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     

Diel and lunar patterns of reproduction in the Caribbean and Pacific sergeant major damselfishes Abudefduf saxatilis and A. troschelii

Diel and lunar reproductive patterns of the Caribbean and Pacific sergeant major damselfishes Abudefduf saxatilis and A. troschelii respectively, were studied i the San Blas and Northern Perls Islands of Panama in 1981 and 1982. These are sister-species that have diverged since the uplift of the isthmus of Panama. Caribbean A. saxatilis females typically complete spawning in the nests of males earlier in the morning than do Pacific A. troschelii females. Spawning is rarely observed during the afternoon. Hatching occurs four or five days after spawning in the Caribbean species, and after four days in the Pacific species. In both, fry hatch during the hour following sunset. There also are differences in lunar patterns of spawning between the two species. The Caribbean A. saxatilis spawns throughout the month, exhibiting no lunar periodicity. In the Pacific A. troschelii spawns within nine days on either side of new moon. During the wet season, reproductive activity at a site spans three or four days, but is extended to eight or more days during dry season upwelling in the Bay of Panama. Thus, reproductive synchrony is much greater within than between colonies of the Pacific sergeant major, particularly in the wet season. Reproductive synchrony in the Pacific sergeant major might be beneficial because fry hatching at dusk encounter favorable tides for transport away from reef-based predators around new moon, or because reproductive synchrony reduces the risk of predation on unhatched embryos in nests guarded by males. Tidal amplitude and the rate of predation on embryos in nests are greater in the Pacific.     

Reproductive biology of the antipatharian black coral Antipathes fiordensis in Doubtful Sound, Fiordland, New Zealand

The reproductive biology of Antipathes fiordensis Grange, a species endemic to south-western New Zealand, was followed from April 1994 to May 1995. Ten colonies were individually tagged in Doubtful Sound and sampled on a monthly basis in order to determine their reproductive activity. The fecundity of each of the five tagged female colonies was determined by estimating the total number of polyps per colony from photographs of each colony and by planimetry, the proportion of gravid polyps per colony, and the mean number of oocytes per gravid polyp. In addition, 56 colonies were sampled in March 1995 to estimate the sex ratio, height at sexual maturity, and mean sizes of females and males. A. fiordensis was found to be a dioecious species which, in the absence of gonads in the polyps, has no obvious external morphological differences between the sexes. Broadcast spawning of gametes is the likely mode of reproduction. Gametogenesis began in November 1994 and was highly synchronous within and between colonies, with spawning occurring in March 1995. The sex ratio in adults was 1:1. Colonies reached sexual maturity between the heights of 70 and 105 cm which, based on existing estimates of growth rate, corresponds to a minimum age for sexual maturity of about 31 yr. The largest oocytes measured ranged from 100 to 140 μm in size. Female colonies produced between 1.3 and 16.9 million oocytes, with the larger colonies dominating the reproductive output of the population. Received: 23 June 1997 / Accepted: 1 August 1997     

Diet and seasonal prey capture rates in the Mediterranean red coral (Corallium rubrum L.)

