Mysterious bio-duck sound attributed to the Antarctic minke whale (Balaenoptera bonaerensis)

For decades, the bio-duck sound has been recorded in the Southern Ocean, but the animal producing it has remained a mystery. Heard mainly during austral winter in the Southern Ocean, this ubiquitous sound has been recorded in Antarctic waters and contemporaneously off the Australian west coast. Here, we present conclusive evidence that the bio-duck sound is produced by Antarctic minke whales (Balaenoptera bonaerensis). We analysed data from multi-sensor acoustic recording tags that included intense bio-duck sounds as well as singular downsweeps that have previously been attributed to this species. This finding allows the interpretation of a wealth of long-term acoustic recordings for this previously acoustically concealed species, which will improve our understanding of the distribution, abundance and behaviour of Antarctic minke whales. This is critical information for a species that inhabits a difficult to access sea-ice environment that is changing rapidly in some regions and has been the subject of contentious lethal sampling efforts and ongoing international legal action.     

Modeling the effects of El Niño, density-dependence, and disturbance on harbor seal (Phoca vitulina) counts in Drakes Estero, California: 1997–2007

Harbor seal ( Phoca vitulina ) haul-out site use may be affected by natural or anthropogenic factors. Here, we use an 11-yr (1997–2007) study of a seal colony located near a mariculture operation in Drakes Estero, California, to test for natural (El Niño-Southern Oscillation (ENSO), density-dependence, long-term trends) and anthropogenic (disturbance or displacement related to oyster production activities) factors that may influence the use of haul-out subsites. Annual mariculture related seal disturbance rates increased significantly with increases in oyster harvest ( r _s= 0.55). Using generalized linear models (GLMs) ranked by best fit and Akaike's Information Criteria, ENSO and oyster production (as a proxy for disturbance/displacement) best explained the patterns of seal use at all three subsites near the mariculture operations, with effects being stronger at the two subsites closest to operations. Conversely, density-dependence and linear trend effects poorly explained the counts at these subsites. We conclude that a combination of ENSO and mariculture activities best explain the patterns of seal haul-out use during the breeding/pupping season at the seal haul-out sites closest to oyster activities.     

Patterns of energy storage in Pseudoboeckella poppei (Crustacea,copepoda) from two contrasting lakes on Signy Island,Antarctica

The copepod Pseudoboeckella poppei (Daday) (Calanoida, Centropagidae) was sampled from Sombre and Heywood Lakes on Signy Island, Antarctica (60° S, 45° W) between January 1984 and March 1985. Sombre Lake is clear and oligotrophic with little phytoplankton and a bottom sediment low in organic content. By contrast Heywood Lake is turbid and mesotrophic; a substantial phytoplankton develops in summer and the bottom sediments are comparatively rich in organics. Both lakes freeze over for much of the year, forcing the copepods to adopt a benthic feeding strategy over winter. Adult Pseudoboeckella feed on phytoplankton when this is available, but also on detritus, diatoms and short algal filaments stirred up from the sediment. In Heywood Lake, male copepods show a smooth seasonal trend in lipid content with lipid being synthesised in early summer and utilised in late summer and winter. The summer increase in lipid content is associated with an increase in dry weight. Female lipid contents show evidence of two peaks of egg production. In Sombre Lake both male and female copepods increase in size during summer and show a wider range of lipid contents than in Heywood Lake; it is likely that this is due to the poorer winter feeding conditions which necessitate the synthesis of a much larger store of reserves during the summer. In contrast to marine calanoid copepods, lipid stores are exclusively triacylglycerol with no trace of wax ester.     

RESPONSE OF ANTARCTIC FUR SEALS TO IMMOBILIZATION WITH KETAMINE, A KETAMINE-DIAZEPAM OR KETAMINE-XYLAZINE MIXTURE, AND ZOLETIL®

Adult Antarctic fur seals (Arctocephalus gazella) were immobilized with Zoletil^® ( n = 172), ketamine ( n = 30), ketamine mixed with diazepam ( n = 23) and with ketamine mixed with xylazine ( n = 45). Response to all drugs was highly variable. There was a relationship between dose rate and level of immobilization in females given Zoletil^®. Males were slightly more sensitive to Zoletil^® than females but this could have been due to the greater body mass and lower mass-specific metabolic rate of males. The dose required to achieve a level of immobilization declined with greater body mass for Zoletil^® and ketamine but not for ketamine-diatepam. Ketamine and ketamine-sedative mixtures commonly caused mild tremoring and occasionally caused convulsions. Neither reaction was seen with Zoletil^®. Mean doses were, Zoletil^® 1.5 mg/ kg, ketamine 6.9 mg/kg, ketamine-diazepam 6.3 mg/kg ketamine and 6.3 μg/kg diazepam, and ketamine-xylazine 7.3 mg/kg ketamine and 0.62 mg/ kg xylazine. Zoletil^® performs at least as well on Antarctic fur seals as ketamine but it may cause respiratory depression. The dose of ketamine required for Antarctic fur seals was greater than for most other species of seals.     

