Life History of the Chironomidae Is Scattered Through a Wide Variety of Papers in Many Languages
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Copyright 1971. All rights reserved LIFE mSTORY OF THE CHIRONOMIDAE 6008 D. R. OLIVER Entomology Research Institute, Canada Department of Agriculture, Ottawa, Ontario, Canada Information on the life history of the Chironomidae is scattered through a wide variety of papers in many languages. The present article is based mainly on papers that have been published since 1950 as the earlier papers were reviewed thoroughly in Chironomus by Thienemann (101). Additional references and information on most of the topics covered here may be found in this excellent book. Even with this restriction a high degree of selection is necessary and most of the papers on genetics, physiology, pro ductivity and biomass, and fish food are not considered. Many of the papers cited have been chosen because they are most likely to be useful for fur ther reference. CLASSIFICATION It seems necessary to comment briefly on the reasons for the confusion which exists in the classificationof the Chironomidae. Part of the confusion arises from the dual use of two family names. The name Tendipes Meigen 1800 was used rather than Chironomus Meigen 1803 by many taxonomists as the type genus of the family. A recent ruling of the International Com mission on Zoological Nomenclature has suppressed the Meigen 1800 names by University of Sussex on 05/26/12. For personal use only. in favor of his 1803 names (see Fittkau 39). As a result, the name Ten dipes was suppressed in favor of Chironomus, and similarly Pelopia was suppressed in favor of Tanypus. This action means that the correct name of the family is Chironomidae not Tendipedidae. Furthermore, it also estab Annu. Rev. Entomol. 1971.16:211-230. Downloaded from www.annualreviews.org lishes that the subfamily names Chironominae and Tanypodinae are correct. Although not covered by a ruling it is generally accepted that Orthocladii nae be used in place of Hydrobaeninae. Tanytarsus has been used as a ge nus in the tribe Chironomini, but another ruling (Bull. Zool. Nom. 18, Opin ion 616) established it as a genus in the tribe Tanytarsini. The classification of holometabolous insects presents special difficulties because the characteristics of all the life stages must be considered. Differ ent ecological requirements of each stage often result in greater diversity, both ecological and morphological, in one stage than in another. The adults of the Chironomidae are usually more uniform in structure than are the immature stages, especially the larvae. The adult stage is somewhat ephem- 211 212 OLIVER eral, completing the reproductive aspects of the life cycle in a fairly short time. Adults require only minimum shelter for mating, maturing eggs, and ovipositing. In contrast, the largest part of the life cycle is spent in the lar� val stage and the range of habitats occupied is perhaps unparalleled among other insect groups. All the energy required to complete the life cycle is built up in the larval stage, because the adults, with few exceptions, do not feed. This ecological diversity between the life stages is shown in the two systems of classification that have evolved; the larval and pupal system of Thienemann and his associates and the adult system of Edwards and Goet� ghebuer (in 13). The generic limits in the system based on the immature stages are frequently narrower than those based on adults. Fortunately, many recent studies have been based on all three stages (e.g., Brundin 13, 14; Fittkau 37), and a more stable system of classification is beginning to evolve. The general classification used as a basis for discussion in this publica� tion follows that of Brundin (14). Seven subfamilies, as follows, are recog� nized: Tanypodinae, Podonominae, Aphroteniinae, Telmatogetoninae, Diamesinae, Orthocladiinae, and Chironominae. Each subfamily, except the Telmatogetoninae, has several tribes, but only the tribes Chironomini and Tanytarsini belonging to the Chironominae are used here. DISTRIBUTION AND HABITAT DIVERSITY The distribution of the family is world�wide. The two species found in Antarctica are the southernmost free-living holometabolous insects known (106). Chironomids extend to the northern limits of land, and they make up one-fifth to one-half of the total number of species in the arctic insect fauna (80). Between these geographical extremes they have radiated into nearly every habitat that is aquatic or wet, including peripheral areas of the oceans (105). Some of these habitats have a very large number of species, e.g., 140 species live in Lake Innaren (11) and 168 in Lake Constance (86). There is no reliable estimate of the total number of species in the family: over 5000 by University of Sussex on 05/26/12. For personal use only. species have been described to date and the species living in large areas such as Asia are almost unknown. The distribution of each of the subfamilies, within their geographical Annu. Rev. Entomol. 