CONTRIBUTIONS TO THE BIOLOGY OF MEOMA VENTRICOSA (ECHINOIDEA: SPATANGOIDA)1 RICHARD H. CHESHER2 Museum of Comparative Zoology, Harvard University ABSTRACT The biology of Meoma ventricosa (Echinoidea; Spatangoida) is de- scribed on the basis of a two-year study conducted in Florida, the Bahama Islands, Panama, and Colombia. The habitat, behavior, food and feeding, growth, reproduction, predators, parasites, commensals, abnormalities, internal anatomy, and relation to the substrate of this large, abundant echinoid are discussed. INTRODUCTION Meoma ventricosa was described by Lamarck in 1816 but until Kier & Grant (] 965) published data on its distribution and behavior, nothing was known about the ecology of this large and abundant animal. M. ventricosa is a member of the largest and most successful order of sea-urchins, the Spatangoida. Spatangoids live in the mud and sand bottoms of all oceans and range in depth from the intertidal zone to about 5000 meters. The literature and systematics of the group are in excellent order, having been summarized by Mortensen (1950, 1951). The fossil history of spatangoids is perhaps superior to that of any other echinoderm group. One of the few known examples of long-term, continuous evolution is that of a spat- angoid from the Chalk of England (Kermack, 1954; Nichols, 1959). In spite of such impressive attributes, very little is known about spatan- goid biology. What data is available shows this to be a rewarding area of study. Moore (1936), Nichols (1959, 1962), Buchanan (1966, 1967), Brattstrom (1946), and Vasseur & Carlsen (1949) have studied ecological aspects of European spatangoids, and Moore & Lopez (1966), Chesher ( 1963), and Kier & Grant (1965) have studied ecological aspects of some tropical spatangoids. One of the major difficulties in studying spatangoids has been their habit of burrowing, which makes them difficult to find and capture. This is particularly true in shallow water, where maneuvering is dangerous for ships with adequate dredging facilities. The development and popularization of free diving apparatus has opened the way for intensive ecological studies in these and other areas which are relatively inaccessible from the surface (Riedl, 1967). M. ventricosa (Fig. 2) is a burrowing sea-urchin common to the coral 1Contribution No. 986 from the Institute of Marine Sciences, University of Miami. " Present address: Department of Biology, College of Guam, Agana, Guam. 1969J Chesher: Biology of Meoma ventricosa 73 reef areas of the West Indies; it is one of the largest and most accessible of the sand-dwelling, tropical spatangoids. Large populations found in Florida, the Bahamas, and Panama provide an excellent opportunity to examine the urchins in their natural habitat. Using various diving tech- niques, which ranged from snorkeling to night diving with small submarines, populations of M. ventricosa were examined from Fort Lauderdale to Key West along the Florida coast, and in a variety of locations in the Bahama Islands, in Panama, and in eastern Colombia. Monthly observations and collections were made near Molasses and Alligator reefs in the Florida Keys. Distribution, behavior, reproduction, growth rates, and ecological parameters were examined in the field. Morphology, internal anatomy, and details of behavior were studied in the laboratories of the Institute of Marine Sciences, Miami, Florida. The study began in 1964 and continued through the summer of 1966. MATERIALS AND METHODS Populations of M. ventricosa were studied from Santa Marta, Colombia; Isla Grande, Panama; Key West, Alligator Reef, Molasses Reef, Ajax Reef, Triumph Reef, Fowey Rocks reef, and Fort Lauderdale along the Florida coast; and Bimini, Grand Bahama, Abaco, Andros, the Berry Is- lands, New Providence, and the Exuma Islands in the Bahama Islands. Preserved specimens were examined from Bermuda, the Gulf of Mexico, Puerto Rico, and other areas in the Caribbean. Skin-diving and scuba-diving techniques were used to examine the pop- ulations in situ. Diving operations were conducted both during the day and at night in depths from the intertidal zone to 60 meters. The distribution of the populations of M. ventricosa in Florida was observed in local areas at night from a towed submarine. Adult urchins were collected simply by picking them up by hand, but young urchins posed a problem, as they leave no trace on the surface of the sand and do not emerge from the sand at night as do the adults. Three methods proved successful for finding them. Many young specimens were found living under coral slabs behind the shallow reef areas. The coral slabs were overturned, and the sand washed away by "fanning" the area by hand or by flipper. Young specimens were excavated from the grass areas with a small air-lift dredge. For portability and convenience, an air- lift was designed to operate from a tank of compressed air. The unit (Fig. 1,A) was made from a 3-meter section of plastic tubing, 6.5 cm in diameter, of the type used in taking deep-sea cores. A fine-mesh net bag was clamped onto one end of the tube. Air was introduced to the other end of the tube via a high-pressure hose and valve assembly attached to a scuba tank. The valve controlled the flow of air and thus the amount of material lifted and the length of time the unit could be used. When in use, 74 Bulletin of Marine Science [19(1 ) A I FIGURE I.