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At least 73 records · Page 4Linked to original sources
PubMed1984

Morphogenesis and morphology of the brain stem nuclei of Cetacea. II. The nuclei of the accessory, vagal and glossopharyngeal nerves in baleen whales.

The development and final structure of the IXth, Xth and XIth cranial nerve nuclei are studied in ironhematoxylin -, thionin - and protargol -stained serial sections of about 50 baleen whale fetuses (blue whale, Balaenoptera musculus, and fin whale, Balaenoptera physalus ) and one adult fin whale. The nucleus ambiguus is composed of three subdivisions, oral, intermediate and caudal, the last mentioned being contiguous caudally with the dorsal motor Xth nucleus. The oral division develops as three parallel cell columns which merge into a well circumscribed solitary structure with a rostrally expanded "head". It is composed of medium-sized multipolar neurons in a myelin-poor neuropil. In the fin whale a minor group of larger cells is found medial to the "head". In both species a peculiar small-celled nucleus rich in capillaries is found ventral to the "head". The intermediate division initially contains a lateral cell column and a medial region of scattered cells. The lateral column persists throughout life, while the medial field develops into three columns only one of which remains distinct in mature individuals. The cells are larger than in the oral division with the largest cells in the medial column. The two columns are surrounded by a field of scattered neurons which continues without a sharp border into the caudal division which is composed of scattered cells throughout. In its rostral half the cells are of the same multipolar type as in the intermediate division while caudally they appear flattened in the horizontal plane. The dorsal motor Xth nucleus develops as three longitudinal columns. In the fetal brain these are cytologically distinct due to different proportions of small, medium-sized and larger multipolar neurons. The spindle-shaped ventromedial column extends the entire length of the nucleus. It is composed mostly of small to medium-sized cells which caudal to the obex are elongated parallel with the neuroaxis . The dorsolateral and ventrolateral columns are restricted to the middle 1/3 of the nucleus, except in the blue whale where the former extends somewhat more rostrally. They are both characterized by the presence of large multipolar cells, the largest of which are found in the ventrolateral column. In adult specimens the cells are more equally sized and the columnar organization less distinct. The nucleus of the tractus solitarius is of about the same length as the two above mentioned nuclei. Except at the very early stages, the nucleus is ill-defined.(ABSTRACT TRUNCATED AT 400 WORDS)

Accessory Nerve↗
PubMed1977

Morphogenesis and morphology of the brain stem nuclei of Cetacea. I. The hypoglossal nucleus.

1. The hypoglossal nucleus of whalebone whales is composed of four major subdivisions, forming four parallel columns, here called the dorsomedial, the dorsolateral, the ventromedial and the ventrolateral XII columns. 2. The ventromedial XII column extends throughout the hypoglossal nucleus, forming in whalebone whales the rostral as well as the caudal end of the nucleus. 3. The ventrolateral XII column is lamelliformed and splits into a dorsomedial and a ventrolateral part, the former intimately related topographically to the dorsomedial column. 4. The dorsomedial XII column is torpedo-shaped, tapering in rostral direction and terminating a little short of the rostral end of the ventromedial XII column, while the blunt end terminates immediately caudal to the obex. 5. The dorsolateral XII column is the shortest subdivision, approximately one fourth of the length of the entire hypoglossal nucleus. The blunt rostral end of the torpedo-shaped column blends with the dorsomedial XII column, its tapering caudal end terminating rostral to the obex. 6. The cells of the hypoglossal nucleus vary in size from small to medium-sized and large, the small ones dominating in the dorsomedial, the large ones in the dorsolateral and ventromedial XII columns. The ventrolateral column is characterized by spindle-shaped cells. 7. In the toothed whale Phocaena communis the differentiation of the hypoglossal nucleus is less clearcut than in whalebone whales, but a similar structural priniciple is recognizable.

Animals↗
PubMed1978

Myology of the shoulder of Pontoporia blainvillei, including a review of the literature on shoulder morphology in the cetacea.

