DEVELOPMENT, SEXUAL DIMORPHISM, and INDIVIDUAL VARIATION IN THE SKELETON OF THE FINLESS PORPOISE, <i>NEOPHOCAENA PHOCAENOIDES</i>, IN THE COASTAL WATERS OF WESTERN KYUSHU, JAPAN

Yoshida, Hiderou; Shirakihara, Miki; Takemura, Akira; Shirakihara, Kunio

doi:10.1111/j.1748-7692.1994.tb00482.x

Cited by 28 publications

(35 citation statements)

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“…Individual variation: Individual variations of feeding and breathing apparatus were the greatest, and it is shown in finless porpoises (Neophocaena phocaenoides) [23] and spotted porpoises (Stenella attenuata) [17]. In addition, spotted seals have a great individual variation in the facial-expression apparatus with regard to movements of the nose and vibrissae, both of which play a unique role in the behaviors of pinnipeds.…”

Section: Discussionmentioning

confidence: 99%

“…Estimate the age to cease the cranial development: To estimate the age of completion of development on a particular character, we assumed the growth of skull virtually ceased at the age at which length attains 95% of its asymptotic length (t .95 ) [23]. T .95 was calculated from the estimates of growth parameters in each measurement.…”

Section: Methodsmentioning

confidence: 99%

“…12, 13, 18, 19, 20, and 22) could not be measured in some specimens. In order to overcome the small sample size, ANCOVA was carried out using data obtained from all age individuals, following the previous study [23].…”

Section: Methodsmentioning

confidence: 99%

“…Estimation of the age when development ceases will make it possible to use all the measurements from animals exceeding this age for a morphological comparison [23]. No such studies have, however, previously been conducted for spotted seals.…”

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Cranial Features of the Spotted Seal, Phoca largha, in the Nemuro Strait, Considering Age Effects.

Mizuno

Ohtaishi

2002

The Journal of Veterinary Medical Science

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ABSTRACT. Cranial features (development, individual variation, and sexual dimorphism) were examined from the 23 metrical characters and 2 nonmetrical characters (the degree of closure of the 9 cranial sutures and the presence of sagittal crest) in the two spotted seal specimen groups at the Nemuro Strait, Hokkaido. One specimen group was incidentally taken in the salmon trap nets between 1982 and 1983 (n=70), and the other was randomly sampled by damage control kill between 1997 and 1998 (n=82). The development of morphometrical characters of skulls ceased at 5. 6, 10.7, 7.9, and 11.9 yr. old, for 1982-83 male, 1982-83 female, 1997-98 male and 1997-98 female, respectively. The sutures were half ankylosed till approximately 10 yr. old in both sexes. The sagittal crest began from about 5 yr. old in male. Individual variation of skull was large in the feeding, breathing, and facial-expression apparatus. On the other hand, the variation of braincase, and skull concerning to the movement of head/neck tended to be small. Only 1997-98 specimens exhibited a sexual dimorphism in skull characters except for the braincase, whereas the dimorphism was not found in 1982-83 specimens. We could not detect the significant difference between two specimen groups, although there were a few differences in characters related to the rostrum and mandible. KEY WORDS: growth, individual variation, principal component analysis, sexual dimorphism, skull morphology.The spotted seal, Phoca largha, which is widely distributed in the Sea of Okhotsk, the Japan Sea, and the Bering Sea [20], exhibits regional variations in morphology. In the Bering Sea, the three geographical populations was found using non-metrical characters of skulls [5]. In the Sea of Okhotsk, it was confirmed of the cranial differentiation based on metrical and non-metrical characters between the northern area (Shelekhova Bay) and the southern area (Terpeniya Bay in Sakhalin) [6]. In the Japan Sea, cranial features in the Mamiya Strait concentration have been reported; almost characters did not show a sexual dimorphism except for the rostrum and nasal bone, and the skulls of female were larger than those in the Peter the Great Bay [12]. However, these studies used the sexual mature specimens, without consideration of the age-based cranial development. There are a few studies to describe the cranial developments. One study reported the development of condylobasal lengths with age [15]. Another study reported the developments of 17 cranial morphometric characters, and denied the sexual dimorphism of sexual mature seal [22], as well as the review study [2].Clarification of the development of morphometric characters provides the basic data for the analysis of geographical variations among neighboring populations. Estimation of the age when development ceases will make it possible to use all the measurements from animals exceeding this age for a morphological comparison [23]. No such studies have, however, previously been conducted for spotted seals.Offshore of Hokkaido, includ...

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Cranial Features of the Spotted Seal, Phoca largha, in the Nemuro Strait, Considering Age Effects.

