Sexual reproduction of the reef coral Montastreacavernosa (Scleractinia: Faviidae) in the Santa Marta area, Caribbean coast of Colombia

Sexual reproduction of the reef-building coral Montastreacavernosa was studied in the Santa Marta area, Caribbean coast of Colombia, from October 1990 to October 1991. The area is subjected to a seasonal upwelling–outwelling regime. From microscopical analysis of tissue sections sampled each lunar month around the full moon, it was confirmed that this is a gonochoric, broadcasting species, with a single gametogenic cycle per year, and a 1:1 sex ratio. Oogenesis began a few weeks after spawning, and extended for 11 mo. The onset of spermatogenesis occurred just before the full moon of June, later than at other localities where sea-water temperatures during the first half of the year are not as low. The amount of reproductive tissue strongly increased in both sexes after July, in association with an increase in sea-water temperature and a decrease in photoperiod. The gonad index of fully mature female colonies was about four times lower than at other localities, perhaps due to the stressful seasonal regime. The male gonad index was lower than that of the female, indicating sex-related differences in the rates of biomass allocation to reproduction. As in other Caribbean localities, spawning occurred after the full moons of August and September. However, there was some evidence of a third spawning episode after the full moon of October, possibly associated with a delay in the occurrence of maximum sea-water temperatures in near-equatorial localities compared to higher latitudes. The probability of cross-fertilization in this species with a gonochoric breeding system and a broadcasting mode of reproduction is favored by its balanced sex ratio, its usually high within-reef zone abundance, and by localized and repeated spawning episodes, synchronized by lunar phase. Received: 19 April 1996 / Accepted: 24 September 1996     

Size-dependent reproduction in the Caribbean gorgonian Pseudoplexaura porosa

Reproductive success among clonal taxa is often portrayed as a simple function of clone size, but reproduction in Pseudoplexaura porosa (Houtuyn), a common Caribbean gorgonian, reflects a more complex relationship between size and gamete production. Tagged colonies were sampled at two reefs in the San Blas Islands, Panama during the 1995 spawning season to determine the colony size at first reproduction, size-dependent polyp fecundities, and whole colony gonad production, and to follow the gametogenic cycle. Additional data were obtained during non-spawning months in 1984 and 1985. Of 120 colonies ranging in height from 20 to 250 cm, only colonies taller than 50 cm were reproductive. An average of 4.33 oocytes polyp⁻¹, 560 to 800 μm in diameter, were released during monthly synchronous spawning events from June to September. Oocytes released each month developed from a group of intermediate size oocytes present at the end of the preceding month. Almost all oocytes >560 μm were released during each spawning event. Spermatogenesis was a shorter process than oogenesis. During each spawning month, mature spermaries developed from a group of <125 μm spermaries. Virtually all spermaries >190 μm were released each month, and most of the spermary volume in mature male polyps was generated anew each month of spawning. Among reproductive colonies, polyp fecundity increased with colony height from 50 to 200 cm. Per capita fecundity of >200 cm tall female colonies was lower than for 150 to 200 cm colonies, but whole colony fecundity of large colonies was greater due to the exponential increase in the number of polyps that occurs with increasing colony height. In male colonies, both polyp and colony reproductive output increased with colony height. The large amounts of sperm produced by large male colonies probably contributes to the high rates of in situ fertilization observed in P. porosa. Differences in fecundity as a function of colony size and sex suggest differences in some combination of the cost of reproduction and/or allocation of resources to reproduction. Received: 9 September 1998 / Accepted: 7 June 1999     

