Threespot Damselfish Research Articles

Clownfish triggers plasticity in the acoustic communication of the three-spot damselfish

Clownfish triggers plasticity in the acoustic communication of the three-spot damselfish

Chromosome-level genome of the three-spot damselfish, Dascyllus trimaculatus.

Damselfishes (Family: Pomacentridae) are a group of ecologically important, primarily coral reef fishes that include over 400 species. Damselfishes have been used as model organisms to study recruitment (anemonefishes), the effects of ocean acidification (spiny damselfish), population structure, and speciation (Dascyllus). The genus Dascyllus includes a group of small-bodied species, and a complex of relatively larger bodied species, the Dascyllus trimaculatus species complex that is comprised of several species including D. trimaculatus itself. The three-spot damselfish, D. trimaculatus, is a widespread and common coral reef fish species found across the tropical Indo-Pacific. Here, we present the first-genome assembly of this species. This assembly contains 910 Mb, 90% of the bases are in 24 chromosome-scale scaffolds, and the Benchmarking Universal Single-Copy Orthologs score of the assembly is 97.9%. Our findings confirm previous reports of a karyotype of 2n = 47 in D. trimaculatus in which one parent contributes 24 chromosomes and the other 23. We find evidence that this karyotype is the result of a heterozygous Robertsonian fusion. We also find that the D. trimaculatus chromosomes are each homologous with single chromosomes of the closely related clownfish species, Amphiprion percula. This assembly will be a valuable resource in the population genomics and conservation of Damselfishes, and continued studies of the karyotypic diversity in this clade.

Spatial and temporal variation in the genetic structure of Dascyllus trimaculatus (Pomacentridae) in the Bohol Sea

The potential of microsatellite markers to detect the spatial and temporal genetic structure of reef fish populations within a linear distance of 300 km in the absence of geographic barriers was tested in the Bohol Sea, central Philippines, using the three-spot damselfish Dascyllus trimaculatus. A total of 672 samples from 7 populations in the Bohol Sea were processed to determine temporal and spatial patterns of genetic variability using ten previously developed and tested microsatellite markers. The extent of differentiation was determined based on a variance-based measure of population structure FST and RST, and genetic distances Ds , DA, and dm2, each of which makes different assumptions on the process of migration, mutation, selection, and genetic drift. Patterns of temporal and spatial variation were consistent among 36 possible pairs of populations. Reef groups are defined as (1) the Mantigue-Dinagat on the northeast edge of the Bohol Sea; (2) the Selinog and Dapitan islands, to the southwest and central Bohol sea populations (3) Apo and (4) Sumilon to the west, and (5) Balicasag group to the northwest. The presence of structure in the absence of geographic barriers suggests the influence of strong surface circulation patterns that differ from the east to the west side of the region. The consistency of a population’s genetic signatures over multiple temporal sampling dates implies strong habitat selection for genotypes. Genetic breaks were detected at a distance 4x greater than the marine protected area’s average size, suggesting a minimum linear distance for networking of MPAs should be expanded to this scale. KEYWORDS: Conservation, Hardy-Weinberg equilibrium, marine protected area, microsatellite markers, population genetics, reef fish

Microhabitat use by recently settled Sparisoma parrotfishes: ontogenetic shifts and association with algal-gardening damselfishes

Little is known about microhabitat use by Caribbean parrotfishes soon after settlement from the plankton. We monitored the abundance and distribution of recently settled Sparisoma spp. (likely mostly S. viride with some S. aurofrenatum) on 6 × 6 m quadrats (n = 9) on the fringing reef front in Barbados (West Indies) every 15 d for 6 mo. Each quadrat was divided into 1 m2 cells to examine associations between substrate composition and recruit (<1.3 cm standard length, SL) and small juvenile (1.3-3 cm SL) abundance. Recruits and small juveniles tended to use some cells more than others, and their distribution partially overlapped. Both were associated with long turf algae on dead coral. However, small juveniles were also associated with crustose coralline algae and substrate elevation, suggesting a partial ontogenetic change in microhabitat use. Microhabitat associations were similar to those of co-occurring algal-gardening longfin damselfish Stegastes diencaeus and threespot damselfish S. planifrons. Whereas Sparisoma recruits overlapped with longfins and to a lesser extent with threespots, small juveniles overlapped only with threespots. Some of the microhabitat associations with recruits and small juveniles at the cell scale were also found across quadrats. We suggest that the reef front is an important habitat for recently settled Sparisoma in Barbados, where they rely on being cryptic and solitary within turf algae gardens defended by damselfishes to minimize predation. After some growth, they perform a microhabitat shift, perhaps due to increased damselfish aggression. Thus, the early post-settlement dynamics of Caribbean Sparisoma might be strongly influenced by substrate modification by algal-gardening damselfishes.

