Dolphins Stenella Research Articles

A Morphological and 13C NMR Study of the Extramandibular Fat Bodies of the Striped Dolphin (Stenella coeruleoalba)

The molecular and histological structure of the fat bodies covering externally the posterolateral region of the jaw of the striped dolphin (Stenella coeruleoalba) was investigated by means of morphological and nuclear magnetic resonance techniques. The analyses of samples belonging to adult and juvenile individuals were performed with the aim of seeking the presence of age-related differences. In our study, the level of isovalerate (iso5:0) in the extramandibular fat of the juvenile individuals is comparable with those of the adult counterparts; conversely, longer isobranched fatty acids were detected in lower quantities in the juveniles together with a higher degree of unsaturation. The morphologic analyses revealed that, in both adults and juveniles, this fatty tissue is similar to univacuolar adipose tissue. However, in the juveniles, a muscular component was present, whereas only in adult subjects, enlarged and irregularly shaped cavities may be seen within the adipose tissue. These cavities, structurally organized as veins, may regulate blood flow in response to changing water temperature and stabilize thermal gradient within the jaw lipids. These data suggest that the molecular components and the histological organization can indicate a maturation of the organ with age that probably may reflect different sound reception properties.

Species records, mistaken identifications, and their further use: the case of the diskfish Echeneis naucrates on a spinner dolphin

The single record of the sharksucker (Echeneis naucrates) attached to a spinner dolphin (Stenella longirostris) is based on a photograph taken at Fernando de Noronha Archipelago, off northeast Brazil. A careful examination of this photograph demonstrates that the diskfish attached to the dolphin is the whalesucker (Remora australis), a species so far recorded on cetaceans only. Thus, the record of S. longirostris as a host for E. naucrates is here invalidated and the value of vouched records is reiterated. The exaggerated reliance even on refereed papers dealing with species records and checklists that lack or have dubious vouchers and their further use is commented upon.

Patterns of Use of Maku'a Beach, O'ahu, Hawai'i, by Spinner Dolphins (<I>Stenella longirostris</I>) and Potential Effects of Swimmers on Their Behavior

Spinner dolphins (Stenella longirostris) use Maku’a Beach, a small bight along the Waianae coast of O’ahu, as a rest site. Behavior and use patterns of Maku’a Beach by spinner dolphins and swimmers were studied in July and August of 1995 to provide baseline data on the dolphin population and to assess potential impacts of swimmers on the dolphins’ resting behavior. Dolphins were observed on 52 out of 53 days, and they entered the area between 0545 and 0845 h. Their departure time varied widely. Average school size was 67 ± 0.6 SE and decreased with time of day. The most common aerial behaviors were slaps, leaps, and spins, respectively, with a peak in aerial behavior in late afternoon associated with schools moving offshore. The number of swimmers in the study area was highest on weekend mornings (X – = 12 ± 0.6 SE), with a maximum of 63 people in the water at the same time. Rest appeared delayed and compressed in this population of dolphins as compared to other studies and may be a response to the presence of swimmers in the morning. The results suggest a potential adverse impact of swimmers on the dolphins’ resting patterns, with earlier departure times and shorter periods of dive behavior indicative of rest.

Temporal Variation in Atlantic Spotted Dolphin (<I>Stenella frontalis</I>) and Bottlenose Dolphin (<I>Tursiops truncatus</I>) Densities on the West Florida Continental Shelf

We surveyed Atlantic spotted dolphins (Stenella frontalis) and bottlenose dolphins (Tursiops truncatus) in an area of the west Florida continental shelf (82° to 84.5° W and 26° to 28° N) from November 1998 to December 2001. Objectives were to estimate relative abundances of these two species and test for seasonal and interannual variations in distribution. Monthly surveys were conducted over a three-year period between the coast and the 180 m depth contour. Abundances of Atlantic spotted dolphins and bottlenose dolphins were estimated using the software program Distance. Sightings from monthly surveys were pooled by years and by seasons within a year. Significant seasonal variations in Atlantic spotted dolphin densities were repeated across years, with lower abundances during the warm season (June-October), and higher densities during the cool season (November-May). Atlantic spotted dolphin densities significantly decreased during 2000, while bottlenose dolphin density trends were not apparent. These trends continued into 2001, suggesting differ

Vomiting Behavior of the Spinner Dolphin (<I>Stenella longirostris</I>) and Squid Meals

We describe and illustrate the vomiting behavior of the spinner dolphin (Stenella longirostris), an eliminative behavior poorly known for cetaceans in the wild. The vomiting may be conveniently described in six behavioral phases: opening beak, closing beak (water intake), swallowing water, pausing, opening beak about to void, and voiding offal and water. Spinners vomit after a meal rich in squids, and, therefore, we relate this eliminative behavior to the presumably irritating remains of this meal type (squid beaks). The vomits are a rich and predictable food source for plankton-eating reef fishes.

