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| Ecology and Behavior | |||||||||||||||||
| Characteristics | |||||||||||||||||
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Similar Species |
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| Chaoborus punctipennis is similar to C. americanus, C. trivittatus, and C. (albipes) flavicans; C. punctipennis is distinguished by its narrow, lanceolate prelabial leaf appendages compared to the wider prelabial leaf appendages of the other three species (length less than 7 times the width). | |||||||||||||||||
Geographic Distribution |
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| C. punctipennis has been reported in temperate and tropical lakes (1). It is the smallest and most widespread Chaoborus species in North America (2). | |||||||||||||||||
Reported Habitats |
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| The first two instars of C. punctipennis are completely planktonic, whereas the third and fourth instar larvae are often found in the sediments during the day (benthic) and can overwinter in this stage (1). C. punctipennis avoids visual predation because of its transparency and small size; therefore this species is commonly found in lakes with fish present (3). | |||||||||||||||||
Coexistance of Chaoborus Species and Niche Differentiation |
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| C. punctipennis is adapted to living in lakes with fish due to their highly transparent body and diel vertical migration behavior. In Northern Michigan lakes, C. punctipennis can live alone or coexist with C. flavicans and C. trivittatus, but only when fish are present (4). Curiously, neither of the other two chaoborids can live alone or together in lakes with fish unless C. punctipennis is also present (4). The ability of the three chaoborid species to coexist in the same lakes appears to be related to differences in size-related food preferences as well as emergence times. Differences in Chaoborus head widths are correlated with the maximum prey size and can be used as an indicator of the difference in the prey size of the three species. Head widths of C. punctipennis are smaller than the other two species as follows: C. punctipennis 1.07 mm, C. flavicans 1.35 mm, C. trivittatus 1.96 mm (4). Timing of Chaoborus species recruitment is also varied. Recruitment is staggered allowing individuals in each population to differ in size throughout the year. In northern Michigan, C. americanus was first to emerge as adults in the middle of May; C. flavicans emerged at the end of May; C. punctipennis emerged at the end of June; and C. trivittatus was last to emerge at the end of August (4). The first two instar stages of C. flavicans and C. punctipennis do not exhibit diel vertical migration and coexistence is also promoted by differing distributions between species (4). Chaoborus americanus is susceptible to fish predation because it lacks diel vertical migration, reaches adult stages during peak fish season and is the largest of the four Chaoborus species (4). C. americanus is found primarily in fishless lakes, particularly stained, bog lakes (4)(6) and its mandibles in the sediments has been used as an indicator of fishless lakes in Maine, USA (5). C. americanus preys on the early instars of C. punctipennis and C. flavicans, excluding them from fishless bog lakes (4)(6). C. trivittatus can co-exist with C. americanus by having a similar body length and overwintering as 2nd or 3rd instars making it too large for C. americanus to consume in the spring (4). |
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Food & Feeding Behavior |
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| C. punctipennis is a voracious predator on smaller zooplankton such as cladocerans, copepods and rotifers (2)(3). It is gape-limited (only ingesting food smaller than mouth) and detects prey by hydrodynamic disturbances in the water (7). First and second instar C. punctipennis, in an acidic lake in Canada, fed mostly on rotifers (7). The frequency of Keratella tauracephala found in crop of the C. punctipennis larvae increased with later instar generations, while the smaller, Trichocera spp., were eaten less (7). Bosmina longirostris made up most of the diet of older instars, although this could be due to the low abundance of copepods present (7). Dinoflagellates may be an important food source for C. punctipennis instars, more so than for larger species such as C. americanus (7). In New Hampshire lakes, C. punctipennis can be omnivorous ingesting large amounts of phytoflagellates and dinoflagellates, especially in first and second instars (2). This suggests C. punctipennis partially filter feeds via its mandibular fan, which could represent an energy-conserving feeding mechanism (2). |
