(DRAFT) - Taxonomy
Species SNAIL, STOCK ISLAND
Species Id ESIS354001
Date 13 MAR 96
TAXONOMY
NAME - SNAIL, STOCK ISLAND
OTHER COMMON NAMES - SNAIL, STOCK ISLAND;SNAIL, TREE and STOCK ISLAND
ELEMENT CODE -
CATEGORY - Aquatic Molluscs
PHYLUM AND SUBPHYLUM - MOLLUSCA,
CLASS AND SUBCLASS - GASTROPODA,
ORDER AND SUBORDER - STYLOMMATOPHORA,
FAMILY AND SUBFAMILY - BULIMULIDAE,
GENUS AND SUBGENUS - ORTHALICUS,
SPECIES AND SSP - RESES,
SCIENTIFIC NAME - ORTHALICUS RESES
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
Stock Island Snail
Orthalicus reses (Say, 1830)
KINGDOM: Animal GROUP: Snail
PHYLUM: Mollusca CLASS: Gastropoda
ORDER: Stylommatophora FAMILY: Bulimulidae
A large ovate-conical tree snail. Adults attain a length of 35-
60 mm and are about 0.54-0.60 times as wide as high. The umbilicus is
imperforate. The shell is thin and weakly translucent. The whorls
slightly rounded and regularly increase in size to a total of 7 whorls
with a modestly impressed suture. The shell is glossy to chalky with
distinct, irregularly impressed incremental striations. The aperture
is ovate in shape. The plane of the aperture lies at an angle of
about 25 degrees to the shell axis in lateral profile (07).
The embryonic whorls are white to cream in color. The following
whorls are white to cream with several irregular, gray-brown or purple
brown vertical flames. Generally the flames are not forked near the
upper suture, in contrast to the subspecies O. r. nesodryas Pilsbry,
1946, which has forked flames. The last whorl or two sometimes has
2-3 faint narrow, brown, spiral bands. In addition there are 1-4 dark
brown varices on the shell, which occur at irregular intervals (a
Taxonomy - 1 (DRAFT) - Taxonomy
Species SNAIL, STOCK ISLAND
Species Id ESIS354001
Date 13 MAR 96
varix is a dark vertical band produced at a growth-rest stage). The
interior of the shell is white, but distinctly shows the external
markings through the translucent shell. The callus across the
parietal wall of the aperture is thin and clear to faintly chestnut in
color (in contrast to O. r. nesodryas, which has a dark brown parietal
callus) (07).
Synonyms:
Bulimus undatus (Bruguiere) reses Say, 1830. (04)
Orthalicus undatus var. B, Shuttleworth, 1856. (05)
Orthalicus undatus (Bruguiere) Binney, 1878. (01)
Oxystyla undata reses (Say), Pilsbry, 1899. (02)
Zebra undata reses (Say), Strebel, 1909. (06)
Orthalicus reses reses (Say), Pilsbry, 1946. (03)
Holotype specimen of Orthalicus r. reses (Say, 1830): originally
in the Academy of Natural Sciences, Philadelphia, but lost in 19th
century. Neotype: Academy of Natural Sciences, Philadelphia;
designated by Pilsbry, 1946:34 (03).
Taxonomy - 2 (DRAFT) - Status
Species SNAIL, STOCK ISLAND
Species Id ESIS354001
Date 13 MAR 96
STATUS
Coded Status
Florida; Federal Threatened
Florida; Officially Listed
T: Federal Threatened
Non-consumptive recreational
Ornamental
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The Stock Island tree snail (Orthalicus reses) has been
designated a Threatened species pursuant to the Endangered Species Act
of 1973 (50 CFR 17.11; P.L. 93-205, 87 Stat. 884; 16 U.S.C.
1531-1540), as amended. The species has this status wherever found
including the State of Florida.
This species is protected by the Lacey Act (P.L. 97-79, as
amended; 16 U.S.C. 3371 et seq.) which makes it unlawful to import,
export, transport, sell, receive, acquire, or purchase any wild
animal (alive or dead including parts, products, eggs, or offspring):
(1) in interstate or foreign commerce if taken, possessed,
transported or sold in violation of any State law or
regulation; or
(2) if taken or possessed in violation of any U.S. law,
treaty, or regulation or in violation of Indian tribal law.
