Phylum Mollusca in the Christopher B. Smith Preserve

Phylum Mollusca Characteristics: Phylum Mollusca is a very large phylum of aquatic and terrestrial invertebrate animals. Some mollusks have shells and other do not. Most have eyes; all have sensory organs that detect chemicals, vibrations, and touch. An unusual characteristic of mollusks is they have organs with multiple functions. For example, the heart and nephridia (kidney) are organs for circulation, excretion, and reproduction.

There are 85,000 living species, divided into 8 classes; two additional classes are extinct. Only one class, Gastropoda (snails and slugs,) is found at the Smith Preserve. Two species of terrestrial gastropods and one species of aquatic gastropod have been found.

Interactions in the Smith Preserve: Since mollusks eat detritus (tiny bits of decaying plants and organisms), they help clean their surroundings and recycle nutrients. Mollusks are an important part of the food chain, providing food for fish, small mammals, and birds. They also serve as intermediate hosts of animal parasites including worms and protozoa.

Class
Family
Species Name
Common Name
Gastropoda
Camaenidae
Zachrysia provisoria
Gastropoda
Unknown
Unknown
UnUnknown
Gastropoda
Physidae
Haitia sp.
 
Gastropoda
Unknown
Unknown

 

 

Zachrysia provisoria

Cuban Brown Snail / Garden Zachrysia

Zachrysia proviscoria is a non-native, air-breathing land snail of medium-size (25–30 mm width).

The individual in the first three photographs was observed crawling through leaf litter. As seen in these photographs, the Cuban brown snail shell is spherical in shape with 4 or 5 rapidly expanding whorls. The shell is translucent and the speckled black mantle shows through the shell. As seen in the photograph below of a dead individual, the shell has many pronounced curved ribs.

The species is thought to have been released to the Miami area in the 20th century and migrated from there. Today, it is the most common of the large terrestrial snails in southern Florida and it is considered an invasive species that could negatively affect agriculture and natural ecosystems. It is a serious pest of tropical fruit and citrus, most ornamental plants, and vegetable plants.

 

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Unknown species

Unknown Common Name

On December 29, 2014, these two very small snails were living in pine needle litter beneath a Pinus elliottii densa (Southern Florida Slash Pine) in the central-western section of the Smith Preserve. They were isolated from the litter with a Berlese funnel and these photographs were created using photomicroscopy.

The first specimen was .75 mm in diameter. The second was 1 mm in diameter.

The taxonomic identity of these snails is unknown.

These snails were likely consuming rotting leaf litter, fungi, and soil. Their diet needs to be rich in calcium and other nutrients to support the growth and repair of their shells.

 

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Haitia sp.

Physa Freshwater Snail

This specimen was collected with a net in the Smith Preserve pond on November 19, 2013. Identification was determined by using the online website "An Identification Manual For The Freshwater Snails of Florida," by Fred G. Thompson, Curator of Malacology, Florida Museum of Natural History, University of Florida, Gainesville, Florida, 32611-7800.

Since this specimen, has no operculum, it belongs to Subclass Pulmonata. Members of this subclass have the ability to breathe air with a simple lung instead of a gill or gills.

As shown in these photographs, the shell of this individual appears to have four whorls. Because the shell is coiled to the left (sinistral), it is classified as a member of Family Physidae. Members of this family have a complex of muscles that is unique. The complex, called "physid musculature,"permits physids to rapidly flick their shells side to side and escape predation. Members of the family have a long, large aperture and a pointed spire. The shells are thin, horn-like, and somewhat transparent.

This individual may be Haitia bermudezi (Low-dome Physa). That species has the apex of the shell very short, only slightly raised above the body whorl. The size of a mature individual is small to medium, 8 to 12 mm in length. According to the online manual, "The sculpture consists of axial striations only. Physid species have similar and superficially featureless, variable shells, and the shell is imprecise for identifying most genera and many species. Definitive identifications may require anatomical dissections and reference to other literature."

Physa freshwater snails eat algae, diatoms, and detritus.

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Unknown Species

Terrestrial Slug

On November 17, 2015, this 1.5 mm slug was captured in a pitfall trap placed under a Quercus laurifolia (Laurel Oak) just north of Smith Preserve Way. The slug's dorsal surface is shown in the first image; its ventral side is shown in the second image. The slug is in its contracted form which resulted from its being immersed in alcohol.

Slugs are snails without visible shells. Some species do have internal shells, but because all slugs lack external shells, they need to conserve moisture. To help with this problem, most are nocturnal and live in sheltered environments.

Slugs produce a slimy substance (mucus) that permits them to adhere to substrate and provides protection against abrasion. The pitfall sample, collected on November 17, 2015, contained many sand grains that were stuck together by mucus. Some species produce mucus that has chemical properties that help the slug defend itself against predators. It is unknown whether this individual produced that type of mucus.

Most slugs are hermaphroditic (ie. they have both male and female sex organs.) As a result, they can mate with other individuals or with themselves.

Slug development from the egg stage varies in time with weather conditions and species. But in general, several months or more are usually required for a slug to reach maturity. Slugs can live for a year or more and continue to grow larger throughout their life.

Most slugs are omnivores, feeding on fungi, decomposing vegetation, soil, and living plant tissue. A slug's mouth has a radula, a rasping structure with tooth-like features.

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© Photographs and text by Susan Leach Snyder (Conservancy of Southwest Florida Volunteer), unless otherwise credited above.

 

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