| Gerris | |
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| A pair of common water striders ( Gerris lacustris ) copulating | |
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| Genus: | Gerris Fabricius, 1794 |
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Gerris is a bug genus in the family Gerridae (water striders). [1] [2]
The genus Gerris contains 43 species in 3 subgenera: [3]
Species of genus Gerris demonstrate a high degree of female control over most aspects of mating and there is significant evidence that supports antagonistic coevolution, and the convenience polyandry hypothesis of multiple matings. [4] [5] There is evidence to suggest that the post-copulatory guarding exhibited by Gerris buenoi - and other species of Gerris - is a form of a direct (material) benefit that females take advantage of to reduce superfluous matings. [6] [4]
Male persistence is often detrimental to female fitness as male species of Gerris harass females. [4] [5] This is believed to be the result of males having a lower number of available mates and therefore, have a reduced fitness. [7] Females are at risk of predation during mating attempts as males mount the female in an attempt to mate and tap their legs on the surface of the water to attract predators. [8] Females respond in turn, creating a pre-copulatory struggle in which they try to perform backwards somersault-like movements to break free of the male grapple. [9] If unsuccessful, female species of Gerris will resort to mating with the male as the cost of rejecting the male advances (death by predation) outweighs the cost of mating out of convenience. [4] [9]
As a result of the tactics employed by both species there is evidence of rapid evolution between the sexes in a persistence-resistance form of sexual conflict. [5] The sexes of species of genus Gerris compete between each other in an "arms race" behaviour where males and females have varying traits that serve to increase their own fitness over the other. [5] Males evolved to harass females by chasing and lunging in an attempt to grapple the female for copulation, and females evolved mechanisms such as genital shielding, evasive maneuvers, and attempting to fight even when grappled. However, evading and fighting are quite costly for females and will give in if the costs of resistance outweigh the cost of mating. [5] [4] Genital shielding can best be seen in G. gracilicornis and a male will have a hard time at inserting his genitalia unless the female protrudes her genitalia out. [10] Males have evolved to overcome this mechanism by attempting an intimate courtship instead of forceful mating, as well as a more hostile approach: attracting predators to force mating with females. [4] [10] [5] The rationale behind attracting predators to force mating is due to how copulation occurs: a male will attempt to mount a female on the surface water; it is the female that is at most risk from insect-eating fish and water dwelling predators. [4] [10] [5] [9]
After copulation, males continue to rest on top of females for some period of time - this is what is known as guarding duration. [4] [7] It can be hypothesized that when superfluous matings are plenty, females will extend this guarding duration by allowing the male to rest upon her for some time which in turn prevents harassment from other males. It is worth noting that this also incurs costs for the female as they must exert energetic costs to compensate for the passive male on her back, and that this might not be an effective tactic for females in the long run. [7] [11]
Water striders, and more specifically those that fall under the genus Gerris are a model organism for studying sexual conflict as they have clear costs associated with their actions. They have great use as a control group when comparing to other organisms where it is more unclear as what is occurring.
The Gerridae are a family of insects in the order Hemiptera, commonly known as water striders, water skeeters, water scooters, water bugs, pond skaters, water skippers, water gliders, water skimmers or puddle flies. Consistent with the classification of the Gerridae as true bugs, gerrids have mouthparts evolved for piercing and sucking, and distinguish themselves by having the unusual ability to walk on water, making them pleuston (surface-living) animals. They are anatomically built to transfer their weight to be able to run on top of the water's surface. As a result, one could likely find water striders present in any pond, river, or lake. Over 1,700 species of gerrids have been described, 10% of them being marine.
Pipefishes or pipe-fishes (Syngnathinae) are a subfamily of small fishes, which, together with the seahorses and seadragons, form the family Syngnathidae.
Sexual conflict or sexual antagonism occurs when the two sexes have conflicting optimal fitness strategies concerning reproduction, particularly over the mode and frequency of mating, potentially leading to an evolutionary arms race between males and females. In one example, males may benefit from multiple matings, while multiple matings may harm or endanger females, due to the anatomical differences of that species. Sexual conflict underlies the evolutionary distinction between male and female.
Sexual cannibalism is when an animal, usually the female, cannibalizes its mate prior to, during, or after copulation. It is a trait observed in many arachnid orders and several insect and crustacean clades. Several hypotheses to explain this seemingly paradoxical behavior have been proposed. The adaptive foraging hypothesis, aggressive spillover hypothesis and mistaken identity hypothesis are among the proposed hypotheses to explain how sexual cannibalism evolved. This behavior is believed to have evolved as a manifestation of sexual conflict, occurring when the reproductive interests of males and females differ. In many species that exhibit sexual cannibalism, the female consumes the male upon detection. Females of cannibalistic species are generally hostile and unwilling to mate; thus many males of these species have developed adaptive behaviors to counteract female aggression.
Traumatic insemination, also known as hypodermic insemination, is the mating practice in some species of invertebrates in which the male pierces the female's abdomen with his aedeagus and injects his sperm through the wound into her abdominal cavity (hemocoel). The sperm diffuses through the female's hemolymph, reaching the ovaries and resulting in fertilization.
Nicrophorus defodiens is a burying beetle described by Mannerheim in 1846.
