Spatial distribution patterns of the gorgonians <Emphasis Type=Italic>Eunicella singularis</Emphasis>, <Emphasis Type=Italic>Paramuricea clavata</Emphasis>, and <Emphasis Type=Italic>Leptogorgia sarmentosa</Emphasis> (Cape of Creus,Northwestern Mediterranean Sea)

Most of the current knowledge on Mediterranean gorgonians is restricted to investigations of those populations found within shallow sublittoral waters, and only limited data are available for populations located below scuba depth. To overcome this lack of information, the occurrence and abundance of the gorgonians Eunicella singularis, Paramuricea clavata, and Leptogorgia sarmentosa were investigated in northwestern Mediterranean benthic communities over a wide geographical (60 km of coastline) and bathymetrical (0–70 m deep) extent using a remotely operated vehicle (ROV). The greatest occurrence and abundances of E. singularis and P. clavata were concentrated in areas that are directly exposed to strong near-bottom currents. E. singularis was the most common and abundant species and displayed great plasticity and amplitude in its environmental preferences. Conversely, P. clavata showed a very patchy distribution that was associated with vertical rocky walls. Only isolated colonies of L. sarmentosa were observed in the study area. Hot spots of abundance of E. singularis and P. clavata were identified below a depth of 40 m, which demonstrates the importance of studying the distribution of benthic species over a wide geographical and bathymetrical extent.     

Monitoring acoustically tagged king prawns <Emphasis Type=Italic>Penaeus</Emphasis> (<Emphasis Type=Italic>Melicertus</Emphasis>) <Emphasis Type=Italic>plebejus</Emphasis> in an estuarine lagoon

Fine-scale movement patterns in penaeid prawns are rarely observed in situ, but are essential in understanding habitat use, foraging, and anti-predator behaviour. Acoustic telemetry was applied to examine the activity, space utilization, and habitat use of the eastern king prawn Penaeus (Melicertus) plebejus, at small temporal and spatial scales. Tracking of sub-adult P. plebejus (n = 9) in Wallagoot Lake (36.789°S, 149.959°E; 23 April–12 May 2009) and calculation of a minimum activity index (MAI) revealed high variation in activity rates across diel periods and in different habitats. Elevated activity rates and movement indicated foraging in unvegetated habitats during the night. Areas within the 95 and 50% space utilization contours averaged 2,654.1 ± 502.0 and 379.9 ± 103.9 m², respectively, and there was a significant negative relationship between these areas and prawn activity rates in unvegetated habitats. This study provides the first estimates of prawn activity rates and space utilization in the field. Application of acoustic telemetry can increase knowledge of prawn movements and their interactions with other marine species in different habitats.     

Sympatry in grapsoid crabs (genera <Emphasis Type=Italic>Planes</Emphasis> and <Emphasis Type=Italic>Plagusia</Emphasis>) from olive ridley sea turtles (<Emphasis Type=Italic>Lepidochelys olivacea</Emphasis>), with descriptions of crab diets and masticatory structures

Grapsoid crabs of the genera Planes and Plagusia are commonly referred to as “rafting crabs” due to their propensity to live on flotsam and pelagic marine animals. Planes minutus and Planes major (=Planes cyaneus) are epibionts of sea turtles. Occurrences of grapsoid crabs in the genera Planes and Plagusia were evaluated on a total of 27 olive ridley sea turtles, Lepidochelys olivacea, from the eastern tropic Pacific (1998–2001) and the Hawaiian Islands (2002) captured in July–December each year. This is the first report of Planes marinus and Plagusia squamosa on sea turtles, and of P. major, P. marinus, and P. squamosa in sympatry on a confined substrate. Stomach content analyses showed P. major and P. marinus consumed a variety of neuston and marine vegetation, with the former consuming considerably more animal material. Epibiotic P. squamosa consumed mostly plant material. The three Planes species had distinctive differences in gastric mill tooth morphology. The versatile mouthparts of P. marinus are described and resemble those of their congeners. Most female P. major and P. marinus collected were ovigerous and present in all survey months.     

