Adult Colonies Research Articles

Expression of cytochrome P450 enzymes in hepatic organoid reconstructed by rat small hepatocytes

Small hepatocytes (SH), which are hepatic progenitor cells, were isolated from an adult rat liver. SH in a colony sometimes change their shape from small to large and from flat to rising/piled-up. The morphological changes of SH may be correlated with hepatic maturation. Cytochrome P450s (CYP) are drug-metabolizing enzymes and the expression is one of hepatic differentiated functions. However, it is well known that the re-expression and maintenance of CYP activity are very difficult in cultured hepatocytes. We investigated the expression of CYP and the enzymatic activities in long-term cultured SH. SH were isolated from adult rat livers and SH colonies were collected, replated on new dishes, and then cultured. CYP1A1/2, CYP2B1, CYP3A2, CYP4A1, and CYP2E1 were induced by the addition of 3-methylcholanthrene, phenobarbital, pregnenolone-16alpha-carbonitrile, clofibric acid, and ethanol, respectively. Immunocytochemistry, immunoblots, and enzyme activities were examined. SH could differentiate into mature hepatocytes by the addition of Matrigel and re-express constitutive CYPs. The expression of CYP1A1/2, CYP2B1, CYP3A2, and CYP4A1 dose-dependently increased and the amounts gradually increased with time in culture, especially in the cells treated with Matrigel. Activities of CYP1A, CYP2B, CYP3A and CYP2E in SH treated with Matrigel induced by each of the inducers were approximately 120-fold, 2.8-fold, 6.4-fold and 0.8-fold higher than in the control. The matured SH could re-express the constitutive CYP and recover inducibility, not only of protein expression but also of enzyme activities.

Influence of environmental conditions on early development of the hydrothermal vent polychaete Alvinella pompejana

Dispersal and colonisation processes at deep-sea vents are still not fully understood, essentially because early life stages of vent species remain unknown. The polychaete worm Alvinella pompejana forms colonies on chimney walls at East Pacific Rise vent sites where the temperature can frequently exceed 20 degrees C. In vitro studies in pressure vessels showed that the early embryos tolerate temperatures in a lower range (10-14 degrees C), suggesting that they would have to escape the colony to develop. Pressure vessels offer the advantage that each parameter can be independently controlled, but they do not simulate the more complex and dynamic conditions naturally encountered at vent sites. Accordingly, in addition to incubations in pressure vessels, we incubated embryos directly at a vent site, in different habitats along a gradient of hydrothermal influence. Embryos incubated on an adult A. pompejana colony where temperature and H(2)S concentrations were relatively high showed a very low survival rate and did not develop, whereas embryos incubated in a Riftia pachyptila clump environment with a lower hydrothermal signature, or at the base of the chimney where the influence of the hydrothermal activity was very weak, survived well and developed. Although the average temperature recorded in the A. pompejana colony was within the range tolerated by embryos (13 degrees C), frequent peaks above 20 degrees C were recorded. Estimated sulphide concentration at this site reached 200 mumol l(-1). Punctuated exposure to both high temperature and elevated sulphide levels probably explain the low survival of embryos within the A. pompejana colony. The in situ experiments further support the idea that embryos require conditions with moderate hydrothermal influence not generally found within an adult colony. However, as much more benign physicochemical conditions can be found within a few tens of cm of adult colonies, embryos do not necessarily have to leave their vent of origin to develop. Further analyses are needed to pinpoint the specific factors that affect the survival and development of embryos at vents.

A demographic approach to monitoring the health of coral reefs

Inshore coral reefs adjacent to the wet tropics in North Queensland, Australia, are regularly exposed to flood plumes from coastal river systems. Changes in the nature of these plumes have been linked to the declining health of coral reefs in the region. The effect of flood plumes on the health of inshore corals was investigated by quantifying aspects of the demography of populations of corymbose and digitate Acropora at three groups of Island reefs along a gradient of exposure and decreasing water quality (High Island >Frankland’s >Fitzroy). The size-structures of colonies, the rates of sexual recruitment, and the growth and survival of juveniles, all varied among the Island reefs. Juvenile and adult sized colonies were far more abundant at the Fitzroy Island reefs, than at the High or Frankland Island reefs that were more exposed to flood plumes. Additionally, there were up to eight times as many sexual recruits at the Fitzroy Island reefs, compared with the High Island reefs. However, the rates of growth and survival of the juvenile sized corals at the Fitzroy Island reefs were lower than at the more exposed reefs. The comparatively low abundance of adult corals at the exposed reefs is most likely due to their histories of disturbance from crown-of-thorns and coral bleaching, but the lack of subsequent recovery due to their low levels of larval recruitment. If a stock-recruitment relationship is typical for these groups of reefs, then the low rates of recruitment may be linked to the low density of adult colonies. Alternately, direct or indirect effects of chronic exposure to poor water quality may have resulted in less suitable substrata for larval settlement. We discuss these results and provide examples of how information about population structure and dynamics can be used in simple matrix models to quantify the current and future health of populations of corals under various scenarios.