AGE AND LENGTH AT WEANING AND DEVELOPMENT OF DIET OF PANTROPICAL SPOTTED DOLPHINS, STENELLA ATTENUATA, FROM THE EASTERN TROPICAL PACIFIC

AbstractUsing stomach contents from 203 spotted dolphins (Stenella attenuata) killed in the yellowfin tuna fishery, we modeled the weaning process of calves. Spotted dolphins began to take solid food at approximately 6 mo of age, or 115 cm, but continued to suckle until they were nearly 2 yr old. Calves tended to feed more frequently on squid as they got older, which suggested there was a shift in diet during weaning. The average age and total body length at weaning was estimated to be 0.8 yr (approximately 9 mo) and 122 cm. The oldest suckling calf was almost 2 yr old, which suggests that some calves continued to suckle for more than a year after they could have been weaned. A better understanding of the weaning process, especially quantifying the period of time when calves are nutritionally dependent on their mothers may lead to a better evaluation of their potential vulnerability to the disturbance caused by the yellowfin tuna purse‐seine fishery.

Distribution of cadmium, copper, iron, manganese, lead, and zinc in spinner dolphins Stenella longirostris stranded in La Paz lagoon, southwest gulf of California.

Distribution of cadmium, copper, iron, manganese, lead, and zinc in spinner dolphins Stenella longirostris stranded in La Paz lagoon, southwest gulf of California.

Hepatic Sarcocystosis in a Striped Dolphin (Stenella coeruleoalba) from the Spanish Mediterranean Coast

Hepatic Sarcocystosis in a Striped Dolphin (Stenella coeruleoalba) from the Spanish Mediterranean Coast

The Lateral Enamel Lamina--Component of Tooth Primordia in Selected Mammalian Species

The lateral enamel lamina (LEL) is a part of the enamel organ, which is probably not involved in tooth formation. It represents, besides the "stalk" of the tooth primordium, a second interconnection between enamel organ and oral epithelium or vestibular lamina. We detected the LEL in the sheep ( Ovis aries ), the dolphin ( Stenella attenuata ), and the vole ( Microtus agrestis ) by light microscopy and computer-aided three-dimensional reconstruction. The LEL could be found in cap to bell stage tooth primordia, most clearly in slowly developing tooth germs. LEL-like structures have been furthermore described or depicted in tooth germs of the mouse, the elk ( Alces alces ), the dugong ( Dugong dugong ), the elephant ( Loxodonta africana ), and the human. Probably it is a part of all mammalian tooth primordia that undergoes regression during morphogenesis of the enamel organ. As a reducing structure, it should be considered in studies of tooth development.

Evolution of the metallic contamination of the striped Dolphins (Stenella Coeruleoalba) on the French Mediterranean coasts between 1990 and 1997

As part of a program monitoring the contamination of Cetaceans by heavy metals on the French Mediterranean coast, the levels of cadmium, copper, mercury, nickel, lead and zinc in nine striped dolphins (Stenella coeruleoalba), stranded dead on the beach in 1996 and 1997, have been worked out. The results obtained were compared to those of a similar study carried out in 1990 and 1991 on the same species. A significant decrease in the concentrations of copper, mercury, nickel and lead was shown, as well as a slight decrease in the concentrations of cadmium. Contamination by zinc was not lower and remain rather high. These results are most likely the consequence of the efforts made to clean up the coast, inadequat as it may be. Indeed, the metallic contents of the most contaminated dolphins still remain high and pose a toxicological problem which is discussed, with emphasis on mercury. Cetacean are reliable biological indicators and irrefutable evidence of the chronical poisoning of the sea and of the danger of high concentrations of some pollutants in the food chains.

Whales and dolphins (Mammalia, Cetacea) of the Cape Verde Islands, with special reference to the Humpback Whale Megaptera novaeangliae (Borowski, 1781)

Observations of whales and dolphins in the Cape Verde Islands obtained in 1995 and 1996 are reported and data on the occurrence of 14 taxa are given, including four not previously reported from the region, viz. Bryde’s Whale Balaenoptera edeni, Killer Whale Orcinus orca,Rough-toothed Dolphin Steno bredanensis, and Striped Dolphin Stenella coeruleoalba. An earlier report of Fin Whale B. physalus is reviewed and re-identified as B. cf. borealis. Status and occurrence of the Humpback Whale Megaptera novaeangliae are discussed at some length. Unpublished observations from other observers are also included and a short account on the history of whaling in the islands is given. A list of all cetacean taxa reliably recorded in the Cape Verde region is presented and unsubstantiated reports are briefly discussed.

