Gyrinus minutus

Gyrinus minutus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Coleoptera
Family:	Gyrinidae
Genus:	Gyrinus
Species:	G. minutus
Binomial name
	Gyrinus minutus; Fabricius, 1798

Last updated April 29, 2024

Gyrinus minutus is a species of whirligig beetle in the family Gyrinidae. It is found in North America and Europe.^[1]^[2]^[3]The body is entirely black with a dull appearance due to its microsculpture. G. minutus typically inhabit open edges of larger water bodies like lakes and reservoirs but also reside in sparsely vegetated ponds and slow-flowing river parts. Their swimming abilities are weaker than other gyrinids, and they often disperse in groups when disturbed. Reproduction begins in early spring with mating on water surfaces, followed by egg-laying on aquatic plants. Larvae hatch after a week, growing quickly and reaching maturity within three to four weeks. They are capable of flight, and adults can be found in new locations throughout the summer.^[4]G. minutus lacks volatile production for predator defense or has minimal amounts, likely due to its behavior and habitat preferences. Interestingly, while G. minutus rarely aggregates, it can still respond to alarm signals from other species.^[5]

Geographic Range

North America

In North America, the distribution of G. minutus extends across Canada and Alaska. Its range is primarily limited to the more northern regions of Manitoba and Saskatchewan but is widespread in the Northwest Territories, Yukon Territories, and Alaska. In Alberta, it is found as far south as Edmonton, excluding the Rocky Mountains, where it has been observed at least as far south as Jasper. There are also records of its presence extending south along the Rocky Mountains into Wyoming and Colorado. It’s likely to be discovered in the southern Canadian Rockies and Montana. Throughout its extensive North American range, G. minutus maintains a relatively consistent appearance. Researchers noted no differences between specimens from the Nearctic and Palearctic regions. Male specimens from Wyoming and Colorado tend to be slightly larger than those from Canada, though females show little variation.^[6]

Europe

This species is the only European species of the subgenus Gyrinulus Zaitzev. It is among the most geographically widespread members of its family, with a holarctic distribution. It can be found throughout Canada and North America and is locally common across the northern Palaearctic region, spanning from Spain to northeastern China, including Sakhalin and Hokkaido. In Europe, it predominantly appears in the northern regions, reaching as far as the UK and the Arctic Circle in Fennoscandia. It is absent from the most southerly areas and North Africa. In the UK, its distribution is largely northern, and its population has declined in many southern regions in recent years. Currently, it is primarily found in a few scattered heathland locations in England and Snowdonia in Wales. However, it remains relatively common in Ireland and Scotland, including the Western Isles and Shetland.^[4]

Habitat

Adults are year-round, spending the winter on submerged vegetation. They remain active from February to late autumn, with peak abundance occurring in mid-to-late-summer. Typically, they are found near the open margins of larger water bodies like lakes and reservoirs, but they also inhabit sparsely vegetated ponds in moorlands and slow-flowing parts of rivers. Unlike other gyrinids, their swimming abilities are weak, and their less pronounced gyrations are obvious in the field. When disturbed, they may dive, but a group often disperses by swimming away from the disturbance.^[4]

Life History

The pupal stage is short, and adults emerge within approximately a week. In laboratory settings, the entire life cycle from egg to adult spans about seven weeks. This species can fly, and adults can appear at new locations throughout the summer.^[4]

Genetics

Autosome pair 1 has a relative chromosome length (RCL) of approximately 14.5, and the RCLs decrease relatively evenly across the karyotype to around 5.5 in pairs 7–13. Pair 10 exhibits an obvious secondary constriction. The majority of the autosomes are either metacentric or submetacentric, with pairs 9 and 12 approaching a subacrocentric shape. The X chromosome, which is the longest in the nucleus, has an RCL of about 20 and is metacentric.^[7]

Mating

Reproduction starts in early spring with mating on the water surface, followed by egg-laying on aquatic plants in late spring. Larvae hatch after about one week. These larvae are entirely aquatic and do not need to swim to the surface for oxygen. They are predators that move among underwater plants and hunt for prey. They grow quickly and reach maturity within three to four weeks. Once mature, they leave the water to create a cocoon on the margins of the water or emerging plants.^[4]

