New insights into patterns of coral spawning on Western Australian reefs

On reefs around Australia, coral mass spawning typically occurs during the austral spring (October/November) on the east coast, and during autumn (March/April) on the west coast. However, to investigate the incidence of a secondary spawning event in spring on the west coast, the reproductive state of corals was assessed on two reefs. The results indicated that of the 29 species of Acropora investigated, multiple colonies of 11 species spawned in late spring or in early summer, in contrast to previous reports of spawning during autumn. Additionally, of four species that were followed through time at one reef, two spawned in both spring and autumn, however, individual colonies had only one gametogenic cycle. Within a single site, conspecific colonies were reproductively isolated and may not interbreed, potentially representing the initial stage of sympatric speciation in these populations.     

Sexual reproduction of Acropora reef corals at Moorea, French Polynesia

Little information is available on reproductive processes among corals in isolated central Pacific reef regions, including French Polynesia. This study examined the timing and mode of sexual reproduction for Acropora reef corals at Moorea. Spawning was observed and/or inferred in 110 Acropora colonies, representing 12 species, following full moon periods in September through November 2002. Gamete release was observed and inferred in four species of Acropora between 9 and 13 nights after the full moon (nAFM) in September 2002. Twelve Acropora spp. spawned gametes between 5 and 10 nAFM in October 2002, with six species spawning 7 nAFM and four species spawning 9 nAFM. In November 2002, spawning of egg and sperm bundles was observed and inferred in 27 colonies of Acropora austera, 6 nAFM. These are the first detailed records of spawning by Acropora corals in French Polynesia.     

Biannual coral spawning decreases at higher latitudes on Western Australian reefs

Seasonal differences in the timing of multi-specific coral spawning between the east and west coasts of Australia may be the result of a genetic legacy or of adaptation to local conditions. Using estimates of the proportions of coral species that spawned in spring and autumn at Ashmore Reef (12°S) and Ningaloo Reef (23°S) in Western Australia, in combination with findings of previous surveys, I examined whether reproductive seasonality varied with latitude. A consistently high proportion of species spawned during the main reproductive season in autumn regardless of latitude. However, there was a clear decrease in the proportion of species spawning in spring, from an average of 49 % at Ashmore Reef (12°S) to 7 % at Ningaloo Reef (23°S). The results of this study suggest that seasonality of coral reproduction in Western Australia reflects environmental gradients and natural selection rather than an inherited genetic legacy.     

Asynchronous spawning in sympatric populations of a hard coral reveals cryptic species and ancient genetic lineages

Genetic subdivision within a species is a vital component of the evolution of biodiversity. In some species of Acropora corals in Western Australia, conspecific individuals spawn in two seasons 6 months apart, which has the potential to impede gene flow and result in genetic divergence. Genetic comparison of sympatric spring and autumn spawners of Acropora samoensis was conducted to assess the level of reproductive isolation and genetic divergence between the spawning groups based on multiple loci (13 microsatellite loci, the mitochondrial control region and two nuclear introns). Bayesian clustering and principal coordinate analysis of the microsatellite loci showed a high level of genetic differentiation between the spawning groups (F’_ST = 0.30; P < 0.001), as did the sequence data from PaxC and Calmodulin (Φ_ST = 0.97 and 0.31, respectively). At the PaxC locus, the autumn and spring spawners were associated with two divergent lineages that were separated by an evolutionary distance of 1.7% and statistical tests indicate divergent selection in PaxC, suggesting this gene may play a role in coral spawning. This study indicates that the autumn and spring spawners represent two cryptic species, and highlights the importance of asynchronous spawning as a mechanism influencing speciation in corals.     

Assessment of reproductive potential in multiple-spawning fish with indeterminate fecundity: a case study of yellow sea bream Dentex hypselosomus in the East China Sea

This study examined the spawning season, spawning frequency and batch fecundity of yellow sea bream Dentex hypselosomus in the East China Sea to reassess the previously reported reproductive characteristics of the species. Time-course sampling showed that this species had a diurnal ovarian maturation rhythm. Late tertiary yolk-stage oocytes appeared 2 days before spawning, starting the process of germinal vesicle movement and breakdown. On the day of spawning, ovulation and subsequent spawning occurred in the early morning (0400–0800 hours). Postovulatory follicles disappeared from the ovaries within c. 24 h of ovulation. Seasonal changes in the ovarian conditions indicated that this species spawned more or less throughout the year, with the peak ranging from spring to autumn. The compositions of the developing oocytes and degenerating postovulatory follicles in the ovaries suggested that most females spawned repeatedly over 2 to 3 consecutive days during the peak of the spawning season. Somatic body condition did not have a significant effect on batch fecundity, but there was a significant relationship between batch fecundity and fork length according to spawning status. Females spawning on consecutive days were more fecund than those spawning every other day. The findings show that this species has much greater reproductive potential than previously estimated.     

