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Spawning strategies in cichlids part 4 – Substrate brooders

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Last updated on 14-Apr-2022

Juan Miguel Artigas Azas,

Classification: Behavior.

" Unlike the livebearing fishes, where females produce eggs that are internally fertilized, giving birth to fully formed and self-reliant progeny, all species of cichlids use external fertilization, which may seem like a more primitive technique, but it has so far supported their evolutionary success. In cichlids, unlike in other fishes such as characins which don’t provide post spawn care to their progeny, egg care has evolved into a high degree of specialization "

In the present article I deal with the basal behavior of the open substrate spawners, from the more primitive to the more advanced techniques, and in a subsequent article I will deal with the more advanced mouth-brooding techniques in cichlids.

Where to place the eggs?

Once a territory has been established by a cichlid, a place has to be chosen inside it where to place the eggs, ideally this means a hard surface where eggs can be attached and maintained in optimum conditions for their development, which includes easy access for protection, oxygenation, and sanitation. This is an important task since eggs are very valuable to the parents as they represent a huge investment in energy and time. For the predators, eggs represent a very nutritious food.

For this reason cichlid pairs, even when they spawn in the open, always look for a place where at least partial protection is provided by the environment, an effort often challenged by available places and competition. A rock or piece of wood that offer a vertical surface helps, as the angle in which the eggs are exposed to predator attacks is reduced, plus the accumulation of debris on them is less on vertical surfaces. The place, however, should also allow the parents to maneuver and protect the area and not liable to be surprised by predators.

Male from Laguna Xiloá Parachromis dovii spawns in the open since pairs have the power to protect their spawning site. Photo by Willem Heijns. (16-Jul-2006). determiner Willem Heijns

Some brute beast species, such as Middle American Parachromis, spawn in the open since they have the power to protect their spawning site. Nonetheless, their eggs number in the thousands to compensate for massive loses, as it appears, their sheer strength and aggressiveness alone does not guarantee their survival. Smaller, more agile fish such as Astyanax tetra species, normally a prey item for Parachromis, may well outmaneuver them and get to their eggs or fry before they can defend them. For a pair of cichlids to be able to successfully defend their eggs from predators like Astyanax, which normally attacks in large numbers, a perfect defense coordination is needed.

Male in the aquarium Andinoacara coeruleopunctata is known to place their eggs on movable surfaces, like sunken leaves. Photo by Matthijs Meindertsma. (14-Apr-2009). determiner Willem Heijns

Over the course of the years I have learnt that to observe and photograph breeding cichlids in nature I need to be slow, patient, and give the parents the opportunity to get accustomed to me and not see me as a threat to their eggs or them. This normally works (although not always with all species) and after they recognize that I am not a danger they allow me to stay close and ignore me. However, if instead I suddenly move in without giving them the opportunity to evaluate me, it can spell disaster since the pair coordination could be lost, and even a slight loss of coordination is easily perceived by stalking Astyanax, which would immediately make use of the opportunity and attack eggs or fry. Once a coordinated massive attack has started, there is nothing that can stop it and consequently most — if not all — of the eggs or fry will be lost in seconds.

Pair spawning in Chocolhaito River Theraps irregularis spawns in the shallow areas of fast flowing rivers, with eggs strongly attached to rocks exposed to the current. Photo by Juan Miguel Artigas Azas. (10-Jan-2004). determiner Juan Miguel Artigas Azas

In the strong currents of the Usumacinta river system (and Sarstoon River in Guatemala), Theraps irregularis spawns in the shallow areas of fast flowing rivers, with eggs strongly attached to rocks exposed to the current. In order to deter predators the pairs are very active in the protection of the spawn, and they count with an evolutionary advantage, i.e. the camouflage of the eggs. Even at a short distance it is very hard to spot them, since they are almost completely translucent and blend perfectly well with the rock, making protection a bit easier for the parents.

The four Paraneetroplus species, all living in Mexico, take this camouflage protection to a more extreme level by not clearly delimiting the spawning site, but just creating a shallow depression where they scatter their translucent eggs on the gravel/pebbles in a larger than usual area, making them almost impossible to see, even if you know they are there. It is only the presence of the pair, who patrol the territory in a very wide circle, that make you aware of a potential spawn. It takes very detailed observation to actually find them.