Physiology

The body is completely black and appears dull because of its intricate microsculpture. Additionally, in many individuals, there's an obvious metallic bronze sheen on the sides of the wing covers (elytra). The underside and legs are light brown or orange. The pronotum has a narrow, smooth longitudinal central line that stands out against its textured surface, while the mesosternum has a clear, longitudinal median groove.^[4]

Pygidial Glands and Predator Defense

Gyrinid beetles have developed an intricate chemical mechanism that functions both as a means of communication and defense against predators. These beetles have pygidial glands that produce a secretion composed mainly of two parts: a high molecular fraction and a low molecular fraction. The high molecular fraction contains a varying mix of four norsesquiterpenes: gyrinidal, isogyrinidial, gyrinidone, and gyrinidione. These norsesquiterpenes are harmful to fish. Both fish and newts tend to avoid consuming gyrinids when they come into contact with them. The low molecular (volatile) fraction includes alcohols, ketones, and aldehydes, such as 3-methyl-1-butanol and 3-methyl-1-butanal. This fraction is believed to act as an alarm substance within the general signaling or defense system of the gyrinids.^[5]^[8]

The volatile compounds could play a role not only in defense mechanisms but also in their communication system. Isoamyl alcohol is even an irritant for humans. These volatile substances might be effective for communication, as signals transmitted through the air can be rapidly detected across open water surfaces.^[9] The production of pygidial secretion by gyrinids fluctuates throughout the seasons, with one peak occurring in late summer and another in spring.^[5]

Gyrinus minutus either has no volatile fraction or produces it in minimal amounts. Thus, G. minutus does not emit the typical gyrinids scent which is detectable by the human nose. The absence of volatiles seems to be linked to the behavior and habitat preferences of the beetles: G. minutus tends to live alone among emergent vegetation in lakes.^[5]

Researchers have also compared G. minutus with two other species: G. substriatus and G. aeratus, both producing 3-methyl-l-butanal and 3-methyl-l-butanol when irritated. G. substriatus is commonly found in groups in rivers and G. aeratus in lakes (both on the open water surface). In contrast, G. minutus prefers more sheltered habitats like small ponds or the vegetated edges of lakes where the risk of predation from fish is likely reduced compared to the more open regions of lakes.^[9] The evolution of chemical defense and alarm signals appears to be linked to the tendency of these beetles to form groups or aggregations. Though G. minutus rarely occurs in large aggregates, it can still respond to the alarm signals released by other Gyrinus species. Occasionally, individuals of G. minutus may present within groups of a scented species (for example, G. aeratus) on open water surfaces, which are outside their typical habitats. The presence could be seen as a strategy to benefit from the alarm volatiles emitted by individuals of another species. This may help them evade approaching threats, a phenomenon known as Batesian mimicry.^[10]

Researchers have identified three functions of pygidial secretion: (1) preventing microorganisms from attaching to the body, (2) deterring predators, and (3) enhancing the wettability of the chitin. Additionally, researchers demonstrated its alarm function. 'Alarm call' in gyrinid beetles is recognized across different species. The release of alarm volatiles in response to "danger" above the water surface, such as moving objects that cast shadows, suggests that bird predation is a significant threat to gyrinids. Indeed, adult gyrinids have been identified as prey for at least two European bird species: the black tern and the greenshank. The properties of the various pygidial compounds are not fully understood. However, the high molecular weight substances gyrinidal and gyrinidione are the active components responsible for fish rejection.^[10] Gyrinids with both norsesquiterpenes and volatiles are more effectively protected against fish predation compared to those with only norsesquiterpenes. Besides, it was shown that fish are more reluctant to eat a gyrinid containing volatiles. It was observed that rainbow trout usually performed oral flushing on captured gyrinid beetles but spent more effort flushing if the beetle was to be consumed. They did not flush prey that they found palatable, indicating that oral flushing serves as a method to eliminate harmful chemicals from potential prey. However, experienced fish were quicker to reject gyrinids containing volatiles compared to those without. If it’s too hard to remove the chemicals, the fish would not spend energy on flushing; instead, they immediately spit out the prey. This suggests that volatiles enhance the distastefulness of gyrinids.^[5]

