Sei Whales Research Articles

Upwellings, canyons and whales: An important winter habitat for balaenopterid whales off Mauritania, northwest Africa

The aim of this study was to identify critical habitats for baleen whales in the Mauritanian upwelling zone using data collected from a platform of opportunity: a 60 day geophysical survey approximately 100km southwest of Cap Blanc, Mauritania in winter (2012/13). The bathymetry of the 5,500km2 study area was complex, including parts of the Cap Timiris Canyon system. Large whales, including sei and blue whales, accounted for 70% of the 238 cetacean sightings. Species identification was often problematic, especially in the case of balaenopterid whales, so data for all whales of this genus were pooled for the estimation of abundance and distribution. Spatial modelling was applied to estimate abundance and to plot a predicted density map of balaenopterid whales. Depth and the chlorophyll-a concentration when at its peak (in the previous September) were significant predictors of whale density. Point abundance in the study area was estimated at 272 whales (95% CI 265–279) and density was highest in the depth range 500–2,250m near to the canyon system (6.18 whales/100km2 , 95% CI 6.03–6.51). Steep seabed topography created by canyons running off the shelf edge, together with the strong upwelling system, probably create optimal habitats for the euphausiid prey of sei and blue whales. Sei whales were observed skim-feeding at dawn or dusk on seven occasions; in one sighting an aggregation of 18 skim-feeding sei whales were observed. The high density of these baleen whale species in such a highly productive area and direct observation of feeding behaviour in sei whales, provides evidence of feeding during the winter breeding season, when they have previously been presumed to feed less. This study demonstrates the potential value of collecting further data on seismic survey vessels and would improve understanding of cetacean ecology in remote and under-explored regions.

Reencounter with the past: occurrence of sei whale (Balaenoptera borealis) in an old hunting area in the south-eastern Pacific Ocean

The sei whale (Balaenoptera borealis) was intensively exploited throughout its range, with about 110.000 individuals hunted by pelagic fleets in Antarctic waters between 1960 and 1970. In addition, basic information on its distribution, migratory routes, and feeding grounds in the southeastern Pacific, has been poorly documented. In the case of Chile, recent information consists mainly of accidental records. This research presents the first sei whale photo-identification catalog for south-central Chile. From November 2019 to January 2020, 88 individuals were recorded from land-based and boat surveys at Caleta Chome. Of these, 12 individuals were photo-identified through scars or distinctive notches in the dorsal fins. The peak of sightings occurred during December 2019; two individuals were sighted on more than one occasion.

Cue rates and surfacing characteristics of sei whales (Balaenoptera borealis) in the Falkland Islands

The cue rate (CR: blows per whale per hour), surfacing characteristics and swim speeds of sei whales (Balaenoptera borealis) were quantified fromfocal follows carried out at Berkeley Sound (East Falkland) between January and May 2017 and off the west coast of West Falkland betweenFebruary and April 2018. In Berkeley Sound, focal follows were conducted from Cape Pembroke lighthouse and from a small boat. In West Falklandall focal follows were conducted from a yacht. Thirty-seven focal follows of sei whale individuals or groups (2–5 individuals) were analysed toproduce CRs ranging from 21.99 to 46.73, with a mean of 31.46 (SD = 5.12). There was no significant difference in the CRs observed from shorevs. boat platforms or between the two study areas. Maximum submergence times exceeding 13min were recorded from both individuals and groups.The durations of 51 whale surfacing events had a mean of 6.4s (SD = 1.7). The average swim speed during boat-based sei whale focal follows was5.7kmh−1. The inter-breath intervals (IBIs) recorded from 13 solitary individuals ranged from 77.2 to 180.1s, with an overall mean of 118.6s (SD= 137.6). A combined approach incorporating IBI parameters and sequence pattern was used to classify 270 IBIs into surface dives (mean = 37.2s),intermediate dives (mean = 113.7s) and true dives (mean = 332.6s). Individuals showed marked variation in dive pattern, with some exhibitingclear cycles of true dives interspersed with surface bouts while others routinely took intermediate-duration dives interspersed by single surfacings.Sei whales in Berkeley Sound exhibited a higher proportion of surface dives than whales in West Falkland, and those surface dives were of lowermean and median IBI. Individual sei whales had surface bouts comprising a mean of 3.8 blows and a mean IBI of 33.4s. These are the firstquantifiable data on surfacing-dive patterns and CRs for sei whales in the Falkland Islands and across the wider range of the species. The data haveconservation and management relevance, including addressing availability bias for line transect and cue count abundance estimates, incorporationinto vessel strike modelling, and understanding foraging behaviour.

