Q1: I don't expect a positive identification from the attached pictures, but is it reasonable to label this amphipod as probable (or possible) juvenile Jassa falcata? Or is there a visible feature that rules out this sp.?
Q2 I have used the incomplete key in Hayward & Ryland's Handbook. Many features I can not discern; should specimens be stained for examination, & with what? I examined this in a drop of alcohol on a microscope slide with a depression, but it kept evaporating, and air bubbles entered the specimen - any advice gratefully received.
Here are the features I think I could see (Binoc microscope up to X56):
Body laterally compressed, smooth dorsum
On antenna 1 the peduncle article 3 is more than half the length of article 2.
Rostrum absent. Gnathopods subchelate. Telson fleshy.
Jassa falcata juvenile because:
dorsum 3mm, antennae 1 mm (adults are 7mm according to H&R)
Body yellow grey strongly marked reddish brown.
Small black round eyes.
Common at LWS at Menai Bridge, Anglesey 13 Aug 2010 in tube on hydroid.
Q3 Is the tube made of a secreted substance, gathered material or a mixture?
Q4 When in its tube, it waves its antennae a bit like the cirri on a barnacle. Is this a feeding or breathing action?
I have cleaned distracting debris from the background of the picture but not up to the edge of the body or between the setae (right term?) on the antennae.
Many thanks for any answers.
Q1: In my opinion Your determination of Ishyroceridae family is correct. But there in England some other species of Jassa could be found, as well as of Parajassa, or Ischyrocerus itself. So some additional characters are needed to identify the genus and the species of Your specimens. You'd better use the book by Lincoln (Lincoln RJ (1979) British Marine Amphipoda: Gammaridea. British Museum (Natural History), London, 658 pp).
Q2: Amphipods should be preserved in 50% alcochol or 5% formaldehyde solution. Or in butanol, if you want to keep coloring. It's easier to examine a specimen in a Petri dish or something similar using preparation needles (I make them of entomological pins) and a forceps. In most cases for precise determination your need to prepare mouthparts or legs in glycerin on a slide (without depression). It's useful to keep a specimen in glycerin for several days before this procedure to make the cuticle more transparent, which is important in microscopy.
Q3: The tubes of corophioids are typically made of gathered material sticked with a secret. But I don't know the true state of this case.
Q4: Feeding. They use pleopods for breathing.
Zdrastye Stas, Spasibo za pomoshch.
Many thanks for answering all my queries so fully, much appreciated.
Sadly, I can not open djvu files, but as it is 50 years since I tried to learn Russian at school, I expect I would find the CCCP key slow work. But thanks for trying to provide me with it. I shall look up Lincoln.
My main interest is Opisthobranch mollusca, so perhaps I should be satisfied to know just what group other shore finds are in.