It is also unlawful to possess any wild animal (alive or dead
including parts, products, eggs, and offspring) within the U.S.
territorial or special maritime jurisdiction (as defined in
18 U.S.C. 7) that is taken, possessed, transported, or sold in
violation of any State law or regulation, foreign law, or Indian
tribal law.
RESPONSIBLE FEDERAL AGENCIES:
USFWS -Responsible for the management/recovery, listing, and
law enforcement/protection of this species.
NPS -Responsible for the law enforcement/protection of this
species with applicable State and Federal laws on
public lands under their control. Also responsible
for conservation (Nat. Park System Organic Act - 16
U.S.C. 1, 2-3)/management/recovery on National Park
Service lands. Taking, possessing, or disturbing of
Federally listed species is prohibited on NPS lands
(36 CFR 2.1, 2.2, and 2.3).
All Federal agencies have responsibility to ensure that any
action authorized, funded, or carried out by that agency is not likely
to jeopardize the continued existence of the species or result in the
destruction or adverse modification of Critical Habitat (50 CFR 402),
and to utilize their authorities to carry out programs for the
conservation of the species.
Status - 1 (DRAFT) - Status
Species SNAIL, STOCK ISLAND
Species Id ESIS354001
Date 13 MAR 96
STATE STATUSES AND LAWS:
STATE: Florida
DESIGNATED STATUS: Endangered
ADMINISTRATIVE AGENCY: Game and Fresh Water Fish Commission
STATE STATUTES: Florida Endangered and Threatened Species Act of
1977, Section 372.072.
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
None.
ECONOMIC STATUSES:
Occasionally collected for shell specimens.
76/04/28:41 FR 17742/17747 - Proposed rule
78/07/03:43 FR 28932/28935 - Listed as Threatened
83/12/08:48 FR 55100/55102 - Five year review
Status - 2 HABITAT ASSOCIATIONS
HABITAT - TERRESTRIAL
TERRESTRIAL
LAND USE -
Residential
Commercial and Services
Industrial
Deciduous Forest Land
COMMENTS ON HABITAT ASSOCIATIONS -
The species lives on trees and shrubs in tropical hardwood
hammocks. It is found on a large diversity of tree species, including
some exotics such as the mango tree, Piscidia piscipula (Jamaican
Dogwood), and Acacia sp. It will not live on the introduced Brazilian
pepper tree, Schinus braziliensis, which forms large thickets on Stock
Island (07).
The snail occurs on both smooth and rough-barked trees. It
aestivates in large trees with cavities and sheltered bowls. It
requires a loose soil rich in organic material for egg deposition.
The species can survive in very small groves of only a few square
yards in area, and in new growth or second growth thickets.
Habitat Associations - 1 (DRAFT) - Food Habits
Species SNAIL, STOCK ISLAND
Species Id ESIS354001
Date 13 MAR 96
FOOD HABITS
TROPHIC LEVEL -
HERBIVORE
LIFESTAGE FOOD FOOD PART
General Bacteria
General Algae
General Myxomycophyta
General Parasitic/Epiphytic Plants
Food Habits - 1 (DRAFT) - Environment Associations
Species SNAIL, STOCK ISLAND
Species Id ESIS354001
Date 13 MAR 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G
G Coastal Features: Rocky offshore islands
G Coastal Features: Sandy offshore islands
G Coastal Features: Vegetated offshore islands
G Tree Cavities: Unknown
Environment Associations - 1 (DRAFT) - Life History
Species SNAIL, STOCK ISLAND
Species Id ESIS354001
Date 13 MAR 96
LIFE HISTORY
FOOD HABITS:
The only available information on food habits is based on the
gut contents of four adult specimens collected in August, 1982. The
snail grazes on minute fungae and algae that grow as epiphytes on tree
leaves and stems. Identified gut contents include basidiospores,
Aureobasidium-like fungae, mycelial fragments and algae
(unidentified). Bacteria are also consumed, but it is not known if
these are a food item or a contaminant (07).
HOME RANGE/TERRITORY:
This species is non-territorial. The only aspect of homing
behavior that has been observed is the tendency for specimens to
return to the same tree cavity to aestivate. For variable short
periods a snail may return to the same limb, bole or fork in a tree to
rest between foraging activities. However snails frequently change
their resting location on a tree, and frequently move to new trees
(07).