Cetacean diversity of the eastern South Atlantic Ocean and Vema Seamount detected during a visual and passive acoustic survey, 2019

Abstract Cetaceans in the eastern South Atlantic Ocean are poorly studied. We present results from a 2 week ship-based survey from Cape Town to Vema Seamount (980 km to the west) during October–November 2019, including visual and towed-hydrophone observations from the vessel, and 10 days of acoustic monitoring on the seamount. Fifty-two hours of visual surveys resulted in 39 encounters of whale groups including seven of humpback, six of fin and one sei whale, as well as four unidentified baleen whales, 18 unidentified balaenopterid whales and four unidentified odontocetes. Two humpback whales at the seamount were engaged in possible feeding behaviour. A large aggregation of mostly fin whales was observed near the continental shelf edge (22 encounters over a 70 × 50 km2 area, six fin, one sei whale, 15 not confirmed to species), an historic whaling ground for both fin and sei whales. Towed-hydrophone data (78.7 h) detected five groups of sperm whales, 45 of delphinids, one beaked whale and no Kogiids. Acoustic data from the seamount detected calls from several baleen whale species including humpback whale non-song calls, Antarctic minke ‘bioduck’ calls, sei whale down-sweep calls and a likely Bryde's whale call. Two call types could not be assigned to species, including the most detected – a simple frequency-modulated call with peak power around 130 Hz. This study contributes to an improved understanding of cetacean occurrence in the eastern South Atlantic Ocean and highlights the need for more research to improve identification of cetacean vocalizations in the region.

Evidence of resource partitioning between fin and sei whales during the twentieth-century whaling period

Investigating resource partitioning of marine predators is essential for understanding coexistence of sympatric species and the functional role they play in marine ecosystems. Baleen whales are a key component of sub-Antarctic ecosystems, foraging predominantly on zooplankton and small forage fish. During the twentieth century, baleen whales were unsustainably exploited across the Southern Ocean. Within the exclusive economic zone of South Georgia and the South Sandwich Islands (SGSSI EEZ) in the South Atlantic, approximately 98,000 fin whales (Balaenoptera physalus) and 16,000 sei whales (B.borealis) were harvested. Despite both species historically occurring in high numbers and feeding in sub-polar waters, little is known about the mechanisms of coexistence. Here, by measuring stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in archived baleen plates and analysing historic catch data, we investigate resource partitioning of fin and sei whale during the commercial whaling period. Temporal and spatial occupancy at SGSSI EEZ (inferred from whaling catches that occurred between 1904 and 1976), alongside historic stomach contents (from the literature), and δ13C and δ15N results (observed in this study), suggests that despite using a common prey resource there was limited overlap in isotopic niches between the two species, with sei whales using SGSSI waters later in the season and for a shorter period than fin whales. We hypothesise that the isotopic differences were most likely due to sei whales foraging at lower latitudes prior to arrival at SGSSI. Our data provide novel insight into how two sympatric whale species co-occurring at SGSSI during the commercial whaling period may have partitioned resources and provide a potential ecological baseline to assess changes in resource use in recovering whale populations.

Mid-frequency song and low-frequency calls of sei whales in the Falkland Islands.

Although sei whales (Balaenoptera borealis) are distributed throughout the globe, their behaviour and vocal repertoire are poorly described. We used passive acoustic monitoring to describe the vocal behaviour of sei whales in the Falkland Islands, between December 2018 and April 2019. We isolated more than 2000 low-frequency calls for manual classification, of which 510 calls with high signal-to-noise ratio were quantitatively measured. Five categories of stereotyped call types in the 15-230 Hz range were described, some with multiple subcategories. These included some similar to previously described calls (e.g. downsweeps), but others that were novel in acoustic structure and frequency band. In the mid-frequency range, we documented a highly stereotyped, hierarchically structured and rhythmically repetitive song display. Songs were arranged in phrases with a structure composed of repetitive sub-phrases, and a diverse variety of sounds in the 1-5 kHz range. Singing commenced in late February, despite the presence of whales and calls since early December, and continued through April. These acoustic properties and behavioural characteristics indicate that this is likely a male breeding display similar to songs and singing of other balaenopterids. This is the first detailed description of a song display for sei whales, highlighting the importance of the Falkland Islands.

