Anatomy of a hemiramphid pharyngeal mill with reference to Arrhamphus sclerolepis krefftii (Steindachner) (Teleostei: Hemiramphidae)

The structure and function of the pharyngeal jaw apparatus (PJA) and postpharyngeal alimentary tract of Arrhamphus sclerolepis krefftii, an herbivorous hemiramphid, were investigated by dissection, light and scanning electron microscopy, and X-ray analysis of live specimens. A simple model of PJA operation is proposed, consisting of an adductive power stroke of the third pharyngobranchial that draws it posteriorly while the fifth ceratobranchial is adducted, and a return stroke in which the third pharyngobranchial bone is drawn anteriorly during abduction of the fifth ceratobranchial. Teeth in the posteromedial region of the PJA are eroded into an occlusion zone where the teeth of the third pharyngobranchial are spatulate incisiform and face posteriorly in opposition to the rostrally oriented spatulate incisiform teeth in the wear zone of the fifth ceratobranchial. The shape of the teeth and their pedestals (bone of attachment) is consistent with the model and with the forces likely to operate on the elements of the PJA during mastication. The role of pharyngeal tooth replacement in maintaining the occlusal surfaces in the PJA during growth is described. The postpharyngeal alimentary tract of A. sclerolepis krefftii comprises a stomachless cylinder that attenuates gradually as it passes straight to the anus, interrupted only by a rectal valve. The ratio of gut length to standard length is about 0.5. Despite superficial similarities to the cichlid PJA (Stiassny and Jensen [1987] Bull Mus Comp Zool 151:269-319), the hemiramphid PJA differs in the fusion of the third pharyngobranchial bones, teeth in the second pharyngobranchials and the fifth ceratobranchial face anteriorly, the presence of a slide-like diarthroses between the heads of the fourth epibranchials and the third pharyngobranchial, the occlusion zone of constantly wearing teeth, and the unusual form of the muscularis craniopharyngobranchialis. The functional relationship between these structures is explained and the consequence for the fish of a complex PJA and a simple gut is discussed.     

Odontode morphology and skin surface features of Andean astroblepid catfishes (Siluriformes,Astroblepidae)

Two types of odontodes, or dermal teeth, occur in the neotropical Andean astroblepid catfishes. Both odontode types conform in structure to dermal teeth of gnathostomes in having dentine surrounding a central pulp cavity covered by a superficial layer of enameloid, but differ from one another in terms of attachment and association with other epidermis features. Type I odontodes in astroblepids, also found in all representatives of the superfamily Loricarioidea, are larger (40-50 microm base diameter), generally conical and sharply pointed, occur on the fin rays, and are associated with dermal bone. Type I odontodes attach to an elevated pediment of dermal bone of the fin lepidotrich, and to dermal bone generally in loricarioids, via a ring of connective tissue. Type II odontodes of astroblepids are smaller (15-20 microm base diameter) and blunt, occur in the skin of the head, maxillary barbels, nasal flap, and lip margins, and are not associated with dermal bone. Observations based on histology and scanning electron microscopy indicate that Type II odontodes are associated with other epithelial structures to form a putative mechanosensory organ. The odontode base lies deep in the dermis. The shaft is surrounded by a dense patch of microvillous epithelium and projects from within a pit formed by an elevated ring of laminar epithelial cells bearing several columnar, knob-like putative mechanosensory structures. Type II odontode organs have thus far been observed in only three astroblepid species, Astroblepus longifilis, A. chotae, A. rosei, where they occur in especially dense arrays on the maxillary barbels, surrounded by discrete patches of microvilli and separate mechanoreceptors. Type II odontode organs are less dense elsewhere on the body, but also occur in the skin of the snout, head, and lips. Typical taste buds are absent from the barbels of these species, but present in other astroblepids. The presence of Type II odontodes and their association with specialized epithelial pit organs are unique to astroblepids among siluriforms and may be potentially important adaptations to life in torrential mountain streams.     

Functional implications of primate enamel thickness.

Recent evolutionary interpretations of Hominoidea have postulated functional relationships between tooth form, diet and masticatory biomechanics. A major consideration is the durability of the tooth under certain dietary conditions. Teeth with low cusps and thicker enamel are able to withstand heavy mastication of abrasive food bolus for a longer period. When comparisons are made between species of higher primates the variables of tooth size, cusp morphology, and enamel thickness appear to be related but until now no systematic analysis has been made to determine the functional relevance of several dental dimensions. This study provides data gained from comparisons of dentition of nine species of primates. Histological sections were made of the post canine teeth and 21 dimensions were compared. The relevant dimensions identified serve to withstand dental wear. The distribution of thicker enamel corresponded to the observed wear planes. Humans had thicker enamel than pongids while the macaque had the thinnest. These preliminary results tend to support theories which explain low, thick, enameled cusps in hominids.     

Changing occlusal variation in Pima Amerinds

Occlusal variables and arch measurements have been recorded on 341 Pima Amerinds pertaining to two samples, one of older individuals raised on traditional diets, the other of younger individuals raised on refined commercial foods that are typical of modern urbanized people. Permanent dental occlusion is significantly more variable from defined ideals in the younger sample, despite their fewer deformities resulting from progressive aging. The youths had relatively narrower palates, correlating with a general trend among industrialized populations and also among experimental animals fed soft diets. Relative rate of deciduous tooth loss and replacement did not correlate with any occlusal variable.     

