How to differentiate the pink “flabellina”

Any diver with a certain experience searching for opisthobranchs in the Mediterranean Sea or NE Atlantic could tell you that, sometimes, it is pretty difficult to tell apart which species of pink “flabellina” you are looking at.

It’s not really that difficult, as long as you know what to look at in order to differentiate them. Here we include the main traits of the most common species:

Flabellina affinis has the following characteristics:

  • The distal end of cerata are always colored purple with a white cnidosac on the tip. The rest of the cerata are transparent and allow to see the reddish brown digestive gland inside.
  • The cerata are joined in groups emerging from pods growing on the animal’s body.
  • Rhinophores have many tight ringed lamellae.
Flabellina affinis by Miquel Pontes

Flabellina affinis by Miquel Pontes

Paraflabellina ischitana has the following characteristics:

  • Cerata are transparent and allow to see the brown to orange digestive gland inside, and have a white cnidosac on the tip. No purple tips as in Flabellina affinis.
  • The cerata are joined in groups emerging from pods growing on the animal’s body.
  • Rhinophores have some loosely ringed lamellae.
Flabellina ischitana by Miquel Pontes

Paraflabellina ischitana by Miquel Pontes

Edmundsella pedata has the following characteristics:

  • Cerata are transparent and allow to see the brown to orange digestive gland inside, and have a white cnidosac on the tip. No purple tips as in Flabellina affinis.
  • The cerata grow directly on the animal’s body, without the pods found in Flabellina affinis or Paraflabellina ischitana.
  • Rhinophores are smooth or wrinkled, but clearly without the ringed lamellae as in Flabellina affinis or Paraflabellina ischitana.
Flabellina pedata by Miquel Pontes

Edmundsella pedata by Miquel Pontes

Piseinotecus soussi has the following characteristics:

  • Cerata are transparent and allow to see the brown to orange digestive gland inside, and have a white cnidosac on the tip. There is a variable ammount of white dots sprayed on the ceratal surface which are absent in Edmundsella pedata. No purple tips as in Flabellina affinis.
  • The cerata grow directly on the animal’s body, without the pods found in Flabellina affinis or Paraflabellina ischitana.
  • Rhinophores are smooth or wrinkled, but clearly without the ringed lamellae as in Flabellina affinis or Paraflabellina ischitana. There is a variable ammount of white dots sprayed on the rhinophoral surface which are absent in the other species.
  • There are internal physiological differences that classify this species in the Piseinotecus genus, but we only state here the traits visible to a SCUBA diver.
Piseinotecus soussi by Enric Madrenas

Piseinotecus soussi by Enric Madrenas

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Miquel Pontes

Informàtic de profesió, és fotògraf submarí i naturalista aficionat. Submarinista des del 1994, el seu “logbook” compta amb unes 700 immersions al mar Mediterrani i als oceans Atlàntic, Índic i Pacífic. Ha participat i participa en tota mena de projectes divulgatius (llibres, revistes, webs, conferències, exposicions…) com a mitjà per difondre el seu interès principal: protegir els mars i els éssers que hi habiten. Fundador del Grup d’Estudis M@re Nostrum (www.marenostrum.org) Soci fundador del GROC (Grup Recerca d’Opistobranquis der Catalunya). Soci Fundador del VIMAR (Vida Marina). Va descobrir l’interessant mon dels opistobranquis el 1997 de la ma dels seus companys d’immersió i des de llavors ha estat una línia de treball continuada, aportant fotos submarines, observacions fetes al medi i donant suport informàtic per a la difusió d’aquests continguts.