Distribution of blue and sei whale vocalizations, and temperature - salinity characteristics from glider surveys in the Northern Chilean Patagonia mega-estuarine system

Northern Chilean Patagonia is a mega-estuarine system where oceanic waters mix with freshwater inputs in the coastal fjords, channels and gulfs. The aim of this study was to examine the distribution of blue and sei whales with respect to oceanographic conditions of the study area from the estuarine inner sea to the outer ocean. Ocean gliders were used, mounted with a hydrophone to determine acoustic presence of whales (Southeast Pacific and Antarctic blue whale song calls, and blue whales D-calls; sei whale downsweeps and upsweeps), and a temperature and salinity instrument. Four glider deployments were carried out in April 2018 and April-June 2019 navigating a total of 2817 kilometers during 2110 hours. To examine interannual variation, the average percentage of day with presence of calls was compared between years using the adjusted p-values for one-way ANOVA and descriptive statistics. To examine spatial variation between the hourly acoustic presence of blue whales and sei whales and temperature and salinity conditions, Generalized Linear Models (GLMs) were used. Salinities were higher in 2019 compared to 2018. Southeast Pacific blue whales produced song calls throughout the study area in both years, across estuarine and oceanic areas, but percentage of day with presence was higher in 2019 vs 2018. Percentage of day with presence of D-calls was similar between years, but higher in oceanic areas during both study periods. In contrast, the spatial pattern of sei whale acoustic presence was ambiguous and interannual variability was high, suggesting that sei whales preferred estuarine areas in 2018 and oceanic areas in 2019. We discuss possible explanations for observed acoustic presence in relation to foraging behavior and prey distribution.

Evidence of Large Whale Socio-Sexual Behavior in the New York Bight

Large whales, including the endangered sei whale (Balaenoptera borealis), sperm whale (Physeter macrocephalus), and North Atlantic right whale (Eubalaena glacialis), are known to occur in the New York Bight. However, relatively little data exist on social behavior typical of these species in the area. The U.S. Mid-Atlantic has traditionally been considered a large whale migratory corridor with few surveys documenting social dynamics of whale presence in these waters. To better understand the occurrence, distribution, abundance, and behavior of these species for management and conservation planning, monthly line-transect aerial surveys were conducted over a 3-year period from March 2017 to February 2020. During these surveys, three noteworthy socio-sexual behavior events were observed and photographed within groups of sei whales (April 2019), sperm whales (September 2019), and right whales (December 2019). Events included what could be either non-reproductive sexual behavior (socio-sexual behavior) or sexual behavior (copulation) among conspecifics, including mirror pair swimming, lateral and vertical presenting, and belly to belly contact. During all three events, groups were highly active at the surface, frequently and quickly changing speed and direction, and animals were predominantly less than one body length apart from other conspecifics in the group. All species were recorded rolling onto their sides and/or back while at or near the surface. Open mouth display occurred in the North Atlantic right whale event. Though copulation is unlikely to have transpired during the sperm whale event and could not have occurred during the right whale event due to the identification of same-sex individuals, it cannot be ruled out as the impetus for the sei whale event. These observations begin to describe the relative importance of the New York Bight as more than a migratory corridor and suggest that additional behaviorally focused data collection be incorporated into future surveys.

Monitoring cetacean occurrence and variability in ambient sound in Scottish offshore waters

The characterisation of marine soundscapes allows observation of spatiotemporal distribution of vocalising species and human activities, which can inform an assessment of their interactions. Such data are important for monitoring the ecological status of marine habitats. The Scottish Atlantic Frontier is an important habitat for a variety of cetacean species. Historic whaling has heavily impacted several species inhabiting these waters and current comprehensive information about seasonal occurrence and distribution is lacking for all species. This study presents year-round passive acoustic monitoring data from ten sites in this understudied region. The three most offshore sites were examined for baleen whale vocalisations, and four species were regularly detected. Fin whale detections peaked from October to January and were at their lowest during May and June. Humpback whale song was detected as early as January but showed a strong seasonal peak in March and April. In contrast, minke whales were detected regularly throughout the year but with a peak in detections from October to November, when sei whales were also detected. All monitoring sites showed frequent occurrence of odontocete echolocation clicks and whistles. Comprised mainly of delphinid vocalisations, whistles and clicks were detected on an almost-daily basis among the offshore sites, with a slight reduction in detections from May to July particularly among the more inshore sites. Ambient sound levels (root-mean-square sounds pressure level; SPL) varied by site and season in relation to species presence, anthropogenic contributions, and environmental conditions. Monthly median SPL across the array varied up to 18 dB within 1/3-octave bands. Throughout the year, variability in median SPL was lowest in the higher frequency bands (>10 kHz), while highest variability was found between January to July in specific lower frequency bands (<1 kHz). Results from this study demonstrate the value of passive acoustic data in providing novel baseline information about cetacean occurrence and distribution in Scottish offshore habitats where data are limited and outdated. The results will feed into statutory reporting on underwater noise, support the identification and designation of future marine protected areas for cetaceans, and help guide management of future human-marine mammal interactions in Scottish offshore waters.

