Evolutionary impacts differ between two exploited populations of northern bottlenose whale (Hyperoodon ampullatus)

Interpretation of conservation status should be informed by an appreciation of genetic diversity, past demography, and overall trends in population size, which contribute to a species' evolutionary potential and resilience to genetic risks. Low genetic diversity can be symptomatic of rapid demographic declines and impose genetic risks to populations, but can also be maintained by natural processes. The northern bottlenose whale Hyperoodon ampullatus has the lowest known mitochondrial diversity of any cetacean and was intensely whaled in the Northwest Atlantic over the last century, but whether exploitation imposed genetic risks that could limit recovery is unknown. We sequenced full mitogenomes and genotyped 37 novel microsatellites for 128 individuals from known areas of abundance in the Scotian Shelf, Northern and Southern Labrador, Davis Strait, and Iceland, and a newly discovered group off Newfoundland. Despite low diversity and shared haplotypes across all regions, both markers supported the Endangered Scotian Shelf population as distinct from the combined northern regions. The genetic affinity of Newfoundland was uncertain, suggesting an area of mixing with no clear population distinction for the region. Demographic reconstruction using mitogenomes suggests that the northern region underwent population expansion following the last glacial maximum, but for the peripheral Scotian Shelf population, a stable demographic trend was followed by a drastic decline over a temporal scale consistent with increasing human activity in the Northwest Atlantic. Low connectivity between the Scotian Shelf and the rest of the Atlantic likely compounded the impact of intensive whaling for this species, potentially imposing genetic risks affecting recovery of this population. We highlight how the combination of historical environmental conditions and modern exploitation of this species has had very different evolutionary impacts on structured populations of northern bottlenose whales across the western North Atlantic.     

The cardiac ventricles of a baleen whale (Balaenoptera acutorostrata: Minke whale) and a toothed whale (Hyperoodon ampullatus: Bottlenose whale)

Fifteen minke whale (Balaenoptera acutorostrata: Mysticeti) and three bottlenose whale (Hyperoodon ampullatus: Odontoceti) hearts were obtained from Norway. Only the ventricular mass and the base of the great arteries were available for study. The shape of the heart, the double apex, the narrowness of the interventricular septum in the dorsiventral plane, the side-to-side position of the ventricles, the relative thickness of the wall of the right ventricle, and the heavy trabeculation agree with other, brief reports of whale heart morphology. Coronary artery tortuosity, which has been described in sperm whales by others, was found in the bottlenose but not in the minke whales. It is suggested that the shape of the heart is associated with depth and duration of dives and that the pattern of trabeculation may be related to the size of the animal.     

Nuclear and mitochondrial markers reveal distinctiveness of a small population of bottlenose whales (Hyperoodon ampullatus) in the western North Atlantic

Small populations at the edge of a species' distribution can represent evolutionary relics left behind after range contractions due to climate change or human exploitation. The distinctiveness and genetic diversity of a small population of bottlenose whales in the Gully, a submarine canyon off Nova Scotia, was quantified by comparison to other North Atlantic populations using 10 microsatellites and mitrochondrial DNA (mtDNA) control region sequences (434 bp). Both markers confirmed the distinctiveness of the Gully (n = 34) from the next nearest population, off Labrador (n = 127; microsatellites -F(ST)= 0.0243, P < 0.0001; mtDNA -Phi(ST) = 0.0456, P < 0.05). Maximum likelihood microsatellite estimates suggest that less than two individuals per generation move between these areas, refuting the hypothesis of population links through seasonal migration. Both males and females appear to be philopatric, based on significant differentiation at both genomes and similar levels of structuring among the sexes for microsatellites. mtDNA diversity was very low in all populations (h = 0.51, pi = 0.14%), a pattern which may be due to selective sweeps associated with this species' extreme deep-diving ecology. Whaling had a substantial impact on bottlenose whale abundance, with over 65 000 animals killed before the hunt ceased in the early 1970s. Genetic diversity was similar among all populations, however, and no signal for bottlenecks was detected, suggesting that the Gully is not a relic of a historically wider distribution. Instead, this unique ecosystem appears to have long provided a stable year-round habitat for a distinct population of bottlenose whales.     