Effects of the herbicide diuron on the early life history stages of coral

The effects of the herbicide diuron on the early life history stages of broadcast spawning and brooding corals were examined in laboratory experiments. Fertilisation of Acropora millepora and Montipora aequituberculata oocytes were not inhibited at diuron concentrations of up to 1000 μg l −1. Metamorphosis of symbiont-free A. millepora larvae was only significantly inhibited at 300 μg l −1 diuron. Pocillopora damicornis larvae, which contain symbiotic dinoflagellates, were able to undergo metamorphosis after 24 h exposure to diuron at 1000 μg l −1. Two-week old P. damicornis recruits on the other hand were as susceptible to diuron as adult colonies, with expulsion of symbiotic dinoflagellates (bleaching) evident at 10 μg l −1 diuron after 96 h exposure. Reversible metamorphosis was observed at high diuron concentrations, with fully bleached polyps escaping from their skeletons. Pulse amplitude modulation (PAM) chlorophyll fluorescence techniques demonstrated a reduction in photosynthetic efficiency ( Δ F / F m ′ ) in illuminated P. damicornis recruits after a 2 h exposure to 1 μg l −1 diuron. The dark-adapted quantum yields ( F v/ F m) also declined, indicating chronic photoinhibition and damage to photosystem II.

An Association between Freshwater Sponges and the Zebra Mussel in a Southern Lake Michigan Harbor

ABSTRACT Freshwater sponges (Spongillidae) were evaluated in a southern Lake Michigan harbor to determine whether preferences existed for attachment sites. Sponges were enumerated that were growing epifaunally on zebra mussel shells and directly on the associated iron revetment wall surrounding a portion of the harbor. Adult colonies of sponges were non-randomly distributed and found in close association with zebra mussel shells. The mechanism for this biotic interaction is unknown. However, this is another example of benthic restructuring of native fauna precipitated by the non-indigenous zebra mussel.

LONG‐TERM ASSESSMENT OF TEMPERATE OCTOCORAL MORTALITY PATTERNS, PROTECTED VS. UNPROTECTED AREAS

Coastal marine protected areas (MPAs) are usually established with an aim to protect areas of special ecological value. However, protected areas tend to attract more tourism and associated recreational activities, thereby exposing the biota to new risks such as high diving activity. The effects of these drawbacks are still little known for low‐dynamic systems such as one of the most characteristic and fragile Mediterranean communities, the coralligenous community. Mortality rates were assessed in both heavily dived and lightly dived areas to evaluate the effect of diving on the survival of the gorgonian Paramuricea clavata. The study was designed to distinguish human‐induced causes from natural causes of gorgonian mortality and to provide criteria for sustainable management of protected areas. We examined total and partial mortality of adult colonies (>10 cm in height) at four locations, two each representing one of the two situations, heavily dived (MPA) and lightly dived (control), annually over a 9‐yr period (1992–2000).High levels of recreational activity did not affect the degree of injury of the colonies. On average, the proportion of live tissue of the colonies remained steady at ∼91%. Colony death by detachment was the main source of mortality at the MPA, four times higher than death due to overgrowth. Mortality rate due to overgrowth remained constant at both areas with an average of 1.2%/yr. Natural mortality rate in sites with low diving activity was estimated to be about 2.7%/yr, whereas high diving activity was estimated to increase the natural mortality rate of the species by a factor of three, up to ∼7.4%/yr. The demographic characteristics of long‐lived low‐turnover structural components of ecosystems makes them especially vulnerable to disturbance events. Since an increase in diving activity seems to be unavoidably brought about by the creation of any MPA, strict regulation of recreational activity must be guaranteed in areas with low‐turnover communities.

A new method for measuring growth and age in the precious red coral Corallium rubrum (L.)

