Arm joint articulations in the ophiuran brittlestars (Echinodermata: Ophiuroidea): a morphometric analysis of ontogenetic, serial, and interspecific variation

The ophiuroid arm contains a series of vertebral ossicles that form an articulated internal skeleton. Ontogenetic, serial, and interspecific variation in these skeletal elements are investigated using morphometric data from 35 species of brittle-stars (Order Ophiurae). Multiple ossicles were sampled from each individual and several individuals were sampled from each species to reconstruct serial and ontogenetic changes in vertebral morphology. Within species, ontogenetic and serial allometries are not statistically different. These data support 'Jackson's law of localized stages' (Jackson, 1899; Clark, 1914), which proposes that serial variation along the arm reflects ontogenetic stages of ossicle growth.
A multivariate analysis of interspecific variation shows two major vertebral forms: ossicles with a proximal depression and distal keel, and ossicles lacking these features. Variation within these groups is largely continuous, but individual species show distinct shape differences and unique allometric patterns of serial variation. These results suggest that vertebral ossicle variation among species can be described by: 1) variation in initial shape; and 2) variation in the allometric trajectory along the proximal-distal axis.
In all species, the most proximal ossicles within the disk show a non-keeled morphology. In species with keeled arm ossicles, however, there is an abrupt transition within the disk between non-keeled and keeled vertebral forms. A single ossicle, having features of both vertebral types, occurs at this site. The taxonomic distribution of the two vertebral forms and the anatomical transition between forms is discussed with reference to current classification systems and recent phylogenetic schemes for the Ophiuroidea.     

Incudomalleal joint formation: the roles of apoptosis,migration and downregulation

Background  

The middle ear of mammals is composed of three endochondrial ossicles, the stapes, incus and malleus. Joints link the malleus to the incus and the incus to the stapes. In the mouse the first arch derived malleus and incus are formed from a single Sox9 and Type II collagen expressing condensation that later subdivides to give rise to two separate ossicles. In contrast the stapes forms from a separate condensation derived from the second branchial arch. Fusion of the malleus and incus is observed in a number of human syndromes and results in conductive hearing loss. Understanding how this joint forms during normal development is thus an important step in furthering our understanding of such defects.     

Hoc alterum auditus organi ossiculum est: Ear Ossicles in Physical Anthropology

In spite of the importance of auditory ossicles in anthropological studies, very little attention has been paid to these bones, which are only rarely recovered in archaeological excavations and in osteological collections. In this paper, we attempt to review some studies that started in the 1960 from when we first collected and prepared ossicles from the early Egyptian osteological collection of Giovanni Marro in Turin (Italy). We attempt to delineate the potential of ear bones in the study of man. In a few cases, archaeological ossicles were discussed in connection with some forms of pathology. Other studies examined the phylogeny of primates based on auditory ossicles. The function of the ossicles is to transmit sound waves to the cochlear endolymph. The energy transmitted through the ossicles is conserved by the action of two levers, which convert the relatively wide and low-energy movements of the hammer into smaller high-energy movements of the stirrup. It is a matter of argument whether the different proportions of the ossicles may imply variations in auditory perception in primates, including man. While the hammer of modern humans and that of the great apes show similar absolute sizes, nevertheless, the ape manubrium is appreciably greater than that of man. This difference, combined with stirrup proportions, causes a strong “low-gear” effect in apes and, as a consequence, probably a different auditory acuity. Although only a few fossil Neanderthal auditory ossicles are known, it may be, nevertheless, of interest studying the ossicles from the viewpoint of vibration transfer impedance function. The methodology may also be appropriate to study the few Australopithecine ossicles that are known. It is a matter of question whether the ossicles may have a meaning in distinguishing human populations; nevertheless, at least a case of clear distinction between human population has been achieved as in the case of Antinoe Roman–Egyptians.     

