SOUND PRODUCTION AND SOUND EMISSION IN SEVEN SPECIES OF EUROPEAN TETTIGONIIDS PART III. DETERMINATION OF THE MECHANISM OF SOUND PRODUCTION USING CEPSTRUM ANALYSIS

ABSTRACT

The mechanism of sound production in tettigoniids is examined by applying the method of ‘cepstrum’ analysis to insect calls. The power cepstrum is defined as the inverse Fourier transform of the logarithmic power spectrum. This analysis shows that the tettigoniid sound signal is a convolution in time of probably two components. The first is caused by the initial impact of teeth of the stridulatory file on the left wing against the plectrum on the right wing (termed the input pulse); the second is caused by the oscillating properties of the tegmina (these being a function of the intrinsic frequencies of dorsal fields and mirror and their damping properties). In the cepstrum each component appears as a varying number of peaks. The tooth impacts cause a very low quefrency peak probably representing the time in which the two tegmina are in contact during each impact and high quefrency peaks representing the impulse repetition rate. The oscillating properties of the tegmina cause two major quefrency peaks which can be clearly related to the size of the dorsal fields and of the mirror respectively, and therefore to their intrinsic frequencies. The high damping factor of the tegmina together with the transient shape of the tegminal input pulse causes a strong time limitation of the impulses and is therefore responsible for the broad frequency bands occurring in the power spectra of the tettigoniid songs. The impulse generation of a synthetic tettigoniid song is discussed.     

Ringed seal (Pusa hispida) tooth annuli as an index of reproduction in the Beaufort Sea

Multi-decadal time-series of biological indices that reflect the state of a population are rare in ecological studies, but invaluable for assessing environmental regulation of population dynamics. We utilized canine teeth extracted from ringed seals (Pusa hispida) killed by polar bears (Ursus maritimus) in the Beaufort Sea, Canada, in 1985–2011, to obtain widths of annual growth layers in the cementum. Canine teeth for 75 individuals were measured and compared across years using a proportional width index (PWI) spanning 1965–2007. PWI was positively correlated with ringed seal ovulation rate obtained independently from other studies and was significantly lower than normal during ringed seal reproductive declines in 1974–75, 1984–87, 1991–93, and 2004–05, suggesting that PWI reflects ringed seal reproductive capacity. The PWI was also examined against climatic and sea ice factors to assess environmental regulation of ringed seal reproduction. Results suggest that ringed seals benefit from cyclonic circulation regimes in the Beaufort Sea, and an earlier breakup of sea ice in summer that may positively influence the quality and quantity of food during the open water season. Results highlight how cementum annuli in the canine teeth of ringed seals can provide an index of body state and linkages to sea ice conditions. Canine teeth from ringed seals can function as a means to monitor the effects of past Arctic marine variability on area-specific populations for which there are few independent empirical data.     

Host characteristics and infection level of an intestinal parasite Corynosoma strumosum (Acanthocephala) in the Kuril harbor seal of Erimo Cape,Hokkaido, Japan

The Kuril harbor seal around Hokkaido is presently recovering from a resource crisis while conflicts with local fisheries have become a concern. However, its feeding habits, which are fundamental information for taking proper preventive measures, are still poorly understood. We thus examined the infection status of a trophically-transmitted parasite, Corynosoma strumosum in the seals of Erimo Cape, to assess the host's feeding habits with a practical view of the parasite as a biological indicator. A total of 2802 worms were found from 20 male and 20 female by-caught animals in salmon set nets within local fisheries during August to November 2014. The parasite abundance was explained mainly by the host's developmental stage and intestinal length while weakly affected by gender and body size, through an estimation of generalized linear models combined with hierarchical partitioning. Considering the past records that demersal fishes are the probable main sources of infection, the infection level may owe to individual host differences regarding these sources and/or feeding grounds with relating the host characteristics. This supports that the resource management of Kuril harbor seals requires careful consideration of the individual differences in feeding behavior.     

Cloning and Sequencing of the Vibrio parahaemolyticus fur Gene

A ferric uptake regulatory gene (fur) was cloned from Vibrio parahaemolyticus WP1 by a polymerase chain reaction-based technique followed by functional complementation of a fur mutation in Escherichia coli. A sequence analysis showed that, at the amino acid level, the V. parahaemolyticus Fur protein is 81% identical with the Fur protein from E. coli and over 90% identical with those of the Vibrio species.     

