MADAGASCAR COCKROACH: CHARACTERISTICS, HABITAT, FEEDING - BIOLOGY - 2024

The Madagascar cockroach (Gromphadorhina portentosa) is a Blattodea insect of the Blaberidae family that is characterized by the lack of wings in both sexes and by its large size, since males can reach up to 9 cm in length (7.6 cm according to some authors), being one of the largest cockroach species that exists.

As its name suggests, this cockroach is native to the island of Madagascar and in its natural environment it lives under decaying logs and other plant debris. Currently it can be obtained practically anywhere in the world as it is used as a pet, however, it is not an invasive species.

Madagascar cockroaches Gromphadorhina portentosa. Taken and edited from: Dezidor.

It is dioecious or gonochoric, that is, it has separate males and females. Copulation occurs after a courtship process, fertilization is internal and the female produces several eggs that are grouped in a single envelope called the ootheca, which she maintains in her abdomen until hatching.

It is an omnivorous species that feeds mainly on fruits and other plant materials. As pets they are kept very well fed with dry processed food for dogs, cats, fish, birds, monkeys and even rats. Some authors point out that they are saprozoic (they feed on dead or decomposing organisms).

characteristics

The Madagascar cockroach has an elongated and oval body, protected by a strong cuticle, black and light brown in color. Both males and females lack wings. The cephalic region is partially protected by a thick pronotum.

There is a marked sexual dimorphism, with larger males, thick and setosus antennae and showing tuberculiform projections on the pronotum similar to horns. The female for its part is smaller, with filiform antennae and with less pronounced projections of the pronotum.

It is one of the largest species of cockroaches existing today, with a male that measures about 7 cm, but according to some authors it can measure 9 cm in length and weigh about 15 gr.

It has thick legs, armed with thorns and very adapted to climbing, and can even do so in polished glass. These legs also allow you to dig into the substrate.

Gromphadorhina portentosa is also known as a hissing cockroach because it is capable of emitting a hissing sound by forcing air through the spiracles located on its abdomen.

The hiss can be of two types, alarm (disturbance hiss) or combat (fighting hiss). Any cockroach of this species can emit the first of them from the fourth stage of life, while only adult males can emit the combat hiss.

Taxonomy

The Madagascar cockroach is a Blattodea (order) insect of the Blaberidae family located within the Gromphadorhinini tribe. This tribe comprises about 20 species in six genera of giant cockroaches, all of them hissing and all inhabitants of Madagascar, except one that lives on the island of Europa, near Madagascar.

The genus Gromphadorhina was erected by Brunner von Wattenwyl in 1865 and currently contains 4 species of giant Madagascar cockroaches, all of which are widely used as pets, the most popular of which, Gromphadorhina portentosa, was described by Schaum in 1583.

Habitat and distribution

Gromphadorhina portentosa lives in tropical rainforests, generally hiding under fallen logs and other plant debris during the daytime, and at night they roam the forest floor. It is also frequent to observe it inhabiting garbage dumps.

The natural distribution of this species is restricted to the island of Madagascar from where it is endemic. At present it is widely distributed worldwide as a pet animal, however to date it is not considered an invasive species and it has no confirmed settled populations outside its place of origin.

Reproduction

Madagascar cockroach female. Taken and edited from: Almabes at English Wikipedia.

The giant cockroach of Madagascar is a gonochoric or dioecious species, that is to say that in this species males and females appear separately, with sexual dimorphism.

The males differ from the female by their larger size, by having strongly setose antennae (filiform in females) and by the presence of a thicker and more ornate pronotum with more developed tubers.

Fertilization is internal, copulation takes place after a courtship stage, which apparently begins without the participation of pheromones. Courtship begins with a long period of touching between males and females using the antennae, after which the male begins to circle the female while continuing to touch her.

For copulation, male and female are placed in opposite position, bringing their abdomens together. The male then begins to rhythmically move his abdomen from side to side, allowing his phallomeres to emerge. The copulation lasts a few seconds. In the following video you can see how they mate:

Once the male deposits his spermatophore in the female's spermatheca, the female will be able to mature successive groups of ovules, which will be fertilized by the sperm contained in the spermatophores, so the female will not need to copulate again in order to continue having offspring.

