Planktonic larval duration of one hundred species of Pacific and Atlantic damselfishes (Pomacentridae)

The plankton larval duration for 100 species of Pacific and Atlantic damselfishes was estimated from daily growth increments on the otolith of juvenile fish collected at various localities between July 1987 and September 1988. For newly-settled fishes, larval duration was determined by counting the entire number of increments present on the otolith, while for older juveniles estimates were made by counting the number of increments between the center of the otolith and a mark corresponding to settlement. We document the development of otolith formation during the period when eggs are incubated on the reef and show that daily increments are only accreted after larvae hatch and enter the planktonic phase. The planktonic larval duration for damselfish is shorter and less variable, both between and within species, compared to other groups of reef fishes such as wrasses and surgeonfishes. Larval duration ranged from 12 to 39 d. Average duration between species ranged from 13.1 to 35.2 d. The time spent in the plankton was not significantly correlated with geographic distribution when evaluated among species, however, genera with confined regional distribution have a shorter mean larval life than do widely distributed genera. Size at settlement was positively correlated with time spent in the plankton among species, but a significant correlation between these variables was only evident within one of ten species. The low variance in planktonic larval duration within species indicates that most damselfish are unable to delay metamorphosis following competency. This inability to postpone settlement limits the potential for dispersal, especially when dispersal time between suitable habitats is greater than about 30 d.     

Growth,dispersal, and identification of planktonic labrid and pomacentrid reef-fish larvae in the eastern Pacific Ocean

Planktonic larvae of six genera of labrid and pomacentrid reef fishes were captured in march 1985 in the eastern Pacific Ocean several hundred kilometers from the nearest reefs. The larvae were identified to genus by fin-ray counts as well as by comparison of their larval otolith morphology with that of known species. The larval otolith morphologies of known species were derived from measurements of the larval otolith embedded within the otoliths of settled juveniles (as delineated by the daily otolith-increment marks corresponding to the late larval period). The body morphology and melanophore patterns of the eastern Pacific labird and pomacentrid larvae closely matched those of congeneric larvae described from other oceans. Growth rates of larvae less than about 70 d old were similar between taxa (from 0.13 to 0.19 mm d^-1). After about 70 d in the plankton, labrid larvae grew much more slowly (0.06 mm d^-1 in Xyrichtys sp.). Labrid larvae had long larval durations (up to 131 d in Xyrichtys sp.), while the larval lives of the pomacentrids appeared to be shorter and much less variable. Larvae of many different ages occurred within the same water mass, and young cohorts of larvae appeared continuously over the sampling period. Some larvae were as young as 21 d, indicating that reef-fish larvae are capable of rapid long-distance dispersal (at least 18 km d^-1).     

Regional differences in duration of the planktonic larval stage of reef fishes in the eastern Pacific Ocean

Regional variation in the duration of the planktonic larval phase of three species of reef fishes, Thalassoma lucasanum (Labridae), Stegastes flavilatus, and Microspathodon dorsalis (Pomacentridae) was investigated between 1982 and 1991 at several sites in the tropical eastern Pacific over a distance of 3500 km, encompassing virtually their entire range of distribution. Durations of the larval phase, determined from counts of daily otolith increments, were significantly different (1.3 to 1.6 x) between sites. Populations of all three species had a consistently shorter larval life at the most northern site, Cabo San Lucas (Mexico) compared to Panamá and the offshore islands of Galápagos and Cocos. Analyses of otolith increment width over the precompetent period revealed that this disparity in larval duration primarily reflected differences in larval growth rates: faster growing fish spent less time in the plankton. In T. lucasanum, some of the variation in larval duration between Panamá and offshore sites (Galápagos Islands and Cocos Island) may be accounted for by a higher frequency of individuals delaying metamorphosis at the offshore sites. These data indicate that conditions in the planktonic environment are not homogeneous throughout the tropical eastern Pacific and may have a profound effect on aspects of the larval ecology of reef fishes in this region.     

Effects on larval crabs of exposure to algal toxin via ingestion of heterotrophic prey

We tested whether ingesting toxic algae by heterotrophic prey affected their nutritional value to crab larval predators, using toxic algal strains that are either ingested directly by larval crabs or rejected by them. Ingestion of toxic strains of the dinoflagellates Alexandrium andersoni and A. fundyense by the rotifer Brachionus plicatilis was confirmed. Rotifers having ingested either algal type for five days were fed to freshly hatched larvae of three crab species, with larval survival and stage durations determined. For both algal/rotifer treatments in all three crab species, larvae fed algae directly died during the first zoeal stage, while those fed rotifers that had been fed either algal strain survived to the experiment’s end (zoeal stage 3). Survival was lower, and stage duration longer, for larvae fed rotifers cultured on toxic algae when compared to those fed non-toxic algae. The role of toxic algae in the planktonic food web may be influenced by its direct or indirect ingestion by larval crabs.     