Molecular genetic identification of southern hemisphere beaked whales (Cetacea: Ziphiidae)

To assist in the species-level identification of stranded and hunted beaked whales, we compiled a database of 'reference' sequences from the mitochondrial DNA control region for 15 of the 20 described ziphiid species. Reference samples for eight species were obtained from stranded animals in New Zealand and South Australia. Sequences for a further seven species were obtained from a previously published report. This database was used to identify 20 'test' samples obtained from incompletely documented strandings around New Zealand. Analyses showed that four of these 'test' specimens (20%) had initially been misidentified. These included two animals of particular interest: (i) a Blainville's beaked whale ( Mesoplodon densirostris) , the first record of this species in New Zealand waters; and, (ii) a juvenile Andrews' beaked whale ( Mesoplodon bowdoini ), a species known from just over 20 strandings worldwide. A published sequence from a beaked whale product purchased in the Republic of Korea was identified as a Cuvier's beaked whale ( Ziphius cavirostris ). Levels of intra- and interspecific variation were compared to determine the potential for misidentification when the database or taxonomy is incomplete. Intraspecific variation was generally <2%, and interspecific divergence was generally >4.7%. Exceptions were within-species variation in Hyperoodon planifrons , southern bottlenosed whale (4.12%), which exceeded the variation between the two species of Berardius (3.78%), and variation between the two specimens assigned to M. hectori , Hector's beaked whale (7.14%). The latter case appears to be an error in species identification, and could represent the discovery of a new species of beaked whale.     

Structure and growth pattern of the bizarre hemispheric prominence on the rostrum of the fossil beaked whale Globicetus hiberus (Mammalia,Cetacea, Ziphiidae)

The rostrum of most ziphiids (beaked whales) displays bizarre swollen regions, accompanied with extreme hypermineralisation and an alteration of the collagenous mesh of the bone. The functional significance of this specialization remains obscure. With the voluminous and dense hemispheric excrescence protruding from the premaxillae, the recently described fossil ziphiid Globicetus hiberus is the most spectacular case. This study describes the histological structure and interprets the growth pattern of this unique feature. Histologically, the prominence in Globicetus is made up of an atypical fibro‐lamellar complex displaying an irregular laminar organization and extreme compactness (osteosclerosis). Its development is suggested to have resulted from a protraction of periosteal accretion over the premaxillae, long after the end of somatic growth. Complex shifts in the geometry of this tissue are likely to have occurred during its accretion and no indication of Haversian remodeling could be found. X‐ray diffraction and Raman spectroscopy indicate that the bone matrix in the premaxillary prominence of Globicetus closely resembles that of the rostrum of the extant beaked whale Mesoplodon densirostris: apatite crystals are of common size and strongly oriented, but the collagenous meshwork within bone matrix seems to be extremely sparse. These morphological and structural data are discussed in the light of functional interpretations proposed for the highly unusual and diverse ziphiid rostrum. J. Morphol. 277:1292–1308, 2016. © 2016 Wiley Periodicals, Inc.     

The most basal beaked whale Ninoziphius platyrostris Muizon, 1983: clues on the evolutionary history of the family Ziphiidae (Cetacea: Odontoceti)

