Kanab Ambersnail- EP
From Glen Canyon Dam AMP
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CRE AT-RISK SPECIES VIGNETTES – Larry Stevens
- Kanab Ambersnail
- Federally endangered since 1991, the Kanab ambersnail [KAS; Oxyloma haydeni haydeni (kanabensis; Pilsbry 1948)] is a half inch-long, dextral (up-to-the-right-spiraling) landsnail with a high, delicate spire, and which only exists in three spring-fed wetlands in southern Utah and northern Arizona. Discovered in Grand Canyon during tributary monitoring at Vaseys Paradise in 1990, this hermaphroditic species has an annual life cycle.
- Eggs are laid in August, larval snails grow until mid-October, then overwinter by sealing themselves with mucous to stone, wood, or (often unfortunately) dead leaves, which may blow away.
- Those snails that survive the vicissitudes of winter emerge in March or April, complete their growth by mid-summer and breed.
- Those with female function lay several clutches of about 40 eggs in gelatinous masses on the undersides of moist stems and leaves.
- KAS feeds on biofilm on moist, dead stems of cardinal monkeyflower and other wetland plants, but they seem to prefer feeding on the tender new leaves of non-native watercress.
- About 10% of adult KAS at Vaseys Paradise are infected with a parasitic Leucochloridium flatworm, which evacuates from the snail in August and completes its life cycle in songbirds.
- Although common in Utah, only two other natural populations of Oxyloma ambersnails occur in Arizona, one at Leopard Frog Marsh at Mile -9L and the other at Indian Gardens on the Bright Angel Trail in central Grand Canyon.
- After scouring springtime floods were eliminated by Glen Canyon Dam in 1963, Vaseys Paradise vegetation cover expanded by about 40% to nearly an acre.
- The post-dam KAS population there is now likely substantially greater than it was in predam time.
- The endangered status of KAS has resulted in several Biological Opinions from the U.S. Fish and Wildlife Service regarding the impacts of planned high flow experiments.
- Actions to protect the Vaseys snail population have included: developing secondary, off-river KAS populations in tributaries; transporting all KAS in the mainstream flood zone to higher elevations; moving and protecting vegetation patches that support KAS; and monitoring flood impacts and among-year population variation.
- Detailed morphological and genetics analyses by the U.S. Geological Survey will soon propose synonomy of Kanab ambersnail into the more widespread and common North American Niobrara ambersnail taxon (Oxyloma h. haydeni Pilsbry 1948), thus Kanab ambersnails will soon no longer exist as a taxonomic entity.
