Wiley: Journal of Morphology: Table of Contents

Alterations of Growth Trajectories in Rook (Corvus frugilegus) Ontogeny

Oksana V. Shatkovska, Maria Ghazali, Ivan S. Mytiai — Tue, 09 Jun 2026 00:55:44 -0700

Scaling of the head, forelimb, and hind limb relative to body mass varies considerably across ontogeny. The period between the end of embryogenesis and the beginning of postnatal development deviates from the general pattern of growth due to a decrease in the relative growth of all traits. Despite the relatively consistent development of traits across ontogeny, the hind limbs exhibit the highest growth rate during embryogenesis, whereas the forelimbs grow faster during most of postnatal development.

ABSTRACT

The growth of birds is a subject of constant interest to researchers, and somewhat contradictory data on this issue have accumulated. It is known that the growth patterns of fore- and hind limbs differ during the embryonic and postnatal periods, whereas their increments change rather similarly. The question arises: how are these contradictory trends reconciled, and what role do they play in shaping body proportions? Our study was carried out on Rook embryos and nestlings. We studied the dynamics of changes in head, forelimb, and hind limb length in relation to body mass using regression analysis. Then, the dynamics of relative sizes were compared with the dynamics of relative increments of these traits that we studied earlier. We distinguished four periods in the dynamics of relative sizes, just as we identified earlier in the dynamics of relative increments, when the growth trajectories of traits undergo significant changes. The studied traits scaled mainly with positive allometry in the first period (from the 10th to 13th days of embryogenesis) and third period (from the 5th to 23rd days of the postnatal period), negative allometry in the second period (from the 14th day of embryonic to the 3rd day of postnatal development) and isometrical in the fourth period (from 25th to 30th days of the postnatal period). Despite the roughly consistent changes in an organism within the designated periods, variations in the regression exponents led to changes in proportions. The hind limb had the highest growth rate during embryogenesis, while the forelimb grew faster across most of the nesting period. We assume that changes in the dynamics of body parts' growth are associated with the preparation of organs for function and with the influence of factors that limit the growth of an entire organism.

Spinal Cord Supports in Caecilian Vertebrae and Their Significance for Amphibian Systematics

Rodolfo Otávio Santos, Mark Wilkinson, Hussam Zaher — Sun, 07 Jun 2026 23:02:37 -0700

This study reports the widespread presence of spinal cord supports within the neural canal of caecilian amphibians (Gymnophiona). Micro-CT scans and histological sections reveal that these structures, previously considered unique to salamanders, occur as medially projecting bony protuberances at least in the atlas of most examined species. Additionally, shallow grooves on the inner walls of the neural canals are proposed as non-ossified homologs to these supports. Similar grooves are also shown to occur on a fossil vertebra of the albanerpetid Wesserpeton evansae. This newly uncovered morphological diversity provides novel characters for caecilian systematics and prompts a reassessment of current hypotheses regarding the evolution of spinal cord supports in tetrapods.

ABSTRACT

Spinal cord supports (medially projecting bony protuberances within the neural canal) are found in several lineages of fossil and extant salamanders and have been interpreted as a synapomorphy of Caudata. Previous studies that have reported the absence of spinal cord supports in caecilian amphibians were based on an incomplete survey. Here, we re-examine the condition in caecilians using micro-CT scans and histological sections of vertebrae. We find that spinal cord supports are widespread among caecilians, occurring at least in the atlas of most examined species. In caecilians, the supports are most prominent in the atlas and appear to form through the expansion of the perichondral ossification of the septal bundles, consistent with the condition observed in salamanders. The presence of spinal cord supports in caecilians requires a reassessment of current hypotheses regarding the evolution of this character in tetrapods and may help clarify the phylogeny of Lissamphibia. Variation within Gymnophiona may provide novel characters of use in caecilian systematics.

Functional Anatomy of the Pharynx of Glycera tridactyla Schmarda, 1861 (Annelida: Glyceriformia: Glyceridae)

Fri, 05 Jun 2026 16:49:57 -0700

Micro-CT technology was used to investigate the functional anatomy of the pharynx in the polychaete Glycera tridactyla. The study revealed a complex system of pharyngeal muscles, including ring muscles, retensor muscles, intestinal retractor muscles, and longitudinal muscles of the buccal tube and oesophagus. This muscular system plays a crucial role in proboscis movement, enabling efficient burrowing and feeding behaviour in these polychaetes.

