Rough-toothed Dolphins Steno Bredanensis Research Articles

Summer and winter surveys of deep waters of the Hellenic Trench, Greece, provide insights into the spatial and temporal distribution of odontocetes

The Mediterranean Sea provides habitat for globally threatened cetaceans. The Hellenic Trench is an Important Marine Mammal Area, providing core habitat for sperm whalesPhyseter macrocephalusand Cuvier’s beaked whalesZiphius cavirostris. Surveys have characterized distributions of these species in near-shore areas (<2000 m deep). Sparse survey effort in deeper waters during winter has allowed speculation that it is not an important habitat in winter. We used passive acoustic monitoring from towed arrays to document cetaceans during summer and winter, covering 18366 km of trackline off the Peloponnese and Crete. We confirmed the acoustic presence of 5 odontocetes: sperm whales (n = 49 encounters; mean depth (x̄): 3360 m; range (R): 1250 to 4210 m), Cuvier’s beaked whales (n = 4;x̄: 3070 m;R: 1970 to 3770 m), Risso’s dolphinsGrampus griseus(n = 5;x̄: 3340 m;R: 2250 to 4440 m), striped dolphinsStenella coeruleoalba(n = 2;x̄: 2980 m;R: 2490 to 3470 m) and rough-toothed dolphinsSteno bredanensis(n = 1; 3650 m). We also encountered 224 unidentified delphinids, including a potential blackfish (3020 m). We confirmed that these species are present in the Hellenic Trench throughout the year. Given the impact of multiple threats on sperm and Cuvier’s beaked whales in the Hellenic Trench, we suggest that policymakers follow the precautionary approach in managing human activities in the area. Ongoing seismic surveys, hydrocarbon extraction and uncontrolled shipping could have potentially negative effects on these species at the population level and we advise caution in permitting such activities in future

Cetacean sightings from Mozambican waters, including the first records of Rough-toothed Dolphin Steno bredanensis and Fraser’s Dolphin Lagenodelphis hosei

Opportunistic cetacean sightings were made during a 79-day fishing trip through southern and central Mozambican waters. Notable sightings included the first Mozambican records of Rough-toothed Dolphin Steno bredanensis and Fraser’s Dolphin Lagenodelphis hosei, although both species have been recorded from neighbouring South African and Tanzanian waters. A number of other rarely seen cetacean species, with few Mozambican records, were also recorded.

Pathological and Genomic Findings of Erysipelothrix rhusiopathiae Isolated From a Free-Ranging Rough-Toothed Dolphin Steno bredanensis (Cetacea: Delphinidae) Stranded in Korea.

Erysipelas, caused by Erysipelothrix rhusiopathiae, is considered one of the most serious infectious diseases of captive and free-ranging cetaceans worldwide, as these animals are known to be highly susceptible to the bacterial infections. The potential diversity between E. rhusiopathiae isolates from captive cetaceans has been previously described; however, the microbiological features of the free-ranging cetacean isolates remain unclear. Here, we describe a case of bacteremia in a rough-toothed dolphin (Steno bredanensis) caused by E. rhusiopathiae. Additionally, we present the first genomic features of the bacteria from free-ranging cetacean individuals. Histopathological and microbial examinations revealed that E. rhusiopathiae caused bacteremia and systemic infection in the dolphin. The genome of the isolated E. rhusiopathiae strain KC-Sb-R1, which was classified as Clade 1 possessing SpaB gene, was clearly differentiated from the other swine-isolated E. rhusiopathiae, and the comparison of its serovar-defining chromosomal region revealed that our isolate was greatly similar to those of other previously reported serovar 2/15 isolates, including the captive-dolphin isolate. Moreover, most of the potential virulence factors in the strain KC-Sb-R1 were similar to those in the strain Fujisawa. Further, a potential cytotoxicity of the isolate was confirmed, suggesting that marine mammal-isolated E. rhusiopathiae could possess strong pathogenic potential in other animals, including humans. These results would further increase our understanding on the risk factors for controlling zoonotic pathogens of emerging infectious diseases in captive or free-ranging cetaceans, and also provide important insight into the diversity of E. rhusiopathiae in animals.

Topography of the Ganglion Retinal Layer and Retinal Resolution in the Rough-Toothed Dolphin Steno bredanensis (Cetacea: Delphinidae)

Topography of the Ganglion Retinal Layer and Retinal Resolution in the Rough-Toothed Dolphin Steno bredanensis (Cetacea: Delphinidae)

ТОПОГРАФИЯ ГАНГЛИОЗНОГО СЛОЯ СЕТЧАТКИ И РЕТИНАЛЬНОЕ РАЗРЕШЕНИЕ У ГРЕБНЕЗУБОГО ДЕЛЬФИНА STENO BREDANENSIS (CETACEA: DELPHINIDAE)

Morphological investigation of the retinal ganglion layer in the rough-toothed dolphin Steno bredanensis was performed using the retinal wholemount technique. Mapping of the distribution density of ganglion cells revealed two areas of their concentration: in the nasal (544 cells/mm2) and temporal (594 cells/mm2) quadrants. Ganglion cell diameters ranged from 12 to 50 µm, with mean values varying from 20 to 29 µm in different areas. The obtained cell distribution density corresponded to a retinal resolution of 11’