Some species, such as Andinoacara coeruleopunctata and A. pulcher, are known to place their eggs on movable surfaces, like sunken leaves (Barlow, 2002), which they can, if necessary, carry with their mouths to areas with more suitable conditions, like in cases of perceived danger or habitat change (e.g. the swelling of a stream by recent rains). In the former species the leaves are even used during courtship by females as a token of readiness to spawn, carrying them in their mouths when approaching a desirable male.

Male in the aquarium Andinoacara coeruleopunctata is known to place their eggs on movable surfaces, like sunken leaves. Photo by Matthijs Meindertsma. (14-Apr-2009). determiner Willem Heijns

A more advanced case of open area spawning involves the use of caves to place the eggs and wrigglers. Caves protect the eggs by hiding them and covering angles of potential attack. Some species use caves already in place that just need to be cleaned. A simple example is Herichthys pantostictus in the Panuco river drainage, which spawn in rocky areas of streams. I have observed this species spawning in covered areas among two rocks which form a cave-like structure, although they would also spawn in the open if necessary. Other species such as Herichthys pame, H. bartoni, and H. minckleyi actually build caves for spawning by digging at the base of rocks. According to my observations, the digging is mostly done by females which grab mouthfuls of soft substrate to spit them on the nest’s surroundings. H. bartoni excavate deep, narrow, horizontal holes in the banks of the springs which they inhabit.

Cryptoheros species in Middle America also dig caves for spawning, the generic name Cryptoheros is actually dedicated to this behavior of spawning in enclosed spaces (Crypto = hidden, from Greek and Heros being a genus of South American cichlids).

An amazing cave digging technique is described by Ron Coleman for Hypsophrys nicaraguensis in Costa Rica (Barlow, 2002; personal communication), a species which digs up long tunnels in muddy bank areas using the body as a drill. I was able to observe a spawning area of this species in the Same River (a tributary of the San Juan drainage) in Costa Rica, with a breeding area in which there were a multitude of deep tunnels (longer than the fish) in a muddy river bank.

Individual in the aquarium Hypsophrys nicaraguensis digs up long tunnels in muddy bank areas to place their non-adhesive eggs. Photo by Brian Traas. determiner Juan Miguel Artigas Azas

Cave digging is not exclusive to Middle America since other species, such as ‘Lamprologus’ lemairii in Lake Tanganyika, excavate caves in the bottom of the lake to spawn. In this and some other Lake Tanganyika species the cave can only accommodate the female, so the eggs have to be fertilized by the male from the outside.

Other small cichlids in Lake Tanganyika, for example ‘Lamprologus’ ocellatus and several other species, use prefabricated caves in the form of empty snail shells as a home and nest. This and several other Tanganyikan cichlid examples are beautifully described in Ad Konings’ “Tanganyika cichlids in their natural habitat, 4th edition” and in specialized profiles in this site.

Egg attachment

Eggs are anchored by cichlids to a surface by small adhesive threads. These threads have evolved several configurations and provide a very strong bond. The threads for example have to be strong enough to anchor eggs of Theraps irregularis and Paraneetroplus species in the strong water currents where they are laid in the open. In muddy areas, where no hard surface is usually found, any solid structure for egg attachment is used. While observing Petenia splendida breeding in the White Water Lagoon in Belize, George Barlow (Barlow, 2002) observed how the fish would dig at the base of water lilies in muddy areas to expose the roots that served as a spawning surface. He also observed Vieja maculicauda in Lake Gatun in Panama digging burrows in muddy areas, which exposed roots that served to hold the eggs in an otherwise soft substrate. The threads stemming from the eggs of these aforementioned species (and many others) are short and found over the entire egg surface.

Adult in the aquarium Pseudoetroplus maculatus produces eggs with threads that protrude from one end only. A spawn of this species typically consists of eggs that sway from one side to the other with the water movement. Photo by Philippe Burnel. determiner Philippe Burnel

Pseudoetroplus maculatus in Sri Lanka produces greenish, oblong eggs with threads that protrude from one end only. A spawn of this species typically consists of eggs that sway from one side to the other with the water movement.

