Table 3 Dichotomous molecular identification key to species of the genus Marenzelleria in the Baltic Sea using RFLP method

1. PCR product size amplified by LCO 1490 and HCO 2198 primers is about 709 bp or using HCO 709 primer 719 bp

2

2a. PCR product digested with ApaI enzyme gives the following restriction pattern (in base pairs; Fig. 2): 309 and 400

M. viridis

2b. PCR product remains uncut

3

3. PCR product size amplified by 16Sar and 16Sbr primers is about 545 bp

4

4a. PCR product digested with SspI enzyme gives the following restriction pattern (in base pairs; Fig. 2): 227 and 318

M. neglecta

4b. PCR product remains uncut

5

5a. PCR product digested with AseI enzyme gives the following restriction pattern (in base pairs; Fig. 2): 237 and 308

M. arctia

5b. PCR product remains uncut

6

6. Repeating of the procedure or sequencing of PCR product of either 16S, COI or Cytb is required! There are several possibilities why no cut is visible: either this individual has lost the restriction site by point mutation or it is another species of Marenzelleria (M. wireni or M. bastropi)^a