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BioImages: The Virtual Field-Guide (UK)
Cornelius, P.F.S., 1995
North-West European Thecate Hydroids and their Medusae
This group includes Obelia geniculata, (familiar to those who did traditional A-level Biology!) and the other thecate (ie case-inhabiting) hydroids of our shores. The stringy growths of the hydroids are often found on the sides of tidal pools, especially if large and shaded, but the medusae of the alternate generation are free-swimming plankters and rarely seen unless sampled for from boat. This is a great shame as they are beautiful objects and often surprisingly large - several centimetres diameter.
The two volumes key c.120 species of hydroids, using an illustrated introductory key of the familiar "AIDGAP" form, followed by keys to genera and species. For medusae, a pictorial key is offered, p86-87, to be used in conjunction with the superfamily and family definitions, followed by various genus or family keys and tables (see p85). The checklist, introductory hydroid key and pictorial medusa key are repeated in the second volume.
Some species are very common, but many are rare and little known. Detailed descriptions summarise what is known for each. Both medusa and hydroid are generally illustrated.
| Publisher |
Field Studies Council (FSC) |
| Volume |
50, parts 1 & 2 |
| Pages |
347+386 |
| ISBN |
1 85153 254 4 |
| Edition |
1 |
| Coverage |
All the North-West European species known at the time. |
| Illustrations |
Line drawings accomppany the text. |
| Identify |
Under a Compound Microscope (also useful to examine under a Stereo Microscope). |
| Specimen Prep. |
Medusae: narcotised (eg gradual addition of formalin)
Hydroids: as above, or menthol crystals for several hours.
Staining may also be needed, unless phase contrast (or better, interference microsopy) is available.
Long term reservation requires care - se p 57-8. |
| Difficulty |
Meduae are said to be a challenge!. |
Malcolm Storey
Taxonomic Scope
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