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1.
  总被引:1,自引:0,他引:1  
Comparisons of the Irrawaddy dolphin, Orcaella brevirostris , between Australian and Asian sites documented geographic differences in height of dorsal fin, presence or absence of a median dorsal groove in front of the dorsal fin, and coloration (presence or absence of a dorsal cape). Analysis of genetic data provided support for two clades within the Asian samples, the Mekong River samples from Cambodia and southern Laos, and all other marine and freshwater sites from Thailand, Indonesia, and the Philippines. The major separation, however, was between sites in Asia and those from Australia (5.9% of base pair differences, compared with 1.2% for within Australia and 1.5% for within Asia). Within a 403 base segment of the mtDNA control region, Australian specimens had 17 diagnostic sites with 16 fixed base pair differences and one insertion/deletion. Consistent, statistically significant differences in skull characters of Australian specimens have previously been demonstrated and are reviewed in this paper. There was a high concordance in character differences demonstrated between O. brevirostris from all Asian sites and Australian specimens, especially in the genetic and osteological characters. Based on the range and concordance of character differences, we propose that the Australian dolphins be recognized as a new species, Orcaella heinsohni (suggested common name: Australian snubfin dolphin).  相似文献   

2.
    
Research into dolphin swimming historically was guided by false assumptions pertaining to maximum speed. Accurate measurements on swimming speed and duration of effort of free-ranging dolphins are rare. To examine the variance of maximum swimming speeds, nearly 2,000 speed measurements were obtained for both captive and free-ranging dolphins, including Tursiops truncatus, Pseudorca crassidens, Delphinus capensis , and Delphinus delpbis . Measurements were made from videotapes of dolphins trained to swim fast around a large pool or jumping to a maximum height, videotapes of captured wild dolphins immediately after release, and sequential aerial photographs of a school of free-ranging dolphins startled by a passing airplane. Maximum horizontal speeds for trained animals were 8.2 m/sec for T. truncatus , 8.0 m/sec for D. delphis , and 8.0 m/sec for P. crassidens . Maximum speeds for T. truncatus swimming upwards, prior to vertical leaps ranged from 8.2 to 11.2 m/sec. Wild T. truncatus demonstrated a maximum speed of 5.7 m/sec. Maximum swimming speed of free-ranging D. capensis responding to multiple passes by a low flying airplane was 6.7 m/sec. There was no evidence that the freeranging dolphins have superior swimming capabilities to captive animals. The results of this study imply that realistic maximum swimming speeds for dolphins are lower than previous reports which were based on sparse data and imprecise measurement techniques.  相似文献   

3.
    
Stable isotopic analyses of carbon, nitrogen, and sulfur were performed on teeth of different ages and sexes of the longbeaked common dolphin, Delphinus capensis, from the Gulf of California. Similarities in diet are suggested between the sexes, with no significant differences in isotopic compositions being observed. Differences in the δ13C, δ15N, and δ34S signatures were found among the age groups (nursing calf, juvenile, subadult, and adult). These data suggest that this species is generally a coastal feeder, and that it changes its feeding habits with increasing age, drawing more nutrition from higher trophic level organisms later in life.  相似文献   

4.
Seven tetranucleotide and three dinucleotide microsatellite loci were isolated from the short‐beaked common dolphin (Delphinus delphis). Number of alleles and observed heterozygosity ranged from three to twelve (mean 8.4) and from 0.087 to 0.978 (mean 0.741), respectively. All loci were tested in four other odontocete species and showed polymorphisms in most locus–species combinations. This panel of nuclear markers will be useful for the investigation of population ecology and social interactions in common dolphins and other cetacean species.  相似文献   

5.
Abstract: At least four morphologically distinct forms of common dolphins are found in the eastern Pacific, We compared length data for common dolphins photographed from the northern, central and southern regions as defined by Perrin et al. (1985) and found significant differences in average length for adult animals (>150 cm) and for "adult females" defined for our purposes as animals accompanied by calves. Analyses of calculated birth dates for calves demonstrated differences in timing of reproduction between the geographically adjacent forms. Length distributions from aerial photographs and samples collected from the purse seine fishery were strikingly similar. This work demonstrates a new, non-invasive method for obtaining unbiased life history and morphological data.  相似文献   