PERIODICITY:
The species is seasonally active. It is dormant in aestivation
during the dry season, usually December - May. In June snails become
active throughout the wet season, although intermittent dry period
may cause the species to return to aestivation sites, or aestivate
directly on the surface of large limbs. During wet weather the snail
is most frequently active at night, but may be active in the daytime
as well (07).
MIGRATION PATTERNS:
Non-migratory.
COVER/SHELTER REQUIREMENTS:
The species inhabits subtropical hardwood hammocks.
It apparently shows no host tree preference. It is found on smooth-
barked and rough-barked trees. It is found on a particular species of
tree in direct proportion to the abundance of that tree at a given
station. It is most common in mature hammocks, but occurs in second
growth and new growth thickets. As many as 14 snails have been found
on a single tree. It aestivates in tree cavities that are
sufficiently large for the snail to enter. A significant natural
mortality occurs when tree growth decreases the size of the opening
and traps aestivating specimens within (07).
REPRODUCTIVE SITE REQUIREMENTS:
Nests are constructed in soft dirt that is rich in leaf-mold
directly at the base of the host tree. The nests are excavated
initially with the posterior part of the snail foot to about 20 mm
deep. After excavation the snail turns around and inserts the
anterior head foot in the cavity, and continues to excavate the
cavity to a depth of 40-60 mm (07).
REPRODUCTIVE CHARACTERISTICS:
Life History - 1 (DRAFT) - Life History
Species SNAIL, STOCK ISLAND
Species Id ESIS354001
Date 13 MAR 96
Mating was observed in September, 1982. The species is
hermaphroditic and sequential reciprocal mating takes place. The
complete mating process takes about 12 hours. The species begins
mating at one year of age. Data are not available on multiple matings
or numbers of nests constructed per year. Nest building also takes
place in September shortly after mating. The eggs hatch the following
June (07). About 8 to 21 eggs are laid per nest. Eggs are covered by
soil as the snail crawls out of the nest.
PARENTAL CARE:
No parental care occurs.
POPULATION BIOLOGY:
The species thrives best in mature tropical hardwood hammocks.
Area of forest cover and aestivation sites seem to be limiting
factors. Food supply exceeds population needs. There is no direct
competition with other species of snails for food. Data are not
available on survival rates or mortality rates. It is preyed upon by
racoons, oppossums, rats, cats, centipedes, spiders, amblypygids,
and is collected or wantonly destroyed by people. The snails reach
adult shell size (35mm) in one year. They survive for up to six
years. They reproduce from years 1-6.
SPECIES INTERRELATIONSHIPS:
The most obvious direct causal relationship that the Stock Island
tree snail has with other species is as a prey item. Racoons,
oppossums, cats, bluejays, crows and humans seem to be the principal
predators. Larval flies of the family Sarcophagidae parasitize the
snail and cause considerable mortality. The species inhabits a large
number of tree species, and is not host specific. It feeds on
microscopic epiphyte algae and fungae growing on the trees, but data
are not available concerning more specific food dependence (07).
OTHER LIFE HISTORY DESCRIPTORS:
None.