Skeletal morphology of the mud star,Ctenodiscus crispatus (Echinodermata: Asteroidea)

The morphology of the following eight major ossicle types is described and illustrated for the goniopectinid asteroid Ctenodiscus crispatus: terminal plates, superomarginal and inferomarginal ossicles, adambulacral and ambulacral ossicles, odontophores, oral intermediate plates, and superambulacral ossicles. Development, variation, and relationships with soft body-parts and with other ossicles are embphasized. Each ossicle type is distinguished by numerous structures related to its function and to articulation with adjoining skeletal elements. Because major structures (such as pustules, alveoli, and articulation surfaces) distinguishing ossicle types develop early during ontogeny, immature ossicles are readily identifiable. However, changes in form and orientation of these structures occur during ossicle growth. Ontogenetic changes are influenced by development of associated skeletal and soft parts. Ambulacral and adambulacral ossicles near the peristome are highly modified but retain the basic characteristics of structure and orientation which define these major types of skeletal elements.     

The foregut-ossicle system of Dromia wilsoni, Dromia personata and Lauridromia intermedia (Decapoda, Brachyura, Dromiidae), studied with a new staining method

The ossicles of the cardiac and pyloric foregut of three species of decapods: Dromia wilsoni [Fulton and Grant, 1902], Dromia personata [Linnè, 1758] and Lauridromia intermedia [Lauri, 1906] are described and illustrated in detail. Five new ossicles are recognized based on a specific staining-method with Alizarin-Red. The ossicle terminology of the brachyuran foregut is revised now to include 37 ossicles. All described ossicles are documented by drawings and photographs. The two new cardiac ossicles, the prepterocardiac and the postpterocardiac ossicles are narrow ossicles associated with the pterocardiac ossicles at the antero-dorsal margin of the cardiac foregut. The pyloric foregut includes the newly described lateral mesopyloric- and the posterior uropyloric ossicles. These pyloric ossicles are clearly recognizable only in the stained condition. Based on our data we provide new additional evidence for brachyuran monophyly and the paraphyletic status of the podotrematan crabs.     

Developmental and morphological variation in the teleost craniofacial skeleton reveals an unusual mode of ossification

We investigated the morphology and development of the scleral ossicles within the eyes of three species from three basal teleost orders, namely, the alewife (Alosa pseudoharengus; Clupeiformes), the surface morph of the Mexican tetra (Astyanax mexicanus; Characiformes) and zebrafish (Danio rerio; Cypriniformes). Two morphologies, circular and elongated, and one variation, fused elements, were identified. Zebrafish have small circular ossicles, whereas the alewife and the Mexican tetra have elongated ossicles. Surprisingly in the Mexican tetra these elements fuse at one end forming a continuous element with an antero-ventral opening; this may be typical for the Order Characiformes. Regardless of morphology, the ossicles develop via unilateral perichondral ossification of the scleral cartilage from two centers opposite one another in the eye. This unilateral type of ossification, in which only the perichondrium furthest from the retina contributes to the ossicles, has not previously been reported in any vertebrate. Because either the perichondrium and/or an extension of the perichondrium can transform into the scleral ossicle, we refer to the transitional tissue as periskeletal. Although the functional significance of the different shaped ossicles is unclear, skeletal muscle attaches directly to these bones, implying voluntary control. The morphological and developmental variation of teleost scleral ossicles makes them an ideal system for determining the genetic basis underlying phenotypic variation as well as for studying mechanisms underlying osteogenic and chondrogenic processes in teleosts. These data support our previous finding that scleral ossicles in teleosts may not be homologous to those in other vertebrates, such as reptiles.     

Test of the relationship between sutural ossicles and cultural cranial deformation: Results from Hawikuh,New Mexico

A number of researchers have hypothesized that the biomechanical forces associated with cultural cranial deformation can influence the formation of sutural ossicles. However, it is still difficult to make definitive conclusions about this relationship because the effects appear to be quite weak, and contradictory results have been obtained when specific sutures and deformation types are compared across studies. This research retests the hypothesis using a single archeological sample of lamdoidally deformed, occipitally deformed, and undeformed crania from Hawikuh, New Mexico (AD 1300–1680). Our results show no significant difference in either the prevalence or number of ossicles between deformed and undeformed crania, suggesting that the abnormal strains generated by cranial shape modification during infancy are not a factor in ossicle development for this population. One significant relationship was detected at the right lambdoid suture in crania with asymmetrical occipital deformation. Crania that were more deformed on the left side showed greater numbers of ossicles on the right side, but the effect was small. Furthermore, the relationship may well reflect a sampling error, due to the small number of crania with greater left side deformation and scorable right side lambdoid ossicles (n = 11). Although it is possible that forms of cranial deformation other than the posterior tabular types examined here may affect ossicle expression, our review of the literature suggests that the relationship in humans is complex and incompletely understood at this time. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Intramembranous ossification of scleral ossicles in Chelydra serpentina