Gorgonians are passive suspension feeders, contributing significantly to the energy flow of littoral ecosystems. More than in active suspension feeders (such as bivalves, ascidians and sponges) their prey capture is affected by spatial and temporal prey distribution and water movement. Corallium rubrum is a characteristic gorgonian of Mediterranean sublittoral hard bottom communities. This study found a high variability in the annual cycle of prey capture rate, prey size and ingested biomass, compared to other Mediterranean gorgonians. Detrital particulate organic matter (POM) was found throughout the year in the polyp guts and constituted the main proportion of the diet (25–44%). Crustacean fragments and copepods (14–46%) accounted for the second major proportion, while invertebrate eggs (9–15%) and phytoplankton (8–11%) constituted the smallest part of the diet. To verify the importance of detrital POM in the energy input of this precious octocoral species, in situ experiments were carried out during the winter–spring period. The results confirm the importance of detrital POM as the main source of food for C. rubrum [0.13±0.04 μg C polyp⁻¹ h⁻¹ (mean±SD)]. This study also compares the prey capture rates of two colony size classes and two depth strata: Within the same patch, small colonies (<6 cm height) captured significantly more prey per polyp (0.038±0.09 prey polyp⁻¹ h⁻¹) than larger colonies (>10 cm high) (0.026±0.097 prey polyp⁻¹ h⁻¹) and showed a higher proportion of polyps containing prey (17% compared to 10%). Comparing colonies of similar size (<6 cm height) revealed that the colonies situated at 40 m depth captured significantly more prey (0.038±0.09 prey polyp⁻¹ h⁻¹) than the ones at 20 m (0.025±0.11 prey polyp⁻¹ h⁻¹). One pulse of copepods was recorded that constituted 16% of all captured prey during the 15-month period studied in one of the sampled populations. The data suggest that the variability of hydrodynamic processes may have a higher influence on the feeding rate than seasonal changes in the seston composition. The carbon ingestion combined with data on the density of the exploited population results in 0.4–9.6 mg C m⁻² day⁻¹. The grazing impact of current, heavily exploited and small-sized populations is comparable to that of larger Mediterranean gorgonians, suggesting that unexploited red coral populations may have a high impact compared with other passive suspension feeders.     

Density,size structure and aspergillosis prevalence in <Emphasis Type="Italic">Gorgonia ventalina</Emphasis> at six localities in Puerto Rico

Gorgonia ventalina’s density, size structure and lesion prevalence was measured at six sites in Puerto Rico that exhibited variation in horizontal water transparency, sedimentation rates, suspended particle matter, scleractinian and macroalgal cover. G. ventalina density varied significantly among sites (between 0.84 and 0.007 colonies/m²), and was positively correlated with water transparency. Size structure did not vary much among sites, and reflects high mortality among the smaller size classes and high survivorship in large colonies. Prevalence of active fungi-induced lesions (type I) did not vary significantly among sites and was density-independent. However, prevalence of old lesions of unknown origin (type II) did vary among reefs and was negatively correlated with water transparency. Prevalence of types I or II lesions was independent of colony size. Our results suggest that (1) turbidity and sedimentation are important abiotic factors controlling the abundance of sea fans, (2) variation in settlement success and early survivorship of recruits has more impact on the sea fan populations than variation in the survivorship of large colonies and (3) prevalence of aspergillosis (type I) at the studied sites is similar to that reported for other Caribbean reefs and supports the epizootic nature of the disease and (4) lesions with exposed skeleton are more likely to be colonized by fouling organisms at impacted reefs. The combined effects of anthropogenic impacts and aspergillosis may cause local extinctions of sea fans, as is becoming evident in many reefs in Puerto Rico.     

On the sociobiology of four puerto rican parrotfishes (Scaridae)

Behavioral observations were made during SCUBA excursions out of the PRINUL underwater laboratory, off the west coast of Puerto Rico. Most of the work involved four species of parrotfishes, Sparisoma viride, Sparisoma aurofrenatum, Scarus croicensis and Scarus taeniopterus. The species of Sparisoma are relatively patrilocal, solitary, slowly and steadily feeding fishes; the terminal phase (termphase) males of S. aurofrenatum hold large territories that encompass the home ranges, possibly territories, of a number of females. The two species of Scarus are roving, aggregating fish that periodically descend to the bottom where they feed rapidly. Reproductive males are of two types, either highly dimorphic, brilliantly colored termphase males, or midphase males that resemble the females. At times, termphase males become territorial and are visited by females and midphase males. Females spawn with termphase and with midphase males. Aggression in all four species was directed largely to conspecific individuals. All species show the ability to change color rapidly, sometimes dramatically, in social interactions.     

