Coexistence of congeneric spiny lobsters on coral reefs: differential use of shelter resources and vulnerability to predators

The notion, previously generated from laboratory experiments, that the local coexistence of spiny lobsters Panulirus guttatus and Panulirus argus on Caribbean reefs may be promoted by a differential use of shelter resources and/or vulnerability to predators was explored in a coral reef in Mexico. Multiple regressions with data collected on 11 occasions on fixed back-reef and fore-reef sites suggested that the densities of the congener, other crevice-dwellers, and predators did not significantly affect the density of P. argus in either reef zone, or of P. guttatus on the back-reef, where coexistence of both lobster species was greatest. In contrast, there was a significant negative relationship between predators and the density of P. guttatus on the fore-reef, where this species was dominant. Congeneric cohabitation in dens was less than expected by chance, but this pattern may reflect a differential use of shelter resources rather than interspecific competition. P. guttatus was more prevalent in dens over the middle and upper third of the reef profile, and P. argus over the lower and middle third of the reef profile. Whether individuals cohabited with conspecifics, congeners, or resided solitarily, P. guttatus was more prevalent at the walls and/or ceiling and P. argus on the floor of dens. This differential use of shelter resources may be related to the differential vulnerability to predators, which may have promoted local coexistence of these congeners in reef habitats.     

Enhancement of juvenile Caribbean spiny lobsters: an evaluation of changes in multiple response variables with the addition of large artificial shelters

Shortage of natural crevice shelters may produce population bottlenecks in juvenile Caribbean spiny lobsters (Panulirus argus), a socially gregarious species. We conducted a field experiment to test enhancement of a local population of juvenile P. argus with the addition of artificial shelters (“casitas”) that mimic large crevices (1.1 m² in surface area and 3.8 cm in height). Changes in density and biomass of juvenile lobsters 15–50 mm carapace length (CL) were assessed with a multiple before-after control-impact (MBACI) analysis. Separate analyses were also conducted on small (15–35 mm CL) and large (35.1–50 mm CL) juveniles to assess size-related effects. First, we carried out 13 lobster surveys on nine fixed 1-ha sites over a shallow reef lagoon (“before” period). Then, we deployed ten casitas in each of five sites and left four sites as controls, and conducted 22 further surveys (“after” period). Deployment of casitas resulted in a sixfold increase in juvenile density (76% contributed by small and 24% by large juveniles) and a sevenfold increase in biomass (40 and 60%, respectively). Capture–recapture results revealed that enhancement was achieved not by promoting individual growth but by increasing survival, persistence, and foraging ranges of small and large juveniles. Casitas both mitigated shortage of natural shelter and increased sociality, allowing for cohabitation of smaller, more vulnerable juveniles with larger conspecifics that have greater defensive abilities. Casitas may help enhance local populations of juvenile P. argus in Caribbean seagrass habitats, typically poor in natural crevice shelters. The use of MBACI and the simultaneous assessment of multiple interrelated response variables may be a powerful analytical approach to test shelter limitation in other species and to examine the function of structural habitat in other systems.     

Rosette-type tegumental glands associated with aesthetasc sensilla in the olfactory organ of the Caribbean spiny lobster, Panulirus argus

The lateral antennular flagellum of decapod crustaceans bears unique olfactory sensilla, namely the aesthetascs, and other sensilla types. In this study, we identify a new major tissue in the lateral flagellum of the Caribbean spiny lobster, Panulirus argus, namely “aesthetasc tegumental glands” (ATGs), based on immunostaining with antibodies against CUB serine protease (Csp), in situ hybridization with csp-specific probes, labeling with the F-actin marker phalloidin, labeling with the nuclear marker Hoechst 33258, and staining with methylene blue. Each ATG has 12–20 secretory cells arranged in a rosette. Each secretory cell has a Csp-immunoreactive basal portion and an apical portion containing granular material (metachromatic staining indicative of acid mucopolysaccharides). At the center of each secretory rosette is a phalloidin-positive common locus that gives rise to a main drainage duct projecting toward the cuticle. Scanning electron and light microscopy show that thin ducts traverse the cuticle and connect to “peg pores” proximal to the bases of the aesthetascs, with 3.4 peg pores per aesthetasc. Since the number of common loci is correlated with the number of peg pores, we conclude that each pore represents the outlet of one ATG, and that the secretions are released from them. We conclude further that ATGs and aesthetascs are functionally linked. We hypothesize that ATG secretions have antifouling and/or friction-reducing properties, and that they are spread over the surface of the aesthetascs by antennular grooming. A review of the literature suggests that ATGs are common in decapod crustacean antennules, and that rosette glands and grooming might be functionally coupled in other body areas.This study was supported by NSF IBN 0077474 and NIH DC00312.     

