Upload
donhan
View
224
Download
1
Embed Size (px)
Citation preview
Gastropods
Beautiful Mollusks
www.imms.org
The Institute for Marine Mammal Studies
(IMMS) is a non-profit organization established
in 1984 for the purpose of public education,
conservation, and research of marine mam-
mals and sea turtles in the wild and under hu-
man care. Located in Gulfport, MS, IMMS has
been an active participant in the National
Stranding Network since its inception. IMMS is
the premiere organization in the Mississippi-
Louisiana-Alabama sub-region of the Gulf
Coast with the capability and experience to
care for sick and injured marine mammals and
sea turtles. Additionally, IMMS promotes public
awareness of marine conservation issues
through its involvement in the community.
Institute for Marine Mammal Studies P.O. Box 207, Gulfport, MS 39502
Phone 228-896-9182 Fax: 228-896-9183 Email: [email protected]
Website: www.imms.org
Quick Facts Gastropods are mollusks and are related to squid,
octopus, and cuttlefish.
There are over 62,000 species of gastropods.
The Queen Conch can live as long as 40 years.
The study of mollusk shells is called conchology.
Cowrie shells were once used as currency in many Polynesian cultures.
The venom from the “sting” of some cone snails can be fatal to humans.
REMEMBER
Prepared by Chris Breazeale, 2012
References: World Register of Marine Species
University of California Museum of Paleontology
www.mesa.edu.au
www.paleo.cortland.edu
Gastropod reproduction varies greatly among spe-
cies. Hermaphroditism is common in all but the
marine species, with individuals serving as either
male or female during mating. The shape of the
shell can often determine the manner in which the
gastropod mates. Snails with tall shells use a
mounting technique while snails with flat shells
often mate in a face-to-face fashion. All gastro-
pods, however, reproduce through internal fertili-
zation. In some instances, sperm can be stored
for months or years before being used to fertilize
eggs. Mates are located through touch and the
use of pheromones, or by sensing cues in the mu-
cus trail left by terrestrial slugs. Most gastropods
are oviparous (egg laying). Land snails deposit
eggs in nests dug in
moist soil. Many
aquatic gastropods
deposit their eggs in
a gelatinous mass
containing as many
as 40,000 individu-
als. During spawn-
ing season, some
gastropods can lay
eggs in intervals of
one or two days.
Others, however, lay
much smaller clutch-
es (groups of eggs)
two or three times
each season. More
common are the
“mermaid’s necklac-
es” laid by the
whelks. These long
chains of egg cases
can be found on
beaches throughout
the world. Juvenile
gastropods are often
called protoconchs
and are shaped like
the adults.
Gastropods are categorized into groups called
clades. Clades are groups of organisms that have
descended from a common ancestor. There is
much discussion in the scientific community re-
garding the biological grouping of some species.
The clades listed below are generally recognized
by researchers.
Neritopsina contains fresh-
water, saltwater, and terrestri-
al species. They can be
found in all shapes and sizes
from limpet-like, to coiled
shells, to slugs.
Vetigastropoda includes
keyhole and slip-limpets,
top shells, abalone, and
several other families.
Caenogastropoda is a large
group that includes many
marine species often coveted
by shell collectors. Conchs,
whelks, moon snails, murids,
cowries, and many others
belong to this group.
Heterobranchia includes
opisthobranchs (sea hares,
sea slugs, and bubble shells)
and pulmonates (consist of
more than 20,000 species).
Patellogastropoda are true
limpets, historically called
Docoglossa. This a major
group of marine gastropods.
Cocculinidae are white lim-
pets that attach to organic
matter in the deep ocean.
This brochure is funded with qualified outer continental shelf oil
and gas revenues by the Coastal Impact Assistance Program,
United States Fish and Wildlife Service, U.S. Department of the
Interior through a grant award to the Mississippi Department of
Marine Resources.
Class: Gastropoda
Reproduction
Juvenile Whelks mitchellspublications.com
Whelk
Egg C
ase
mit
chell
spub
lica
tio
ns.
com
Red Helmet Shell (Cypraecassis rufa ) http://www.flickriver.com
Janolu
s barb
are
nsi
s
blo
g.u
sa.g
ov
Lightening Whelks Busycon contrarium nativeguidesfishing.com
Phylogeny
Hel
icin
a p
laty
chil
a
fr.w
ikip
edia
.org
P
ha
sia
no
tro
chu
s ex
imiu
s p
ort
ph
illi
pm
ari
nel
ife.
net
.au
Cypraea aurantium animals.nationalgeographic.com
Pa
tell
a r
ust
ica
en
.wik
iped
ia.o
rg
Cocc
uli
na s
ubco
mp
ress
a
concho
logy.b
e
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Scientific Classification
The Basics Gastropods represent a group of animals often
called snails or slugs. Meaning “stomach foot,”
the word gastropod describes the muscular “foot”
that runs along the underside of the snail. This
foot is used primarily for locomotion. Many gas-
tropods have a shell but some do not. The shelled
gastropods are often called univalves because
they only have one shell, as opposed to bivalves
which have two shells. Some of these animals are
terrestrial, living their entire lives on land. Like
all other mollusks, other gastropods live in marine
or freshwater habitats. There are approximately
62,000 described species and 13,000 genera of
gastropods found throughout the world, from the
neighborhood garden to deep-water hydrothermal
vent colonies. Current estimates place the num-
ber as high as 150,000 species. They comprise
80% of living mollusk species. Gastropods are
extremely diverse in morphology (shape), feeding
behavior, reproductive strategies, habitat range,
and size. They have the widest range of ecologi-
cal niches of all mollusks. Gastropods are among
the oldest known fossils, with their shells being
found in rocks dating 540 million years ago.