Life History - 2 (DRAFT) - Management Practices
Species SNAIL, STOCK ISLAND
Species Id ESIS354001
Date 13 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Selective Thinning
Beneficial Restricting/regulating human disturbance of populations
Beneficial Maintaining undisturbed/undeveloped areas
Beneficial Controlling/Restricting Pesticide Use
Beneficial Controlling/Removing Nonnative Vegetation
Beneficial Transplanting wild animals
Beneficial Restricting Poaching
Adverse Harassment/Vandalism/Indiscriminate Killing
Existing Harassment/Vandalism/Indiscriminate Killing
Adverse Climate Alteration
Existing Climate Alteration
Adverse Poaching
Existing Poaching
Adverse Collecting
Existing Collecting
Adverse Low Gene Pool
Existing Low Gene Pool
Adverse Parasites
Existing Parasites
Adverse Predation
Existing Predation
Adverse Rural Residential/Industrial Areas
Existing Rural Residential/Industrial Areas
Adverse Recreational development
Existing Recreational development
Adverse Grazing
Existing Grazing
Adverse
Existing
Adverse Forest Alteration
Existing Forest Alteration
Adverse Harvesting
Existing Harvesting
COMMENTS ON MANAGEMENT PRACTICES -
The Stock Island tree snail originally was confined to Key West
and Stock Island, Monroe Co., Florida (07). Much destruction of the
native forest occured in the nineteenth and early twentieth century
because the islands were used for grazing cattle and urbanization
(03). Much of the islands have been urbanized during recent years
(07). An 18 hole golf course (Key West Golf Course) was built on
Stock Island in the late 19th century, thereby encroaching further on
the native forest (07). Cats and rats prey upon Stock Island snails
(07). Larval flies of the family Sarcophagidae parasitize the snail
and cause considerable mortality. Some collecting for shell specimens
continues, and some local individuals deliberately destroy live
specimens (07). The golf course is currently being converted into a
multiple dwelling residential complex (07). About 200 individuals
Management Practices - 1 (DRAFT) - Management Practices
Species SNAIL, STOCK ISLAND
Species Id ESIS354001
Date 13 MAR 96
survived in 1983 on Stock Island. In 1986, only 50-100 remained
(08,09) on Stock Island. The species is extirpated from Key West.
APPROVED PLAN:
U.S. Fish and Wildlife Service. 1982. Stock Island Tree Snail
Recovery Plan. U.S. Fish & Wildlife Service, Atlanta, GA. 17 pp.
The Recovery Plan assumed that the snail could be maintained
at the Stock Island site indefinitely, and that reintroduction
into suitable sites in the City of Key West was possible.
Subsequently, the snail has declined seriously at the remaining
Stock Island sites and it has not been possible to locate
promising reintroduction sites in Key West. A July, 1986 survey
(08) indicated that only 50-100 sbauks renaubed ib Stock Island,
down from 214-321 in August 1982. The causes of the decline are
not certain but fragmentation of hardwood hammocks, changes in
microclimate, and increased predation have been suggested (09).
It now appears that it will not be possible to maintain or
enhance the Stock Island populations. The best alternative
appears to be locating suitable hardwood hammocks on off-road
keys in National Key Deer Refuge and introducing the Snail there.
This assumes hammocks lacking the conspecific Orthalicus reses
nesodryas can be located.
Management Practices - 2 (DRAFT) - References
Species SNAIL, STOCK ISLAND
Species Id ESIS354001
Date 13 MAR 96
References
***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****
01 Binney, W. G. 1876. The terrestrial air-breathing mollusks of the
United States and adjacent territories of North America. Boston:
1-439.
02 Pilsbry, H. A. 1899. Manual of conchology, Series 2, 12:1-258.
Philadelphia.
03 Pilsbry, H. A. 1946. Land Mollusca of North America (north of
Mexico). Monogr. Acad. Nat. Sci., Phila., 2:1-520.
04 Say, T. 1830. Descriptions of some new terrestrial and fluviatile
shells of North America. New Harmony Disseminator of Useful
Knowledge, New Harmony, IN. Pages 1-46.
05 Shuttleworth, R. J. 1856. Notitiae Malacologicae oder Beitrage
zur nahern Kenntniss der Mollusken. 1:63-64.
06 Strebel, H. 1909. Revision der unterfamilie der Orthalicinen.
Jahrbuch der Hamburgischen Wissenschaftlichen Anstolten (Beiheitz),
26:1-191.
07 Thompson, F. G. and J. Deisler. Unpublished data. In press.
08 Sunderland, K. 1986. Orthalicus reses reses survey on Stock
Island, Monroe County, Florida. Unpubl. Report to the Nature
Conservancy. 50 pp.
09 Deisler, J.E. 1986. Deisler, J.E. 1986. Unpubl. Report to
the Nature Conservancy. 3 pp.
***** REFERENCES FOR N-OCCURRENCE NARRATIVE ONLY *****
01 Thompson, F. G. and J. Deisler. Unpublished data. In press.
02 Pilsbry, H. A. 1946. Land Mollusca of North America (north of
Mexico). Monogr. Acad. Nat. Sci., Phila. 3(2):1-520.
References - 1