Implications of life history for genetic structure and migration rates of southern African coastal invertebrates: planktonic,abbreviated and direct development

The amount of genetic structure in marine invertebrates is often thought to be negatively correlated with larval duration. However, larval retention may increase genetic structure in species with long-lived planktonic larvae, and rafting provides a means of dispersal for species that lack a larval dispersal phase. We compared genetic structure, demographic histories and levels of gene flow of regional lineages (in most cases defined by biogeographic region) of five southern African coastal invertebrates with three main types of larval development: (1) dispersal by long-lived planktonic larvae (mudprawn Upogebia africana and brown mussel Perna perna), (2) abbreviated larval development (crown crab Hymenosoma orbiculare) and (3) direct development (estuarine isopod Exosphaeroma hylecoetes and estuarine cumacean Iphinoe truncata). We hypothesized that H. orbiculare, having abbreviated larval development, would employ a strategy of larval retention, resulting in genetic structure comparable to that of the direct developers rather than the planktonic dispersers. However, regional population structure was significantly lower in all species with planktonic larvae, including H. orbiculare, than in the direct developers. Moreover, nested clade analysis identified demographic histories resulting from low levels of gene flow (isolation by distance and allopatric fragmentation) in the direct developers only, and migration rates were significantly higher in all three species having planktonic larvae than in the direct developers. We conclude that the amount of genetic structure within marine biogeographic regions strongly depends on the presence or absence of free-swimming larvae. Whether such larvae are primarily exported or retained, whether they have long or short larval duration, and whether or not they are capable of active dispersal seems to have little effect on connectivity among populations.     

Daily otolith increments and recruitment in two coral-reef wrasses,Thalassoma bifasciatum and Halichoeres bivittatus

Increments on the otoliths of two common coral reef fishes, the bluehead wrasse Thalassoma bifasciatum and the slippery dick Halichoeres bivittatus, were demonstrated by mark-recapture experiments to be daily. Otoliths were marked in two ways; by depriving fish of light, food, and temperature cycles and also by supplemental feeding in the field. Both experiments were performed in late 1980 in the San Blas Islands of Panamá. A mark corresponding to settlement of the planktonic larva onto the reef was found on the otoliths of the bluehead wrasse. This settlement mark was used to calculate the dates of settlement of a collection of juveniles of this species taken from a patch reef in the San Blas Islands of Panamá in 1981. Settlement occurred in short and irregular bursts. The number of daily increments before the settlement mark indicates a planktonic larval life of 40 to 72 d.     

Effects of temporary starvation on larvae of the sea star Asterina miniata

Patchy food distribution may force temporary starvation conditions on planktonic larvae. This potential food limitation may affect survivorship, duration of larval period, and post-metamorphic succes. In this study, larvae of the asteroid Asterina miniata were subjected to temporary food deprivation of several durations and at different stages. Developmental effects were documented by quantification of larval stage, total length, time to metamorphosis, initial juvenile radius, range of settling times, and percent survival to metamorphosis. All starved treatments were significantly affected in settling time and most in percent survival. However, larvae starved later in development demonstrated tremendous tolerance of food deprivation (e.g. the total number of settlers in the treatment starved for 28 d was not significantly different from the fed control). Survival was lower in treatments starved earlier in development than those starved later. Food is apparently required until late in larval development to facilitate metamorphosis. The range of settling times was large; for example, the continuously-fed control treatment produced juveniles from Days 58 through 136. Temporary starvation had no effect on initial juvenile radius.     