Scleral ossicles are present in many reptiles, including turtles and birds. In both groups the sclerotic ring situated in the eye is composed of a number of imbricating scleral ossicles or plates. Despite this gross morphological similarity, Andrews (1996. An endochondral rather than a dermal origin for scleral ossicles in Cryptodiran turtles. J. Herpetol. 30, 257-260) reported that the scleral ossicles of turtles develop endochondrally unlike those in birds, which develop intramembranously after a complex epithelial-mesenchymal inductive event. This study re-explores one of the species examined by Andrews in order to determine the mode of ossification of scleral ossicles in turtles. A growth series of Chelydra serpentina embryos, including the stages examined by Andrews, were examined by staining separately for cartilage and bone. Results clearly contradict Andrews (1996) and show that the scleral ossicles of Chelydra serpentina develop similarly to those in birds. That is, they develop intramembranously without a cartilage precursor and are likely induced by transient scleral papillae. The sequence of scleral papillae development is broadly similar, but the papillae themselves are not as distinct as those seen in chicken embryos. This study has important consequences for understanding the homology of scleral ossicles among tetrapods.     

The crustacean cuticle does not record chronological age: New evidence from the gastric mill ossicles

A proposed method to determine chronological age of crustaceans uses putative annual bands in the gastric mill ossicles of the foregut. The interpretation of cuticle bands as growth rings is based on the idea that ossicles are retained through the moult and could accumulate a continuous record of age. However, recent studies presented conflicting findings on the dynamics of gastric mill ossicles during ecdysis. We herein study cuticle bands in ossicles in four species of commercially important decapod crustaceans (Homarus gammarus, Nephrops norvegicus, Cancer pagurus and Necora puber) in different phases of the moult cycle using dissections, light microscopy, micro-computed tomography and cryo-scanning electron microscopy. Our results demonstrate that the gastric mill is moulted and ossicles are not retained but replaced during ecdysis. It is therefore not plausible to conclude that ossicles register a lifetime growth record as annual bands and thereby provide age information. Other mechanisms for the formation of cuticle bands and their correlation to size-based age estimates need to be considered and the effect of moulting on other cuticle structures where ‘annual growth bands’ have been reported should be investigated urgently. Based on our results, there is no evidence for a causative link between cuticle bands and chronological age, meaning it is unreliable for determining crustacean age.     

Digestive anatomy of Halella azteca (Crustacea,Amphipoda)

The digestive tract of the freshwater amphipod Hyalella azteca is a straight but differentiated tube consisting of foregut, midgut, and hindgut divisions. The foregut is subdivided into a tubular esophagus, a cardiac stomach, and a pyloric stomach. The cuticular lining of the cardiac stomach is elaborated into a set of food-crushing plates and ossicles, the gastric mill, while the pyloric cuticle forms a complex straining and pressing mechanism. Nine caeca arise from the midgut, seven anteriorly and two posteriorly. Four of the anterior caeca, the hepatopancreatic caeca, are believed to be the primary sites of digestion and absorption. The remaining caeca may be absorptive, secretory, or both. The much-folded hindgut wall is capable of great distention by extrinsic muscle action for water intake to aid in flushing fecal material out of the anus; such action also may stimulate antiperistalsis by intrinsic rectal muscles.     

Technical note: a landmark-based approach to the study of the ear ossicles using ultra-high-resolution X-ray computed tomography data

Previous study of the ear ossicles in Primates has demonstrated that they vary on both functional and phylogenetic bases. Such studies have generally employed two-dimensional linear measurements rather than three-dimensional data. The availability of Ultra- high-resolution X-ray computed tomography (UhrCT) has made it possible to accurately image the ossicles so that broadly accepted methodologies for acquiring and studying morphometric data can be applied. Using UhrCT data also allows for the ossicular chain to be studied in anatomical position, so that it is possible to consider the spatial and size relationships of all three bones. One issue impeding the morphometric study of the ear ossicles is a lack of broadly recognized landmarks. Distinguishing landmarks on the ossicles is difficult in part because there are only two areas of articulation in the ossicular chain, one of which (the malleus/incus articulation) has a complex three-dimensional form. A measurement error study is presented demonstrating that a suite of 16 landmarks can be precisely located on reconstructions of the ossicles from UhrCT data. Estimates of measurement error showed that most landmarks were highly replicable, with an average CV for associated interlandmark distances of less than 3%. The positions of these landmarks are chosen to reflect not only the overall shape of the bones in the chain and their relative positions, but also functional parameters. This study should provide a basis for further examination of the smallest bones in the body in three dimensions.     