Feeding behaviour of the sea cucumber <Emphasis Type="Italic">Cucumaria frondosa</Emphasis> (Echinodermata: Holothuroidea) in the laboratory and the field: relationships between tentacle insertion rate,flow speed,and ingestion

The sea cucumber, Cucumaria frondosa, is a benthic suspension feeder that captures food particles on its tentacles and then inserts them into its mouth one at a time. Previous studies have suggested that tentacle insertion rate (TIR) could be a useful indicator of food intake. The present study determined whether flow velocity affects TIR and whether TIR is a good indicator of ingestion. Video observations of sea cucumbers in Passamaquoddy Bay (45°01.70N, 66°55.74W) in August 1995 showed that TIRs increased with velocities up to 55 cm s⁻¹ and decreased steadily at flows above that up to 130 cm s⁻¹. In October 2006, laboratory flume studies were carried out on specimens collected from the same site in the previous August. Temperature and salinity (12°C and 32) in the flume were the same as in the field at the time of collection. There was high individual variation in feeding behavior at free-stream velocities of 4–40 cm s⁻¹ and TIR was independent of flow. As the number of tentacle insertions increased in the flume experiments, the amount of chloropigments in the digestive tracts of the sea cucumbers also increased. This suggests that TIR, which can be measured non-intrusively using remote video techniques, could be a good indicator of feeding behavior and ingestion in C. frondosa.     

Comparison of the statolith structures of <Emphasis Type=Italic>Chironex fleckeri</Emphasis> (Cnidaria,Cubozoa) and <Emphasis Type=Italic>Periphylla periphylla</Emphasis> (Cnidaria,Scyphozoa): a phylogenetic approach

The rhopalia and statocysts of Periphylla periphylla (Péron and Lesueur in Ann Mus Hist Nat Marseille 14:316–366,1809) and Chironex fleckeri Southcott (Aust J Mar Freshw Res 7(2):254–280 1956) were examined histologically and showed several homologous characteristics. Differences in sensory area distribution could be connected to a slightly different functionality of equilibrium sensing. In P. periphylla, the statoliths (crystals) grow independently of each other; whereas in C. fleckeri, one large crystal covers the smaller ones. The structures of both statoliths were examined in detail with single-crystal diffraction, microtomography and diffraction contrast tomography. The single compact statolith of C. fleckeri consisted of bassanite as was previously known only for other rhopaliophoran medusae. An origin area with several small oligocrystals was located in the centre of the cubozoan statolith. The origin areas and the accretion of statoliths are similar in both species. Our results lead to the assumption that the single bassanite statolith of C. fleckeri (Cnidaria, Cubozoa) is a progression of the scyphozoan multiplex statolith. It is therefore suggested that the Cubozoa are derived from a scyphozoan ancestor and are a highly developed taxa within the Rhopaliophora.     

Interactions between an invasive and a native bryozoan (<Emphasis Type=Italic>Membranipora membranacea</Emphasis> and <Emphasis Type=Italic>Electra pilosa</Emphasis>) species on kelp and <Emphasis Type=Italic>Fucus</Emphasis> substrates in Nova Scotia,Canada

