A review of the biology and ecology of the whale shark

The information available on the biology and ecology of the whale shark is reviewed, and is updated from material published since 1986. Research work carried out on the seasonal aggregation of whale sharks at the Ningaloo Reef in Western Australia is summarized. Future research studies on whale sharks in the Ningaloo Marine Park are discussed in the context of management of sustainable whale shark interaction tourism.     

Nucleotide sequence of the D-loop region of the sperm whale (Physeter macrocephalus) mitochondrial genome

We have amplified, by the polymerase chain reaction, and have sequenced the D-loop region of the mitochondrial DNA from the sperm whale (Physeter macrocephalus). The sperm whale D-loop was aligned with D- loop sequences from four other cetaceans (Commerson's dolphin, orca, fin whale, and minke whale) and an out-group (cow). This alignment showed the sperm whale sequence to be larger than that of other cetaceans. In addition, some sequence blocks were highly conserved among all six species, suggesting roles in the functioning of mitochondrial DNA. Other blocks that were previously reported to be well conserved among cetaceans showed little sequence conservation with the sperm whale D-loop, which argues against the functional importance of these sequence blocks in cetaceans.      

Molecular studies on two variant repeat types of the common cetacean DNA satellite of the sperm whale, and the relationship between Physeteridae (sperm whales) and Ziphiidae (beaked whales)

In the sperm whale (Physeter macrocephalus) two different repeat types (A and B) of the common cetacean DNA satellite were identified. The evolution of each group of repeats appears to be independent from that of the other. The sequence similarity between the two groups is less than the similarity between group A and repeats of the satellite in related whale species. The systematic relationship within and between the families Physeteridae (sperm whales) and Ziphiidae (beaked whales) was addressed by both sequence analysis of the satellite and comparisons with the families Delphinidae and Phocoenidae. The mysticete blue whale (Balaenoptera musculus) was used as an outgroup in the comparisons. The molecular phylogeny, when maximum-parsimony analysis and the neighbor-joining method were used, grouped together species of each family. At the family level the ziphiids grouped closet to the families Phocoenidae and Delphinidae. The similarities between the common cetacean satellite of the blue whale and the sperm whale were greater than those between the blue whale and the other odontocetes included, suggesting that the evolution of the satellite is slower in the sperm whale than in the other odontocetes.      

The complete nucleotide sequence of the mitochondrial DNA of the fin whale,Balaenoptera physalus

Summary The composition of the mitochondrial DNA (mtDNA) of the fin whale,Balaenoptera physalus, was determined. The length of the molecule is 16,398 bp, and its organization conforms with that of other mammals. The general similarity between the mtDNA of the fin whale and the cow is greater than the similarity between the fin whale and other species (human, mouse, rat) in which the composition of the entire molecule has been described. The D-loop region of the mtDNA of the fin whale is 81% identical to the D-loop of dolphin DNA, and the central portion of the D-loop is similar to the bovine D-loop. The accumulation of transversions and gaps in the 12S and 16S rRNA genes was assessed by comparing the fin whale, cow, and human. The sequence difference between human and the whale and human and the cow was at the same level, indicating that the rate of evolution of the mtDNA rRNA genes is about the same in artiodactyls and cetaceans. In the 12S rRNA gene an accumulation rate of 0.05% per million years places the separation of cetaceans and artiodactyls at about 55 million years ago. The corresponding figure for human and either the whale or the cow is about 80 million years. In the 16S rRNA gene a 0.08% accumulation rate of transversions and gaps per million years yields concurring figures. A comparison between the cytochromeb gene of the fin whale and cytochromeb sequences in the literature, including dolphin (Stenella) sequences, identified the cetaceans as monophyletic and the artiodactyls as their closest relatives. The comparison between the cytochromeb sequences of the fin whale andStenella showed that differences in codon positions one or two were frequently associated with a change in another codon position.     