Structure,molting, and mineralization of the dorsal ossicle complex in the gastric mill of the blue crab,Callinectes sapidus

This study examined the mesocardiac and urocardiac ossicles in the gastric mill of the blue crab to describe its structure, mineralization, and dynamics throughout the molt cycle, and to assess its possible utility in age determination. Morphologically, the mineralized ossicles are similar to the calcified dorsal carapace having a lamellate structure comprised of sheets of chitin/protein fibrils. Staining with acridine orange showed the same arrangement of an epicuticle, exocuticle, and endocuticle. In much of the mesocardiac and urocardiac ossicles, the endocuticle is very reduced, with the exocuticle predominating; the reverse of the dimensions of the exoskeleton. The lamellate structure of the ossicles was confirmed with scanning electron microscopy; however, elemental mapping by energy‐dispersive analysis of X‐rays revealed that the ossicles are mineralized with calcium phosphate, in contrast to the calcium carbonate biomineral of the exoskeleton. The medial tooth of the urocardiac ossicle is not calcified, but the epicuticle is highly elaborated and impregnated with silica. Histological examination of the ossicles demonstrated that they are molted during ecdysis, so despite the appearance of bands in the mesocardiac ossicle, it is difficult to hypothesize how the bands could represent a record of chronological age. J. Morphol. 276:1358–1367, 2015. © 2015 Wiley Periodicals, Inc.     

Effects of high hydrostatic pressure on bacterial growth on human ossicles explanted from cholesteatoma patients

Background

High hydrostatic pressure (HHP) treatment can eliminate cholesteatoma cells from explanted human ossicles prior to re-insertion. We analyzed the effects of HHP treatment on the microbial flora on ossicles and on the planktonic and biofilm states of selected isolates.

Methodology

Twenty-six ossicles were explanted from cholesteatoma patients. Five ossicles were directly analyzed for microbial growth without further treatment. Fifteen ossicles were cut into two pieces. One piece was exposed to HHP of 350 MPa for 10 minutes. Both the treated and untreated (control) pieces were then assessed semi-quantitatively. Three ossicles were cut into two pieces and exposed to identical pressure conditions with or without the addition of one of two different combinations of antibiotics to the medium.Differential effects of 10-minute in vitro exposure of planktonic and biofilm bacteria to pressures of 100 MPa, 250 MPa, 400 MPa and 540 MPa in isotonic and hypotonic media were analyzed using two patient isolates of Staphylococcus epidermidis and Neisseria subflava. Bacterial cell inactivation and biofilm destruction were assessed by colony counting and electron microscopy.

Principal Findings

A variety of microorganisms were isolated from the ossicles. Irrespective of the medium, HHP treatment at 350 MPa for 10 minutes led to satisfying but incomplete inactivation especially of Gram-negative bacteria. The addition of antibiotics increased the efficacy of elimination. A comparison of HHP treatment of planktonic and biofilm cells showed that the effects of HPP were reduced by about one decadic logarithmic unit when HPP was applied to biofilms.High hydrostatic pressure conditions that are suitable to inactivate cholesteatoma cells fail to completely sterilize ossicles even if antibiotics are added. As a result of the reduced microbial load and the viability loss of surviving bacteria, however, there is a lower risk of re-infection after re-insertion.     

