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1.
The pit organs of elasmobranchs (sharks, skates and rays) are free neuromasts of the mechanosensory lateral line system. Pit organs, however, appear to have some structural differences from the free neuromasts of bony fishes and amphibians. In this study, the morphology of pit organs was investigated by scanning electron microscopy in six shark and three ray species. In each species, pit organs contained typical lateral line hair cells with apical stereovilli of different lengths arranged in an “organ‐pipe” configuration. Supporting cells also bore numerous apical microvilli taller than those observed in other vertebrate lateral line organs. Pit organs were either covered by overlapping denticles, located in open grooves bordered by denticles, or in grooves without associated denticles. The possible functional implications of these morphological features, including modification of water flow and sensory filtering properties, are discussed. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc. 相似文献
2.
M. B. Peach 《Journal of fish biology》2003,62(4):793-802
Epaulette sharks Hemiscyllium ocellatum in three treatments, pit organs (free neuromasts) ablated, sham-operated and normal ( n = 8 for each treatment), showed a significant preference for facing upstream in a flume ( P < 0·05). There were no significant differences in the mean angles or angular variances among treatments. Individuals with ablated pit organs, however, spent significantly less time moving around than controls ( P < 0·05), suggesting that pit organs contributed to motivation for activity. Pit organs do not appear to make an important contribution to rheotaxis in H. ocellatum . It is suggested that this may be due to structural differences in the pit organs of H. ocellatum compared with other species. 相似文献
3.
Pit organs (free neuromasts of the mechanosensory lateral line system) are distributed over the skin of elasmobranchs. To investigate phylogenetic trends in the distribution and abundance of pit organs, 12 relevant morphological characters were added to an existing matrix of morphological data (plus two additional end terminals), which was then re-analysed using cladistic parsimony methods ( paup * 4.0b10). Character transformations were traced onto the most parsimonious phylogenetic trees. The results suggest the following interpretations. First, the distinctive overlapping denticles covering the pit organs in many sharks are a derived feature; plesiomorphic elasmobranchs have pit organs in open slits, with widely spaced accessory denticles. Second, the number of pit organs on the ventral surface of rays has been reduced during evolution, and third, spiracular pit organs have changed position or have been lost on several occasions in elasmobranch evolution. The concentrated-changes test in macclade (version 4.05) was used to investigate the association between a pelagic lifestyle and loss of spiracular pit organs (the only character transformation that occurred more than once within pelagic taxa). Depending on the choice of tree, the association was either nonsignificant at P = 0.06 or significant at P < 0.05. Future studies, using species within more restricted elasmobranch clades, are needed to resolve this issue. 相似文献
4.
The biological function of anatomical specializations in the mechanosensory lateral line of elasmobranch fishes is essentially unknown. The gross and histological features of the lateral line in the Atlantic stingray, Dasyatis sabina, were examined with special reference to its role in the localization and capture of natural invertebrate prey. Superficial neuromasts are arranged in bilateral rows near the dorsal midline from the spiracle to the posterior body disk and in a lateral position along the entire length of the tail. All dorsal lateral line canals are pored, contain sensory neuromasts, and have accessory lateral tubules that most likely function to increase their receptive field. The pored ventral canal system consists of the lateral hyomandibular canal along the disk margin and the short, separate mandibular canal on the lower jaw. The extensive nonpored and relatively compliant ventral infraorbital, supraorbital, and medial hyomandibular canals form a continuous complex on the snout, around the mouth, and along the abdomen. Vesicles of Savi are small mechanosensory subdermal pouches that occur in bilateral rows only along the ventral midline of the rostrum. Superficial neuromasts are best positioned to detect water movements along the transverse body axis such as those produced by tidal currents, conspecifics, or predators. The pored dorsal canal system is positioned to detect water movements created by conspecifics, predators, or possibly distortions in the flow field during swimming. Based upon the stingray lateral line morphology and feeding behavior, we propose the Mechanotactile Hypothesis, which states that the ventral nonpored canals and vesicles of Savi function as specialized tactile mechanoreceptors that facilitate the detection and capture of small benthic invertebrate prey. J. Morphol. 238:1–22, 1998. © 1998 Wiley-Liss, Inc. 相似文献
5.