Predators selectively graze reproductive structures in a clonal marine organism

Although the fitness consequences of herbivory on terrestrial plants have been extensively studied, considerably less is known about how partial predation impacts the fitness of clonal marine organisms. The trophic role of Caribbean parrotfish on coral reefs is complex: while these fish are important herbivores, as corallivores (consumers of live coral tissue), they selectively graze specific species and colonies of reef-building corals. Though the benefits of parrotfish herbivory for reef resilience and conservation are well documented, the negative consequences of parrotfish grazing for coral reproductive fitness have not been previously determined. We examined recently grazed colonies of Montastraea annularis corals to determine whether grazing was positively associated with coral reproductive effort. We measured gonad number, egg number and size, and proportional reproductive allocation for grazed and intact coral colonies 2–5 days prior to their annual spawning time. We found that parrotfish selectively grazed coral polyps with high total reproductive effort (number of gonads), providing the first evidence that parrotfish selectively target specific tissue areas within a single coral colony. The removal of polyps with high reproductive effort has direct adverse affects on coral fitness, with additional indirect implications for colony growth and survival. We conclude that chronic grazing by parrotfishes has negative fitness consequences for reef-building corals, and by extension, reef ecosystems.     

Nitrate uptake by the reef coral Diploria strigosa: effects of concentration, water flow, and irradiance

The effects of several environmental variables on net nitrate uptake by the scleractinian coral Diploria strigosa were investigated under controlled flow conditions. D. strigosa exhibited nitrate uptake rates ranging from 1 to 5 nmol cm⁻² h⁻¹ at ambient concentrations of 0.1–0.3 μM that are typical of oligotrophic reefs such as Bermuda. Net uptake ceased at approximately 0.045 μM. The uptake was positively correlated with concentration up to a saturation concentration of approximately 3 μM. The uptake was also positively correlated with water velocity at 1 μM, but not at 6 μM, suggesting diffusional limitation at low concentrations and kinetic limitation at higher concentrations. Nitrate uptake by D. strigosa was not affected by light intensity or time of day, but was almost completely inhibited by 48 h exposure to ammonium levels found on many reefs.     

Reef coral reproduction in the Abrolhos Reef Complex, Brazil: the endemic genus Mussismilia

The current contribution deals with the reproductive biology of a genus endemic to Brazil –Mussismilia Ortmann, 1890 – including all three species of the genus: M. braziliensis (Verrill, 1868), M. hartti (Verrill, 1868), and M. hispida (Verrill, 1902), which occur sympatrically in the studied area, the Abrolhos Reef Complex, Brazil. Sexuality patterns, modes of reproduction, synchrony and spawning periods are reported, and were determined by histological examination of material. All three species started to develop female and male gametes over different periods in the same breeding season. The three species are probably broadcast spawners, since no embryos or planulae were observed in any species at any given time of the year. Each reproductive cycle lasted approximately 11 months. Oogenesis and spermatogenesis started in different periods, with spermaries appearing in approximately the eighth month of ovary development and lasting about 3 months. Reproductive cycles were annual. Spawning probably occurred in consecutive months in each species. In M. braziliensis, spawning presumably happened between March and the middle of May in 1996 and 1997. Evidence suggested that spawning events of M. hispida took place between the end of April and mid-June. M. hartti may have spawned between September and November. The data presented here suggested that all studied species have at least one exclusive spawning period, asynchronically with the others. A possible exception may be the simultaneous (or close) spawnings of M. braziliensis and M. hispida in May. It is suggested that asynchrony in spawning periods among species may reduce the chance of hybridization, gamete waste and the competition for settlement surfaces. The occurrence of extended spawning periods for each species may also reduce the risks of reproductive failure, due to temporary adverse conditions. Received: 8 December 1998 / Accepted: 15 July 1999     

Sexual reproduction and external brooding by the Caribbean gorgonianBriareum asbestinum

