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Douglas Y Shapiro - One of the best experts on this subject based on the ideXlab platform.
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spatial dispersion and nonmigratory spawning in the bluehead wrasse Thalassoma bifasciatum
Ethology, 2010Co-Authors: W Tecumseh, S Fitch, Douglas Y ShapiroAbstract:Earlier studies of the behavior of the bluehead wrasse Thalassoma bifasciatum have shown it to be a migratory spawner with large terminal-phase males defending temporary spawning territories. We describe a variant social structure where fish occupy permanent home ranges, spawn within or near these home ranges, and are not territorial. Movements of identified terminal-phase and intermediate males and females were mapped in the backreef areas of three coral reefs in Puerto Rico. Locations of spawns were then compared with these home-range maps. All fish used most or all of their morning home range during the afternoon spawning period. Both terminal-phase males and females spawned within or near their home ranges. Males were relatively tolerant of other males during the afternoon spawning period: only one in five encounters between large males resulted in aggressive chases. The location of chases bore no relation to spawning sites, areas of morning foraging, or to home-range borders. A Monte Carlo computer simulation was used to measure home-range dispersion of terminal-phase and intermediate males at our main site. If males were territorial, we should expect their home ranges to be significantly overdispersed within the cumulative area they occupied. During the first year male home ranges were overdispersed but during the second year they were randomly dispersed, even though the same number of terminal-phase males occupied the same study site both years. Differences in social behavior between backreef areas and other areas reported in the literature, and found in other portions of our reefs, may be related to differences in feeding ecology between populations and between different portions of the same reef.
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components of fertilization success in the bluehead wrasse Thalassoma bifasciatum
Behavioral Ecology, 2001Co-Authors: Christopher W. Petersen, Robert R Warner, Douglas Y Shapiro, Andrea MarconatoAbstract:In many species of marine organisms, males and females release gametes directly into the water column. Although free-spawning marine invertebrates appear to have highly variable fertilization success, in tropical reef fishes the average fertilization success is quite high, typically over 90%; nevertheless, substantial variation has been reported, and fertilization has a direct effect on fitness. We investigated the factors affecting fertilization success in natural spawnings of the bluehead wrasse, Thalassoma bifasciatum. During a two-year study at a site in St. Croix, we found extensive and predictable variation in fertilization success in pair spawns of this reef fish. Fertilization success averaged 95%, but was affected by the amount of sperm released, the water velocity at a site, the mating success of the male, and the size of the female. As sperm released in a spawn increases, and as water velocity at a site decreases, sperm concentrations should remain higher in the vicinity of eggs for a longer period of time, and both of these factors are correlated with increasing fertilization success. The recent history of individuals with partners or sites did not affect the fertilization success of their spawn. In an evolutionary context, the real and predictable variance in fertilization success in this species may influence the mating choices of males and females. However, there is currently no evidence that females use differences in fertilization success among males or sites in their reproductive decisions. Key words: bluehead wrasse; Coral reef fish; mate choice; fertilization; reproductive success; spawning; sperm limitation, Thalassoma bifasciatum. [Behav Ecol 12:237–245 (2001)]
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sexual conflict males with highest mating success convey the lowest fertilization benefits to females
Proceedings of The Royal Society B: Biological Sciences, 1995Co-Authors: Robert R Warner, Douglas Y Shapiro, Andrea Marcanato, Christopher W. PetersenAbstract:In natural populations of a coral reef fish (the bluehead wrasse, Thalassoma bifasciatum ), males with the highest daily mating success produce the fewest sperm per mating, and this is reflected in significantly lower fertilization rates. The average amount released by males in pair-mating was 3.3 x 10 6 spermatozoa, resulting in a fertilization rate of 96%. Sperm released per spawn declined with increasing mating success, so that females mating with the most successful males had less than 93% of their eggs fertilized. It is unlikely that high mating-success males are physiologically incapable of increasing sperm production, because younger males with different mating strategies have absolutely larger testes and higher daily sperm output. Feeding experiments suggest that high-success males are diverting energy from gamete production to other fitness-enhancing activities such as mate guarding. Females incur the cost of low sperm release by having fewer of their eggs fertilized. There are no obvious compensatory benefits to females from mating with high-success males.