The six-spotted fishing spider is an arachnid from the nursery web spider family Pisauridae. This species is from the genus Dolomedes, or the fishing spiders. Found in wetland habitats throughout North America, these spiders are usually seen scampering along the surface of ponds and other bodies of water. They are also referred to as dock spiders because they can sometimes be witnessed quickly vanishing through the cracks of boat docks. D. triton gets its scientific name from the Greek mythological god Triton, who is the messenger of the big sea and the son of Poseidon.
Sexual antagonistic co-evolution is the relationship between males and females where sexual morphology changes over time to counteract the opposite's sex traits to achieve the maximum reproductive success. This has been compared to an arms race between sexes. In many cases, male mating behavior is detrimental to the female's fitness. For example, when insects reproduce by means of traumatic insemination, it is very disadvantageous to the female's health. During mating, males will try to inseminate as many females as possible, however, the more times a female's abdomen is punctured, the less likely she is to survive. Females that possess traits to avoid multiple matings will be more likely to survive, resulting in a change in morphology. In males, genitalia is relatively simple and more likely to vary among generations compared to female genitalia. This results in a new trait that females have to avoid in order to survive.
Interlocus sexual conflict is a type of sexual conflict that occurs through the interaction of a set of antagonistic alleles at two or more different loci, or the location of a gene on a chromosome, in males and females, resulting in the deviation of either or both sexes from the fitness optima for the traits. A co-evolutionary arms race is established between the sexes in which either sex evolves a set of antagonistic adaptations that is detrimental to the fitness of the other sex. The potential for reproductive success in one organism is strengthened while the fitness of the opposite sex is weakened. Interlocus sexual conflict can arise due to aspects of male–female interactions such as mating frequency, fertilization, relative parental effort, female remating behavior, and female reproductive rate.
Aquarius remigis, known as the common water strider, is a species of aquatic bug. It was formerly known as Gerris remigis, but the subgenus Aquarius was elevated to generic rank in 1990 on the basis of phylogenetic analysis. Aquarius remigis is found throughout North America, but is most prevalent in the mid-west of the United States.
Aquarius najas, also known as the river skater, is a European species of water strider. It was formerly known as Gerris najas, but the subgenus Aquarius was elevated to generic rank in 1990 on the basis of phylogenetic analysis.
Female copulatory vocalizations, also called female copulation calls or coital vocalizations, are produced by female primates, including human females, and female non-primates. Copulatory vocalizations usually occur during copulation and are hence related to sexual activity. Vocalizations that occur before intercourse, for the purpose of attracting mates, are known as mating calls.
Sexual coercion among animals is the use of violence, threats, harassment, and other tactics to help them forcefully copulate. Such behavior has been compared to sexual assault, including rape, among humans.
In behavioral ecology, polyandry is a class of mating system where one female mates with several males in a breeding season. Polyandry is often compared to the polygyny system based on the cost and benefits incurred by members of each sex. Polygyny is where one male mates with several females in a breeding season . A common example of polyandrous mating can be found in the field cricket of the invertebrate order Orthoptera. Polyandrous behavior is also prominent in many other insect species, including the red flour beetle and the species of spider Stegodyphus lineatus. Polyandry also occurs in some primates such as marmosets, mammal groups, the marsupial genus' Antechinus and bandicoots, around 1% of all bird species, such as jacanas and dunnocks, insects such as honeybees, and fish such as pipefish.
Aquarius is a genus of water striders found predominantly in the northern hemisphere. Formerly a subgenus, Aquarius was elevated to generic rank in 1990 on the basis of phylogenetic analysis. These are among the world's largest water striders, with females averaging 12–17 mm (0.47–0.67 in) long and males roughly 10–30% smaller, depending on the exact species. An outlier is A. elongatus where both sexes typically are about 24 mm (0.94 in), roughly the same as certain Cylindrostethus, and second only to Gigantometra gigas.
Limnoporus is a genus of water striders in the family Gerridae. There are six extant described species in Limnoporus.
Gerris comatus is a species of water strider in the family Gerridae. It is found in North America.
Agelenopsis pennsylvanica, commonly known as the Pennsylvania funnel-web spider or the Pennsylvania grass spider, is a species of spider in the family Agelenidae. The common name comes from the place that it was described, Pennsylvania, and the funnel shape of its web. Its closest relative is Agelenopsis potteri.
Gerris buenoi is a species of water strider that belongs to the family Gerridae. It was first identified in 1911 and is native to continental USA and Canada. Individuals of this species are small in size and have modified appendages, allowing them to float and "skate" along the surface of the water. G. buenoi can be found near the shoreline of freshwater ponds and small lakes, where they hunt for terrestrial insects that have fallen into the water.
The sensory trap hypothesis describes an evolutionary idea that revolves around mating behavior and female mate choice. It is a model of female preference and male sexual trait evolution through what is known as sensory exploitation. Sensory exploitation, or a sensory trap is an event that occurs in nature where male members of a species perform behaviors or display visual traits that resemble a non-sexual stimulus which females are responsive to. This tricks females into engaging with the males, thus creating more mating opportunities for males. What makes it a sensory trap is that these female responses evolved in a non-sexual context, and the male produced stimulus exploits the female response which would not otherwise occur without the mimicked stimulus.