The reproductive biology of the gonochoricBriareum asbestinum (Pallas), a common Caribbean gorgonian, was studied in the San Blas Islands (Panama), La Paguera (Puerto Rico) and the Bahamas. Of 721 colonies examined at the height of the reproductive season, during the summers of 1985 to 1988, all were either male or female. No hermaphroditic colonies or polyps were observed. The sexratio of Panama populations was significantly biased in favor of males (2.1:1,n=454) over all four years of the study. A significant male bias was also found in populations sampled in Puerto Rico (2.3:1,n=143) and in the Bahamas (2.5:1,n=124). The consistency of this geographically widespread skewed sex-ratio is unique among octocorals and scleractinians. Ooyctes appear annually in September and reach maximum diameter (600 to 900µm) in June and July of the following year. The 3 to 5 mo developmental cycle of spermaries is shorter than that of females and begins in March. Spawning in males is synchronous and occurs following the full moons of June and July. Fertilization is internal. Embryos are released from polyps very early in development, often whilst still in the process of cleaving. Embryos remain attached to the outside of the colony for 3 to 5 d, many becoming entrapped in mucous sheets secreted by the colonies. Larvae are negatively buoyant and settle rapidly once displaced from the colony. Males become reproductive at smaller branch sizes than females. Reproductive effort (gonads polyp^–1 and total gonad volume polyp^–1) for both males and females increased with increasing branch size and in polyps away from the tip and base of the branch.Please address all correspondence and requests for reprints to Dr Brazeau at his present address: Department of Biology, University of Houston, Houston, Texas 77204-5513, USA     

Sexual reproduction of the solitary sunset cup coral Leptopsammia pruvoti (Scleractinia, Dendrophylliidae) in the Mediterranean. 2. Quantitative aspects of the annual reproductive cycle

There are few data on the reproductive biology of coral species living in temperate zones, particularly in the Mediterranean Sea. Leptopsammia pruvoti is a solitary coral that is commonly found in sea caves and under overhangs throughout the Mediterranean basin and along European coasts from Portugal to southern England. In this paper, we describe its annual reproductive cycle in the eastern Ligurian Sea near the city of Leghorn (Tuscany, Italy). Polyps were sexually mature at 3 mm in length (maximum diameter of the oral disc), were dioecious with a sex ratio of 1:1, and brooded their larvae. The maturation of spermaries took 12 months and oocytes 24 months. The rate of gonad development increased significantly from November to January, fertilization occurred from January to April and planulation during May and June. Seasonal variations in water temperature and photoperiod may have played an important role in regulating reproductive events. The amount of energy devoted to male gametogenesis (quantified by gonad index) was significantly higher in the sex separated species L. pruvoti than in the hermaphroditic dendrophylliid Balanophyllia europaea, whose reproduction has been studied in a previous work. We hypothesize that this difference is due to the contrasting sexuality or fertilization biology of these two species (cross-fertilization in the sex separated L. pruvoti versus possibly self-fertilization in the hermaphroditic B. europaea). Greater male sexual allocation in reproductive strategies characterized by dioecism or cross-fertilization when compared to those characterized by hermaphroditism or self-fertilization is common in plant mating systems. In relation to other solitary dendrophylliids, L. pruvoti presents an ‘r’-reproductive strategy.     

Reproduction patterns of four Antarctic octocorals in the Weddell Sea: an inter-specific,shape, and latitudinal comparison

The reproductive patterns of four Antarctic gorgonian species have been investigated. Two of them, Dasystenella acanthina and Thouarella sp., present the bottle-brush-shape type; the other two, Fannyella rossii and Fannyella spinosa, are fan-shaped. Two different reproductive patterns have been observed in D. acanthina and Thouarella sp., which point to two size classes in the frequency distribution of oocytes. This feature indicates a reproduction cycle with overlapping generations, being each of them of more than one year, probably with seasonal spawning. F. rossii and F. spinosa show only one size class of oocytes, which could point towards an annual reproductive cycle. The presence of larvae in the gastrovascular cavities in both Fanyella species and Thoaurella sp. is a sign of a possible larvae release during austral summer. The number of oocytes per polyp ranges from 1.1 ± 0.10 SE to 1.5 ± 0.06 SE, and the size ranges from 50 to 1200 μm. The number of spermatic cysts ranges from 2.6 ± 0.19 SE to 5.0 ± 0.21SE, and their sizes range from 50 to 800 μm. These values are comparable to the reproductive trends and features found in gorgonians from other latitudes, which correspond in some cases with similar morphotypes. These coincident strategies could be related to morphological similarities rather than with latitude or water temperature. The results of this study indicate that octocoral morphology may play a crucial role in determining the reproductive output of these organisms.     

