Gerromorpha
| Gerromorpha | ||||||||||
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Common pond runner ( Hydrometra stagnorum ) |
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| Gerromorpha | ||||||||||
| Popov , 1971 |
The Gerromorpha (water striders i. W. S.) are a suborder of the bed bugs (Heteroptera). The family group includes around 1900 described species worldwide. 51 of them have been found in Europe. Although the predatory bugs that live on the surface of the water occur mainly in freshwater bodies of water, some species of the subfamily Halobatinae (family water striders (Gerridae)) also live in the open sea. The animals are perfectly adapted to life on the surface of the water.
features
The Gerromorpha show great variability , especially in the construction of their legs and thorax , which reflects the range of specialization of the different species in their life on the water surface. This is particularly noticeable in the long-legged Gerridae. Common to all Gerromorpha is a fine hydrophobic hair on the head, thorax and on parts of the abdomen. The adults have three pairs of inserting trichobothria in deep pits on their heads . On the praetarsus there is an arolium dorsally and ventrally .
There is a sexual dimorphism between the sexes, since the females are usually noticeably larger than the males. However, this is not infrequently the other way around, especially with larger species. With the Gerrinae and here especially with the genera Aquarius , Gerris and Limnoporus , the size difference decreases proportionally with increasing average size of the animals. With the exception of the wing polymorphism, most gerromorpha are almost uniform in appearance within their species. Within a population of the same species there are individuals with long and short wings and / or there are individuals who have no wings at all.
distribution
The group is widespread worldwide and is absent only in Antarctica . The main area of distribution is in the Neotropics , in central and western Africa, Madagascar and in the Indo-Australian region. Numerous species are also known from southern Asia, the Malay Archipelago and New Guinea, especially in moist soil habitats and in rivers. The Gerromorpha are found to be particularly strong in marine habitats in the Indo-West Pacific, where around 150 species in 16 genera and 5 families occur. Most species of the marine sea water striders ( Halobates ) live near the coast, but there are several species that are completely oceanic.
The bugs colonize a variety of different habitats. They include the Pleuston (surface of the open water) and also the surfaces that are colonized by algae or aquatic plants. Still or slowly flowing waters are settled, but also torrents, the intertidal zone such as z. B. Mangroves and coral reefs and the open ocean. In addition, there are several types of different subgroups that colonize moist land habitats, such as moist earth, or moist gravel and stones at springs and hygropetric biotopes with algae and deciduous moss growth. Not only permanent, but also temporarily humid habitats are populated. In the case of the sea sandpiper species living in the ocean, the distribution is mainly linked to the surface temperature of the water. Large populations can only be found in places where the temperature is above 24 ° C.
Way of life
Gerromorpha are predatory scavengers that use their stinging-sucking mouthparts that are typical of bedbugs for food. While a few species feed on dead vertebrates and even attack live fish, most species feed on insects. Unlike the males, the larger females can also attack larger prey. Even if the bugs have some influence on various insects that hatch on the water, they mainly feed on insects that unintentionally land on the water, such as grasshoppers. So they are z. B. in rice fields important beneficial insects against herbivorous insects. Individual animals usually eat smaller prey, but it also often happens that many eat larger prey together. What is interesting is that the first bugs arriving at the prey usually get less food than those arriving later, as they can take in the prey that has already been liquefied by the nutritional juices of the other with less effort. This even means that individual animals tend to eat such prey for longer, even when predators are approaching.
pairing
The males of different gerromorpha cause waves on the water surface to attract females. So send z. For example, the males of Gerris remigis , when carried by the females, emit signals between 90 and 100 Hz , which deter competitors and probably also improve the female's prey luck. There are also species that use signals of different frequencies to deter competitors and influence females. Four basic mating mechanisms are known: a monogamy-like behavior, which results from the male guarding the female after the mating, or which results from the monopoly of the first male through the construction of the female apparatus for storing the sperm; Polygyny , through the defensive act of a male in a certain egg-laying place; pure dominance or polygyny on a lek , as well as polygyny in mixed competition including the extended search for females ready to mate and guarding them after they have laid eggs.
Depending on the species, the females can be stimulated to lay eggs in response to signals from the male after mating, in which case the males try to maintain their dominance over other males, but they can also lay the eggs alone, regardless of the behavior of the male. Females of species in which no pronounced courtship behavior takes place before mating first defend themselves against the male before they allow mating, whereby the potential partner is presumably examined for mating suitability. The fights between the sexes, which become more frequent, especially with large population densities, are resource-binding for the females. Females with a partner who successfully drives away other males can concentrate better on foraging for food, which is more beneficial to them, although the attached male makes them more likely to become prey to predators.
development
Gerromorpha usually go through five (very rarely four) larval stages. During their development, the body appendages grow proportionally faster than the rest of the body, so that it can be seen that the rapid development of the musculoskeletal system has high priority. The development time is indirectly proportional with increasing temperature and lasts between 40 and 65 days in the temperate latitudes and the tropics. However, the species of the genera Mesovelia and Halobates, for example, develop much faster . The animals usually need the longest time to develop in the egg stage and the two last larval stages.