Historical occurrence of whales in Scottish Waters inferred from whaling records

Abstract Archived logbooks detailing landings at Scottish shore‐based whaling stations between 1903 and 1951 were used to map whale catch locations. Historical distribution and occurrence are inferred and summary statistics on total landings are updated for blue (Balaenoptera musculus), fin (Balaenoptera physalus), humpback (Megaptera novaeangliae), North Atlantic right (Eubalaena glacialis), sei (Balaenoptera borealis) and sperm (Physeter macrocephalus) whales: a total of 9,996 whales were caught during this period, which is 3.7% higher than previously reported and 25% higher for blue whales. The most frequently caught species were fin and sei whales. Whaling off Scotland in the 1920s contributed to the likely extinction of right whales in the eastern North Atlantic. Blue whales, once regularly hunted to the west of Scotland, are now rarely documented there and North‐east Atlantic whaling appears to have had a significant and lasting impact on sei whales. Analysis of whaling effort indicates that catch rates remained high despite the depletion of some species. This, may be a consequence of two features of Scottish shore‐based whaling: (1) the mixed species catch composition; and (2) the catching of whales as they migrated through Scottish waters. The findings of this study highlight the historical significance of the shelf‐seas around Scotland as a habitat for some species, which was not apparent from previous studies. These results can inform where there may be potential for the recovery of some species in the future. Current major threats in the North Atlantic include entanglement, ship strike and displacement owing to the effects of climate change. The baseline and historical information on distribution and seasonal occurrence examined here is important for informing spatial and temporal measures to reduce these threats. If populations are to recover post‐whaling there is an increasing need to reduce threats such as ship strikes and entanglement, whose magnitude is proportional to whale density.

Anatomical Mechanism for Protecting the Airway in Whales Involves Interlocking the Larynx

The mammalian respiratory and digestive tracts are configured to enable simultaneous function of both systems, while preventing accidental choking on food. This protection is critical in mysticetes (baleen whales), especially as feeding involves large pressures and potential inundation of water.Dissections were performed on 43 specimens representing 8 mysticete species: fin, blue, sei, minke, humpback, gray, right, and pygmy right whales. 36 specimens were necropsied as whole carcasses, 5 were obtained as whole heads, 2 were whole fetuses. All were recovered post mortem from US beach strandings. Dissections focused on hyolaryngeal anatomy, soft palate, and nasopharynx.Results indicate that the mysticete larynx retains an intranarial position during feeding, swallowing, breathing, and sound production. The soft palate forms a muscular ring that keeps the larynx interlocked into the nasopharynx. The epiglottis overlaps the soft palate extensively, nesting rostrally over a shelf that forms a pocket lined by nasopharyngeal pits. The soft palate articulates tightly with the epiglottic base, and lateral portions arc around larynx to meet in the caudal midline. Posteriorly, the soft palate forms another smaller shelf that interlocks with the caudally curling paired corniculate cartilages. These two points of interlocking keep the larynx intranarially positioned during deglutition. The paired lateral food channels (piriform sinuses) pass on either side of the epiglottis and corniculate cartilages and unite caudally to form the esophagus. Food can easily pass around the interlocked larynx using these lateral food channels.Suprahyoid muscles elevate the oral floor, squeezing out water and pushing the tongue towards the oral roof to compress the food bolus and force it through the oropharyngeal inlet. The oropharyngeal inlet appears regulated by muscles that likely relax to allow dilation. Suprahyoid muscles also ensure the larynx‐soft palate interlock, as the epiglottis is pushed rostrally to maximally overlap the soft palate. Food encountering the interlocked soft palate‐epiglottis is diverted laterally into paired lateral food channels. Infrahyoid muscles retract the larynx caudally, returning it to its rest position with moderate soft palate overlap. Continued contraction would allow the long epiglottis to slide along its overlap with the soft palate, giving mobility to enlarge the depth of the lateral food channels if necessary, without unlocking the larynx. This interlock preserves the protection of the airway.Unlocking the epiglottis necessitates elevating the soft palate while withdrawing the epiglottis. This may occur to channel air into the oral cavity for bubble cloud production. However, the larynx is at risk of inundation from water in this position, as it forms a very poor seal with the corniculate cartilages and their flexible flaps. The rigid epiglottis could not be folded caudally manually to meet the corniculates. No muscles were noted that could retract the epiglottis towards the corniculates. Similarly, no muscles were found that could rigidify the corniculate flaps or cause them to seal in opposition. Therefore, the sealing mechanism of the larynx is limited to opposition of the arytenoid cartilages supporting the U‐shaped vocal fold.