Distribution pattern, reproductive traits, and molecular analysis of two coexisting vermetid gastropods of the genus Petaloconchus: a Caribbean endemic and a potential invasive species

Vermetid gastropods are characterized by complex taxonomy and unusual ecology. A survey of the fouling community in the intake channel at the Planta Centro Power Plan in Puerto Cabello, Venezuela, found massive colonies of vermetid gastropods of the genus Petaloconchus. We arbitrarily named two prevalent varieties as black and brown-orange morphs, distinguishing based on the color of their soft bodies. Spatial distribution was different for the morphs. The black morph was present along the jetty, with higher average densities in the shallower intertidal area (410 vs. 143 ind m⁻²), while the brown-orange morph was only present at the initial part of the channel (μ = 83 ind m⁻²). Both produced small eggs (142 vs. 180 μm diameter on average), with the orange-brown eggs being slightly larger, but the morphs differed in other reproductive aspects. The brown-orange morph produced significantly fewer capsules (up to nine simultaneously per female) with fewer embryos (average of 27 viable embryos/capsule) that hatched at a larger size (577 μm on average), allocating about 17.64% of the initial egg production to nurse eggs. In contrast, the black morph produced up to 14 capsules simultaneously, hatched an average of 178 veligers of 212 μm, and produced no nurse eggs. The intra-capsular development reached a more advanced stage in the brown-orange morph than in the black one. Several cytochrome subunit I (COI) and 16S rRNA (16S) haplotypes were found for the black morph, when compared to only one haplotype for both genes present for the brown-orange morph. Preliminary phylogenetic analyses separated the morphs into different clades, supported by robust bootstrap values and posterior probabilities (>98). Our results indicate that the morphs are two different species: the black morph was identified as Petaloconchus cf. varians and the brown-orange morph as a non-described species, Petaloconchus sp. (orange). The first is endemic to the Caribbean, while the second is potentially an introduced species.     

Reproductive ecology of the azooxanthellate coral <Emphasis Type="Italic">Tubastraea coccinea</Emphasis> in the Equatorial Eastern Pacific: Part V. Dendrophylliidae

The reproductive ecology of Tubastraea coccinea Lesson, an azooxanthellate tropical scleractinian coral, was studied over various periods from 1985 to 2006 at four principal eastern Pacific locations in Costa Rica, Panamá, and the Galápagos Islands (Ecuador). This small (polyp diameter 0.8–1.0 cm), relatively cryptic species produced ova and planulae year round, including colonies with as few as 2–10 polyps. Of 424 colonies examined histologically, 13.7% contained both ova and sperm. Mature ova varied in diameter from ∼300 to 800 μm and the time from spawning and fertilization of oocytes to release of brooded planulae was about 6 weeks. Planulae were 0.5–1.5 mm long and they settled and metamorphosed on a variety of substrates after 1–3 days. Spermaries, though more difficult to distinguish in histological sections, were present throughout the year. Spent spermaries were never observed in sections, but several colonies in Panamá and the Galápagos Islands released sperm from night one to night five after full moon, indicating the potential for cross-fertilization among colonies. Planula release was observed at Uva Island (Panamá) in March, May, June, and July, and in general planula presence was higher at warm ocean temperatures at all sites, whether or not the sites were influenced by seasonal upwelling. Annual fecundity estimates for T. coccinea are comparable with other high fecundity brooding species, including the zooxanthellate Porites panamensis, with which it co-occurs in Panamá. Tubastraea coccinea is widely distributed in the tropical Indo-Pacific and has colonized substrates in the western Atlantic. In addition to the reproductive characteristics described in the present study, other features of the biology of T. coccinea, such as an ability to withstand conditions that produce bleaching and mortality in zooxanthellate species, may account for its widespread, low-latitude distribution in multiple oceans. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. An erratum to this article can be found at     