Most species are adaptable in their rate of reproduction, so that there can be locally mixed populations that are univoltin, (partially) bivoltion or multivoltin. Only a few species are obligatory univoltin and therefore only ever produce one generation per year. Some tropical species are active all year round, but there are also species that z. B. are not active in dry seasons, or their activity is based on the chlorophyll concentration of surface water, such as the oceanic species of the genus Halobates , which have their greatest reproductive activity when the chlorophyll has the lowest concentration. Species of the temperate latitudes overwinter as adults on land, flightless in isolated habitats mostly near the water, but flightable usually look for a place further away from the water. But there are also species in which the eggs overwinter.
Natural enemies
In addition to the weather, which can strongly influence the population density of the Gerromorpha, in addition to the other natural enemies, the frequently observed cannibalism plays a significant role in the population development. For example, a study showed that nymphs of the Gerris pingreensis species developed significantly better if they were given the opportunity to eat smaller members of their suborder. After all, the adult animals did not differentiate between conspecifics and other representatives of the partial order during their hunt. Cannibalism does not occur in all types of gerromproha. It generally increases with decreasing food supply and is restricted by the complexity of the habitat.
Representatives of the Gerromorpha are also from a number of aquatic and semi-aquatic invertebrates, such as. B. Floating beetles (Dytiscidae), back swimmers (Notonectidae), dragonflies and predatory spiders (Pisauridae) are captured to a relevant extent. In addition, parasitoids that infect the eggs also have a major impact on population development. It is conceivable that these clog some species in such a way that they only develop in a temporarily stable manner where wintering parasitoid wasps do not find ideal living conditions. In addition to all of these, birds and fish are also non-specific enemies and mites and trypanosomatida are considered parasites that can weaken populations.
Fossil Finds
Fossil finds from representatives of the Gerromorpha are only known sporadically. Species of the Hydrometridae and Gerridae are known from Denmark in the Upper Paleocene and date approximately 55 million years ago . Since most of the Mesoveliidae and Veliidae finds date from the Lower Cretaceous , it can be assumed that most of the families of the group probably originated in the early Mesozoic Era and that the group has existed for about 120 million years. Fossil are at least 35 species from six families known (2005).
Taxonomy and systematics
The monophyly of the seven partial orders of the bedbugs was confirmed in a multigene study from 2012 based on molecular phylogeny. This showed that the Gerromorpha is closely related to the partial order of the Dipsocoromorpha .
A phylogenetic investigation of the Gerromorpha subtaxa in 2005 confirmed the close relationship between the Gerridae, Hermatobatidae and Veliidae, which together form the superfamily Gerroidea. At the family level, there were no contradictions to the relationships of the Gerromorpha identified by Spencer and Andersen in 1994 as the basis of the discussion for a long time. Only the monophyly of the Veliidae would no longer be given in the original consideration, which is why the genus Ocellovelia (subfamily Ocelloveliinae ) had to be placed as a sister group to the other Veliidae. At the same time, however, many questions remain unanswered with regard to the relationships between the groups below the family level. Although there was a close relationship between the subfamilies Halobatinae and Ptilomerinae of the Gerridae, the relationships within this family could otherwise hardly be broken down. It was also shown that the subfamily Veliinae of the Veliidae is probably not monophyletic.
The following cladogram results from the above findings:
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supporting documents
Individual evidence
- ↑ a b c d Jakob Damgaard, Nils M. Andersen, Rudolf Meier: Biology of Water Striders: Interactions Between Systematics and Ecology . In: Systematic Entomology . 30, 2005, pp. 289-309.
- ^ Nepomorpha. Fauna Europaea, accessed October 12, 2013 .
- ^ Ekkehard Wachmann , Albert Melber, Jürgen Deckert: Bugs. Volume 1: Cimicomorpha: Dipsocoromorpha, Nepomorpha, Gerromorpha, Leptopodomorpha, Cimicomorpha (part 1) (= The animal world of Germany and the adjacent sea parts according to their characteristics and according to their way of life . 77th part). Goecke & Evers, Keltern 2006, ISBN 3-931374-49-1 , p. 60 .
- ↑ a b c d e f g h i j k l m n John R. Spence, Nils Møller Andersen: Combining molecular and morphological analyzes of water strider phylogeny (Hemiptera – Heteroptera, Gerromorpha): effects of alignment and taxon sampling . In: Annual Review of Entomology . 39, 1994, pp. 101-128.
- ↑ Wilfried Westheide, Gunde Rieger (Ed.): Special Zoology. Part 1: Protozoa and invertebrates . 3. Edition. Springer-Verlag, Berlin Heidelberg 2013, ISBN 978-3-642-34695-8 , pp. 687 .
- ↑ a b Min Li, Ying Tian, Ying Zhao, Wenjun Bu (2012): Higher Level Phylogeny and the First Divergence Time Estimation of Heteroptera (Insecta: Hemiptera) Based on Multiple Genes. PLoS ONE 7 (2): e32152. doi : 10.1371 / journal.pone.0032152 (open access)
literature
- Ekkehard Wachmann , Albert Melber, Jürgen Deckert: Bugs. Volume 1: Cimicomorpha: Dipsocoromorpha, Nepomorpha, Gerromorpha, Leptopodomorpha, Cimicomorpha (part 1) (= The animal world of Germany and the adjacent sea parts according to their characteristics and according to their way of life . 77th part). Goecke & Evers, Keltern 2006, ISBN 3-931374-49-1 .