6.
The spotted dolphin (Stenella attenuata), a species commonly associated with the tuna fishery, is widely distributed in the eastern tropical Pacific Ocean (ETP). Geographic patterns in morphological characteristics of this dolphin were evaluated for 36 skull measurements of 574 museum specimens allocated to 5° latitude-longitude blocks. A strong subdivision between northern and southern offshore populations was demonstrated using principal components, canonical variates and cluster (UPGMA and function-point) analyses of block means derived from standardized, sex-adjusted measurements. Classification functions derived from a stepwise multiple discriminant analysis correctly identified more than 87 percent of the specimens as being from either a northern or southern locality. These results support recognition of southern spotted dolphins as a separate management stock. Dolphins from a sample representing a far-western locality show similarities with those from the south. Patterns of geographic variation in morphology were evaluated using Mantel tests and matrix correlations; 17 of the 36 characters showed regional patterning and 18 exhibited local patterning. Morphological trends were also assessed with respect to 14 oceanographic measures that characterize environmental variability in the ETP. In general, clinal variation in morphology mirrors a north-south trend found in several environmental variables. Overall, the most striking associations between morphological and environmental variables involved Solar Insolation (Jan.). Sea surface temperatures also exhibited a strong association with morphological variables; the highest correspondence was found between width of the temporal fossa and sea surface temperature in July. In addition, the thickness of the oxygen minimum layer exhibited a pattern of variation that was statistically associated with 58 percent of the skull characters. The geographic patterns found for cranial morphology and environmental measures are strongly clinal and in general congruent, suggesting that oceanographic conditions in part determine trends in morphological characteristics of spotted dolphins.  相似文献   

7.
The common dolphin has a widespread distribution and is relatively abundant in the temperate to subtropical waters of the eastern North Atlantic. However, it is not known whether different species, subspecies, or populations occur in this region. We examined 393 common dolphin skulls obtained from both stranded and bycaught individuals collected between 1901 and 2005. The series included skulls of 152 females and 199 males, from animals ranging in body length from 93 to 230 cm and 105 to 244 cm, respectively. The ranges of total body length, skull size, RL/ZGW ratio and maximum upper alveolar (tooth) count of common dolphins in the eastern North Atlantic overlapped with those of both short- ( D. delphis ) and long-beaked ( D. capensis ) species found off the Californian coast. However, in the absence of additional data, the common dolphin in the eastern North Atlantic is regarded here as a large form of Delphinus delphis . Sexual dimorphism and possible sex-linked characters were identified within the sample. Results of the current study indicate some population differentiation within the eastern North Atlantic, with common dolphins off Portugal showing segregation in morphometric characteristics from common dolphins in other areas.  相似文献   

8.
Growth, allometric relationships and sexual dimorphism are described from measurements of 105 male, 149 female and 38 unsexed specimens of short‐beaked common dolphin, Delphinus delphis, stranded along the Irish coastline (53.8% of the sample) or by‐caught in fisheries (46.2% of the sample), from 1990 to 2003. For each dolphin, 24 external body length measurements were recorded. Ages were determined for 183 dolphins by analysis of growth layer groups in the dentine. Males ranged in total body length (TBL) from 105 to 231 cm and females from 93 to 230 cm, with a maximum age of 25 years obtained for both sexes. Using a single Gompertz growth curve, asymptotic values obtained for TBL were 211.6 cm and 197.4 cm for males and females, respectively. Asymptotic lengths were attained at 11 years in males and 9 years in females. The gestation period was estimated to last approximately 11.5 months. Sexual size dimorphism (SSD) was evident, with males being significantly larger than females for 20 of the characters measured, and an SSD ratio of 1.06 was obtained. Sexual shape dimorphism was lacking, except for the presence of prominent postanal humps in mature males.  相似文献   

9.
    