Ultraviolet radiation effects on the behavior and recruitment of larvae from the reef coral Porites astreoides

We tested the rarely considered hypothesis that the ultraviolet portion (UVR, 280–400 nm) of the light spectrum affects patterns of recruitment in reef-building corals. The premise for this hypothesis rests in the fact that biologically relevant intensities of UVR penetrate to considerable depths (>24 m) in the clear waters surrounding many coral reefs, and that reef organisms allocate substantial resources to prevent and repair UVR damage. The ability of larvae spawned by the brown morph of the Caribbean coral, Porites astreoides, to detect and avoid UVR was assessed in petri dishes where one-half of the dish was shielded from UVR and the other exposed. Observations made every 30 min between 10:30 and 13:30 h showed significantly higher densities of larvae swimming in regions shielded from UVR. To determine how this behavior affects settlement patterns, larvae collected from P. astreoides adults at 18 m depth were released into chambers deployed at 17 m depth where they were given a choice of three different light regions in which to settle: PAR (PAR=400–700 nm), PAR+UVAR (UVAR=320–400 nm), and PAR+UVAR+UVBR (UVBR=280–320 nm). At the end of the experiment, greater numbers of P. astreoides larvae had settled in the region of the tube where UVR was reduced than would be expected if dispersion were random. To our knowledge, this is the first demonstration in any reef-building coral species that planula larvae can detect UVR and that it affects their choice of a settlement site. These results indicate that the capacity to detect and avoid habitats with biologically damaging levels of UVR may be one factor contributing to the successful recruitment of coral larvae.     

Reproductive traits of pioneer gastropod species colonizing deep-sea hydrothermal vents after an eruption

The colonization dynamics and life histories of pioneer species determine early succession at nascent hydrothermal vents, and their reproductive ecology may provide insight into their dispersal and population connectivity. Studies on the reproductive traits of two pioneer gastropod species, Ctenopelta porifera and Lepetodrilus tevnianus, began within a year after an eruption on the East Pacific Rise (EPR) that eliminated vent communities near 9°50′N from late 2005/early 2006. Standard histology was used to examine gamete release, instantaneous female fecundity, and time to maturation. Both species exhibited two-component oocyte size–frequency distributions indicating quasi-continuous reproduction with high fecundity. In samples collected in December 2006, both C. porifera and L. tevnianus individuals were reproductively mature. The smallest reproducing C. porifera were 4.2 mm (males) and 5.4 mm (females) in shell length, whereas reproductive L. tevnianus were smaller (2.3 and 2.4 mm in males and females, respectively). Most C. porifera were large (>6.0 mm) compared to their size at metamorphosis and reproductively mature. In contrast, most L. tevnianus were small (<1.0 mm) and immature. Reproductive traits of the two species are consistent with opportunistic colonization, but are also similar to those of other Lepetodrilus species and peltospirids at vents and do not fully explain why these particular species were the dominant pioneers. Their larvae were probably in high supply immediately after the eruption, due to oceanographic transport processes from remote source populations.     