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sperm economy in a coral reef fish Thalassoma bifasciatum
Ecology, 1994Co-Authors: Douglas Y Shapiro, Andrea Marconato, Tomoko YoshikawaAbstract:In many coral reef fishes, males face the evolutionary problems of how to allocate sperm among frequent, daily mating in order to maximize the number of eggs they fertilize. A method is developed and tested for collecting and counting the number of sperm and eggs released during separate spawns of the coral reef fish Thalassoma bifasciatum. The method was used to examine the pattern of sperm allocation for pair— and group—spawning males. The number of sperm released by pair—spawning males varied positively with the number of eggs released by their female mates and with female body size. The data suggest that males economize on sperm release by providing the minimum amount of sperm needed to fertilize the egg clutch of the female partner. Fertilization efficiency (the number of eggs fertilized by a given number of sperm) was higher with large females than it was with small females. Males differed significantly among themselves in sperm output per spawn, with some males consistently releasing more sperm than other males with same—sized females. Male—male differences were not due to differences in male body size, quality of the spawning site, or the apparent degree of water movement. The number of sperm released per spawn did not decline throughout the daily spawning period, a pattern that disproved one but not all possible patterns of sperm depletion. In group spawns, the total number of sperm released and the number released per male were respectively 50 and 6 times the number released in pair spawns, on average. Both of these measures increased significantly with the clutch size of the spawning female. Overall, sperm production is probably sufficiently costly that males have been selected to allocate sperm carefully among their frequent daily spawns.
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sex differentiation and gonadal development in the diandric protogynous wrasse Thalassoma bifasciatum pisces labridae
Journal of Zoology, 1993Co-Authors: Douglas Y Shapiro, Maria B RasottoAbstract:One hypothesis that would unify many of the apparently diverse patterns of gonadal differentiation in teleost fishes under a single conceptual scheme is that individuals develop in a female direction unless a masculinizing mechanism intervenes. We provided a descriptive test of this hypothesis in a diandric, protogynous wrasse in which males are produced through two, apparently different developmental sequences: ‘primary males’ develop testes as juveniles and remain male throughout life, while ‘secondary males’ develop ovaries as juveniles and later in adult life the functional ovary redifferentiates into a functional testis. The gonads of 128 individuals, from the smallest juveniles to full-sized adults, were examined histologically. Gonads of the smallest juveniles were undifferentiated or contained young oocytes with no ovarian cavity and no testicular tissue. As individuals increased in size, the proportion of oocytic gonads increased. The distribution of gonad types for larger individuals suggested that a portion ofthese oocytic gonads developed into ovaries, while another portion lost its oocytic elements and became testes. These patterns supported the hypothesis that the gonads of all individuals, including primary males, passed through an initial female phase prior to differentiating into an ovary or testis. The structure of primary testes was not identical to the structure of secondary testes. The critical difference between the two types lay in the presence of a large central cavity in the latter that was not present in the former. Positional differences in the duct system were only found in the posterior region of the gonad and were the consequence of a lateral internal split in the secondary gonad resulting from confluence of the central cavity.
Giacomo Bernardi - One of the best experts on this subject based on the ideXlab platform.