中国大陆海域沿岸搁浅和误捕的喙鲸类调查

从2009 年1 月至2010 年2 月,我们对中国大陆海域沿岸搁浅和误捕的喙鲸类头骨标本进行了测量和鉴
定。目前中国大陆海域搁浅和误捕的喙鲸类有5 种,分别为柯氏喙鲸、贝氏喙鲸、朗氏喙鲸、柏氏中喙鲸和小
中喙鲸,其中小中喙鲸为中国海域(包括台湾)的首次报道,也是在西北太平洋区的首次记录。小中喙鲸的主
要形态鉴别特征为有1 对纺锤形牙齿着生在下颌骨联合后面。经对已报道过的大陆海域搁浅和误捕的3 个雌性
银杏齿中喙鲸头骨标本和台湾省搁浅银杏齿中喙鲸的颅骨、鼻骨、下颌骨以及牙齿特征对比重新鉴定,订正大
陆的3 个样本为雌性柏氏中喙鲸。本文报道了大陆沿岸海域搁浅和误捕的喙鲸类最新调查研究结果。     

Re-identification of the supposed True's beaked whale Mesoplodon mirus from Scotland

In the first week of January 1931 a beaked whale (Family Ziphiidae) stranded at Gierinish, South Uist, Outer Hebrides, was identified as a True's beaked whale Mesoplodon mirus . This stranding is referred to frequently in the cetacean literature, either directly or indirectly. Re-examination of the skull of this specimen reveals characters unique to Cuvier's whale Ziphius cavirostris and not shown by any Mesoplodon . Therefore, there is no known stranding of True's beaked whale in Britain.     

Hydrodynamic performance of the flippers of large‐bodied cetaceans in relation to locomotor ecology

Cetaceans evolved flippers that are unique in both size and shape probably due to selection pressures associated with foraging and body size. Flippers function as control surfaces for maneuverability and stability. Flippers of cetaceans and engineered hydrofoils are similar with streamlined cross‐sections and wing‐like planforms, which affect lift, drag and hydrodynamic efficiency. Scale models of the flippers from large‐bodied (body length > 6 m) cetaceans (fin whale, killer whale, sperm whale) were constructed from computed tomography (CT) scans of flippers. Flipper planforms were highly tapered for the fin whale, a rounded, paddle‐like design for the killer whale, and a square geometry for the sperm whale. Hydrodynamic properties of the models at varying angles of attack (?40º to 40^o) were determined in a water tunnel with a multi‐axis load cell. The flippers were found to have hydrodynamic characteristics similar to engineered wings. Differences in flipper morphology of large‐bodied cetaceans and their hydrodynamic performance are associated with the requirements of aquatic locomotion involved with ecology of the whales. The flippers of the killer whale provided the greatest maneuverability, whereas the flippers of the fin whale had low drag for lunging and the flippers of the sperm whale provided lift for diving.     

A Swedish subfossil find of a bowhead whale from the late Pleistocene: shore displacement,paleoecology in south-west Sweden and the identity of the Swedenborg whale (Balaena swedenborgii Liljeborg, 1867)

The Swedenborg whale Balaena swedenborgii Liljeborg, 1867, is a baleen whale species believed to have existed in the North Sea from the period when the inland ice melted around 13,000 before present (BP) until about 8000 years ago. The first bones attributed to this species were found in Sweden in 1705. When whale remains were discovered on the Swedish west coast during the extension work of a motorway extension, it was speculated that this could be a specimen of the extinct Swedenborg whale. The bones were found 72 m above the present-day sea level embedded in glacial mud. Shelly remains of marine organisms were present in the deposit surrounding the whale-fall, and sediments with the associated specimens were therefore collected for further analyses. We applied radiocarbon dating, thin sectioning, morphological analyses, ancient DNA typing and analyses of the associated shelly assemblage in an interdisciplinary effort to understand the circumstances of this fossil whale-fall. Our results show that the whale is not the putative species B. swedenborgii, but a bowhead whale Balaena mysticetus. The results also indicate that the whale must have been rapidly covered by glacial sediments, highlighting the speed of the deglacial process in the area.     