Pale biological implications of some Upper Ordovician juvenile asteroids (Echinodermata)

Blake, D. B. 1990 10 15: Pale biological implications of some Upper Ordovician juvenile asteroids (Echinodermata). Lethaia , Vol. 23, pp. 347–357. Oslo. ISSN 0024–1164.
Two patterns have been recognized in the early dorsal skeletal development of modern asteroids. The skeleton of well-preserved juveniles of the Late Ordovician species Promopalaeaster finei is similar in fundamental ossiclar arrangement to one of these patterns, suggesting continuity of developmental sequence. Similarities include presence of large terminal ossicles and double rows of marginal ossicles. Ancient and modern juveniles differ in that in P. finei , podial pores leading to the interior of the arms are lacking, thus providing an ontogenetic argument that such pores are phylogenetically derived within the class. An unpaired interbrachial marginal, or axillary, is present distal to the oral frame; positioning supports earlier suggestions that the axillary is the homologue of the odontophore ossicle of modern asteroids. Comparisons between P. finei and another Ordovician species, Macroporaster matutinus , suggest the need for greater mouth frame flexibility contributed to the evolution of the modern odontophore. Axillary development is linked to the common absence of actinal ossicles from Paleozoic species. ▭ Asteroidea, Echinodermata, functional morphology, ontogeny, phylogeny, Ordovician, Paleozoic .     

Complex Evolutionary and Genetic Patterns Characterize the Loss of Scleral Ossification in the Blind Cavefish Astyanax mexicanus

The sclera is the tough outer covering of the eye that provides structural support and helps maintain intraocular pressure. In some fishes, reptiles, and birds, the sclera is reinforced with an additional ring of hyaline cartilage or bone that forms from scleral ossicles. Currently, the evolutionary and genetic basis of scleral ossification is poorly understood, especially in teleost fishes. We assessed scleral ossification among several groups of the Mexican tetra (Astyanax mexicanus), which exhibit both an eyed and eyeless morph. Although eyed Astyanax surface fish have bony sclera similar to other teleosts, the ossicles of blind Astyanax cavefish generally do not form. We first sampled cavefish from multiple independent populations and used ancestral character state reconstructions to determine how many times scleral ossification has been lost. We then confirmed these results by assessing complementation of scleral ossification among the F₁ hybrid progeny of two cavefish populations. Finally, we quantified the number of scleral ossicles present among the F₂ hybrid progeny of a cross between surface fish and cavefish, and used this information to identify quantitative trait loci (QTL) responsible for this trait. Our results indicate that the loss of scleral ossification is common–but not ubiquitous–among Astyanax cavefish, and that this trait has been convergently lost at least three times. The presence of wild-type, ossified sclera among the F₁ hybrid progeny of a cross between different cavefish populations confirms the convergent evolution of this trait. However, a strongly skewed distribution of scleral ossicles found among surface fish x cavefish F₂ hybrids suggests that scleral ossification is a threshold trait with a complex genetic basis. Quantitative genetic mapping identified a single QTL for scleral ossification on Astyanax linkage group 1. We estimate that the threshold for this trait is likely determined by at least three genetic factors which may control the severity and onset of lens degeneration in cavefishes. We conclude that complex evolutionary and genetic patterns underlie the loss of scleral ossification in Astyanax cavefish.     

Evidence of predation on Cretaceous sea stars from north-west Germany

Asteroids and asteroid ossicles of the Late Cretaceous White Chalk of north-west Germany were examined for evidence of predation. Bite marks of fishes were commonly found on larger ossicles and on one entirely preserved specimen of Recurvaster polyplacus. On ossicles of Pycinaster magnificus, tooth marks show evidence of serration, probably by the galeoid shark Squalicorax. Predation of durophagous fishes is obviously size-related, because regurgitated pellets contain exclusively ossicles of small asteroids.     

The fine structure and development of calcified skeletal elements in the body wall of holothurian echinoderms

The calcareous ossicles and iron-rich calcified granules in the integument of sea cucumbers (Echinodermata: Holothuroida) have been examined by light and electron microscopy. Most ossicles are perforated, platelike structures that measure 100–500 μm long and consist of magnesium-rich calcite. The formation of ossicles occurs within multinucleated syncytia of sclerocytes that are situated in the dermal layer of the body wall. Sclerocytes possess fairly large numbers of mitochondria and are characteristically enveloped by an external lamina. Each ossicle arises as a minute rodlike spicule that branches and develops into a fenestrated skeletal element. When viewed by SEM, fully developed ossicles appear non-crystalline. Following decoration with synthetically grown calcite seeds, however, each ossicle reveals an ordered array of crystallites that seem to be aligned perpendicular to the ossicle's original plane of growth. Examinations of sectioned ossicles indicate that the mineral phase in each skeletal element lacks a well developed matrix of EDTA-insoluble organic substances. Ossicles first arise in the ciliated, lecithotrophic larvae of Eupentacta quinquesimita at about 1 week postfertilization. Two-week-old specimens adopt an epibenthic existence and subsequently become enveloped by imbricated ossicles that are secreted by sclerocytes resembling those found in adults. In molpadiid holothurians, the adult body wall contains numerous reddish-brown granules that are chiefly composed of iron-rich subunits. The dermal granules differ from calcitic ossicles in developing extracellularly in association with finely filamentous material.     