The maturity and reproduction of the Atlantic angel shark Squatina dumeril were assessed using 77 females (29·2–110·4 cm total length; LT) and 269 males (58·7–108·2 cm LT) harvested by artisanal gillnetters off Venezuela. The biased sex ratio implied segregation or sex‐specific gear selectivity. Based on the development of the reproductive tract, 50% LT at sexual maturity (LT50, mean ± s.e .) for females and males were estimated at 86·14 ± 0·64 and 81·55 ± 0·12 cm, respectively. Uterine fecundity ranged between one and six and with a maximum embryo size of 25·7 cm LT. Gravid females were observed from August to December, including those close to parturition and while the gestation period was not confirmed, the size of ovarian follicles among some specimens implied protraction. The low fecundity of the species supports close monitoring of catches. 相似文献
6.
Trokovic N Herczeg G McCairns RJ Ab Ghani NI Merilä J 《Journal of evolutionary biology》2011,24(7):1546-1558
The mechanosensory lateral line system of fishes is an important organ system conveying information crucial to individual fitness. Yet, our knowledge of lateral line diversity is almost exclusively based on interspecific studies, whereas intraspecific variability and possible population divergence have remained largely unexplored. We investigated lateral line system variability in four marine and five pond populations of nine-spined stickleback (Pungitius pungitius). We found significant differences in neuromast number between pond and marine fish. In particular, three of seventeen lateral line regions (viz. caudal peduncle superficial neuromasts; canal neuromasts from the anterior trunk and caudal peduncle) showed strong divergence between habitats. Similar results were obtained with laboratory-reared individuals from a subset of populations, suggesting that the patterns found in nature likely have a genetic basis. Interestingly, we also found habitat-dependent population divergence in neuromast variability, with pond populations showing greater heterogeneity than marine populations, although only in wild-caught fish. A comparison of neutral genetic (F(ST)) and phenotypic (P(ST)) differentiation suggested that natural selection is likely associated with habitat-dependent divergence in neuromast counts. Hence, the results align with the conclusion that the mechanosensory lateral line system divergence among marine and pond nine-spined sticklebacks is adaptive. 相似文献
7.
Detailed swimming kinematics of the yellowtail kingfish Seriola lalandi were investigated after unilateral ablation of superficial neuromasts (SNs). Most kinematic variables, such as tail‐beat frequency, stride length, caudal fin‐beat amplitude and propulsive wavelength, were unaffected but lateral amplitude at the tip of the snout (A0) was significantly increased in SN‐disrupted fish compared with sham‐operated controls. In addition, the orientation of caudal fin‐tip relative to the overall swimming direction of SN‐disrupted fish was significantly deflected (two‐fold) in comparison with sham‐operated control fish. In some fish, SN disruption also led to a phase distortion of the propulsive body‐wave. These changes would be expected to increase both hydrodynamic drag and thrust production which is consistent with the finding that SN‐disrupted fish had to generate significantly greater thrust power when swimming at ≥1·3 fork lengths (LF) s?1. In particular, hydrodynamic drag would increase as a result of any increase in rotational (yaw) perturbation and sideways slip resulting from the sensory disturbance. In conclusion, unilateral SN ablation produced directional instability of steady swimming and altered propulsive movements, suggesting a role for sensory feedback in correcting yaw and slip disturbances to maintain efficient locomotion. 相似文献
8.
J. P. Diaz M. Prié-Granié M. Kentouri † S. Varsamos R. Connes 《Journal of fish biology》2003,62(1):24-40
Using light and electron microscopy, a study of the development of the lateral line system of the sea bass Dicentrarchus labrax , from embryo to adult, revealed that the first free neuromasts appeared on the head shortly before hatching and multiplied during the larval stage. They were aligned on the head and trunk in a pattern which corresponded to the location of future canals. The transition to the juvenile stage marked the start of important anatomical changes during which head and trunk canals were formed successively. Neuromasts, with a cupula and consisting of standard sensory cells and supporting cells, were characterized by bidirectional polarity. The exact location of the first neuromast formed in the embryo was identified and its differentiation monitored from primordium to eruption. This neuromast was distinguishable from the others by its radial polarity. Correlations were made between the development of the lateral line system and the behaviour of the sea bass. 相似文献
9.
M. B. Peach 《Journal of fish biology》2001,59(3):696-704
Resting Port Jackson sharks Heterodontus portusjacksoni with dorso-lateral pit organs ablated oriented with a mean angle of 263° to the current direction in a flume. This was significantly different ( P <0·01) to controls (normal and sham operated) who had a pooled mean angle of 44° to the current. Thus the dorso-lateral pit organs of H. portusjacksoni , like the free neuromasts of some teleosts, provide sensory information for rheotaxis. 相似文献
10.