Variation in larval life-history traits among reef fishes across the Isthmus of Panama

We tested the hypothesis that regional differences in oceanic productivity have led to the evolution of predictable patterns of regional variation in life-history traits of pelagic larvae of tropical reef fishes. To do so we compared larval traits (egg and hatchling size, larval growth rate and duration, and size at settlement) among closely related reef fishes from the Atlantic and Pacific coasts of the Isthmus of Panama. This comparison provides a control for phylogenetic effects because those regions shared a common fauna prior to the rise of the Isthmus ˜3.5 million years ago, subsequent to which each fauna evolved independently under a very different productivity regime. We measured larval traits of 12 benthic-spawning damselfishes (Pomacentridae: Abudefduf, Chromis and Stegastes) and 13 pelagic-spawning wrasses (Labridae: Bodianus, Halichoeres and Thalassoma). These included members of each genus on each side of the Isthmus and four sets of transisthmian sister species of pomacentrids. Among the pomacentrids we found consistent transisthmian differences in hatchling size, but not in other larval traits. Essentially the reverse pattern occurred among the labrids – larval growth and duration differed consistently among congeners in the two regions, but without consistent differences in hatchling size or size at settlement. Neither relationship is predicted by the regional-productivity hypothesis. Most of the differences were quite small. Stronger phylogenetic effects on larval traits (inter- and intrageneric variation within regions) occur in both families and evidently overwhelm any effect of regional variation in productivity. Reassessment of data that takes into account such phylogenetic effects questions previous conclusions about the existence of regional differences in larval traits among damselfishes in the West Pacific and the Caribbean. Received: 19 January 2000 / Accepted: 26 September 2000     

Phylogeography, historical demography, and the role of post-settlement ecology in two Hawaiian damselfish species

Coral reef fish generally have relatively sedentary juvenile and adult phases and a presumed highly dispersive pelagic larval phase, yet previous studies that have tried to relate pelagic larval duration (PLD) to population structure have given inconsistent results. In the present study, the population structures of two damselfishes, Stegastes fasciolatus and Dascyllus albisella, were examined using mitochondrial control region sequences. The two species have similar PLDs (∼25 and 27 days respectively), but consistently differ in their settlement preferences, habitat, and densities in populations throughout the Hawaiian Archipelago, from Hawaii north to Kure Atoll, and south to Johnston Atoll. Information on habitat preferences and population densities were collected between September 2000 and October 2002, and tissue samples for the genetic studies were collected between January and April 2004. Based on the differences in habitat and abundance of the two species, the expectation was that S. fasciolatus would have high genetic variability but little population structure compared to D. albisella, and this was largely confirmed. Stegastes fasciolatus had little population structure in most of the Hawaiian Islands, and D. albisella showed evidence of strong population structure throughout its range. An exception to this pattern was the large difference between the Kure Atoll population of S. fasciolatus and all others. These results suggest that the interaction of several biological factors (e.g. species-specific spawning habitat and season) with environmental factors (e.g. seasonal wind and current patterns) may have more influence on population structure than single life history characteristics, such as the PLD.     

Larval development in the Tasmanian mysids Anisomysis mixta australis, Tenagomysis tasmaniae and Paramesopodopsis rufa (Crustacea: Mysidacea)

We describe the brood duration and marsupial development of three temperate coastal mysid species, Anisomysis mixta australis (Zimmer), Tenagomysis tasmaniae Fenton and Paramesopodopsis rufa Fenton, found commonly in Tasmanian waters. Larvae cultured in vitro had brood durations at 13 °C (17 °C) of 22 (15), 23 (15), and 28 (20) d, respectively. Development through seven larval stages, and brood durations for these three species are similar to those reported for coastal mysids from other temperate areas throughout the world. Received: 10 June 1997 / Accepted: 1 July 1997     

Small-scale spatial and temporal genetic structure of the Atlantic sea scallop (Placopecten magellanicus) in the inshore Gulf of Maine revealed using AFLPs

Despite long planktonic durations, many species of broadcast spawning invertebrates exhibit genetic structure at small spatial and temporal scales. Amplified fragment length polymorphisms were used to assess genetic variation in the sea scallop, Placopecten magellanicus, among four inshore and one offshore location in the Gulf of Maine and temporal genetic variation among age classes of sea scallops at one site. Our results indicated that genetic structure for P. magellanicus exists on smaller spatial scales (tens to hundreds of kilometers) than expected given the 40-day planktonic larval period. In addition, genetic differences among age classes may be influenced by inter-annual differences in larval supply or reproductive success. Future genetic studies should sample multiple age classes prior to comparison among locations.     