Response to underwater laser pointer in the Orange-finned Anemonefish Amphiprion chrysopterus and three-spot damselfish Dascyllus trimaculatus.

Response of orange-finned anemonefish Amphiprion chrysopterus and three-spot damselfish Dascyllus trimaculatus to red laser-pointer light was studied in Mo'orea, French Polynesia. Four magnificent anemones Heteractis magnifica and their resident fish were observed for typical behaviours (biting, chasing, hiding, posing, lunging and retreating) with and without exposure to laser-pointer light. Lunging behaviour increased significantly for both fish species upon exposure to laser-pointer light; none of the other behaviours changed significantly. We advance the hypothesis that orange-finned anemonefish and three-spot damselfish interpret laser pointer stimulation as a territorial threat.

RADseq analyses reveal concordant Indian Ocean biogeographic and phylogeographic boundaries in the reef fish Dascyllus trimaculatus.

Population genetic analysis is an important tool for estimating the degree of evolutionary connectivity in marine organisms. Here, we investigate the population structure of the three-spot damselfish Dascyllus trimaculatus in the Red Sea, Arabian Sea and Western Indian Ocean, using 1174 single nucleotide polymorphisms (SNPs). Neutral loci revealed a signature of weak genetic differentiation between the Northwestern (Red Sea and Arabian Sea) and Western Indian Ocean biogeographic provinces. Loci potentially under selection (outlier loci) revealed a similar pattern but with a much stronger signal of genetic structure between regions. The Oman population appears to be genetically distinct from all other populations included in the analysis. While we could not clearly identify the mechanisms driving these patterns (isolation, adaptation or both), the datasets indicate that population-level divergences are largely concordant with biogeographic boundaries based on species composition. Our data can be used along with genetic connectivity of other species to identify the common genetic breaks that need to be considered for the conservation of biodiversity and evolutionary processes in the poorly studied Western Indian Ocean region.

A 3000 year record of Caribbean reef urchin communities reveals causes and consequences of long‐term decline in Diadema antillarum

Urchins are the last abundant grazers of macroalgae on most Caribbean reefs following the historical overexploitation of herbivorous fishes. The long‐spined urchin Diadema antillarum was particularly effective at controlling macroalgae and facilitating coral dominance on Caribbean reefs until its ecological extinction from a catastrophic disease epidemic in the early 1980s. Despite their important role in the structure and functioning of Caribbean reef ecosystems, the natural dynamics of Caribbean reef urchin communities are poorly known due to the paucity of ecological survey data prior to large‐scale human disturbances and the Diadema dieoff. To help resolve the baseline abundances and ecological roles of common urchin taxa, we track changes in urchin abundance and composition over the past 3000 yr from analysis of subfossil urchin spines preserved in reef matrix cores collected in Caribbean Panama. Echinometra consistently dominated the subfossil spine assemblage, while Diadema was consistently rare in the subfossil record in this region. Rather than increasing during a period of heightened human exploitation of their fish competitors and predators, Diadema began declining over a millennium ago. Convergent cross mapping (CCM) causality analyses reveal that Diadema abundance is causally related to coral community composition. Diadema is negatively affected by Acropora cervicornis dominance, likely due to the tight association between this coral and the threespot damselfish, an effective Diadema competitor. Conversely, Diadema positively affects the abundance of the coral Madracis mirabilis, possibly via its control of macroalgae. Causal relationships were not detected among abundances of individual urchin taxa, indicating that inter‐specific echinoid competition is not a factor limiting Diadema recovery. Our detailed record of prehistorical and historical urchin community dynamics suggests that the failure of Diadema to recover over 30 yr after its mass mortality event may be due in part to the prey release of damselfish following the long‐term overfishing of piscivorous fishes.

