morph shown is inconspicuous, other morphs thought to mimic locally common prey species (aggressive mimicry). Anatomy: Broad, strong lower jaw with stout, sharp bicuspid teeth. Ribbink et al. (1983)
Konings (1995c)
Docimodus johnstonii "Hap" flock Catfish fins Behavior: Unknown, but diet confirmed by stomach contents. Anatomy: Broad, strong lower jaw with stout unicuspid teeth convergently resembling those of Genyochromis. Eccles & Lewis (1976)
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Ectoparasite Cleaners
Picture
(click for species page)
Cichlid species Group Food Adaptations Reference

Photo: A. Konings
Maylandia crabro Mbuna flock Fish lice, and other foods Behavior: Facultative cleaner of Argulus (parasitic crustaceans) from large Bagrus catfish. Also eats other, varied foods including Bagrus eggs. Coloration: Distinctive "bumblebee" colors may advertise cleaning service. Ribbink & Lewis (1982)
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Molluscivores
Picture
(click for species page)
Cichlid species Group Food Adaptations Reference
Trematocranus placodon "Hap" flock Snails Behavior: Picks small snails from sandy substrates, using the mouth. Crushes the shells between the upper and lower pharyngeal jaws in the throat. Anatomy: Massive pharyngeal jaws with enlarged teeth, and heavy musculature to power these jaws. Fryer & Iles (1972)
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Crevice Feeders
Picture
(click for species page)
Cichlid species Group Food Adaptations Reference
Abactochromis labrosus Mbuna flock Insect larvae, small crustaceans, etc. Behavior: Skulks on rocky shores. Fits its narrow head and mouth and soft, enlarged lips, in which taste buds are densely arranged, in crevices; some observers believe it seals the crevices with the lips; it then sucks out the insect larvae or other invertebrates. Often turns on its side to feed in horizontal cracks. Anatomy: Soft, fleshy lips with elongate median lobes; laterally compressed head and jaws. Ribbink et al. (1983)
Oliver & Arnegard (2010)
Cheilochromis euchilus "Hap" flock Insect larvae Behavior: Feeds on rocky shores and at rocks on intermediate sand/rock habitat, sealing rounded holes with its lips and sucking out insect larvae in them. Anatomy: Fleshy, flaccid lips with large median lobes. Eccles & Trewavas (1989)
Konings (1995c)
Lichnochromis acuticeps "Hap" flock Insect larvae, young Mbuna cichlids Behavior: Wanders along rocky shores and intermediate zone, reaching deep into cracks and spaces between rocks to extract young Mbuna and larval insects. Turns on side to probe horizontal cracks.Anatomy: Laterally compressed head and body, narrow jaws with fleshy lips without median lobes. Eccles & Trewavas (1989)
Konings (1995c)

Photo: C. K. Larsen
Mylochromis labidodon "Hap" flock Insect larvae, small crustaceans, etc. Behavior: On pebble beds in intermediate zone, feeds on small hidden organisms by grasping pebbles with its jaws and turning them over to reveal any edible invertebrates (video available). Anatomy: Distinctive lower jaw dentition reminiscent of Labidochromis, with anterior teeth abruptly larger and angled forward. Konings (1995c)
Eccles & Trewavas (1989)
Placidochromis milomo "Hap" flock Insect larvae, small crustaceans, etc. Behavior: Convergently similar to C. euchilus (above), on rocky shores. Anatomy: Fleshy lips with large median lobes. Larger body size of adult permits feeding on larger crevice-dwelling invertebrates. Oliver (1984)
Konings (1995c)
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Collectors of Periphyton (algae growing on plants)
Picture
(click for species page)
Cichlid species Group Food Adaptations Reference
Cyathochromis obliquidens Mbuna flock Periphyton on Vallisneria leaves; also Aufwuchs on rocks Behavior: In intermediate sand/rock zone, combs algae from leaves of Vallisneria aethiopica plants and from rocks. Anatomy: Slender, movably implanted jaw teeth with crowns inclined obliquely toward midline of jaw; tooth crowns can conform to leaf or rock surface. Fryer & Iles (1972)
Ribbink et al. (1983)
Hemitilapia oxyrhynchus "Hap" flock Periphyton on Vallisneria leaves Behavior: Nibbles algae from leaves of Vallisneria aethiopica plants on sandy shores, often turning on its side to grasp each leaf. Anatomy: Spadelike lower jaw with movably implanted teeth which conform to leaf surface. Fryer & Iles (1972)
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Eaters of Aufwuchs — i.e., algae growing on rocks, wood, or other surfaces
Picture
(click for species page)
Cichlid species Group Food Adaptations Reference
Labeotropheus trewavasae Mbuna flock Both loose and firmly attached Aufwuchs; also benthic and planktonic crustaceans Behavior: Nibbles algae, often from undersides of rocks. Body nearly parallel to rock. Anatomy: Wide, inferior (underslung) mouth; both jaws with straight outer row of closely spaced tricuspid teeth which form scraping surfaces. Fryer & Iles (1972)
Ribbink et al. (1983)
Petrotilapia tridentiger Mbuna flock Loose Aufwuchs; also zooplankton, phytoplankton, detritus, fish eggs & fry Behavior: Combs loose Aufwuchs with jaws pressed against rock surface and body at right angles to surface. Anatomy: Wide, terminal mouth; both jaws with numerous rows of long, slender, movably implanted, tricuspid teeth. Fryer & Iles (1972)
Ribbink et al. (1983)
Pseudotropheus (Maylandia) zebra Mbuna flock Loose Aufwuchs (also zooplankton and benthic invertebrates when available) Behavior: Presses mouth against rocks, closes and opens mouth repeatedly while pressed. Anatomy: Large, mobile, terminal mouth with bicuspid outer and widely spaced, tricuspid inner teeth, which comb only loosely attached algae from rocks. Fryer & Iles (1972)
Holzberg (1978)