Amino acid metabolism and protein turnover in larval turbot (Scophthalmus maximus) fed natural zooplankton or Artemia

The present paper studied the influence of different food regimes on the free amino acid (FAA) pool, the rate of protein turnover, the flux of amino acids, and their relation to growth of larval turbot (Scophthalmus maximus L.) from first feeding until metamorphosis. The amino acid profile of protein was stable during the larval period although some small, but significant, differences were found. Turbot larvae had proteins which were rich in leucine and aspartate, and poor in glutamate, suggesting a high leucine requirement. The profile of the FAA pool was highly variable and quite different from the amino acid profile in protein. The proportion of essential FAA decreased with development. High contents of free tyrosine and phenylalanine were found on Day 3, while free taurine was present at high levels throughout the experimental period. Larval growth rates were positively correlated with taurine levels, suggesting a dietary dependency for taurine and/or sulphur amino acids. Reduced growth rates in Artemia-fed larvae were associated with lower levels of free methionine, indicating that this diet is deficient in methionine for turbot larvae. Leucine might also be limiting turbot growth as the different diet organisms had lower levels of this amino acid in the free pool than was found in the larval protein. A previously presented model was used to describe the flux of amino acids in growing turbot larvae. The FAA pool was found to be small and variable. It was estimated that the daily dietary amino acid intake might be up to ten times the larval FAA pool. In addition, protein synthesis and protein degradation might daily remove and return, respectively, the equivalent of up to 20 and 10 times the size of the FAA pool. In an early phase (Day 11) high growth rates were associated with a relatively low protein turnover, while at a later stage (Day 17), a much higher turnover was observed. Received: 19 March 1997 / Accepted: 14 April 1997     

Settlement patterns and post-settlement survival in two Mediterranean littoral fishes: influences of early-life traits and environmental variables

We examined the relationships between daily pattern of settlement and environmental parameters during two consecutive years in two littoral fishes, Lipophrys trigloides (Blenniidae) and Chromis chromis (Pomacentridae), in the NW Mediterranean Sea. We also used individual early-life traits (pelagic larval duration, size at hatching and size at settlement) calculated from otoliths, to study the proximate causes of settlement variability and size-selective mortality after settlement. Several early-life characteristics of L. trigloides (planktonic larval duration and size at hatching), and environmental variables averaged during the whole planktonic period (e.g. water temperature, wave height, solar radiation) were related with the magnitude of settlement. In contrast, C. chromis showed no significant relationships between early-life traits and the magnitude of settlement, and a weak relationship between settlement magnitude and environmental variables. Furthermore, juvenile survivors showed larger size at hatching than settlers, indicating that size at hatching affected the juvenile survival of the two species. These results suggest that survival was linked largely to conditions at hatching for both species.     

Laboratory study of effects of temperature and salinity on survival and larval development of a population of Rhithropanopeus harrisii from the Mondego River estuary,Portugal

Rhithropanopeus harrisii (Gould) is an introduced species in the estuary of the Mondego River (Portugal): it was first recorded from the Iberian Peninsula in 1989. The larval development of this population was studied under laboratory conditions at different temperatures and salinities, and showed a larval development pattern very similar to that reported for American estuarine populations of this species. Larval development was negatively correlated with temperature. Time to megalopa varied between 7 and 35 d; the first crab (C₁) was reached after a maximum of 11 to 43 d. Larval development was optimum at 25°C and 15S. Larval survival was maximum at 10, 15 and 20S at all three temperatures studied (20, 25 and 30°C). The percentage of abnormal megalopae increased with increasing salinity to a maximum (100%) at 30S; incidence of abnormality was not affected by temperature.     

Data on biological productivity of the Western tropical Pacific Ocean

Vertical distribution and production of phytoplankton and planktonic bacteria were studied in the pelagic and neritic regions of the Western tropical Pacific Ocean and in temperate waters of the Japan Sea. The stable, layering structure of the community and its daily fluctuations caused by grazing are described. Data on the integral daily production of communities under 1 m² are presented. The data obtained are discussed with respect to the trophical relations in planktonic communities of the stratified sea basins.     

Foraging behavior in early Atlantic cod larvae (Gadus morhua) feeding on a protozoan (Balanionsp.) and a copepod nauplius (Pseudodiaptomussp.)

Food limitation is likely to be a source of mortality for fish larvae in the first few weeks after hatching. In the laboratory, we analyzed all aspects of foraging in cod larvae (Gadus morhua Linnaeus) from 5 to 20 d post-hatching using protozoa (Balanion sp.) and copepod nauplii (Pseudodiaptomus sp.) as prey. A camera acquisition system with two orthogonal cameras and a digital image analysis program was used to observe patterns of foraging. Digitization provided three-dimensional speeds, distances, and angles for each foraging event, and determined prey and fish larval head and tail positions. Larval cod swimming speeds, perception distances, angles, and volumes increased with larval fish size. Larval cod swam in a series of short intense bursts interspersed with slower gliding sequences. In 94% of all foraging events prey items were perceived during glides. Larval cod foraging has three possible outcomes: unsuccessful attacks, aborted attacks, and successful attacks. The percentage of successful attacks increased with fish size. In all larval fish size classes, successful attacks had smaller attack distances and faster attack speeds than unsuccessful attacks. Among prey items slowly swimming protozoans were the preferred food of first-feeding cod larvae; larger larvae had higher swimming speeds and captured larger, faster copepod nauplii. Protozoans may be an important prey item for first-feeding larvae providing essential resources for growth to a size at which copepod nauplii are captured. Received: 20 April 1999 / Accepted: 12 January 2000     

