Skeletal Ontogeny Research Articles

Skeletal ontogeny in basal scleractinian micrabaciid corals

AbstractCover illustration. Skeleton of extant micrabaciid scleractinian coral Letepsammia franki Owens, 1994 (holotype USNM75638, Indian Ocean, Durban, 138 m). In this issue of the Journal of Morphology Janiszewska et al. study the skeletal ontogeny of Micrabaciidae, one of two modern basal scleractinian lineages using serial microcomputed tomography sections and scanning electron micrographs. See pp. 243–257 for a new interpretation of the septal development of this group of screactinian corals.

Skeletal ontogeny in basal scleractinian micrabaciid corals

The skeletal ontogeny of the Micrabaciidae, one of two modern basal scleractinian lineages, is herein reconstructed based on serial micro-computed tomography sections and scanning electron micrographs. Similar to other scleractinians, skeletal growth of micrabaciids starts from the simultaneous formation of six primary septa. New septa of consecutive cycles arise between septa of the preceding cycles from unique wedge-shaped invaginations of the wall. The invagination of wall and formation of septa are accompanied by development of costae alternating in position with septa. During corallite growth, deepening invagination of the wall results in elevation of septa above the level of a horizontal base. The corallite wall is regularly perforated thus invaginated regions consist of pillars inclined downwardly and outwardly from the lower septal margins. Shortly after formation of septa (S2 and higher cycles) their upper margins bend and fuse with the neighboring members of a previous cycle, resulting in a unique septal pattern, formerly misinterpreted as "septal bifurcation." Septa as in other Scleractinia are hexamerally arranged in cycles. However, starting from the quaternaries, septa within single cycles do not appear simultaneously but are inserted in pairs and successively flank the members of a preceding cycle, invariably starting from those in the outermost parts of the septal system. In each pair, the septum adjacent to older septa arises first (e.g., the quinaries between S2 and S4 before quinaries between S3 and S4). Unique features of micrabaciid skeletal ontogeny are congruent with their basal position in scleractinian phylogeny, which was previously supported by microstructural and molecular data.

Skeletal development in the African elephant and ossification timing in placental mammals

We provide here unique data on elephant skeletal ontogeny. We focus on the sequence of cranial and post-cranial ossification events during growth in the African elephant (Loxodonta africana). Previous analyses on ossification sequences in mammals have focused on monotremes, marsupials, boreoeutherian and xenarthran placentals. Here, we add data on ossification sequences in an afrotherian. We use two different methods to quantify sequence heterochrony: the sequence method and event-paring/Parsimov. Compared with other placentals, elephants show late ossifications of the basicranium, manual and pedal phalanges, and early ossifications of the ischium and metacarpals. Moreover, ossification in elephants starts very early and progresses rapidly. Specifically, the elephant exhibits the same percentage of bones showing an ossification centre at the end of the first third of its gestation period as the mouse and hamster have close to birth. Elephants show a number of features of their ossification patterns that differ from those of other placental mammals. The pattern of the initiation of the ossification evident in the African elephant underscores a possible correlation between the timing of ossification onset and gestation time throughout mammals.

Geographic variation of skeletal ontogeny and skull shape in the harbour porpoise (Phocoena phocoena)

All extant porpoise species show paedomorphic skeletal traits. These traits are hypothesized to be connected with rapid growth to reproductive size and could thus show geographic variation according to ecological circumstances. To investigate this, skeletal ontogeny was compared among harbour porpoises from California, West Greenland, the inner Danish waters, and the Sea of Azov. Porpoises from California grew to larger sizes than Danish porpoises, which were again larger than Greenlandic porpoises, whereas Azov porpoises were smallest. Size differences were largely attributable to differences in timing of offset of growth. Expression of paedomorphosis followed the same pattern among populations and sexes as adult sizes; Californian porpoises were less paedomorphic than the other populations across all assessed traits, whereas porpoises from Azov were the most paedomorphic. We propose that the larger size and less profound paedomorphism seen in Californian porpoises are attributable to fluctuation of prey availability, owing to variation in upwelling on which productivity in Californian waters depends. Skull shapes after correction for allometry were significantly different among all populations, Sea of Azov porpoises being most divergent. There was no overlap of skull shapes between the Atlantic, the Pacific, and Azov, supporting the current division of harbor porpoises ( Phocoena phocoena (L., 1758)) into three subspecies ( Phocoena phocoena phocoena (L., 1758), Phocoena phocoena relicta Abel, 1905, and Phocoena phocoena vomerina Gill, 1865).

