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  • 1
    Electronic Resource
    Electronic Resource
    Does body size difference in the leeches Glossiphonia complanata (L.) and Helobdella stagnalis (L.) contribute to co-existence? (1994)
    Springer
    Hydrobiologia 273 (1994), S. 67-75 
    Details
    ISSN: 1573-5117
    Keywords: Glossiphonia complanata ; Helobdella stagnalis ; leeches ; lake ; food ; competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of predator and prey body size on the feeding success of the British lake-dwelling leeches Glossiphonia complanata and Helobdella stagnalis was examined in the laboratory, and any involvement of size difference between the leeches in allowing coexistence in the field assessed. G. complanata breeds in advance of H. stagnalis and maintains a body size advantage throughout their annual life-cycle. In experiments, conducted at 14 °C and a photoperiod of 16 hrs L: 8 hrs D, three size classes of leeches of each species were each exposed to each of three size classes of each of five prey species, viz. Tubifex sp., Chironomus sp., Asellus aquaticus, Lymnaea peregra and Potamopyrgus jenkinsi. For each prey species, three different types of experiments were performed: one leech exposed to four prey individuals; four leeches of the same species with sixteen prey; and two leeches of each species with sixteen prey. In the first experiment, all sizes of G. complanata were capable of feeding on all sizes of the prey types offered; the same was true for H. stagnalis with exceptions of feeding on large A. aquaticus and large L. peregra. For both species, but especially for G. complanata, there was a trend within each size class of leech for decreasing proportions of fed leeches with increasing prey size, and within each size class of prey for an increasing proportion of fed leeches with increasing leech size; however there were several exceptions to these trends. Both leeches fed extensively on Tubifex sp. but there were significant differences in the proportions feeding on other prey types; G. complanata fed more on A. aquaticus and the two snail species, and less on Chironomus, than H. stagnalis. The effect of increasing the number of leech individuals from one to four individuals, of the same or mixed species, had little effect on the proportion of leeches which had fed. It is concluded that large G. complanata will have access to large individuals of certain prey taxa denied H. stagnalis, which may lessen the intensity of interspecific competition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00006848
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The consequence of a food refuge collapse on a guild of lake-dwelling triclads and leeches (1994)
    Springer
    Hydrobiologia 277 (1994), S. 187-195 
    Details
    ISSN: 1573-5117
    Keywords: triclads ; leeches ; food refuge ; snails ; lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The diets ofPolycelis nigra, P. tenuis, Dugesia polychroa, Dendrocoelum lacteum, Glossiphonia complanata, Helobdella stagnalis andErpobdella octoculata in an English lake were examined, using a serological technique, and compared between 1981–82 and 1989–90. Leech, triclad and prey abundances were also recorded. Between the two studies, snail numbers crashed whereas the abundances ofAsellus andGammarus increased.Dugesia andGlossiphonia numbers decreased substantially, whilstPolycelis tenuis andHelobdella abundances increased. In the second study, the snail component in the diet was greatly reduced resulting in a broader food niche, particularly forDugesia andGlossiphonia, and greater food overlap between the predators with the exception ofDendrocoelum andErpobdella which do not eat molluscs. It is postulated that the reduced size of the snail refuge, and consequent increase in severity of interspecific competition with other predators, particularlyPolycelis andHelobdella, led to the observed decrease in abundances ofDugesia andGlossiphonia. The decline in the last two genera, perhaps coupled with increased crustacean abundance, could have contributed to the numerical increase of the competitively superiorPolycelis tenuis andHelobdella.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007300
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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