''Variabilichromis moorii'' has no common name and is a
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of
freshwater
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
cichlid
Cichlids are fish from the family Cichlidae in the order Cichliformes. Cichlids were traditionally classed in a suborder, the Labroidei, along with the wrasses ( Labridae), in the order Perciformes, but molecular studies have contradicted this ...
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
to
Lake Tanganyika
Lake Tanganyika () is an African Great Lake. It is the second-oldest freshwater lake in the world, the second-largest by volume, and the second-deepest, in all cases after Lake Baikal in Siberia. It is the world's longest freshwater lake. ...
in eastern Africa. It is a small ovate bodied fish named for an early collector of fish from the lake,
John Edmund Sharrock Moore
John Edmund Sharrock Moore ARCS (10 May 1870 – 15 January 1947) was an English biologist, best known for being co-publisher of the term meiosis and leading two expeditions to Tanganyika.
Personal life
Born at Swinshaw near Loveclough, Ross ...
(1870-1947) who was a
cytologist
Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and ...
,
zoologist
Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the Animal, animal kingdom, including the anatomy, structure, embryology, evolution, Biological clas ...
and led an expedition to Lake Tanganyika and who discovered this species.
Juveniles are usually yellow, and adults are dark brown to black in color.
[Borstein, Sam. "Variabilichromis Moori (Boulenger, 1898)." Sam Borstein's Cichlids. N.p., n.d. Web. 20 Nov. 2013. .] It reaches a
total length (TL) of . Currently it is the only member of its
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
. ''V. moorii'' feeds on
algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
,
zooplankton
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
, and
benthic
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...
invertebrates
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
. It is also found in the
aquarium
An aquarium (plural: ''aquariums'' or ''aquaria'') is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aq ...
trade.
Taxonomy
''V. moorii'' is the only member of the genus ''Varibilichromis'', as well as a member of the tribe
Lamprologini
Lamprologini is a tribe of African cichlid fishes. It contains seven genera and nearly 100 species. Over half of the species in this tribe are in the large genus ''Neolamprologus''. Most genera in the tribe are endemic to Lake Tanganyika, but on ...
. It had previously been in the genus ''
Neolamprologus
''Neolamprologus'' is a genus of cichlids endemic to eastern Africa with all but one species, ''Neolamprologus devosi'' from the Malagarasi River, occurring in Lake Tanganyika. It is the largest genus of cichlids in Lake Tanganyika and also the l ...
'', but in 1985, Colombé & Allgayer created the new
monotypic
In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...
genus ''Variabilichromis'' in order to account for a more ancestral
supra-orbital bone structure. This was rejected by
Poll
Poll, polled, or polling may refer to:
Figurative head counts
* Poll, a formal election
** Election verification exit poll, a survey taken to verify election counts
** Polling, voting to make decisions or determine opinions
** Polling places o ...
's (1986) classification, but supported by Stiassny (1997).
Stiassny's classification kept the monotypic genus due to the aforementioned bone structure, as well as the existence of two other characteristics that are rare in the tribe Lamprilogini: their diet includes
filamentous algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular micro ...
, and females have two working
ovaries
The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...
.
[Borstein, Rick. "Variabilochromis Moorii." Variabilochromis Moorii. Greater Chicago Cichlid Association, 11 Aug. 2011. Web. 20 Nov. 2013. .]
Morphology and coloration
![Variabilichromis moorii en aquarium](https://upload.wikimedia.org/wikipedia/commons/2/22/Variabilichromis_moorii_en_aquarium..jpg)
''V. moorii ''exhibit
sexual dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
as adult females tend to be larger than adult males.
Adult males often have longer
pelvic
The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton).
The ...
,
dorsal
Dorsal (from Latin ''dorsum'' ‘back’) may refer to:
* Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism
* Dorsal, positioned on top of an aircraft's fuselage
* Dorsal co ...
, and
anal fin
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...
s than females do.
![Variabilichromis moorii juvénile](https://upload.wikimedia.org/wikipedia/commons/5/54/Variabilichromis_moorii_juv%C3%A9nile..jpg)
Adults are black with electric blue edges on their
tail
The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, r ...
, pectoral, and dorsal fins, whereas juveniles are yellow.
Geographically speaking, they show little variation in color.
Distribution & habitat
''V. moorii'' is only found in the southern parts of
Lake Tanganyika
Lake Tanganyika () is an African Great Lake. It is the second-oldest freshwater lake in the world, the second-largest by volume, and the second-deepest, in all cases after Lake Baikal in Siberia. It is the world's longest freshwater lake. ...
in Africa. They are found in rocky, relatively shallow areas in the
littoral zone
The littoral zone or nearshore is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely inundated), to coastal areas ...
of the lake (less than 10 meters in depth).
It is one of the most abundant species in this region of the lake.
Breeding and mating
![Variabilichromis oeufs 380](https://upload.wikimedia.org/wikipedia/commons/d/d5/Variabilichromis_oeufs_380.jpg)
''V. moorii'' is a substrate-breeder, with a male and female pair providing
biparental care to their eggs and the young after they hatch.
This species exhibits serial
monogamy
Monogamy ( ) is a form of dyadic relationship in which an individual has only one partner during their lifetime. Alternately, only one partner at any one time (serial monogamy) — as compared to the various forms of non-monogamy (e.g., polyga ...
, where a male and female are monogamous for at least one spawning cycle. A female lays 200–500 eggs per
brood
Brood may refer to:
Nature
* Brood, a collective term for offspring
* Brooding, the incubation of bird eggs by their parents
* Bee brood, the young of a beehive
* Individual broods of North American Periodical Cicadas:
** Brood X, the largest bro ...
, usually under an overhanging rock or within a rock crevice.