Feeding habits of Bryde's and sei whales in the western North Pacific inferred from stomach contents and skin stable isotope ratios

Gathering information on the diet composition of baleen whales at different temporal scales is useful for investigating their feeding habits. Bryde's whales (Balaenoptera edeni) and sei whales (B. borealis) are known to feed on crustaceans and pelagic fish in their western North Pacific feeding grounds; however, their feeding habits before arriving in the feeding area are not known. This study clarified the feeding habits of these two whale species by simultaneously analyzing nitrogen and carbon stable isotope ratios and stomach contents of individuals captured in the western North Pacific in 2015 and 2016. A stable isotope Bayesian mixed-model was used to estimate prey composition. The results showed clear temporal differences in the feeding habits of both whales. Specifically, Bryde's whales fed primarily on krill and pelagic and mesopelagic fishes as they migrated northwards, and then fed exclusively on krill during the summer. Sei whales fed on copepods when they arrived in the subarctic region before shifting to pelagic fish species in the summer. The differences in the feeding habits of these two whale species are attributed to their latitudinal segregation and the availability of prey species, especially in sei whales, which migrate to the subarctic region where copepods are abundant.

Alongside but separate: Sympatric baleen whales choose different habitat conditions in São Miguel, Azores

Fin whales and sei whales are two migratory baleen whale species sighted every year across the waters of the Azores. Improved understanding of the ecological niche and habitat requirements of these baleen whales is needed to identify persistent or predictable oceanographic events that may set the time of their migration, as well as local or ephemeral oceanographic features that may aggregate their prey in a particular area. In dynamic environments such as the open ocean, mesoscale and submesoscale features can become decisive to determine the distributions of highly mobile species such as baleen whales. In this study, we analyse the habitat preferences of fin whales and sei whales around São Miguel Island (Azores) using environmental variables at different temporal and spatial scales. For both species, model results showed a clear influence of variables linked with primary production and therefore, prey availability; as well as a noticeable preference for oceanographically dynamic areas which directly affect distribution and aggregation of prey. Those environmental choices may indicate different levels of foraging habitat use for both species. Differences were found between the species, highlighting preferences for colder waters in fin whales and areas with stronger sea surface temperature gradients in sei whales. Model results obtained for fin whales were similar with those previously published for blue whales, suggesting that both species make similar use of the waters around São Miguel, often foraging during the migration across these waters. Results for sei whale, however, emphasize dynamic variables, indicating that travelling may prevail over feeding behaviour during their migration by the Azores.

Estimating proportions of identical twins and twin survival rates in cetaceans using fetal data

AbstractMultiplet pregnancies are rare in cetaceans, and live‐born multiple births even rarer. We used whaling data collected from pregnant females and held by the International Whaling Commission to examine multiplets in 16 cetacean species, finding that 0.87% (2,197 out of 252,651) of pregnancies included multiple fetuses, including 12 instances of five or more fetuses in five different species, all rorquals. For six species, we estimate the proportion of twins that are identical using Weinberg's differential rule. Identical twins are less common than fraternal twins in all species (4%–34%) except humpback whales (57%). To infer survival rates of twins to term, we fitted models to the proportion of twins by fetal length, finding that the probability of surviving twins declined exponentially to near zero with increasing fetal length for sei, fin, and blue whales; but not for sperm, humpback, and Antarctic minke whales. Because some fetuses may be missed at smaller lengths, we repeated this analysis excluding fetuses shorter than 2 ft (61 cm), finding that twin survival declined with increasing fetal length for sei, fin, blue, and Antarctic minke whales. We conclude that few multiple pregnancies (<1 in 500) end in live birth, and even these pregnancies experience high mortality after birth.

