EVENTS

Members Reports and Photos

SATURDAY 1st march  2014  

 PRAEGER CENTRE, National botanic gardens     

LEADERs: maria long & declan doogue

Morning session: Maria Long: The Vertigo snail family

Ireland has some good legislation supporting the conservation of wildlife, and natural habitats. Indeed complaints from landowners and developers would lead one to the impression that the commercial development of the entire country is stymied by those of us (do-gooders and tree-huggers) interested in the well-being of our naturally-occurring plants and animals, and the places they need for survival.  

In fact it is a relatively rare occurrence for an infrastructural or commercial project to be seriously affected by the enforcement of conservation legislation. Two unconnected famous occasions when this did happen were when a major road scheme through County Kildare and a commercial recreational development in County Clare fell foul of tiny Whorl Snails of the family Vertigo.  

Maria Long has taken part in several studies and surveys of these and gave us a ‘Praeger Day’ morning introduction to them on March 1st 2014.  We have eight species of Vertigo in Ireland, and all but two are in real danger of extinction, mostly due to draining of their habitat and all are considered ‘rare’ though some are relatively widespread.  

Many of these species are found in wetland habitats, some preferring wet flushes, other swamps or fens. Some species are even found on shaded rocks and walls, where they should not be confused with young Lauria or Leiostyla species among others whose adults are much bigger. The fully-grown adult Vertigos are usually about 2–3 mm in size, so they are not easy to see with the naked eye unless you are lucky and come across one that is on the move. Sieving moss and detritus from the margins of water-bodies and hand-searching at the base of reed-beds are probably most effective methods of finding them. In Autumn Vertigo moulinsiana climbs high up reeds and may be found there.  

Maria explained that naming these endearing little creatures to species level is possible using a good handlens and a lot of experience and habitat knowledge, but it is usually preferable to get them under the microscope

Features of the shell are used: whether they coil sinisterly or dextrally, the shape of the opening or mouth, the number and positioning of ‘teeth’ around the mouth, as well as the relative size of the whorls and the nature of any sculpturing on the surface. Colour can also be used, but less reliably.  

Afternoon Session: Declan Doogue:  Capturing and identifying water-snails

Declan explained how the recent flooding of river valleys following the very wet winter, provide an opportunity to sample the fauna, especially the fresh-water molluscan fauna of the rivers. Debris from the river margins and beds is washed up and ‘beached’ at areas where the river bends or meanders or otherwise loses its ability to carry debris. Among the deposits will be found a large amount of ‘dead’ snail-shells which being light is carried well up onto dry land. Samples can be gathered for later drying.  

The dried-out flotsam can be put through a series of different-sized sieves. The material captured at each sieve is examined for snail-shells and other molluscs which can be saved for later identification. The most interesting small snails and bivalves are often found by examining the final, finest sample that makes it all the way through the sieves. This should be examined using good light and some sort of magnification.  

Declan and some members had brought along some samples and these were sieved and examined to demonstrate the technique.  

The main disadvantages to this method are that although you can be reasonably sure that all of your specimens lived in the river or its close environs, it is not useful for mapping schemes based on a grid system as you cannot ascertain how far any specimen has been swept along the river. This and sorting that occurs by water-transport makes even relative studies in population values impossible to interpret.  

As a tool to collect samples of water molluscs to be used for teaching or learning, however, it is a very easy to use method. But beware of land snails that might have fallen in while alive, or been gathered by the flood along the ‘dry-land’ floor of the river valley!

Gerry Sharkey

     

Atlas of Molluscs        Freshwater Bivalves            Non-Marine         Freshwater Bivalves


   

Aquatic Snails               Planorbis carinatus                                 Lymnaea stagnalis

   

Lymnaea peregra                                 Royal Canal                   Land Snails

 

                     Discus rotundatus     Vertigo shell nomenclature

     

                         Columella aspera (top) & C. edentula (bottom)                         

 

A                                 B

A. Vertigo substriata (left) & V. pygmaea (right) B. Vertigo moulinsiana (left) & V.antivertigo (right)

      

  Leiostyla anglica (top) & Lauria cylindracea (bottom)

 

Photos ©  P Lenihan 

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