A dwarf form of the spinner dolphin has been reported from the Gulf of Thailand, while more typical large spinner dolphins have been described from Japanese waters and other localities in the western Pacific. These reports have been based on very few specimens. Our purpose in this study was to determine the affinities of spinner dolphins throughout the region based on larger samples and to review their taxonomic status, with an hypothesis of two widespread ecotypic forms, or subspecies. We examined 213 osteological specimens, from a tuna gillnet fishery in the Philippines, from the former Taiwanese shark gillnet fishery in the Timor and Arafura Seas off northern Australia, from the Gulf of Thailand, from other areas in the western Pacific and Southeast Asia, from the eastern Indian Ocean, and from the Central and South Pacific. Results show that spinner dolphins from the deep inner waters of the Philippines conform to the large pelagic type of spinner dolphin that inhabits the Central and South Pacific, the western Pacific and the eastern Indian Ocean. The skull is similar in size and shape to the holotype specimen of S. longirostris (from unknown locality). This form feeds primarily on small mesopelagic fishes and squids. Spinner dolphins from the shallow waters of inner Southeast Asia represented in the sample, including the Gulf of Thailand, Timor Sea and Arafura Sea, are smaller in body and skull size, have fewer teeth and vertebrae, and feed mainly on benthic and coral reef fishes and invertebrates. We hypothesize that this form also inhabits the Java Sea and other shallow waters throughout inner Indonesia and Malaysia. We redescribe a subspecies corresponding to the small form and based on Delphinus roseiventris Wagner 1846 from the Arafura Sea, designating a neotype and paraneotype specimens.  相似文献   

10.
This revision deals with the Zygothrica samoaensis species group, which includes 15 species, five of which are described as new to science. Two synonymies are proposed: Z. vietnamensis Grimaldi, 1990, as a junior synonym of Z. flavofinira Takada, 1976, and Z. britannia Grimaldi, 1990, as a junior synonym of Z. malaysiana Grimaldi, 1990. The samoaensis group is divided into three species subgroups: (i) the samoaensis subgroup, consisting of nine species, including a new species, Z. australiaensis sp. nov.; (ii) the fijiana subgroup of Z. fijiana Takada, 1976, and two new species, Z. triscutellaris sp. nov. and Z. bicornigera sp. nov.; and (iii) the leptorostra subgroup of Z. leptorostra Grimaldi, 1990, and two new species, Z. pimacula sp. nov. and Z. quintamaculata sp. nov. Supplementary information on geographic distribution is provided for some species, as well as a key to all species of the samoaensis group. Zygothrica kokodana Grimaldi, 1990, and Z. paleovitta Grimaldi, 1990, have closer affinity with the hirticornis and the quadrivittata species groups, respectively, and so are moved to the corresponding genus Hirtodrosophila.  相似文献   

11.
    
The corpora albicantia (CAs) from the ovaries of 39 common dolphins ( Delphinus delphis ) caught in driving fisheries were used, and histologically and immunohistochemically examined. The area of each corpus albicans (CA) and the proportion of that area occupied by elastin were measured using NIH-image software. In all CAs, elastoid material (EM) was apparent although EM area varied in each CA. CAs increased in number with dolphin age. Smaller CAs contained a higher proportion of EM. EM was completely digested by elastase, but not by collagenase. Furthermore, EM was immunostained with anti-α-elastin antibody. These results demonstrated that EM was elastin. The present study is the first to describe the presence of elastin in cetacean CAs. The higher proportion of elastin in small-sized CAs of common dolphins is suggested as the likely cause of the persistence of CA.  相似文献   

12.
    
Here we present the first data describing the behavior of common dolphins ( Delphinus sp.) in the Hauraki Gulf, New Zealand. Activity budgets are used to assess the effects of diel, season, depth, sea surface temperature, group size, and composition on dolphin behavior. Additionally, the presence/absence of Bryde's whale ( Balaenoptera brydei ) and Australasian gannet ( Morus serrator ) is examined in relation to dolphin behavior. Behavioral data were collected from 686 independent dolphin groups during boat-based surveys conducted between February 2002 and January 2005. Foraging (46.7%) and social (7.2%) were the most and least frequently observed behaviors, respectively. Travel (28.9%), mill (9.5%), and rest (7.7%) accounted for the remainder of the activity budget. Behavior varied seasonally, with the highest proportion of foraging and resting groups observed during the spring and autumn, respectively. Behavior also varied with water depth, with foraging animals observed in the deepest and resting groups recorded in the shallowest regions of the Hauraki Gulf. A correlation between group size and behavior was evident, although behavior did not vary with the composition of dolphin groups. Resting, milling, and socializing animals were more frequently observed in smaller group sizes. Foraging behavior was prevalent in both small and large group sizes, suggesting foraging plasticity exists within this population. Behavior differed between single- and multispecies groups, with foraging more frequent in multispecies groups. Resting, milling, or socializing was rarely observed in the presence of any associated species, indicating the primary mechanism for association is likely prey related.  相似文献   

