Friday,21 September 2018, 1 : 35 PM

Introduction to Cichlids

Geophagus Iporangensis
Geophagus Iporangensis
Image Credit: Hayath Mohammad

Introduction



Cichlids are a large group of fish which are very popular in both aquarium community as well as food industry.
Cichlids are placed in family Cichlidae.
A full taxonomic classification is given below.

  • Kingdom : Animalia
  • Phylum : Chordata
  • Class : Actinopterygii
  • Order : Perciformes
  • Suborder : Labroidei
  • Family : Cichlidae

The Cichlid family is both large and diverse.
At least 1,300 species have been scientifically described, making it one of the largest vertebrate families.
New species are discovered annually, and many species remain un-described.
The actual number of species is therefore unknown, with estimates varying between 1,300 and 3,000.


Physical Description



Cichlid Comaprision

Cichlids Boulengerochromis and Apistogramma(not to scale)
(Image Credits: Wikipedia and Leif Apisto Johansen)



Cichlids span a wide range of body sizes, from species as small as 1 inch belonging to genus apistogramma to much larger species approaching 36 inches belonging to genus Boulengerochromis .(Image above)

Cichlids exhibit a great diversity of body shapes, ranging from strongly laterally compressed fish belonging to genus like Altolamprologus, Pterophyllum , and Symphysodon to fish that are cylindrical and highly elongate like those belonging to genus Julidochromis, Teleogramma, Teleocichla etc.



CichlidSizeComaprision

Cichlids Discus and Julidochromis(not to scale)
(Image Credits: Guerin Nicolasvia(via Wikipedia) and Hayath Mohammad)



Generally, however, cichlids tend to be of medium size, ovate in shape and slightly laterally compressed , and generally similar to the North American sunfishes in morphology, behavior, and ecology.

The family also includes many familiar aquarium fish, including the angelfish, oscars, discus, and a broad group called "africans".
Cichlids have the largest number of endangered species among vertebrate families, most in the haplochromine group.

Cichlids are particularly well known for having evolved rapidly into a large number of closely related but morphologically diverse species within large african lakes, particularly Tanganyika, Victoria, Malawi, and Edward.

Their diversity in the African Great Lakes is important for the study of speciation in evolution.
Many cichlids that have been introduced into waters outside of their natural range have become nuisances, such as tilapia in the USA and India.


Anatomy and appearance

Cichlids share a single key trait:


PharyengalJaws

Oral Jaws and Pharyngeal
(Image Credits:By Gareth J Fraser C. Darrin Hulsey Ryan F Bloomquist Kristine Uyesugi Nancy R Manley J. Todd Streelman doi:10.1371/journal.pbio.1000031.g001 [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons)



The fusion of the lower pharyngeal(throat) bones into a single tooth-bearing structure.
A complex set of muscles allows the upper and lower pharyngeal(throat) bones to be used as a second set of jaws for processing food.
This unique adaptation allows cichlids to have two sets of jaws, one can be called a the "true jaws" (mandibles) and the other "pharyngeal jaws".
Having two jaws allows cichlids to be very efficient feeders and allows them to capture and eat a wide variety of food.
This efficient feeding system is said to be major factor in their amazing diversity.

Following features distinguish cichlids rom the other fish are:

  • A nostril on each side of head.
  • The lateral line is interrupted in most species.
  • Scales in lateral lines may be over 100, usually 20-50.
  • Dorsal fin usually have 7-25 spines and 5-30 soft rays.
  • Spines in anal fin 3-15 (generally 3)
  • Soft rays 4-15 (a few with 30).
  • Sub ocular shelf absent.
  • A distinctively shaped otolith.
  • The small intestine's left-side exit from the stomach instead of its right side as in other fish.


Taxonomy

The family Cichlidae was first described by Heckel in 1840, based on the Natterer collection from Brazil (illustrations in Riedl-Dorn, 2000).
Another early major classification is by Jardine in 1843, based on the Schomburgk collection from Guyana, Brazil and Venezuela (Kullander & Stawikowski, 1997a-b, for identifications).
Steindachner (1875) worked on the Thayer expedition collection of Amazonian cichlids, but did not add much beyond the work of Heckel.

