Risso's Dolphin Grampus Griseus Research Articles

TETRAPHYLLIDEAN PLEROCERCOIDS FROM WESTERN MEDITERRANEAN CETACEANS AND OTHER MARINE MAMMALS AROUND THE WORLD: A COMPREHENSIVE MORPHOLOGICAL ANALYSIS

Tetraphyllidean plerocercoids have occasionally been reported in marine mammals, but they have rarely been described in detail, and the ecological significance of these infections is unclear. We described plerocercoids collected from the mucosa of the terminal colon and rectum, the anal crypts, and the hepatopancreatic ducts of 7 striped dolphins Stenella coeruleoalba, 1 Cuvier's beaked whale Ziphius cavirostris, and 3 Risso's dolphins Grampus griseus from the Spanish Mediterranean. We also examined undescribed plerocercoids from 3 cetacean species from the Atlantic and the Pacific. All plerocercoids had a lanceolate body, and a scolex with an apical sucker and 4 sessile monolocular bothridia. The bothridia had free posterior edges and an accessory sucker at their anterior end. Under light microscopy, the bothridia of some Mediterranean specimens looked bilocular without accessory suckers, but a true accessory sucker was observed in histological sections. A principal component analysis revealed 2 stable clusters of specimens along the first principal component regardless of host species. These "large" and "small" morphotypes are thought to represent early migratory stages of Phyllobothrium delphini and Monorygma grimaldii. The similarity in scolex morphology, the observation of plerocercoids buried in intestinal regions close to the sites where M. grimaldii and P. delphini occur, and the coexistence of all larval forms in the same individual hosts would support this hypothesis. Future molecular analysis may confirm it.

Summer distribution and relative abundance of cetacean populations off north-west Scotland

A line transect survey was conducted in July/August 1998 to investigate the distribution and abundance of cetaceans off north-west Scotland. Over 2156.5 km of survey effort, 304 sightings were recorded of which 184 were identified to species. Nine species were identified: Atlantic white-sided dolphin Lagenorhynchus acutus, fin whale Balaenoptera physalus, sei whale Balaenoptera borealis, long-finned pilot whale Globicephala melas, sperm whale Physeter macrocephalus, common dolphin Delphinus delphis, harbour porpoise Phocoena phocoena, white beaked dolphin Lagenorhynchus albirostris and Risso's dolphin Grampus griseus. The Atlantic white-sided dolphin was the most relatively abundant species. The relative abundance of large whales and dolphins was greatest in the Faroe–Shetland Channel. The continental slopes of this area are undergoing development by oil industries and concerns have been raised about the potential impacts of these activities on cetaceans. These waters are used year-round by cetaceans and provide feeding and breeding grounds and are a migration route for large whales.

Gastrointestinal helminths of Risso's dolphin Grampus griseus from the Western Mediterranean

The gastrointestinal helminth fauna of 17 Risso's dolphins Grampus griseus (Cuvier, 1812) from the Western Mediterranean was analysed. Five helminth species were found. Adults and juveniles of Hadwenius delamurei were collected from the duodenum of 7 animals. Adults were located significantly more anteriorly than juveniles, which is compatible with a previous hypothesis that species of Hadwenius undergo an ontogenetic migration towards the anterior duodenum. Eggs from Pholeter gastrophilus appeared in 1 small cyst in the main stomach. Adults of Tetrabothrius forsteri and Trigonocotyle globicephalae were collected from the duodenum of 1 and 4 individuals, respectively. Metacestodes, Scolex pleuronectis, were found in the liver, pancreas, pyloric stomach and intestine of 13 individuals. The most favored locations were in the mucosa of the terminal colon and in anal crypts. It is likely that worms select these locations to reach the mesenteries and blubber of the anogenital area, where S. pleuronectis might become Monorygma and/or Phyllobothrium. Two individuals of Stenurus globicephalae occurred in the intestine of 1 individual, and were probably swallowed accidentally. The intestinal helminth communities of Risso's dolphin are depauperate. The parasite species found also occur in other oceanic cetaceans from the Western Mediterranean. However, H. delamurei and T. globicephalae are only shared with pilot whales Globicephala spp., which are phylogenetically closely related to Risso's dolphins.