Ontogenetic and phylogenetic transformations of the ear ossicles in marsupial mammals

This study is based on the examination of histological sections of specimens of different ages and of adult ossicles from macerated skulls representing a wide range of taxa and aims at addressing several issues concerning the evolution of the ear ossicles in marsupials. Three-dimensional reconstructions of the ear ossicles based on histological series were done for one or more stages of Monodelphis domestica, Caluromys philander, Sminthopsis virginiae, Trichosurus vulpecula, and Macropus rufogriseus. Several common trends were found. Portions of the ossicles that are phylogenetically older develop earlier than portions representing more recent evolutionary inventions (manubrium of the malleus, crus longum of the incus). The onset of endochondral ossification in the taxa in which this was examined followed the sequence; first malleus, then incus, and finally stapes. In M. domestica and C. philander at birth the yet precartilaginous ossicles form a supportive strut between the lower jaw and the braincase. The cartilage of Paauw develops relatively late in comparison with the ear ossicles and in close association to the tendon of the stapedial muscle. A feeble artery traverses the stapedial foramen of the stapes in the youngest stages of M. domestica, C. philander, and Sminthopsis virginiae examined. Presence of a large stapedial foramen is reconstructed in the groundplan of the Didelphidae and of Marsupialia. The stapedial foramen is absent in all adult caenolestids, dasyurids, Myrmecobius, Notoryctes, peramelids, vombatids, and phascolarctids. Pouch young of Perameles sp. and Dasyurus viverrinus show a bicrurate stapes with a sizeable stapedial foramen. Some didelphids examined to date show a double insertion of the Tensor tympani muscle. Some differences exist between M. domestica and C. philander in adult ossicle form, including the relative length of the incudal crus breve and of the stapes. Several differences exist between the malleus of didelphids and that of some phalangeriforms, the latter showing a short neck, absence of the lamina, and a ventrally directed manubrium. Hearing starts in M. domestica at an age in which the external auditory meatus has not yet fully developed, the ossicles are not fully ossified, and the middle ear space is partially filled with loose mesenchyme. The ontogenetic changes in hearing abilities in M. domestica between postnatal days 30 and 40 may be at least partially related to changes in middle ear structures.     

Direct Age Determination of a Subtropical Freshwater Crayfish (Redclaw,Cherax quadricarinatus) Using Ossicular Growth Marks

Recent studies have reported that crustacean age determination is possible. We applied a direct ageing method (i.e. transverse cross sectioning of gastric ossicles) to a subtropical freshwater crayfish (Cherax quadricarinatus) sourced from an aquaculture population. Growth mark periodicity and the potential for chronological depositions were investigated by staining C. quadricarinatus with calcein and examining their ossicles a year later. Pterocardiac ossicles were superior to other ageing structures (i.e. other ossicles and eyestalks) and produced repeatable between-reader counts (87% were corroborated and 13% varied by ±1). C. quadricarinatus size-at-age data (for an aquaculture population) was described by a von Bertalanffy growth equation (L _∞ = 32 mm occipital carapace length; K = 0.64; t ₀ = –0.18; R² = 0.81). Ossicular growth marks did not correspond to moult history. The calcein stain was retained over an annual cycle comprising multiple moults, demonstrating that pterocardiac ossicles retain chronological information. The maximum age (3+) corroborated other indirectly-obtained longevity estimates for C. quadricarinatus. Multiple lines of evidence indicate that the growth marks in C. quadricarinatus ossicles are probably deposited annually during winter. The ability to extract age information from subtropical decapods provides substantial opportunities for advancing fisheries and conservation research globally, but further research is needed to provide a definitive validation and elucidate the mechanism governing the accrual of ossicular growth marks.