Eggs take at least 3 days to hatch and newly hatched larvae are approximately (TL). They remain in the larval stage for 4 to 5 days, attached to the substrate by their head glands. They then develop into free-swimming
fry and swim in a tight school close to the spawning site. Parents may defend the brood for up to 100 days, which is when fry reach about (TL).
Lunar synchronicity in spawning
Spawning cycles in ''V. moorii'' correspond to the lunar cycle, with egg-laying taking place just before the full moon. This lunar-related reproductive periodicity is rare in freshwater organisms and far more common in organisms in marine environments. This periodicity probably evolved to decrease risk of
predation
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...
when the fry are in their most vulnerable stages (as
eggs and larvae), since the moon is at its brightest and the parents can best defend against
nocturnal
Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite.
Nocturnal creatures generally have highly developed sens ...
fry-eating fish. Such nocturnal predators also tend to
avoid or move away from light and thus hunt less during the full moon. This lunar synchronicity confers greater benefit to ''V. moorii'' compared to other freshwater fish species because of ''V. moorii''’s location in the
tropical zone
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referred to ...
where the moonlight is more intense (since it is more perpendicular to the surface) and ''V. moorii'' tend to live in shallow waters that are easily penetrated by moonlight.
Parasitic spawning and multiple paternity
''V. moorii'' shows
social but not genetic monogamy. Breeding adults spawn according to the
lunar cycle
Concerning the lunar month of ~29.53 days as viewed from Earth, the lunar phase or Moon phase is the shape of the Moon's directly sunlit portion, which can be expressed quantitatively using areas or angles, or described qualitatively using the t ...
and thus
spawn synchronously (see ''Lunar synchronicity in spawning)''. This allows males to spawn on eggs that do not belong to the female he is mated to (also known as parasitic spawning).
All offspring within a single brood share the same mother but not the same father. A study found that broods are almost always sired by multiple males (at least two but sometimes more than ten), a rate which is exceptionally high compared to other multiply mating fish. The male mated to the mother of the brood will invest significant resources to protect the territory and brood even though he did not sire the majority of the fry. The female is related to the entire brood and the male is related only to a fraction of the brood, so the female would be expected to provide more care than the male. However, there is no great difference in male parental care and female parental care.
Defending territory
''V. moorii'' have individual territories for feeding and territories shared with a mate when spawning and raising their young.
Feeding territories
Individual ''V. moorii'' territories are defended for their food resources and territory owners will defend more aggressively against individuals of species with similar diets, including
conspecifics
Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species.
Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organis ...
. ''V. moorii'' feeding territories in deeper areas are larger than those in shallow areas. Population density decreases with greater depth, so a large territory in a deep area can be more easily defended from competitors than a similarly sized territory in a shallow area. There is also lower algal productivity at greater depths because less light is available for photosynthesis, which also contributes to larger territories with increasing depth.
Breeding territories
''V. moorii'' parents have a total defended territory that is several times larger than the core area (which is the area where the parents spend most of their time and where the brood is located). The male and female divide the total territory into roughly equal subterritories without much overlap, with the brood located in-between these two subterritories. The subterritory borders are not fixed and will shift throughout the day, depending on the presence of intruders. Upon seeing an intruder, a parent will quickly dart out of the core territory to chase the intruder away.
The parents will attack conspecifics as well as other fish species that enter the territory.
Heterospecific
Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species.
Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organis ...
s are attacked far more often than conspecifics, and include both predators (such as ''
L. elongatus'' and ''
N. fasciatus'') and non-predators (such as ''
O. ventralis'' and ''
T. moorii'' which compete with ''V. moorii'' for food).
''V. moorii'' attack fry-eating fish entering their territory more often if their brood is larger. This is reasonable because the parents have a higher rate of return on
parental investment
Parental investment, in evolutionary biology and evolutionary psychology, is any parental expenditure (e.g. time, energy, resources) that benefits offspring.Clutton-Brock, T.H. 1991. ''The Evolution of Parental Care''. Princeton, NJ: Princeton ...
in a large brood compared to a small one. ''V. moorii'' parents attack fry-eating fish more often than other types of fish, meaning they can concentrate their defensive efforts on the fish most dangerous to their fry. Rates of attack do not decrease significantly even as fry get older and larger because the environment has high predation pressure and even older fry will be quickly eaten without defense from the parents.
Exploitation by ''Neolamprologus mustax''
''V. moorii'' parents typically chase away other fish that enter their territory, but they are less aggressive toward members of the cichlid species ''
N. mustax'' which are yellow in color, resembling ''V. moorii'' fry. ''N. mustax'' is the only other cichlid in'' V. moorii''
's habitat which is yellow. Experiments have shown that ''V. moorii'' are more aggressive toward black fish compared to yellow fish of the same size and shape.
''N. mustax'' feed on benthic invertebrates and preferentially feed in'' V. moorii'' territories where benthic invertebrates much more abundant. This is due to ''V. moorii'' parents driving away other zoobenthivorous fish species, which often also prey on ''V. moorii'' fry.
Unlike other zoobenthivorous fish, ''N. mustax'' do not prey on ''V. moorii'' fry; if they did they would certainly be driven away.
References
{{Taxonbar, from=Q134843
Lamprologini
Fish of Lake Tanganyika
Monotypic fish genera
Taxa named by George Albert Boulenger
Fish described in 1898
Taxobox binomials not recognized by IUCN