Comparative aspects of sexual reproduction in the Caribbean coral genus Diploria (Scleractinia: Faviidae)

The increasing decline of Caribbean reef-building species underlines the importance of more information on their reproductive biology and ecology. This study compares the reproductive biology of the three species of Diploria, an important Caribbean reef-building genus affected by bleaching and disease, by: (a) characterizing their gametogenetic cycles simultaneously, (b) exploring the spatial and temporal variability in reproductive traits within and across species, (c) assessing fecundity and the minimum size of sexual reproduction, and (d) comparing information with other studies in the Caribbean. Starting in 1999, one tissue core was collected every month (for 17 months) from each of at least five large, tagged colonies of each species in La Parguera, Puerto Rico. Three more temporally spaced samplings were done during summer of 2000 and winter–spring of 2001 and 2002. Tissues were fixed in Helly’s solution, rinsed in fresh water, decalcified with 10% HCl, and preserved in 70% ethanol, embedded in paraplast, cut, and thin slides (7 μm) prepared and stained with Heidenhain’s Aniline-Blue method. Maximum egg size, number of eggs and spermaries were measured and gametogenetic cycles assessed. Microscopic observations confirmed that all three species were simultaneous hermaphrodites with a single, annual gametogenetic cycle. Spermatocytes and oocytes developed within the same mesentery but were not intermingled. Female gametes developed several months earlier than that of males, but both reached maturation simultaneously. Minor differences in the onset of gametogenesis were found for D. strigosa and D. clivosa, with both spawning after 10 p.m. between 8 and 10 days after the August and/or September full moons. D. labyrinthiformis on the other hand, began oogenesis in early July and spawned after 11 p.m. between 7 and 10 days after the April and/or May full moons. Spatial and temporal variability in mean number of spermaries and eggs/mesentery among colonies within and among species were found. D. labyrinthiformis had consistently significant higher mesenterial and polyp fecundity compared to the other two species over the 3 years. Average egg diameter varied between 240 and 246 μm and was similar among the three species. D. strigosa and D. clivosa sexual reproductive characteristics were similar to those of other large broadcast spawning Faviidae (i.e. Montastraea spp) in the region. In contrast, D. labyrinthiformis was a spring spawner (similar to Colpophyllia natans in Puerto Rico), which together with its significantly different micromorphology suggests that it might be phylogenetically more distant to the other taxa.     

Reproductive success in the Caribbean octocoral Briareum asbestinum

For most sessile marine invertebrates the number of offspring produced by an individual is often determined indirectly from counts of eggs present, with the assumption that all or most become viable offspring. Few field data on the actual number of offspring produced per individual (reproductive success) have been reported. We examined reproductive success in the octocoral, Briareum asbestinum (Pallas), by measuring embryo densities on 40 female colonies on two reefs (Pinnacles and House reefs) in the San Blas Islands, Panama from 1986 to 1988. The percentage of female colonies with mature eggs which subsequently released embryos was low, ranging from 46.6% in 1986 to 5.0% in 1988. Reproductive success was significantly different between reefs. Pinnacles reef had significantly more successful colonies (those releasing embryos) than House reef in all three years and significantly higher embryo densities in 1986 and 1987. There was a significant positive correlation between female reproductive success and the density and proximity of nearby males in both 1986 and 1987. In addition, fertile female branches placed 25 cm away from male branches produced significantly more embryos than female branches placed 50 cm away. In 1988 two groups of female branches were placed at distances of <50 cm and 5 m from four large male colonies at Pinnacles reef. Of the 20 female branches placed 5 m from the males none released embryos while 35% (7 of 20 branches) of the branches <50cm from males released embryos. These data indicate that simple counts of mature eggs present within female colonics prior to the reproductive season provide a poor estimate of reproductive success in B. ashestinum and that female reproductive success is positively influenced by the close proximity of males.     

