if there are three the right corner is spineless, and if there are two the right and left corners lack spines (fig. 47a). c. bipes is the only species with two antapical spines, c. skogsbergii and c. gouretti have three, and c. horrida, c. armata, c. reticulata, and c. aultii all have four. smaller spines also exist on the larger spines of c. horrida and c. gouretti which look like brushes on the tips of the large spines (fig. 47). each spine is made on the junction of four lists, forming a sort of cross shape when looking down the spine. the lists of antapical spines are fairly short and do not extend far out, but the lists of the ventral and dorsal spines can extend quite far and join up with the other lists on the body surface. as a dinoflagellate, ceratocorys have two flagella. one, the transverse flagellum, is lodged in the girdle, and the other, the longitudinal flagellum, exits the cell through the flagellar pore. the transverse flagellum provides both forward motion and spin to the cell, while the longitudinal flagellum acts as a rudder to steer with. environmental differences have an effect on cell morphology of c. horrida. when cultured in still water, >80% of the population is considered "long-spined" with spines almost one cell diameter in length. when the water is continuously agitated to simulate light wind or surface chop at ocean surface the "short-spine" morphotype will, over time, become the dominant cell type. this morphotype's ventral and dorsal spines tend to disappear, while the remaining four antapical spines are shorter and wider than that of the "long-spined" cells. furthermore, the cell volume halves, and mean vacuole size drops as well. reduction of spines is due to material resorption during endoskeleton transformation rather than as a result of cell division. once the water is returned to still conditions, the population will slowly recover back to being majority "long-spine" cells. in all cultures there is a small proportion of the population that is spineless, more angular in shape, and a cell volume approximately 1/3rd of the "long-spined" cells. the "long-spined" cells are both larger and denser than the "short-spined" cells but have a slower sinking rate than the "short-spine" cells. this is because the long spines provide more surface area, allowing the cell to take advantage of the viscosity of the water to reduce sinking. the "short-spined" morphotype's reduced swimming and faster sinking rate is likely an adaptation to avoid turbulent surface conditions and potential cell damage. the dinokaryon is u-shaped and located in the posterior of the cell in at least c. malayensis; there has been no description of the shape of the nucleus in other species in this genus. dinokaryons are the name for dinoflagellate nuclei, and are different from usual nuclei in that the dna is not organized in nucleosomes, there are no histones, and chromosomes are always condensed. life cycle this genus is only known to reproduce through binary fission, doubling their haploid genome to form diploid cells that then split off to form two haploid daughter cells. there is no information on whether or not ceratocorys reproduce sexually, or what that process might entail. when the cell splits, one daughter cell receives the four antapical spines and must regrow the dorsal and ventral spines, and the other receives the dorsal and ventral spines and must regrow the four antapical spines (fig. 48). when changing morphology from "long-spined" to "short-spined" and back, cells will fully convert to one morphology or the other before reproducing and switching between morphologies is an ability of each individual cell rather than a set phenotype due to changing genetics. its absence at low temperatures indicates that active reproduction likely does not happen below 20°c. there has been no evidence of a cyst stage for any organism in this genus. practical importance since c. horrida has nearly instantaneous bioluminescent reactions to different kinds of water flow, it is a good model organism for understanding plankton responses to water movement. studying the changes in bioluminescence in different types of fluid movement connects organism response to small-scale fluid processes, which are important for understanding the community dynamics of plankton. due to its bioluminescent capabilities and sensitivity to different environmental molecules, c. horrida has been used by rapid toxicity tests like qwiklite to detect levels of different man-made contaminants and toxins in aquatic systems by measuring the reduction in light production of the organisms. compared to toxicity tests that use organisms such as invertebrates or fish, testing using bioluminescent organisms such as c. horrida is far quicker and cheaper. though species selection for qwiklite tests should depend on study-specific factors, usage of c. horrida stands as a viable option for rapid toxicity tests, as its sensitivity is comparable to several commonly used standardized tests. presence of c. horrida has also been found to be an indicator of oceanic upwellings. despite its low abundance, it is one of the most common types of tropical peridinians, and so is also an indicator of tropical waters. furthermore, its sensitivity and inability to stand low temperatures makes it unlikely to indicate waters of tropical origins far from the source point.