Ophiophragmus filograneus is an amphiurid estuarine brittlestar.
The arm color is mostly dark with occasional light bands, and the disk
color is usually gray or brown. There are two podial scales per podial
pore set at right angles and separated from one another by a distinct gap.
The aboral arm plates are not split in half. The disk scales are often
darker than the base color of the disk, typically with lighter borders, and
the disk margin has 20 or more fence papillae between the arms. The arm
spines nearest the disk are significantly longer than those at the ends of
the arms. (Pomory 2007, SMS undated).
Potentially Misidentified Species
Although echinoderm taxonomy is a highly specialized science, the general
appearance (see above), along with collection information (e.g., location
and habitat) should allow unambiguous identification of Ophiophragmus
filograneus. The congeneric species Ophiophragmus wurdemani
occurs in Florida waters, but is restricted to unvegetated benthic habitats
in more saline waters and does not penetrate deeply into Florida's brackish
estuaries (Turner and Meyer 1980).
HABITAT AND DISTRIBUTION
Ophiophragmus filograneus has been reported only from brackish
waters of Florida. (Talbot and Lawrence 2002, Pomory 2007).
Ophiophragmus filograneus is common throughout the IRL in
association with Halodule wrightii seagrass beds (Thompson 1978).
The Mosquito Lagoon portion of the IRL system is reported as the northern
distributional limit for the species (Turner and Meyer 1980).
LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan
The central disc of Ophiophragmus filograneus typically grows to as
much as 9-10 mm in diameter, and the long arms attain a length of up to 150
mm (Hendler et al. 1995, Talbot and Lawrence 2002).
Clements et al. (1994) sampled natural and planted Tampa Bay Halodule
beaudettei beds on a quarterly basis to determine Ophiophragmus
filograneus population densities. Mean quarterly densities averaged
10.6 individuals per square meter in natural grass beds (ranging from 0-32
individuals per square meter) and 33.8 individuals per square meter in
planted beds (ranging from 0-48.6 individuals per square meter).
Grizzle (1984) lists O. filograneus as among the most common
macrobenthic species at two IRL sites, one of which the authors considered
to be more environmentally degraded than the other. Brittlestar abundance
was approximately 4 times higher at the undegraded site, and the author
considers O. filograneus to be an equilibrium species rather than an
Several authors (e.g., Stancyk 1974, Turner 1974, Turner and Meyer 1980)
indicate that Ophiophragmus filograneus forms dense reproductive
populations in the Florida Halodule beds in which it occurs beds.
Stancyk (1973) hypothesized that Ophiophragmus filograneus exhibits
direct development (no planktonic phase), base on egg type. The author
suggests direct development as an adaptation for life in a harsh
environment, as has been suggested for other direct-developing echinoderms
Turner (1974) examined the post-metamorphic arm growth of Tampa Bay O.
filograneus and revealed the typical pattern to involve a faster rate
of growth in two non-adjacent arms and a concurrent slower growth in the
remaining arms. The author suggests this pattern may be an adaptation
allowing earlier descent of the disc within the substratum and away from
predation and salinity and temperature fluctuations, with the two arms
displaying concentrated growth remaining long enough to reach up to the
sediment surface. Arm lengths are gradually equalized as individuals grow.
Restricted to Florida, this is an exclusively subtropical species.
Individuals appear to actively burrow deeper within the soft sediment in
response to adverse surface conditions, including cold temperature (Stancyk
Although echinoderms are often cited as the only strictly marine major
animal phylum, a number of representatives may be encountered at salinities
less than full-strength seawater (Stickle and Diehl 1987). Of the
approximately 40 echinoderm species reported from brackish waters,
Ophiophragmus filograneus is the species with the greatest tolerance
for hyposaline conditions, occurring in estuaries but not in the open sea
(Turner and Meyer 1980, Talbot and Lawrence 2002). This species appears to
be the only echinoderm restricted to estuarine habitats.
Talbot and Lawrence (2002) questioned whether exclusion of O.
filograneus from higher open ocean salinities was due to physiological
adaptation for reduced salinities or to some other factor. Laboratory
experiments revealed that O. filograneus collected from Tampa Bay at
22 ppt was more physiologically stressed (based on measurements of
respiration, metabolism, and limb regeneration rate) at 16 ppt than at
either 22 ppt or 30 ppt. The findings suggest exclusion from the open
ocean may be due to factors other than salinity tolerance, such as dietary
resource availability, sediment type, or exclusion due to competition or
Ophiophragmus filograneus typically buries its disc in muddy sand
and extends one or more of its arms up to the sediment to feed (Stancyk
1974). As with a number of infaunal brittlestars,O. filograneus is
capable of functioning as both a suspension-feeder and as a deposit-feeder
likely to routinely ingest significant quantities of detrital material
(Clements et al 1994).
As with some other brittlestars, O. filograneus also appears capable
of resorbing portions of its own biomass if environment conditions (e.g.,
starvation) force individuals to catabolize tissue for maintenance (Dobson
et al., 1991). Turner and Murdoch (1976) describe a pattern of
preferential tissue resorption in which tissues from the disc, oral frame,
and arm tips are catabolized before other body tissues, leaving the
majority of arm tissue intact to take advantage of favorable feeding
conditions should they occur.
The exclusively estuarine distribution of this species likely minimizes competitive interactions with other brittlestar species.
Ophiophragmus filograneus is an important component in the diet of a
number of benthic-feeding animals, most notably stingrays of genus
Dasyatis and the cownose ray Rhinoptera bonasus (Turner at
The need for individuals to keep portions of their arms exposed at the
sediment surface for feeding purposes also exposes brittlestars species to
a high degree of sublethal partial predation, and animals often lose
portions of their exposed arms to shrimps, crabs, flatfish and other
epibenthic predators (Duineveld and Van Noort 1986, O'Connor et al. 1986).
Based on a Tampa Bay study, however Clements et al. (1994) indicated that
partial predation on seagrass-associated O. filograneus appears low
compared to rates reported for other infaunal brittlestars, particularly
those from unvegetated habitats.
Ophiophragmus filograneus is a common inhabitant of estuarine
Florida subtidal unconsolidated substratum environments and seagrass
meadows, particularly Halodule wrightii beds (Clements et al.
1994, Rose 1997, Pomory 2007).
O. filograneus is capable of regenerating lost arms from autotomized
discs.. The high incidence of O. filograneus regenerating arms in
the field suggests a high degree of sub-lethal predation in habitats
occupied by this species (Stancyk 1974, Lawrence 1990, Rose 1997).
Clements et al. (1994) estimate that 52-94% of brittlestars collected from
natural and planted Tampa Bay H. beaudettei beds showed evidence of
arm regeneration. Brown (1982) also reported a degree of gut replacement
in O. filograneus during regeneration of portions of autotomized
Neanthes succinea is an active forager primarily at night, spending most of the day in a mucous-lined tube (Craig et al. 2003).
No information is available at this time
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