The hypervariable domain of the mitochondrial control region in Atlantic spiny lobsters and its potential as a marker for investigating phylogeographic structuring

Atlantic spiny lobsters support major fisheries in northeastern Brazilian waters and in the Caribbean Sea. To avoid reduction in diversity and elimination of distinct stocks, understanding their population dynamics, including structuring of populations and genetic diversity, is critical. We here explore the potential of using the hypervariable domain in the control region of the mitochondrial DNA as a genetic marker to characterize population subdivision in spiny lobsters, using Panulirus argus as the species model. The primers designed on the neighboring conserved genes have amplified the entire control region (approx. 780 bases) of P. argus and other closely related species. Average nucleotide and haplotype diversity within P. argus were found to be high, and population structuring was hypothesized. The data suggest a division of P. argus into genetically different phylogeographic groups. The hypervariable domain seems to be useful for determining genetic differentiation of geographically distinct stocks of P. argus and other Atlantic spiny lobsters.     

Ecto-ATPase/phosphatase activity in the olfactory sensilla of the spiny lobster,Panulirus argus: localization and characterization

Summary Electrophysiological studies have shown that the olfactory organ (antennule) of the spiny lobster, Panulirus argus, has chemoreceptors that are selectively excited by adenine nucleotides in seawater. Biochemical studies have revealed that these same nucleotides can be rapidly dephosphorylated by ectoenzymes associated with the olfactory sensilla (aesthetascs). In this study the distribution of ecto-ATPase/phosphatase activity within aesthetascs was determined cytochemically and the nature of the adenine-nucleotide dephosphorylating activity was dissected biochemically. Cytochemically, the distribution of ATP-dephosphorylating activity was similar to that shown previously for AMP and -glycerol phosphate; i.e., cerium phosphate reaction product was specifically localized to the transitional zone where the sensory dendrites develop cilia and branch to form the outer dendritic segments. Unlike the dephosphorylation of AMP and -glycerol phosphate, Mg²⁺ or Ca²⁺ was required for ecto-ATPase/phosphatase activity. Biochemical measures of both AMP-and ATP-dephosphorylating activity within aesthetascs corroborated the cytochemical evidence that these activities are localized to the transitional zone. A major portion of the AMP dephosphorylation (about 67%) derives from nonspecific alkaline phosphatase activity that is insensitive to levamisole and L-bromotetramisole. In contrast, nonspecific phosphatase activity accounted for a much smaller part of the ATP dephosphorylation (about 15%). Ectoenzymatic activity in the transitional zone may be an important means of removing excitatory/inhibitory nucleotides from this region.Abbreviations ADP Adenosine 5-diphosphate - AMP adenosine 5-monophosphate - AMPCP , -methylene ADP - ASW artificial seawater - ATP adenosine 5-triphosphate - -GP -glycerol phosphate - EM electron microscopy     

Spatial genetic patterns in lagoonal, reef-slope and island populations of the coral Platygyra daedalea in Kenya and Tanzania

Considering the rapid degradation of coral reefs, it is becoming increasingly important to assess factors such as levels of intraspecific genetic diversity and degree of connectivity between populations and reefs. In this study, five DNA microsatellite markers were used to infer migration patterns and levels of genetic diversity in ten populations of the faviid coral Platygyra daedalea along the coast of East Africa. Populations from reef-slopes and offshore islands had significantly greater genetic diversity, measured as expected heterozygosity and allelic richness than those of inshore lagoonal reefs. A combination of F-statistics and individual assignment tests indicated moderate to high levels of gene flow among lagoonal populations, and less migration between lagoonal sites and the reef-slope and island sites. These results suggest that reef-slope and island reefs could be important reservoirs of genetic diversity for this coral species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Identification and characterization of microsatellite loci in the blue coral <Emphasis Type="Italic">Heliopora </Emphasis><Emphasis Type="Italic">coerulea</Emphasis> (Alcynonaria: Coenothecalia)