Mysticete (baleen whale) relationships based upon the sequence of the common cetacean DNA satellite.

The genomes of all extant cetaceans are characterized by the presence of the so-called common cetacean DNA satellite. In the mysticetes (whalebone whales) the repeat length of the satellite is 1,760 bp. In the odontocetes (toothed whales), other than the family Delphinidae, the repeat length is usually approximately 1,740 bp. The Delphinidae are characterized by a repeat length of approximately 1,580 bp. It has been shown in odontocetes that the satellite evolves in concert and that differences between species, with respect to the sequence of the satellite, correspond reasonably well to their evolutionary distances. In the present study the sequence of the satellite was determined in three repeats in each of seven mysticete species, and a consensus for each species established. Parsimony and neighbor-joining analyses based upon sequences of all repeats showed that the primary evolutionary distinction among the mysticetes is between the Balaenidae sensu stricto (i.e., the bowhead whale and the right whale) and all remaining species, including the pygmy right whale, a species that usually has been included in the Balaenidae. The comparisons also showed that the humpback whale and the gray whale were approximately equidistant from the blue whale and the fin whale (genus Balaenoptera). Concerted evolution of the satellite was also demonstrated among the mysticetes, but it appeared to evolve more slowly in the mysticetes than in the odontocetes.     

IDENTIFICATION OF WHALE SPECIES BY LIQUID CHROMATOGRAPHIC ANALYSIS OF SARCOPLASMIC PROTEINS

Liquid chromatography (LC) was applied to identify whale species by analyzing water-soluble sarcoplasmic proteins in skeletal muscles. Twenty-five samples from four baleen whale species (fin whale, sei whale, Bryde's whale, and minke whale) and eight toothed whale species (sperm whale, Baird's beaked whale, short-finned pilot whale, Dall's porpoise, northern right whale dolphin, Pacific white-sided dolphin, common dolphin, and striped dolphin) were analyzed. Water-soluble sarcoplasmic proteins were extracted from each sample and analyzed using a UV-VIS spectrophotometric detector at 280 nm and a pho-todiode array detector. The chromatographic profiles of each sample showed distinctive qualitative and quantitative characteristics for each whale species, making species identification possible. A photodiode array detector was useful for further accurate identification of whale species by obtaining the absorption spectra of separated protein peaks. These results suggest that the LC method is readily applicable to rapid, simple, and reliable identification of whale species.     

Ensemble modeling of the potential distribution of the whale shark in the Atlantic Ocean

The whale shark (Rhincodon typus) is an endangered marine fish species which can be adversely affected by the fishing activities of the industrial purse seine fleet targeting tropical tuna. Tuna tend to aggregate around all types of floating objects, including whale sharks. We analyzed and modeled the spatial distribution and environmental preferences of whale sharks based on the presence and absence data from fishing observations in the Atlantic Ocean. We used a thorough multialgorithm analysis, based on a new presence–absence dataset, and endeavored to follow the most recent recommendations on best practices in species distribution modeling. First, we selected a subset of relevant variables using a generalized linear model that addressed multicollinearity, statistical errors, and information criteria. We then used the selected variables to build a model ensemble including 19 different algorithms. After eliminating models with insufficient performance, we assessed the potential distribution of whale sharks using the mean of the predictions of the selected models. We also assessed the variance among the predictions of different algorithms, in order to identify areas with the highest model consensus. The results show that several coastal regions and warm shallow currents, such as the Gulf Stream and the Canary and Benguela currents, are the most suitable areas for whale sharks under current environmental conditions. Future environmental projections for the Atlantic Ocean suggest that some of the suitable regions will shift northward, but current concentration areas will continue to be suitable for whale shark, although with less productivity, which could have negative consequences for conservation of the species. We discuss the implications of these predictions for the conservation and management of this charismatic marine species.     