Characteristics of Whale Müller Glia in Primary and Immortalized Cultures.

Müller cells are the principal glial cells in the retina and they assume many of the functions carried out by astrocytes, oligodendrocytes and ependymal cells in other regions of the central nervous system. Müller cells express growth factors, neurotransmitter transporters and antioxidant agents that could fulfill important roles in preventing excitotoxic damage to retinal neurons. Vertebrate Müller cells are well-defined cells, characterized by a common set of features throughout the phylum. Nevertheless, several major differences have been observed among the Müller cells in distinct vertebrates, such as neurogenesis, the capacity to reprogram fish Müller glia to neurons. Here, the Müller glia of the largest adult mammal in the world, the whale, have been analyzed, and given the difficulties in obtaining cetacean cells for study, these whale glia were analyzed both in primary cultures and as immortalized whale Müller cells. After isolating the retina from the eye of a beached sei whale (Balaenoptera borealis), primary Müller cell cultures were established and once the cultures reached confluence, half of the cultures were immortalized with the simian virus 40 (SV40) large T-antigen commonly used to immortalize human cell lines. The primary cell cultures were grown until cells reached senescence. Expression of the principal molecular markers of Müller cells (GFAP, Vimentin and Glutamine synthetase) was studied in both primary and immortalized cells at each culture passage. Proliferation kinetics of the cells were analyzed by time-lapse microscopy: the time between divisions, the time that cells take to divide, and the proportion of dividing cells in the same field. The karyotypes of the primary and immortalized whale Müller cells were also characterized. Our results shown that W21M proliferate more rapidly and they have a stable karyotype. W21M cells display a heterogeneous cell morphology, less motility and a distinctive expression of some typical molecular markers of Müller cells, with an increase in dedifferentiation markers like α-SMA and β-III tubulin, while they preserve their GS expression depending on the culture passage. Here we also discuss the possible influence of the animal’s age and size on these cells, and on their senescence.

Gargantuan whales more manoeuvrable than they ought to be

A fighter pilot wouldn't enter into a dogfight in a Boeing 747. They'd opt for something more nimble, like a Eurofighter Typhoon or Lockheed Raptor. But immense baleen whales don't have the privilege of shrinking to pursue the smallest and quickest fish and krill to dine upon. Yet somehow, they manage to overwhelm their agile victims. The irony is that the massive mammals only became so large because they could capture colossal quantities of food in a single gulp. So just how manoeuvrable are these extraordinary creatures, and how does that versatility vary from the relatively diminutive minke whales (5.0 m, 2000 kg) to the truly gargantuan blue whales (30 m, 185,000 kg)? Over the past 10 years, Jeremy Goldbogen's lab at Stanford University, USA, has built up an extensive network of 25 collaborators from all across the USA, Greenland, Denmark, The Netherlands, South Africa and the Falkland Islands, attaching movement sensors with magnetometers and depth gauges to 280 whales – including minke, Bryde's, grey, humpback, sei, fin and blue whales – to find out how their movements varied from the smallest to the largest.Describing the experience of tagging a whale, Paolo Segre (Stanford University) says, ‘It's incredible. As they rise out of the water, you realize how large they are’. And retrieving the sensitive tags is every bit as nerve-wracking. ‘When you throw something delicate and expensive into the ocean, there's a reasonable chance that you won't get it back, so every time we recover a tag it's a big deal’, he smiles. In addition, the team took aerial photographs of 93 animals to calculate their sizes.After successfully collating 4037 h of whale movements over a 10-year period, Segre recalls analysing the daunting dataset, breaking the movements down into fast sprints, flips and somersaults, rolls and turns, while also calculating the whales’ swimming speeds. After months of painstaking calculation, Segre eventually identified over 625,000 manoeuvres before plotting the accelerations experienced by the animals against their masses to find out which whales were the most and least manoeuvrable.Not surprisingly, the blue whales were the most cumbersome, manoeuvring more slowly than the smaller and more sprightly species. However, when the team compared the blue whale's movements with their expectations – based on the animals’ colossal size – they found that the blue whales were accelerating faster than had been thought possible. And, when they checked the turn speeds and somersault accelerations of the other large whales, they saw that these animals were also outperforming the scientists’ expectations. The largest whales seemed to be depending on their flippers and spines – which bend and arch – to accelerate their flips, while using their flippers like aeroplane wings to compensate for their size and turn faster.Segre's analysis also showed that the humpbacks’ scalloped flippers helped them to roll faster than the other species. However, slow-moving grey whales, which roll onto their sides to suck food from the bottom of shallow inlets, depended on their flukes (tail fins) to tip over onto their sides, tucking their flippers against their bodies. And the humpbacks, which dine on nimble krill, were more lithe, surging and tumbling faster than the whales that feast on fish, suggesting that diet influences the animals’ manoeuvrability.So larger baleen whale species are less agile than their smaller cousins, but blue whales and fin whales are more agile than they should be for their size, taking advantage of their flippers and flukes for harder turns and flips than might otherwise be possible. ‘Large whales play to their strengths to overcome the limitations of their body size’, says Segre.