Effect of seawater temperature on reproductive seasonality and fecundity of Pseudoplexaura porosa (Cnidaria: Octocorallia): latitudinal variation in Caribbean gorgonian reproduction

Abstract. The majority of tagged colonies of Pseudoplexaura porosa in Bermuda were reproductive over 2 months in the summer. They spawned 5–8 d after the full moon, with a peak on the sixth day, similar to colonies in Panama. The months of spawning were August and September in 1998, but July and August in 1999 and 2000. This temporal difference between the months of spawning corresponded to inter-annual variations in seawater temperature profiles. Initial gamete development each year occurred only when the daily mean seawater temperature during the month before spawning exceeded 27°C. There was a significant positive relationship between reproductive effort (gamete volume) of colonies and rising seawater temperature in the month preceding spawning; this was true for both the initial and the second spawning months. The end of the reproductive season each year was triggered by the decline in seawater temperature past the summer maximum. The duration of the reproductive season of conspecifics at the central Caribbean reef of Panama is 2 months longer than in Bermuda. This can be explained by the smaller annual temperature range at the lower latitude and the earlier onset of temperatures favorable for gamete development. Fecundity estimates for members of P. porosa (mean oocyte and spermary densities) in Bermuda were lower than for conspecifics in Panama. The shorter reproductive season in Bermuda, in addition to the lower fecundity of colonies, indicates that reproduction in P. porosa is compromised at this high latitude reef.     

Coral mass- and split-spawning at a coastal and an offshore Venezuelan reefs,southern Caribbean

This study aimed to evaluate potential differences in coral spawning behavior between a fringing coastal reef and an offshore reef in the southern Caribbean. For this, scleractinian and gorgonian colonies (N = 324) of 21 species were mapped along eight transects, each 10-m long, at two study sites located in Morrocoy and Los Roques National Parks, Venezuela. Observations were made between 19:30 and 23:00 from August 23 to 30 and from September 26 to 30, 2002. Ninety one colonies belonging to six hard coral and seven octocoral species spawned or planulated during this period. We were unable to observe any signs of reproductive activity in 95 colonies of nine species different from those that reproduced. Despite the differences in environmental conditions between the two sites, we observed high synchrony in the spawning behavior of seven coral species common to both reefs. The most striking result was the ability of colonies of Montastraea faveolata and Eusmilia fastigiata to split spawn up to three times, either in consecutive nights or in different months.     

Transplantation and cultivation of fragments of coral colonies of various scleractinian species on a reef in Vietnam

Six coral species of the genus Acropora and two species of the genus Porites were studied during experiments on cultivation of reef-building scleractinian corals. The research has established species-specific factors and others affecting regeneration of fragments and growth of new colonies in these coral species. The accretion of donor fragments and new branches averaged from 40 to 160 mm per year, depending on the coral species, colony size, and season of transplantation. An average monthly accretion of medium and larger transplants and growth of new branches were 1.2–1.3 times higher at spring cultivation than at autumn transplanting. When transplanted, coral fragments of medium and larger sizes survived well and showed higher growth rates in all species studied. These transplants developed the highest number of new branches, and their buds and formed the largest colonies. Prolongation of the cultivation time from 1 to 1.5 years caused a 1.2–1.4 fold accretion of transplants.     

Aspects of the spawning of western Atlantic butterflyfishes (Pisces: Chaetodontidae)

Synopsis The status of knowledge of spawning among the five shallow waterChaetodon species in the western Atlantic is reviewed. Spawning has been observed for three species in Puerto Rico, St. Croix and the Bahamas, with possible courtship in a fourth.Chaetodon aculeatus spawned near the time of sunset over objects on the reef as single female/male pairs or as two females and one male, with pair spawning in rapid succession. Spawning occurred during much of the lunar month from February to April and it is uncertain whether any lunar periodicity to spawning exists. Male-male aggression was noted. Spawning sites (coral heads) were alternated daily and it is likely that females spawn only once every two days. A single female produced as many as 2090 eggs in a single spawning.Chaetodon capistratus spawned during much of the lunar month from February to April. It spawned about 5 min afterC. aculeatus, occasionally using the same sites, and alternated sites daily. A female produced as many as 3710 eggs in one spawning.Chaetodon striatus spawned from February to April but it is unknown if it has any lunar spawning cycle. No predation attempts by piscivores on spawning adults were seen. Predation byMelichthys niger on eggs ofC. striatus occurred. No egg predation was observed forC. aculeatus andC. capistratus. With an assumed four month reproductive season, alternate day spawning and observed egg production values,C. aculeatus andC. capistratus produce respectively about 100 000 and 200 000 eggs per large female per year. The reproductive strategy of smaller species may be to produce moderate numbers of eggs per day over a spawning season of at least a few months while larger species may produce more eggs per day for a shorter period.     

