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There are different ecotypes of killer whales (Orcinus orca) worldwide; type D killer whales are the least known. These killer whales have a globose head, an extremely small post-ocular patch and a falcate dorsal fin. We report the first stranding event of type D killer whales recorded in southern South America, in the Magellan Strait, Chile. The group consisted of four adult females, two juvenile females, and two females and one male of indeterminate age class. Total length of adult females averaged 572.8 ± 23.6 cm and juvenile females averaged 397.0 ± 24.0 cm. Dorsal fin height of adult females averaged 57.3 ± 8.5 cm and in juvenile females 30.5 ± 19.1 cm. No obvious signs of anthropogenic intervention were observed. The characteristic small post-ocular white eye patch of this killer whale ecotype measured 21.8 cm long and 5.9 cm wide in the freshest carcass found. All animals presented backswept dorsal fins and a dental formula of 11 to 13 maxillary and mandibular teeth. The length of the largest tooth in each individual ranged from 8.0 to 10.2 cm, suggesting that type D killer whales have smaller teeth. We suggest that the total length of type D killer whales is shorter than other killer whale ecotypes. After 67 years, we report the second known stranding of type D killer whales worldwide and we report for the first time body measurements, size, and number of teeth of this ecotype of killer whales. [ABSTRACT FROM AUTHOR]

Several types of development are reported in the worldwide distributed Family Calyptraeidae. In species with direct development, embryos can grow from large eggs or can feed on nurse eggs, nurse embryos, or other intracapsular nutritional resources. Here the reproductive mode of Trochita pileolus and how biochemical composition varies among egg size between three species of Trochita were studied. Adults and broods of T. pileolus were collected off Tierra del Fuego and nearby Burdwood Bank at depths of 96–151 m. The mean shell diameter of brooding females was 16.3 ± 2 mm and the number of egg capsules observed ranged from 5 to 9. In each egg capsule 7–10 embryos developed from uncleaved eggs of about 500 µm diameter. Neither nurse eggs nor other kinds of extraviteline food sources were recorded. No oophagy, adelphophagy, or late intracapsular cannibalism were observed. The development mode of T. pileolus closely resembles that of the giant T. trochiformis from Chile, in which the energy for developing embryos is obtained from large fertile eggs. The eggs of T. trochiformis had higher lipid content than the other two species and were more energy-dense than glycogen-enriched eggs. The relative lipid coverage area and the hatching size of T. pileus were similar to T. pileolus, although the egg size was three times smaller. This could be attained because T. pileus has developed intracapsular nutritional resources such as nurse eggs and adelphophagy. [ABSTRACT FROM AUTHOR]

Cetaceans are known to play an important role in ecosystem structure and dynamics because they occupy the highest position in food webs. In order to improve our knowledge on the feeding ecology of the long finned pilot whale, Globicephala melas edwardii, in the western South Atlantic Ocean, we analyzed carbon (δ13C) and nitrogen (δ15N) stable isotope composition of bone collagen from 54 specimens found stranded along the coast of Tierra del Fuego, Argentina. Through Bayesian mixing models we estimated the contribution of the most putative prey to the consumer's diet. Prey species were selected, based on previous knowledge and covered all possible foraging areas for the region that were analyzed through a visual spatial analysis (based on sightings records). Based on our results, the long finned pilot whale is mainly a teutophagous species, feeding on squids, and can complement its diet with neritic prey when moving sporadically to coastal areas. We found that the southeastern part of Tierra del Fuego, north of Staten Island and the slope break around the Burdwood Bank are plausible feeding areas, which offer suitable habitats where pilot whales can search for their preferred prey. These areas are important for Argentin's conservation policies, since they enclose three oceanic Marine Protected Areas (Namuncurá–Burdwood Bank, Burdwood Bank II and Yaganes). Therefore, it is crucial to improve the knowledge regarding their foraging preferences in order to provide support for conservation and management strategies in these MPAs. [ABSTRACT FROM AUTHOR]

Fin whales (Balaenoptera physalus) can be found worldwide, in oceanic waters, though are rarely found in coastal areas of wide and shallow continental platforms such as those in the western South Atlantic Ocean. Here we report the first confirmed stranding of a B. physalus off the Atlantic coast of Tierra del Fuego (TDF), in July (austral winter) of 2016. In addition, a bibliographic review of the strandings of this species was carried out on the Argentinian coasts and especially on TDF. The animal was fresh when it was found and may have been alive at the moment of the stranding. The specimen was a physically immature female with a total length 15.8 m. No injuries or fishing gear were observed to suggest accidental entanglement or vessel collision. The specimen's stomachs were empty except for a low-grade infestation with the trematode Ogmogaster antarcticus, but without any associated macroscopic gastric pathology. Although the necropsy was carried out within a few hours of death, we could not make an accurate diagnosis of the cause of death. However, the insufficient fat deposits indicate a bad physical condition and may have contributed to its stranding and subsequent death. This specimen represents the first confirmed stranding of this species in TDF. [ABSTRACT FROM AUTHOR]