Photo: J. Stewart
Pseudotropheus (Pseudotropheus) sp. "acei" Mbuna flock Aufwuchs growing on waterlogged tree logs and branches (epixylic algae) Behavior: Aggregates in large shoals over submerged tree trunks and limbs that have washed into the lake, feeding on algae growing on the wood. Anatomy: Dentition similar to that of many specialists on algae growing on stones (epilithic algae). Konings (1995c)
Pseudotropheus (Tropheops) tropheops Mbuna flock Firmly attached Aufwuchs (Calothrix spp.) and some loose Aufwuchs; also zooplankton and benthic invertebrates Behavior: Plucks algae from rocks with sideways, upward head jerks. Anatomy: Steeply inclined snout; small, slightly subterminal mouth with bicuspid outer and numerous, close-set inner tricuspid teeth which rasp firmly attached algae from rocks; enlarged lateral conical teeth help cut strands. Fryer & Iles (1972)
Ribbink et al. (1983)
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Paedophages (robbers of eggs or larvae from mouthbrooding cichlids)
Picture
(click for species page)
Cichlid species Group Food Adaptations Reference
Caprichromis orthognathus "Hap" flock Cichlid eggs/larvae Behavior: Uncommon fish found over sand. Confirmed paedophage; rams heads of mouthbrooding female cichlids from below and behind, causing them to spit out their brood. Anatomy: Massive lower jaw and nearly vertical gape. Coloration: Oblique stripe displayed or hidden, to match color pattern of multiple prey species (aggressive mimic). McKaye & Kocher (1983)
Diplotaxodon greenwoodi "Hap" flock Cichlid eggs/larvae(?) Behavior: Suspected deep-water paedophage; behavior unknown. Anatomy: Enormous, elongated lower jaw and steeply inclined gape. Stauffer & McKaye (1986)
Naevochromis chrysogaster "Hap" flock Cichlid eggs/larvae(?) Behavior: Uncommon, on sandy shores. Feeding behavior unknown. Anatomy: Specialized jaws, which are heavy, short; lower jaw with chin knob. Teeth small, movable, bi- and tricuspid; nearly buried in thickened, papillose oral mucosa. Function in feeding is unknown; suspected paedophage. Eccles & Trewavas (1989:24)
Konings (1995c)
Protomelas spilopterus "Hap" flock Cichlid eggs/larvae(?) Behavior: Uncommon sandy shore fish; feeding behavior unknown. Anatomy: Specialized, somewhat oblique jaws; lower jaw massive. Outer teeth stout, unicuspid or with minute lateral cusp; crowns erect or curved forward (lower jaw). Suspected paedophage.
Eccles & Trewavas (1989:70)
Konings (1995c:207-9)
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Last Update: 16 May 2014
Web Author: M. K. Oliver, Ph.D.
Copyright © 1997-2014 by M. K. Oliver - ALL RIGHTS RESERVED

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