DEVELOPMENT OF HEMOGLOBIN, HEMATOCRIT, AND ERYTHROCYTE VALUES IN GALÁPAGOS FUR SEALS

We studied the ontogeny of hemoglobin concentration, hematocrit and erythrocyte counts in the Galapagos fur seal ( Arctocephalus galapagoensis , Heller 1904). Two hundred and fifty-three animals were sampled between the ages of 22 d and > 8 yr, of which 46 were adult females. Body mass increased steadily with age from 6.1 ± 1.2 kg in 1-mo-old pups ( n = 27) to 28.5 ± 3.3 kg in adult females. Even adult females increased in mass with age. Hemoglobin (Hb), hematocrit (Hct), and red blood cell (RBC) values all increased in a logarithmic fashion with age up to 2 yr. Blood values for pups were Hct: 35.5 ± 4.1%; Hb: 12.9 ± 1.3 g/dl; RBC: 4.1 ± 0.3·10⁶/μl. Half-year-old fur seals (Hct: 42.1 ± 3.2%; Hb: 15.7 ± 1.3 g/dl; RBC: 4.9 ± 0.5·10⁶/μl; n = 50) were the oldest age group to show significantly lower blood values than adult females ( P < 0.001 for all three parameters). Yearling blood values (Hct: 47.2 ± 3.6%; Hb: 17.3 ± 1.6 g/dl; RBC: 5.6 ± 0.4·10⁶/μl; n = 56) did not differ significantly from those of adult females ( P < 0.32; P < 0.26; P < 0.23, respectively). Blood values of adult females were lower than those of 2-yr-olds (Hct: 49.6 ± 2.4%; Hb: 18.5 ± 1.2 g/dl; RBC: 5.7 ± 0.3·10⁶/μl; n = 31). These differences were significant only for RBCs ( P < 0.003). Up to the age of 1 yr, age was the best predictor for blood values, thereafter mass tended to be a better predictor. Female juveniles between the ages of 150 and 600 d had higher blood values than same-age males. The relationship of blood value development to diving activity is briefly described and the results are compared to values of other marine mammals. Ontogeny is discussed in relation to the development of these blood values in terrestrial mammals.     

A REASSESSMENT OF THE IMPACT OF THE EXXON VALDEZ OIL SPILL ON HARBOR SEALS (PHOCA VITULINA RICHARDSI) IN PRINCE WILLIAM SOUND, ALASKA

Analyses of population trends and movements of harbor seals in Prince William Sound (PWS) casts doubt on published findings that 302 seals were killed by the Exxon Valdez oil spill in 1989. Assumptions that seals have 100% fidelity to a haul-out, that they were not displaced by the spill and associated disturbances, and that population trends throughout PWS varied similarly, except for oil spill effects, are not supported. Survey efforts to account for missing seals in 1989 were incomplete, too late in the year, and geographically limited. Basic assumptions required for statistical comparisons of oiled and unoiled haul-outs were violated. Fourteen dead seals, mostly pups, were recovered in PWS. Cause of death in most instances could not be determined, nor could the proportion that would have died naturally. Evidence does not support high unsubstantiated mortality, but is more consistent with seals avoiding or moving away from some oiled haul-outs. Interpretation of survey results requires consideration of temporal and regional variation. "Route A" surveys of central and eastern PWS do not represent population trends in western PWS or at glacial haul-outs. To adequately monitor population trends of PWS as a whole, broader sampling must be conducted on a routine basis.     

SHIPBOARD LINE TRANSECT SURVEYS OF CRABEATER SEAL ABUNDANCE IN THE PACK-ICE OFF EAST ANTARCTICA: EVALUATION OF ASSUMPTIONS

We examine the extent to which the assumptions underlying line transect sampling are satisfied in shipboard surveys of crabeater seals ( Lobodon carcinophaga ) hauled out on the Antarctic pack-ice. Measurement of the perpendicular distance of seal groups from the ship with an electronic inclinometer fitted to a rifle stock was unbiased. Crabeater seals showed little movement in response to the approaching ship. Movement away from the ship by seals close to the ship's track was partially responsible for a relative lack of sightings close to the transect-line, but otherwise had little effect on the sighting histogram. Minor deviations from the transect direction to avoid running over seals violated the assumption of uniform distribution of groups, and contributed to a relative lack in sightings close to (<40 m) the transect-line. We estimate that 5%-10% of seal groups close to the transect-line were not sighted by bridge observers prior to passing abeam of the ship, but most of these missed groups were likely to have been sighted some distance behind-abeam. Shipboard transects provided a biased sample of four environmental features known to be related to crabeater seal abundance because of logistical difficulties in the ship traversing along straight transects through thick ice. Calculation of transect length L from successive GPS locations was mildly sensitive to the frequency of locations. We provide analytical recommendations to reduce or eliminate the effect of assumption violation when present and hence minimize bias in abundance estimation.     