Reproductive consequences of male body mass and aggressiveness depend on females’ behavioral types

Relatively few investigations explicitly test for concordant versus conflicting selection pressures from intrasexual versus intersexual selection. Here, we examine the effects of male body mass and behavioral type (BT) on reproductive success in the spider Anelosimus studiosus, with emphasis placed on the potential interaction between intrasexual and intersexual selection influences. Female A. studiosus exhibit either an aggressive-active or docile-passive BT, both of which co-occur in multifemale colonies. Males, in contrast, exhibit a more continuous distribution of behavioral tendencies. We investigated the male traits favored by females in five trial types: one docile female, one aggressive female, four docile females, four aggressive females, and two docile and two aggressive females. Male reproductive success was estimated by the number eggs produced by females following staged mating trials. In previous work, it was established that large aggressive males are favored in male–male contests, an intrasexual effect. However, large aggressive males were not universally favored here. We failed to detect an effect of male body mass or aggressiveness on reproductive success in trials with all docile females; however, in situations involving aggressive females, large aggressive males experienced diminished reproductive success relative to small docile males. Large, aggressive males were also more likely to be attacked and killed by aggressive females in the first 20 min of staged encounters and were more likely to be found dead after 72 h of unobserved interactions. Taken together, our data suggest that the reproductive consequences of male traits differ based on (1) the aspect of sexual selection being considered (intrasexual versus intersexual) and (2) the BT of their prospective mates: large aggressive males enjoy advantages in intrasexual selection and when courting docile females and small docile males experience reduced risk of cannibalism and increased reproductive success with aggressive females.     

Seasonal cycle of sexual reproduction of the Mediterranean soft coral Alcyonium acaule (Anthozoa, Octocorallia)

Alcyonium acaule (Cnidaria, Octocorallia) is a common, hard-bottom soft coral in the northwestern Mediterranean Sea. This study describes sexual reproduction and the gamete development cycle of this soft coral. A population at 15–18 m depth in the Marine Protected Area of the Medes Islands (42º02′55″ N, 3º13′30″ E) was sampled from July 1994–August 1995. A. acaule is gonochoristic and a surface brooder, spawning once a year in early summer. The mean diameter of ripe spermatic sacs was 400 ± 91 (SD) μm, and the mean diameter of mature oocytes was 473 ± 37 (SD) μm. There were 30 spermatic sacs polyp^?1 in males and 14 oocytes polyp^?1 in females. Different phases of gametogenesis in female and male colonies were examined separately with respect to seasonal changes in bottom temperature and solar irradiance. The data suggest that the relatively constant temperatures in January–April are probably not related to oocyte maturation, but that rising temperatures in May could affect sperm maturation. Rapidly increasing solar irradiance in March may be the trigger for vitellogenesis and oocyte maturation, although the mechanism for this in anthozoans is not understood.     

Seasonality in reproduction of the deep-water pennatulacean coral Anthoptilum grandiflorum

The deep-sea pennatulacean coral Anthoptilum grandiflorum exhibits a cosmopolitan distribution and was recently determined to serve as habitat for other invertebrates and fish larvae in the northwest Atlantic. Colonies collected at bathyal depths between 2006 and 2010 in eastern Canada were analysed to determine their fecundity and characterize spatial and temporal trends in their reproductive cycle. Anthoptilum grandiflorum is a gonochoric broadcast spawner with a sex ratio that does not differ significantly from equality (although one hermaphrodite colony was observed). In male colonies, all the spermatocysts synthesized become mature over the annual cycle, while only ~21 % of the initial production of oocytes reaches maturity in female colonies. Female potential fecundity based on mature oocytes just before spawning was on average 13 oocytes polyp^?1; male potential fecundity was 48 spermatocysts polyp^?1. The spawning period of A. grandiflorum differs between geographic regions, from April (in southern Newfoundland) to July (in Labrador), closely following regional spring phytoplankton blooms after accounting for the deposition of planktic detritus. Release of oocytes by a live colony held in the laboratory was recorded in April 2011, coincident with field data for similar latitudes. Seawater temperatures at the time of spawning were around 3.6–4.8 °C in all regions and in the laboratory. Early stages of gametogenesis were detected in colonies collected shortly after the spawning season, and early and late growth stages occurred successively until December. Mature colonies were observed between April and July (depending on latitude). The diameter of mature oocytes (~1,100 μm maximum diameter) is consistent with lecithotrophic larval development.     

