Habitats, abundance and diets of Muricacean gastropods at Aldabra Atoll

Twenty-three species of predatory Muricacean gastropods are common on the intertidal rocky shores of Aldabra Atoll. Species show a division of the habitat space by vertical zonation along the intertidal gradient, longitudinal zonation around an exposure gradient and by choice of substrate type. Co-occurring species usually overlap very little in size and this may indicate utilization of different parts of the habitat/food resource.
Most species of Thais, Purpura and Morula feed by drilling sedentary or semi-mobile prey and most suitable prey species are exploited. Species show a broad partitioning of the available food resources and overlap between species is usually low. Large species have generally more varied diets than small species. Size variation of some species around the Atoll may be attributed to differences in diet. Species of Drupa do not drill but feed upon eunicid, nereid and sipunculid worms and small Crustacea. Drupella cornus and two species of Coralliophilidae feed upon coral polyps.
The Muricacea occur together with other predatory gastropods, such as the Conidae, Mitridae and Buccinidae, but these families have generally different diets and largely independent food webs.
The Muricacea at Aldabra appear to have narrower habitat ranges than muricids in temperate areas.     

A partial food web involving predatory gastropods on a Pacific fringing reef

An analysis of the feeding habits of a diverse assemblage of predatory gastropods on a Guam fringing reef, shows that seven major prey categories are eaten, namely polychaetes, sipunculans, gastropods, bivalves, crustaceans, ophiuroids, and fish. The three largest feeding groups are the polychaete feeding guild which mainly consists of species of Conus, the gastropod guild dominated by species of the Muricidae and the sipunculan guild consisting mainly of the Mitridae. There is considerable dietary overlap between members of feeding guilds, but interaction between guilds is low and accounted for by the relatively few generalist species in the community.     

Geomorphology of the uplifted Pleistocene atoll at Henderson Island, Pitcairn Group

Henderson Island, in the Pitcairn Group, preserves a Pleistocene atoll physiography with the rim of the raised reef structure, supporting spur and groove topography, enclosing a central lagoon. Excellent preservation of coral reef communities occurs along the ancient atoll rim and within the central lagoon. The previously interpreted depositional nature of the fossil atoll structure is herein corroborated with geomorphologic and stratigraphic evidence from previously un-visited portions of the island. Stratigraphic and lateral facies relationships indicate a physiographic zonation which includes spur and grooves, outer reef flat, lagoon margin, and an interior lagoon with patch reefs. The in situ occurrence and zonation of reef coral communities around the periphery and within the interior of the island appear to reflect the original physiography of the atoll lagoon, with the most pronounced reef development on the SE side of the original atoll. Stratigraphic units which comprise the raised atoll lagoon structure represent different time intervals, so the atoll lagoon structure formed during various sea level fluctuations. The modern atolls of the Pitcairn Group, Oeno and Ducie, provide some comparisons (similarities and differences) with the fossil lagoon on top of Henderson Island.     

Optimal diet theory: behavior of a starved predatory snail

Summary The tenets of optimal foraging theory are used to contrast the behavior of the predatory snail Acantina spirata when feeding on the barnacles Balanus glandula and Chthamalus fissus under conditions of satiation and starvation. As predicted in optimal diet models, A. spirata is less selective (ratio of attack frequency on a prey species to number of individuals available) when the higher ranking prey has low abundance. When given a choice, starved snails attack both barnacle species equally, whereas satiated individuals preferentially attack B. glandula, the more profitable prey (ash-free dry weight of barnacles ingested per unit handling time). Under starvation conditions, equal attack frequency does not result in equal prey species consumption because Acanthina spirata is more successful at attacking C. fissus than B. glandula.The assumption of constant prey encounter rates in optimal diet models is not met when A. spirata goes from a state of satiation to starvation. The encounter rate on B. glandula is lowered due to a decrease in attack success. A loss of feeding skills in starved A. spirata is responsible for the greater difficulty snails have in gaining access through the opercular plates of B. glandula.Behavioral changes in A. spirata as snails pass from satiation to hunger translate into an energetic disadvantage during feeding for hungry snails for two reasons. First, higher prey handling times result in a decreased rate of biomass intake. Second, alteration in the relative attack frequency between barnacle species, combined with a decrease in attack success on the more profitable prey leads to more frequent ingestion of the less profitable prey.     