The primitive cichlid Paratilapia polleni from Madagascar produces spherical eggs with threads long enough such as to entangle each other, creating a three dimensional bunch of eggs with several layers bound together.

At least one substrate brooding species produces eggs which have no threads at all: Hypsophrys nicaraguensis from the San Juan River system in Middle America. Since this particular species deposits eggs at the bottom of a mud or clay tunnel there is no need to attach to anything.

In most substrate brooding cichlid species eggs are attached to surfaces in a perfectly orderly way forming impeccable rows of equally separated eggs. Cichlids can do this without looking by using their pelvic fins as guides, which sense the position of already deposited eggs (Ostrander et al., 1985).

Eggs fertilization

Pair at Namansi ‘Lamprologus’ callipterus males cannot fit in the shell nest, so the sperm has to live long enough to reach the eggs. Photo by Juan Miguel Artigas Azas. (16-Sep-2010). determiner Ad Konings

Once deposited, eggs need to be fertilized. Sperm in cichlids have a very short lifespan, with a typical viability in water of about 30 seconds (Barlow, 2002). This short life is, however, more than enough since, in most cases, a female deposits short rows of eggs and then makes space so the male can position himself above the eggs and fertilize them. The viability of the sperm is long enough for males of ‘Lamprologus’ callipterus, who cannot fit in the shell in which the female deposits the eggs, to release the sperm from the outside.

Most cichlid aquarists who have used the “incomplete divider method” developed in the mid 1960s by Guy Jordan, a founder of the American Cichlid Association, know that when a large cichlid releases sperm from one side of an incomplete divider in an aquarium, most if not all of the eggs on the other side get fertilized. One should wonder if the sperm also is somehow attracted by the eggs.

How many eggs?

In 1991 Ron Coleman published a paper where he examined the investment made by females in the production of their eggs, and how many of them are produced. He found two very interesting facts: That a female of a given size has a restricted volume where she can accommodate eggs before depositing them and hence the number of eggs produced is directly proportional to the female’s size and that different cichlid species produce eggs of different sizes. Egg size ideally has to be the smallest possible so to be able to produce the maximum number of fry, but then the environment counterbalances by not allowing enough fry to survive if they do not have a given size.

After the publication of his paper, Coleman established in 1996 the Cichlid Egg Project, intended to request aquarists for eggs of different cichlid species to be measured and tabulated. He received many samples and found that for example lotic species, which spawn and raise their fry in fast flowing water, produce larger (but fewer) eggs than lentic species, which raise their fry in slow flowing or stagnant water. The hypothesis is that fry have to swim in the water current once the eggs hatch and they have to be large and strong enough to cope with it. Examples are Tomocichla tuba, a lotic species, with eggs 3.1 mm long versus eggs of Parachromis managuensis, a lentic species, which have a length of 2.1 mm. T. tuba eggs are 50% percent longer than those or P. managuensis. It may not seem like much but if we consider the egg’s volume it means that T. tuba produces eggs more than three times bigger than P. managuensis.

Male in the aquarium Tomocichla tuba produces large eggs that are three times as large as those of Parachromis dovii, aimed to produce fry that are large enough to stand in the strong current where they live. Photo by Willem Heijns. (06-Jan-2008). determiner Juan Miguel Artigas Azas

Of course lotic versus lentic is not everything in determining egg size and number as we will see when we talk about mouth-brooding cichlids, which I will do next time.

I want to thank my friend Ad Konings for kindly reviewing this writing. I also want once again to recommend the reading of George Barlow’s “The Cichlid Fishes (Nature's Grand Experiment in Evolution)”; a fantastic guide for learning about cichlids, and which has often served me as guide writing these articles.

References (5):

Citation:

Artigas Azas, Juan Miguel. (April 13, 2022). "Spawning strategies in cichlids part 4 – Substrate brooders". Cichlid Room Companion. Retrieved on May 21, 2022, from: https://cichlidae.com/section.php?id=326.