Potentially Misidentified Species: Although echinoderm taxonomy is a highly specialized science, the general appearance, 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).
Regional Occurrence: Ophiophragmus filograneus has been reported only from brackish waters of Florida. (Talbot and Lawrence 2002, Pomory 2007).
IRL Distribution: 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).
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).
Abundance: 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 opportunistic species.
Reproduction: 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.
Embryology: 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.
Temperature: 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 1970).
Salinity: 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 predation.
Trophic Mode: 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.
Competitors: The exclusively estuarine distribution of this species likely minimizes competitive interactions with other brittlestar species.
Predators: 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 al. 1982).
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.
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 discs.
Activity Time: Neanthes succinea is an active forager primarily at night, spending most of the day in a mucous-lined tube (Craig et al. 2003).
Brown BK. 1982. Gut replacement during disc regeneration of the autotomized disc of Ophiophrugmus filograneus (Echinodermata: Ophiuroidea). Unpublished master's thesis, Florida Institute of Technology, Melbourne. 90 p.
Clements LAJ, Bell SS, and JR Kurdziel. 1994. Abundance and arm loss of the infaunal brittlestar Ophiophragmus filograneus (Echinodermata: Ophiuroidea), with an experimental determination of regeneration rates in natural and planted seagrass beds. Marine Biology 121:97-104.
Dobson WE, Stancyk SE, Clements LA, and RM Showman. 1991. Nutrient translocation during early disc regeneration in the brittlestar Microphiopholis gracillima (Stimpson) (Echinodermata: Ophiuroidea). Biological Bulletin 180:167-184.
Duinevetd GCA, and GJ Van Noort. 1986. Observations on the population dynamics of Amphiura filiformis (Ophiuroidea: Echinodermata) in the southern North Sea and its exploitation by the dab Limanda. Netherlands Journal of Sea Research 20:85-94.
Grizzle RE. 1984. Pollution indicator species of macrobenthos in a coastal lagoon. Marine Ecology Progress Series 18: 191-200.
Hendler GJ, Miller E, Pawson DL, and PM Kier. 1995. Sea stars, sea urchins, and allies. Echinoderms of Florida and the Caribbean. Washington, D.C.: Smithsonian Institution Press.
Lawrence JM. 1990. The effect of stress and disturbance on echinoderms. Zoological Science 7:17-28.
O'Connor B, Bowmer T, McGrath D, and R Paine. 1986 Energy flow through an Amphiura filiformis (Ophiuroidea: Echinodermata) pepulation in Galway Bay, west coast of Ireland: Preliminary investigation. Ophelia 26:351-357.
Pomory CM. 2007. Key to the common shallow-water brittle stars (Echinodermata: Ophiuroidea) of the Gulf of Mexico and Caribbean Sea, Caribbean Journal of Science Special Publication No. 10. University of Puerto Rico, Mayaguez. 42 p.
Rose CS. 1997. Distribution, body size, and regeneration of the amphiurid, Ophiophragmus filograneus in the Tampa Bay area, with special reference to the presence of the seagrass, Halodule wrightii. MS thesis. University of South Florida, Tampa.
Stancyk SE. 1970. Studies on the biology and ecology of ophiuroids at Cedar Key, Florida. M.Sc. Thesis. University of Florida. 92 p.
Stancyk SE. 1973. Development of Ophiolepis elegans (Echinodermata: Ophiuroidea) and its implications in the estuarine environment. Marine Biology 21:7-12.
Stancyk SE. 1974. Life history patterns of three estuarine brittlestars (Ophiuroidea) at Cedar Key, Florida. PhD dissertation. University of Florida, Gainesville.
Stickle WB, and WJ Diehl. 1987. Effects of salinity on echinoderms. Echinoderm Studies 2:235-285.
Talbot TD and JM Lawrence. 2002. The effect of salinity on respiration, excretion, regeneration and production in Ophiophragmus filograneus (Echinodermata: Ophiuroidea). Journal of Experimental Marine Biology and Ecology 275:1-14.
Thomas LP. 1961. Distribution and salinity tolerance in the amphiurid brittlestar Ophiophragmus filograneus (Lyman, 1875). Bulletin of Marine Science of the Gulf Caribbean 11:158-160.
Turner RL. 1974. Post-metamorphic growth of the arms in Ophiophragmus filograneus (Echinodermata: Ophiuroidea) from Tampa Bay, Florida (USA). Marine Biology 24:273--277.
Turner RL and CE Meyer. 1980. Salinity tolerance of the brackish-water echinoderm Ophiophragmus filograneus (Ophiuroidea). Marine Ecology Progress Series 2:249-256.
Turner RL, Heatwole DW, and SE Stancyk. 1982. Ophiuroid discs in stingray stomachs: evasive autotomy or partial consumption of prey? p. 331-335 In: Lawrence, J. M. (ed.) Echinoderms. Proceedings of the International Conference, Tampa Bay. A. A. Balkema, Rotterdam.
Aboral: In a direction away from the mouth; the part of the body opposite the mouth.
Anal Cone: In crinoids and echinoids, a fleshy projection bearing the anus at its apex; also known as an anal tube.