13.
Corals from 26 sites in the Indian Ocean, from numerous taxonomic sources, are analysed for distribution patterns after applying a consistent synonymy. The data set contains double the amount of distribution information used previously. Cluster analysis shows several contiguous regional groupings within this ocean, and no geographically dispersed groupings exist. Between-site species similarity correlates negatively with distance between sites. Coral species diversity and genus diversity plotted with latitude and longitude confirm that a band of high diversity stretches across the entire Indian Ocean, but that in this Ocean, unlike the Pacific and greater Caribbean area, there is no clear gradient with latitude at least up to the latitudinal limits of coral growth. About half the species are widespread throughout the Indian Ocean. Species frequency/distribution curves and cumulative frequency curves show that 150 species occur at only 2–4 sites. Multi-dimensional scaling (MDS) analysis using only these species confirms that they are important in forming sub-regional groupings which are superimposed on a general Indian Ocean homogeneity.The perennial problem of error in taxonomic data sets is examined. Increasing taxonomic error is introduced into the data using random methods. It is found that about 25% more error can be added to this data set before the relationship between similarity coefficient and geographical distance between pairs of sites is lost. Measures extracted from the clustering procedure using the original data and the data sets with added taxonomic error, show a sharp loss in cluster formation after addition of about 10 or 20% more error.  相似文献   

14.
    
Correlations between surface behavior and concurrent underwater vocalizations were modeled for common dolphins (Delphinus spp.) in the Southern California Bight (SCB) over multiple field seasons. Clicks, pulsed calls, and whistles were examined, with a total of 50 call features identified. Call features were used to classify behavior using random forest decision trees, with rates of correct classification reaching 80.6% for fast travel, 84.6% for moderate travel, 59.8% for slow travel, and 58% for foraging behavior. Common dolphins spent most of their time traveling. The highest number of clicks, pulsed calls, and complex whistles were produced during fast travel. In contrast, during foraging there were few pulsed calls and whistles produced, and the whistles were simple with narrow bandwidths and few harmonics. Behavior and vocalization patterns suggest nocturnal foraging in offshore waters as the primary feeding strategy. Group size and spacing were strongly correlated with behavior and rates of calling, with higher call rates in dispersed traveling groups and lower call rates in loosely aggregated foraging groups. These results demonstrate that surface behavior can be classified using vocalization data, which builds the framework for behavioral studies of common dolphins using passive acoustic monitoring techniques.  相似文献   

15.
Sightings of white-sided ( Lagenorhynchus acutus ) and common dolphins ( Delphinus delphis ) from survey vessels operating on the continental shelf of the northeastern United States were recorded during spring and fall of six years. Distributions of these sightings were compared with sea surface temperature and salinity, and bottom topography. The apparent geographic distributions of the two species are complementary, although there is a broad overlap. White-sided dolphins occurred primarily within the Gulf of Maine, but also on Georges Bank and in the mid-Atlantic region. Common dolphins were abundant within a broad band paralleling the continental slope (100–200 m depth contour) from latitude 35°N to the northeast peak of Georges Bank. Sightings of this species were distributed primarily along the edge of the continental shelf south of 40°N in spring and north of this latitude in fall. Few sightings of common dolphins occurred in the Gulf of Maine.
Although both species of dolphins were sighted more frequently in areas of high sea floor relief, white-sided dolphins occurred in areas where sea surface temperatures and salinities are low while common dolphins were sighted in warmer, more saline waters. However, these environmental conditions may be only secondarily influencing dolphin distribution. Seasonal variation in sea surface temperature and salinity, and local nutrient upwelling in areas of high sea floor relief may affect preferred prey abundances, which in turn may affect dolphin distribution.  相似文献   