Fate of Mu Receptors During Rat Skeletogenesis

Studies have intimated a role for endogenous opioids in skeletal ontogeny. We hypothesized that this role may be confined to the perinatal period. We, therefore, examined both fetal and postnatal rat long bones to determine the pattern, if any, of mu receptor expression. Perfused long bones and brains were harvested from 3 to 4 each of near-term fetuses, 3- to 4-week-old neonates, and 6-week-old juveniles. Tissues were decalcified, embedded, sectioned, quenched of peroxidase, and then blocked. Sections were incubated overnight with either rabbit antirat mu receptor IgG or naïve rabbit IgG (control) at 4 degrees C. The next day, sections were washed, blocked again, and incubated with biotin-labeled secondary antibody, streptavidin-peroxidase conjugate, and a chromogen substrate with intervening wash steps. Slides were counterstained with hematoxylin and coverslipped. Digital photomicrographs were then imported into an image analysis program and the percent area of stained cortical and trabecular bone quantified. Mu receptor expression decreased significantly with age. Approximately 25% of the area of fetal long bones stained positively, including the endosteum, periosteum, and the growth plate. Little or no nonspecific staining occurred. Staining in neonatal tissue was diminished to <11% of the area and involved areas of apparent remodeling; chondrocytes in the growth plates failed to stain. Finally, juvenile bone evidenced staining approaching background levels produced by control slides (approximately 2%). Mu receptors are abundant in developing rat long bones during fetal development but become progressively less abundant postnatally. This infers a role for endogenous opioids during skeletal ontogeny.

Appendicular skeleton inBachia bicolor(Squamata: Gymnophthalmidae): osteology, limb reduction and postnatal skeletal ontogeny

Jerez, A. and Tarazona, O. A. 2009. Appendicular skeleton in Bachia bicolor (Squamata: Gymnophthalmidae): osteology, limb reduction and postnatal skeletal ontogeny. — Acta Zoologica (Stockhom) 90: 42‐50 The osteology of the appendicular skeleton and its postnatal development are described in Bachia bicolor , a serpentiform lizard with reduced limbs. The pectoral girdle is well developed and the forelimb consists of a humerus, ulna, radius, five carpal elements (ulnare, radiale, distal carpals 4‐3, centrale), four metacarpals (II, III, IV, V) and phalanges (phalangeal formula X-2-2-2-2). In the hindlimb, the femur is small and slender, and articulates distally with a series of ossified amorphous and extremely reduced elements that correspond to a fibula, tibia and proximal and distal tarsals 4 and 3. The pelvic girdle consists of ischium, pubis and ilium, but its two halves are widely separated; the ilium is the least reduced element. We describe the ossification and development during postnatal skeletal ontogeny, especially of epiphyseal secondary centres, ossifications of carpal elements, apophyseal ossifications and sesamoids. Compared to other squamates, B. bicolor shows an overall reduction in limb size, an absence of skeletal elements, a fusion of carpal elements, an early differentiation of apophyseal centres, and a low number of sesamoids and apophyseal centres. These observations suggest that the reductions are produced by heterochronic changes during postnatal development and probably during embryonic development; therefore the appendicular skeleton exhibits a pattern of paedomorphic features.

Substance P and its receptors in bone metabolism

Accumulating evidence on bone physiopathology has indicated that the skeleton contains numerous nerve fibers and its metabolism is regulated by the nervous system. Until now, more than 10 neuropeptides have been identified in bone. Substance P (SP) is a neuropeptide released from axons of sensory neurons, belongs to the tachykinin family and plays important roles in many physiological and pathological processes by acting as a neurotransmitter, neuromodulator, or trophic factor. It activates signal transduction cascades by acting on the neurokinin-1 receptor (NK(1)-R). Previous studies have confirmed that the SP-immunoreactive (IR) axons innervate bone and adjacent tissues, and that their density varies depending on the regions and physiological or pathological conditions. Over the past few decades, it has been found that SP takes part in the stimulation of bone resorption, and its receptors have been demonstrated to be located in osteoclasts. Notably, in studies of skeletal ontogeny, SP-IR axons have been shown to appear at an early stage, mostly coinciding with the sequence of long bone mineralization. These findings, together with data obtained from chemically or surgically targeted nerve deletions, strongly suggest that SP is a potent regulator of skeletal physiology. The specific distribution of SP-IR nerve fibers, the different amount of SP within regions, and the various levels of expression of NK(1)-R in targeted cells presumably related to and participate in bone metabolism. It can be predicted that the indirect roles of SP through other cytokines are as important as its direct roles in bone metabolism. This new regulating pathway of bone metabolism would have enormous implications in skeletal physiology and the relevant research might present curative potentials to a spectrum of bone diseases.