Apical System: In echinoids, a ring of specialized skeletal plates, including the genital plates and ocular plates; usually located on the highest point of the test.
Arm: In asteroids, crinoids, and ophiuroids, a movable, jointed ambulacral projection, distal to the disk or calyx that carries a radial branch of the water vascular system and the nervous system; sometimes called a ray.
Basket: One of several types of microscopic skeletal ossicles in holothuroids; minute cup-shaped ossicle, usually with four projections.
Button: One of several types of microscopic skeletal ossicles in holothuroids; minute ossicle with four perforations; may be smooth or knobbed.
Disk: The round or pentagonal central body region of ophiuroids and asteroids; see also Terminal Disk.
Distal: In a direction away from the center of the body; for example, toward the tip of the arm in asteroids or the tip of a spine in echinoids.
Dorsal: In echinoderms, this term is variously applied; in asteroids, ophiuroids and echinoids it usually refers to the surface of the body that is opposite the mouth, the surface that is uppermost; in holothuroids, with mouth and anus opposite ends of the cylindrical body, the uppermost surface is considered dorsal; in crinoids, the surface opposite the mouth in considered dorsal by convention, even though it is functionally the ventral (lower) side.
Echinulate: Something spiny or prickly, usually referring to the microscopic texture of a skeletal element such as a spine.
Hermaphrodism: A condition in organisms whereby one individual possesses both functional male and female reproductive structures; hermaphroditic individuals may express both sexes simultaneously, alternately, or sequentially.
Interambulacral Area: An oral or aboral section of the body lying between two ambulacra; in interradius; also known as an interambulacrum.
Interradial: Referring to interambulacral areas of the body; interradius and interradii also commonly used.
Oral: In a direction toward the mouth; a part of the body on the same surface as the mouth.
Oral Papillae: In ophiuroids, small plates at the edge of the mouth, attached to the edges of the jaw plate and/or to the aboral shield; may be variously shaped, from spine-like to scale-like.
Papillae: In holothuroids, specialized dorsal tube feet that lack a suckered tip; in ophiuroids, certain skeletal elements of the jaws or disk.
Papillate: Covered with papillae.
Papillose: Covered with papillae.
Pedicellariae: Small stalked or unstalked pincer-like organs on the body of asteroids and echinoids, used for defense and grooming.
Peltate: Shield-shaped; used to describe the tentacles of some holothuroids.
Perforated Plate: One of several types of microscopic skeletal ossicles in holothuroids; sieve-like and widespread; may also be found in other echinoderm classes, especially in juvenile individuals.
Periproct: In echinoids, a flexible region surrounding the anus, which consists of a membrane containing embedded plates and often bearing spines and pedicellariae.
Plates: One of several types of skeletal elements in echinoderms; tabular structures with a characteristic shape and a fixed position.
Primary Plates: The first-formed plates on the dorsal side of the disk; in ophiuroids, these are the central and five radial plates; in adults, they may form a rosette of scales near the center of the disk, or they may be separated by numerous secondarily developed scales.
Radial: In a direction toward the central axis of an arm or ambulacrum; a part of the body near an arm or ambulacrum.
Radial Shields: Pairs of plates on the dorsal surface of the ophiuroid disk, which lie near the base of each arm; usually relatively large and conspicuous, but may be hidden by granules or superficial scales.
Rods: One of several types of microscopic skeletal ossicles in holothuroids; commonly found as supporting structures in tentacles or tube feet.
Scales: One of several types of skeletal elements in echinoderms; flat, thin structures that are overlapping, tessellate, or haphazardly arrayed.
Sole: In some holothuroids, the flattened ventral part of the body, either covered with or surrounded by tube feet.
Spines: One of several skeletal elements in echinoderms; movable, articulating structures that are long, slender and attenuated.
Teeth: In ophiuroids, small plates or spines attached to the dental plate on the inner edge of the jaw, a series of them extending into the mouth; in echinoids, the five hard, sharp, and movable ossicles incorporated in Aristotle’s lantern; the term also refers to five movable ossicles that surround the anus of some holothuroids.
Tentacle Scales: Small, movable spines or scales, associated with ophiuroid tube feet, which are attached to the ventral arm plate and/or lateral arm plate; may cover the tentacle pores and protect the retracted tube feet.
Tentacles: In holothuroids, feeding structures in the form of highly modified tube feet arranged in a ring around the mouth.
Terminal Disk: Round portion on the end of the tube foot in many echinoderms; usually employed for attachment to substrates.
Tube Feet: Fluid-filled, fingerlike extensions of the water vascular system that protrude through the openings in the skeleton or between skeletal elements; muscles and nerves in the shaft of the tube feet control their movements; glands, and sometimes a muscular sucker, at the tip function in adhesion; specialized tube feet are used for locomotion, feeding, burrowing, respiration, and a combination of functions.
Ventral: In echinoderms, this term is variously applied; in asteroids, echinoids and ophiuroids, it is the surface of the body that carries the mouth; this surface is in contact with the substrate; in holothuroids, with mouth and anus at opposite ends of a cylindrical body, the ventral surface is lowermost, in contact with the substrate; in crinoids, the ventral surface carries the mouth and is functionally the uppermost surface.