Vertical and horizontal genetic connectivity in Chromis verater, an endemic damselfish found on shallow and mesophotic reefs in the Hawaiian Archipelago and adjacent Johnston Atoll.

Understanding vertical and horizontal connectivity is a major priority in research on mesophotic coral ecosystems (30–150 m). However, horizontal connectivity has been the focus of few studies, and data on vertical connectivity are limited to sessile benthic mesophotic organisms. Here we present patterns of vertical and horizontal connectivity in the Hawaiian Islands-Johnston Atoll endemic threespot damselfish, Chromis verater, based on 319 shallow specimens and 153 deep specimens. The mtDNA markers cytochrome b and control region were sequenced to analyze genetic structure: 1) between shallow (<30 m) and mesophotic (30–150 m) populations and 2) across the species' geographic range. Additionally, the nuclear markers rhodopsin and internal transcribed spacer 2 of ribosomal DNA were sequenced to assess connectivity between shallow and mesophotic populations. There was no significant genetic differentiation by depth, indicating high levels of vertical connectivity between shallow and deep aggregates of C. verater. Consequently, shallow and deep samples were combined by location for analyses of horizontal connectivity. We detected low but significant population structure across the Hawaiian Archipelago (overall cytochrome b: ΦST = 0.009, P = 0.020; control region: ΦST = 0.012, P = 0.009) and a larger break between the archipelago and Johnston Atoll (cytochrome b: ΦST = 0.068, P<0.001; control region: ΦST = 0.116, P<0.001). The population structure within the archipelago was driven by samples from the island of Hawaii at the southeast end of the chain and Lisianski in the middle of the archipelago. The lack of vertical genetic structure supports the refugia hypothesis that deep reefs may constitute a population reservoir for species depleted in shallow reef habitats. These findings represent the first connectivity study on a mobile organism that spans shallow and mesophotic depths and provide a reference point for future connectivity studies on mesophotic fishes.

Differences in composition of territories in relation to behaviour, stage, and depth of the three-spot damselfish, Stegastes planifrons, in Caribbean coral reefs

Coral reef diversity is correlated with the depth at which the reefs are found, the energy available for biological processes, and the species’ roles and presence throughout the food chain. Can a specific species activity alter the whole ecosystem? Can a small-scale, short-term activity such as fish behaviour have a long-term effect on a larger scale, that of the reef? Can the life stage of a species mediate substrate competition? The three-spot damselfish (Stegastes planifrons) is hypothesized to regulate competition between substrate coverage by actively farming – protecting from herbivores and weeding – in order to regulate the algal species composition and percent coverage of the reef. This behaviour is observed in both juvenile and adult fish. Deeper patches are predicted to have less coral diversity and higher algal diversity; juvenile fish are predicted to have less diversity in their patches than adults. Coral and algal diversity are hypothesized to be negatively correlated. In this study, behaviour of the S. planifrons was classified into one of four categories (active patrolling, passing patrolling, farming, and hiding) and palatable algae surface area coverage was digitized from photographs; life stage was either juvenile or adult. Coral and algal genus diversity were measured along a depth gradient of 0-16 m where the diversity of the reef was thought to be the highest. A three-way ANCOVA was performed to test whether fish behaviour (a small-scale, short-term process), depth, or fish development stage (juvenile or adult) had a significant effect on coral or algal diversity (a large-scale, long-term process). Results showed a significant effect of fish behaviour category on algal genera diversity, and a significant effect of depth on both algal and coral genera diversity. Farming yielded significantly more algal coverage than hiding. This study shows that small-scale, short-term behaviours by S. planifrons can have an effect on algal genera diversity on coral reefs in Utila, Honduras.&#x0D; &#x0D; Keywords: Stegastes planifrons (three-spotted damselfish); behaviours (short-term, small-scale); stage of development (juvenile, adult); depth; coral reef and algal diversity (long-term, large-scale); damselfish territories