16.
  总被引:1,自引:2,他引:1  
Data collected by scientific technicians aboard tuna purse seiners in the eastern Pacific Ocean since the early 1970s have allowed us to study the biology and herd dynamics of pelagic dolphins. A pattern of increasing group size in the morning and subsequent decline in the late afternoon or night was evident for spotted, spinner, and common dolphins, as well as for large yellowfin tuna that associate with dolphins. Diel patterns were also apparent in the formation of mixed-species herds of spotted and spinner dolphins and tuna-dolphin aggregations. Different patterns, however, were displayed by bottlenose dolphins and by yellowfin and skipjack tunas that did not associate with dolphins. It appears that these diel patterns are produced by an interaction of predation pressure and prey distribution.  相似文献   

17.
18.
主要组织相容性复合体(Major histocompatibility complex,MHC) 基因是由一组紧密连锁的基因组成,是哺乳动物免疫系统中最重要的组成部分。本文选择3 个MHC 基因座位的第二外元,即:MHC-I 类基因和II 类基因的DRA 和DQB 座位,初步调查濒危物种中华白海豚的遗传变异。共鉴定了2 个DRA、2 个DQB 和7 MHC-I等位基因。DRA 座位遗传变异非常低,而DQB 和MHC-I 座位具有相对较高水平的遗传变异。并且,在DQB 和MHC-I 基因座位的假定的抗原结合位点(Antigen binding sites,ABS),非同义替代明显大于同义替代,提示平衡选择(Balancing selection)维持这两个座位的多态性,而在DRA 座位上,并没有检测到平衡选择。系统发生分析表明中华白海豚的MHC 等位基因没有聚在一起,而是和其他的物种聚在一起,符合MHC 跨种进化(Transspecies evolution)的模式。  相似文献   

19.
On February 2,2015, a dead female Indo-Pacific humpback dolphin (Sousa chinensis) was found in the coastal water of Meilian Village, Yacheng Town, Sanya City, Hainan Province, China. It was the first Indo-Pacific humpback dolphin death case ever found in waters southwest of Hainan Island. In the present study, data about external morphology and skeleton system of the dead dolphin were documented, Body length and body mass of the animal were 235.0 cm and ca. 150 kg, respectively, with completely white body color. The cranium of this dolphin wa 189 mm in zygomatic width, and 415 mm in skull length. Its vertebra formula was C6+T12+L10+Ca20=48. It had 12 pairs of ribs and 11 V-bones. According to previous reports, our skeleton sample may have one cervical vertebra missing, and one or more caudal vertebras and V bones missing. More new skeleton samples from the same population are needed to confirm this presumption.  相似文献   

20.
  总被引:3,自引:0,他引:3  
A controlled experiment was carried out in 1996–1997 to determine whether acoustic deterrent devices (pingers) reduce marine mammal bycatch in the California drift gill net fishery for swordfish and sharks. Using Fisher's exact test, bycatch rates with pingers were significantly less for all cetacean species combined ( P < 0.001) and for all pinniped species combined ( P = 0.003). For species tested separately with this test, bycatch reduction was statistically significant for short-beaked common dolphins ( P = 0.001) and California sea lions ( P = 0.02). Bycatch reduction is not statistically significant for the other species tested separately, but sample sizes and statistical power were low, and bycatch rates were lower in pingered nets for six of the eight other cetacean and pinniped species. A log-linear model relating the mean rate of entanglement to the number of pingers deployed was fit to the data for three groups: short-beaked common dolphins, other cetaceans, and pinnipeds. For a net with 40 pingers, the models predict approximately a 12-fold decrease in entanglement for short-beaked common dolphins, a 4-fold decrease for other cetaceans, and a 3-fold decrease for pinnipeds. No other variables were found that could explain this effect. The pinger experiment ended when regulations were enacted to make pingers mandatory in this fishery.  相似文献   

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