Effect of Sei and Fin whale Müller glia in the survival and neurite growth of RGCs in vitro

AbstractPurposeMüller cells are crucial in retinal homeostasis. In zebrafish and lower vertebrates, spontaneous retinal regeneration was observed. In the mammalian retina, there is no such evidence. However, recent studies have been demonstrated that Müller cells promote the survival and the neurite outgrowth of RGCs in vitro. Here, the effect of Müller cells from two of the largest mammals in the world, Fin and Sei whales, was analyzed on RGCs survival and neurite outgrowth.MethodsThe retinas of beached Balaenoptera physalus and Balaenoptera borealis whales, 24 hr post‐mortem, were studied. Cultures of Müller cells were grown and, once whale Müller cells reached confluence, adult rat RGCs were seeded on Müller cells. The cells were cultured during six days. The number and length of the neurites of the RGCs were quantified. The conditioned media (CM) from whale Müller cells was analysed by mass spectrometry to identify and quantify proteins. Results were compared to the CM from pig Müller cells. NELL2, SEMA3F, CD56, NRCAM, OGN and PEDF were selected as candidate factors to promote neurite outgrowth and tested in pure rat RGCs cultures.ResultsRGCs survival increased 60% when cultured with whale Müller cells. The length of the neurites (>200 μm) increased 90% and the length of the longest neurites (>1000 μm) increased more than 500%. Proteomic analysis from whale Müller cells CM showed that the function of the 10% of the most represented proteins detected was related to neurite outgrowth, compared to only 2% of the proteins in pig CM. The selected proteins induced an increase in the percentage of RGCs with long neurites (>200 μm) and an increase of 200% in RGCs with very long neurites (>1000 μm).ConclusionsWhale Müller cells increase RGCs neurite growth, suggesting that whale Müller cells secrete a combination of neurotrophic factors promoting regeneration of RGCs. Besides, the selected proteins from the CM increase neurite outgrowth, confirming the capacity of the factors secreted by whale Müller cells to regenerate RGCs.Supported by ELKARTEK (KK‐2019/00086), MINECO‐Retos (PID2019‐111139RB‐I00) Grupos UPV/EHU (GIU2018/50).

Morphological characterization of the whale retina

AbstractPurposeThe retina of the largest adult mammal in the world, the whale, was analysed morphologically by immunohistochemistry. The eye of these aquatic mammals have been poorly studied, thus, the aim of this study was to examine the different neurons and glial cells in the whale retina using a range of molecular markers.MethodsThe eyes of beached whales (n = 2, Balaenoptera physalus and Balaenoptera borealis) were obtained, and after dissection and fixation of the retinas, whole‐mount preparations and cryostat sections were immunostained. The neurons and glial cells in these tissues were analysed using different antibodies to label RGCs, photoreceptors, bipolar cells, amacrine cells, microglia, astrocytes and Müller cells. Thioflavin S was also used to label misfolded proteins.ResultsMost of the molecular markers used labelled their specific structures in the whale retinas as in terrestrial mammalian retinas. However, whale cones do not express cone markers (M/L and S opsin, and cone arrestin). It is important to highlight the large size of whale RGCs and there is a heterogeneity in NFs expression. It is also noteworthy that intrinsically photosensitive RGCs labelled with melanopsin form an extraordinary network in the whale retina, where these cells are more abundant in the centre, and different subtypes of melanopsin positive cells were identified. Thioflavin S is weakly labelled of some RGCs in a punctuate pattern and it could easily represent an early sign of neurodegeneration. In addition, degenerative neuritic beading has been observed in RGCs when the retina was analysed after 48 hr postmortem.ConclusionsIn conclusion, there are some notable differences in the retina of the whales when compared with that of terrestrial mammals. Their rod‐monochromatic vision due to an evolutionary loss of cone photoreception and the well‐developed melanopsin‐positive RGCs network could in part be responsible for their perception in the deep sea.Supported by ELKARTEK (KK‐2019/00086), MINECO‐Retos (PID2019‐111139RB‐I00) Grupos UPV/EHU (GIU2018/50).