11.
Neonatal predation in multispecies aquarium exhibits can prevent detection of captive breeding by wobbegong sharks. We used ultrasonography and isolation strategies to prevent neonatal predation and maximize survival/growth of the dwarf ornate wobbegong (Orectolobus ornatus de Vis, 1883). We captured seven free‐living wobbegongs (two males and five females) and subjected each animal to a health assessment which led to the euthanasia of one female with a retained hook. Ultrasonography showed that females were pregnant, one was preovulatory, and one was in a resting phase. Two females (one pregnant) and one male were placed in isolation in each of two tanks. In October 2006, 25 neonates were born overnight with the two litters placed into separate neonate tanks. Over the ～6.5‐month monitoring period, four neonates with reduced body condition died without premonitory signs resulting in a 63.0% annual survival rate. Finite growth rates did not differ between sexes or litters and averaged (±SE) 12.2 (1.5) cm/year and 156.4 (26.4) g/year. At the cessation of monitoring, total length had increased by ～30%, whereas total weight had almost doubled with neonatal body condition in line with free‐living wobbegongs. Our efficacious, six‐step manipulative, the approach should be applicable with all wobbegongs given their reproductive similarities, but we recommend that efforts focus on the dwarf ornate, tasselled and Japanese wobbegongs because all are small in size and have bred in aquaria. Ultimately, this approach should produce self‐sustaining aquarium populations, place less reliance on the wild acquisition and provide animals for other aquaria, population restocking, or scientific research. 相似文献
12.
Shark populations tend to be highly vulnerable to overexploitation due to low fecundity and slow growth rates. Recent fishing pressure on the smooth dogfish in the northwest Atlantic has created a necessity for more information about their basic biology. Length and age at maturity, fecundity, and reproductive season were estimated. Total length at 50% maturity was 102cm for females, and 86cm for males. The majority of females were mature at age 4 or 5, and all males were mature at 2 or 3 years of age. Females had an 11–12 month gestation with parturition occurring in May, ovulation occurring between May and July likely in late May and early June, and mating occurring between May and September. Fecundity ranged between 3 and 18 pups per litter, and was positively related to length and age, with a mean of 9.53 pups per litter. Sperm was found in the terminal zone of the oviducal gland of females throughout the year. 相似文献
13.
Jacqueline F. Webb Nathan C. Bird Lauren Carter Juleen Dickson 《Journal of morphology》2014,275(6):678-692
14.
J. A. Sulikowski † W. B. Driggers III‡ T. S. Ford R. K. Boonstra J. K. Carlson § 《Journal of fish biology》2007,70(2):428-440
The reproductive periodicity of blacknose sharks Carcharhinus acronotus in the northern Gulf of Mexico was determined by examining reproductive tissues from specimens collected monthly from 2002 to 2005. Monthly changes in shell gland mass, right ovary mass and ovarian follicle diameter were assessed for 74 mature females. Temporal changes in testes mass, testes width and proportion of mature spermatocysts were examined for 64 mature males. Trends in female reproductive tissues suggested an annual peak in reproductive activity during June and July, while trends in male variables suggested an annual reproductive peak during May and June. Although male and female reproductive activity peaked in different months, a strong synchronicity existed between the proportion of mature spermatocysts and the diameter of the largest ovarian follicle. Based on these results, the mating season of blacknose sharks lasts from mid-May to July in the Gulf of Mexico. Maximum embryo sizes were observed in May, which suggested that partition occurs during late May or early June. Results indicate that blacknose sharks have a clearly defined annual cycle in the Gulf of Mexico. This conclusion is further supported by the complete absence of gravid females without vitellogenic ovarian follicles among all mature females examined. 相似文献
15.
Parthenogenesis has been observed in several elasmobranch species, primarily in public aquaria. The majority of cases of parthenogenesis have occurred either when females were held without males or once a male was removed from a female's habitat. Here we report a second instance of parthenogenesis in a zebra shark female that was housed with conspecific mature males. This study calls into question the conditions under which elasmobranch females undergo parthenogenesis. 相似文献
16.
