Observations of a distinctive morphotype of killer whale (Orcinus orca), type D, from subantarctic waters

Studies have shown that killer whale (Orcinus orca) communities in high latitudes regularly comprise assemblages of sympatric ‘ecotypes’—forms that differ in morphology, behavior, and prey preferences. Although they can appear superficially similar, recent genetic evidence suggests that breeding is assortative among ecotypes within individual communities, and species-level divergences are inferred in some cases. Here, we provide information on a recently recognized ‘type D’ killer whale based on photographs of a 1955 mass stranding in New Zealand and our own six at-sea sightings since 2004. It is the most distinctive-looking form of killer whale that we know of, immediately recognizable by its extremely small white eye patch. Its geographic range appears to be circumglobal in subantarctic waters between latitudes 40°S and 60°S. School sizes are relatively large (mean 17.6; range 9–35; n = 7), and although nothing is known about the type D diet, it is suspected to include fish because groups have been photographed around longline vessels where they reportedly depredate Patagonian toothfish (Dissostichus eleginoides).     

Out of the Pacific and back again: insights into the matrilineal history of Pacific killer whale ecotypes

Killer whales (Orcinus orca) are the most widely distributed marine mammals and have radiated to occupy a range of ecological niches. Disparate sympatric types are found in the North Atlantic, Antarctic and North Pacific oceans, however, little is known about the underlying mechanisms driving divergence. Previous phylogeographic analysis using complete mitogenomes yielded a bifurcating tree of clades corresponding to described ecotypes. However, there was low support at two nodes at which two Pacific and two Atlantic clades diverged. Here we apply further phylogenetic and coalescent analyses to partitioned mitochondrial genome sequences to better resolve the pattern of past radiations in this species. Our phylogenetic reconstructions indicate that in the North Pacific, sympatry between the maternal lineages that make up each ecotype arises from secondary contact. Both the phylogenetic reconstructions and a clinal decrease in diversity suggest a North Pacific to North Atlantic founding event, and the later return of killer whales to the North Pacific. Therefore, ecological divergence could have occurred during the allopatric phase through drift or selection and/or may have either commenced or have been consolidated upon secondary contact due to resource competition. The estimated timing of bidirectional migration between the North Pacific and North Atlantic coincided with the previous inter-glacial when the leakage of fauna from the Indo-Pacific into the Atlantic via the Agulhas current was particularly vigorous.     

Wild mice provide insights into natural killer cell maturation and memory

The immune system has evolved, and continues to evolve, in response to the selection pressure that infections exert on animals in their natural environments, yet much of our understanding about how the immune system functions comes from studies of model species maintained in the almost complete absence of such environmental selection. The scientific discipline of immunology has among its aims the improvement of human and animal health by the application of immunological knowledge. As research on humans and domesticated animals is highly constrained-ethically, logistically and financially-experimental animal models have become an invaluable tool for dissecting the functioning of the immune system. The house mouse (Mus musculus) is by far the most widely used animal model in immunological research but laboratory-reared mice provide a very narrow view of the immune system-that of a well-fed and comfortably housed animal with minimal exposure to microbial pathogens. Indeed, so much of our immunological knowledge comes from studies of a very few highly inbred mouse strains that-to all intents and purposes-our immunological knowledge is based on enormously detailed studies of very small numbers of individual mice. The limitations of studies in inbred strains of laboratory mice are well-recognized (Pedersen & Babayan 2011), but serious attempts to address these limitations have been few and far between. However, the emerging field of 'ecological immunology' where free-living populations are studied in their natural habitat is beginning to redress this imbalance (Viney et al. 2005; Martin et al. 2006; Owen et al. 2010; Abolins et al. 2011). As demonstrated in the work by Boysen et al. (2011) in this issue of Molecular Ecology, studies in wild animal populations-especially free-living M. musculus-represent a valuable bridge between studies in humans and livestock and studies of captive animals.     

Dental care for a captive killer whale,Orcinus orca

The crowns of several teeth of a captive killer whale, particularly on the mandible, were worn to the level of the pulp cavities by biting a cement structure in the pool. Food plugging partially vacant pulp cavities created intense vascularization, inflammation, and eventually a systemic focus for infection. This trauma correlated with an elevated white blood cell count. Haematology was restored to normal following regular care for the worn teeth. Patent drainage of the pulp cavity was maintained through routine brushing with a large-scale toothbrush. Administration of antibiotics was not necessary in controlling the white blood cell count.     

Salmonella Newport omphaloarteritis in a stranded killer whale (Orcinus orca) neonate

Salmonella enterica serovar Newport (Salmonella Newport) was isolated from multiple tissues in a neonate killer whale (Orcinus orca) that stranded dead in 2005 along the central coast of California, USA. Necrotizing omphaloarteritis and omphalophlebitis was observed on histologic examination suggesting umbilical infection was the route of entry. Genetic analysis of skin samples indicated that the neonate had an offshore haplotype. Salmonellosis has rarely been identified in free-ranging marine mammals and the significance of Salmonella Newport infection to the health of free-ranging killer whales is currently unknown.     

Movement,site fidelity and connectivity in a top marine predator,the killer whale

Movement, site fidelity and connectivity have important consequences for the evolution of population structure and therefore the conservation and management of a species. In this study photographs of naturally marked killer whales collected from sites across the Northeast Atlantic are used to estimate fidelity to sampling locations and movement between locations, expressed as transition probabilities, pt, using maximum likelihood methods. High transition probabilities suggest there is high inter-annual site fidelity to all locations, and large-scale movement between the spawning and wintering grounds of both Norwegian and Iceland stocks of Atlantic herring. There was no evidence of movement between the Norwegian herring grounds and Icelandic herring grounds, or between the mackerel fishing grounds and the herring fishing grounds. Thus the movement of predictable and abundant prey resources can lead to intrinsic isolation in this species We also find movement between the Northern Isles, Scotland and East Iceland. An association network indicates that killer whales predating seals around the Northern Isles, Scotland are linked to the community of killer whales that follow the Icelandic summer-spawning herring. This adds support to existing evidence of a broad niche width in some populations.     

