Pterotrachea coronata  (Forskål, 1775)
by Walter Jung and Maike Kussinn

   

e started diving in 1993, had our course in Germany and finished it with the Bronze brevet of VDST (equivalent to CMAS *). Diving in Germany means for us to go into a dark and cold gravel pit. Whom it surprises: We wanted to have a look for ourselves to all the wonderful things in the sea which the other divers of our diveclub "TG Mölln" were adoring. So we decided to go to the Costa Brava (Spain) in autumn.

We were the proud owners of a beautiful, multicolored caravan, and it was a joy to drive and dive the coast up and down. We admired enormous groupers in L'Estartit, large sea-hares in Tamariu, large and small octopus, Spanish lobsters, electric rays, congers, lobsters, etc.

Because we found everything so wonderful, we go frequently to this beautiful coast. We even inspired some diver friends to go to this diving area. We became so used to the idea, that in October we all went to the Costa Brava.

Only that this year it would be different, because we travelled in spring, with the thought that perhaps there will be something else to see. And so was it. 

In Tossa de Mar we had the feeling of not diving in water, but in a fish egg soup. We were speechless. We had to push the egg strings away with our hands. Fulleaten fish chewed boringly the fish eggs around. 

And then, in Tamariu, occurred something that started us the idea of writting this small article. During a beach dive in the bay of Tamariu (Stolli's diving center) we could film and observe this strange organism in 5 m depth of water.

My buddy Maike Kussinn discovered it. It was my dive number 557 and the date was April 12, 1999. At first the animal layed quietly and looked as if it was asleep. While I rounded and filmed the animal, it seemed it to wake up and circled us, as if it was closely examining our equipment.

DESCRIPTION OF THE ANIMAL

It had a size about 30 cm long, with a diameter about 5 cm, sausage-like body, transparent like a jellyfish and button black eyes equipped with a long trunk. The animal moved with some transparent swimming fins under the body.

We described the organism to many local dive guides, but nobody could tell us a word about the animal, even approximately.

Only Dr. Peter Nahke brought clarity to the problem in July 1999: It belongs to the superfamily of the Atlantoidea, whose 3 families appear described in the Mediterranean. It is a pelagic slug, i.e. it constantly swims in middle waters far from the coast where it becames extremely rare.

Professor Dr. Dieter Adelung (Oceanographic Institute of the University of Kiel), in a letter to us, identified with a 90% confidence rate that it is a Pterotrachea coronata.

We are very interested in the underwater flora and fauna. We have many underwater films already made, e.g. from Ireland, France, Spain, Norway, Croatia, Denmark, Red Sea, Maldives, Cuba - but such an animal never came before our camera lens.

SYSTEMATIC CLASSIFICATION

• According to Check List of European Marine Mollusca
  
  Superclass: MOLLUSCA
  Class: Gastropoda (Cuvier, 1797)
  Subclass: Prosobranchia (Milne Edward, 1848)
  Order: Apogastropoda (Salvini, Plawen & Haszprunar, 1987)
  Suborder: Caenogastropoda (Cox, 1959)
  Superfamily: Firoloidea (Rafinesque, 1815)
  Family: Firolidae (Rafinesque, 1815)
  Genus: Pterotrachea (Forskål, 1775)
  Species: coronata (Forskål, 1775)
  
• According to Rupert Riedl's book: Fauna and Flora of the Mediterranean
  
  Tribe: Mollusca (soft animals) 
  Subtribe: Conchifera (bowl soft animals)
  Class: Gastropoda 
  Subclass: Prosobranchia
  Order: Caenogastropoda 
  Suborder: Mesogastropoda
  Superfamily: Atlantoidea
  Family: Pterotrachidae
  Genus: Pterotrachea
  Species: coronata (Forskål, 1775)

ACKNOWLEDGEMENTS

• All pictures are from a UW video by Walter Jung
• The classification first took place thanks to Dr. Peter Nahke
• Identified (with 90 % confidence) as Pterotrachea coronata by Prof. Dr. Dieter Adelung
• Report by Walter Jung and Maike Kussinn
• Erwin Köhler looked for the specification up to systematics and created the original web pages. 

DIRECTORY