Mizuno

Ohtaishi

2002

The Journal of Veterinary Medical Science

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“…To estimate the age of completion of development for a particular character, we assumed that growth virtually ceased at the age at which length reached 95% of its asymptotic length (t .95 ), following the previous studies [20,37]. We calculated t .95 from the estimates of growth parameters using the monomolecular model [20,24].…”

Section: Methodsmentioning

confidence: 99%

Age-Related Change and Allometry of Skull and Canine of Sea Otters, <i>Enhydra lutris</i>

Hattori

Burdin

Suzuki

et al. 2003

The Journal of Veterinary Medical Science

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ABSTRACT. Skulls and canines of 460 sea otters from Lopatka Cape, Kamchatka, were examined to assess development patterns, individual variation and sexual differences. An allometric formula was applied to morphometrical data, and the relative growth of each character to total length of skull was analyzed. In both sexes, most morphometrical characters ceased growth at about 2 years of age. Canine root length increased rapidly during the first year of life, while crown length decreased due to remarkable wear. There was large individual variation in the feeding and breathing/sniffing apparatus, while there was little variation in braincase size. There wer e sexual differences in most characteristics, although males and females showed similar growth patterns. The coronoid process of the mandible showed positive allometry in both sexes, and we attributed this finding to feeding habits. The fact that only male mastoids showed positive allometry may be due to the need for male otters to maintain a passing territory. KEY WORDS: allometry, Enhydra lutris, growth, morphology, skull.J. Vet. Med. Sci. 65(4): 439-447, 2003 The sea otter, Enhydra lutris, is a member of the Mustelidae, order Carnivora. It is highly adapted to the marine environment in a number of ways, including senses, feeding and behavior. Three subspecies of sea otters are commonly recognized: Asian (E. l. lutris), Alaskan (E. l. kenyoni) and southern sea otters (E. l. nereis) [2].Morphological studies of skulls of this species revealed geographic variation, and supported the above subspecies designations [3,18,29,36]. In most of these analyses, only adult specimens were used; the animals were considered adults if the basioccipital-basisphenoid suture was closed on the lower surface of the braincase [30]. Green [13] and Morejohn et al. [23] proposed criteria for relative age based on skull characters, tooth eruption and tooth wear. They used non-metric characters that indicate cessation of growth but not the age at which cessation occurred. The age of attainment of physical maturity is an important datum, because its variation can indicate changes in the nutritional condition of the population [25]. However, no detailed descriptions of age-related patterns of change have been available in sea otter skulls. Bodkin et al. [4] evaluated the accuracy and precision of using cementum layers of canine teeth to estimate sea otter age. They concluded that this method was sufficiently accurate for estimating age class distributions of relatively large samples.In this study, we used skull specimens to examine development of cranial structure in sea otters (E. l. lutris) in Lopatka Cape. We described growth over time, sexual differences and individual variation in the skulls and canines. Allometry was used to study relative growth of the different cranial components. We interpreted allometry coefficients as growth rates, although, in truth, they represented size rates. Discussion of our findings was based on functional grounds. MATERIALS AND METHODSWe analyzed 460...

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Occipital Ossification of Balaenopteroid Mysticetes

Walsh

Berta

2011

The Anatomical Record

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The bones of the posterior portion of the mammalian skull often exhibit incomplete ossification of the joints between the bones at the time of birth, with complete ossification at some point after birth. The sequence of ossification of these joints in mysticetes can be used to characterize the relative age in the calf and early juvenile ontogenetic stages. This study examined occipital joints ossification of 38 dry prepared neonate specimens in four mysticete species from two families (Eschrichtiidae: Eschrichtius robustus; Balaenopteridae: Balaenoptera acutorostrata, Balaenoptera physalus, and Megaptera novaeangliae). Each of the joints responsible for the fusion of the occiput were examined and rated for degree of ossification. The cranial ossification analysis indicates that E. robustus calves have open occipital joints until 6 months of age and are born at a less mature stage than closely related balaenopterids. All of the species followed the same sequence of ossification: basioccipital/exoccipital joint, followed by the basioccipital/basisphenoid joint, and completed by the supraoccipital/exoccipital joint. Anat Rec, 294:391-398, 2011.

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DEVELOPMENT, SEXUAL DIMORPHISM, and INDIVIDUAL VARIATION IN THE SKELETON OF THE FINLESS PORPOISE, NEOPHOCAENA PHOCAENOIDES, IN THE COASTAL WATERS OF WESTERN KYUSHU, JAPAN

Cited by 28 publications

References 10 publications

Cranial Features of the Spotted Seal, Phoca largha, in the Nemuro Strait, Considering Age Effects.

Cranial Features of the Spotted Seal, Phoca largha, in the Nemuro Strait, Considering Age Effects.

Age-Related Change and Allometry of Skull and Canine of Sea Otters, <i>Enhydra lutris</i>

Occipital Ossification of Balaenopteroid Mysticetes

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