Temporal variability of settlement in Carapidae larvae at Rangiroa atoll

Carapidae (or pearlfish) are eel-like fishes living inside different invertebrates, such as holothurians, sea stars or bivalves. In some Polynesian areas where they live in sympatry, several species (Carapus homei, Carapus mourlani, Carapus boraborensis and Encheliophis gracilis) are able to inhabit the same host species. The heterospecific infestation rate is very rare, suggesting that the four species can compete for their hosts. Some differences in settlement period, breeding period and in pelagic larval duration (PLD) could allow better characterisation of the life history of each species. More than 700 larvae were collected during an entire year on the Rangiroa atoll (French Polynesia). Each species was identified; their settlement pattern was examined and their PLD was deduced from otolith (sagittae) increments. In the four collected species, the settlement pattern differed: C. homei and C. mourlani settle on the reef during the entire year, and show an asynchronous and diffuse breeding cycle. C. boraborensis and E. gracilis have a shorter settlement period which could be compatible with breeding synchronisation. As most reef fishes, Carapidae larvae mainly settle during moonless nights. Moreover, each species presents some plasticity, allowing it to settle on the reef under suitable conditions.     

The effect of a species-specific avoidance response to predatory starfish on the intertidal distribution of two gastropods

Summary The gastropodsAcmaea (Collisella) limatula andAcmaea (Notoacmea) scutum respond to water flowing over certain predatory starfish (i.e. to the scent of the starfish) by moving rapidly up a submerged, vertical surface. These limpets respond with upward movement to the scent ofPisaster ochraceus, Pisaster giganteus, Pycnopodia helianthoides, andLeptasterias aequalis. All of these starfish are predators on molluscs and at least occasionally inhabit the intertidal. In contrast, the limpets respond weakly or not at all to the scent ofPatiria miniata andPisaster brevispinus. Patiria is an omnivorous scavenger, andP. brevispinus is predaceous but strictly subtidal when it occurs on rocky shores. For the starfish tested, then, the limpets only give avoidance responses to starfish species naturally encountered as predators.The avoidance response ofA. limatula andA. scutum to predatory stafish can also be demonstrated in the field. When onePisaster ochraceus is placed beneath a population of limpets in the intertidal and confined so that contacts between the starfish and limpets are impossible, the limpet population is displaced significantly upward after one tidal cycle. In addition, the closer the limpets are to the starfish, the greater is their upward displacement.     

Differential vulnerability determines the diet of a slow-moving predatory stream insect

1. We investigated the diet and prey electivity of Rhyacophila obliterata, a slow‐moving invertebrate predator capable of hunting in high‐flow microhabitats, and quantified the components of the predation sequence of fifth‐instar larvae foraging on mobile (Baetis mayflies, Amphinemura stoneflies) versus semi‐sessile (larval blackflies) prey. 2. In the field, fifth‐instar Rhyacophila consistently took more larval blackflies than more mobile prey. In behavioural trials, the number of attacks by Rhyacophila differed significantly between prey types, mobile prey being attacked more often than blackflies. Capture success, by contrast, was highest for blackflies, whereas Amphinemura and Baetis were rarely captured. In mixed‐prey feeding trials, Rhyacophila showed strong preference for blackflies and equally strong avoidance of Amphinemura and Baetis. 3. For mobile prey, the risk of being captured by this sluggish predator is very low, so they can afford to be in close contact with it. Rhyacophila was almost unable to capture any other prey but blackflies, resulting in strong passive selection for blackflies. 4. Therefore, the diet of fifth‐instar Rhyacophila can be predicted from laboratory observations and prey behaviour is the major determinant of the diet of this invertebrate predator.     

Bacterial communities in predatory mites are associated with species and diet types

The symbiotic bacterial communities of phytophagous arthropods are affected by host species and feeding habits, but such effects have been poorly studied in natural enemies. Here, we investigated the entire bacterial microbiome of two species of predatory mites, Neoseiulus californicus and Neoseiulus barkeri, feeding on three types of diets (artificial diet, pollen and their natural prey, the spider mite Tetranychus urticae) by high-throughput sequencing of the 16S rRNA gene. We found that the bacterial diversity of predatory mites feeding on artificial diet was significantly different from pollen and spider mite feeding groups in both N. californicus and N. barkeri, while bacterial diversity also differed strikingly between the two species even when feeding on the same artificial diet. This finding suggests that the bacterial community of predatory mites is determined by both species and diet. Alphaproteobacteria and Gammaproteobacteria were the two dominant bacterial classes in both predatory mite species, except for N. californicus feeding on artificial diet. The bacterium Bosea sp. was detected in all samples as the core microbial species in predatory mites. Additionally, we discuss whether Bradyrhizobiaceae and Rhodobacteraceae bacteria could be used as probiotics in the artificial diet of N. californicus for better mass rearing.

