Aestivating snails : 無料・フリー素材/写真
Aestivating snails / wallygrom
| ライセンス | クリエイティブ・コモンズ 表示-継承 2.1 |
|---|---|
| 説明 | Golden Beach, Thassos, Greece.I'm sure those snails don't move from one year to the next ... apparently it's a process called aestivation ... a sort of hibernation period when it's hot and dry.From Wikipedia -Aestivation is a state of animal dormancy, similar to hibernation, although taking place in the summer rather than the winter. Aestivation is characterized by inactivity and a lowered metabolic rate, that is entered in response to high temperatures and arid conditions. It takes place during times of heat and dryness, the hot dry season, which are often the summer months.Invertebrate and vertebrate animals are known to enter this state to avoid damage from high temperatures and the risk of desiccation. Both terrestrial and aquatic animals undergo aestivation. The fossil record suggests that aestivation may have evolved several hundred million years ago.Some air-breathing land snails, including species in the genera Helix, Cernuella, Theba, Helicella, Achatina and Otala, commonly aestivate during periods of heat. Some species move into shaded vegetation or rubble. Others climb up tall plants, including crop species as well as bushes and trees, and will also climb man-made structures such as posts or fences.Their habit of climbing vegetation to aestivate has caused more than one introduced snail species to be declared an agricultural nuisance.To seal the opening to their shell to prevent water loss, pulmonate land snails secrete a membrane of dried mucus called an epiphragm. In certain species, such as Helix pomatia, this barrier is reinforced with calcium carbonate, and thus it superficially resembles an operculum, except that it has a tiny hole to allow some oxygen exchange. |
| 撮影日 | 2010-08-17 12:14:21 |
| 撮影者 | wallygrom |
| タグ | |
| 撮影地 | Chrysi Ammoudia, East Macedonia and Thrace, Ελλάδα 地図 |
| カメラ | Canon PowerShot SX200 IS , Canon |
| 露出 | 0.001 sec (1/1000) |
| 開放F値 | f/4.0 |
| 焦点距離 | 5 mm |