Most research on biological invasions to date has focused on the population dynamics of very successful and disruptive introduced species; however, additional knowledge of the biology of the native species is essential for understanding interactions between the two and may reveal factors that limit invasion success. The invasive bryozoan Membranipora membranacea interacts with native Electra pilosa on two substrates in northwest Atlantic subtidal habitats: highly dynamic and fast-growing kelps; and smaller, more stable, and slow-growing fucoid algae. We quantified the relative abundance and evaluated encounter outcomes in different seasons of these two bryozoans on kelp and Fucus at four sites in Nova Scotia. We also examined the effects of substrate (kelp, Fucus), temperature (7, 10, 13°C), and food (limited, unlimited) on growth rates of E. pilosa in laboratory experiments and using field manipulations. We compared our findings on factors affecting the growth of E. pilosa to those on M. membranacea obtained in similar and thus directly comparable experiments from a previous study. The proportional abundance of M. membranacea was greater than that of E. pilosa on kelps, but the opposite was observed on Fucus. Competitive standoffs between the two bryozoans were more frequent than expected, with no differences recorded between substrates; most encounters were won by M. membranacea. Growth of E. pilosa was faster on Fucus than kelp, decreased with increasing temperature only on Fucus, and was not affected by food. Growth rate of E. pilosa in all treatments was slower than that previously measured for M. membranacea. Faster growth and strong overgrowth abilities likely interact on kelps to ensure success of the invasive bryozoan. Success can be limited by low space availability, which in turn restricts growth rate, and consequently, colony size, such as on fucoid substrates. The incorporation of alternative contexts into invasion research can reveal factors involved in the resilience of native communities.     

Reduced planktotrophy in larvae of <Emphasis Type="Italic">Clypeaster</Emphasis><Emphasis Type="Italic">rosaceus</Emphasis> (Echinodermata,Echiniodea)

Phylogenetic analyses have demonstrated that nonfeeding larvae have evolved from feeding larvae many times among marine invertebrates. In light of this observation, it is surprising that an intermediate strategy, a larva that can feed but is provisioned with enough energy to metamorphose without acquiring exogenous food (i.e., facultative planktotrophy), is rare. A hypothesis for the lack of facultative planktotrophic species among marine invertebrates is that the transition from feeding to nonfeeding is rapid due to this intermediate stage being evolutionarily unstable. Evidence that would support this hypothesis is if species with facultative planktotrophy have reduced food assimilation when compared with obligate planktotrophs. We studied a species with facultative planktotrophic larvae, Clypeaster rosaceus, that is very near the boundary between facultative and obligatory planktotrophy, to answer two questions: (1) does feeding during the larval stage result in energy gains in larval or juvenile stages and (2) if not, are larvae capable of assimilating exogenous food at all. Our measurements of energetics in larval and juvenile stages show that C. rosaceus larvae accumulate very little if any energy when fed, but stable isotope data indicate that larvae are able to assimilate some food. Our results are consistent with similar studies on facultative planktotrophic larvae suggesting poor food assimilation and rapid loss of larval feeding after a population evolves the ability to reach metamorphosis without feeding (lecithotrophy).     

Selfing in <Emphasis Type=Italic>Parvulastra exigua</Emphasis>: an asterinid sea star with benthic development

Parvulastra exigua, a species that lacks a dispersive larva, is paradoxically one of the most widely distributed and abundant sea stars in Australia. The potential that self-fertilization and successful development of self-generated progeny might contribute to population maintenance in this species was investigated through induction of spawning in isolated individuals collected from five populations near Sydney, New South Wales (34°S, 151°E), during the spawning period (August–October 2010, 2011). Evidence of selfing differed significantly among the five populations but the level of selfing within individual egg masses did not. Overall, there was a mean of 8.9% fertilization in egg masses with embryos. Some clutches developed to the juvenile stage while others arrested development before hatching. The presence of miniscule testis tissue in gonads that appeared to be ovaries indicated that hermaphroditism may be more common in some populations than indicated by anatomy. Mixed mating (selfing + outcrossing), pseudocopulation during egg laying and developmental success of self-fertilized embryos may contribute to the ecological success of P. exigua. These might influence population genetic structure and would facilitate establishment of founder populations by a small number of migrants.     