In 1868 Günther described and illustrated a large part of the Central American cichlid fauna, followed by Regan (1906-1908).
Pellegrin (1904) revised the family with diagnoses of all genera and species known to him.
Much of Pellegrin’s efforts with the Neo tropical taxa were improved upon by Regan’s series of generic revisions in the next two years (Regan, 1905-1906), which remained the platform for all Neo tropical cichlid systematics until the 1980s.

The first modern phylogenetic revision of the Neo tropical cichlids was presented by Cichocki (1976), and most recently Kullander (1988) and Farias et al. (1999) have provided phylogenetic hypotheses based on morphology and molecular data respectively.
In 1988 Kullander provided a detailed classification right down to tribe. Scientific general reviews of the family are provided by Keenleyside (1991) and Barlow (2000).

Kullander (1998) recognizes eight subfamilies of cichlids:

  • Astronotinae
  • Cichlasomatinae
  • Cichlinae
  • Etroplinae
  • Geophaginae
  • Heterochromidinae
  • Pseudocrenilabrinae
  • Retroculinae

Classification of fish between various genus, tribes, families etc. is done on the basis of morphology and genetic analysis.
Earlier classification were based on dentition, however later on it was discovered that teeth shape etc, changes with age and wear tear and is not a very reliable source for classification.
It is now a common consensus that the whole family of cichlids has descended from a common ancestor, or that it is monophyletic.


Range and habitat

Cichlids are the most species-rich non-Ostariophysan family in freshwaters worldwide.
They are most diverse in Africa and South America.
It is estimated that Africa alone hosts at least 1,600 species.
Central America offers approximately 120 species, as far north as the Rio Grande in southern Texas.
Madagascar has its own distinctive species, only distantly related to those on the African mainland.

Endemic cichlids are largely absent in Asia, except for four species in the Jordan Valley in the Middle East , one in Iran, and three in India and Sri Lanka.

Cichlids are less commonly found in brackish and saltwater habitats, though many species tolerate brackish water for extended periods;
Cichlasoma urophthalmus, for example, is equally at home in freshwater marshes and mangrove swamps, and lives and breeds in saltwater environments such as the mangrove belts around barrier islands.

Several species of Tilapia, Sarotherodon, and Oreochromis are euryhaline can tolerate water with high salinity) and can disperse along brackish coastlines between rivers.
Only a few cichlids, however, inhabit primarily brackish or salt water, most notably Etroplus maculatus, Etroplus suratensis, and Sarotherodon melanotheron.
Cichlids have not reached any oceanic island and have a predominantly Gondwanan distribution. That is they are mostly found in Africa, North America, South America, Australia, Indian subcontinent, Arabian peninsula etc.



Feeding



Cichlids are very adaptive feeders, and having two set of teeth allows them to specialize in niches to feed.
Cichlids exhibit a wide range of feeding strategies and adaptations.



EtroplusSuratensis

Etroplus suratensis primarily herbivore
(Image Credits:Beta M)



Some Cichlids are primarily herbivores feeding on algae (e.g. Petrochromis) and plants (e.g. Etroplus suratensis).
Small animals, particularly invertebrates, are only a minor part of their diet.

Some cichlids are detritivores and eat all types of organic material; among these species are the tilapiines of the genera Oreochromis, Sarotherodon, and Tilapia.

Other cichlids are predatory and eat little or no plant matter.
These include generalists that catch a variety of small animals, including other fishes and insect larvae (e.g. Pterophyllum), as well as variety of specialists.

Some cichlids have extremely specialized diet, for example Trematocranus is a specialized snail-eater, while Pungu maclareni feeds on sponges.
A number of cichlids feed on other fish, either entirely or in part.
Crenicichla are stealth-predators that lunge from concealment at passing small fish, while Rhamphochromis are open water pursuit predators that chase down their prey.

Crencichlapuncata

Crenicichla punctata a stealth predator
(Image Credits:Wikipedia)



Paedophagous cichlids such as the Caprichromis species eat other species' eggs or young, in some cases ramming the heads of mouth brooding species to force them to disgorge their young.

