Gyrinus gibbus

Gyrinus gibbus
Gyrinus gibbus from Cuenca
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Coleoptera
Family:	Gyrinidae
Genus:	Gyrinus
Species:	G. gibbus
Binomial name
Gyrinus gibbus Aubé, 1838
Synonyms
Gyrinus apicalis Sharp, 1877 Gyrinus hypomelas Ochs, 1955

Gyrinus gibbus is a species of aquatic beetle in the family Gyrinidae. It is native to the Neotropics.

Description

The body of Gyrinus gibbus has an oval, convex shape and is between 4,5 mm and 6.0 mm long. It is coloured black or dark brown with exception of the elytral margin, which is often coloured in a reddish or yellow tone. The elytra are non-uniformly reticulated and vary from a polished appearance in the middle regions of the elytra to a bronze-metallic appearance towards the elytral margins. The species shows a high regional variability in body size, convexity, colouration and reticulation of the elytra, with specimens found in the Amazon region being less round and less convex. Like all Gyrinid beetles Gyrinus gibbus has horizontally divided eyes, allowing them to observe the surroundings underwater and on the surface alike. Gyrinus gibbus can be distinguished from the very similar Gyrinus ovatus by the harsher contrast between the polished and metallic areas on the elytra. Furthermore, the elytral apex of Gyrinus gibbus shows a complete border, while in Gyrinus ovatus the epipleural angle bears a spiky denticle.

Feeding habits

Gyrinus gibbus feeds on small insects and spiders.

Distribution

Gyrinus gibbus is distributed in many parts of Latin America, including Argentina, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, Mexico, Paraguay, Peru, Uruguay and Venezuela. Gyrinus gibbus prefers stagnant or slow flowing waters. In Venezuela the species seems to be strongly associated with streams and river habitats where it occurs in the calmer zones of those water bodies.

Larval Development and Behavior

Recent studies have provided new insights into the larval development and behavior of Gyrinus gibbus. Unlike their adult counterparts, which are known for their distinctive whirligig swimming patterns on the water surface, the larvae exhibit different ecological preferences and behaviors. The larvae are primarily benthic, residing at the bottom of water bodies where they feed on detritus and small invertebrates. This stage is crucial for their development, as it allows them to accumulate the necessary energy reserves for metamorphosis.Larval Gyrinus gibbus undergoes three instars before pupation, each marked by significant morphological changes. During these stages, the larvae develop specialized adaptations, such as elongated bodies and well-developed mandibles, which aid in their predatory lifestyle. The final instar is particularly important as it prepares the larvae for the transition to the pupal stage, where they will undergo metamorphosis into adult beetles.Understanding the larval stages of Gyrinus gibbus not only provides a comprehensive view of their life cycle but also highlights the ecological roles they play in their habitats. These findings contribute to the broader knowledge of gyrinid beetles and their adaptations to aquatic environments.