Feeding habits of the whale shark (<Emphasis Type="Italic">Rhincodon typus</Emphasis>) inferred by fatty acid profiles in the northern Mexican Caribbean

Whale shark (Rhincodon typus, Smith, 1828) is an endangered species with anthropogenic pressures due to increasing demand of encounter tourism activities. Research efforts to identify management and conservation strategies for this species are needed. The Northern Mexican Caribbean is one of the most important feeding aggregation sites of whale sharks worldwide. In this study, Mexican Caribbean whale shark feeding habits are assessed by means of fatty acid (FA) signature analysis, a biochemical non-destructive technique widely applied in trophic ecology studies. Sub-dermal tissue biopsies of 68 whale sharks and samples of their potential prey (zooplankton) were collected during 2010 and 2011 in two areas with high R. typus abundance. Zooplankton samples (n?=?17) were divided in two categories: mixed zooplankton (several groups of zooplankton) and fish eggs (> 95% of sample components were fish eggs). FA profiles of whale shark tissue sampled between years showed significant variability; while there was no intraspecific differences in FA signature related to sex, size and location. FA profiles of whale sharks and their potential prey were dominated by saturated fatty acids (SFA). R. typus FA signature was significantly different from that of mixed zooplankton; on the other hand, whale shark and fish egg FA profiles formed groups with overlapping values and registered high levels of oleic acid. PUFA average ω3/ ω6 ratio on whale shark FA profiles for both years was below 1. Arachidonic acid (ARA) percentage was higher in whale shark biopsies (13.2% in 2010, 6.8% in 2011) compared to values observed in fish eggs (2.0%) and mixed zooplankton (1.4%). Similarity between FA profiles of whale sharks and fish eggs, low levels of bacterial FA found in R. typus biopsies, as well as whale shark feeding behavior observations in the study area, suggest that R. typus is feeding mainly on surface zooplankton in Mexican Caribbean; however, elevated ARA percentages in whale shark samples may indicate that this species has complementary feeding sources, such as demersal zooplankton, which has been reported in other aggregation sites. Results obtained contribute to the knowledge of the whale shark trophic ecology in the area, but are inconclusive. Further studies are recommended to evaluate whale shark FA profiles from different tissues (muscle or blood); also, broader information is needed about zooplankton FA signature in the study area.     

The complete mitochondrial genome sequence of the world's largest fish,the whale shark (Rhincodon typus), and its comparison with those of related shark species

The whale shark (Rhincodon typus) is the largest extant species of fish, belonging to the order Orectolobiformes. It is listed as a “vulnerable” species on the International Union for Conservation of Nature (IUCN)'s Red List of Threatened Species, which makes it an important species for conservation efforts. We report here the first complete sequence of the mitochondrial genome (mitogenome) of the whale shark obtained by next-generation sequencing methods. The assembled mitogenome is a 16,875 bp circle, comprising of 13 protein-coding genes, two rRNA genes, 22 tRNA genes and a control region. We also performed comparative analysis of the whale shark mitogenome to the available mitogenome sequences of 17 other shark species, four from the order Orectolobiformes, five from Lamniformes and eight from Carcharhiniformes. The nucleotide composition, number and arrangement of the genes in whale shark mitogenome are the same as found in the mitogenomes of the other members of the order Orectolobiformes and its closest orders Lamniformes and Carcharhiniformes, although the whale shark mitogenome had a slightly longer control region. The availability of mitogenome sequence of whale shark will aid studies of molecular systematics, biogeography, genetic differentiation, and conservation genetics in this species.     

Quantification and genetic profiling of DNA isolated from free-floating feces of the North Atlantic right whale (Eubalaena glacialis)

Fecal analysis from the highly endangered North Atlantic right whale provides valuable information about health and reproductive parameters of individual animals. Genetically profiling the feces facilitates this connection when the sample originator is unknown. Although genetic analysis of feces collected in terrestrial systems has become well established, genetic studies of cetacean DNA are rare. Here, the use of free‐floating feces as a source of right whale DNA and the reliability of the genotypes produced are examined. On average, fecal extracts yielded 25 ng of DNA/mg dry weight, but less than 1% was right whale DNA. Although all samples were amplified using genus‐specific mitochondrial control region primers, the quantity of right whale DNA present was over estimated when compared to amplifications using nuclear primers. No correlation was found between the quantity of right whale DNA recovered and the duration the sample sat in the water. Composite microsatellite profiles from multiple amplifications of 28 fecal samples of known origin were consistent with profiles of the same individuals obtained from skin biopsies, however, the rate of allelic dropout varied depending on the amount of right whale DNA added. A screening and genotyping protocol for reliable genetic profiling based on fecal DNA quantification is presented.     

