Predatory Snails, and Prey, of Bay Mouth Bar

Bay Mouth Bar is a series of sand bars and seagrass beds at the mouth of Alligator Harbor.  For just a few days a month, the tide is low enough for it to be exposed for a couple of hours.  When that happens, you can see an incredible diversity of life, including more predatory snails than anywhere else in the world.  That’s what attracted Dr. Robert Paine to the area in the late 1950′s, as he was forming his ideas about keystone species and food webs.  In recent years, Dr. David Kimbro and his lab have repeated surveys and found that there have been a few changes in the last fifty years.  His doctoral student, Tanya Rogers, is conducting further research into whether the removal of one of Bay Mouth Bar’s top predators played a role in these changes.

Foundation Species

Turtle Grass (Thalassia testudinum)
Turtle grass is Florida’s most important seagrass species for habitat formation. Click to expand

Shoal Grass (Halodule wrightii)
Shoal grass is another of the dominant seagrass species in Florida. Click to expand.

Shoal grass is one of the dominant seagrass species in Florida. It is usually found growing in shallow water and can tolerate prolonged periods of exposure during low tide.

Manatee Grass (Syringodium filiforme)
Manatee grass is commonly found in mixed seagrass beds. Click to expand.

Manatee grass is commonly found in mixed seagrass beds.

Top Predator

Horse Conch (Pleuroploca gigantea)
Not a true conch, this large snail is a predator in the lower intertidal and subtidal zones.  Click to expand

Tulip (Fasciolaria tulipa) also known as the True Tulip
Tulips were once a primary predator of the Bay Mouth Bar ecosystem, second only to the horse conch. Click to expand

A predatory snail found in mud/ sand flats and seagrass beds.  Tulips were once a primary predator of Bay Mouth Bar, but are no longer found in that community. As a top predator, these snails were second only to the horse conch, feeding on large other snails and bivalves.  The horse conch was its main predator on Bay Mouth Bar.

True Tulips are distinguished from Banded Tulips primarily by the lines on their shells. Adult Tulips have 25-38 interrupted lines along their shells, while Banded Tulips have 4-8 unbroken lines.
Read more about an experiment being conducted by Tanya Rogers on the loss of predatory diversity on Bay Mouth Bar here.

 Other Predators

Banded Tulip (Fasciolaria hunteria)
The Banded Tulip is a predator snail that feeds on a variety of prey.  Click to expand

The Banded Tulip is a predator snail that feeds on a variety of prey including small snails, bivalves, tube worms, and carrion. True Tulips are distinguished from Banded Tulips primarily by the lines on their shells. Adult Tulips have 25-38 interrupted lines along their shells, while Banded Tulips have 4-8 unbroken lines.

Lightning Whelk (Busycon contrarium)
Like the crown conch, the lightning whelk uses its proboscis to pry bivalves open and suck out the flesh.  Click to expand

Like the crown conch, the lightning whelk uses its proboscis to pry bivalves open and suck out the flesh.  Its proboscis is slender compared with that of a conch, and so it doesn’t have the force to pry open oyster shells, eating instead clams and mussels.  While they get fairly large compared to other predatory snails found in Florida waters, they do not consume other snails and are themselves consumed by tulip snails and horse conchs. These whelks can be easily confused for knobbed whelks, with which it shares many characteristics. The best way to visually differentiate the two is by identifying on which side it curves.   Lightning whelks curve on the left (sinistral) side, knobbed whelks on the right (dextral).  This elegant curve gave the whelks particular value to Florida’s native Apalachee people and their counterparts in other Mississippian cultures. You can read more about whelks and the Apalachee here.

Lace Murex (Murex florifer)
The Murex is one of the predatory snails that has disappeared from Bay Mouth Bar.  Click to expand.

The Murex is one of the predatory snails that has disappeared from Bay Mouth Bar. A drilling predator, the Murex is a specialist, feeding on bivalves, particularly cross-barred venus.

Read more about an experiment being conducted by Tanya Rogers on the loss of predatory diversity on Bay Mouth Bar here.

Moon Snail (Polinices dulpicatus)
Polinices burrows in the sand flats, looking for its prey.  Click to expand

Polinices burrows in the sand flats, looking for its prey. Once its meal is found, the moon snail envelops it, secreting acid until the prey is soft enough for the snail to pierce with its radula. These snails are drilling predators and feed primarily on bivalves. The body of a moon snail can extend outside of its shell and almost completely cover it, but can be retracted completely inside when disturbed.

Pear Whelk (Busycon spiratum)
Pear whelks feed on bivalves and small snails, such as moon snails and turban snails.  Click to expand

Pear whelks feed on bivalves and small snails, such as moon snails and turban snails.

White Baby Ear (Sinum perspectivum)
The White Baby Ear is a drilling predator that feeds on bivalves.  Click to expand

The White Baby Ear is a drilling predator that feeds on bivalves. Like the moon snail, the white baby ear burrows down into the sediment and can extend its body outside of its shell to nearly cover it. Unlike the moon snail though, it cannot completely retract its body inside its shell.

Other Gastropods (Snails)

Bruised Nassa (Nassarius vibex) also known as the Eastern Nassa
These scavengers are generally known as “mud snails”.  Click to expand

These scavengers are generally known as “mud snails”. They have a long siphon with which they can smell food from long distances away.

Chestnut Turban (Turbo cataneus)

Gulf Oyster Drill (Urosalpinx perrugata)
Urosalpinx are drilling predators, feeding on bivalves and barnacles.  Click to expand

Urosalpinx are drilling predators, feeding on bivalves and barnacles. These can often be found on the backs of horse conchs.

Common Atlantic Marginella (Prunum apicinum)

Bivalves

Ark Shell (Anadara sp.)

Bay Scallop (Aequipecten irradians)
In the summer months, scalloping is a common recreational activity along Florida’s Gulf coast. Click to expand

Open harvest season for bay scallops along Florida’s Gulf coast runs July 1-September 24.

Broad-Ribbed Cardita (Carditamera floridana)

Cross-Barred Venus (Chione cancellata)

Florida Prickly Cockle (Trachycardium egmontianum)

Pen Shell (Atrina sp.)
The largest clam on Bay Mouth Bar, it is the only bivalve consumed by horse conchs. Click to expand.

The largest clam on Bay Mouth Bar, it is the only bivalve consumed by horse conchs.

Southern Horse Mussel (Modiolus squamosus)

Southern Quahog (Mercenaria campechiensis)
The southern quahog is closely related to the northern quahog (Mercenaria mercenaria), which is also known as the hard clam.  Click to expand

The southern quahog is closely related to the northern quahog (Mercenaria mercenaria), which is also known as the hard clam and is frequently eaten by humans.

Tanya Rogers tested the survivorship and causes of death of clams on Bay mouth Bar by tethering baby quahog and sunray venus clams in various locations on the bar. Read more on Tanya’s experiment here.

Read about when WFSU-TV Producer Rob Diaz de Villegas tried his hand at quahogging and making New England Quahog Chowder here.

Sunray Venus (Macrocallista nimbosa)
Click to expand

Tanya Rogers tested the survivorship and causes of death of clams on Bay mouth Bar by tethering baby quahog and sunray venus clams in various locations on the bar. Read more on Tanya’s experiment here.

Yellow Egg Cockle (Laevicardium mortoni)

Other Invertebrates

Brachiopod (Glottidia pyramidata)

Sand Dollar (Mellita quinquiesperforata)

Sea Urchin

Spider Crab

Tunicates

Polychaete Tube Worms