Ninoziphius platyrostris, from the late Neogene of Peru, is one of the best‐known fossil beaked whales (Odontoceti: Ziphiidae), with a holotype including the skull with ear bones, mandibles, teeth, and postcranial elements. Furthermore, based on several characters, including a complete functional upper and lower dentition, it is usually considered as one of the most archaic ziphiids. However, the poorly preserved dorsal portion of the holotype skull has led to unresolved phylogenetic relationships. With the addition of two newly prepared skulls from the same Peruvian locality we redescribed N. platyrostris. In the light of recent ziphiid discoveries, an emended diagnosis of the species is proposed here. In our cladistic analysis Ninoziphius is the most basal stem ziphiid. Newly observed or reassessed morphological traits allow functional and ecological considerations. The morphology of the oral apparatus suggests that Ninoziphius was less specialized for suction feeding than most extant ziphiids. Tooth wear in the holotype may indicate benthic feeding. Although the vertebral column of Ninoziphius corresponds to less developed locomotor abilities for deep dives, its cranial morphology does not provide definitive arguments for an echolocation system less efficient than in deep diving extant ziphiids. Finally, the phylogenetic tree produced was used to detail the evolutionary history of several major ziphiid features (dental reduction, development of mandibular tusks, and increased body size). © 2013 The Linnean Society of London     

Review of the distribution of Mesoplodon species (order Cetacea, family Ziphiidae) in the North Atlantic

Four species of beaked whales of the genus Mesoplodon regularly occur in the North Atlantic. These are Sowerby's Beaked Whale Mesoplodon bidens, Blainville's Beaked Whale Mesoplodon densirostris, Gervais Beaked Whale Mesoplodon europaeus and True's Beaked Whale Mesoplodon mirus. These four species differ in their distribution within this area. M. bidens is the most northerly recorded species followed by M. mirus. M. densirostris and M. europaeus both generally occur further south and their distributions cross the equator. The distribution of Mesoplodon species may relate to variations in water temperature.     

The diversity and distribution of the cetaceans of Costa Rica (Cetacea: Delphinidae, Physeteridae, Ziphiidae y Balaenopteridae)

The first complete checklist of Costa Rican cetaceans is presented with a total of 28 species (35% of the group's world diversity). Most of the species occur in the Pacific Ocean (89%) and most are considered oceanic (57%), common (54%) and resident (68%). The known distribution and status of each species are also provided.     

Deep-diving foraging behaviour of sperm whales (Physeter macrocephalus)

1. Digital tags were used to describe diving and vocal behaviour of sperm whales during 198 complete and partial foraging dives made by 37 individual sperm whales in the Atlantic Ocean, the Gulf of Mexico and the Ligurian Sea. 2. The maximum depth of dive averaged by individual differed across the three regions and was 985 m (SD = 124.3), 644 m (123.4) and 827 m (60.3), respectively. An average dive cycle consisted of a 45 min (6.3) dive with a 9 min (3.0) surface interval, with no significant differences among regions. On average, whales spent greater than 72% of their time in foraging dive cycles. 3. Whales produced regular clicks for 81% (4.1) of a dive and 64% (14.6) of the descent phase. The occurrence of buzz vocalizations (also called 'creaks') as an indicator of the foraging phase of a dive showed no difference in mean prey capture attempts per dive between regions [18 buzzes/dive (7.6)]. Sperm whales descended a mean of 392 m (144) from the start of regular clicking to the first buzz, which supports the hypothesis that regular clicks function as a long-range biosonar. 4. There were no significant differences in the duration of the foraging phase [28 min (6.0)] or percentage of the dive duration in the foraging phase [62% (7.3)] between the three regions, with an overall average proportion of time spent actively encountering prey during dive cycles of 0.53 (0.05). Whales maintained their time in the foraging phase by decreasing transit time for deeper foraging dives. 5. Similarity in foraging behaviour in the three regions and high diving efficiencies suggest that the success of sperm whales as mesopelagic predators is due in part to long-range echolocation of deep prey patches, efficient locomotion and a large aerobic capacity during diving.     

Deep-diving behaviour of a whale shark Rhincodon typus during long-distance movement in the western Indian Ocean

A whale shark Rhincodon typus satellite tagged off the coast of Mozambique showed a highly directional movement across the Mozambique Channel and around the southern tip of Madagascar, a minimum distance of 1200 km in 87 days. Dives to depths well into the mesopelagic and bathypelagic zones (1286 m maximum depth) were recorded in a bathymetrically non-constraining habitat. The water temperature range recorded during the fish's movement was 3·4–29·9° C.     