Arterial system of the head and anterior portion of the trunk of Balaenoptera edeni

As demonstrates the investigation of the blood system in the whale (Balaenoptera edeni) performed by means of the macropreparation of corrosive casts and sawcuts, in this species, as in other Cetacea, there is a well developed complex of the arterial rete mirabile, owing to which the brain is supplied with blood. In the whale mentioned this complex is comparable with that in dolphins and is noticeably less developed than in the spermacet (Physeter sp.). Angioarchitectonic of the whale has much in common with the arterial system of representatives of Balaenopteridae family, previously studied.     

Insights into the population structure of blue whales in the Eastern North Pacific from recent sightings and photographic identification

Blue whales were widely distributed in the North Pacific prior to the primary period of modern commercial whaling in the early 1900s. Despite concentrations of blue whale catches off British Columbia and in the Gulf of Alaska, there had been few documented sightings in these areas since whaling for blue whales ended in 1965. In contrast, large concentrations of blue whales have been documented off California and Baja California and in the eastern tropical Pacific since the 1970s, but it was not known if these animals were part of the same population that previously ranged into Alaskan waters. We document 15 blue whale sightings off British Columbia and in the Gulf of Alaska made since 1997, and use identification photographs to show that whales in these areas are currently part of the California feeding population. We speculate that this may represent a return to a migration pattern that has existed for earlier periods for eastern North Pacific blue whale population. One possible explanation for a shift in blue whale use is changes in prey driven by changes in oceanographic conditions, including the Pacific Decadal Oscillation (PDO), which coincides with some of the observed shifts in blue whale occurrence.     

Analysis of the C4 genes in baleen whales using a human cDNA probe

We have used a human C4 cDNA probe to investigate the complement component C4 gene in four members of the family Balaenopteridae: fin whale (Balaenoptera physalus), sei whale (B. borealis), minke whale (B. acutorostrata), and bryde's whale (B. edeni). Restriction mapping of genomic DNA from the first three species suggests the presence of only one locus in these species, and also shows that the C4 genes in the three species are very similar. We have used 14 restriction endonucleases to investigate the restriction fragment length polymorphism (RFLP) of fin whales, 13 enzymes for sei whales, and 8 enzymes for the minke whale. No polymorphism was seen in DNA from the five minke whale samples, but Rsa I and Taq I restriction enzymes gave polymorphism in fin and sei whales whereas Hind III and Msp I restriction enzymes showed polymorphism in sei whales only. Only one bryde's whale sample was available for investigation. The study of DNA available from mother-fetus pairs from the two polymorphic species demonstrated a simple, two-allele transmission of RFLP alleles.     

Estimated absorbance spectra of the visual pigments of the North Atlantic right whale (Eubalaena glacialis)

To assess the spectral sensitivities of the retinal visual pigments from the North Atlantic right whale (Eubalaena glacialis), we have cloned and sequenced two exons from the rod opsin gene and two exons from the middle‐wavelength sensitive (MWS) cone opsin gene in order to determine the amino acids at positions known to be key regulators of the spectral location of the absorbance maximum (λ_max). Based on previous mutagenesis models we estimate that the right whale possesses a rod visual pigment with a λ_max of 499 nm and a MWS cone visual pigment with a λ_max of 524 nm. Although the MWS cone visual pigment from the right whale is blue‐shifted in its spectral sensitivity like those from odontocetes, the spectral sensitivity of the right whale rod visual pigment is similar to those from terrestrial mammals.