Costs of exclusive male parental care in the sea spider <Emphasis Type=Italic>Achelia simplissima</Emphasis> (Arthropoda: Pycnogonida)

Sea spiders are one of the few marine invertebrates whose males care exclusively for offspring. The costs of parental care, however, have never been addressed for any species of pycnogonid. Costs may be significant for brooding sea spiders of Achelia simplissima, since males carry up to 12 egg masses simultaneously and actively aerate those eggs by moving their ovigerous legs back and forth. This study explored four potential costs to males as a result of parental care: predation, dislodgment, movement and feeding patterns, and frequency of epibionts. Brooding males were found to experience significantly higher frequencies of predator attacks and epibionts, as well as a lower rate of movement compared with nonbrooding males. Interestingly, brooding males were harder to dislodge than nonbrooding males and experienced no change in feeding frequency as a result of parental care. This is the first study to provide evidence that parental care may be costly for male pycnogonids in terms of individual survival and future reproductive success.     

The invasive venomous striped eel catfish <Emphasis Type=Italic>Plotosus</Emphasis><Emphasis Type=Italic>lineatus</Emphasis> in the Levant: possible mechanisms facilitating its rapid invasional success

The venomous striped eel catfish Plotosus lineatus was first recorded in the Mediterranean in 2002. Within 1–3 years, it has spread throughout the entire Israeli coast. We have studied its spatiotemporal distribution patterns via trawl surveys in order to determine the scale and extent of this invasion. Findings indicate that a population explosion has occurred, and the catfish now inhabits all sandy and muddy substrates up to ca 80 m. P. lineatus was found to recruit in autumn in the Mediterranean and displays similar or improved growth patterns and condition factor compared to those found in its native habitat. We discuss the possible ecological mechanisms responsible for its success: Benthic invaders are among its main prey items, suggesting an invasional meltdown process. We also point to the decline of indigenous species using its trophic and behavioral–ecological niche and hypothesize that they might be outcompeted and displaced by the catfish.     

Brooding and development of <Emphasis Type=Italic>Anasterias minuta</Emphasis> (Asteroidea: Forcipulata) in Patagonia,Argentina

Brooding, embryonic and larval development, and the influence of environmental and biological factors in tidepool habitats were studied in the sea star, Anasterias minuta, at various sites along ~220 km of the Patagonian coast. This species has a benthic, lecithotrophic development that includes eight distinct developmental stages. A larval organ, the connection cord, is developed from a small preoral lobe at early stages of development and becomes larger and thinner at advanced stages. Fecundity and average egg size increased with female body size. The regression of log egg number to log sea-star size and weight at different sites had a slope significantly less than 3.0, resulting in negative allometry and indicating that brood capacity was limited in large females. Development was generally synchronous among sites, but varied within each brood at advanced stages, with more developed brooded larvae located at the periphery of the brood mass. Brooding was synchronous among various populations at different years and spatial scales, and extended over a period of 8 months. The highest proportion of brooding females occurred during May and June (austral winter). Juveniles were released mainly during September. The likelihood of finding brooding sea stars decreased with increasing sea water temperature, tidal height, and wave exposure, and increased with increasing body size. Both body size of brooding females and brooding rate were higher in the infralittoral fringe than at midlittoral levels. A revision of the current model of brooding behavior and development among forcipulate sea stars is given.     

Food availability and physiological state of sea urchin larvae (<Emphasis Type="Italic">Strongylocentrotus purpuratus</Emphasis>)

Food availability is highly variable in the ocean. Many species of marine invertebrates have a larval form that depends upon exogenous nutrients for growth, yet there are few biochemical and physiological indices for determining changes in the nutritional status of larvae. In this study, the effects of food availability on biochemical compositions and metabolic processes of larvae of the sea urchin, Strongylocentrotus purpuratus, were determined. Larvae were cultured under different food concentrations (fed-to-excess and unfed) and a suite of biological processes assayed, ranging from measurements at the level of the whole organism to that of specific molecules. These data were normalized to DNA content (an index of cell number) to allow comparisons of physiological rates in larvae of different sizes. Changes in the following were measured during larval growth: free amino acid pool, protein, lipid classes (cholesterol, free fatty acids, hydrocarbons, phospholipids, triacylglycerol), enzyme activities (Na⁺, K⁺-ATPase and citrate synthase), and respiration rates. In growing larvae, the two key components that showed differential cell-specific content relative to unfed larvae were glycine in the free amino acid pool and phospholipids. Additionally, several lipid classes were detectable only in fed larvae (cholesterols, free fatty acids, and hydrocarbons). While triacylglycerols were present in eggs and utilized during pre-feeding development, they were not re-accumulated at detectable levels in feeding larvae. Respiration rates, protein content, and enzyme activities were all similar on a cell-specific basis, showing that these variables did not provide useful indices of differences in physiological state between fed and unfed larvae. In contrast, measurements of the cell-specific content of glycine and certain lipid classes did provide useful indices of physiological state of larvae. Application of these indices could potentially allow for determinations of nutritional state of larvae in the ocean.     