Changing Patterns of Microhabitat Utilization by the Threespot Damselfish, Stegastes planifrons, on Caribbean Reefs

BackgroundThe threespot damselfish, Stegastes planifrons (Cuvier), is important in mediating interactions among corals, algae, and herbivores on Caribbean coral reefs. The preferred microhabitat of S. planifrons is thickets of the branching staghorn coral Acropora cervicornis. Within the past few decades, mass mortality of A. cervicornis from white-band disease and other factors has rendered this coral a minor ecological component throughout most of its range.Methodology/Principal FindingsSurvey data from Jamaica (heavily fished), Florida and the Bahamas (moderately fished), the Cayman Islands (lightly to moderately fished), and Belize (lightly fished) indicate that distributional patterns of S. planifrons are positively correlated with live coral cover and topographic complexity. Our results suggest that species-specific microhabitat preferences and the availability of topographically complex microhabitats are more important than the abundance of predatory fish as proximal controls on S. planifrons distribution and abundance.Conclusions/SignificanceThe loss of the primary microhabitat of S. planifrons—A. cervicornis—has forced a shift in the distribution and recruitment of these damselfish onto remaining high-structured corals, especially the Montastraea annularis species complex, affecting coral mortality and algal dynamics throughout the Caribbean.

Territoriality and Aggression in the Threespot Damselfish (Pisces; Pomacentridae): An Experimental Study of Causation

Based on a series of correlations and the results of several experimental series on the territorial behavior of the threespot damselfish Eupomacentrus planifrons, a two-component system of the causation of territorial aggression is proposed. The first component, spatial commitment, determines the size of the area defended; the second, attack readiness, determines the vigor of such defense. The two differ in their responses to such factors as social isolation and repeated conspecific stimulation (and stimulation from non-related fishes). By their interaction, these two independent systems can account for not only many of the apparently contradictory results reported in the literature concerning the causation of aggressive behavior (such as the effects of social isolation), but also the stability of social systems based on territoriality. Forms of territorial advertisement, such as bird song and poster-coloration, are considered in terms of this two-component system.

Use of Copepods as Live Feed for Larviculture of Damselfishes

It is well established that small-sized live feed with sufficient DHA, EPA and ARA as starter feed is the key factor for the success in larviculture of marine fishes with altricial larvae having limited yolk, which are in an undeveloped state at hatching. Copepods form a major component of the natural diet of many fish larvae and the wide range of body sizes of copepods both within and between species is extremely useful for employing the early stage nauplii and copepodites as starter feed for very small larvae with small mouth opening. Improved survival, growth and normal pigmentation have been documented in the larviculture of several marine finfishes reared with the early stage nauplii and copepodites. This is generally attributed to the levels of DHA, EPA and or arachidomic acid (ARA) in the diet and particularly to the DHA: EPA ratio in the diet. Two species of copepods viz. Euterpina acutifrons, a harpacticoid copepod and Pseudodiaptomus serricaudatus, a calanoid copepod were selected and cultured. They were employed as starter feed for the larviculture of three species of damsel fishes viz. the three spot damselfish, Dascyllus trimaculatus, the humbug damselfish, Dascyllus aruanus and the blue damselfish, Pomacentrus caeruleus. It was found that co-culturing of copepods in greenwater in the larviculture tank is the most effective method for initiating the exogenous feeding of the species studied.

A Comparison of Damselfish Densities on Live Staghorn Coral (Acropora cervicornis) and Coral Rubble in Dry Tortugas National Park