We isolated 11 polymorphic microsatellites from blue coral (Heliopora coerulea), whose conservation and management are of great concern. The number of alleles ranged from 3 to 20 with an average of 5.5, and the observed and expected heterozygosities ranged from 0.115 to 0.833 and from 0.371 to 0.915, respectively. These loci are useful for conservation genetics in H. coerulea populations.     

Prevalence, intensity and aggregation of intestinal parasites in mountain hares and their potential impact on population dynamics

Mountain hare Lepus timidus populations show unstable dynamics and since hares carry a significant helminth infection and host-parasite interactions are known to be destabilising, they have been proposed as a possible causal mechanism for the observed instability. We assessed the prevalence, intensity of infection and aggregation of the helminth parasites Graphidium strigosum and Trichostrongylus retortaeformis recovered from 589 mountain hares culled from 30 Scottish sporting estates in 1999 and 2000. Graphidium strigosum showed low prevalence and intensity of infection and was highly aggregated. In contrast, T. retortaeformis showed high prevalence and intensity of infection and a low degree of aggregation. Differences in body condition of the hares were best explained by a model including sex and month of collection and interaction terms for sex-month and intensity of infection of T. retortaeformis-month. The low degree of aggregation of T. retortaeformis and the significant negative effect of intensity of infection on body condition are in accordance with the hypothesis that the host-parasite interaction is the causative destabilising mechanism for mountain hare dynamics.     

江苏海门蛎岈山牡蛎礁恢复工程的生态评估

江苏海门蛎岈山牡蛎礁是我国目前现存的面积最大的潮间带活体牡蛎礁,但由于人类活动干扰及泥沙淤积等原因,该自然牡蛎礁面积不断缩小,影响着该牡蛎礁的生态功能与保护管理。于2013—2014年开展了首期江苏海门蛎岈山牡蛎礁恢复工程,基于生态监测结果评估该牡蛎礁恢复工程的生态效果。多层礁体上活体牡蛎丰度显著高于单层礁体(P0.05);随着礁体的发育,恢复礁体上牡蛎丰度显著下降(P0.05)。非参数Kruskal-Wallis检验结果显示,在两个生活周期内(2013-09—2013-11,2014-03—2014-05)牡蛎均呈现快递的生长(Q=10.519,Q=6.527,P0.05),而在越冬期内(2013-11—2014-03)牡蛎几乎停止了生长(Q=0.35,P0.05)。随着礁体的发育,恢复牡蛎礁上大型底栖动物群落的物种丰度并没有增加,但其平均总密度和总生物量均呈现显著性的增长(P0.05);礁体构建后1a时恢复牡蛎礁中大型底栖动物的平均总密度和生物量均接近于自然牡蛎礁(P0.05),但显著高于未恢复区(P0.05);恢复牡蛎礁与自然牡蛎礁具有显著不同的大型底栖动物群落(ANOSIM,P=0.001)。研究结果表明该牡蛎礁恢复工程取得初步成功。     

Phylogeography of colour polymorphism in the coral reef fish Pseudochromis fuscus, from Papua New Guinea and the Great Barrier Reef

Body colour has played a significant role in the evolution of coral reef fishes, but the phylogenetic level at which colour variation is expressed and the evolutionary processes driving the development and persistence of different colour patterns are often poorly understood. The aim of this study was to examine the genetic relationships between multiple colour morphs of Pseudochromis fuscus (family Pseudochromidae), both within and among geographic locations. Pseudochromis fuscus is currently described as a single species, but exhibits at least six discrete colour morphs throughout its range. In this study, P. fuscus from Papua New Guinea (PNG) and the Great Barrier Reef (GBR), Australia, formed three genetically distinct clades based on mitochondrial DNA (control region) sequence data: (1) yellow and brown morphs from the GBR and southern PNG, as well as an orange morph from southern PNG; (2) a pink morph from southern PNG; and (3) all three morphs (pink, orange and grey) found in Kimbe Bay, northern PNG. The three groups showed deep levels of divergence (d=14.6–25.4%), suggesting that P. fuscus is a complex of polychromatic species, rather than a single widespread species with many different colour morphs. Population genetic analyses indicate that the three clades have experienced unique evolutionary histories, possibly from differential effects of sea level fluctuations, barriers to gene flow and historical biogeography.     