Aerial surveys of manatees (<Emphasis Type=Italic>Trichechus manatus)</Emphasis> in Lee County,Florida<Emphasis Type=Italic>,</Emphasis> provide insights regarding manatee abundance and real time information for managers and enforcement officers

Conservation and management of the endangered Florida manatee is often centered on reducing mortality caused by watercraft collisions. Lee County, Florida, has led the state in watercraft-related mortality for eight of the last 10 years. This county is of particular concern as it contains important habitat for manatees, including extensive feeding grounds and an artificial warm-water refuge where more than 900 manatees have been recorded on a single day. Distributional aerial surveys were conducted from April 2007 through April 2009 over Lee County waters. Surveys yielded higher numbers of manatees than previously observed in this area. Using GIS methodology, kernel density analysis illustrated seasonal changes in distribution patterns and highlighted areas where manatees were most densely clustered. For example, during summer months, manatees were widely distributed throughout the survey area, with high-density areas associated with seagrass beds. During winter months, manatees were densely clustered at warm-water sites and over feeding grounds within close distance of these sites. These seasonal distribution patterns coincide well with speed zone designations. Counts and distributions of manatees were made available, almost immediately if necessary, to local marine law enforcement in an attempt to focus resources toward reducing manatee-watercraft collisions. Future studies should implement similar communication strategies to improve conservation efforts.     

Sexual and asexual reproduction of <Emphasis Type="Italic">Coscinasterias</Emphasis><Emphasis Type="Italic">tenuispina</Emphasis> (Echinodermata: Asteroidea) from Rio de Janeiro,Brazil

An intertidal population of the fissiparous sea star Coscinasterias tenuispina (Lamarck, 1816) was sampled over a 1 year period at Ponta de Itaipu, Niterói, Rio de Janeiro. Gonadal indices revealed an annual reproductive cycle. Spawning occurred in the late winter and early spring between August and November. Pyloric caecal indices did not show a clear annual cycle or a reciprocal relationship with gonadal indices. The population appears to be sustained only by fission, as only males were found. Fission occurred throughout the year, but was most frequent in the winter (July, August and September). Incidence of fission was correlated with the occurrence of the extremely low tides during daytime that exposes many specimens to air. Austral winter tides are low by day and high by night, while the austral summer tides are low by night and high by day. The most extreme annual deviation in seawater temperature is about 5°C. Larval recruitment seems to be negligible, since very small individuals were not found.     

Feeding aggregations of sea stars (<Emphasis Type="Italic">Asterias</Emphasis> spp. and <Emphasis Type="Italic">Henricia sanguinolenta</Emphasis>) associated with sea urchin (<Emphasis Type="Italic">Strongylocentrotus droebachiensis</Emphasis>) grazing fronts in Nova Scotia