An aggregation of lizard skeletons from the Lower Cretaceous of China

Many fossil taxa are known only from single specimens, making it difficult to gauge levels of intraspecific, and particularly ontogenetic, variation. Here we report on an aggregation of the Early Cretaceous lizardDalinghosaurus longidigitus from deposits of the Yixian Formation, China. A single block from the Lujiatun Bed contains parts of at least sixteen three-dimensional skeletons ranging from hatchling to young adult. Taphonomic features suggest the animals were probably part of a natural aggregation caught up and transported by a localised mudslide during a volcanic eruption. The most complete specimens on the block add new information on jaw, palate and braincase morphology for this derived lizard.Dalinghosaurus is now represented by a sample of nearly thirty individuals from hatchling to skeletally mature adult, permitting a discussion of skeletal ontogeny. While the narrow fused frontal, flange-like angular process, strong conical teeth and long feet remain constant features throughout development, there are marked changes in cranial sculpture pattern through ontogeny and more minor changes in skull morphology and limb proportions.

Osteological development of the vertebral column and of the fins in Diplodus puntazzo (Cetti, 1777)

The normal development of the vertebral column and of the fins in Diplodus puntazzo (Cetti, 1777) was studied. The ontogenetic pattern of the skeleton follows that described in all other Sparidae studied so far: the onset of the ontogeny of the vertebral column is at 4.9 mm total length (TL) with the formation of the first neural processes, while the vertebral centra begin forming at 5.8 mm TL and are completed by 8.1 mm TL. Pectoral supports (cleithrum, coracoid-scapula cartilage, fin plate) are the first fin elements to be formed at 2.9 mm TL and are followed by those of the caudal (4.5 mm TL), dorsal, anal (6.4 mm TL) and finally by those of the pelvic fin (8.1 mm TL). The caudal fin is the first to develop fin rays and attain the full count of lepidotrichia (5.8–7.1 mm TL), but the last to attain the full count of all its rays (dermatotrichia, 14.1 mm TL). The next fins to complete their rays are the anal (8.5 mm TL), the dorsal (10.1 mm TL) and finally the pectoral and the pelvic (10.6 mm TL). Fin meristic characters were compared between the reared and 27 wild D. puntazzo juveniles. The results of the skeletal ontogeny are compared with the pattern of development of the Sparidae.

Osteological development of the vertebral column and of the fins in Pagellus erythrinus (L. 1758). Temperature effect on the developmental plasticity and morpho-anatomical abnormalities

The osteological ontogeny of Pagellus erythrinus (Linnaeus, 1758) and its temperature-induced plasticity is studied. The ontogeny of the skeleton follows the pattern described in all other Sparidae studied so far: the onset of the ontogeny of the vertebral column and the caudal fin is at 4.3 mm total length (TL) and the completion at 17.6 and 15.4 mm TL, respectively. Dorsal and anal fin development appears at about 5.2 mm TL and completes at 7.5 mm TL. The pelvic are the last fins to develop (7.5–11.5 mm TL). Although the pectorals are the only fins present before first feeding, their ontogeny is completed only after 12.0 mm TL. Temperature affects the developmental rate of the skeleton giving as much as 10.9% of differentiation in total length between 16 and 21 °C (caudal lepidotrichia), 9.2% between 16 and 18 °C (caudal lepidotrichia) and 6.7% between 18 and 21 °C (pelvic lepidotrichia). The role of temperature in developmental plasticity is enhanced by the induction of abnormalities mainly in the area of the caudal fin, which reached (in total) 75% occurrence in the higher temperature regime (23 °C) tested. The results of the skeletal ontogeny are compared with the pattern of development of the Sparidae, and are discussed in respect to the role of temperature in the developmental plasticity of fish.

Comments on Basal Teleosts and Teleostean Phylogeny, by Gloria Arratia

For more than 20 years, Gloria Arratia has been a prolific contributor on Mesozoic fossil fishes and on the skeletal ontogeny and morphology of Recent teleosts. Often writing with her husband, Hans-Peter Schultze, she has produced (among much else) a notable series of papers on the caudal skeleton of Recent lower teleosts and on the palatoquadrate and urohyal (e.g., Arratia, 1991; Arratia and Schultze, 1991, 1992). Her most recent monograph (Arratia, 1997) covers Jurassic fossils representing eight genera (one of which is the Recent Elops), two of them new, and also describes the firstJurassic leptocephali or transforming leptocephali. As usual with Arratia's work, the descriptions of fossils are as complete as the specimens allow, and the illustrations are excellent.