A new technique for aging red coral Corallium rubrum (L.) colonies based on staining the organic matrix found in the axial calcareous skeleton is presented and validated. This method provided clear-cut images of growth rings of red coral. To demonstrate their annual periodicity, two approaches have been used: (i) applying this technique to adult colonies of known age (more than 20 years old), and (ii) labeling colonies with calcein and allowing them to grow for 1 year. Results provided evidence of the annual periodicity of growth rings. This new method assesses colony age with an underestimate of true age by 3–4 years. The difference between estimated age and actual age could be attributed to the phase of initial growth during which rings are not formed. Colonies from different sites, depths, and habitats (n=33) were analyzed yielding preliminary data on longevity and mean growth rates in red coral. Colonies from shallow habitats (15–62 m) examined here with basal diameter of about 7 mm were at least 30–40 years old. Mean growth rate of basal diameter was 0.35±0.15 mm year−1. Comparison with previous aging methods used for red coral resulted in considerable differences in estimations of age (about 10 years greater in this study) and growth rates (about four times lower). The application of this method to red coral will provide key data as a basis for developing management and conservation plans for this valuable species.

The role of sexual and asexual reproduction in structuring high latitude populations of the reef coral Pocillopora damicornis.

The genotypic composition of populations of the asexually viviparous coral Pocillopora damicornis varies in a manner that challenges classical models of the roles of sexual and asexual reproduction. On the geographically isolated Hawaiian reefs and high latitude reefs in Western Australia, P. damicornis populations are highly clonal although it has been argued that sexual reproduction via broadcast spawning generates widely dispersed colonists. In contrast, on eastern Australia's tropical Great Barrier Reef populations show little evidence of clonality. Here, we compare the genotypic diversity of adult and juvenile colonies of P. damicornis at seven sites on eastern Australia's high latitude Lord Howe Island reefs to determine if levels of clonality vary with habitat heterogeneity and age of colonies (as predicted by theory) or alternatively if clonality is again always high as for other isolated reef systems. We found 55-100% of the genotypic diversity expected for random mating at all seven sites and little evidence of asexual recruitment irrespective of habitat heterogeneity (sheltered versus wave exposed) or colony age. We found reduced levels of genetic diversity compared with tropical reefs (2.75 versus 4 alleles/locus), which supports earlier findings that Lord Howe Island is an isolated reef system. Furthermore, heterozygote deficits coupled with significant genetic subdivision among sites (FST=0.102+/-0.03) is typical of populations that have limited larval connections and are inbred. We conclude that the genetic structure of P. damicornis at Lord Howe Island reflects populations that are maintained through localised recruitment of sexually produced larvae.

The ecotoxicology of vegetable versus mineral based lubricating oils: 3. Coral fertilization and adult corals

Biodegradable vegetable-derived lubricants (VDL) might be less toxic to marine organisms than mineral-derived oils (MDL) due to the absence of high molecular weight aromatics, but this remains largely untested. In this laboratory study, adult corals and coral gametes were exposed to various concentrations of a two-stroke VDL-1A and a corresponding MDL to determine which lubricant type was more toxic to each life stage. In the fertilization experiment, gametes from the scleractinian coral Acropora microphthalma were exposed to water-accommodated fractions (WAF) of VDL-1A and MDL for four hours. The MDL and VDL-1A WAFs inhibited normal fertilization of the corals at 200 μg l−1 total hydrocarbon content (THC) and 150 μg l−1 THC respectively. Disturbance of a stable coral-dinoflagellate symbiosis is regarded as a valid measure of sub-lethal stress in adult corals. The state of the symbiosis in branchlets of adult colonies of Acropora formosa was monitored using indicators such as dinoflagellate expulsion and dark-adapted photosystem II yields of dinoflagellate (using pulse amplitude modulation fluorescence). An effect on symbiosis was measurable following 48 h exposure to the lubricants at concentrations of 190 μg l−1 and 37 μg l−1 THC for the MDL and VDL-1A respectively. GC/MS revealed that the main constituent of the VDL-1A WAF was the compound coumarin, added by the manufacturer to improve odour. The fragrance containing coumarin was removed from the lubricant formulation and the toxicity towards adult corals re-examined. The coumarin-free VDL-2 exhibited significantly less toxicity towards the adult corals than all of the other oil types tested, with the only measurable effect being a slight but significant drop in photosynthetic efficiency at 280 μg l−1.

Checking the landing zone: do invertebrate larvae avoid settling near superior spatial competitors?