Migrating feeding aggregations (or fronts) of sea urchins can dramatically alter subtidal seascapes by destructively grazing macrophytes. While direct effects of urchin fronts on macrophytes (particularly kelps) are well documented, indirect effects on associated fauna are largely unknown. Secondary aggregations of predators and scavengers form around fronts of Strongylocentrotus droebachiensis in Nova Scotia. We recorded mean densities of the sea stars Asterias spp. (mainly A. rubens) and Henricia sanguinolenta of up to 11.6 and 1.7 individuals 0.25 m⁻² along an urchin front over 1 year. For Asterias, mean density at the front was 7 and 15 times greater than in the kelp bed and adjacent barrens, respectively. There was strong concordance between locations of peak density of urchins and sea stars (Asterias r = 0.98; H. sanguinolenta r = 0.97) along transects across the kelp–barrens interface, indicating that sea star aggregations migrated along with the urchin front at rates of up to 2.5 m per month. Size–frequency distributions suggest that Asterias at the front were drawn from both the barrens (smaller individuals) and the kelp bed (larger individuals). These sea stars fed intensively on mussels on kelp holdfasts and in adjacent patches. Urchin grazing may precipitate aggregations of sea stars and other predators or scavengers by incidentally consuming or damaging mussels and other small invertebrates, and thereby releasing a strong odor cue. Consumption of protective holdfasts and turf algae by urchins could facilitate feeding by these consumers, which may obtain a substantial energy subsidy during destructive grazing events.     

Spatial patterns and environmental correlates in leaf-associated epifaunal assemblages of temperate seagrass (<Emphasis Type=Italic>Zostera marina</Emphasis>) meadows

We estimated and tested variability of seagrass leaf-associated epifaunal assemblages at a range of scales. Sampling was performed in 36 seagrass (Zostera marina) meadows within three regions along the Swedish west coast following a hierarchical design (samples separated by 10 s m, km or 100 km). Results showed strongest variability (43–81%) at the intermediate amongst-meadow (km) scale using biomass of functional categories, while considering taxa composition the within-meadow (10 s m) scale contributed most to variability (60%). Using functional categories, we found that embayment exposure and seagrass shoot density were the most important predictor variables explaining part of the variability in biomass of suspension feeders (bivalves and barnacles) and grazers. In contrast, variability in epifaunal taxa composition was predicted mainly by sediment chemistry, substratum coverage and geographical positioning. Our findings suggest that models to develop predictive power and mechanistic understanding should focus on variables and processes varying at small and intermediate scales rather than those varying at larger scales.     

Genetic population structure in a commercial marine invertebrate with long-lived lecithotrophic larvae: <Emphasis Type="Italic">Cucumaria</Emphasis><Emphasis Type="Italic">frondosa</Emphasis> (Echinodermata: Holothuroidea)

The patterns of genetic diversity and connectivity were investigated in Cucumaria frondosa, the most abundant sea cucumber in the North Atlantic, to assist in the management and conservation of this ecologically important marine invertebrate, which is the target of an emerging fishery. Mitochondrial DNA COI sequences of 334 C. frondosa were obtained and analyzed, mainly from its western North Atlantic range, where the commercial fishery is being developed, with complementary sampling in the mid- and eastern North Atlantic. Analysis of molecular variance showed no significant (P > 0.05) differences among subpopulations in the western region suggesting that it constitutes one panmictic population. The same analysis showed low, but significant differences between eastern and western Atlantic populations. Coalescent analyses using isolation with migration models and a Bayesian skyline plot indicated historical divergence and a general increase in population size prior to the last glacial maximum and highly asymmetric gene flow (nearly 100 times lower from west to east) between sea cucumbers from North America and Norway. Results suggest that subpopulations of C. frondosa within the western North Atlantic have been highly connected. We propose that aided by the high-connectivity local subpopulations can recover rapidly from natural (i.e., ice ages) or anthropogenic (i.e., overfishing) population declines through recruitment from deep refugia.     