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Reproductive Habits |
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| In a southern lake in North Carolina, C. punctipennis has two generations per year, an overwintering spring generation and a shorter summer generation (1). | |||||||||||||||||
Predation on Chaoborus |
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| Chaoborus species rarely co-occur with C. americanus in the fishless lakes. One reason for this is the larvae of C. americanus hatch earlier in the fishless ponds and feed on the later arriving Chaoborus (2)(4). C. punctipennis is particularly vulnerable to C. americanus predation. The larger C. americanus prefers to eat the smaller C. punctipennis, even in the presence of alternate prey (3). Other Chaoborus species (eg: C. americanus ) exhibit cannibalism on smaller instars and this may also occur with C. punctipennis if there is a large size difference between individuals (3). C. punctipennis minimize fish predation by diel vertical migration, allowing them to coexist in large and small lakes with fish (2). | |||||||||||||||||
| Chaoborus larvae are meroplanktonic, generally spending the daylight hours near or in the lake sediments and migrating toward the surface at night to feed on other zooplankton. C. punctipennis exhibits diel vertical migration using the relative rate (%) of light change as a trigger or cue that initiates its migration; thus, the percentage light is an predictor of the time (onset) of migration. When the relative change in light exceeds a threshold level (usually around dusk), Chaoborus migrate out of the sediments or anoxic zone and up through the water column, ascending at a speed that is a function of the relative rate of light changes (4). Vertical migrations are most pronounced in the fourth (final) larval instar and generally absent in the first two larval stages (3)(8). Diel vertical migrations of Chaoborus can be easily tracked in lakes using sonar with a frequency of 50-200 KHz. |
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Seasonal Variations |
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| Generally, larvae in the third and fourth instars (6.5-8.5 mm) over-winter, then grow rapidly in the early spring, with a peak in emergence as winged adult midges in early to mid-summer (1)(8). Adults generally live only a few days and do not feed. | |||||||||||||||||
References |
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(1) EATON, K. A. 1983. The life history and production of Chaoborus punctipennis (Diptera: Chaoboridae) in Lake Norman , North Carolina , USA. Hydrobiologia. 106: 247-252. (2) MOORE, M. V., N. D. YAN, AND T. PARSON. 1994. Omnivory of the larval phantom midge (Chaoborusspp.) and its potential significance for freshwater planktonic food webs. Can. J. Zool. 72: 2055-2065. (3) VON ENDE, C. N. 1979. Fish predation, interspecific predation, and the distribution of two Chaoborus species. Ecology. 60: 119-128. (4) VON ENDE, C. N. 1978. Regional coexistence of four Chaoborus species. Verh. Internat. Verein. Limnol. 20: 2630-2633. (5) Gaenzle Schilling, E., C. S. Loftin, K. E. DeGoosh, A. D. Huryn, and K. E. Webster. 2008. Predicting the locations of naturally fishless lakes. Freshwater Biology. 10: 1111 1365-2427. EMILY GAENZLE SCHILLING, CYNTHIA S. LOFTIN, KATIE E. DEGOOSH, ALEXANDER D. HURYN, KATHERINE E. WEBSTER (2008) (6) VON ENDE, C. N. 1975. Organization of bog lake zooplankton communities: factors affecting the distribution of four Chaoborus species (Diptera: Chaoboridae). Ph. D. Dissertation, Univ. of Notre Dame. 107 pp. (7) YAN, N. D., W. KELLER, H. J. MACISAAC, AND L. J. MCEACHERN. 1991. Regulation of a zooplankton community structure of an acidified lake by Chaoborus. Ecol. Appl. 1: 52-65. (8) HANEY, J. F., A. CRAGGY, K. KIMBALL, and F. WEEKS. 1990. Light control of evening vertical migration by Chaoborus punctipennis larvae. Limnol. Oceanogr. 35: 1068-1078. (9) MURBY, A. L., AND J. F. HANEY. 2006. Diel Vertical Migration of Zooplankton and Net Phytoplankton in Mendums Pond, N.H. Dept. of Zoology, Univ. of New Hampshire, Durham, NH USA (Research Poster). |
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