Examination of the lateral line canals in the Epaulette Shark reveals a much more differentiated sensory system than previously reported from any elasmobranch. Two main types of lateral line canals are found. In one type rounded patches of sensory epithelia are separated by elevations of the canal floor. The other type is a straight canal without restrictions and with an almost continuous sensory epithelium. In addition, we found epithelia (type A) with very long apical microvilli on the supporting cells. These microvilli reach beyond the stereovilli of the hair cells. Another type (B) of sensory epithelium has short microvilli on the supporting cells. In this latter type of epithelium the stereovilli of the hair cells are comparatively tall and reach out beyond the supporting cell microvilli.
New hair cells are found widely in both types of sensory epithelia. These always occur as single cells, unlike those described in teleost lateral line canal sensory epithelia where new hair cells seem to form in pairs. Dying hair cells are also widespread, indicating a continuous turnover of hair cells. 相似文献
New hair cells are found widely in both types of sensory epithelia. These always occur as single cells, unlike those described in teleost lateral line canal sensory epithelia where new hair cells seem to form in pairs. Dying hair cells are also widespread, indicating a continuous turnover of hair cells. 相似文献
17.
版纳鱼螈侧线系统的结构 总被引：5，自引：0，他引：5
版纳鱼螈(Ichthyophis bannanica)是我国无足目的仅有代表,应用光镜和扫描电镜对版纳鱼螈的侧线系统进行形态学和组织学观察的研究表明:版纳鱼螈幼体表皮中的侧线器官有接受机械刺激的神经丘和电接受壶腹器官两种,神经丘包括表面神经丘和陷神经丘。侧线分布主要包括:头部的鼻侧线、眶上线、眶下线、眶后线、口侧线、下颌线、咽侧线、鳃孔上线和身体上的背侧线。侧线器官的分布密度、大小和凹陷深度明显与周围表皮的厚度和不同部位有关。幼体的侧线器官退化与鳃孔的退化同步,亚成体以后不保留侧线系统。版纳鱼螈的侧线分布和器官结构与其它无足类的大致相似,仅在眶上线和眶下线的器官分布上存在微小的差别 相似文献
18.
James C. Liao 《Biology letters》2010,6(3):402-405
The lateral line system of larval zebrafish can translate hydrodynamic signals from the environment to guide body movements. Here, I demonstrate a spatial relationship between the organization of afferent neurons in the lateral line ganglion and the innervation of neuromasts along the body. I developed a whole cell patch clamp recording technique to show that afferents innervate multiple direction-sensitive neuromasts, which are sensitive to low fluid velocities. This work lays the foundation to integrate sensory neuroscience and the hydrodynamics of locomotion in a model genetic system. 相似文献
19.
Michelle R. Davis Natalie Mylniczenko Timothy Storms Frances Raymond J. Lawrence Dunn 《Zoo biology》2006,25(6):491-500
The mediation of nociception with analgesic medications has not been well documented in elasmobranchs. The purpose of this study was to determine effective analgesic doses of the opioid agonist‐antagonist, butorphanol, and the non‐steroidal anti‐inflammatory drug, ketoprofen, in an elasmobranch. This was evaluated by repetitively assessing minimum anesthetic concentrations of the immersion anesthetic, tricaine methanesulfonate (MS‐222), required to prevent response to noxious stimuli in chain dogfish (Scyliorhinus retifer) when administered multiple doses of each of the analgesics (0.25, 0.5, 1.0, 2.5, and 5.0 mg/kg butorphanol and 1.0, 1.5, 2.0, and 4.0 mg/kg ketoprofen). Baseline concentrations of MS‐222 required to prevent a response to a noxious stimulus were determined for each animal and served as the controls. Although individual animals displayed a reduction in MS‐222 concentration with various doses of both analgesics, no statistically significant difference was noted between control animals and animals given analgesics. It is plausible that unique elasmobranch anatomy, lack of appropriate medication dose or timing of administration, and other physiological factors not yet identified may have contributed to the lack of apparent efficacy of the analgesics evaluated in this study. Zoo Biol 0:1–10, 2006. © 2006 Wiley‐Liss, Inc. 相似文献
20.
Meredith B. Peach 《Marine and Freshwater Behaviour and Physiology》2013,45(4):275-279
Little is known about the skin surface of elasmobranchs (sharks and rays), compared to the morphology of the overlying placoid scales. In this article the discovery of cells with numerous apical microvilli on the skin of sharks is reported. As the morphology of these cells is similar to various other sensory receptors, including solitary chemosensory cells in other fishes, it seems likely that they have a sensory function. 相似文献