Eusociality and extraordinary sex ratios in the spider Anelosimus eximius (Araneae: Theridiidae)

Summary Colonies of Anelosimus eximius in Panama had an average sex ratio of 0.15±sd 0.09, i.e. about five females for each male. The sex ratio in egg sacs reared was even lower (0.08±0.01), as was that of immatures in newly founded colonies (0.12±0.05). The possible mechanisms responsible are discussed. Mature colonies had an average ratio of 17 females and 2 males for each egg sac present (range: 2–91 females, 0.2–8.2 males) and contained a large proportion of females which were not inseminated but which presumably help. Since both sexes are diploid, arrhenotoky can be ruled out and it is assumed that some females do not come to reproduction, the proportion depending on the availability of resources. This mechanism may enable entire colonies to survive lean times.     

Clinal variation in anuran advertisement calls: basis for acoustic isolation?

Summary The calls of male treefrogs (Eleutherodactylus coqui) were studied along an altitudinal gradient in the Luquillo Mountains in eastern Puerto Rico. The fundamental frequency of each note in the advertisement call was highly negatively correlated with altitude. Although males responded vigorously to playbacks of calls of other males recorded at their own altitude, males at high altitudes responded less frequently to recorded calls of males from low altitudes, and males at low altitudes responded less frequently to recorded calls of males from high altitudes. These results are discussed in relation to potential isolation in contiguous populations of E. coqui.     

Prey, feeding rates, and asexual reproduction rates of the introduced oligohaline hydrozoan Moerisia lyonsi

Moerisia lyonsi Boulenger (Hydrozoa) medusae and benthic polyps were found at 0 to 5‰ salinity in the Choptank River subestuary of Chesapeake Bay, USA. This species was introduced to the bay at least 30 years before 1996. Medusae and polyps of M. lyonsi are very small and inconspicuous, and may occur widely, but unnoticed, in oligohaline waters of the Chesapeake Bay system and in other estuaries. Medusae consumed copepod nauplii and adults, but not barnacle nauplii, polychaete and ctenophore larvae or tintinnids, in laboratory experiments. Predation rates on copepods by medusae increased with increasing medusa diameter and prey densities. Feeding rates on copepod nauplii were higher than on adults and showed no saturation over the range of prey densities tested (1 to 64 prey l⁻¹). By contrast, predation on copepod adults was maximum (1 copepod medusa⁻¹ h⁻¹) at 32 and 64 copepods l⁻¹. Unexpectedly, M. lyonsi colonized mesocosms at the Horn Point Laboratory during the spring and summer in 4 years (1994 to 1997), and reached extremely high densities (up to 13.6 medusae l⁻¹). Densities of copepod adults and nauplii were low when medusa densities were high, and estimated predation effects suggested that M. lyonsi predation limited copepod populations in the mesocosms. Polyps of M. lyonsi asexually produced both polyp buds and medusae. Rates of asexual reproduction increased with increasing prey availability, from an average total during a 38 d experiment of 9.5 buds polyp⁻¹ when each polyp was fed 1 copepod d⁻¹, to an average total of 146.7 buds polyp⁻¹ when fed 8 copepods d⁻¹. The maximum daily production measured was 8 polyp buds and 22 medusae polyp⁻¹. The colonizing potential of this hydrozoan is great, given the high rates of asexual reproduction, fairly wide salinity tolerance, and existence of a cyst stage. Received: 29 October 1998 / Accepted: 3 March 1999     

Temporal variability in zooplankton prey capture rate of the passive suspension feeder<Emphasis Type="Italic"> Leptogorgia sarmentosa</Emphasis> (Cnidaria: Octocorallia), a case study

