Species Description:
H. verrilli
colonies are calcified and encrusting. Individual zooids are regular in shape,
and generally quadrangular. Zooids measure an average of 0.40 X 0.29 mm, but
older colonies grow as large as 0.47 X 0.39 mm. A slightly raised rim separates
zooids from each other. Ten to twenty regularly-spaced pores perforate the
frontal surface of individual zooids. The orifice is rounded distally, with a
slightly curved proximal portion. There is often an umbo just inferior to the
orifice. The lophophore measures approximately 0.428 mm in diameter and bears 12
tentacles. avicularia are highly variable, or absent in some colonies. If they
are present, they may occur on either side, or on both sides of the orifice.
Avicularia may be narrow; ovoid, or have round bases with triangular mandibles.
The narrow type is generally directed proximolaterally; the other types can have
a variety of orientations. Living specimens from the IRL area are ivory or beige
in color. However, specimens from other areas vary from shades of yellow to red.
Other Taxonomic Groupings:
Suborder: Ascophora
II. HABITAT AND
DISTRIBUTION
Regional Occurrence:
H. verrilli is
widely distributed in warm temperate to tropical waters, and is especially
common in brackish water areas. In the western Atlantic, it is found from Cape
Cod south to Brazil. In the Pacific, it is found from the Gulf of California to
the Galapagos Islands, Ecuador.
IRL Distribution:
H. verrilli is
a highly abundant and well known fouling organism within the Indian River
Lagoon.
III. LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan:
Zooids measure an average of 0.40 X 0.29 mm, but
older colonies grow as large as 0.47 X 0.39 mm. The frontal surface of
individual zooids is perforated by 10 - 20 regularly spaced pores. The
lophophore measures approximately 0.428 mm in diameter and bears 12 tentacles.
Abundance:
H. verrilli is
one of the most abundant bryozoan species in the Indian River Lagoon. It occurs
most commonly from October through June, with greatest abundance in the Fall.
Locomotion:
Sessile
Reproduction:
The heaviest period of larval settlement in this
species is in Fall, from October through January, though new colonies continue
to settle through June.
Embryology:
Globular ovicells are present. These are
hyperstomial and have rough calcification around the outside, with a smoother,
porous central area. The central area may become secondarily calcified. Embryos
are a red-orange color.
IV. PHYSICAL TOLERANCES
Temperature:
H. verrilli is
eurythermal,
with its period of heaviest reproduction occurring in cooler months.
Salinity:
H. verrilli is
commonly collected in areas where salinity falls below 30‰.
V. COMMUNITY ECOLOGY
Trophic Mode:
H. verrilli,
like all bryozoans, is a suspension feeder. Each individual zooid in a colony
has 12 ciliated tentacles which 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.
Habitats:
Typical habitat for ectoprocts in the Indian River
Lagoon include seagrasses, drift algae, oyster reef, dock, pilings, breakwaters,
and man-made debris (Winston 1995). H. verrilli was typically found
encrusting wood, shell and other hard substrata.
Associated Species:
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.
VI. SPECIAL STATUS
Special Status:
None.
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.
Economic Importance:
None
Report by: K. Hill,
Smithsonian Marine Station
Submit additional information, photos or comments to:
irl_webmaster@si.edu
Page last updated: July 25, 2001
|