Interproximal grooving in the Atapuerca-SH hominid dentitions

The dental sample recovered from the Sima de los Huesos (SH) Middle Pleistocene cave site of the Sierra de Atapuerca (Spain) includes 296 specimens. Interproximal wear grooves have been observed in 20 maxillary and mandibular posterior teeth belonging to at least five of the 32 individuals identified so far in the SH hypodigm. Interproximal grooving affected only the adults, and at an age between 25 and 40 years. The appearance, morphology, and location pattern of the SH wear grooves are similar to those reported in other fossil hominids and in more recent human populations. Two alternative proposals, the toothpicking and the fiber or sinew processing hypotheses, compete for explaining the formation of this anomalous wear. The characteristics observed in the wear grooves of the SH teeth are compatible only with the habitual probing of interdental spaces by means of hard and inflexible objects. Dietary grit may also have contributed to the abrasion of the root walls during the motion of the dental probes. Am. J. Phys. Anthropol. 102:369–376, 1997. © 1997 Wiley-Liss, Inc.     

猕猴颊齿大小的性差研究初报

对28例太行山成年猕猴(♂10,♀18)的上、下颌颊齿齿冠面积进行测量。运用SPSS 10.0统计软件的多变量分析,选择有关颊齿变量建立性别判别函数。结果表明:猕猴颊齿具有明显的性差。选择不同的变量和选择不同的判别函数其性别正确判别率不同。上、下颌颊齿的性差有一定差异。使用逐步判别法建立判别函数,其性别正确判别率上颌颊齿为89.3%,下颌颊齿为92.3%。     

Pharyngeal jaw morphology and homology in Sicydiine Gobies (Teleostei: Gobiidae) and allies

An extremely large number of fifth ceratobranchial teeth, with highly modified, striated, and hooked tips were observed in the central and western Pacific sicydiine goby genus Stiphodon.A scanning electron microscopic study of the form and arrangement of fifth ceratobranchial teeth was conducted to assess the distribution of these modifications in sicydiine gobies and their putative close relatives. Our goals were to explore a new set of characters in gobioid systematics, to test sicydiine monophyly, and to test hypotheses of relationships of sicydiine gobies. Sicydiines are hypothesized herein to be most closely related to the western Pacific Tukugobius and Rhinogobius,freshwater genera with which they share thickened pelvic-fin rays, no teeth on the anterior portion of the fifth ceratobranchial bones, fifth ceratobranchial teeth with differentiated and striated tips, and overlapping anterior rami of the fifth ceratobranchial bones. The latter two characters occur in some, but not all, sicydiines. The pantropical freshwater goby Awaous,often classified with sicydiines, is not considered the closest relative of the subfamily. The highly modified fifth ceratobranchials of Stiphodon are similar to, and concluded here to be homoplasious with, those of the mudflat-dwelling New World goby Evorthodus and the Indo-west Pacific oxudercine gobies, represented in this study by Pseudapocryptes. J. Morphol. 237:257–274, 1998. Published 1998 Wiley-Liss, Inc.     

Fluoride or/and aluminum induced toxicity in guinea pig teeth with the low expression of dentine phosphoprotein

This study investigated the damage and expression of dentine phosphoprotein (DPP) in guinea pig teeth by the administration of fluoride (F) or/and aluminum (Al). Fifty‐two guinea pigs were divided randomly into four groups (control, F, Al, and F+Al). F (150 mg NaF/L) or/and Al (300 mg AlCl₃/L) were added in their drinking water for 90 days. The levels of F ion, dentine sialophosphoprotein (DSPP) gene, and DPP protein in incisor and molar were determined, respectively. The results showed that the concentrations of F ion in F and F+Al groups were increased significantly. F induced the mottled enamel and irregular abrasion of teeth, which might occur as a consequence of depressed DSPP mRNA and DPP protein expression. Both the gene and protein expressions showed obvious decrease induced by Al, especially by F. There were no synergistic effects between F and Al, instead, Al inhibited the toxicity of F.     

中华稻蝗全消化道内壁显微结构观察

本文采用扫描仪和扫描电镜对中华稻蝗消化道内壁的细微结构进行了系统观察和研究。结果表明,中华稻蝗食道内壁由纵行脊组成,前端有齿。嗉囊包括两段,前段的一个小的膨大部分,由V-形区和两侧的V-形脊组成,只在前端内壁有齿;后段为一个大的膨大部分,由柳叶脊、扇形脊和不规则脊组成,脊的上缘有齿。前肠内壁的齿主要为单生齿,除贲门瓣上齿的齿尖指向前方外,全部齿的齿尖指向后方。后肠的前端为12个幽门瓣,内壁有齿。回肠和结肠由6条纵行脊组成,结肠内壁有齿。直肠的齿在除直肠垫外的直肠内壁上。后肠的齿主要为丛生齿,后肠除直肠内壁齿的齿尖指向附着环外,全部齿的齿尖指向后方。根据我们的观察,对前肠提出了新的分区。