FIRST RECORD OF A FISH PARASITE APOROCOTYLE SIMPLEX ( DIGENEA ) FROM THE POLISH EXCLUSIVE ECONOMIC ZONE OF THE BALTIC SEA

One specimen of Aporocotyle simplex Odhner, 1900 (Digenea: Sanguinicolidae) was confirmed in 2004 from the branchial artery of a dab, Limanda limanda (Linnaeus, 1758), from the Gulf of Gdańsk. This work provides a partial description and a few morphological measurements of that specimen. This is the first record of A. simplex from Poland.

The range of dab, Limanda limanda (Linnaeus, 1758) (Actinopterygii: Pleuronectidae) covers the European Atlantic coasts and stretches into the Polish Exclusive Economic Zone of the Baltic Sea.There are only two Polish publications dealing with parasites of dab (Markowski 1933, Rolbiecki 2004).
In 2004, nine dab specimens (221-224 mm, 154-197 g) were captured from the Gulf of Gdańsk, Poland and examined for parasites.One live specimen of Aporocotyle simplex Odhner, 1900 (Fig. 1), infecting the branchial artery of the second gill arch, was recovered.The parasite was preserved in hot 70% ethanol, stained with Gowers alum carmine, dehydrated in 90% acetic acid, cleared in benzyl alcohol, and mounted in Canada balsam.It was deposited in the Division of Invertebrate Zoology, University of Gdańsk.This is the first record of A. simplex in Poland.
This specimen corresponds to previous descriptions (e.g., Thulin 1980a).Specimens of Aporocotyle simplex infecting dab are shorter than those infections American plaice, Hippoglossoides platessoides (Fabricius, 1780).Based on the published literature the vitelline follicles in specimens of A. simplex from dab should be less developed than those from American plaice (Thulin 1980a(Thulin , 1991)), but the present specimen had vitelline follicles that are well developed and surrounding the intestine.
Blood flukes, including Aporocotyle simplex, can harm the host fish by damaging the gills and consequently compromise the respiration.Adults and eggs can occlude blood vessels, leading to thrombosis, hyperplasia, epithelium hypertrophy, and, consequently-gill necrosis.Infected, fish can have granulomatous nodules in the branchial cavity epithelium and the heart of infected fishes can have cercariae and/or schistosomule larvae (Thulin 1991).
Aporocotyle simplex is a marine species using either of the terebellid polychaetes Artacama proboscidea Malmgren, 1865 or Lanassa nordenskioeldi Malmgren, 1866 as intermediate hosts (Køie 1982, Køie andPetersen 1988), and flatfishes as the most commonly reported definitive host (Thulin 1991).Due to the lack of those species of polychaetes in the Baltic Sea would seem that the fluke using another annelids in that area, or A. simplex was introduced here in dab from the region of the North Sea.