Description of a new long‐snouted beaked whale from the Late Miocene of Denmark: evolution of suction feeding and sexual dimorphism in the Ziphiidae (Cetacea: Odontoceti)

A new genus and species of Ziphiidae, Dagonodum mojnum gen. nov., sp. nov., from the upper Miocene Gram Formation (c. 9.9–7.2 Ma) represents the first occurrence of the family in Denmark. This long‐snouted ziphiid is characterized by two pairs of mandibular tusks, the Eustachian outlet that approximately levels with the dorsalmost margin of the posterior portion of the involucrum, and the left trapezoid nasal with a posteromedial projection into the frontal. A phylogenetic analysis including 25 species and 69 characters was conducted. Dagonodum mojnum is placed in a basal ziphiid clade as the sister taxon of Messapicetus. The specimen is probably a male, because it has enlarged tusks. Alternatively, females could also be involved in fights and develop erupted tusks as in the extant Berardius. Although less well supported, this interpretation proposes that aggressive interactions were not restricted to males in stem‐ziphiids. With a thickened thyrohyal and the presence of a precoronoid crest, D. mojnum was able to use suction feeding, but was less specialized to it compared to extant ziphiids. The elongated neck of D. mojnum less optimized to perform deep dives, and the shallow depth at which the Gram Formation was deposited corroborates the hypothesis that at least part of the stem‐ziphiids were not regular deep divers.     

A new stem-sperm whale (Cetacea, Odontoceti, Physeteroidea) from the Latest Miocene of Peru

A finely preserved skull with mandible and teeth associated, from the Latest Miocene beds (ca. 6 Ma) of the Pisco Formation, Sud-Sacaco, Peru, represents a new physeteroid genus and species, Acrophyseter deinodon. This moderate size sperm whale is characterized, among others, by: the short rostrum, the mandible distinctly curved upwards, large teeth very close together (12 on each upper tooth row and 13 on each lower tooth row), the lateral margin of the maxilla along the rostrum base much lower than the orbit roof, a wide supracranial basin dorsally overhanging the right orbit and limited to the cranium and a large temporal fossa dorsomedially elevated. A preliminary cladistic analysis provides a phylogenetic position of Acrophyseter nested within the stem-Physeteroidea, more basal than the clade Kogiidae + Physeteridae. The morphology of the oral apparatus and of the temporal fossa suggests that Acrophyseter was able to feed on large preys.     

Killer sperm whale: a new basal physeteroid (Mammalia, Cetacea) from the Late Miocene of Italy

Zygophyseter varolai , a new genus and species of Physeteroidea (Cetacea, Odontoceti), is based on an almost complete skeleton from the Late Miocene (Tortonian) in southern Italy. The extreme elongation of the zygomatic process of the squamosal and the circular supracranial basin (probably for housing the spermaceti organ) delimited by a peculiar anterior projection of the supraorbital process of the right maxilla are the most distinctive features of this bizarre sperm whale. Large body size, large teeth present in both lower and upper jaw, and anteroposteriorly elongated temporal fossa and zygomatic process of the squamosal indicate that this cetacean (for which we suggest the English common name killer sperm whale) was an active predator adapted to feeding on large prey, similarly to the extant killer whale ( Orcinus orca ). A phylogenetic analysis reveals that Zygophyseter belongs to a Middle–Late Miocene clade of basal physeteroids, together with Naganocetus (new genus for the type of ' Scaldicetus ' shigensis ). Moreover, the phylogenetic analysis shows evidence of a wide physeteroid radiation during the Miocene and that the extant Physeter and Kogia belong to two distinct families that form a clade representing the crown-group Physeteroidea.  © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 148 , 103–131.     