Marine invertebrates can display several reproductive strategies, from external reproduction to parental care. Internal brooding is particularly relevant in harsh conditions, like Antarctic/sub-Antarctic waters and deep-sea, since it maximizes the survival of the young. Actinostola crassicornis is an abundant and widely distributed sea anemone from the southwestern Atlantic Ocean. It can be found all along the Argentinean sea down to 1200 m depth, usually in large numbers. It is a unique species in the area, since it is a large white brooding sea anemone. We studied 75 specimens collected by the O/V Walther Herwig and the O/V Puerto Deseado all along its distribution, from about 60 m to 800 m depth, in different seasons of the year. All the specimens were sexed, and the presence of free oocytes and juveniles inside the coelenteron were assessed. Large oocytes (over 500 μm) and juveniles were found in samples from most of the sampled months. We found a larger number of female specimens, and most of the brooding specimens were female. No early developmental stages were found smaller than a sea anemone with about 12 tentacles. We conclude that A. crassicornis reproduces continuously throughout the year and that although most of the juveniles were found in females, male specimens can breed. Brooding has great benefits in terms of protecting the offspring, since predation upon the juveniles is prevented, but dispersal of the offspring is low, shown by the aggregated distribution of the species. [ABSTRACT FROM AUTHOR]

Subpolar coastal waters are key hotspots in the global carbon cycle. However, the small-scale distribution of partial pressure of carbon dioxide (p CO 2) in these environments and the physical and biological controls underlying this variability are still poorly understood. Here, we examine simultaneous high-resolution spatial measurements of wind speed and p CO 2 , temperature, salinity, and in-vivo chlorophyll- a fluorescence (chl- a fluo, a proxy of phytoplankton biomass) in surface waters that were obtained during an oceanographic survey in the Argentinian Beagle Channel (subantarctic Atlantic Patagonian) in early fall 2017. The 240 km study transect (centered at 55°S - 67°W) was divided into two zones: (A1) The Beagle Channel innermost portion, semi-enclosed and subject to strong continental influence and (A2) its eastern outlet towards the open Southwest Atlantic. Discrete seawater samples were also collected for apparent oxygen utilization (AOU), nutrients and pH measurements. High-resolution spatial measurements revealed the persistence of p CO 2 below atmospheric equilibrium, increasing in median (interquartile range 25–75%) from 314 μatm in the inner Beagle Channel (A1) to 348 μatm towards the adjacent open sea (A2). A decrease in atmospheric CO 2 sequestration was associated with an increase in water temperature from 9.5 °C to 10.7 °C, salinity from 30.8 to 32.5, and chl- a fluo from 2.24 to 2.91 mg m−3 along the coastal-offshore gradient. Low AOU and nutrient levels were found in regions inside the channel. Indeed, the relationships between CO 2 and temperature or salinity were significantly different from those expected from the theoretical solubility effect, indicating a dominance of metabolic over physicochemical controls on this gas. Moreover, physical factors such as vertical stratification contributed to the variable surface p CO 2 values. These findings reveal the existence of short-scale spatial variability of CO 2 in the Beagle Channel, improving our understanding of the multiple controls on atmospheric carbon sequestration in extensive subpolar continental shelves. • Integrated assessment of metabolic and physicochemical controls on p CO 2. • High short-scale variability of p CO 2 is revealed by the ship measurements. • The Beagle Channel acts as a net CO 2 sink during early fall. • The rate of CO 2 sequestration increases towards the inner regions of the Channel. • The CO 2 surface distribution is dominated by metabolism over physicochemical controls. [ABSTRACT FROM AUTHOR]

The crab Halicarcinus planatus (Fabricius, 1775) is the only member of Hymenosomatidae that inhabits the southern tip of South America, and it is the only decapod species that reproduces twice a year in the Beagle Channel. In this study, we analysed seasonal variations in development duration, body size, biomass (dry weight), and elemental composition (CHN) of larvae from a population living at the southernmost limit of the species' geographic range. Compared to offspring produced in December (early summer), larvae released in August (late winter) were on average larger and heavier, and they showed a higher carbon content (suggesting a larger lipid fraction). This pattern of intraspecific variation in larval size and biomass corresponds with minimum primary productivity in sub-Antarctic regions during winter, suggesting that large winter eggs may represent a reproductive adaptation to a regular pattem of variation in nutritional conditions, including food limitation in winter. As an additional or alternative explanation, also strong salinity fluctuations occurring in summer might reduce larval quality in the December cohort. In conclusion, seasonal variation in larval size and bioniass may be related to variations in nutritional and/or physical factors. [ABSTRACT FROM AUTHOR]