The purpose of this paper is to describe in detail the shoulder myology of the La Plata River Dolphin, Pontoporia blainvillei, and to review the literature on cetacean shoulder myology. Three fetal and one adult animal were used for the collection of morphological information. Pontoporia is less specialized in its shoulder anatomy that most delphinid cetaceans, and shares several characteristics with some mysticetes. The omohyoid and anterior serratus anterior muscles are found in both Pontoporia and the mysticete Balaenoptera, but are absent in most delphinids. The pectoralis abdominalis and three rhomboideus divisions are found in Pontoporia and Kogia, but in only a few delphinid species described in the literature. It is suggested that these characteristics are associated with a generalized use of the forelimb in Pontoporia.

Animals↗
PubMed1995

Prenatal development of the integument in Delphinidae (Cetacea: Odontoceti).

The prenatal development of epidermis, dermis, and hypodermis was studied in embryos of different age of two delphinid species (Stenella attenuata, Delphinus delphis), using light and transmission electron microscopical methods. The delphinid embryo is covered by a multilayered tissue formed by four different epidermal generations (periderm, stratum intermedium-I, str. intermedium-II, str. spinosum) produced by the str. basale. The first layer appears at about 40-50 mm of body length, the second type (s.i.-I) about 60-160 mm, and the third type (s.i.-II) is present at 160-500 mm. The first spinosal cells are produced at 225-260 mm body length; thenceforth, the epidermis increases continuously in thickness. Epidermal ridge formation begins about 400-mm body length. The development of the dermis is characterized by the early production of thin connective tissue fibers (40-70-mm body length) and simultaneously the cutaneous muscle matures in structure. Vascular development intensifies between embryos of 150-225 mm, and collagen production increases markedly in fetuses of 225-260-mm length. These events are paralleled by an increase in dermal thickness. The first elastic fibers can be recognized in the skin from the abdomen at about 600-mm body length. The development of the hypodermis is marked by very rapid and constantly progressing growth, beginning about 60-mm body length. The first typical fat cells appear in animals of 360-400 mm. Regional differences are obvious for all skin layers with regard to the flippers, where structural maturation proceeds more rapidly than in dorsal or abdominal regions.

Animals↗
PubMed2002

Comparison of lipids in selected tissues of the Florida manatee (Order Sirenia) and bottlenose dolphin (Order Cetacea; Suborder Odontoceti).

The position, porosity and oil-filled nature of the zygomatic process of the squamosal bone (ZPSB) of the Florida manatee, Trichechus manatus latirostris, suggest that it may have a similar sound conduction function to that of the intramandibular fat body (IMFB) of the bottlenose dolphin, Tursiops truncatus, and other odontocetes. To examine this possibility we determined the lipid composition of the ZPSB and adipose tissue from the dorsal part of the head region of the Florida manatee, and compared it to that of the dolphin IMFB and melon (another fatty area implicated in sound conduction in odontocetes). Lipids from manatee ZPSB and from adipose tissue were composed almost entirely of triacylglycerols. The most abundant fatty acids of the ZPSB were 18:1, 16:0, 14:0 and 16:1. The major fatty acids of the adipose tissue in the head were the four mentioned above, along with 12:0 and 18:0. Manatee samples did not contain isovaleric acid (iso-5:0), which was found in the bottlenose dolphin IMFB and melon, and has been related to sound conduction in dolphins and some other odontocetes. Thus, if manatee tissues are capable of sound conduction, and this process does occur through the ZPSB, a somewhat different suite of lipid components must support this function.

Adipose Tissue↗
PubMed1997

Matriarchal genetic population structure of North American beluga whales Delphinapterus leucas (Cetacea: Monodontidae).

The North American beluga whale Delphinapterus leucas population has been divided into a number of putative geographical stocks based upon migration routes and areas of summer concentration. Nucleotide sequences of the mitochondrial DNA (mtDNA) control region were used to assess whether these geographical stocks are genetically distinct. Beluga whale samples from 25 sites were collected primarily from aboriginal subsistence hunts across North America from 1984 to 1994. Thirty-nine mtDNA haplotypes were identified in 628 beluga samples. No differences were found in the distribution of haplotypes between male and female beluga whales at any sampling site. These haplotypes segregated into two distinct assemblages in both a haplotype network and a neighbour-joining tree. The haplotype assemblages and a geographically disjunct distribution that suggests postglacial recolonization of the North American Arctic from two different refugia. An analysis of molecular variance based on haplotype relationships and frequency indicated genetic heterogeneity among beluga whale summering groups (P < or = 0.001). Sequence divergence estimates between sampling sites also indicated geographical differentiation, particularly between samples taken at east Hudson Bay or St Lawrence River and the western or central Arctic. The results of this study show a high degree of philopatry to specific summering areas by this highly mobile animal.