-A, portable air-lift dredge for capturing small specimens of burrow- ing animals. (n, net bag to retain specimens; h, clamp; p, plastic tube, 3 meters long, 6.5 cm diameter; i, intake end; c, collar to provide an even flow of air into the intake end of the dredge; v, valve controlling the air flow; t, high pres- sure rubber hose; y, yoke to fasten hose to scuba tank.)-B, measuring board for tagging urchins underwater. Construction is of %-inch clear Plexiglas. Ca, movable arm; I, pencil; 95, the tag number on the urchin and marked on the board; s, pencil sharpener.) 1969] Chesher: Biology of Meoma ventricosa 75 the end with the net was directly above the diver and the end which re- ceived the flow of air was held next to the sand. The dredge sucked up large amounts of sand and could operate continuously for about 15 to 20 minutes. The scuba tank was held on the diver's back with a double tank harness, which also held another tank for the diver's breathing air. The air-lift was quite useful for digging small specimens out of sand pockets and grassy areas where other methods of digging were difficult. Alan Emory, of the Institute of Marine Sciences, subsequently used the same apparatus to sample planktonic organisms from the small niches within the coral reef structure. Finding small urchins in the broad, open sand areas presented still an- other problem. The air-lift was too slow, and digging by hand was un- economical. Surface trawls did not cover enough distance along the bottom (they became clogged within a few meters). A portable 3.5-h.p. water pump was placed in an outboard motorboat, and a 60-meter length of fire- hose with a brass nozzle was used to direct a stream of water at the sand. The jet of water cleared away the sand rapidly, exposing the burrowing animals without harming them. The jet was directed in long, slow sweeps from side to side as the diver moved ahead. By working with the direction of the bottom currents in the area, the silt that was stirred up was carried away from the diver. Tagging, feeding, and behavior experiments were performed in situ, and the methods are described below in the sections on growth, feeding and behavior. Ciliary currents were discerned by using a dissecting microscope and biologically inert fluorescent particles (Tracer-Glow pigments available from Wildlife Supply Co., Saginaw, Michigan) and food-coloring dyes. Small dots of the food dye were placed on the test with a hypodermic syringe; the progress of the ciliary currents was easily traced by the move- ment of the dye. Movement of sand particles was determined by using black grains of sand. After the animal had begun to burrow into the zone containing the black grains, the burrow was opened up and the progress of these grains was then visible. Movement of particles and feeding methods were observed through a glass-bottomed aquarium. Analyses of the sediment were based on the techniques described by Krumbein & Pettijohn (1938). Core samples were taken by pushing a plastic core tube, 20 cm in length, into the substrate. Both ends of the core tube were then stoppered with rubber plugs. The cores were stored in an ice-cooler and frozen within two hours. H~S was measured with a kit produced by Hatch Chemical Co. Particle size was measured by wet screening through a nest of sieves with mesh sizes of 2.0, 1.0, 0.5, 0.25, 0.125, and 0.062 mm. Silt and clay fractions were separated via liquid suspension (Krumbein & Pettijohn, 1938). Porosity of the substrate was 76 Bulletin of Marine Science [19(1) FIGURE 2. Adult specimen of Meoma ventricosa (132 mm test length) photo- graphed alive: A, dorsal view; B, ventral view. determined by measuring the loss in weight of the sand upon drying. Per- meability was measured in a permeameter as described by Stearn (1927). Total organic carbon present was measured by ignition of a preweighed sample to 500°C, at which temperature the organic carbon is driven off as CO2. CaCOx does not burn until a much higher temperature is reached. Crucibles were pre-ignited to 1000°C, cooled in a desiccator, and weighed. Samples were cut from the central portion of a frozen core, using a sterile, stainless steel knife, and then were dried in a vacuum desiccator at 28 Ibsjin2 and 50°C before being weighed prior to ignition.