Predicting structural complexity of reefs and fish abundance using acoustic remote sensing (RoxAnn)

This study determined whether the acoustic roughness of Caribbean reef habitats is an accurate proxy for their topographic complexity and a significant predictor of their fish abundance. Fish abundance was measured in 25 sites along the forereef of Glovers Atoll (Belize). At each site, in situ rugosity (ISR) was estimated using the “chain and tape” method, and acoustic roughness (E1) was acquired using RoxAnn. The relationships between E1 and ISR, and between both E1 and ISR and the abundance of 17 common species and the presence of 10 uncommon species were tested. E1 was a significant predictor of the topographic complexity (r ² = 0.66), the abundance of 10 common species of surgeonfishes, pomacentrids, scarids, grunts and serranids and the presence of 4 uncommon species of pomacentrids and snappers. Small differences in E1 (i.e. ∆0.05–0.07) reflected in subtle but significant differences in fish abundance (~1 individual 200 m⁻² and 116 g 200 m⁻²) among sites. Although we required the use of IKONOS data to obtain a large number of echoes per site, future studies will be able to utilise RoxAnn data alone to detect spatial patterns in substrate complexity and fish abundance, provided that a minimum of 50 RoxAnn echoes are collected per site.     

Temporal patterns of larval settlement and survivorship of two broadcast-spawning acroporid corals

Acroporid corals are the main reef-building corals that provide three-dimensional habitats for other reef organisms, but are decreasing on many reefs worldwide due to natural and anthropogenic disturbances. In this study, temporal patterns of larval settlement and survivorship of two broadcast-spawning acroporid coral species, Acropora muricata and A. valida, were examined through laboratory rearing experiments to better understand the potential for larval dispersal of this important coral group. Many larvae were attached (but not metamorphosed) to settlement tiles on the first examination 3–4 days after spawning (AS). The first permanent larval settlement (i.e. metamorphosed and permanently settled juvenile polyps) occurred at 5–6 days AS, and most larval settlement (85–97% of total) occurred within 9–10 days AS. Larval survivorship decreased substantially to around 50% by the first week of the experiment and to approximately 10% by the second to third week. The rates of larval attachment, settlement, and the initial drop in survivorship of larvae suggest that effective dispersal of some acroporid species may largely be completed within the first few weeks AS.     

Contrasting population genetic structures of sympatric, mass-spawning Caribbean corals

Coral reef conservation management policy often focuses on larval retention and recruitment of marine fish with scant data available on important, less motile reef-building species such as corals. To evaluate the concept of population connectivity in corals, we tested whether broadcast spawning reproduction per se confers the same degree of dispersal to two sister species, Montastraea annularis (Anthozoa: Scleractinia; Ellis and Solander 1786) and M. faveolata (Ellis and Solander 1786), both dominant taxa in reefs of the northern Caribbean. Genetic analyses of ten nuclear DNA loci (seven microsatellite and three single-copy RFLP) reveal strikingly different patterns of population genetic subdivision for these closely related, sympatric species, in spite of likely identical dispersal abilities. Strong population genetic structure typified the architecture of M. annularis, whereas M. faveolata populations were principally genetically well mixed. A higher level of clonality was observed in M. annularis potentially because of a susceptibility to physical fragmentation. Clonality did not, however, significantly contribute to population genetic structure or low-level Hardy–Weinberg and linkage disequilibria observed in some populations. The lack of consistent association between reproductive mode and dispersal reinforces the perspective that population connectivity is not so much a function of predictable marine population source and sink relationships as is due to a more complex interface of oceanic currents interacting with and amplifying stochastic fluctuations in larval supply and settlement success. Our results support others promoting an overall ecosystem approach in marine protected area design.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Seasonal and interannual variations in size,biomass and chemical composition of the eggs of North Sea shrimp, <Emphasis Type="Italic">Crangon crangon</Emphasis> (Decapoda: Caridea)