     

Sharing, consumption, and patch choice on Ifaluk atoll

Anthropological tests of patch choice models from optimal foraging theory have primarily employed acquisition rates as the currency of the model. Where foragers share their returns, acquisition rates may not be similar to consumption rates and thus may not be an appropriate currency to use when modeling foraging decisions. Indeed, on Ifaluk Atoll the distribution patterns of fish vary by fishing method and location. Previous analyses of Ifaluk patch choice decisions suggested that if Ifaluk fishers are trying to maximize their production rates they should rarely torch fish for dogtoothed tuna. However, some men do spend considerable time and energy exploiting the dogtoothed tuna patch. To improve our understanding of the constraints and motivations influencing men’s decisions to exploit this patch, here I use per capita consumption rates as a currency, rather than production rates, to evaluate predictions generated from a patch choice model. Results indicate that although fish caught in other patches are more widely distributed than fish caught in the dogtoothed tuna patch, the consumption rates of torch fishers and their kin are still considerably lower than the consumption rates of men pursuing fish in other patches. Although these results are unable to explain why Ifaluk men exploit the dogtoothed tuna patch, an important explanatory hypothesis is eliminated.     

The shark assemblage at French Frigate Shoals atoll, Hawai'i: species composition, abundance and habitat use

Empirical data on the abundance and habitat preferences of coral reef top predators are needed to evaluate their ecological impacts and guide management decisions. We used longline surveys to quantify the shark assemblage at French Frigate Shoals (FFS) atoll from May to August 2009. Fishing effort consisted of 189 longline sets totaling 6,862 hook hours of soak time. A total of 221 sharks from 7 species were captured, among which Galapagos (Carcharhinus galapagensis, 36.2%), gray reef (Carcharhinus amblyrhynchos, 25.8%) and tiger (Galeocerdo cuvier, 20.4%) sharks were numerically dominant. A lack of blacktip reef sharks (Carcharhinus melanopterus) distinguished the FFS shark assemblage from those at many other atolls in the Indo-Pacific. Compared to prior underwater visual survey estimates, longline methods more accurately represented species abundance and composition for the majority of shark species. Sharks were significantly less abundant in the shallow lagoon than adjacent habitats. Recaptures of Galapagos sharks provided the first empirical estimate of population size for any Galapagos shark population. The overall recapture rate was 5.4%. Multiple closed population models were evaluated, with Chao M(h) ranking best in model performance and yielding a population estimate of 668 sharks with 95% confidence intervals ranging from 289-1720. Low shark abundance in the shallow lagoon habitats suggests removal of a small number of sharks from the immediate vicinity of lagoonal islets may reduce short-term predation on endangered monk seal (Monachus schauinslandi) pups, but considerable fishing effort would be required to catch even a small number of sharks. Additional data on long-term movements and habitat use of sharks at FFS are required to better assess the likely ecological impacts of shark culling.     

The influence of acclimation, endosymbionts and diet on the supercooling capacity of the predatory bug Macrolophus pygmaeus

The generalist predator Macrolophus pygmaeus Rambur (Hemiptera: Miridae) is a key biological control agent in European greenhouses. The influence of acclimation, infection with endosymbiotic bacteria and diet on the cold tolerance of the Mediterranean biocontrol population was assessed by determining the supercooling point, i.e. the temperature at which the insect’s body fluids freeze. This parameter provides a first indication of an insect’s establishment potential in a new region and of its possible geographical range. Allowing the predatory bugs to adapt to lower temperatures resulted in an increase in supercooling ability. Macrolophus pygmaeus bugs exposed to antibiotics in their artificial diet and hence cured from their infection with the endosymbiotic bacteria Wolbachia pipientis, Rickettsia bellii and R. limoniae were more tolerant to freezing than infected bugs. The diet of the predators also affected the freezing temperature of the body fluids. Predators fed an artificial diet based on egg yolk were less resistant to freezing than those fed Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. These findings illustrate that several factors may affect the cold hardiness of a biocontrol agent and may thus complicate the evaluation of its establishment potential in the framework of an environmental risk assessment.     