Sexual reproduction in Hawaiian Acropora

Sexual reproductive maturity was evaluated in Acropora valida, Acropora cytherea and Acropora humilis at French Frigate Shoals, Northwest Hawaiian Islands during two consecutive summers. Acropora valida gonads matured at different rates in different habitats in both years. Spawning was inferred by the sudden disappearance of gonads of mature size. Histological sections of fertile polyps confirmed the maturity of gonads prior to spawning. An isolated colony of A. humilis spawned in early summer. Strong indications of sexually mature colonics of A. cytherea exist, but clear temporal patterns were not apparent. Lunar period of spawning in reef flat A. valida and A. humilis differed from that reported for these species from other regions. The three species did not overlap in time of spawning. Previous ideas concerning the allochthonous origin of larval recruits, as well as the absence of Acropora from high islands of the Hawaiian chain, are re-evaluated in light of new evidence for sexual reproductive capacity by native populations.     

MORE THAN BINDIN DIVERGENCE: REPRODUCTIVE ISOLATION BETWEEN SYMPATRIC SUBSPECIES OF A SEA URCHIN BY ASYNCHRONOUS SPAWNING

The evolution of reproductive barriers is crucial to the process of speciation. In the Echinoidea, studies have focused on divergence in the gamete recognition protein, bindin, as the primary isolating mechanism among species. As such, the capacity of alternate mechanisms to be effective reproductive barriers and the phylogenetic context in which they arise is unclear. Here, we examine the evolutionary histories and factors limiting gene exchange between two subspecies of Heliocidaris erythrogramma that occur sympatrically in Western Australia. We found low, but significant differentiation between the subspecies in two mitochondrial genes. Further, coalescent analyses suggest that they diverged in isolation on the east and west coasts of Australia, with a subsequent range expansion of H. e. erythrogramma into Western Australia. Differentiation in bindin was minimal, indicating gamete incompatibility is an unlikely reproductive barrier. We did, however, detect strong asynchrony in spawning seasons; H. e. erythrogramma spawned over summer whereas H. e. armigera spawned in autumn. Taken together, we provide compelling evidence for a recent divergence of these subspecies and their reproductive isolation without gamete incompatibility. Western Australian H. erythrogramma may therefore present an intriguing case of incipient speciation, which depends on long‐term persistence of the factors underlying this spawning asynchrony.     

Spawning of coral reef invertebrates and a second spawning season for scleractinian corals in the central Red Sea

Recent coral spawning observations in the central Red Sea show that most scleractinian species release their gametes in the spring, with a majority of species spawning in April. There is, however, a lack of reproductive data for several other coral species, as well as a general lack of data for other invertebrates. Here, we document the detailed timing of spawning for 13 scleractinian coral species, one sea anemone, and six echinoderms from an inshore reef off the coast of Thuwal, Saudi Arabia, in the spring between April and June 2014. Furthermore, inferred from the presence of mature gametes, we report the month of spawning for three additional coral species in the spring. Seven scleractinian coral species were inferred to release their gametes in a second reproductive season, in the autumn, between September and November. This is the first report of a second spawning season in the Arabian region. Biannual spawning has so far been reported on the Great Barrier Reef, in Western Australia, in Indonesia, in Malaysia, in Palau, in Thailand, in Taiwan, and in Western Samoa.     

Outlier Loci Detect Intraspecific Biodiversity amongst Spring and Autumn Spawning Herring across Local Scales

Herring, Clupea harengus, is one of the ecologically and commercially most important species in European northern seas, where two distinct ecotypes have been described based on spawning time; spring and autumn. To date, it is unknown if these spring and autumn spawning herring constitute genetically distinct units. We assessed levels of genetic divergence between spring and autumn spawning herring in the Baltic Sea using two types of DNA markers, microsatellites and Single Nucleotide Polymorphisms, and compared the results with data for autumn spawning North Sea herring. Temporally replicated analyses reveal clear genetic differences between ecotypes and hence support reproductive isolation. Loci showing non-neutral behaviour, so-called outlier loci, show convergence between autumn spawning herring from demographically disjoint populations, potentially reflecting selective processes associated with autumn spawning ecotypes. The abundance and exploitation of the two ecotypes have varied strongly over space and time in the Baltic Sea, where autumn spawners have faced strong depression for decades. The results therefore have practical implications by highlighting the need for specific management of these co-occurring ecotypes to meet requirements for sustainable exploitation and ensure optimal livelihood for coastal communities.     