Distribution of cetaceans in the offshore Gulf of Mexico

In order to comprehend better the distribution of Gulf of Mexico cetaceans, all available records of whales and dolphins in the offshore Gulf were assembled and analysed. This included sightings, strandings and captures of all species, except the Bottlenose Dolphin Tursiops truncatus, from all sources, except the recently completed GulfCet project. An attempt was made to confirm species identification for each of the records. A total of 1223 records was available for analysis. Twentyseven species of cetaceans have been confirmed to occur in the offshore Gulf of Mexico. All of the baleen whales, with the possible exception of the Bryde's Whale Balaenoptera edeni appear to be extralimital in the Gulf. The Sperm Whale Physeter macrocephalus is, by far, the most common great whale in this body of water. All previous records of Common Dolphins Delphinus spp. in the Gulf are rejected as either incorrect or unreliable, and there is currently no convincing evidence that dolphins of the genus Delphinus occur in the Gulf. The Atlantic Spotted Dolphin Stenella frontalis is the only species, other than the Bottlenose Dolphin, that regularly occurs over the continental shelf. The Pantropical Spotted Dolphin Stenella attenuata is the most common species of small cetacean in oceanic waters of the Gulf, but many other species also occur there in significant numbers.

PIXE ANALYSIS OF TRACE ELEMENTS IN CETACEAN TEETH

PIXE was adopted for analysis of trace elements in teeth of two species of cetaceans, sperm whale (Physeter macrocephalus) and pantropical spotted dolphin (Stenella attenuata). The analyses were performed along with the growth layer of the teeth, which is formed annually, suitable for age determination. Mn , Fe , Cu , Zn and Sr were detected in the teeth of sperm whale and pantropical spotted dolphin. Among these trace elements, gradual increase was observed for Zn/Ca ratio in the sperm whale's teeth.

A record of Striped Dolphin Stenella coeruleoalba (Meyen,1833) from the Turkish Mediterranean Sea coast

The mummified carcass of a pregnant female of the Striped Dolphin Stenella coeruleoalba was found on the beach of the Göksu delta (Silifkce, Turkey, Mediterranean Sea) on 25 July 1996. This appears to be the first published record for Turkey.

A comparative study on liver ornithine carbamoyl transferase from a marine mammal Stenella and an elasmobranch Sphyrna zygaena

1. 1. Ornithine carbamoyl transferases from liver of the dolphin Stenella and the shark Sphyrna zygaena were purified to homogenity and compared for some kinetic and structural properties. 2. 2. The two enzymes showed a specific activity of 211 and 115 respectively. 3. 3. With respect to molecular weight, trimeric subunit structure and K m values, they were alike and similar to enzymes from other species. 4. 4. Both enzymes were thermolable, but they were protected from thermal inactivation in a different way by ornithine and phosphate. 5. 5. The two enzymes focused, respectively, at pH 8.6 and between pH 6.4 and 8.0, the former value being appreciably higher than those of enzymes from other species.

Prevalence of morbilliviruses among pinniped and cetecean species

Since 1987, morbillivirus infections have caused serious disease outbreaks with high mortality among aquatic mammals. Baikal seals (Phoca sibirica) in Siberia were involved in an outbreak caused by a virus closely related to canine distemper virus (CDV) in 1987. Harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus) in north-western Europe were struck by a newly recognised morbillivirus of seals (PDV1). A serological survey has indicated that these morbillivirus infections frequently occur among several pinniped species. Besides pinnipeds, the presence of morbillivirus infections among cetaceans, including whales, dolphins and porpoises, has been demonstrated since the outbreak of PDV among seals in north-western Europe. Morbillivirus was isolated from several stranded harbour porpoises (Phocoena phocoena). This virus proved to be very similar to a virus which was isolated during a disease outbreak with high mortality among striped dolphins (Stenella coeruleoalba) in the Mediterranean area. The viruses isolated from these cetacean species were quite different from the viruses isolated from the seals. They proved more related to the ruminant morbilliviruses, peste des petits ruminants virus and rinderpest virus. The potential transmission of the dolphin morbillivirus to the endangered population of the Mediterranean monk seal (Monachus monachus) has been considered. Studies are presently being conducted into the possibility of inducing protection against morbillivirus infection in this species by vaccination with an immune stimulating complex (ISCOM) preparation based on CDV.