The conceptual and practical implications of interpreting diet breadth mechanistically in generalist predatory insects

Seasonal polyphenism in animal colour patterns indicates that temporal variation in selection pressures maintains phenotypic plasticity. Spring generation of the polyphenic European map butterfly Araschnia levana has an orange–black fritillary‐like pattern whilst individuals of the summer generation are black with white bands across the wings. What selects for the colour difference is unknown. Because predation is a major selection pressure for insect coloration, we first tested whether map butterfly coloration could have a warning function (i.e. whether the butterflies are unpalatable to birds). In a following field experiment with butterfly dummies we tested whether the spring form is better protected than the summer form from predators in the spring, and vice versa in the summer. The butterflies were palatable to birds (blue tits Cyanistes caeruleus) and in the field the spring and summer form dummies were attacked equally irrespective of season. Therefore, we found no evidence that the map butterfly is warning‐coloured or that seasonal polyphenism is an adaptation to avian predation. Because insect coloration has multiple functions and map butterfly coloration is linked to morphology, life history and development it is likely that the interplay of several selection pressures explains the evolution of colour polyphenism. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Habitats,stress, and evolutionary rates

Habitats of organisms are expressed as an interaction between stress intensity, magnitude of environmental fluctuations, and energy availability from resources. Under this model organisms should evolve broad biological properties defined by such physical characteristics. When energy is severely restricted under the continuing constant stress of adversity-selection, or in widely fluctuating and highly stressful environments, little evolutionary change is expected; relict species and ‘living fossils’ are the respective expectations. In rather stable abiotic environments where resources are limited habitat preferences may develop leading to specialization and ultimately adaptive radiations. On the other hand major new innovations are more likely in highly disturbed resource-rich habitats. Evidence from the living and fossil biota is presented which is consistent with these conclusions.     

Nocturnal swimming, aggregation at light traps, and mass spawning of scissurellid gastropods (Mollusca: Vetigastropoda)

Abstract. Thousands of minute scissurellid gastropods (Vetigastropoda: Scissurellidae) were observed and collected at floating light traps in Moorea, French Polynesia, where a mass spawning event occurred on November 11, 2002. More than 20,000 live snails were recovered from the traps, and epidemic spawning continued in the laboratory, where clouds of white sperm and red-orange eggs were broadcast into the water. No aggregations of this magnitude have been reported previously in vetigastropods, nor is the capacity for sustained swimming known from other vetigastropod taxa. Snails had emerged from a local benthic habitat of coral sand and swum through ≥2 m of water to reach the traps. Scanning electron micrographs of the ornate shells confirm the identity of the most abundant species as Scissurella spinosa , with lesser numbers of Sinezona plicata . Our observations indicate that scissurellids are not exclusively benthic and that they are not rare, even though they have seldom been collected and studied alive. Because little is known about the basic biology and anatomy of scissurellids and because their position within the basal Gastropoda is poorly resolved, we include information on the design and construction of inexpensive light traps to promote comparative investigation of other poorly known species.     

Effects of diet on development and reproduction of the predatory pentatomids Picromerus bidens and Podisus maculiventris

The effects of five diets (larvae of Galleria mellonella L., larvae of Spodoptera littoralis (Boisduval), eggs of Ephestia kuehniella Zeller, cysts of Artemia franciscana Kellogg and an artificial diet based on bovine meat) on development, survival and reproduction of two predatory stinkbugs, Picromerus bidens L. and Podisus maculiventris (Say), were studied in the laboratory. Both species successfully completed immature development on the foods offered, except for P. bidens on cysts of A. franciscana. Significant effects of diet on developmental duration were found in both species. Total developmental time from second instar to adult ranged from 25.0 to 41.5 days and from 18.7 to 46.0 days in P. bidens and P. maculiventris, respectively. Nymphal survival of P. maculiventris was superior to that of P. bidens on all diets tested. Nymphal survival of P. maculiventris was greater than 92% on all diets except on A. franciscana cysts, yielding only 50% survival to adulthood. Survival of P. bidens fed on eggs of E. kuehniella was higher than that of conspecifics fed on caterpillar prey or artificial diet (89% on flour moth eggs vs. 68 and 80% on G. mellonella and S. littoralis and only 50% on meat diet). Fresh weight of newly emerged females of both pentatomids was affected by the diet offered to the predators during their nymphal stage. Females of P. maculiventris produced viable eggs on all diets except on cysts of A. franciscana and had mean fecundities of 691, 436, 608 and 344 eggs per female on S. littoralis, G. mellonella, E. kuehniella eggs and the meat diet, respectively. Females of P. bidens laid eggs only on live prey with mean fecundities of 94 and 38 eggs per female on S. littoralis and G. mellonella, respectively. The results indicate a lower nutritional plasticity of P. bidens as compared with P. maculiventris. An erratum to this article can be found at     