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evolution of coral reef fish Thalassoma spp labridae 1 molecular phylogeny and biogeography
Marine Biology, 2004Co-Authors: Giacomo Bernardi, G Bucciarelli, D Costagliola, D R Robertson, J B HeiserAbstract:Wrasses in the genus Thalassoma comprise 27 recognized species that occur predominantly on coral reefs and subtropical rocky reefs worldwide. The phylogenetic relationships for 26 species were examined based on two mitochondrial genes (cytochrome b and 16S rRNA) and one nuclear intron (the first intron of the ribosomal protein S7). Two closely related species, the bird-wrasses (Gomphosus varius Lacepede, 1801 and G. caerulaeus Lacepede, 1801), were also included in the analysis. These species grouped within the genus Thalassoma. Thalassoma newtoni (Osorio, 1891) from Sao Tome, which is generally synonymized with the Atlantic/Mediterranean Thalassoma pavo (Linnaeus, 1758) appears to be a valid species. Using a molecular clock, the genus was estimated to have originally diverged 8–13 million years ago, with Thalassoma ballieui (Vaillant and Sauvage, 1875) from Hawaii and Thalassoma septemfasciata Scott, 1959 from Western Australia as the ancestral species. Approximately 5–10 million years ago, a sudden burst of speciation resulted in seven clades, which were resolved with the sequence data. The terminal Tethyan event and the closing of the Isthmus of Panama were probably the major historical factors shaping the evolution of species in the genus Thalassoma. These data on the spatio-temporal pattern of speciation in the Indo-Pacific indicate that peripheral species have been generated at various times throughout the history of the genus, and that none of the widespread species are relatively young. Thus, there is no clear support for centrifugal (youngest at the periphery) versus centripetal (oldest at the periphery) modes of generation of species, two theories which have been used to account for geographic gradients in species diversity.
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evolution of coral reef fish Thalassoma spp labridae 2 evolution of the eastern atlantic species
Marine Biology, 2004Co-Authors: D Costagliola, Peter Wirtz, D R Robertson, J B Heiser, P Guidetti, Sergio Stefanni, Giacomo BernardiAbstract:The genetic relationships within and among congeneric species of marine fish from the Atlantic and the Mediterranean are poorly known. Relationships among all five species of the wrasse genus Thalassoma present in the Atlantic and the Mediterranean were examined using sequence data from the mitochondrial control region. Sampling was focused on the mid-Atlantic T. sanctaehelenae (Valenciennes, 1839) and T. ascensionis (Quoy & Gaimard, 1834), the eastern Atlantic T. newtoni (Osorio, 1891) from Sao Tome, and the eastern Atlantic/Mediterranean T. pavo (Linnaeus, 1758). Two western Atlantic species T. bifasciatum (Bloch, 1791) from the Caribbean and T. noronhanum (Boulenger, 1890) from Brazil served as outgroups. Tissues from a total of 132 individuals were sequenced. T. newtoni from Sao Tome preferentially grouped with the central Atlantic T. sanctaehelenae and T. ascensionis. T. pavo exhibits two distinct coloration patterns, one in the Cape Verde Islands and one in the eastern Atlantic Islands and Mediterranean. However, no genetic discontinuities between the Cape Verde Islands and the remaining samples or between Atlantic and Mediterranean individuals were found. Within Mediterranean populations of T. pavo, our data suggested the presence of a genetic break between eastern and western regions.
Andrea Marconato - One of the best experts on this subject based on the ideXlab platform.
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components of fertilization success in the bluehead wrasse Thalassoma bifasciatum
Behavioral Ecology, 2001Co-Authors: Christopher W. Petersen, Robert R Warner, Douglas Y Shapiro, Andrea MarconatoAbstract:In many species of marine organisms, males and females release gametes directly into the water column. Although free-spawning marine invertebrates appear to have highly variable fertilization success, in tropical reef fishes the average fertilization success is quite high, typically over 90%; nevertheless, substantial variation has been reported, and fertilization has a direct effect on fitness. We investigated the factors affecting fertilization success in natural spawnings of the bluehead wrasse, Thalassoma bifasciatum. During a two-year study at a site in St. Croix, we found extensive and predictable variation in fertilization success in pair spawns of this reef fish. Fertilization success averaged 95%, but was affected by the amount of sperm released, the water velocity at a site, the mating success of the male, and the size of the female. As sperm released in a spawn increases, and as water velocity at a site decreases, sperm concentrations should remain higher in the vicinity of eggs for a longer period of time, and both of these factors are correlated with increasing fertilization success. The recent history of individuals with partners or sites did not affect the fertilization success of their spawn. In an evolutionary context, the real and predictable variance in fertilization success in this species may influence the mating choices of males and females. However, there is currently no evidence that females use differences in fertilization success among males or sites in their reproductive decisions. Key words: bluehead wrasse; Coral reef fish; mate choice; fertilization; reproductive success; spawning; sperm limitation, Thalassoma bifasciatum. [Behav Ecol 12:237–245 (2001)]