In each reproductive season the female produces between 15 and 40 eggs. These ovules are fertilized and the eggs produced are protected by an envelope called the ootheca. The female does not immediately deposit the ootheca, but conserves it in an incubator chamber inside her abdomen until the time the juveniles hatch.

Lifecycle

The life cycle of the Madagascar cockroach begins when the nymph leaves the ootheca and the interior of the mother. This is one of the few species of ovoviviparous cockroaches in existence. The nymph is an externally similar stage to the adult, only much smaller and sexually immature.

The nymph must go through six molts, in a period that can last between six and seven months, to reach sexual maturity. Once sexual maturity is reached, the giant cockroach can reproduce. The female needs to copulate only once in her life to have a supply of sperm to fertilize all the eggs she will produce.

After fertilization of the ovules to produce the eggs, the female places between 15 and 40 eggs in a unique protective structure, called the ootheca. This retains the ootheca in an incubation chamber inside.

After a gestation period of approximately two months, the nymphs have developed and the rupture of the ootheca occurs and the nymphs are released from this structure and immediately the release of the interior of the mother as well.

The longevity of the species has been estimated at five years in captivity and slightly less in the wild.

Feeding

According to some authors, the Madagascar cockroach is a saprozoic species that feeds on decomposing organic material, both of animal and plant origin. Other authors consider it as an opportunistic omnivore, capable of feeding on practically anything.

In their natural environment, their main food is made up of the fallen fruits on the forest floor. They can also feed on small animals, both living and dead.

In captive conditions they can feed on both fresh plant material and dry food prepared for different types of animals, such as lizards, birds, dogs, cats, among others.

Applications

As pets

Gromphadorhina portentosa is used as a pet in various parts of the world. Its popularity as a pet was increased by the appearance of specimens of the species in various Hollywood films, such as Men in Black (Men in Black).

This cockroach is very well adapted to captive breeding. However, special attention must be paid to the enclosure where it will be kept, as it is a very good climber and can even climb on polished glass surfaces. Due to this, these enclosures must be able to be closed properly, but allow the passage of air.

Another important aspect to pay attention to is the period immediately after the molt. At that time the exoskeleton is very soft and therefore should be avoided handling them until it has hardened.

As a food supplement for animals

Gromphadorhina portentosa has been evaluated as a protein source to feed aquaculture animals (fish, shrimp), demonstrating that the meal obtained from this species contains a better profile of essential amino acids than that from soy, as well as a higher level of crude protein.

In addition, the digestibility of the proteins present in Gromphadorhina portentosa flour is higher than that of soybean flour. This, coupled with the fact that the Madagascar cockroach is easy to grow and that this crop has a low ecological footprint, make the species a strong potential candidate for the production of aquaculture feeds.

Due to its high protein content, Gromphadorhina portentosa has also been suggested to be used in the manufacture of food for dogs and rabbits, being a way to increase the nutritional value of these foods.

Birth of cockroaches Gromphadorhina portentosa. Taken and edited from: Matt Reinbold.

In the human food industry

Researchers have evaluated the flour of Gromphadorhina portentosa in the manufacture of cheeses, showing as a result that by increasing the content of cockroach flour, the clotting time of the cheese decreases.

With the increase in flour, factors such as hardness, adhesiveness and elasticity of the cheese are also positively affected. On the other hand, the resilience, cohesiveness and rubberiness of the product are negatively affected by said increase.

References

1. RH Barth, Jr (1968). The mating behavior of Gromphadorhina portentosa (Schaum) (Blattaria, Blaberoidea, Blaberidae, Oxyhaloinae) an anomalous pattern for a cockroach. Psyche.
2. Madagascar hissing cockroach. On Wikipedia. Recovered from: en.wikipedia.org.
3. P. Mulder (nd). Madagascar Hissing Cockroaches: Information and Care. Oklahoma Cooperative Extension Service.
4. Giant Madagascar Cockroach: Reproduction, Care, Habitat and Much More. Recovered from: hablemosdeinsectos.com.
5. P. Echegaray-Vallejo, JA Gómez-Salazar, CA García-Munguía, AM García-Munguía, AI Mireles-Arriaga (2019). Effect of the addition of Gromphadorhina portentosa on the TPA of milk coagulation. Research and Development in Food Science and Technology.
6. Whistling cockroach. At Bioparc Valencia. Recovered from: bioparcvalencia.es.
7. Gromphadorhina. On Wikipedia. Recovered from: en.wikipedia.org.