Reproduction of Potamothrix hammoniensis (Oligochaeta) in shallow eutrophic lakes

Janusz Żbikowski, Daria Mimier, Elżbieta Żbikowska

Percentage of sexually mature individuals of Potamothrix hammoniensis in the studied lakes

Paper category: Original research paper
Corresponding author: Janusz Żbikowski (jzbikow@umk.pl)
DOI: 10.1515/ohs-2018-0017
Received: September 06, 2017
Accepted: January 05, 2018
Full text: here

Abstract

The aim of the study was to indicate the abiotic parameters of water and bottom sediments, which significantly affect the reproduction of Potamothrix hammoniensis in 9 shallow eutrophic lakes, of which 5 were dominated by macrophytes and 4 – by phytoplankton. Samples were collected once a month from January to December 2012. The percentage of Potamothrix hammoniensis individuals with a developed reproductive system varied in individual lakes and ranged from 14 to 72%. There was no correlation between the distinguished lake types and the proportion of sexually mature individuals. The reproductive activity was not observed in summer and early autumn. Among the measured parameters, the highest values of the Pearson correlation coefficient were found between the percentage of individuals with a developed reproductive system and the conductivity (r = 0.69; p < 0.001), pH (r = 0.51; p = 0.002) and the organic matter content in the sediments (r = −0.42; p = 0.012). It is worth noting that there was no correlation between the percentage of sexually mature specimens and the water temperature (r = −0.22, p = 0.204) and the oxygen concentration (r = −0.08; p = 0.648).

Faculty of Biology and Environmental Protection, Nicolas Copernicus University in Toruń, ul. Lwowska 1, 87-100 Toruń, Poland

Faculty of Biology and Environmental Protection, Nicolas Copernicus University in Toruń, ul. Lwowska 1, 87-100 Toruń, Poland

Faculty of Biology and Environmental Protection, Nicolas Copernicus University in Toruń, ul. Lwowska 1, 87-100 Toruń, Poland


Digenetic trematodes and molluscs


Digenetic trematodes are the largest group within the flatworms (Platyhelminthes) containing from 18 to 25 thousand species. Most of these organisms are hermaphroditic, except representatives of some families such as Schistosomatidae and Didymozoidae. The most characteristic feature of digenetic trematodes is complex life cycles with various developmental stages occurring in intermediate and final hosts. The definitive hosts of these parasites are all groups of vertebrates: fish, amphibians, reptiles, birds, and mammals, including humans. The first intermediate host is almost always a mollusc (especially freshwater snails) in which sporocysts and/or rediae reproduce asexually. The next larval stages - cercariae released from molluscs find a second intermediate host (various groups of invertebrates and vertebrates), in which they transform into invasive stages - metacercariae. A final host becomes infected by ingestion of a second intermediate host with metacercariae.
Molluscs playing a crucial role in the life cycle of Digenea are convenient material for parasitological research because of the ease of their collecting and maintaining in a laboratory. The close relationship between trematodes and molluscs, indicating the specificity of a host-parasite system, allows for consideration of the phenomenon of parasitism in terms of:

  • immunity (responses of mollusks to trematode invasion, defense mechanisms of trematodes)

  • physiology (impact of trematodes on behavior, fertility, and appearance of molluscs)

  • ecology (regulation of molluscan populations by trematodes, modulating interactions of infected molluscs with other organisms, trematodes as indicators of "ecosystem health", classic and modified life cycles of Digenea)

  • evolution (specificity of the trematode - mollusc system, relationships between species)

  • epidemiology (distribution of trematodes of medical or veterinary importance)

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