A feeding association between Wilson's Storm-petrels Oceanites oceanicus (Kuhl, 1820) and Rough-toothed Dolphins Steno bredanensis (G. Cuvier in Lesson, 1828)

On 06 October 2012 a pod of Rough-toothed Dolphins Steno bredanensis (Delphinidae) was observed catching and tearing apart several Castin Leatherjacks Oligoplites saliens (Carangidae) near Montão de Trigo Island, northern coast of São Paulo, Brazil. The resulting floating masses of viscera attracted a feeding aggregation of 120-150 Wilson's Storm-petrels Oceanites oceanicus (Hydrobatidae), a transequatorial migrant passing through the area during October. This interspecific association has not been recorded before, although it could be expected given that S. bredanensis feeds on large fish and O. oceanicus is a known scavenger of kills made by cetaceans such as Killer Whales.

Age and growth of some delphinids in south-eastern Brazil

This study provides the first compilation on age and growth of some delphinids in south-eastern Brazil (18°25′S–25°45′S). A total of 154 delphinids were reported: 44 Atlantic spotted dolphin Stenella frontalis; 36 bottlenose dolphin Tursiops truncatus; 26 ‘Brazilian’ common dolphin Delphinus sp.; 20 rough-toothed dolphin Steno bredanensis; 16 Fraser's dolphin Lagenodelphis hosei; 3 false killer whale Pseudorca crassidens; 3 unidentified Stenella sp.; 2 pantropical spotted dolphin Stenella attenuata; 2 short-finned pilot whale Globicephala macrorhynchus; 1 spinner dolphin Stenella longirostris; and 1 striped dolphin Stenella coeruleoalba. Age was estimated by counting the number of growth layer groups present in the dentine in 74.5% of the sample. The growth of 92 individuals of the first five species was determined by the Gompertz model to length-at-age data. Stenella frontalis—the oldest specimen was 23 y and the asymptotic length of 224.4 cm predicted by growth curve occurred at about 20 y; T. truncatus—the oldest specimen was 26 y and the asymptotic length of 301.3 cm predicted by growth curve occurred at about 20 y; Delphinus sp.—the oldest dolphin was 18 y and the asymptotic length of 215.9 cm predicted by growth curve occurred at about 5–6 y; S. bredanensis—the oldest specimen was 24 y and the asymptotic length of 258.1 cm predicted by growth curve occurred at about 10 y; L. hosei—the oldest specimen was 19 y and the asymptotic length of 231.2 cm predicted by growth curve occurred at about 7–8 y. Only age was estimated for the other species. The age-at-length data for S. frontalis, Delphinus sp., S. bredanensis and L. hosei were consistent, suggesting a good agreement with previous work on these species. For T. truncatus, the age at asymptotic length obtained in this study might be confirmed by increasing the sample size. The information currently presented will contribute to further life history research of delphinids on the western south Atlantic coast.

Finding of a dead rough-toothed dolphin Steno bredanensis (Cuvier and Lesson, 1828), stranded on the south Morrocan coast

The rough-toothed dolphin Steno bredanensis (Cuvier and Lesson, 1828) inhabits tropical and warm-temperatures seas. However, in many of these places, the specie has not been recorded yet, so the distribution is based on scarce watching and stranding data. There are so few data of this species from around the world that the International Union for the Conservation of Nature (IUCN) catalogues this animal with Insufficiently Known status, which makes any observation of this species extraordinarily valuable. Most of the encounters with the rough toothed dolphin have taken place offshore (Addink & Smeenk, 2001; Ritter, 2002). Though there are records of shallow water watching, often associated with feeding behavior (Delgado Estrella, 1994), individual OR SINGLE stranding is not very common (Smeenk, pers. com.) but often they strand in groups (massive stranding) (Cadenat, 1949; Stinnintz et al., 2000; Manasijevic et al., 2002). Between the 4 and the 11 of September 2002 we took part in an expedition through the western coast of Morocco and the Western Sahara (De los Rios y Ocana, in prep.) searching for sea turtle nesting evidences and feeding ecology data. During this expedition, we found a rough-toothed dolphin Steno bredanensis, dead for several weeks. We would like to present here the results of our identification and study of the specimen. The coast of Tarfaya consists of a large sandy beach, full of sediments and debris due to strong currents. Almost any inert material is, therefore, washed ashore. Much plastic debris such as bags, bottles, etc., and even three hulks, stranded in less than half a mile, were found in the littoral area. From our starting point (waypoint N 27o 55 163 W 012o 53 048 ), walking to either side of the beach for about 2 km, we found two Loggerhead turtle (Caretta caretta) carcasses, one Common dolphin (Delphinus delphis) corpse, and another corpse later identified as a Rough-toothed dolphin, Steno bredanensis (Fig. 1). So, according to our observations and also to local fishermen, this long and sandy coast is an area where cetaceans and turtles usually strand throughout the year. Identification of a dolphin which is alive, recently stranded or dead for just a few days, is not very difficult, especially for experts. Unfortunately, most of the times, we find the animal many days after death, lying on the beach, burnt by the sun, and even with some showing. In these cases, we have to perform anatomical analysis in order to make a proper identification, and the best part to do that on the skull, where the most differential characteristics are concentrated. The carcass in question presented a level of putrefaction 3, as the skin was totally dry and petrified. The identification of the specimen turned out