Many species today have remained unchanged for
over 350 million years.
Many gastropods have a shell that protects the soft body of the animal. The coiled shell opens on the right-hand side in most species and many species possess an operculum (gill cover) that further helps to protect the animal. Gastropods exhibit anatomi-cal torsion. This means the visceral (muscle) mass
rotates 180⁰ to one side during development, plac-ing the anus above the head. Gastropods typically have a well-defined head and two to four sensory tentacles with eyes located near the base of the ten-tacles or on separate eye stalks. The eyes of uni-valves are extremely diverse, with some possessing simple ocelli (simple eyes) which cannot process images, to eyes containing lenses for nocturnal species. The feeding habits of gastro-pods are varied, though most species utilize a radula (tongue-like structure). Rad-ulae are chitinous ribbons designed to scrape or cut food before it enters the esophagus. Both herbivo-rous (plant eating) and carnivorous (animal eating) snails use a radula for feeding. Some species even use their radula as a “drill” to bore into the shells of other mollusks before consuming their prey. Other univalves may be detritus (decaying organic matter) feeders, scavengers, or ciliary (tiny hairs) feeders. The primary organs for excretion are the nephridia. These organs produce ammonia or uric acid as a waste product. Most marine gastropods breathe using a gill but some freshwater species and most terrestrial species have a pallial lung (lung sac). Nudibranchs often have feathery gill plumes located on their backs.
Anatomy Gastropod shells
are essentially
exoskeletons.
The primary
functions of a
shell are to pro-
tect the animal
from predators and pro-
vide a place for muscle attachment. The shell is
also useful in the prevention of mechanical dam-
age. Terrestrial snails use the shell for protec-
tion against the sun and to prevent desiccation or
drying of the bodily fluids. Secreted by the man-
tle, the shell is composed mainly of calcium car-
bonate precipitated into an organic matrix
known as conchiolin. Due to the asymmetrical
nature of coiled shells, gastropods possess a
quality known as chirality or “handedness.”
Over 90% of gastropods have a dextral or “right-
hand” shell. Left-hand coiled shells are referred
to as sinistral. If the opening (aperture) of a
shell is on the right side when the shell is held
with spire pointing upwards, the shell is said to
be dextral. Occasionally, dextral species will
produce sinistral shells, and vice-versa. These
oddities are highly sought after by shell collec-
tors. There are a few species of arboreal (tree-
dwelling) land snails that show normally mixed
coiling, with individuals being either sinistral or
dextral. Not all shelled gastropods exhibit coil-
ing. Limpets, especially, are known to have
simple cone-shaped shells as adults.
Many gastropods are
used as food items
throughout the world.
Conchs in particular
are highly sought after
due to their mild fla-
vor, especially in the
Caribbean and the
Florida Keys.
Escargot, abalone, and
periwinkle snails are also
popular food items.
Throughout history,
seashells have been
used as ornamenta-
tion, scrapers, cooking
utensils, oil lamps,
boat bailers, musical
instruments, and even
currency. The world-
wide seashell trade has devastated populations
of gastropods, leading some countries to ban
the import and export of some shells. The
more endangered species have been fully pro-
tected in some areas, making it illegal to collect
or harvest these animals. In parts of the Carib-
bean, countries are now “farming” gastropods
like the queen conch to try to satisfy public
demand for meat and shells. The collection of
seashells is considered by some to be harmless.
Many beaches around the world are comprised
of shell material and animals such as the hermit
crab, rely solely on the discarded shells of gas-
tropods for survival. Although empirical data
from the trade of seashells are
hard to find, it is estimated
that billions of dollars each
year are made collecting and
selling shells around the
world.
Various Gastropod Shells ucmp.berkeley.edu
Pink Queen Conch Lobatus gigas naplesseashellcompany.com
Live Conch out of Shell members.virtualtourist.com
Co
nch F
ritt
ers
u
rbansp
oo
n.c
om
Cayenne Keyhole Limpet Diodora cayenensis
Green abalone Haliotis fulgens shells-of-aquarius.com
Hermit Crab in Shell hermitcrabpetcare.com http://njscuba.net
The freshwater Sinistral Pond Snail (Physella sp.) scrapes algae from the
glass with its radula ucmp.berkeley.edu
Shells Human Impacts