Animals↗
PubMed1998

Molecular genetic identification of southern hemisphere beaked whales (Cetacea: Ziphiidae).

To assist in the species-level identification of stranded and hunted beaked whales, we compiled a database of 'reference' sequences from the mitochondrial DNA control region for 15 of the 20 described ziphiid species. Reference samples for eight species were obtained from stranded animals in New Zealand and South Australia. Sequences for a further seven species were obtained from a previously published report. This database was used to identify 20 'test' samples obtained from incompletely documented strandings around New Zealand. Analyses showed that four of these 'test' specimens (20%) had initially been misidentified. These included two animals of particular interest: (i) a Blainville's beaked whale (Mesoplodon densirostris), the first record of this species in New Zealand waters; and, (ii) a juvenile Andrews' beaked whale (Mesoplodon bowdoini), a species known from just over 20 strandings worldwide. A published sequence from a beaked whale product purchased in the Republic of Korea was identified as a Cuvier's beaked whale (Ziphius cavirostris). Levels of intra- and interspecific variation were compared to determine the potential for misidentification when the database or taxonomy is incomplete. Intraspecific variation was generally < 2%, and interspecific divergence was generally > 4.7%. Exceptions were within-species variation in Hyperoodon planifrons, southern bottlenosed whale (4.12%), which exceeded the variation between the two species of Berardius (3.78%), and variation between the two specimens assigned to M. hectori, Hector's beaked whale (7.14%). The latter case appears to be an error in species identification, and could represent the discovery of a new species of beaked whale.

Animals↗
PubMed2000

[Crustacean parasites and epizoa of the sperm whale, Physeter catodon Linnaeus, 1758 (cetacea, Odontoceti), in the Gulf of Lion (Western Mediterranean)].

The authors point out for the first time, fixation of the Cirriped Conchoderma virgatum (Spengler, 1790) on an Amphipod Cyamid parasite of a young sperm-whale, Physeter catodon Linnaeus, 1758, stranded on the gulf of Lion coast (Western Mediterranean). Using the scanning electron microscope, they furnish precisions on the morphology and they furnish some observations concerning reproduction and biogeography of this Amphipod, Neocyamus physeteris (Pouchet, 1888).

Animals↗
PubMedDate not supplied

Molecular identification of evolutionarily significant units in the Amazon River dolphin Inia sp. (Cetacea: Iniidae).

The Amazon river dolphin, genus Inia, is endemic to the major river basins of northern South America. No previous studies have focused on the genetic structure of this genus. In this work, 96 DNA samples from specimens of this genus were collected in the Orinoco basin (four rivers), the Putumayo River, a tributary of the Colombian Amazon and the Mamoré, and the Tijamuchí and Ipurupuru rivers in theBolivian Amazon. These samples were used to amplify a fragment of 400 bp of the mitochondrial DNA (mtDNA) control region. In addition, 38 of these samples were also used to sequence 600 bp of the mitochondrial cytochrome b gene. The analysis of the population structure subdivision with an analysis of molecular variance (AMOVA) revealed important aspects about the genetic structure of Inia groups fromthese three geographically separate regions. By comparing the control region DNA and cytochrome b sequences, distinct types of nonshared haplotypes were observed. The net genetic divergence of control region sequences was 6.53% between the Orinoco and Bolivian rivers, 5.32% between the Putumayo and Bolivian rivers, and 2.50% between the Orinoco and Putumayo rivers. For the cytochrome b gene, these values were 2.48%, 2.98%, and 0.06%, respectively. The nucleotide sequences were analyzed phylogenetically using several genetic distance matrices and applying neighbor-joining, maximum likelihood, and maximum parsimony procedures. The results support the proposal to subdivide the Inia genus into at least two evolutionarily significant units: one confined to the Bolivian river basin and the other widely distributed across the Amazon and Orinoco basins.

Animals↗