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 280:239-247 (2004) - doi:10.3354/meps280239 Checking the landing zone: Do invertebrate larvae avoid settling near superior spatial competitors? Stephan G. Bullard1,3, Robert B. Whitlatch1,*, Richard W. Osman2 1Department of Marine Sciences, University of Connecticut, Groton, Connecticut 06340, USA 2Smithsonian Environmental Research Center, PO Box 28, 647 Contees Wharf Road, Edgewater, Maryland 21037, USA 3Present address: University of Hartford Hillyer College, 200 Bloomfield Av., West Hartford, Connecticut 06117, USA *Corresponding author. Email: robert.whitch@ucom.edu ABSTRACT: It has been hypothesized that larvae of benthic marine invertebrates may reduce their risk of post-settlement competition by avoiding superior competitors during settlement. Few studies, however, have directly compared the levels of larval settlement close to and away from established competitors. We conducted experiments in the New England subtidal to determine whether larvae of fouling organisms would avoid substrata (100 cm2 PVC panels) with established adult colonies of the tunicates Botryllus schlosseri, Botrylloides violaceus, and Diplosoma listerianum compared to control substrata without tunicates. After panels had been exposed for 1 wk in the field, we assessed larval settlement on the entire surface of panels and within 1 cm of established tunicate colonies. We also monitored the fate of larvae that settled near established tunicates to determine if different tunicate species posed different risks of overgrowth to newly settled juveniles. Pair-wise comparisons revealed only 1 significant difference (out of 48 total analyses) when we examined levels of settlement on panels with tunicates relative to bare controls. We also found no significant differences in the number of settlers overgrown by different tunicate species. Thus, our results suggest that invertebrate larvae do not avoid settling near established dominant competitors (i.e. colonial tunicates). These results are in contrast to a previous study which had shown that larvae of competitively inferior species avoided settling near B. schlosseri. KEY WORDS: Ascidians · Competition · Cues · Larvae · Overgrowth · Settlement · Tunicates Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 280. Online publication date: October 14, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Harvesting Impacts and Invasion by an Alien Species Decrease Estimates of Black Coral Yield off Maui, Hawai'i

For over 40 yr, the black coral fishery in Hawai'i has been managed successfully. However, three new developments now threaten sustainability of the resource. First, harvesting pressure on increasingly smaller colonies of both species of commercial black coral (Antipathes dichotoma Pallas and Antipathes grandis Verrill) has increased. Since 1976, the biomass of black coral in the overall bed off Maui, Hawai'i, has decreased by about 25%. Second, at depths between 80 and 110 m off Maui an alien species, Carijoa riisei (Duchassaing & Michelotti), has overgrown large areas of the substratum as well as many adult colonies of both species of commercial black coral. This invasion may be contributing to a decrease in the recruitment of both species of black coral at shallower depths. Third, increasing sales of black coral jewelry in recent years is also placing more demand on the resource. Taken together, these trends suggest a need for more stringent regulations, including a larger size (height) limit, a reduction in the maximum sustained yield, and possible reassessment of the economics of the fishery. Adoption of these or other measures would help to extend and ensure continued sustainability of the black coral fishery in Hawai'i and long-term conservation of the resource.

Coral mortality and interaction with algae in relation to sedimentation

The impact of sedimentation on coral–algal interactions was studied by monitoring tissue mortality and radial growth in two coral species, Colpophyllia natans and Siderastrea siderea, over a continuum of sediment input intensities. This study sets out to investigate (1) whether sedimentation can facilitate algal overgrowth of corals and (2) whether this was a significant cause of coral mortality. Over a 15-month period, 198 coral colonies were tagged and photographed at six sites along two replicate gradients of sediment input, spanning high inputs near river mouths to low inputs at exposed headlands. Photographs were taken so that they covered the interface between colonies and algae. Radial growth was measured along colony edges in contact with algae and unaffected by tissue loss from causes other than competition with algae. To establish whether algal overgrowth was a significant cause of coral mortality, tissue mortality on the colony surface area visible in the photographs was related to different causes, including sediment smothering, disease, and algal overgrowth. Radial growth became negative with increasing proximity to river mouths in C. natans and remained negative or close to zero throughout the gradients in S. siderea, overall suggesting that sedimentation can facilitate algal overgrowth on corals. However, the analysis of tissue mortality revealed that algal overgrowth was a relatively minor cause of tissue loss. In contrast, the most important cause of coral mortality in relation to sedimentation was from sediment smothering, probably during intense episodes of deposition associated with heavy rainfall. We conclude that sedimentation may lead to reef degradation by causing coral mortality through sediment smothering and burial, and then by suppressing the regrowth of surviving adult colonies through increased competition with algae.