Over the past 30 years, cold events and disease have reduced much of the live Acropora cervicornis (Staghorn Coral) in Dry Tortugas National Park (DTNP), FL to fields of coral rubble. It is unclear how the resulting loss of three-dimensional reef structure has affected density and distribution of reef-dependent damselfishes. We compared densities of Stegastes adustus (Dusky Damselfish), Stegastes leucostictus (Beaugregory Damselfish), Microspathodon chrysurus (Yellowtail Damselfish), Stegastes planifrons (Three-spot Damselfish) and Stegastes variabilis (Cocoa Damselfish) inhabiting DTNP's last live Staghorn Coral formation with densities from surrounding coral rubble. Live Staghorn Coral supported a 65% higher damselfish density compared to coral rubble. Density of Dusky, Cocoa, Beaugregory, Yellowtail and Three-spot Damselfish on coral rubble (0.11, 0.58, 0.74, 0.02, and 0.06 fish/m2, respectively) was less than that found on living Staghorn Coral colonies (2.03, 0.45, 0.25, 0.50, and 0.96 fish/m2, respectively). Dusky Damselfish dominated the live Staghorn Coral site, while Cocoa and Beaugregory Damselfish dominated the coral rubble site. Juvenile density was ten times greater on coral rubble than on live Staghorn Coral, whereas adults had highest densities on live Staghorn Coral.

The effect of community on the territorial behavior of the threespot damselfish

I examined the hypothesis that animals alter their behavior in response to changes at the community scale of organization, rather than simply reacting to a sequential set of independent interactions with other organisms. The focal species was the threespot damselfish, Stegastes planifrons,a territorial coral reef fish that experiences a high degree of variation in community composition. Field observations of individual threespot damselfish showed a significant increase in the amount of time spent on active territorial defense when the community contained greater proportions of food competitors. Territorial behavior also increased concurrently with higher species diversity in the community. However, no behavioral change was observed in response to the total number of fish entering the defended territory, suggesting that threespot damselfish are responding to more complex environmental cues associated with community structure rather than simple density.

Genetic evidence for two distinct clades in a French Polynesian population of the coral reef three-spot damselfish Dascyllus trimaculatus

Previous studies have shown that the three-spot damselfish species complex [Dascyllus albisella Gill, D. auripinnis Randall and Randall, D. strasburgi Klausewitz, D. trimaculatus (Ruppell)] is an assemblage of five geographically distinct clades. The one exception was a single D. trimaculatus from French Polynesia, which grouped with "Pacific Rim" individuals. In the present study, an additional 252 individuals from French Polynesia collected between June 1996 and January 2002 were analyzed using PCR amplifications, restriction fragment length polymorphisms, and DNA sequencing of the mitochondrial control region. The French Polynesian D. trimaculatus belong to two distinct clades. One clade comprising 96% of the individuals includes haplotypes found only in French Polynesia. The other clade (4% of the individuals) is comprised of haplotypes that cluster with "Pacific Rim" individuals, a clade with widespread distribution from Japan to the Line Islands and from Wallis to Palau. Present data suggest that a small number of larvae from northwestern reefs (possibly Line Islands) may have occasionally reached and colonized French Polynesian reefs.

Multidimensional polarization sensitivity in damselfishes.

Using electroretinogram recording and microspectrophotometry we investigated spectral sensitivity and ultraviolet polarization sensitivity in three species of coral reef fishes commonly known as damselfishes. Here we show that three species of damselfishes (three-spot damselfish, Dascyllus trimaculatus; blacktail damselfish, D. melanurus; and blue-green chromis, Chromis viridis) have four classes of cone photoreceptors (lambda(max) ranges: ultraviolet 357-367 nm; short wavelength-sensitive 469-478 nm; medium wavelength-sensitive 482-493 nm; long wavelength-sensitive 512-524 nm; rods 499-500 nm). The three species shared similar combined spectral sensitivity but surprisingly complicated and varied polarization sensitivity. Damselfish examined in this study have three and four channel polarization sensitivity, the most complex polarization sensitivity recorded for any vertebrate. Such capacity could play an important role in mediating a conspecific visual communication network utilizing polarized light signals in the coral reef environment.