Pilot trophic model for subantarctic water over the Southern Plateau, New Zealand: a low biomass, high transfer efficiency system

The Southern Plateau subantarctic region, southeast of New Zealand, is an important feeding area for birds, seals and fish, and a fishing ground for commercially significant species. The Southern Plateau is a major morphometric feature, covering approximately 433,620 km² with average depth of 615 m. The region is noted for its relatively low levels of phytoplankton biomass and primary production that is iron-limited. In order to evaluate the implications of these attributes for the functioning of this ecosystem a steady-state, 19-compartment model was constructed using Ecopath with Ecosim software of Christensen et al. [www.ecopath.org]. The system is driven by primary production that is primarily governed by the supply of iron and light. The total system biomass of 6.28 g C m⁻² is very low compared with systems so far modelled with a total system throughput of 1136 g C m⁻² year⁻¹. In the model, the Southern Plateau retains 69% of the biomass in the pelagic system and 99% of total production. Although fish are caught demersally, most of their food is part of production in the pelagic system. Top predators represent about 0.3% of total biomass and account for about 0.24 g C m⁻² year⁻¹ of food consumed made up of birds 0.058 g C m⁻² year⁻¹, seals 0.041 g C m⁻² year⁻¹, and toothed 0.094 g C m⁻² year⁻¹ and baleen whales 0.051 g C m⁻² year⁻¹. This amounts to 105,803 tonnes carbon over the whole of the Southern Plateau and is about 17% of the total amount of food eaten by non-mesopelagic fish. Mean transfer efficiencies between trophic levels II and IV of 23% are at the high end of the range reported in the literature. In the model, adult fish production is almost completely accounted for by the fisheries take (32%), consumption by seals (7%), toothed whales (21%), other adult fish (13%), and squid (20%). Fish and squid catches are at the trophic levels of 4.8 and 5.0, respectively. The gross efficiency of the fishery is 0.018% (catch/primary production). Although not all data come from direct knowledge of this system, the model reflects its general characteristics, namely a low primary production system dominated by the microbial loop, low sedimentation to the seafloor, high transfer efficiencies, a long food web and supporting high-level predators.     

ESTIMATION OF AGE-SPECIFIC PROBABILITIES OF FIRST RETURN AND ANNUAL SURVIVAL RATES FOR THE MALE GRAY SEAL (HALICHOERUS GRYPUS) ON SABLE ISLAND FROM CAPTURE-RECAPTURE DATA

We used a longitudinal capture-recapture study to estimate the age-specific probabilities of first return to the breeding colony and annual survival rates for male gray seals ( Halichoerus grypus ), based on resightings of seals branded as young on Sable Island. We estimated that the average age of first returns for seals born in 1969–1970 to be 9.1 (SE 0.4) yr; for seals born in 1973–1974 it is estimated to be 9.8 (SE 0.2) yr. The estimated annual survival rate of these males was estimated to be 0.976 (SE 0.003).     

ESTIMATING POPULATION SIZE IN ASYNCHRONOUS AGGREGATIONS: A BAYESIAN APPROACH AND TEST WITH ELEPHANT SEAL CENSUSES

Many organisms reproduce in temporary aggregations where estimates of colony size can be made by direct counts. When individuals are not synchronous, however, early breeders depart before the last arrive, so counts underestimate the total breeding population. We present a model describing a colony's census as a function of arrival, breeding tenure, and the correlation between them, and we use it to illustrate how variance in arrival and tenure affect the census. Counts of breeding female northern elephant seals ( Mirounga angustirostris ) from 1975 to 2007 were used to test the model. Four of the model's parameters—population size, mean and variance of arrival date, and the correlation between arrival date and breeding tenure—could be estimated from census data using a Bayesian approach; prior estimates of two other parameters—mean tenure and its variance—had to be used to avoid overparameterization. The model's predictions fit observed censuses well and produced reliable estimates of population size and arrival behavior, showing that the maximum census was 8%–16% below the total number of breeding females. This method could be used for estimating abundance in any asynchronous aggregation, given independent information on one of the defining distributions: arrival, tenure, or departure.