363 Toxicity effects of vitamin A on the liver and bone in rats

Swimming and nonswimming tadpole larvae of the ascidian Ecteinascidia turbinata Herdman were followed in situ by divers to determine whether swimming affects larval dispersal. Swimming affected neither dispersal direction nor time spent in the water column. However, the dispersal rates and distances of swimming larvae were significantly lower than those of nonswimming larvae.Potential paths of larval dispersal were modeled with subsurface drogues. Movements of both swimming and nonswimming larvae differed consistently from surface flo w direction in these shallow (1.0–1.5 m) waters, indicating that caution should be used in modeling larval dispersal with drogues, particularly when larvae do not consistently remain in surface waters.In our south Florida study site, E. turbinata colonies were present only on unanchored mangrove prop roots and survival of colonies transplanted into surroundings habitats was very low. Drogue paths demonstrated that currents could potentially carry E. turbinata between mangrove islands, but behavior of the larvae suggests that dispersal is generally very localized with larvae settling near colonies from which they were released. This behavior differs dramatically from that reported for E. turbinata larvae in a more homogeneous habitat in the northern Gulf of Mexico.The short-distance dispersal of swimming tadpole larvae inthis study may represnt a local adaptation to favor recruitment near parental habitats and to prevent advection to inappropriate sites. Long-distance exchange between isolated islands probably occurs through rafting of adult colonies on fragmented mangrove roots rather than through larval dispersal.

Influence of UV radiation on the survival of larvae from broadcast-spawning reef corals

Effects of ambient ultraviolet light on the survivorship of eggs and planulae larvae was investigated for three species of broadcast-spawning reef corals, Acropora palmata, Montastraea annularis, and M. franksi. Eggs and larvae from these corals contain high concentrations of lipids (60–70% by weight) and float in surface waters for 3–4 days following spawning. Larvae originating from colonies living at deeper sites on the reef exhibited significantly lower survivorship than conspecifics originating from parents in shallow water when experimentally exposed for up to 4 days to ambient surface levels of ultraviolet radiation (UVR). Concentrations of the UVR-protective compounds correlated positively with survival and matched concentrations found in parent colonies, implying that higher concentrations of ultraviolet B protective compounds are responsible for greater survival of eggs and larvae from shallow compared to deeper-dwelling parents. Ultraviolet B appears to be responsible for most of the observed differences in larval survivorship with ultraviolet A playing a minor or insignificant role. Data presented here indicate that coral recruits on Caribbean reefs and elsewhere may originate primarily from adult colonies dwelling in shallow water.

Larval dispersal, recruitment, and adult distribution of the brooding stony octocoral Heliopora coerulea on Ishigaki Island, southwest Japan

Larval dispersal and recruitment are important factors that determine the distribution of adult corals. The relationships between larval dispersal, recruitment, and the adult distribution of the blue octocoral, Heliopora coerulea, were investigated on Shiraho Reef, Ishigaki Island, southwest Japan. Heliopora coerulea is a surface brooder that releases planulae in June or July on Shiraho Reef. We observed planulae between 1998 and 2000 and found that they did not swim actively; instead, they crawled into their settlement positions after becoming grounded on the substratum. Planulae occurred throughout the water column and were dispersed by tidal and wind-driven currents around the parent population on the reef flat. Recruitment was observed only within 350 m of the parent populations, including areas between the branches of the adult colony. The planulae of H. coerulea had a narrow dispersal range as a result of their mostly benthic, shorter larval duration, and the influence of weaker currents. Thus, the dispersal distance of larvae is determined by their position in the water column, the currents that deliver the larvae, and the competency period of the larvae. The narrow dispersal range of H. coerulea was consistent with recruitment of sexually derived larvae onto their natal reef.

Substrate distribution in fungus chambers in nests of Atta bisphaerica Forel, 1908 (Hym., Formicidae)

Abstract: Substrate distribution was studied in three adult colonies of the leaf‐cutting ant Atta bisphaerica Forel, 1908 using dye. Some supply holes were mapped using baits made from small plastic straws impregnated with citric pulp. Two holes, equidistant from one another, were then selected in each nest. The colonies were excavated completely 24 h after bait placement. During excavation, fungus chambers were checked for dye. We observed that the dyed baits were distributed in all sectors and at all depths regardless of where the baits had been placed. This supported the hypothesis that toxic baits placed in a single supply hole are uniformly distributed throughout the colony.