Disseminated Toxoplasmosis in a Mediterranean Pregnant Risso's Dolphin (Grampus griseus) with Transplacental Fetal Infection

Disseminated Toxoplasmosis in a Mediterranean Pregnant Risso's Dolphin (Grampus griseus) with Transplacental Fetal Infection

Distribution of Risso's dolphin (Grampus griseus, Cuvier 1812) in Chilean waters

En este trabajo se revisa la informacion del calderon gris Grampus griseus en aguas chilenas. En base al analisis de 44 registros, la distribucion a lo largo de la costa chilena parece ser continua entre los 20o13' S y 40o S, sugiriendo que los registros mas australes en Chile (~52oS) podrian corresponder a calderones grises provenientes del Oceano Atlantico. Los registros en Chile muestran un aumento durante el verano austral e indican una preferencia por aguas sobre los 1000 m de profundidad. Varamientos masivos, interacciones con pesquerias y asociaciones con otras especies de cetaceos son tambien revisadas.

Distribution of mercury in the organs and tissues of five toothed-whale species of the Mediterranean

Mercury levels were determined in the tissues and organs (lung, liver, kidney, skin, muscle, bone) of five toothed-whales stranded along the Corsican coast between November 1993 and February 1996. The species taken into consideration were the bottlenose dolphin Tursiops truncatus, the common dolphin Delphinus delphis, the striped dolphin Stenella coeruleoalba, the pilot whale Globicephala melas and the Risso's dolphin Grampus griseus. The variation in mercury levels between the different tissues and organs (lung, liver, kidney, skin, muscle, bone) of the cetacean species are discussed as regards storage, biotransformation and elimination. In all cases, the liver appears to be the preferential organ for mercury accumulation (with concentrations as high as 4250 μg Hg/g dw and 3298 μg Hg/g in the livers of Tursiops truncatus and Grampus griseus, respectively). The kidney and lung are the next organs in terms of mercury uptake followed by the muscle, bone and skin. The stomach contents of Grampus griseus and D. delphis were determined and consisted of cephalopods for Grampus griseus, and of sardines Sardina pilchardus and mackerels Trachurus sp. for D. delphis. Cephalopods had higher mercury concentrations (25.4 μg Hg/g dw) than fish (ca 1 μg Hg/g). These contents represent only one meal and mercury levels found in livers may integrate mercury uptake having occurred during the whole life span of animals.

The Stomach Contents of A Risso's Dolphin (Grampus Griseus) Stranded at Thurlestone, South Devon

Risso's dolphin (Grampus griseus) (Cuvier, 1812) is not common off the coast of Devon although strandings are occasionally reported. Norman & Fraser (1948) noted that 45 had been stranded on the British coast over a period of 33 years and that these were concentrated in the south-west. While it is regularly stated that this animal eats squids exclusively the prey species have not been identified. In view of the variety of squids available to an oceanic mammal and the information its food can give on both the migration of the dolphin and the ecology of the cephalopods in its diet the stranding of a Risso's dolphin at Thurlestone Rock on 12 May 1983 provided an unusual and welcome opportunity to examine the animal and its food.

A near mass stranding of cetaceans in St Helena Bay, South Africa

A group of 70 false killer whales Pseudorca crassidens and 124 bottlenose dolphins Tursiops sp., and a separate group of 13 Risso's dolphins Grampus griseus, assembled close inshore off a known mass-stranding site in St Helena Bay, South Africa, in October 2003. However, only a single Risso's dolphin attempted to strand and 13 bottlenose dolphins had to be shepherded out of the shallows the next day, the remainder leaving of their own accord. This is considered to be the first near-stranding phenomenon recorded for the region.