Voucher Specimen: American Museum of Natural History # 583
C. seurati is an encrusting bryozoan that forms small whitish colonies on seagrasses
and other substrata. Zooids
are oval in shape and measure
approximately 0.55 X 0.33 mm. Each has a single pair of long, distal spines.
Lateral spines, if present, are highly variable in number.
The lophophore measures approximately 0.621 mm in diameter and bears an average
of 15 tentacles. The proximal
budding pattern of this species, which shows a distal-proximal pattern, sets it apart from most other members of its
genus. In C. seurati, the
ancestrula (the original settled larva) buds proximally. This proximal zooid then gives rise to 1 distal,
and 2 distolateral zooids. The distolateral zooids then bud proximally,
distally and laterally until a circle is formed around the ancestrula.
Potentially Misidentified Species
could be mistaken for C. tenuissimum. 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.
HABITAT AND DISTRIBUTION
C. seurati typically
occurs in Northern Europe and the Mediterranean. Prior to Winston's 1982 study,
this species had not been reported in the western hemisphere. Its range now
includes estuarine habitats on Florida's east coast.
C. seurati is likely to be widespread in the
IRL, but it has been primarily collected from Link Port (Winston 1982).
LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan
Individual zooids measure an average of 0.55 X 0.33
mm in size. Lophophore diameter measures 0.621 on average.
C. seurati is
among the most abundant bryozoan species in the IRL. It is most common from
December through May (Winston 1982). In the IRL, it is considered a fouling
organism (Winston 1995).
No ovicells are present in this species and eggs
are not brooded. Reproduction is accomplished by releasing eggs into the water
column for fertilization. Peak reproductive season occurs from late winter to
C. seurati and C. tenuissimum 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, settlement rates between both
species tend to equalize, and by May, only C. seurati is still settling.
After fertilization, embryos develop into
C. seurati is considered a winter species in the IRL, being most common from December through May (Winston 1982, 1995).
C. seurati is
one of 3 truly estuarine bryozoan species in the Indian River Lagoon. It was not
collected from coastal stations, but was routinely collected in the IRL in
waters where salinity ranged between 18 - 40 ‰ (Winston 1982, 1995). In
Europe, it has been collected in estuaries where salinity is less than 1 ‰
C. seurati, like all bryozoans, is a suspension feeder. Each individual zooid in a colony
has an average of 15 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 C. tenuissimum.
Typical habitat for ectoprocts in the Indian River
Lagoon include seagrasses, drift algae, oyster reef, dock, pilings, breakwaters,
and man-made debris (Winston 1995).
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,
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.
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.