In the shrimp Crangon crangon, an important fishery resource and key species in the southern North Sea, we studied temporal variations in size, biomass (dry weight, W) and chemical composition (C, N, protein and lipid) of eggs in an initial embryonic stage. Data from 2 years, 1996 and 2009, consistently revealed that egg size and biomass varied seasonally, with maxima at the beginning of the reproductive season (January), decreasing values throughout spring, minima in June–July, and a slight increase thereafter. This cyclic pattern explains why “Winter eggs” are on average larger and heavier than “summer eggs”. Using a modelling approach, we estimated the duration of oogenesis in relation to seasonally changing seawater temperatures. According to an additive model of multiple explanatory variables, the C content per newly laid egg showed in both years a highly significant negative relationship with day length (r2 = 0.38 and 0.40, respectively; P < 0.0001), a weak positive relationship with temperature (r2 = 0.08 and 0.09; P < 0.05), and a weak negative relationship with phytoplankton biomass (r2 = 0.11 and 0.12; P < 0.05) at the estimated time of beginning oogenesis. Phenotypic plasticity in initial egg size and biomass is interpreted as an adaptive reproductive trait that has evolved in regions with strong seasonality in plankton production and periods of larval food limitation. In contrast to biomass per egg, the percentage chemical composition remained similar throughout the reproductive period. Both the absolute and percentage values also showed significant interannual variations, which caution against generalizations based on short-term studies of reproductive traits of C. crangon and other species of shrimp.     

Variation in colony geometry modulates internal light levels in branching corals, <Emphasis Type="Italic">Acropora humilis</Emphasis> and <Emphasis Type="Italic">Stylophora pistillata</Emphasis>

Colonial photosynthetic marine organisms often exhibit morphological phenotypic plasticity. Where such plasticity leads to an improved balance between rates of photosynthesis and maintenance costs, it is likely to have adaptive significance. To explore whether such phenotypic plasticity leads to more favourable within-colony irradiance for reef-building branching corals, this relationship was investigated for two coral species Acropora humilis and Stylophora pistillata, along a depth gradient representing light habitats ranging from 500 to 25 μmol photons m⁻² s⁻¹, during 2006 at Heron Island, Great Barrier Reef (23.44°S, 151.91°E). In the present study changes in flow-modulated mass transfer co-varied with light as a function of depth. In low-light (deep) habitats, branch spacing (colony openness) in A. humilis and S. pistillata was 40–50% greater than for conspecifics in high-light environments. Also, branches of A. humilis in deep water were 40–60% shorter than in shallow water. Phenotypic changes in these two variables lead to steeper within-colony light attenuation resulting in 38% higher mean internal irradiance (at the tissue surface) in deep colonies compared to shallow colonies. The pattern of branch spacing was similar for S. pistillata, but this species displayed an alternate strategy with respect to branch length: shade adapted deep and cave colonies developed longer and thinner branches, allowing access to higher mass transfer and irradiance. Corals in cave habitats allowed 20% more irradiance compared to colonies found in the deep, and had a 47% greater proportion of irradiance compared to colonies in the shallow high-light environment. Such phenotypic regulation of internal light levels on branch surfaces partly explains the broad light niches of many branching coral species. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Influence of environmental factors and female size on reproductive output in an invasive temperate marine gastropod <Emphasis Type="Italic">Rapana</Emphasis><Emphasis Type="Italic">venosa</Emphasis> (Muricidae)