Larval mesopelagic fish assemblages in the Kuroshio–Oyashio transition region of the western North Pacific

We examined larval mesopelagic fish assemblages, their distribution, and seasonal occurrence patterns in the Kuroshio–Oyashio transition region of the western North Pacific where complex hydrographic structures are observed due to the confluence of the Kuroshio Extension and Oyashio current. Larvae of the dominant families Myctophidae, Gonostomatidae, Bathylagidae, Sternoptychidae, and Phosichthyidae were represented by 31 species or types belonging to 24 genera. Based on species composition analysis using the Morishita–Horn similarity index, five assemblages were recognized: Oyashio, Spring Transition, Summer Transition, Kuroshio, and Slope Water assemblages. The distribution patterns of these assemblages corresponded closely with hydrographic structures such as position of the Oyashio and Kuroshio Extension fronts, warm core rings and streamers. Spring Transition (April) and Summer Transition (July–October) assemblages were the most important larval assemblages in the transition region. Larval abundances were low during late autumn and winter. The Spring Transition and Summer Transition assemblages were composed of subtropical, transitional, subarctic, and slope-water species, suggesting the importance of the transition region as nursery grounds of mesopelagic fishes of various origins from subarctic to subtropical waters. Larval fish transport by the Kuroshio, Oyashio, and Tsugaru Warm currents into the transition region is discussed.     

Development of the nasal olfactory organs in the larvae, settlement-stages and some adults of 14 species of Caribbean reef fishes (Labridae, Scaridae, Pomacentridae)

Larval fishes likely use a variety of settlement cues to locate and navigate toward the habitats they will inhabit as juveniles. Information about the morphology and state of development of the sensory organs of larval stages of fishes provides insight into their capabilities at the time of settlement. The peripheral olfactory organ of wild-caught late-stage larvae and early juveniles and some adults of 14 species of the Caribbean reef fishes wrasses (Labridae), parrot fishes (Scaridae) and damselfish (Pomacentridae) were examined using scanning electron microscopy and compared in terms of settlement specificity. Ages in days after hatching and days post-settlement were determined from the otoliths. Morphology of the nares and the olfactory epithelium are described for these species by stage. The separation of the anterior and posterior nares occurred before settlement in the labrids but in some specimens of scarids this separation was not complete by the time of settlement. Densities of ciliated and microvillous receptor cells and non-sensory ciliated epithelial cells were calculated. Densities of ciliated receptor cells ranged from 0.389 μm⁻² in a specimen of Thallasoma bifasciatum to 0.0057 μm⁻² in Bodianus rufus and of microvillous receptor cells from 0.038 μm⁻² in a Clepticus parrae juvenile to 0.266 μm⁻² in a juvenile Doratonotus megalepis. Densities of non-sensory cilia, also associated with high olfactory ability, were also high. The olfactory organ in wrasses is well developed prior to settlement and is comparable to that of adult fishes. The possible role of olfaction in larval schooling, reef cue detection and orientation toward habitat at settlement is discussed.

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Latitudinal variability in spatial genetic structure in the invasive ascidian, Styela plicata

Increases in temperature can shorten planktonic larval durations, so that higher temperatures may reduce dispersal distances for many marine animals. To test this prediction, we first quantified how minimum time to settlement is shortened at higher temperatures for the ascidian Styela plicata. Second, using latitude as a correlate for ocean temperature and spatial genetic structure as a proxy for dispersal, we tested for a negative correlation between latitude and spatial genetic structure within populations, as measured by anonymous DNA markers. Spatial genetic structure was variable among latitudes, with significant structure at low and intermediate latitudes (high and medium temperatures) and there was no genetic structure within high-latitude (low temperature) populations. In addition, we found consistently high genetic diversity across all Australian populations, showing no evidence for recent local bottlenecks associated S. plicata’s history as an invasive species. There was, however, significant genetic differentiation between all populations indicating limited ongoing gene flow.