Other Taxonomic Groupings
Voucher Specimen: American Museum of Natural History # 584
Colonies of C. tenuissimum form
white crusts on seagrasses, shells, and other substrata. Primary buds
usually form distally from the ancestrula (the original settled larva), with
the next buds forming proximally. Growth proceeds in both directions, and
intermediate buds aid in forming a double fan shape that eventually becomes
rounded. Zooids are oval in shape and measure 0.53 X 0.25 mm. Each zooid has
a pair of short distal spines, and 5 - 7 pairs of lateral spines. The
operculum is chitinous. The lophophore averages 0.475 mm in diameter and
bears an average of 12 tentacles. Old colonies have areas where degenerate
zooids are partially closed or calcified, and filled with storage products,
while other areas within the colony have new or regenerating zooids with
Potentially Misidentified Species
C. tenuissimum could
be mistaken for C. seurati, since the 2 species occupy the same substrata
and are morphologically similar. However, the budding pattern in C.
tenuissimum is slightly more regular than in C. seurati due to C.
tenuissimum's somewhat larger zooid size and distal-proximal budding
pattern. Additionally, lateral walls in individual zooids are more calcified in C.
seurati, and its distal spines are longer and more pointed. C. seurati
has fewer lateral spines than C. tenuissimum in water of the same
salinity: 1 - 3 for C. seurati vs. 5 for C. tenuissimum.
Seasonally, C. seurati is most common in the winter months, while C.
tenuissimum is most common in spring and summer. In terms of salinity, C.
seurati is more common in waters with lower salinity than is C.
HABITAT AND DISTRIBUTION
is a common estuarine species along the east coast of the United States and the
Gulf of Mexico. It is also found in some locations along the Pacific coast, and
is believed to have been introduced, along with oysters, from the Gulf coast of
the U.S. (Lagaaij and Cook 1973; Winston 1982).
is one of the most abundant bryozoan species inhabiting the Indian River Lagoon
(Winston 1982, 1995).
LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan
Individual zooids of C. tenuissimum attain an average size of 0.53 X 0.25
mm. The lophophore has between 11 and 13 tentacles and measures approximately
0.475 mm in diameter.
C. tenuissimum is one of the most abundant bryozoans within the IRL and is considered a fouling
organism (Winston 1995). While it is abundant in the IRL, it is found in its
greatest numbers in the St. James River, near Jamestown, VA.
is able to grow to reproductive size in less than 1 month. No ovicells are
present. Reproduction occurs in both spring and fall, and is accomplished by
release of eggs into the water column via the intertentacular organs of
polypides. Peak reproduction occurs in late fall (Winston 1982).
C. tenuissimum and C.
seurati co-occur in estuarine habitats, but their reproductive seasons are
apparently offset. During December, when C. tenuissimum larvae are
settling in their greatest numbers, they can outnumber C. seurati by a
ratio of 99:1. However, throughout January, their settlement rates tend to
equalize and by May, only C. seurati is still settling.
Fertilized eggs released into the water column develop into planktonic larvae.
is collected year-round, and thus is able to withstand seasonal fluctuations in water
temperature. It is considered to be eurythermal.
is one of 3 species of truly estuarine bryozoans. It was not collected from
coastal stations surveyed by Winston (1982, 1995), but was routinely collected
from the IRL where salinity ranged from 18 - 40.
like all bryozoans, is a suspension feeder. Each individual zooid in a colony
has an average of 12 ciliated tentacles that are extended to filter
phytoplankton less than 0.045 mm in size (about 1/1800 of an inch) from the
water column. Bullivant ( 1967; 1968) showed that the average individual zooid
in a colony can clear 8.8 ml of water per day.
Winston (1982) reported that C. seurati may be a better space competitor
than C. tenuissimum, because its colonies were often observed to overgrow
Typical habitat for ectoprocts in the Indian River Lagoon include seagrasses,
drift algae, oyster reef, dock, pilings, breakwaters, and man-made debris
(Winston 1995). Because C. tenuissimum is a fast growing species and
attains reproductive size in under 1 month, it is able to live successfully on
small, unstable substrata. Even the seagrass Syringodium has been shown
to provide suitable habitat for reproductively successful colonies of C.
tenuissimum (Winston 1982).
Seagrasses as well as floating macroalgae, provide support for bryozoan
colonies. In turn, bryozoans provide habitat for many species of juvenile fishes
and their invertebrate prey such as polychaete worms, amphipods and copepods
(Winston 1995). Bryozoans are also found in association with other species that
act as support structures: mangrove roots, oyster beds, mussels, etc.
Benefit in IRL
Bryozoans are ecologically important in the Indian River Lagoon due to their
feeding method. As suspension feeders, they act as living filters in the marine
environment. For example, Winston (1995) reported that bryozoan colonies located
in 1 square meter of seagrass bed could potentially filter and recirculate an
average of 48,000 gallons of seawater per day.
Lagaaij R, Cook PL. 1973. Some Tertiary to Recent Bryozoa. In: Atlas of Palaeobiogeography, Hallam, A. Ed. 489-498. Amsterdam, NL: Elsevier.
Winston JE. 1982. Marine bryozoans (Ectoprocta) of the Indian River area (Florida). Bull Amer Mus
Nat Hist 173: 99-176.
Winston JE. 1995. Ectoproct diversity of the Indian River coastal lagoon. Bull Mar Sci 57: 84-93.