Evolution of population structure in a highly social top predator, the killer whale

Intraspecific resource partitioning and social affiliations both have the potential to structure populations, though it is rarely possible to directly assess the impact of these mechanisms on genetic diversity and population divergence. Here, we address this for killer whales (Orcinus orca), which specialize on prey species and hunting strategy and have long-term social affiliations involving both males and females. We used genetic markers to assess the structure and demographic history of regional populations and test the hypothesis that known foraging specializations and matrifocal sociality contributed significantly to the evolution of population structure. We find genetic structure in sympatry between populations of foraging specialists (ecotypes) and evidence for isolation by distance within an ecotype. Fitting of an isolation with migration model suggested ongoing, low-level migration between regional populations (within and between ecotypes) and small effective sizes for extant local populations. The founding of local populations by matrifocal social groups was indicated by the pattern of fixed mtDNA haplotypes in regional populations. Simulations indicate that this occurred within the last 20,000 years (after the last glacial maximum). Our data indicate a key role for social and foraging behavior in the evolution of genetic structure among conspecific populations of the killer whale.     

Globin genes in Polynesians have many rearrangements including a recently described gamma gamma gamma gamma/.

Rearrangements involving genes of the alpha- and beta-globin loci were frequently detected in DNA from Polynesians. A founder effect and genetic drift occurring 2,000-3,000 years ago as Polynesians migrated eastward across the Pacific is proposed as the likely mechanism for these genetic changes that include deletions or additions of alpha-, gamma-, and zeta-globin genes and an unusual restriction fragment length polymorphism (RFLP) associated with the zeta gene. Preliminary data show different frequencies for gene rearrangements between island groups. Further study of these differences should provide additional information on the prehistory of Polynesians.     

Mitogenomic perspectives into sciaenid fishes' phylogeny and evolution origin in the New World

Sciaenid fishes are widely distributed throughout the coastal waters and estuaries of the world. A total of 23 genera of this family are endemic to the Old World. However, evolutionary relationships among Old World sciaenid fishes and their origin have remained unresolved despite their diversity and importance. Besides, hypotheses that explain the origin and biogeographical distribution of sciaenid fishes are controversial. In this study, the complete mitochondrial genome sequences of seven representative sciaenid species were determined and a well-resolved tree was recovered. This new timescale demonstrated that the sciaenid originated during the late Jurassic to early Cretaceous Period. The estimated origin time of sciaenid fish is 208 Mya, and the origin of Old World sciaenid is estimated at 126 Mya. Reconstruction of ancestral distributions indicated a plesiomorphic distribution and center of origin in the New World, with at least one lineage subsequently dispersed to the Old World. Moreover, we conclude that the common ancestors of Old World sciaenid fishes were derived from species of New World.     

Ecological,morphological and genetic divergence of sympatric North Atlantic killer whale populations

Ecological divergence has a central role in speciation and is therefore an important source of biodiversity. Studying the micro‐evolutionary processes of ecological diversification at its early stages provides an opportunity for investigating the causative mechanisms and ecological conditions promoting divergence. Here we use morphological traits, nitrogen stable isotope ratios and tooth wear to characterize two disparate types of North Atlantic killer whale. We find a highly specialist type, which reaches up to 8.5 m in length and a generalist type which reaches up to 6.6 m in length. There is a single fixed genetic difference in the mtDNA control region between these types, indicating integrity of groupings and a shallow divergence. Phylogenetic analysis indicates this divergence is independent of similar ecological divergences in the Pacific and Antarctic. Niche‐width in the generalist type is more strongly influenced by between‐individual variation rather than within‐individual variation in the composition of the diet. This first step to divergent specialization on different ecological resources provides a rare example of the ecological conditions at the early stages of adaptive radiation.     

Ovarian cycle approach by rectal temperature and fecal progesterone in a female killer whale,Orcinus orca

This study aimed to validate the measurements of body temperature and fecal progesterone concentrations as minimally invasive techniques for assessing ovarian cycle in a single sexually mature female killer whale. Rectal temperature data, fecal and blood samples were collected in the dorsal position using routine husbandry training on a voluntary basis. The correlations between rectal temperature and plasma progesterone concentration and between fecal and plasma progesterone concentrations were investigated. Fecal progesterone metabolites were identified by a combination of high‐performance liquid chromatography and enzyme immunoassay. Plasma progesterone concentrations (range: 0.2–18.6 ng/ml) and rectal temperature (range: 35.3–35.9°C) changed cyclically, and cycle lengths were an average (±SD) of 44.9±4.0 days (nine cycles) and 44.6±5.9 days (nine cycles), respectively. Rectal temperature positively correlated with the plasma progesterone concentrations (r=0.641, P<0.01). There was a visual trend for fecal progesterone profiles to be similar to circulating plasma progesterone profiles. Fecal immunoreactive progestagen analysis resulted in a marked immunoreactive peak of progesterone. The data from the single killer whale indicate that the measurement of rectal temperature is suitable for minimally invasive assessment of the estrous cycle and monitoring the fecal progesterone concentration is useful to assess ovarian luteal activity. Zoo Biol 30:285–295, 2011. © 2010 Wiley‐Liss, Inc.