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sperm economy in a coral reef fish Thalassoma bifasciatum
Ecology, 1994Co-Authors: Douglas Y Shapiro, Andrea Marconato, Tomoko YoshikawaAbstract:In many coral reef fishes, males face the evolutionary problems of how to allocate sperm among frequent, daily mating in order to maximize the number of eggs they fertilize. A method is developed and tested for collecting and counting the number of sperm and eggs released during separate spawns of the coral reef fish Thalassoma bifasciatum. The method was used to examine the pattern of sperm allocation for pair— and group—spawning males. The number of sperm released by pair—spawning males varied positively with the number of eggs released by their female mates and with female body size. The data suggest that males economize on sperm release by providing the minimum amount of sperm needed to fertilize the egg clutch of the female partner. Fertilization efficiency (the number of eggs fertilized by a given number of sperm) was higher with large females than it was with small females. Males differed significantly among themselves in sperm output per spawn, with some males consistently releasing more sperm than other males with same—sized females. Male—male differences were not due to differences in male body size, quality of the spawning site, or the apparent degree of water movement. The number of sperm released per spawn did not decline throughout the daily spawning period, a pattern that disproved one but not all possible patterns of sperm depletion. In group spawns, the total number of sperm released and the number released per male were respectively 50 and 6 times the number released in pair spawns, on average. Both of these measures increased significantly with the clutch size of the spawning female. Overall, sperm production is probably sufficiently costly that males have been selected to allocate sperm carefully among their frequent daily spawns.
Christopher W. Petersen - One of the best experts on this subject based on the ideXlab platform.
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components of fertilization success in the bluehead wrasse Thalassoma bifasciatum
Behavioral Ecology, 2001Co-Authors: Christopher W. Petersen, Robert R Warner, Douglas Y Shapiro, Andrea MarconatoAbstract:In many species of marine organisms, males and females release gametes directly into the water column. Although free-spawning marine invertebrates appear to have highly variable fertilization success, in tropical reef fishes the average fertilization success is quite high, typically over 90%; nevertheless, substantial variation has been reported, and fertilization has a direct effect on fitness. We investigated the factors affecting fertilization success in natural spawnings of the bluehead wrasse, Thalassoma bifasciatum. During a two-year study at a site in St. Croix, we found extensive and predictable variation in fertilization success in pair spawns of this reef fish. Fertilization success averaged 95%, but was affected by the amount of sperm released, the water velocity at a site, the mating success of the male, and the size of the female. As sperm released in a spawn increases, and as water velocity at a site decreases, sperm concentrations should remain higher in the vicinity of eggs for a longer period of time, and both of these factors are correlated with increasing fertilization success. The recent history of individuals with partners or sites did not affect the fertilization success of their spawn. In an evolutionary context, the real and predictable variance in fertilization success in this species may influence the mating choices of males and females. However, there is currently no evidence that females use differences in fertilization success among males or sites in their reproductive decisions. Key words: bluehead wrasse; Coral reef fish; mate choice; fertilization; reproductive success; spawning; sperm limitation, Thalassoma bifasciatum. [Behav Ecol 12:237–245 (2001)]
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sexual conflict males with highest mating success convey the lowest fertilization benefits to females
Proceedings of The Royal Society B: Biological Sciences, 1995Co-Authors: Robert R Warner, Douglas Y Shapiro, Andrea Marcanato, Christopher W. PetersenAbstract:In natural populations of a coral reef fish (the bluehead wrasse, Thalassoma bifasciatum ), males with the highest daily mating success produce the fewest sperm per mating, and this is reflected in significantly lower fertilization rates. The average amount released by males in pair-mating was 3.3 x 10 6 spermatozoa, resulting in a fertilization rate of 96%. Sperm released per spawn declined with increasing mating success, so that females mating with the most successful males had less than 93% of their eggs fertilized. It is unlikely that high mating-success males are physiologically incapable of increasing sperm production, because younger males with different mating strategies have absolutely larger testes and higher daily sperm output. Feeding experiments suggest that high-success males are diverting energy from gamete production to other fitness-enhancing activities such as mate guarding. Females incur the cost of low sperm release by having fewer of their eggs fertilized. There are no obvious compensatory benefits to females from mating with high-success males.