Remote video bioassays reveal the potential feeding impact of the rabbitfish Siganus canaliculatus (f: Siganidae) on an inner-shelf reef of the Great Barrier Reef

Herbivores are widely acknowledged as key elements maintaining the health and resilience of terrestrial and aquatic ecosystems. Understanding and quantifying the impact of herbivores in ecosystems are fundamental to our ability to manage these systems. The traditional method of quantifying the impact of herbivorous fishes on coral reefs has been to use transplanted pieces of seagrass or algae as “bioassays”. However, these experiments leave a key question unanswered, namely: Which species are responsible for the impact being quantified? This study revisits the use of bioassays and tested the assumption that the visual abundance of species reflects their role in the removal of assay material. Using remote video cameras to film removal of assay material on an inner-shelf reef of the Great Barrier Reef, the species responsible for assay-based herbivory were identified. The video footage revealed that Siganus canaliculatus, a species not previously recorded at the study site, was primarily responsible for removal of macroalgal biomass. The average percentage decrease in thallus length of whole plants of Sargassum at the reef crest was 54 ± 8.9% (mean ± SE), and 50.4 ± 9.8% for individually presented Sargassum strands (for a 4.5-h deployment). Of the 14,656 bites taken from Sargassum plants and strands across all reef zones, nearly half (6,784 bites or 46%) were taken by S. canaliculatus, with the majority of the remainder attributable to Siganus doliatus. However, multiple regression analysis demonstrated that only the bites of S. canaliculatus were removing macroalgal biomass. The results indicate that, even with detailed observations, the species of herbivore that may be responsible for maintaining benthic community structure can go unnoticed. Some of our fundamental ideas of the relative importance of individual species in ecosystem processes may be in need of re-evaluation.     

The skeletal isotopic composition as an indicator of ecological and physiological plasticity in the coral genus<Emphasis Type="Italic"> Madracis</Emphasis>

Three species of the reef coral genus Madracis display skeletal isotopic characteristics that relate to depth, colony topography, and consequently to coral physiology. The joint interpretation of skeletal ¹³C and ¹⁸O provides information on the ecological plasticity and adaptation to depth of a coral species. Isotopic results are most easily understood in terms of kinetic effects, which reduce both ¹⁸O and ¹³C below isotopic equilibrium values, and metabolic effects, which only influence the skeletal ¹³C. Madracis mirabilis is adapted to depths shallower than 20 m, and shows the greatest range in kinetic effects and the strongest metabolic ¹³C enrichments caused by symbiont photosynthesis. Madracis formosa lives deeper than 40 m, and shows a reduced range of kinetic effects and relatively weak metabolic ¹³C enrichments. Madracis pharensis inhabits depths from 5 to >60 m, and does not attain the strength of kinetic effects of either of the other two species, apparently because it is not quite as well adapted to rapid growth at either extreme.     

Coexistence of NADPH-diaphorase and vasoactive intestinal polypeptide in the enteric nervous system of the Atlantic cod (Gadus morhua) and the spiny dogfish (Squalus acanthias)

The distribution of NADPH (nicotinamide adenine dinucleotide phosphate)-diaphorase in nerve cells in the gastrointestinal tract has been investigated and compared in three fish species representing different evolutionary branches. In mammals, NADPH-diphorase is identical to nitric oxide synthase (NOS) and can, in the presence of NADPH, reduce the dye nitroblue tetrazolium, resulting in a blue product. Using this method, we have found numerous NADPH-diaphorase-containing nerve cells in the myenteric plexus of the Atlantic cod (Gadus morhua) and the spiny dogfish (Squalus acanthias) but none in the hagfish (Myxine glutinosa). In the cod, nerve fibres were sparsely stained, whereas in the dogfish, they formed a dense pattern of fibre bundles. Double-staining for NADPH-diaphorase and the neuropolypeptides VIP (vasoactive intestinal polypeptide) and PACAP (pituitary adenylate cyclase activating peptide) revealed three separate populations designated VIP/NADPH, VIP/- and NADPH/-. The majority but not all of the NADPH-diaphorase-positive cells also showed VIP or PACAP immunoreactivity and vice versa. The presence of NADPH-diaphorase in neurons and the distribution of these neurons in the gastrointestinal tract of the two species indicate a physiological role for nitric oxide in the control of gut motility.     