Postembryonic ontogeny of the spadefoot toad, Scaphiopus intermontanus (Anura: Pelobatidae): skeletal morphology.

Postembryonic skeletal ontogeny of the pelobatid frog Scaphiopus intermontanus is described based on a developmental series of cleared-and-stained, whole-mount specimens. The focus is on laboratory-reared individuals fed a herbivorous diet as larvae. Although there is variation in the timing of ossification of individual skeletal elements relative to developmental stages based on external morphological criteia, the sequence of skeletal development generally is conservative. Compared with its close relative, S. bombifrons, ossifications that occur during prometamorphosis tend to be slightly delayed in S. intermontanus; however, cranial bones that ossify during late metamorphic climax in S. intermontanus are delayed until post-metamorphosis in S. bombifrons. The differences in timing between the two species are consistent, however, with differences observed between two developmental series of S. intermontanus raised at two different temperatures. Noteworthy features of skeletal development in S. intermontanus include: 1) presence of palatine ossifications that form from independent centers of ossification and soon fuse with the postnarial portion of the vomers to form the compound vomeropalatine bones; 2) compound sphenethmoid that may arise from four or more endochondral centers of ossification and one dorsal, dermal center of ossification; and 3) presence of transverse processes and vestigal prezygapophyses on the first postsacral vertebra. The morphology of the larval orbitohyoideus and interhyoideus muscles is compared. The record of skeletal ontogeny and muscle morphology presented herein for the herbivorous larval morph can serve as a baseline for comparisons with the ontogeny of the carnivorous larval morph of Scaphiopus.

Postembryonic ontogeny of the spadefoot toad, Scaphiopus intermontanus (Anura: Pelobatidae): Skeletal morphology

Postembryonic skeletal ontogeny of the pelobatid frog Scaphiopus intermontanus is described based on a developmental series of cleared-and-stained, whole-mount specimens. The focus is on laboratory-reared individuals fed a herbivorous diet as larvae. Although there is variation in the timing of ossification of individual skeletal elements relative to developmental stages based on external morphological criteria, the sequence of skeletal development generally is conservative. Compared with its close relative, S. bombifrons, ossifications that occur during prometamorphosis tend to be slightly delayed in S. intermontanus; however, cranial bones that ossify during late metamorphic climax in S. intermontanus are delayed until postmetamorphosis in S. bombifrons. The differences in timing between the two species are consistent, however, with differences observed between two developmental series of S. intermontanus raised at two different temperatures. Noteworthy features of skeletal development in S. intermontanus include: 1) presence of palatine ossifications that form from independent centers of ossification and soon fuse with the postnarial portion of the vomers to form the compound vomeropalatine bones; 2) compound sphenethmoid that may arise from four or more endochondral centers of ossification and one dorsal, dermal center of ossification; and 3) presence of transverse processes and vestigal prezygapophyses on the first postsacral vertebra. The morphology of the larval orbitohyoideus and interhyoideus muscles is compared. The record of skeletal ontogeny and muscle morphology presented herein for the herbivorous larval morph can serve as a baseline for comparisons with the ontogeny of the carnivorous larval morph of Scaphiopus. J. Morphol. 238:179–244, 1998. © 1998 Wiley-Liss, Inc.

Juvenile Skeletal Structure and the Reproductive Habits of Dinosaurs

Skeletal ontogeny in extant archosaurians (crocodilians and birds) indicates that the morphology of the perinatal pelvic girdle is an indicator of overall developmental maturity [that is, altriciality (nestbound) versus precociality (mobile and relatively independent)]. Comparison of the skeletal anatomy of perinatal extant archosaurians and perinatal dinosaurs suggests that known dinosaur hatchlings were precocial. These data are consistent with the overall similarity in nesting behavior of dinosaurs and modern crocodilians.