Synchronous reproduction of corals in the Red Sea

Multi-species synchronous spawning was first described on reefs off the east and west coast of Australia. In contrast, locally abundant species in the northern Red Sea and the central Pacific have little overlap in the time of reproduction. Consequently, the idea developed that high levels of spawning synchrony both within and among species was largely confined to Australian reefs. Here, we show that gamete maturity in colonies of the genus Acropora was highly synchronous in the Red Sea. In early April 2008, at two locations separated by 300 km, 13 of 24 species sampled had mature colonies, and a further 9 species had immature colonies. In late April–early May 2008, all colonies sampled had no oocytes, indicating colonies had spawned a few days after the full moon of 20 April 2008. Similarly, in 2009, 99% of colonies from 17 species at Hurghada were mature in late April, and all were empty in early May. Spawn slicks suggested many of these colonies had released gametes three night prior to the full moon on 8 May 2009. This level of synchrony in gamete maturity is among the highest ever recorded and similar to that typically recorded in Acropora assemblages on Australian reefs. While further work is required to document the night of gamete release, these data strongly suggest that high levels of spawning synchrony are a regular feature of these Red Sea coral assemblages and that multi-species spawning occurs on or around the full moon in April and/or May.     

Relationship between hatch date and first-summer growth of five species of prairie-stream cyprinids

Stream fishes often exhibit a bet-hedging multiple spawning reproductive strategy. In many species, the reproductive season lasts several months. This exposes young fishes to varying environmental conditions that may differentially affect growth. We studied the effect of hatch date on first-summer growth among members of a prairie-stream fish assemblage. The reproductive season in both years of the study was protracted, lasting from April through August. Due to intermittent stream-discharge, there were two distinct periods during which most species successfully reproduced. In general, growth rate was greater among individuals with an early hatch date than among those with a later hatch date. Multiple regression models indicated that hatch date was related to growth in all study species with one exception (red shiner, Cyprinella lutrensis). The results of this study provide evidence that young-of-the-year of multiple spawning stream-fish species that are spawned late in the season may grow at a slower rate than young spawned earlier in the season.     

Reproductive cycles in littoral populations of Choromytilus meridionalis (Kr.) and Aulacomya ater (Molina) with a quantitative assessment of gamete production in the former

Changes in ovary weight and ovary smears of Choromytilus meridionalis (Kr.) and Aulacomya ater (Molina) showed the breeding season to extend throughout the spring and summer months (Aug.-Feb.). Release of gametes was intermittent with regeneration of the gonad after peak spawning periods. Populations spawned synchronously or asynchronously with an average of 50% of individuals spawning at any one time. The end of the breeding season was marked by gonad depletion and resorption of gametes. Gametogenesis followed rapidly and large quantities of reserve material were not deposited in the mantle during the winter months as in Mytilus edulis.The False Bay population of Choromytilus meridionalis has predominantly synchronous spawning and gamete production for two breeding seasons was calculated. The quantity of gametes released varied annually and was not significantly different in males and females. Mean gamete production was calculated as 1.17 × standing crop expressed as dry flesh weight, or 1.33 × energy value of the standing crop per annum.     

Gametogenesis and fecundity of <Emphasis Type="Italic">Acropora tenella</Emphasis> (Brook 1892) in a mesophotic coral ecosystem in Okinawa,Japan

Mesophotic coral ecosystems (below 30–40 m depth) host a large diversity of zooxanthellate coral communities and may play an important role in the ecology and conservation of coral reefs. Investigating the reproductive biology of mesophotic corals is important to understand their life history traits. Despite an increase in research on mesophotic corals in the last decade, their reproductive biology is still poorly understood. Here, gametogenesis and fecundity of the Indo-Pacific mesophotic coral, Acropora tenella, were examined in an upper mesophotic reef (40 m depth) in Okinawa, Japan for the first time. Acropora tenella is a hermaphrodite with a single annual gametogenic cycle, and both oogenesis and spermatogenesis occurring for 11–12 and 5–6 months, respectively. Timing of spawning of this species was similar to other shallow Acropora spp. in the region. However, colonies had longer gametogenic cycles and less synchronous gamete maturation compared to shallow acroporids with spawning extended over consecutive months. Both the polyp fecundity (number of eggs per polyp) and gonad index (defined as the number of eggs per square centimeter) of A. tenella were lower than most acroporids. Our findings contribute to understanding of the life history of corals on mesophotic reefs and suggest that the reproductive biology of upper mesophotic corals is similar to that of shallow-water corals.     