ABSTRACT

The pharyngeal muscular system of polychaetes is highly complex and shows remarkable variation in structure and function among taxa. In this study, the functional anatomy of the pharynx of G. tridactyla was investigated using micro-computed tomography (micro-CT). Sixteen Glycera specimens were imaged in different pharyngeal positions to examine the roles of key muscular structures in pharyngeal movement. The high-resolution imaging provided by micro-CT allowed visualisation of the pharyngeal muscles in their original topography, revealing essential components for pharyngeal function, including the ring muscle, retensor muscles, intestinal retractor muscles, and longitudinal muscles of the buccal tube and oesophagus. Comparison with previous studies addressed gaps in our knowledge of Glyceridae functional anatomy. Specifically, detailed analysis of the muscular system in different pharyngeal positions clarified the mechanisms of proboscis movement, which indicate the rapid and effective responses of these worms during burrowing and feeding behaviour.

Diversity of Resilin Incidence in the Insect Leg

Steven Lerch, Bernard Moussian — Sun, 31 May 2026 23:12:30 -0700

Resilin incidences in the insect cuticle are commonly detected by fluorescence microscopy using the property of Resilin protein matrices to emit blue light after excitation with UV light. This indirect method produces significant background signal. We analyzed Resilin incidences by eliminating background information through subtraction of signal intensities induced with the same light source and recorded with two filter setups (DAPI and DT) with overlapping emission detection windows. As shown here in the Locusta migratoria trochanter (th) that bridges the femur (fr) and the coxa (co) podomeres, we detected signals in three different areas: target signal area (TSA), background area (BGA) and the non-target signal area (nTSA). In brief, by this simple method, we were able to reduce the background and enhance the fidelity of Resilin incidence post-microscopy. Additional normalization allowed broad comparison of the data that indicate that Resilin incidences in 29 insect species representing 7 orders are not conserved.

ABSTRACT

Insect movements rely on membranous elastic types of cuticles that bridge hard and tanned types, which serve as an exoskeleton. A prominent, polymerous protein of membranous cuticles is Resilin, known for its flexibility and visco-elasticity. In the articulated legs, including the coxa, the trochanter, the femur, the tibia and the tarsi, Resilin incidences in or at the joints of these podomers have been identified in various species such as the fruit fly Drosophila melanogaster and the desert locust Schistocerca gregaria relying on Resilin autofluorescence. A systematic, comparative and standardized work on Resilin identification in insect legs is yet missing. Here, we identified Resilin incidences in the legs of 29 model and non-model species belonging to the major insect orders by harmonizing fluorescence signal intensities using the microscopic intensity subtraction method. We both confirm the presence of known Resilin locations and identify new incidences in the podomers, such as a coxa–trochanter signal. Together, we find that Resilin distribution in insect legs is highly diverse with no incidence common to all species tested. This underlines that the use of Resilin follows a rapid and optimizing evolutionary adaptation. Our data pave the path for studies of the comparative function of Resilin in insect legs.

Immunohistochemistry of Salivary Enzymes and Morphology of Salivary Glands in Eurycea (Plethodontidae)

Sun, 31 May 2026 23:05:56 -0700

The morphology and enzyme content of salivary glands are documented in Eurycea (Plethodontidae, subfamily Hemidactyliinae) using histology and immunohistochemistry. Amylase and protease are present in the intermaxillary gland and surface epithelium of the tongue, but absent from the lingual gland. These results propose that the intermaxillary gland is primarily responsible for saliva secretion, whereas the lingual gland plays a different role.

ABSTRACT

Although they potentially share ancestral heritage with the mental gland, salivary glands have not been studied thoroughly in plethodontid salamanders. Previous enzymatic studies in other families of amphibians have identified the presence of proteases and amylases, which are thought to be secreted from the intermaxillary gland and lingual gland. However, no such studies have been conducted in plethodontid salamanders, and the enzyme contents of these glands are poorly understood. We used immunohistochemistry to identify the presence of amylase, protease, and lipase in the glands of three species of Eurycea. Histological descriptions—based on hematoxylin and eosin staining—of the studied glands are also included. We found that amylase and protease were present in the intermaxillary gland and in the surface epithelium of the tongue. The lingual gland was notably lacking salivary enzymes. Preliminary results indicate the possible presence of lipase in the mouth of plethodontid salamanders. This study confirms the intermaxillary gland as a major salivary organ, while contrasting with the previous understanding of the amphibian lingual gland.

Issue Information

Sun, 31 May 2026 22:35:09 -0700

Journal of Morphology, Volume 287, Issue 6, June 2026.