Among the more unusual feeding strategies are those of Corematodus, Docimodus evelynae, P lecodus, Perissodus, and Genyochromis spp., which feed on scales and fins of other fishes,
a behavior known as lepidophagy, along with the death-mimicking behavior of Nimbochromis and Parachromis species, which lay motionless, luring small fish to their side prior to ambush.

This variety of feeding styles has helped cichlids to inhabit similarly varied habitats.
Its pharyngeal teeth (teeth in the throat) afford cichlids so many "niche" feeding strategies, because the jaws pick and hold food, while the pharyngeal teeth crush the prey.


Reproduction-Mating


Like most fish cichlids lay eggs and young emerge from the eggs.
Mating behaviors of cichlids is both monogamous as well as polygamous.
The mating system of a given cichlid species is not consistently associated with its brooding system.
For example, although most monogamous cichlids are not mouth brooders, Chromidotilapia, Gymnogeophagus, Spathodus and Tanganicodus are all monogamous mouth brooders.
In contrast, numerous open or cave spawning cichlids are polygamous; examples include Apistogramma, Lamprologus, Nannacara and Pelvicachromis.


Brood care

All cichlid species show some form of parental care for both eggs and larvae, often nurturing free-swimming young until they are weeks or months old.
Communal parental care is observed in many cichlid families.
In this it is observed that multiple monogamous pairs care for a mixed school of young.
Some examples are Amphilophus citrinellus, Etroplus suratensis, and Tilapia rendalli.
In some cases not only adults but also older juveniles participate in protecting the young.
This has been observed in Neolamprologus brichardi.

Several cichlids feed their young with a skin secretion from mucous glands. For example discus (Symphysodon spp.), some Amphilophus species, Etroplus and Uaru.

Parental care falls into one of four categories:

  • Substrate or open brooders,
  • Secretive cave brooders (also known as guarding speleophils)
  • Ovophile mouth brooders.
  • Larvophile mouth brooders.


Substrate/Open brooding



angelfish

Pterophyllum sp.-Angel fish-An open brooder
(Image Credits:Wikipedia)



Open or substrate brooding cichlids lay their eggs in the open, on rocks, leaves, or logs.
Examples of open brooding cichlids include Pterophyllum, Symphysodon spp, and Anomalochromis thomasi.
Male and female parents usually engage in differing brooding roles.
Most commonly, the male patrols the pair's territory and repels intruders, while females fan water over the eggs, removing the infertile and leading the fry while foraging.
However, both sexes are able to perform the full range of parenting behaviors.


Cave brooding



Pelvichromis

Pelvicachromis taeniatus-A Cave brooder
(Image Credits:Wikipedia)



Secretive cave spawning cichlids lay their eggs in caves, crevices, holes, or discarded mollusc shells, frequently attaching the eggs to the roof of the chamber.
Examples include Pelvicachromis spp., Archocentrus spp, and Apistogramma spp.

Free-swimming fry and parents communicate in captivity and in the wild.
Frequently this communication is based on body movements, such as shaking and pelvic fin flicking.
In addition, open and cave brooding parents assist in finding food resources for their fry.
Multiple neo tropical cichlid species perform leaf-turning and fin-digging behaviors.


Ovophile mouth brooding



Cynotilapia

Cynotilapia frontosa-A Mouth brooder(enlarge to see the babies in the mouth
(Image Credits:Wikipedia)



Ovophile mouth brooders incubate their eggs in their mouths as soon as they are laid, and frequently mouth brood free-swimming fry for several weeks.
Examples include many Great Rift Valley lake cichlids(Lake Malawi, Lake Tanganyika and Lake Victoria) endemics, e.g.: Maylandia, Pseudotropheus, and Tropheus, along with some South American cichlids such as Geophagus steindachneri.


Larvophile mouth brooding

Larvophile mouth brooders lay eggs in the open or in a cave and take the hatched larvae into the mouth.
Examples include some variants of Geophagus altifrons, Aequidens, Gymnogeophagus, and Satanoperca.
Mouth brooders, whether of eggs or larvae, are predominantly females.
Exceptions that also involve the males include eretmodine cichlids (genera Spathodus, Eretmodus, and Tanganicodus), some Sarotherodon species, Chromidotilapia guntheri, and some Aequidens species.