Gut characteristics and assimilation efficiencies in two species of herbivorous damselfishes (Pomacentridae: Stegastes dorsopunicans and S. planifrons)

The morphological and physiological mechanisms by which marine herbivores assimilate energy and nutrients from primary producers and transfer them to higher trophic levels of reef ecosystems are poorly understood. Two wide-ranging Caribbean fishes, the dusky damselfish, Stegastesdorsopunicans, and the threespot damselfish, S. planifrons, defend territories on patch reefs in the Archipelago de San Blas, Republic of Panama. We examined how relative intestine length and retention time influence digestion and absorption of energy and nutrients in these fishes. The dusky damselfish has a relative intestine length (RIL=intestine length/standard length) of 1.2 and a Zihler index {ZI=intestine length (mm)/10[mass(g)1/3]} of 3.4. These values are significantly lower (PRIL=PZI 0.05) for both dusky (6.6 h) and threespot damselfish (6.5 h). Thus, food travels the length of the threespot damselfish intestine ~2.5 times faster than it does in the dusky damselfish intestine. Levels of protein, carbohydrate, and lipid are significantly (0.003<P<0.030) higher in the feces of dusky damselfish than in the feces of threespot damselfish, when both species were fed a natural diet of benthic diatoms collected from damselfish territories. This indicates threespot damselfish have a greater nutrient-specific and total assimilation efficiency than do dusky damselfish. Furthermore, when fed an artificial pellet diet, protein absorption efficiency differed significantly (P=0.014) between species; threespot damselfish absorbed 98.3% of dietary protein, whereas dusky damselfish absorbed 96.4% of dietary protein.

Do cleaning stations affect the distribution of territorial reef fishes?

We investigated the role of cleaning stations in determining the distribution of territorial reef species. Cleaner fish reduce their clients' ectoparasite loads and, therefore, proximity to cleaning stations should be advantageous for territorial fish. We focused on five damselfish species which hold permanent territories and cleaning stations occupied by cleaning gobies (Elacatinus spp.) on a Caribbean reef. Contrary to our predictions of higher densities near cleaning stations, we found that bicolor damselfish were less abundant near cleaning stations than at ecologically similar points without cleaning gobies whereas no effects were seen for longfin, dusky, yellowtail, and threespot damselfish. In addition, although damselfish densities were higher in the immediate vicinity of cleaning stations than 1.5–3 m away for most species, this was also the case at points without cleaners. Because cleaning stations are usually located on prominent coral heads or sponges, the overall significant attraction of damselfish to such structures, whether occupied by cleaning gobies or not, could reflect attraction to past or potential cleaning stations. However, it is more likely that interspecific competition and/or the low benefits of being cleaned at our study site prevent aggregation around cleaners. Cleaning stations may play only a minor role in determining the distribution of territorial reef fishes.

Species boundaries, populations and colour morphs in the coral reef three–spot damselfish ( Dascyllus trimaculatus ) species complex

Coloration patterns of tropical reef fishes is commonly used for taxonomic purposes, yet few studies have focused on the relationship between species boundaries and coloration types. The three-spot damselfish (Dascyllus trimaculatus) species complex comprises four species that vary both in geographical ranges and colour patterns making them an ideal model to study these relationships. We analysed the mitochondrial control region of 122 individuals from all four species collected from 13 localities. Individuals from two species (Dascyllus albisella and D. strasburgi) grouped into monophyletic clades, while the two other species (D. trimaculatus and D. auripinnis) were found to be paraphyletic. Coloration patterns were therefore not found to be good predictors of genetic isolation. In contrast, geographical origin was always consistent with the observed genetic pattern.

Gonadal development and mode of sexuality in a coral‐reef damselfish, Dascyllus trimaculatus

AbstractThe process of early gonadal development and the mode of sexuality were examined in the three‐spot damselfish Dascyllus trimaculatus. All gonads developed an ovarian lumen and primary‐growth‐stage oocytes after an initially undifferentiated state. From this ovarian state or from more developed ovaries, some gonads redifferentiated into testes. None of 130 individuals examined had a gonad containing degenerating vitellogenic oocytes and proliferating spermatogenic tissue. Nineteen individuals, however, had a gonad containing degenerating cortical–alveolus stage oocytes and proliferating spermatogenic tissue. The size of these individuals overlapped with the female size range in which most females were still in the middle of the maturation process or the smallest female size class in which most females had vitellogenic oocytes. This suggests that the transition toward maleness in these individuals is likely to have occurred after oocytes in their gonads attained cortical–alveolus stage, but before their final maturation and spawning as females, and that the protogynous pattern of gonadal development in D. trimaculatus is non‐functional. The observed protogynous pattern seems to have been present in the common ancestor of the genus and have been retained in this descendant species.