Foraging behavior and diet composition of Trimma caudomaculata and Trimma caesiura (Gobiidae) on coral reefs in Okinawa, Japan

The feeding habits of two small gobies, Trimma caudomaculata and T. caesiura, were surveyed on coral reefs in Okinawa, Japan. Both species actively exhibited foraging attempts beneath overhanging reef structures during the daytime, and fed on small animals, mainly copepods. Trimma caudomaculata formed feeding schools in water columns to swallow mainly Calanoida and Harpacticoida. Trimma caesiura stayed by themselves on the reef substratum and captured mainly Harpacticoida by taking short jumps into the water column. Diet compositions of these congeneric gobies may reflect differences in their foraging behaviors and use of microhabitats.     

Biases in the estimation of spatial egg aggregation and association based on emergence data

Spatial aggregation and association of conspecific and allospecific eggs over resource patches have often been estimated based on emergence data. However, intra-specific competition reduces the number of emergents of conspecifics, and inter-specific competition reduces the number of emergents of allospecifics, causing biases in the estimation of spatial distribution of eggs using emergence data. The present study investigated, by laboratory experiments using drosophilids and simulation models, how the use of emergence data causes such biases. In the laboratory experiments, females were allowed to oviposit over resource patches, and spatial aggregation and association of eggs were examined. The number of emergents from each resource patch was then estimated from the density-survival relationship, and spatial aggregation and association of emerging adults thus estimated were compared with those of eggs. In the simulation models, the spatial distributions of adults emerging from eggs that varied in their degree of spatial aggregation were evaluated under different intensities of intra- and/or inter-specific competition. Both laboratory experiments and simulations indicate that the use of emergence data always causes an underestimation of spatial aggregation and association of eggs. Relaxation of intra- and inter-specific competition by addition of extra resources would improve the estimation of spatial egg distribution based on emergence data.     

Spatial differences in patterns of modification: selection on hairy in Drosophila melanogaster wings

Artificial selection was carried out for over 45 generations to enhance and suppress expression of the mutation hairy on the Drosophila melanogaster wing. Whole chromosome mapping of X‐linked and autosomal modifiers of sense organ number displayed regional differences in magnitude and direction of their effects. Regional specificity of modifier effects was also seen in some interchromosomal interactions. Scanning electron microscopy allowed precise measurement of sense organ size and position along the L3 longitudinal wing vein. Sense organ size varied in a predictable fashion along the proximal–distal axis, and the dorsal pattern differed from the ventral pattern. The high and low selection lines differed most in the proximal portion of the L3 vein. Extra sense organs in the High line were often associated with vein fragments at locations predicted from ancestral vein patterns. Thus, regional specificity of polygenic or quantitative trait locus modifier effects was identified in several different parts of the wing. This revised version was published online in July 2006 with corrections to the Cover Date.     

The influence of colony size and coral health on the occupation of coral-associated gobies (Pisces: Gobiidae)

Fishes of the genus Gobiodon are habitat specialists by their association with Acropora corals. Little is known about the parameters that define host coral quality for these fishes, in particular their breeding pairs. Data were collected in the northern Red Sea using 10 × 1-m belt transects in different reefs and zones. Gobiid density was highly correlated with coral density over all sites and zones, and the more specialized goby species preferred coral species that are less vulnerable to environmental stress. Moreover, the occupation rate of corals by goby breeding pairs significantly increased with colony size and decreased with partial mortality of colonies. Logistic regression showed that both coral size (being most important) and partial mortality are key factors influencing the occupation by breeding pairs. This study provides the first evidence that breeding pairs of coral-associated gobiids have more advanced habitat requirements than con-specifics in other social states. As coral reefs are threatened worldwide and habitat loss and degradation increase, this information will help predict the potential effects on those reef fishes obligatorily associated with live corals.     