Skeletal ontogeny and feeding mechanisms in conodonts

The growth and function of the conodont skeletal apparatus have important implications for early vertebrate relationships and the evolution of vertebrate hard tissues, yet they are poorly understood. Analysis of element length, platform linear dimensions, and platform area in discrete Pa elements of Carboniferous Idiognathodus and Gnathodus bilineatus reveals that the platform increased in size at a rate significantly above that required to maintain geometric similarity. Measurements of P, M and S elements in bedding-plane assemblages of Idiognathodus and G. bilineatus indicate that relative to Pa element length, Pb and S element growth was isometric, whereas M elements grew with negative allometry. There is no evidence to support loss or resorption of S and M elements in later growth stages, or to indicate periodic shedding and replacement of elements. These results are important for understanding apparatus and element Function. The positive allometry of the Pa element platform supports interpretations of a mashing or grinding tooth-like Function for platformed Pa elements. If conodonts were active suspension-feeders, the increasing food requirements of a growing conodont would require the filter array formed by the S and M elements to have grown at a rate significantly above isometry. The lack of positive allometry of S and M elements indicates that conodonts were not suspension-feeders and supports hypotheses that conodonts fed with a raptorial apparatus and teeth. □Conodonts, vertebrates, skeletal apparatus, ontogeny, allometry, function, suspension-feeding, teeth.

Feeding mechanisms in conodonts and the function of the earliest vertebrate hard tissues

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Growth in encrusting cheilostome bryozoans: II. Circum-Atlantic distribution patterns

Differences in zooid skeletal ontogeny are strongly linked to the distribution of bryozoan species, even along such large-scale environmental gradients as depth and latitude. Three growth patterns broadly characterize zooid formation for encrusting cheilostome bryozoans: zooidal and intrazooidal budding, which facilitate growth in two dimensions at colony margins; and frontal budding, which also permits upward growth in the third dimension. Analyses of skeletal growth patterns of encrusting species present in 230 Recent assemblages from the North Atlantic, Mediterranean, North Sea, and Gulf of Mexico show that species with zooidal budding dominate overwhelmingly at lower latitudes and in shallower water, as assessed by percentages of species within assemblages. In contrast, patterns within moderately diverse fossil assemblages from North America indicate that within the geographic and environmental limits sampled, species with intrazooidal budding once dominated and probably originated in shallow, warm water environments. Intrazooidal budding now occurs with greater relative frequency among species from deeper and higher latitude assemblages. Patterns for frontal budding suggest a slight decrease with increasing depth, but no consistent relationship with latitude. These paleoenvironmental trends occur withn a putatively monophyletic clade and are markedly similar to onshore/offshore trends recognized in other groups of marine benthos, based on patterns of occurrence of supra-specific taxa and novel morphotypes. Results presented here are based on relative dominance of species within assemblages and thus provide a novel comparative test of these previously reported trends.

Fine Structure of Radiolaria: ABSTRACT

Fine structure and physiological studies of major biological End_Page 412------------------------------ processes in solitary and colonial radiolarians have begun to elucidate some of the adaptive mechanisms that may account for the remarkable success of these holoplankters in diverse oceanic environments. The diversity of algal symbionts including dinoflagellates, prasinophytes, and a brown-pigmented alga has been documented by light and electron microscopy, and the role of the symbionts in host nutrition has been determined for some solitary and colonial species using cytochemical and radioisotopic techniques. Fine structure analysis of predatory behavior and food vacuole contents shows that some larger solitary spumellarian species are omnivores consuming crustacean prey and other microzooplankton in addition to algae. This is in contrast to prior assumptions that most solitary radio arians are microherbivores and therefore changes our conception of their niche in oceanic environments. Fine structure examination of skeletal morphogenesis in a number of solitary and colonial species has clarified the mechanism of skeletal deposition and pattern of skeletal ontogeny. These studies contribute to our understanding of cellular specialization in radiolarians, their physiological adaptive mechanisms to a holoplanktonic existence, and the biological factors correlated with patterns of skeletal morphogenesis that may be useful in interpreting radiolarian evolution and paleoecology. End_of_Article - Last_Page 413------------

Daily growth layers in locust rubber-like cuticle influenced by an external rhythm

The first experimentally verified daily growth layers in insects have been located in sections of desert locust rubber-like cuticle. Paired growth zones in the resilin are fluorescent in u.v. light and result from a daily deposition rhythm. During night conditions, a wide brightly fluorescent zone is deposited. Three days' deposits are formed in the ligaments of the pharate adult before emergence. Thereafter, one layer is added per day until the ligaments are full-grown. Experimentally prolonged days and nights induced corresponding wide dimly or brightly fluorescent zones. Paired daily growth zones of a different nature occur in the solid cuticle. The discovery is likely to provide a useful analytical and experimental method in many fields of entomology. This is discussed in relation to skeletal ontogeny, cuticle studies, regeneration and wound reactions, vision, population ecology and field studies of cuticle maturation.