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Variable pelagic fertilization success : implications for mate choice and spatial patterns of mating
Ecology, 1992Co-Authors: Christopher W. Petersen, Robert R Warner, Sarah Cohen, Helen C. Hess, Amy T. SewellAbstract:Fertilization success was measured in the bluehead wrasse, Thalassoma bifasciatum, a tropical reef fish with external fertilization of pelagic eggs. This species exhibits intraspecific variation in its spawning behavior; females either spawn with single males (pair spawning) or spawn with a group of at least three and often > 20 males (group spawning). Fertilization success averaged -75% and did not differ between pair and group spawning, despite an estimated 80-fold increase in sperm release in group spawns. There was also no evidence that pair-spawning males suffered sperm depletion over the course of the spawning period. Thalassoma bifasciatum occurs in a variety of habitats and is exposed to varying levels of water turbulence. Fertilization success varied among days, and decreased with rougher water conditions. Within a reef, the calmer spawning sites behind the reef relative to the current had higher fertilization success than those along the side of the reef. These data suggest that while the type of spawning occurring at the site does not affect selection for fertilization success, females may gain fertilizations by selecting partic- ular locations or periods of calmer water conditions to spawn. This is an alternative hypothesis to explain temporal and spatial patterns of mating. We provide detailed methods on how to accurately obtain data on fertilization success. Our technique can be used to study natural spawning in a wide variety of reef fishes and other marine organisms with pelagic eggs, external fertilization, and predictable spawning.
Robert R Warner - One of the best experts on this subject based on the ideXlab platform.
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components of fertilization success in the bluehead wrasse Thalassoma bifasciatum
Behavioral Ecology, 2001Co-Authors: Christopher W. Petersen, Robert R Warner, Douglas Y Shapiro, Andrea MarconatoAbstract:In many species of marine organisms, males and females release gametes directly into the water column. Although free-spawning marine invertebrates appear to have highly variable fertilization success, in tropical reef fishes the average fertilization success is quite high, typically over 90%; nevertheless, substantial variation has been reported, and fertilization has a direct effect on fitness. We investigated the factors affecting fertilization success in natural spawnings of the bluehead wrasse, Thalassoma bifasciatum. During a two-year study at a site in St. Croix, we found extensive and predictable variation in fertilization success in pair spawns of this reef fish. Fertilization success averaged 95%, but was affected by the amount of sperm released, the water velocity at a site, the mating success of the male, and the size of the female. As sperm released in a spawn increases, and as water velocity at a site decreases, sperm concentrations should remain higher in the vicinity of eggs for a longer period of time, and both of these factors are correlated with increasing fertilization success. The recent history of individuals with partners or sites did not affect the fertilization success of their spawn. In an evolutionary context, the real and predictable variance in fertilization success in this species may influence the mating choices of males and females. However, there is currently no evidence that females use differences in fertilization success among males or sites in their reproductive decisions. Key words: bluehead wrasse; Coral reef fish; mate choice; fertilization; reproductive success; spawning; sperm limitation, Thalassoma bifasciatum. [Behav Ecol 12:237–245 (2001)]
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large mating aggregations and daily long distance spawning migrations in the bluehead wrasse Thalassoma bifasciatum
Environmental Biology of Fishes, 1995Co-Authors: Robert R WarnerAbstract:The mating system of the labrid fishThalassoma bifasciatum has been extensively described in the literature, and the species has formed the basis for much work in ecology and behavior. However, most work in the past on this species has concentrated in small patch reef habitats. Here I describe a different mating pattern in bluehead wrasses occurring on a large, linear barrier reef in St. Croix, U.S. Virgin Islands. On this reef, very large group-mating aggregations (> 10000 fish) form daily at a single area on the forepart of the reef. Tagging studies showed that fishes are faithful to particular feeding schools arrayed along the forereef, and that they migrate to the spawning grounds along a specific path from distances more than 1.5 km away. No mating appears to occur in other upcurrent areas of the forereef. One-way migration times averaged 52 min from the farthest site studied, and feeding does not occur en route. Despite large differences in time spent in migration, no significant differences existed in fecundity or frequency of spawning among females living at different distances from the mating aggregation. The only apparent differences was a significantlyhigher growth rate in the fishes residing farthest from the aggregation. This higher growth rate corresponded to a higher overall feeding rate in the distant location, suggesting that food intake can more than compensate for the increased costs of migration.