Comparison between community structures of fishes in <Emphasis Type="Italic">Enhalus acoroides</Emphasis>- and <Emphasis Type="Italic">Thalassia hemprichii</Emphasis>-dominated seagrass beds on fringing coral reefs in the Ryukyu Islands,Japan

To clarify differences in community structures and habitat utilization patterns of fishes in Enhalus acoroides- and Thalassia hemprichii-dominated seagrass beds on fringing coral reefs, visual censuses were conducted at Iriomote and Ishigaki islands, southern Japan. The numbers of fish species and individuals were significantly higher in the E. acoroides bed than in the T. hemprichii bed, although the 15 most dominant fishes in each seagrass bed were similar. Cluster and ordination analyses based on the number of individuals of each fish species also demonstrated that fish community structures were similar in the two seagrass beds. Species and individual numbers of coral reef fishes which utilized the seagrass beds numbered less than about 15% of whole coral reef fish numbers, although they comprised about half of the seagrass bed fishes. Of the 15 most dominant species, 5 occurred only in the two seagrass beds, including seagrass feeders. Ten other species were reef species, their habitat utilization patterns not differing greatly between the two seagrass beds. Some reef species, such as Lethrinus atkinsoni and L. obsoletus, showed ontogenetic habitat shifts with growth, from the seagrass beds to the coral areas. These results indicate that community structures and habitat utilization patterns of fishes were similar between E. acoroides- and T. hemprichii-dominated seagrass beds, whereas many coral reef fishes hardly utilized the seagrass beds.     

Colonization of vineyards by phytoseiid mites: their dispersal patterns in the plot and their fate

The effect of wind and woody margins on the dispersal and population dynamics of phytoseiid mites was studied in a vine plot for a period of two years. Mites were sampled in the plot and in the surrounding vegetation (crops and natural vegetation) in order to determine phytoseiid mite abundance. The surrounding vegetation was considered to be a reservoir of phytoseiids from where the vine plot could be invaded. Directional and non-directional soil and aerial traps were placed in the plot to determine predatory mite exchange between the two areas. Colonization of the plot occurred in two stages: first, mite migration into the plot, followed by their establishment. The two-year study partially clarified the first of these two stages. Kampimodromus aberrans was the main species caught in the aerial traps. Phytoseiid mite dispersal within the vine plot seemed to be affected by both wind (direction, intensity and regularity) and phytoseiid mite density in the woody margin. However, the woody margin had a large effect only over a short distance. Some observations pointed towards an effect of other reservoir areas but it was not possible to characterize these. The population density of the phytoseiid mites in the plot increased from 1996 to 1998, but these increases are much smaller than one would expect on the basis of the number of mites migrating by air in the plot. Moreover, blocks where most mites were trapped were not the blocks where densities of phytoseiid mites on vine leaves were the largest. It therefore seems likely that not all migrants were able to develop. Their settlement pattern was not determined and this could constitute a potential research focus for the future.     

Insect natural enemies of coffee green scales [Hemiptera: Coccidae] in Kenya and their potential for biological control ofCoccus celatus andC. viridis in Papua New Guinea

Coffee green scales,Coccus celatus De Lotto andC. viridis (Green), are major pests of coffee in Papua New Guinea (PNG). Surveys for insect natural enemies of coffee green scales were conducted in Kenya to find species suitable for introduction to PNG. Natural enemy communities in Kenya were found to be diverse, particularly those located in the central highlands where 3 primary parasitoids,Metaphycus stanleyi Compere,M. baruensis Noyes andDiversinervus stramineus Compere (Encyrtidae), were dominant onC. celatus andC. alpinus De Lotto. It is suggested that these 3 parasitoids may be potential biological control agents forC. celatus. Several insect predators were found associated withC. celatus in the central highlands but most were only common in ant-free scale populations. An aphelinid primary parasitoid,Coccophagus rusti Compere, was the only natural enemy ofC. viridis located. This species, however, could be of potential as a biological control agent, especially in view of its previous use in biological control against soft scales.