There is increasing evidence that suspension feeders play a significant role in plankton–benthos coupling. However, to date, active suspension feeders have been the main focus of research, while passive suspension feeders have received less attention. To increase our understanding of energy fluxes in temperate marine ecosystems, we have examined the temporal variability in zooplankton prey capture of the ubiquitous Mediterranean gorgonian Leptogorgia sarmentosa. Prey capture was assessed on the basis of gut content from colonies collected every 2 weeks over a year. The digestion time of zooplankton prey was examined over the temperature range of the species at the study site. The main prey items captured were small (80–200 µm), low-motile zooplankton (i.e. eggs and invertebrate larvae). The digestion time of zooplankton prey increased when temperature decreased (about 150% from 21°C to 13°C; 15 h at 13°C, 9 h at 17°C, and 6 h at 21°C), a pattern which has not previously been documented in anthozoans. Zooplankton capture rate (prey polyp^–1 h^–1) varied among seasons, with the greatest rates observed in spring (0.16±0.02 prey polyp^–1 h^–1). Ingestion rate in terms of biomass (g C polyp^–1 h^–1) showed a similar trend, but the differences among the seasons were attenuated by seasonal differences in prey size. Therefore, ingestion rate did not significantly vary over the annual cycle and averaged 0.019±0.002 g C polyp^–1 h^–1. At the estimated ingestion rates, the population of L. sarmentosa removed between 2.3 and 16.8 mg C m^–2 day^–1 from the adjacent water column. This observation indicates that predation by macroinvertebrates on seston should be considered in energy transfer processes in littoral areas, since even species with a low abundance may have a detectable impact.Communicated by S.A. Poulet, Roscoff     

The adaptive significance of male polymorphism in the acarid mite Caloglyphus berlesei

Summary Two forms of males occur in the acarid mite, Caloglyphus berlesei. One of them uses its thickened third pair of legs to kill other males; the other, without modified legs, does not attack other males. Previous studies have shown that the form of the male is environmentally determined: fighter males develop only at low population densities and their development can be suppressed by substances emanating from dense colonies. In this study, the duration of development, longevity and virility of the two male morphs were measured. The only significant difference was that fighters had a shorter development time between the two last moults. In another experiment, two groups of colonies were maintained under the same conditions but had different numbers of individuals: small colonies contained 2 fighters and 2 non-fighters, whereas large colonies contained 30 males of each type. The relative reproductive success of both morphs was estimated from numbers of matings. In small colonies, the estimated reproductive success (ERS) was significantly higher for fighters than for non-fighters, mainly because in over 50% of these colonies a single fighter male managed to kill all the rival males and monopolize the females. The opposite was true in large colonies, in which non-fighters achieved significantly higher ERS, mainly because the fighters were killed in fights more often than the non-fighters. This implies that the ratio of costs to benefits obtained by adopting the fighter-male strategy increases with the number of rival males, which may explain conditional male development in C. berlesei.     

Estimates of species- and ecosystem-level respiration of woody stems along an elevational gradient in the Luquillo Mountains, Puerto Rico

We measured CO₂ efflux from stems of seven subtropical tree species situated along an elevational gradient in the Luquillo Mountains, Puerto Rico and scaled these measurements up to the landscape level based on modeled and empirical relations. The most important determinants of ecosystem stem respiration were species composition and stem temperature. At a species scale, measured CO₂ efflux per unit bole surface area at a given temperature was highest in the early successional species Cecropia schreberiana and lowest in species that inhabit high elevations such as Micropholis garciniifolia and Tabebuia rigida. Carbon dioxide efflux rates followed a diel pattern that lagged approximately 6 h behind changes in sapwood temperatures. At an ecosystem scale, our simulation model indicates a decreasing trend of stem respiration rates with increasing elevation due to shifts in species composition, lower temperatures and reductions in branch surface area. The highest estimated stem respiration rates were present in the lowland tabonuco forest type and the lowest rates were present in the elfin forest type (mean 7.4 and 2.1 Mg C ha⁻¹ yr⁻¹, respectively). There was slight temperature-induced seasonal variation in simulated stem respiration rates at low elevations, with a maximum difference of 19% between the months of February and July. Our results coincide well with those of Odum and Jordan [Odum, H.T., Jordan, C.F., 1970. Metabolism and evapotranspiration of the lower forest in a giant plastic cylinder. In: Odum, H.T., Pigeon, R.F. (Eds.), A Tropical Rain Forest: A Study of Irradiation and Ecology at El Verde, Puerto Rico. U.S. Atomic Energy Commission, Oak Ridge, TN, pp. I165–I189] for the tabonuco forest type and extend their work by presenting estimates and spatial patterns of woody tissue respiration for the entire mountain rather than for a single forested plot.     

