The comparative morphology of pit organs in elasmobranchs

Peach, Meredith B.; Marshall, N. Justin

doi:10.1002/jmor.10715

Cited by 22 publications

(17 citation statements)

References 41 publications

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“…A direct relationship between the cutaneous sensory system of modern elasmobranchs and surrounding dermal denticles was described by several authors (e.g. Budker 1938;Reif 1985;Peach and Marshall 2009). This concerns the superficial neuromasts (pit organs), which are (together with the canal neuromasts) one of the two main types of mechanoreceptor organs of the lateral line system (McKenzie et al 2014;Webb 2014).…”

Section: Discussionmentioning

confidence: 99%

Denticle-embedded ampullary organs in a Cretaceous shark provide unique insight into the evolution of elasmobranch electroreceptors

Vullo

Guinot

2015

Sci Nat

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Here, we report a novel type of dermal denticle (or placoid scale), unknown among both living and fossil chondrichthyan fishes, in a Cretaceous lamniform shark. By their morphology and location, these dermal denticles, grouped into clusters in the cephalic region, appear to have been directly associated with the electrosensory ampullary system. These denticles have a relatively enlarged (∼350 μm in diameter), ornamented crown with a small (∼100 μm) asterisk- or cross-shaped central perforation connected to a multi-alveolate internal cavity. The formation of such a complex structure can be explained by the annular coalescence and fusion, around an ampullary vesicle, of several developmental units still at papillary stage (i.e. before mineralization), leading to a single denticle embedding an alveolar ampulla devoid of canal. This differs from larger typical ampullae of Lorenzini with a well-developed canal opening in a pore of the skin and may represent another adaptive response to low skin resistance. Since it has been recently demonstrated that ampullary organs arise from lateral line placodes in chondrichthyans, this highly specialized type of dermal denticle (most likely non-deciduous) may be derived from the modified placoid scales covering the superficial neuromasts (pit organs) of the mechanosensory lateral line system of many modern sharks.

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Section: Discussionmentioning

confidence: 99%

Denticle-embedded ampullary organs in a Cretaceous shark provide unique insight into the evolution of elasmobranch electroreceptors

Vullo

Guinot

2015

Sci Nat

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“…3C). Even though the feature cannot be specifically identified from superficial examination, some of the pit organ components in rays can be set on small protuberances (Peach & Marshall 2009;Klimley 2013). If the modified denticle supports pit organ components, the surrounding dermal denticles are not arranged in a pattern typically associated with external pit organs.…”

Section: Discussionmentioning

confidence: 99%

“…If the modified denticle supports pit organ components, the surrounding dermal denticles are not arranged in a pattern typically associated with external pit organs. Peach (2003) and Peach & Marshall (2009) described external pit organ denticle patterns on a rostral-caudal axis as opposed to the radiating arrangement found on the Gulf of Mexico Mollisquama; a histological examination is required for assessing the modified denticle's properties (J. Marshall, pers. comm.…”

Section: Discussionmentioning

confidence: 99%

First record of Mollisquama sp. (Chondrichthyes: Squaliformes: Dalatiidae) from the Gulf of Mexico, with a morphological comparison to the holotype description of Mollisquama parini Dolganov

Grace¹,

Doosey²,

Bart³

et al. 2015

Zootaxa

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The description of the pocket shark genus Mollisquama (M. parini Dolganov, 1984) is based on a single known specimen collected from the Nazca Ridge of the southeast Pacific Ocean. A second Mollisquama specimen has been captured in the central Gulf of Mexico establishing a considerable range extension and a parturition locality because the specimen has a healed vitelline scar. Both the holotype of M. parini and the Gulf of Mexico specimen possess the remarkable pocket gland with its large slit-like external opening located just above the pectoral fin. Features found on the Gulf of Mexico specimen that were not noted in the description of M. parini include a series of ventral abdominal photophore agglomerations and a modified dermal denticle surrounded by a radiating arrangement of denticles just posterior to the mouth. Based on a morphometric and meristic comparison of the Gulf of Mexico specimen with information in the description of M. parini, the Gulf of Mexico specimen is identified as Mollisquama sp. due to differences in tooth morphology and vertebral counts. Phylogenetic analysis of NADH2 gene sequences places Mollisquama sister to Dalatias plus Isistius within the family Dalatiidae.

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“…Neuromasts are categorized on the basis of their location and may occur over the surface of the skin or lining canals. Epidermal neuromasts extend their cupulae into the surrounding water and emanate from a pit surrounded by denticles (termed pit organs) [Maruska, 2001;Peach and Marshall, 2009]. Canal neuromasts are enclosed in fluid-filled canals embedded within the skin or cartilage [Jordan, 2008;Jordan et al, 2009].…”

Section: Lateral Linementioning

confidence: 99%

The Neuroecology of Cartilaginous Fishes: Sensory Strategies for Survival

Collin¹

2012

Brain Behav Evol

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As apex predators, chondrichthyans, or cartilaginous fishes, hold an important position within a range of aquatic ecosystems and influence the balance between species’ abundance and biodiversity. Having been in existence for over 400 million years and representing the earliest stages of the evolution of jawed vertebrates, this group also covers a diverse range of eco-morphotypes, occupying both marine and freshwater habitats. The class Chondrichthyes is divided into two subclasses: the Elasmobranchii (sharks, skates, and rays) and the Holocephali (elephant sharks and chimaeras). However, many of their life history traits, such as low fecundity, the production of small numbers of highly precocious young, slow growth rates, and late maturity, make them highly susceptible to human exploitation. To mitigate the negative effects of human impacts, it is important that we understand the sensory strategies that elasmobranchs use for navigating within their environment, forming reproductive aggregations, feeding, and even communicating. One approach to investigate the sensory bases of their behavior is to examine the peripheral sense organs mediating vision, olfaction, gustation, lateral line, electroreception, and audition in a large range of species in order to identify specific adaptations, the range of sensitivity thresholds, and the compromise between sensory spatial resolution and sensitivity. In addition, we can quantitatively assess the convergence of sensory input to the central nervous system and the relative importance of different sensory modalities. Using a comparative approach and often a combination of anatomical, electrophysiological, and molecular techniques, significant variation has been identified in the spatial and chromatic sampling of the photoreceptors in the eye, the surface area and the number of olfactory lamellae within the nasal cavity, the level of gustatory sampling within the oral cavity, the type and innervation of neuromasts of the lateral line system, the distribution of electroreceptive pores over the head, and the morphology of the inner ear. These results are presented in the context of predictions of sensory capabilities for species living in a range of ecological niches, what further research is needed, and how this sensory input may be a predictor of behavior.

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The comparative morphology of pit organs in elasmobranchs

Cited by 22 publications

References 41 publications

Denticle-embedded ampullary organs in a Cretaceous shark provide unique insight into the evolution of elasmobranch electroreceptors

Denticle-embedded ampullary organs in a Cretaceous shark provide unique insight into the evolution of elasmobranch electroreceptors

First record of Mollisquama sp. (Chondrichthyes: Squaliformes: Dalatiidae) from the Gulf of Mexico, with a morphological comparison to the holotype description of Mollisquama parini Dolganov

The Neuroecology of Cartilaginous Fishes: Sensory Strategies for Survival

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