TRACE METALS AND METHYL MERCURY: ASSOCIATIONS AND TRANSFER IN HARP SEAL (PHOCA GROENLANDICA) MOTHERS AND THEIR PUPS

Milk samples from the stomachs of harp seal pups were analysed for Cu, Zn, Se, Cd and Hg, as were liver, kidney, and muscle from mother-pup pairs. Tissues were also analysed for MeHg. Milk contained, in addition to essential trace metals, Cd and Hg (57 ng/g and 6.5 ng/g respectively).
Pups had mercury in all three tissues. The percent methyl mercury in liver of pups was higher than in liver of mothers. Mercury in muscle was mostly methyl mercury in both mothers and pups. Total mercury in liver of mothers but not pups was correlated positively with selenium. Estimates of ingested mercury by pups indicated they had acquired most of their mercury during gestation.
Although mothers had cadmium in liver and kidney, it was not detected in tissues of pups. Cadmium did not transfer across the placenta, while mercury did. Tissue concentrations of Cu and Zn were higher in pups than mothers. The presence of metallothionein in pup tissues was postulated.
A strong positive correlation of copper and selenium between mothers and pups indicated transfer of these elements from mother to pup in direct proportion to their concentrations in maternal liver and kidney.     

THE ASSESSMENT OF COMPETITION BETWEEN SEALS AND COMMERCIAL FISHERIES IN THE NORTH SEA AND THE ANTARCTIC1

Most of the exploited fish stocks in the North Sea are also used as a food supply by a number of seal species; the same is true for some fish and invertebrate stocks in the Antarctic—although the fisheries there are, at present, much smaller than those in the North Sea. The information needed for a critical assessment of such interactions is reviewed. Using existing techniques it is possible to estimate the quantity and size-classes of each fish or invertebrate species consumed by seals and to compare this with the commercial catch. If fishing mortality is known, these estimates can be used to calculate the level of mortality imposed by the seals. However, a realistic evaluation requires information on the distribution and movements of the fish, the seals' feeding effort, and the fisheries effort in time and space. At present it is difficult or impossible to obtain this information, but recent technological developments in telemetry equipment will soon make it feasible. To assess the economic effects of changes in seal numbers on the fishery, or the ecological effects of changes in fisheries effort on seal populations, requires additional information on the responses of the fishery and the seals to changes in fish abundance, and of the commercial market to changes in the supply of fish.     

Studies on the morphology and anatomy of the Antarctic nudibranch genera Pseudotritonia Thiele, 1912 and Telarma Odhner, 1934 with a discussion of the family Gharcotiidae Odhner, 1926 (Nudibranchia: Opisthobranchia)

The external morphology and anatomy of the Antarctic nudibranchs Pseudotritonia quadrangularis Thiele, 1912, P. gracilidens Odhner, 1944 and Telarma antarctica Odhner, 1934 are redescribed. Both genera, which were only known by two or one specimen, do not possess a cnidosac, but there is a terminal swelling at the termination of the digestive glandular ramifications in P. gracilidens. This sac is composed of cells with a large vacuole. A glandular stripe on the right side of the body above the genital openings, nephroproct and anal papilla is considered to be a synapomorphy for both genera. The validity of the family Charcotiidae and the affinities to the aeolid genus Notaeolidia Eliot, 1905 and taxa of the Arminacea are discussed.     

Heart structure and ventricular ultrastructure of hemoglobin- and myoglobin-free icefish Channichthys rhinoceratus

Summary The structural and ultrastructural characteristics of the heart of Channichthys rhinoceratus, an antarctic teleost devoid of respiratory pigments, are described and compared with those obtained from the red-blooded related species Notothenia rossii.The heart of the icefish is characterized by a spongy myocardium supplied with a highly developed arterial coronary system. This vasculature includes a subepicardial system and an extensive intratrabecular capillary network. Arterial hilar network and Thebesian vessels may also be present. The bulbus arteriosus shows unusually large spheroid structures located in the middle layer of the wall.Both white- and red-blooded species display comparable myocardial cell morphology and organelle distribution. However, the mitochondrial cristae of the former are more densely packed and the sarcolemma possesses numerous caveolae. A large proportion of non-contractile cells is also found in the icefish ventricular wall.