Characterization of primary and immortalized whale Müller Glial cells

AbstractPurposeMüller cells are the principal glia of the retina, expressing growth factors, neurotransmitter transporters and antioxidant agents with an important role in preventing excitotoxic damage to neurons. Although fish Müller cells can be transformed into neurons, this has never been described in mammals. In the present study, whale Müller cells were cultured and immortalized, with the aim of analysing the molecular characteristics as well as the division rate in vitro of primary and immortalized whale Müller cells.MethodsThe eye of Balaenoptera borealis was obtained, retina was isolated and Müller cells were cultured. Half of the cultures were immortalized with simian virus 40 T‐antigen. Primary as well as immortalized Müller cultures were grown until primary cells reached senescence. Specific Müller molecules, dedifferentiated, neuronal precursors and neuronal markers were studied in both primary and immortalized cells. Ultrastructural morphology was also studied by scanning electron microscopy (SEM). In addition, the proliferation kinetics (time between divisions, percentage of dividing cells and division duration) was analyzed by time‐lapse. Karyotype characterization was performed in immortalized whale Müller cells.ResultsWhale Müller cells were immortalized after 10 passages and approximately 2 months of culturing. Müller markers were preserved, while expression of dedifferentiation markers was observed after the 5th passage. At high passages, neuronal precursor markers were weakly expressed. In addition, immortalized cells were stained extensively with neuronal markers. Immortalized Müller immunostaining and SEM revealed heterogeneous cell morphologies due to changes in the cytoskeleton. The proliferation kinetics demonstrated that primary whale Müller cells divide every 23 hr, approximately, while after the immortalization process the time between divisions increased to 29 hr.ConclusionsIn conclusion, we have generated a cell line from whale Müller cells that maintains primary Müller characteristics but presents a partially dedifferentiated state. In addition, we present a detailed analysis of the rate of cell division during the immortalization process.Supported by ELKARTEK KK‐2019/00086, MINECO‐Retos PID2019‐111139RB‐I00, Grupos UPV/EHU GIU2018/50.

Polychlorinated biphenyl (PCB) concentrations and profiles in marine mammals from the North Atlantic Ocean

Polychlorinated biphenyls (PCBs) can provide crucial information into the bioaccumulation and biomagnification of POPs in marine mammals. Muscle tissue samples were obtained for detailed PCB congener specific analysis of all 209 PCBs in 11 species of marine mammals stranded across the coast of the UK between 2010 and 2013. At least 145 PCB congeners were found in each individual. The highest concentrations of PCBs were recorded in a killer whale (318 mg/kg lipid) and the highest toxic equivalent in a Risso's dolphin (1687 pg/g TEQ2005 wet). Concentrations of PCBs in the majority of samples exceeded toxic thresholds (9 mg/kg lipid) for marine mammals, highlighting the health risk they face from PCB exposure. Many PCB profiles did not fit typical ‘Aroclor’ signatures, but instead indicated patterns of congeners that are resistant to biotransformation and elimination. However, this study identified a novel PCB signature in a sei whale that has not yet been previously observed in marine mammals. The whale had a PCB profile that included lighter and inadvertent PCB congeners such as PCB 11, suggesting that the main source of exposure was through atmospheric deposition, rather than terrestrial discharges. Seven subsamples were chosen for chiral analysis of PCB 95, 136 and 149. The enantiomer fractions (EFs) of C-PCBs 95 and 149 were non racemic suggesting there may be enantiomer selective metabolism in marine mammals. Although there has been a shift in the literature towards emerging pollutants, this study acts as a stark reminder that PCBs continue to pose a significant risk to wildlife.