Reproductive cycle of two commercial species of sea cucumber (Echinodermata: Holothuroidea) from Caribbean Panama

The reproductive status of the holothuroid species Isostichopus badionotus (Selenka, 1867) and Holothuria mexicana (Ludwig, 1875) was studied over 16 months in Bocas del Toro (Panama), from November 1999 to February 2001. Sexual reproduction was evaluated by the gonad index method, and by histology of gonad development. In addition, population structure was assessed based on sex ratio, minimum reproductive size, and length and weight distributions of males and females. The sex ratio in both species was 1:1, with a unimodal population distribution composed mainly of mature individuals. The minimum reproductive length and weight were 13-20 cm and 150 g, respectively, for both species, although reproductive individuals 10 cm in length were also found. A consistently higher gonad index was observed in H. mexicana, due to a high proportion of mature females and males and high gonad indices in most monthly samples. Gametogenesis and spawning patterns seemed to occur throughout the year, with periods of enhanced activity. Two periods of maximum reproductive activity were tentatively identified: July-November for I. badionotus and February-July for H. mexicana, but neither species had a single, sharply defined annual spawning event. Further work on these exploited holothuroids should examine the relationships between reproduction and environmental factors and between reproductive status and recruitment.     

Fine-scale observations of the predatory behaviour of the carnivorous copepod <Emphasis Type=Italic>Paraeuchaeta norvegica</Emphasis> and the escape responses of their ichthyoplankton prey,Atlantic cod (<Emphasis Type=Italic>Gadus morhua</Emphasis>)

Paraeuchaeta norvegica (8.5 mm total length) and yolk-sac stage Atlantic cod larvae (4 mm total length) (Gadus morhua) larvae were observed in aquaria (3 l of water) using silhouette video photography. This allowed direct observations (and quantitative measurement) of predator–prey interactions between these two species in 3-dimensions. Tail beats, used by cod larvae to propel themselves through the viscous fluid environment, also generate signals detectable by mechanoreceptive copepod predators. When the prey is close enough for detection and successful capture (approximately half a body-length), the copepod launches an extremely rapid high Reynolds number attack, grabbing the larva around its midsection. While capture itself takes place in milliseconds, minutes are required to subdue and completely ingest a cod larva. The behavioural observations are used to estimate the hydrodynamic signal strength of the cod larva’s tail beats and the copepod’s perceptive field for larval fish prey. Cod larvae are more sensitive to fluid velocity than P. norvegica and also appear capable of distinguishing between the signal generated by a swimming and an attacking copepod. However, the copepod can lunge at much faster velocities than a yolk-sac cod larva can escape, leading to the larva’s capture. These observations can serve as input to the predator–prey component of ecosystem models intended to assess the impact of P. norvegica on cod larvae.     

Male takeover,infanticide, and female countertactics in white-headed leaf monkeys (<Emphasis Type=Italic>Trachypithecus leucocephalus</Emphasis>)

Infanticide by males is common in mammalian species such as primates in which lactation lasts much longer than gestation. It frequently occurs in one-male groups following male takeovers and is likely a male reproductive strategy. Reported female countertactics include abrupt weaning of infants, dispersal, or paternity confusion. Here, we estimated costs of female countertactics in terms of weaning ages and interbirth intervals. We observed a population of white-headed leaf monkeys (Trachypithecus leucocephalus) in Nongguan Nature Reserve, China (1995–2006) mainly composed of one-male groups. Takeovers (N = 11) coincided with the peak conception period. Detailed data are presented for five takeovers (34 females, 29 infants, and 47 group-years) leading to six infant disappearances (42.9% of infant mortality). All presumed infanticides were in accordance with the sexual selection hypothesis. Following a takeover, females without infants or with old infants stayed with the new males, incurring no or low costs (via abrupt weaning). Females with young infants dispersing with the old males also experienced low costs. High costs (due to infant loss) were incurred by pregnant females and those with young infants who stayed with the new males indicating that paternity was not confused. Costs in terms of long interbirth intervals were also high for females leaving with the old males to later join the new males, despite infant survival. Female countertactics reflected female philopatry mediated by infant age. Presumably due to the seasonal timing of takeovers, most countertactics seemed successful given that 32.3% of females apparently incurred no costs and 41.2% incurred only low costs.