Found this pair of Bopyrids in a sample also containing Upogebia deltaura, Callianassa subterranea and Pisidia longicornis. Unfortunately the host is unknown for it was detached. Both Upogebia and Callianassa were fallen apart so it is either of them. What struck me in the female were the 2 large anal appendages and the 2 separate scales covering the head. The male (probably a juvenile) has 2 small eyes at the back of the head, a tuft of hairs at the distal article of the antenna and the last 6 abdominal segments has lateral appendages. They were found in the Cleaverbank, a part of the Dutch North Sea containg lots of coarse sand and pebbles at 2.viii.2015. They look a bit like Ione thoracica but the pair of scales on top of the females' head is bothering me.
Hi Ton,
in samples we analysed from the North Sea we identified a couple of times species of the genus Pseudione (borealis and callianassae). The pictures you attached seem to me similar to P. borealis.
Best wishes
Michael
The male doesn't look like any Pseudione borealis we have seen. In our specimens none of the males has lateral appendages unlike this specimen. However it may be a juvenile male? If this is the case Pseudione I will believe. I have never heard of P. callianassae. What are the discriminating features to separate them from P. borealis?
The difference between both species are e.g. the distal appendages of the females: in borealis with tubercles or knops and smooth in callianassae, a third one (hyndmanni) the lateral appendages are folded. However, I'm not an expert of this special group only rarely sampled (by coincidence). There exist several other species. Maybe a closer look will bring more knowledge, picture determination is always difficult. If you are interested, we could send you our material?
We have found on numerous occasions Pseudione within Callianassa. In almost every sample containing C. subterranea there was at least 1 individual with Pseudione or Ione underneath the carapax. In a key on Dutch aquatic isopods (Huwae & Rappe 2003) there are only 2 species parasitic on C. subterranea i.e Ione thoracica and P. borealis which appear to be common in the Dutch North Sea. Reading the revision by Bourdon (1968) P. callianassae is regarded a nomen nudum for only the head of the male is depicted. Sars (1898) mention some other Pseudione (e.g. affine, hyndmanni) and Naylor (1972) only reported hyndmanni from Britain but clearly states that Pseudione is in need of revision. So I'm not even sure which species we have. Worms regards borealis, hyndmanni, affinis and callianassae all as good species, but I have my doubts. I even think that many species descriptions are based on immature and mature males/females and that some of the names are synonyms. For now I follow Huwae & Rappe (2003) untill a revision of the genus is conducted.
o.k. could you please send me a pdf of the paper of Huwae & Rappe
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