Variation in Spinner Dolphins (Stenella longirostris) from the Eastern Tropical Pacific Ocean: Sexual Dimorphism in Cranial Morphology

Four meristic and 32 morphometric cranial characteristics were analyzed for sexual dimorphism in 200 adult spinner dolphins ( Stenella longirostris ) from the eastern tropical Pacific Ocean (ETP). Specimens were first separated into “whitebelly” and “eastern” forms based on external criteria and compared in a two-way ANOVA of color versus sex. Differences between the two color forms were minor, thus allowing the specimens to be pooled for subsequent analyses of sexual dimorphism. We assessed animals from nine 5° latitude-longitude blocks containing four or more individuals with a two-way ANOVA involving sex and geographic block. Sexual dimorphism was significant in 13 of the 36 characters and ranged from 0.04 to 11.32% difference. We could correctly identify 67% to 69% of the specimens to sex based on a discriminant function involving six characters (three rostral widths, a tooth width, the length of the temporal fossa, and one braincase measure). Classification functions are included to classify unknown specimens to sex. In addition, correction terms are included that will enable investigators to adjust measurements and factor out sexual differences in studies where it is advantageous to treat the sexes simultaneously. Trends in sexual dimorphism were very similar to those found in spotted dolphins ( S. attenuata ) from the same geographic region, although the differences were less pronounced in the spinners.

Differentiation between Inshore and Offshore Spotted Dolphins in the Eastern Tropical Pacific Ocean

Multivariate analyses were performed on 36 morphometric and meristic skull measurements taken on 613 spotted dolphins ( Stenella attenuata ) from the eastern tropical Pacific Ocean. Corrections were made to account for sexual dimorphism. Findings extend previous results which indicate sharp demarcation between two stocks: a larger, more robust coastal or inshore form; and a smaller, more terete pelagic or offshore stock. Sample means from 5° latitude-longitude blocks were projected onto principal component I and showed separation of four inshore from 19 offshore blocks, primarily on the basis of size involving most morphometric characters. A second component with high loadings on tooth counts summarized differences of three southern inshore blocks (adjacent to Central America) from a fourth, more northerly block located at the Gulf of California. Cluster analyses provided a similar summary of interblock associations. Principal components and cluster analysis based on individual specimens were also used to identify seven individuals with questionable affinity. The remaining 606 specimens (575 offshore, 31 inshore) were used to generate a discriminant axis and associated classification functions that correctly allocated all specimens. The best character for distinguishing between offshore and inshore specimens is Tooth Width. Classificatory information is provided to enable other researchers to assign unknown specimens.

Ecological Aspects of Smaller Cetaceans, with Emphasis on the Striped Dolphin (Stenella coeruleoalba)

The striped dolphin (Stenella coeruleoalba) is captured by drive fisheries as it migrates along the coast of Japan. The largest school of striped dolphins captured contained 2838 individuals. Annual catches have reached approximately 20,000 striped dolphins, and it is estimated that the population fished must number 400,000–600,000 animals. Recent variations in catch levels have resulted from economic and environmental fluctuations, not from a decrease in population size.

Mercury, DDT, Dieldrin, and PCB in Two Species of Odontoceti (Cetacea) from St. Lucia, Lesser Antilles

Samples of blubber, muscle, liver, and kidney of short-finned pilot whale Globicephala macrorhyncha and long-snouted dolphin Stenella (longirostris ?) from waters adjacent to St. Lucia, Lesser Antilles, were analyzed for Hg, DDT, dieldrin, and PCB. Total Hg levels were high, ranging from 1.33 to 5.36 ppm in muscle (methylated fraction 42–100%), 2.28 to 14.00 ppm in kidney (methylated fraction about 14%), and 13.00 to 157.00 ppm in liver (methylated fraction 2–17%). ΣDDT in blubber ranged from 1.25 to 7.38 ppm, dieldrin in blubber from 0.007 to 0.04 ppm, and PCB in blubber from 0.69 to 5.00 ppm. The presence of the high Hg levels is attributed largely to natural sources, as the Lesser Antilles Island Arc is a site of intense cyclic tectonic activity. There may be some contribution from atmospheric sources. Both DDT and PCB could be largely the result of atmospheric transportation from higher Atantic latitudes, although local DDT spraying programs may have contributed. Certainly the circulation pattern in the Gulf of Mexico and Caribbean appears to rule out water-borne transport from the river systems of the Gulf States of the United States.