Holocene growth of a mid-Pacific atoll: Tarawa,Kiribati

Cores from ten holes, drilled to a maximum depth of 30 m, on Tarawa atoll in the central Pacific have been utilised in a study of the Holocene development of the atoll. Four dominant lithologies, in descending order, are cay rock, unconsolidated sediment, corals and leached limestone. Petrographic and radiometric age analyses indicate that the Holocene reef has developed on a previous (last interglacial) reef; the latter shows the effects of both vadose and phreatic freshwater diagenesis. Hydrological investigations beneath the present islands indicate the presence of freshwater lenses up to 29 m thick; the modern lenses are unrelated to freshwater diagenetic imprints preserved within the limestones. Vertical accretion rates of 5–8 m/1000 years for the Holocene reef section on Tarawa are significantly higher than rates measured for other Pacific atolls. The dated coral sequences suggest a more rapid rate of sea level rise during the early Holocene, and a relatively earlier stabilisation of sea level than has been suggested previously.     

云南高黎贡山南段高山生境的鸟兽多样性

高山生态系统通常具有较高的生物多样性,分布着一些特有动植物类群。由于高山地区对环境变化较为敏感,因此该区域物种的分布及其保护问题备受关注。南北走向的高黎贡山地处全球生物多样性热点地区,但以往的调查多集中在中段,对南段的高山地区仍缺乏研究。因此,为了解该区域的鸟兽多样性本底、现状,以及大中型兽类和地栖鸟类的季节变化动态,本调查于2018年11月至2019年10月沿高黎贡山山脊海拔3 100 ~ 3 700 m区域布设红外相机进行监测。分别选择南斋公房、北斋公房和大脑子3个监测区域,有效相机工作日9 359台日,共调查记录到24种鸟类（3目11科）和19种兽类（5目14科）。其中,鸟兽物种相对多度较高的前3种依次为小熊猫（Ailurus fulgens）、毛冠鹿（Elaphodus cephalophus）和血雉（Ithaginis cruentus）。鸟兽物种数有明显的季节变化：冬季物种数少、秋季和夏季多,全年以8月最高;动物活动强度同样存在明显的季节变化和种间差异。鸟类和兽类的物种丰富度季节变化与活动强度变化,可能与动物沿海拔梯度的垂直迁移和高海拔食物资源的波动有关。将本次调查结果与中段调查数据比较,鸟类Beta多样性的周转大于嵌套,而兽类是嵌套大于周转,说明两地物种组成差异以鸟类为主。综合考虑,我们建议将动物垂直迁移和活动强度的季节变化纳入自然保护区管理和保护中,并实施高黎贡山高山生态系统的全境保护。     

四川老君山自然保护区不同生境鸟类多样性研究

2006年4~5月采用"点样带法"(point transects)对四川老君山自然保护区的鸟类物种组成和种群数量进行了调查,共记录到85种鸟类,分属7目22科。其中,国家级保护鸟类5种,我国特有种13种,优势种4种。把调查区域划分为3种生境:原始林、次生林和人工林,并对各生境鸟类群落的鸟类数量级、鸟类群落的物种多样性、鸟类群落间的相似性进行了比较分析,其结果表明:1)国家级保护鸟类在原始林中最多,次生林中最少;我国特有种则是次生林中最多,人工林中最少。2)鸟类群落Shannon-Wiener物种多样性指数原始林最高,人工林最低。3)原始林和次生林之间的B ray-Curtis相似性指数最高,原始林和人工林之间相似性指数最低。     

Habitat preferences and diet in the predatory Coccinellidae (Coleoptera): an evolutionary perspective

Coccinellids (ladybird beetles) exhibit considerable diversity in habitat and dietary preference and specificity. This is evident even when comparing species within some coccinellid genera. Resource limitation and competition are suggested as of greatest importance in the evolution of coccinellid habitat preferences. Dietary and habitat specialization has probably occurred in some lineages within broader preferences possessed by generalist ancestors, to avoid the costs associated with migration between habitats and prey switching. Feeding in atypical habitats, on alternative food, when optimal prey are scarce, is likely to have been of great importance in facilitating evolutionary shifts to novel diets and habitats. The broad host ranges of many coccinellid parasitoids and observed interspecific differences in parasitoid prevalence resulting from physiological differences between coccinellid species argue that enemy free space has been of limited importance in habitat and prey shifts in this group. Rapid change may occur in coccinellid foraging patterns, perhaps due to conditioning, and coccinellids may swiftly adapt to new habitats through selection acting on the expression pre-existing traits. Diet, as a determinant of coccinellid migration and gene flow, is likely to affect probable modes of speciation in different coccinellid groups. Parapatric speciation and possibly sympatric speciation are suggested as of possible importance in the genesis of new coccinellid species through prey and habitat shifts.