Pup Shoving by Adult Naked Mole‐Rats

AbstractAdult naked mole‐rats (Heterocephalus glaber) characteristically perform an unusual behavior toward young: they shove small pups frequently and vigorously around the nest. We studied 15 litters in five captive colonies to quantify which adults shove pups, changes in shoving frequencies as pups develop, how external disturbances affect pup‐shoving frequencies, and behavior of juveniles that were not shoved as pups. In all litters and colonies the breeding female shoved pups significantly more often than any other individual. Breeding females also shoved adult colony mates, but at far lower rates than they shoved pups. Breeding males shoved pups about half as often as did breeding females. Together, the parents shoved pups ten times more often than did nonbreeders. Frequencies of pup shoving peaked when pups were 3–4 wk old, roughly coincident with weaning. When colonies were disturbed experimentally, frequencies of pup shoving increased dramatically, whereas rates at which nonbreeding adults were shoved decreased sharply. We separated four newly‐weaned litters and raised half the pups apart from their colony. When these litters were reunited 4–9 wk later, the unshoved (experimental) pups were the same size as the frequently shoved (control) pups, but the unshoved pups were significantly less likely to flee from a disturbance. Shoving of small pups encourages them to flee from danger, and also may enforce weaning.

Extreme genetic differences between queens and workers in hybridizing Pogonomyrmex harvester ants.

The process of reproductive caste determination in eusocial insect colonies is generally understood to be mediated by environmental, rather than genetic factors. We present data demonstrating unexpected genetic differences between reproductive castes in a variant of the rough harvester ant, Pogonomyrmex rugosus var. fuscatus. Across multiple loci, queens were consistently more homozygous than expected, while workers were more heterozygous. Adult colony queens were divided into two highly divergent genetic groups, indicating the presence of two cryptic species, rather than a single population. The observed genetic differences between castes reflect differential representation of heterospecific and conspecific patrilines in these offspring groups. All workers were hybrids; by contrast, winged queens were nearly all pure-species. The complete lack of pure-species workers indicates a loss of worker potential in pure-species female offspring. Hybrids appear to be bipotential, but do not normally develop into reproductives because they are displaced by pure-species females in the reproductive pool. Genetic differences between reproductive castes are expected to be rare in non-hybridizing populations, but within hybrid zones they may be evolutionarily stable and thus much more likely to occur.

Ecological variation across a transition in colony-founding behavior in the ant Messor pergandei

A number of hypotheses have been proposed to explain the evolution of group colony foundation (pleometrosis) in ants, but evaluating their importance under natural conditions is difficult. The desert seed-harvester ant, Messor pergandei, shows regional variation in the incidence of pleometrosis. I investigated whether there are ecological differences between the two regions that may explain the observed behavioral divergence. Pleometrosis was significantly associated with reduced precipitation, lower vegetation biomass, and lower adult colony density. These differences are consistent with the hypothesis that additional worker production in group colonies increases foraging success rather than competitive ability. The data also suggest an additional hypothesis, desiccation resistance, that should be explored. Annual variability within regions was high and far exceeded the magnitude of the differences seen between regions. Future laboratory and field experiments should take such variability into account.

Recruiting juvenile damselfish: the process of recruiting into adult colonies in the damselfish Stegastes nigricans

Juveniles of Stegastes nigricans occur in adult colonies, solitarily, and occasionally in juvenile colonies. We concentrated on solitary juveniles and those in adult colonies. We examined the costs and benefits of different settlement strategies, quantified the territory requirements of adults, and investigated the process of how juveniles make the transition to adult territorial fish. An adequate adult territory lies next to those of other adults, is proportional in area to the size of the adult, and contains a refuge tunnel whose entrance is sufficiently large. Compared with solitary juveniles, those <4 cm total length inhabiting adult colonies experienced reduced heterospecific competition for algal food and consequently benefited from a greater density of algae. A cost of recruiting into an adult colony, however, was increased attacks by adults. Juveniles that settled in adult colonies avoided attacks by retreating into small holes inaccessible to adults. As juveniles in adult colonies grew, they were chased less often by adults, whereas they themselves chased adults and heterospecific fish more often. Because territory size correlated with fish size in adult colonies, its area had to expand as the young fish grew, and that expansion was done at the expense of neighbors. Obtaining the space needed by an adult may be possible only when the juvenile settles directly into an adult colony. Juveniles that first settle down solitarily, or in juvenile colonies, may later attempt to enter adult colonies. However, because they do so as larger juveniles, they would have difficulty insinuating themselves into small refuges, which is essential for retreat from the adults.