Planktonic spermatophores found in a culture device with spionid polychaetes

Kurzfassung

Aus Evertebratenlarven, die als Futter fürPleurobrachia pileus (Ctenophora) in einen „Planktonkreisel“, ein Hälterungssystem mit Sandinnenfilter, gebracht worden waren, entwickelte sich eine hauptsächlich aus Polychaeten bestehende Bodenfauna. Von dieser wurden pelagische Spermatophoren abgegeben, die nach den erhaltenen Kriterien (Bestimmung des am Ort der Spermatophorenabgabe gefundenen Polychaeten, Form der Spermien) vonSpio filicornis (Spionidae) stammten. Die Beobachtungen konnten nicht wiederholt und die Spermienaufnahme durch andere Polychaeten nicht beobachtet werden. Indirekte Spermatophorenübertragung ist bisher im marinen Bereich nur bei Halacariden beschrieben worden.

Summary

1. During culture experiments with marine invertebrates pelagic spermatophores were detected which looked like transparent toy baloons of 1.6 mm diameter. They were extremely fragile, which may account for the lack of previous reports.

2. The spermatophores never appeared singly. 10 of them were seen emerging from the sand at a place where the spionidSpio filicornis was living.

3. The shape and size of the spermatozoa conform to those of related spionids, which have spezialized organs assumed to be capable of producing pelagic spermatophores; while mating experiments were not conclusive, evidence suggests that the spermatophores were indeed the product ofSpio filicornis.

4. Therefore it is expected that at least this spionid polychaete uses the indirect transfer of spermatophores in order to assure the fertilization of its eggs. The only group of marine organisms from which a similar behaviour is known are members of Halacarida.