1971.16:211-230. Downloaded from www.annualreviews.org range, is primarily governed by the availability of water ecologically suited to the requirements of the larvae. The Aphroteniinae, the smallest subfam ily, with eight species, is strictly rheophilic; it is more or less confined to swift mountain streams in southern South America, South Africa, and Aus� tralia. The Podonominae, primarily rheophilic and cold-adapted, is much more common in the Southern Hemisphere, particularly the southern part where 130 species have been found, than in the Northern Hemisphere, where only 20 species have been recorded. One genus, Lasiodiamesa, has become adapted to warm pools in sphagnum bogs. The Diamesinae is also a rheophilic and cold-adapted group, though a few genera occur in lentic hab� itats; they inhabit the colder parts of the circumpolar lands and the moun- LIFE HISTORY OF CHIRONOMIDS 213 tain ranges throughout the world. All these subfamilies are absent in the tropical lowlands (14). Most of the species in the family belong to one of the subfamilies Tany podinae, Chironominae or Orthocladiinae, which are more or less world wide in distribution. Most of the Tanypodinae and Chironominae are essen tially thermophilous and adapted to living in standing water, though species of each do occur in cool habitats and in mnning water. Both subfamilies occur in all geographical regions except Antarctica. They are very abun dant in the warmer parts of the Holoarctic and decrease in numbers with increasing latitude, or its climatological equivalent. Eighty percent of the chironomids living in forest streams of the central Amazon region are Chi ronominae (38). The Tanypodinae also are common in the tropics but they are probably more boreal (37). The Orthoc1adiinae occupy the widest range of habitats of all chironomids. It is the dominant subfamily in the arctic region (80) and, in contrast with the Chironominae and the Tanypodinae, decreases in numbers in increasingly warmer regions, though they are not uncommon in many warm habitats (e.g., 38). The larvae of this primar ily cold-adapted subfamily live in all types of lentic and lotic habitats. It is the only subfamily with terrestrial species (13, 14) that live not only in the wet margins of water bodies but also in quite nonaquatic habitats such as cow dung (61). The Telmatogetoninae, the largest marine group, is associated with rocky peripheral areas that are usually subjected to tidal action. The larvae are euryhaline and are often found in areas that receive freshwater runoff; one species of Telmatogeton lives in swift mountain streams in Hawaii (105). These peripheral marine habitats, as well as brackish rock pools, also ha ve been invaded by larvae of the Orthoc1adiinae and Chironominae (46, 47,83). Brundin (14) believes that the primitive habitat in which chironomid evolution began was the upper reaches of mountain streams that arose from cool springs and ran through hygrophilous, temperate forests. It was a by University of Sussex on 05/26/12. For personal use only. rather stable habitat, rich in dissolved oxygen and diatoms, with moderate annual variation in temperature and water level. In his account of the evo lution of the Chironomidae within the framework of Hennig's sister group Annu. Rev. Entomol. 1971.16:211-230. Downloaded from www.annualreviews.org theory, Brundin (14) shows that the "pleisomorph lines" have remained rheobiontic, whereas the "apomorph lines" adapted to the different types of lentic water. As he points out, there are exceptions, e.g., the Tanypodinae are primarily lcntic but the occurrence of the genera Rheopelopia, Concha pelopia, and Macropelopia in running water is a secondary adaptation. The Tanypodinae is considered to be the "apomorph" sister group of the Aphro teniinae and the Podonominae. Together these three subfamilies form the sister group of the remaining four subfamilies. Within this latter group the Chironominae is considered to be the "apomorph" sister group of the Tel matogetoninae, Diamesinae, and Orthocladiinae. As previollsly mentioned, many of the larvae in these two "apomorphic" subfamilies (Tanypodinae 214 OLIVER and Chironominae) within each major sister group are lentic and thermoph ilous. Accepting the thesis that the larvae of the Chironomidae were ini tially cool-adapted, the success of the family in the colder regions is not surprising. In the arctic region and in cold mountain streams larvae develop at temperatures close to the limit of life and no major special adaptations appear to have evolved (14, 80), except the ability of some larvae to with ' stand freezing (2). In contrast, a number of ecological and physiological specializations have evolved to accommodate conditions found in warm standing water, such as the free-living pupae of the Tanypodinae (14), the presence of hemoglobin in the larvae of the Chironominae (14, 102), and the most unusual ability of Polypedilum vanderplankii larvae to completely dehydrate and remain viable under dry conditions for months (51). THE LIFE CYCLE The four life stages, egg, larva, pupa, and adult, are treated separately.