摘要:

AbstractWe provided a water‐cornea interface to correct the usual aerial myopia encountered in fundus photography of marine mammal eyes. The 12Tursiopseyes were consistent for vascular structure, optic papillae, dimensional components and tapetal coloration. Multiple photographs were assembled to produce one ocular fundus typical ofTursiops truncatusand one forGrampus griseus.The eyes have a vestigial hyaloid vessel and an optic disc („blind spot”) that occupies the center of the fundus. The disc is bounded in both species by a vascular structure that is continuous with a (retrobulbar) perineural organ called the ophthalmic rete. The vascular trees of the fundus do not suggest an area of specialization for high resolution. Both species exhibit total tapetalization. Tapetal spectral reflectance did not vary betweenTursiops.There was, however, a difference between species in the short wavelength regions of the spe

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1987.tb00147.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractGrowth layer groups (GLGs) were counted in teeth from an adult male belukha whale (Delphinapterus leucas) that had lived for 23 yr in captivity and was estimated to have been 14 mo at capture. As defined here, GLGs are repeating areas of alternating opaque (denser) and translucent (less dense) dentin or cementurn, or nodes at the dentin‐cementum interface. A GLG involves at least one change from opaque to translucent, dense to less dense or ridge to groove, but may be further subdivided by incremental growth layers or laminations. Teeth were prepared by two techniques. Thick sections (longitudinal half sections) were examined with a dissecting microscope under reflected light. Thinner cross and longitudinal sections were x‐rayed and the plates scanned with a microdensitometer. Scanning electron photomicrographs were prepared from thick sections, but SEM proved to be the least useful technique. Counts of GLGs were variable because the laminations were numerous and some surface layers had been lost from wear. Thick‐ and thinner‐section techniques gave comparable results, and approximately 40 GLGs were counted consistently. Although captive environments are less variable than natural ones, our findings are further evidence that belukhas in the wild deposit more than one—and probably two—GL

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1987.tb00148.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe vaquita,Phocoena sinus, is a porpoise in the family Phocoenidae that lives only in the Gulf of California. The external appearance ofP. sinuswas unknown until 13 fresh specimens were recently examined. The most obvious morphological feature distinguishingP. sinusfrom its two congeners is the proportionately higher dorsal fin. The most striking features of the pigmentation pattern are the large black eye patches and the black upper and lower lip patches. In both areas, the pigmentation contrasts sharply with the surrounding light gray coloration. The total lengths of the specimens ranged from 70.3 cm (a neonate) to 143.5 cm (an adult female).

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1987.tb00149.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractAerial and underwater audiograms for two young female northern fur seals (Callorhinus ursinus) and one young female California sea lion(Zalophus californianus)were obtained with the same procedure and apparatus.Callorhinushears over a larger frequency range and is more sensitive to airborne sounds thanZalophusor any other pinniped thus far tested in the frequency range of 500 Hz to 32 kHz. Sensitivity ofCallorhinusto waterborne pure tones, ranging from 2 to 28 kHz, is equal or superior to all other pinnipeds tested in this same frequency range. LikeZalophus, the upper frequency limit for underwater hearing (as defined by Mastertonet al.1969) inCallorhinusis about one‐half octave lower than the three phocid species thus far tested.Callorhinus'upper frequency limit in air is about 36 kHz and under water it is about 40 kHz. Comparison of air and water audiograms showsCallorhinusis no exception to previous behavioral findings demonstrating that the „pinniped ear” is more suitable for hearing in water than in air. Similar toZalophusandPhoca vitulina, Callorhinusshows an anomalous hearing loss at 4 kHz in air. The basis for this insensitivity to airborne sounds at 4kHz and not at lower or higher frequencies is presumably caused by specialized middle ear mechanisms matching impedance for waterborne sounds. Critical ratio curves forCallorhinusare similarly shaped to ones obtained for humans but are shifted upwards in frequency. Compared to all other marine mammals thus far evaluated, the critical ratios forCallorhinusare the smallest yet rep

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1987.tb00150.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe relative abundance of the most common cetacean schools in the eastern tropical Pacific Ocean for 1977–1980 are estimated based on encounter rates with tuna purse‐seiners. No temporal trends were apparent in the relative abundance estimates. The geographic distributions for eight different school types are described. Multivariate statistical techniques are used to investigate interrelations between species and relationships to parameters of the physical environment. The results suggest three major species groupings: (1) an inshore grouping of bottlenose dolphins (Tursiops truncates), Risso's dolphin (Grampus griseus), pilot whales (Globicephala macrorhynchus) and, to a lesser extent, common dolphins (Delphinus delphis); (2) an offshore pelagic grouping of spotted and spinner dolphins (Stenella attenuateandS. longirostris); and (3) an association between pilot whales and common dolphins that overlaps the first grouping in inshore areas and also tends to be segregated from the second grouping. The results also suggest that relative densities of different school types are strongly related to physical environmental parameters, the most important being sea surface temperature, depth of the thermocline and thickness of the oxygen minimum la

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1987.tb00151.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1987.tb00152.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1987.tb00153.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1987.tb00154.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1987.tb00155.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Book review in this articleWhales and Dolphins of New Zealand and Australia. an Identification Guide. A. N. Baker.Guia Para el Reconocimiento de Cetaceos Del Mar Argentino. A. Lichter and A. Hooper.Mamiferos Marinos de Chile. W. Sielfeld K.The Whale Watcher's Handbook. Erich Hoyt. Illustrations by Pieter Folkens.The Sierra Club Handbook of Whales and Dolphins. S. Leatherwood and R. R. Reeves (paintings by L. Foster).

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1987.tb00156.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY