Sentence:  The Middle East is an area of complex tectonic history through time, and this complexity is reflected in the biogeography of the region. Essentially, six historico-biogeographical 'strata' can be recognized among the crustaceans which inhabit the region. These are: [...] 6) <WSD>Lessepsian</WSD> migrants between the Mediterranean and Red Seas after the opening of the Suez Canal. 
Meaning of the word marked with <WSD> tags:  Of or relating to organisms that migrate from the Red Sea to the eastern Mediterranean Sea by means of the Suez Canal.