Life history and reproductive strategies influence population dynamics at the inter- and intra-specific level. Environmental conditions suitable for gonad development and spawning, the reproductive range, may be a smaller portion of the broader species distribution. The only known breeding population of veined rapa whelks (Rapana venosa) in North America is in Chesapeake Bay, USA. There is considerable interest in the potential reproductive range of this non-indigenous species given the rapa whelk’s negative impacts on commercial shellfish species in both its native and introduced ranges. Weight-specific reproductive output is described for wild caught Chesapeake Bay rapa whelks maintained in flow-through mesocosms for 2 years. Measured reproductive output within and between egg capsule deposition seasons (years) in relation to water temperature, salinity, daylength, and female size is used to describe the rapa whelk’s reproductive range. Egg capsule production is influenced by seasonal and absolute water temperatures as well as seasonal daylength cycles. Egg capsule deposition by Chesapeake Bay rapa whelks begins at water temperatures of approximately 18°C and continues for 11–15 weeks. Forty to 70% of female whelks deposited egg capsules in most weeks during this season, producing 150–200 egg capsules female⁻¹ week⁻¹. Water temperatures >28°C caused reduced egg capsule production relative to temperatures of 20–25°C. Egg capsule production was positively related to seasonal changes in daylength, and two peaks of egg capsule deposition were observed in the 2001 and 2002 deposition seasons. The combination of declining daylength and higher water temperatures in late summer was associated with the cessation of egg capsule deposition. A lower average weight specific reproductive output in 130–145 mm SL rapa whelks (average 12 ± 1%) than in 90–106 mm SL rapa whelks (average 22 ± 1% of body weight) may reflect a life history that balances the physiological costs of maintaining a large body mass with the production of many planktonic larvae from multiple clutches of egg capsules per breeding season over a 10–15-year lifespan. Estimates of the cumulative day-degree requirements corresponding to the annual initiation of egg capsule deposition were 238 and 236 for 2001 and 2002, respectively. Reproductive output and day-degree requirements for Chesapeake Bay rapa whelks were similar to values calculated from previous studies of native muricids (Eupleura caudata and Urosalpinx cinerea). A latitudinal range of 30–41° (N and S) is predicted as the realized reproductive range for rapa whelk populations on the basis of the day-degree requirements for native whelks and reproductively active invasive rapa whelk populations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Reproductive energetics,endocrinology and population dynamics of Nephtys caeca and N. hombergi

An investigation of gametogenetic cycles and spawning success in populations of Nephtys caeca and N. hombergi from the River Tyne estuary, North Shields, England, in relation to production of gonadotrophic (GH) and spawning hormones (SH) has been made, based on data collected from 1978–1984. The data show that a consistent pattern of gametogenesis and efficient spawning occurs in populations of N. caeca in north-east England, but that the reproductive cycle of N. hombergi is erratic. Premature oosorption and gametogenic failure in this latter species is associated with a low level of GH production. Following high levels of GH production, gravid females sometimes fail to spawn owing to the non-release of SH. The reproductive energetics and reproductive success of N. caeca and N. hombergi are described in relation to the observed patterns of endocrine activity and the consequent changes in population structure.     

Multi-year observations on the gametogenic ecology of the Antarctic seastar <Emphasis Type="Italic">Odontaster validus</Emphasis>

This study reports the first multi-year observations on the reproductive patterns for an Antarctic predator/scavenger, Odontaster validus (Koehler 1912). Seastars were collected monthly from a shallow site (15–20 m depth) near the British Antarctic Survey (BAS) Rothera Research Station (Adelaide Island, 67°34′S 68°08′W) from July 1997 to January 2001. Reproductive condition, oocyte size frequencies and spermatogenesis were examined in at least ten seastars each month using histological and image analysis techniques. Gonad indices (GI) and pyloric caeca indices (PI) were also examined in the same samples. Female and male GIs varied seasonally, in parallel with a reduction in the proportion of large oocytes and mature sperm in the gonad in August to mid-October following winter spawning. Despite there being remarkable consistency in the timing of spawning from year to year, differences in the reproductive condition of individuals were apparent. Patterns in the digestive tissues also varied with season, peaking in December and reaching a minimum in February in two of the three study years. This weaker annual pattern may partly reflect the varied diet of this predator/scavenger species, which is not directly dependant on the timing and magnitude of the annual phytoplankton bloom. Pooled oocyte size distributions and residual analysis suggested that oogenesis progressed over 18–24 months, with the largest of the two size classes (maximum diameter = 183 μm) being spawned annually. This pattern of oocyte growth and spawning was previously reported in the early 1960s for an O. validus population from McMurdo Sound, which lies south of Rothera by 10° latitude. The extremely catholic diet of this predator/scavenger suggests the reproductive patterns of the seastar will be less susceptible to changes in food supply compared to polar suspension feeders or deposit feeders. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.