An outstanding question for future research is whether G. minutus has lost the capability to produce volatile alarm substances, or if it never possessed this ability. The absence of production in G. minutus could potentially indicate an original state. Furthermore, considering the small size of G. minutus, the production of volatiles may be less advantageous, as its smaller size likely makes it a less appealing prey for vertebrates.^[10]

Related Research Articles

Beetles are insects that form the order Coleoptera, in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 described species, is the largest of all orders, constituting almost 40% of described insects and 25% of all known animal species; new species are discovered frequently, with estimates suggesting that there are between 0.9 and 2.1 million total species. Found in almost every habitat except the sea and the polar regions, they interact with their ecosystems in several ways: beetles often feed on plants and fungi, break down animal and plant debris, and eat other invertebrates. Some species are serious agricultural pests, such as the Colorado potato beetle, while others such as Coccinellidae eat aphids, scale insects, thrips, and other plant-sucking insects that damage crops. Some others also have unique characteristics, such as the common eastern firefly, which uses a light-emitting organ for mating and communication purposes

The whirligig beetles are water beetles, comprising the family Gyrinidae that usually swim on the surface of the water if undisturbed, though they swim underwater when threatened. They get their common name from their habit of swimming rapidly in circles when alarmed, and are also notable for their divided eyes which are believed to enable them to see both above and below water. The family includes some 700 extant species worldwide, in 15 genera, plus a few fossil species. Most species are very similar in general appearance, though they vary in size from perhaps 3 mm to 18 mm in length. They tend to be flattened and rounded in cross section, in plain view as seen from above, and in longitudinal section. In fact their shape is a good first approximation to an ellipsoid, with legs and other appendages fitting closely into a streamlined surface. Whirligig beetles belong to the beetle suborder Adephaga, which also includes ground beetles and diving beetles.

A water beetle is a generalized name for any beetle that is adapted to living in water at any point in its life cycle. Most water beetles can only live in fresh water, with a few marine species that live in the intertidal zone or littoral zone. There are approximately 2000 species of true water beetles native to lands throughout the world.

The Adephaga are a suborder of beetles, and with more than 40,000 recorded species in 10 families, the second-largest of the four beetle suborders. Members of this suborder are collectively known as adephagans. The largest family is Carabidae which comprises most of the suborder with over 40,000 species. Adephaga also includes a variety of aquatic beetles, such as predaceous diving beetles and whirligig beetles.

The Dytiscidae – based on the Greek dytikos (δυτικός), "able to dive" – are the predaceous diving beetles, a family of water beetles. They occur in virtually any freshwater habitat around the world, but a few species live among leaf litter. The adults of most are between 1 and 2.5 cm (0.4–1.0 in) long, though much variation is seen between species. The European Dytiscus latissimus and Brazilian Megadytes ducalis are the largest, reaching up to 4.5 cm (1.8 in) and 4.75 cm (1.9 in) respectively. In contrast, the smallest is likely the Australian Limbodessus atypicali of subterranean waters, which only is about 0.9 mm (0.035 in) long. Most are dark brown, blackish, or dark olive in color with golden highlights in some subfamilies. The larvae are commonly known as water tigers due to their voracious appetite. They have short, but sharp mandibles and immediately upon biting, they deliver digestive enzymes into prey to suck their liquefied remains. The family includes more than 4,000 described species in numerous genera.

Hydrophilidae, also known colloquially as water scavenger beetles, is a family of beetles. Aquatic hydrophilids are notable for their long maxillary palps, which are longer than their antennae. Several of the former subfamilies of Hydrophilidae have recently been removed and elevated to family rank; Epimetopidae, Georissidae, Helophoridae, Hydrochidae, and Spercheidae. While the majority of hydrophilids are aquatic, around a third of described species are terrestrial, mostly belonging to the subfamily Sphaeridiinae.