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sexual conflict males with highest mating success convey the lowest fertilization benefits to females
Proceedings of The Royal Society B: Biological Sciences, 1995Co-Authors: Robert R Warner, Douglas Y Shapiro, Andrea Marcanato, Christopher W. PetersenAbstract:In natural populations of a coral reef fish (the bluehead wrasse, Thalassoma bifasciatum ), males with the highest daily mating success produce the fewest sperm per mating, and this is reflected in significantly lower fertilization rates. The average amount released by males in pair-mating was 3.3 x 10 6 spermatozoa, resulting in a fertilization rate of 96%. Sperm released per spawn declined with increasing mating success, so that females mating with the most successful males had less than 93% of their eggs fertilized. It is unlikely that high mating-success males are physiologically incapable of increasing sperm production, because younger males with different mating strategies have absolutely larger testes and higher daily sperm output. Feeding experiments suggest that high-success males are diverting energy from gamete production to other fitness-enhancing activities such as mate guarding. Females incur the cost of low sperm release by having fewer of their eggs fertilized. There are no obvious compensatory benefits to females from mating with high-success males.
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Variable pelagic fertilization success : implications for mate choice and spatial patterns of mating
Ecology, 1992Co-Authors: Christopher W. Petersen, Robert R Warner, Sarah Cohen, Helen C. Hess, Amy T. SewellAbstract:Fertilization success was measured in the bluehead wrasse, Thalassoma bifasciatum, a tropical reef fish with external fertilization of pelagic eggs. This species exhibits intraspecific variation in its spawning behavior; females either spawn with single males (pair spawning) or spawn with a group of at least three and often > 20 males (group spawning). Fertilization success averaged -75% and did not differ between pair and group spawning, despite an estimated 80-fold increase in sperm release in group spawns. There was also no evidence that pair-spawning males suffered sperm depletion over the course of the spawning period. Thalassoma bifasciatum occurs in a variety of habitats and is exposed to varying levels of water turbulence. Fertilization success varied among days, and decreased with rougher water conditions. Within a reef, the calmer spawning sites behind the reef relative to the current had higher fertilization success than those along the side of the reef. These data suggest that while the type of spawning occurring at the site does not affect selection for fertilization success, females may gain fertilizations by selecting partic- ular locations or periods of calmer water conditions to spawn. This is an alternative hypothesis to explain temporal and spatial patterns of mating. We provide detailed methods on how to accurately obtain data on fertilization success. Our technique can be used to study natural spawning in a wide variety of reef fishes and other marine organisms with pelagic eggs, external fertilization, and predictable spawning.
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social control of sex change in the bluehead wrasse Thalassoma bifasciatum pisces labridae
The Biological Bulletin, 1991Co-Authors: Robert R Warner, Stephen E SwearerAbstract:While the bluehead wrasse has long been used as a test species in sex allocation theory, there is no published evidence that sex change in this species is socially controlled. Here we show that removal of large terminal color phase (TP) males from local populations leads to sex and color change in the largest initial color phase (IP) females. In contrast, no sex changes occurred in control populations in which the TP males were handled but replaced, and in which only the IP males were removed. The response to removals was quite precise, resulting in a nearly one-to-one replacement of TP males. Large individuals that had been seen spawning as female males on the day prior to the manipulation, initiated male behaviors within minutes of the removal of the TP males and spawned in the male role the same day. Color changes were noted within a day and were distinct within four days. Sex change was verified by histological examination of the gonads of the changing individuals. All had functional testes, and all s...