The aftermath of coral bleaching on a Maldivian reef—a quantitative study

Since the bleaching event of 1998, the development of the reef flat and upper reef slope on a Maldivian reef (the Komandoo house reef; Komandoo Island, Lhaviyani atoll or Fadiffolu atoll) is under detailed observation. We quantitatively recorded specific losses, re-colonisation by coral larvae on transects on the reef flat and on dead Acropora tables at the reef slope and regeneration of partly damaged large Porites and Diploastrea—colonies over the period from 1999 to 2004. The detrimental effects on the reef structure by bioerosion and hydrodynamics, as well as the overall status of the reef community were qualitatively assessed. Recruitment soon after the bleaching was more pronounced than in the following years, Pavona varians being a main constituent. The temporal re-colonisation pattern points at an emergency spawning of local Scleractinia just prior to the bleaching, whereas a sharp decrease of young settlers in 2001 and 2002 confirms a reduction of fertile colonies. The dominant species in the coral community shifted from acroporids and pocilloporids to agariciids. The skeletal deposition of recovering Diploastrea heliopora was equivalent to that before the bleaching, but much less than that of neighbouring Porites lobata colonies. The slow and scattered formation of new reef substance, which would structurally strengthen the reef, is however outweighed by the collapse of dead protruding and spacious colonies (e.g., Acropora tables). Six years after the bleaching, the formerly three-dimensional structure of the reef flat and upper reef slope presents as a levelled field of rubble, only partly consolidated by incrusting corals. Considering the recurrence of bleaching events (1987, 1998) and the results of the present study, one may assume a cascading deterioration of the status of the reef for the future.     

Duration of larval and spawning periods inPagrus auratus (Sparidae) determined from otolith daily increments

Synopsis Counts of pre-metamorphic and post-metamorphic daily increments in the sagittae of settled juvenilePagrus auratus were used to determine duration of the larval period and to back-calculate spawning dates. The duration of the larval period was 18–32 days, and was longer for snapper spawned early in the spawning season, when water temperatures were low, than for snapper spawned later in the season when temperatures were high. Sagitta size at metamorphosis was unrelated to duration of the larval period or temperature, and mean increment width during the larval period increased with temperature. These results suggest that metamorphosis is size- rather than age-dependent. Back-calculated spawning dates ranged from September to March, and peaked in November-January. Maximum spawning season duration was five months. Spawning onset was earlier when spring water temperature was higher than normal, and first spawning occurred at 14.8–15.6 °C over three seasons, indicating that spawning onset is temperature-dependent.     

Congruent patterns of connectivity can inform management for broadcast spawning corals on the Great Barrier Reef

Connectivity underpins the persistence and recovery of marine ecosystems. The Great Barrier Reef (GBR) is the world's largest coral reef ecosystem and managed by an extensive network of no‐take zones; however, information about connectivity was not available to optimize the network's configuration. We use multivariate analyses, Bayesian clustering algorithms and assignment tests of the largest population genetic data set for any organism on the GBR to date (Acropora tenuis, >2500 colonies; >50 reefs, genotyped for ten microsatellite loci) to demonstrate highly congruent patterns of connectivity between this common broadcast spawning reef‐building coral and its congener Acropora millepora (~950 colonies; 20 reefs, genotyped for 12 microsatellite loci). For both species, there is a genetic divide at around 19°S latitude, most probably reflecting allopatric differentiation during the Pleistocene. GBR reefs north of 19°S are essentially panmictic whereas southern reefs are genetically distinct with higher levels of genetic diversity and population structure, most notably genetic subdivision between inshore and offshore reefs south of 19°S. These broadly congruent patterns of higher genetic diversities found on southern GBR reefs most likely represent the accumulation of alleles via the southward flowing East Australia Current. In addition, signatures of genetic admixture between the Coral Sea and outer‐shelf reefs in the northern, central and southern GBR provide evidence of recent gene flow. Our connectivity results are consistent with predictions from recently published larval dispersal models for broadcast spawning corals on the GBR, thereby providing robust connectivity information about the dominant reef‐building genus Acropora for coral reef managers.