New baleen whale genera (Cetacea, Mammalia) from the miocene of the northern caucasus and ciscaucasia: 1. Kurdalagonus gen. nov. from the middle-late Sarmatian of Adygea

A revision of previously known material and analysis of new records of Miocene baleen whales from the Sarmatian of Adygea (city of Maikop, Blinovo Formation) resulted in the establishment of a new genus, Kurdalagonus with three species: K. mchedlidzei sp. nov. (Middle Sarmatian, Nagiezh-Uashkh locality), K. adygeicus sp. nov. (Upper Sarmatian, Hydroelectric power station locality), and K. maicopicus (Spasskii, 1951) (=Cetotherium maicopicum Spasskii, 1951; Middle Sarmatian, Hydroelectric power station locality).     

Histology and growth pattern of the pachy-osteosclerotic premaxillae of the fossil beaked whale Aporotus recurvirostris (Mammalia, Cetacea, Odontoceti)

Beaked whales (Ziphiidae) often show highly specialized features, involving bone morphology or structure, in the rostral region of their skulls. Previous studies revealed an extremely derived and peculiar histological structure in the rostrum of the extant Mesoplodon densirostris. In order to assess if this structure is a general feature of ziphiids, the swollen premaxillae of Aporotus recurvirostris, a Miocene species from the North Sea, were studied histologically. These bones are pachyostotic and strongly osteosclerotic. However, their structural organization is entirely different from that of M. densirostris rostrum: they are basically made of a non-remodeled, laminar tissue that was cyclically deposited by the periosteum. As compared to the generalized structure of the premaxillae of toothed whales exemplified by the bottlenose dolphin, Tursiops truncatus, the pachyostotic condition of Aporotus premaxillae was obviously due to a particularly high and sustained growth-rate, occurring in a dorso-lateral direction. The osteosclerotic structure of these bones resulted from a complete lack of inner resorption activity. The histological features of Aporotus premaxillae indicate that these bones are not likely to have been hypermineralized, and thus, their physical properties must have differed from those of the M. densirostris rostrum. The possible functional involvements of rostral peculiarities in beaked whales are discussed with reference to the whole set of available comparative data.     

New baleen whale genera (Cetacea, Mammalia) from the miocene of the northern Caucasus and Ciscaucasia: 2. Vampalus gen. nov. from the Middle-Late Miocene of Chechnya and Krasnodar Region

Based on an almost complete skeleton (skull, scapula fragment, humeri, ulna, radius, 7 cervical, 12 thoracic, and 20 lumbar and caudal vertebrae) from the Aksai River valley near the village of Sayasan (Nozhai-Yurtovskii District of the Chechen Republic), a new Middle-Late Miocene representative of the cetotheriid subfamily Herpetocetinae, Vampalus sayasanicus gen. et sp. nov., is described. This is the first record of fossil whales in Chechnya. The genus Vampalus is also considered to include Cetotherium helmerseni Brandt, 1871 from the Miocene of the Krasnodar Region.     

A genetic analysis of the beluga whale Delphinapterus leucas (Cetacea: Monodontidae) from summer aggregations in the Russian Far East

The genetic structure of four summer aggregations of the Beluga Whale, Delphinapterus leucas, in Sakhalin Bay and Udskaya Bay, off the western coast of Kamchatka in the Sea of Okhotsk and in the Anadyr Estuary of the Bering Sea was analyzed through nucleotide sequencing of the mtDNA control region and detection of the allelic composition of nine microsatellite loci in nuclear DNA. It has been shown that each of the aggregations features a unique set of maternal lines, which indicates a high degree of philopatry in this species. Beluga whales of the Anadyr Estuary are genetically isolated from those of the Sea of Okhotsk. Beluga whales of the summer aggregations of Sakhalin Bay and those from Udskaya Bay share a common gene pool and belong to a single population, while the whales that summer off western Kamchatka with great consistency may be attributed to a different population. Comparison of nucleotide sequences of the mtDNA in beluga whales from various waters of the Russian Far East and North America allowed us to propose a hypothesis about how the structure of beluga whale populations formed in the North Pacific during the postglacial period.