Anti-predator adaptations are mechanisms developed through evolution that assist prey organisms in their constant struggle against predators. Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by avoiding detection, warding off attack, fighting back, or escaping when caught.

In 1938, the Austrian ethologist Karl von Frisch made his first report on the existence of the chemical alarm signal known as Schreckstoff in minnows. An alarm signal is a response produced by an individual, the "sender", reacting to a hazard that warns other animals, the receivers, of danger. This chemical alarm signal is released only when the sender incurs mechanical damage, such as when it has been caught by a predator, and is detected by the olfactory system. When this signal reaches the receivers, they perceive a greater predation risk and exhibit an antipredator response. Since populations of fish exhibiting this trait survive more successfully, the trait is maintained via natural selection. While the evolution of this signal was once a topic of great debate, recent evidence suggests schreckstoff evolved as a defense against environmental stressors such as pathogens, parasites, and UVB radiation and that it was later co-opted by predators and prey as a chemical signal.

Gyrinus natator, the common whirligig beetle, is a species of beetle native to the Palearctic realm, including much of Europe. Its range extends northwards as far as Norway, Finland, and the Saint Petersburg area of Russia. It is an aquatic beetle and moves rapidly around on the surface or swims underwater in still or slow-moving fresh water.

Hygrobia is a genus of aquatic beetles native to Europe, North Africa, China and Australia. It is the only genus in the family Hygrobiidae, also known as the Paelobiidae. These are known commonly as squeak beetles or screech-beetles.

<i>Acilius sulcatus</i> Species of beetle

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Green leaf volatiles (GLV) are organic compounds released by plants. Some of these chemicals function as signaling compounds between either plants of the same species, of other species, or even different lifeforms like insects.

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Phratora vitellinae, the brassy leaf beetle, formerly Phyllodecta vitellinae, is a beetle of the family Chrysomelidae found in Europe and Asia. It feeds on Populus and Salix species. The evolution of its host plant preferences and the mechanism by which it uses host plant chemicals to make a larval defensive secretion have been the subject of intense study by research groups in Europe and the Nordic countries.

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References

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↑ "Gyrinus minutus". GBIF. Retrieved 2019-09-23.
↑ "Gyrinus minutus species Information". BugGuide.net. Retrieved 2019-09-23.
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↑ Kenner, Rex D. (2000). "Gyrinus cavatus and G. minutus (Coleoptera: Gyrinidae) in British Columbia with comments on their nearctic distributions". Journal of the Entomological Society of British Columbia. 97: 67–72. ISSN 1929-7890.
↑ Angus, Robert B.; Holloway, Teresa C. (2016-03-21). "A chromosomal analysis of eleven species of Gyrinidae (Coleoptera)". Comparative Cytogenetics. 10 (1): 189–202. doi: 10.3897/CompCytogen.v10i1.7662 . ISSN 1993-0771. PMC 4856935 . PMID 27186347.
↑ Eisner, Thomas; Aneshansley, Daniel J. (2000). "Chemical defense: Aquatic beetle (Dineutes hornii) vs. fish (Micropterus salmoides)". Proceedings of the National Academy of Sciences of the United States of America. 97 (21): 11313–11318. doi: 10.1073/pnas.190335397 . PMC 17197 .
1 2 Ivarsson, Per; Henrikson, Britt-Inger; Stenson, Jan A. E. (1996-12-01). "Volatile substances in the pygidial secretion of gyrinid beetles (Coleoptera: Gyrinidae)". Chemoecology. 7 (4): 191–193. doi:10.1007/BF01266313. ISSN 1423-0445.
1 2 3 Karlsson, Anna-Karin Borg; Henrikson, Britt-Inger; Härlin, Carina; Ivarsson, Per; Stenson, Jan A. E.; Svensson, Bo W. (1999). "The Possible Role of Volatile Secretions as Intra- and Interspecific Alarm Signals in Gyrinus Species". Oikos. 87 (2): 220–227. doi:10.2307/3546737. ISSN 0030-1299. JSTOR 3546737.