Absence of sex-differential brood raising by workers in Diacamma sp. from Japan

To optimally allocate resources between workers, reproductive females, and males, ant workers have to be able to identify the sex of larvae and raise them differently. The ability of workers to discriminate between the sexes in the brood was tested in colonies of queenless ponerine ants, Diacamma sp., from Japan. The ratio of male eggs in the egg pile was increased experimentally. This manipulation resulted in a corresponding increase in the ratio of adult males, suggesting that Diacamma workers do not raise the sexes differently. Received: 4 November 1997 / Accepted after revision: 14 March 1998     

Secondary polygyny by inbred wingless sexuals in the dolichoderine ant Technomyrmex albipes

Summary Technomyrmex albipes makes huge polydomous colonies which consist of up to several millions of adults. In field colonies, dealate queens are rare or absent, though winged males and winged females emerge annually (synchronously) in large numbers from late may to mid June. Field and laboratory observations showed that the reproduction of established colonies was performed by wingless females inseminated by wingless males from the same colony. Dissections and morphological examinations revealed that wingless females are workers with no spermatheca and intercastes with a spermatheca. Most intercastes were inseminated, had developed ovaries, and seemed to reproduce, while workers did not seem to reproduce. Extranidal tasks were performed only by workers. Approximately half of the adult population were intercastes, and wingless males represented only a small portion of all adults, the rest being nonreproductive workers. Intercastes and wingless males were produced throughout the year except in winter. The winged females and males copulate outside the nest only after the nuptial flight and the dealate females are able to perform independent founding, but they are also eventually supplanted by intercastes. The adoption of dealate queens by an established natal colony did not seem to occur. Thus we infer that in this species the winged reproductives disperse and found new colonies, while inbred wingless reproductives allow the enlargement and budding of colonies. This species has a special trophic-flow system. There is no trophallaxis among adults, and nutrient transfer from adults to other colony members is achieved exclusively by specialized trophic eggs. All females (dealate queens, intercastes, and workers) seem to produce trophic eggs. This aphid-like life cycle, i.e., the occurrence of both winged and wingless reproductive forms, may have evolved as an adaptation supporting the development of secondary polygyny and polydomy.Offprint requests to: K. Yamauchi     

Sexual selection and the tail ornaments of North American barn swallows

Summary In this study conducted in southeastern Ontario, Canada, we manipulated the length of outer tail feathers (streamers) of male barn swallows (Hirundo rustica) shortly after they returned to four small breeding colonies in the spring. Both streamers on most males in these colonies were experimentally either lengthened or shortened by 20 mm and as a result 10 randomly chosen males of each category had their streamer lengths manipulated before the fertile period of their mate. Males with elongated streamers had a significantly shorter pre-laying period (from arrival until first egg date) than those with shortened streamers and we interpret this as indicating that they obtained their mates more rapidly. Females mated to elongated males had significantly longer tails and laid their first egg significantly earlier than those mated to shortened males; no other indices of reproductive success differed between these two experimental groups. These results provide some support for previous work suggesting that females prefer males with longer streamers and thus that streamer length in this species is under the influence of sexual selection. We also found that males with longer natural streamers were significantly more likely to break them and that males were much more likely to break their streamers than were females. Since males participate in incubation in North America but not in Europe, we suggest that the aerodynamic disadvantages of streamer breakage that result from incubation attentiveness are at least partly responsible for the shorter streamer length of males in North America. Offprint requests to: R. Montgomerie