Contributions to Zoology, 80 (1) – 2011Pawel Koperski; Rafal Milanowski; Agnieszka Krzyk: Searching for cryptic species in Erpobdella octoculata (L.) (Hirudinea: Clitellata): discordance between the results of genetic analysis and cross-breeding experiments
Material and methods

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Field study

FIG2

Table 1. Morphological variability of E. octoculata expressed as a percentages of morphological forms and values of NPA index (percentage of non-pigmented area on the dorsal side of the body - see methods for details) in different types of freshwater habitats. The results of post-hoc comparisons (Tukey’s test) presented as a homogenic groups.

FIG2

Fig. 1. Morphological forms of Erpobdella octoculata. Schematic drawings of the dorsal side of the individuals’ body, presenting colouring patterns (grey - dark pigmented area, white - unpigmented area) on the post-clitelliar region: (a) form 1 - very dark, (b) 2 - dark, (c) 3 - medium, (d) 4 - light, (e) 5 - very light, (f) - individual of the form 2 with marked region of the body (somite 14-15) taken into consideration in the analysis.

A total of 583 individuals of E. octoculata were sampled between 2007 and 2009 in 18 freshwater environments in Poland: rivers, streams, channels, lakes and ponds, differing in terms of their bottom substrate (Table 1). Leeches were sampled manually from stones and with sweep-net from macrophytes and silt. Animals were preserved in 10% ethyl alcohol and after one hour in 80% ethyl alcohol. Selected animals were photographed under magnification c. 100 ×, alive and after preservation. On the basis of the photographic data-base, the sampled individuals were classified into five morphological forms (morphotypes), distinguished mainly on the basis of the area covered by dark pigment on the dorsal surface of the post-clitellar region (measured on somites 14-15) (Fig. 1a-f). These morphological forms are characterised as follows:

The differences between different types of environments and between different types of bottom substrates in proportion to particular morphological forms and in mean proportion of pigmented area on the dorsal surface were determined. Statistical significance of the differences in proportions was tested with Chi2 tests, while those in the mean pigment coverage of the body was tested with one-way ANOVA and post-hoc Tukey’s test.