The endoskeletal structure supporting the gill-books of Limulus polyphemus has been investigated by means of light and electron microscopy, chemical analysis and x-ray diffraction. This tissue is a cartilage which has significant correspondences with both vertebrate cartilage and plant tissues. Morphologically, the Limulus cartilage resembles certain cellular vertebrate cartilages with relatively scant matrix, and also certain plant parenchyme, collenchyme and sclerenchyme tissues. Of particular interest, was the observation that during cytoplasmic division, a phragmasome-like structure appears between the daughter cells of the dividing gill cartilage cells. This phragmasome-like structure appears to be a precursor of new matrix (cell-wall) formation between the young chondrocytes, in much the same fashion as its counterpart in plant tissues. Perichondrial cells and underlying chondrocytes contain lipid droplets, abundant glycogen and ribosomes, as do corresponding vertebrate cartilage cells. In some of the Limulus cells, glycogen and ribosomes appear to be admixed with lipid, forming aggregates in which all three materials are in intimate intraparticulate relationship. During molting, the number of ribosomes seen in chondrocytes increases. The tissue contains both hydroxyproline and hydroxylysine, and gives a weak x-ray diffraction pattern.
"The endoskeleton resembles cartilage thought to be present in many invertebrates [31,32,35-39]. It apparently gives support to the basal portion of at least some of the embryonic appendages in their early stages of development. "
[Show abstract][Hide abstract] ABSTRACT: The transmission electron microscope (TEM) is used for the first time to study the development of book gills in the horseshoe crab. Near the end of the nineteenth century the hypothesis was presented for homology and a common ancestry for horseshoe crab book gills and arachnid book lungs. The present developmental study and the author's recent ones of book gills (SEM) and scorpion book lungs (TEM) are intended to clarify early histological work and provide new ultrastructural details for further research and for hypotheses about evolutionary history and relationships.
The observations herein are in agreement with earlier reports that the book gill lamellae are formed by proliferation and evagination of epithelial cells posterior to opisthosomal branchial appendages. A cartilage-like endoskeleton is produced in the base of the opisthosomal appendages. The lamellar precursor cells in the appendage base proliferate, migrate outward and secrete the lamellar cuticle from their apical surface. A series of external, posteriorly-directed lamellae is formed, with each lamella having a central channel for hemolymph and pillar-type space holders formed from cells of the opposed walls. This repeated, page-like pattern results also in water channels (without space holders) between the sac-like hemolymph lamellae.
The developmental observations herein and in an earlier study (TEM) of scorpion book lungs show that the lamellae in book gills and book lungs result from some similar activities and features of the precursor epithelial cells: proliferation, migration, alignment and apical/basal polarity with secretion of cuticle from the apical surface and the basal surface in contact with hemolymph. These cellular similarities and the resulting book-like structure suggest a common ancestry, but there are also substantial developmental differences in producing these organs for gas exchange in the different environments, aqueous and terrestrial. For scorpion book lungs, the invaginated precursor cells align in rows and secrete rows of cell fragments that are the basis for the internal, anterior-directed air sacs. The hemolymph sacs of book gills are formed by epithelial evagination or outfolding from the posterior surface of the branchial appendages.
Frontiers in Zoology 03/2012; 9(1):4. DOI:10.1186/1742-9994-9-4 · 3.05 Impact Factor
"Conversely, the Limulus branchial bar residual material is quite different in composition , with high proportions of both glutamic acid and arginine, and relatively low proportions of glycine and other non-polar amino acids. It is interesting that the amino acid composition of the CNBr-resistant branchial bar material is almost identical to that reported by Person and Philpott (1969b) for acid hydrolysates of untreated Limulus gill cartilage (Table 3), except for the presence of methionine, perhaps reflecting some contamination with other proteins which would be removed by CNBr treatment. The strong similarities between compositions of untreated and CNBrtreated Limulus branchial cartilage suggest that the residual protein after CNBr makes up the majority of the protein in this cartilage. "
[Show abstract][Hide abstract] ABSTRACT: A collagenous extracellular matrix was previously considered to be a requirement for classification of true cartilage. Data from the lamprey and hagfish now clearly indicate that both of these jawless craniates have extensive non-collagenous, yet cartilaginous endoskeletons. Non-collagenous cartilages are present in the cephalochordates (amphioxus) and in the invertebrates, although collagen-containing cartilages also are found in the invertebrates. This review summarizes current knowledge of the morphological, biochemical and molecular characteristics of the unusual non-collagenous cartilages in jawless craniates and the cartilaginous tissues in amphioxus and invertebrates. A least two types of non-collagenous cartilage matrix proteins are found in both the hagfishes and the lampreys, all of which are resistant to digestion by cyanogen bromide (CNBr). Although all four of these matrices show some similarities with each other, suggesting a family of non-collagenous, elastin-like proteins, it is clear that the major matrix proteins of each are different. New morphological and biochemical information on the cartilaginous tissues in squid, horseshoe crab and amphioxus reveals the presence of CNBr-insoluble, non-collagenous matrix proteins, potentially extending the jawless craniate family of cartilaginous proteins into the invertebrates. Details of the evolutionary relationships between these non-collagenous matrix proteins and the significance of the occurrence of these proteins as the major components of the cartilaginous tissues of jawless craniates, amphioxus, horseshoe crab and squid, all of which are capable of producing a variety of collagens in other tissues, remain to be investigated.
Cell and Tissue Research 06/2001; 304(2):165-74. DOI:10.1007/s004410100374 · 3.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In both light and electron microscopes, head cartilage from the squid Loligo pealii strongly resembles vertebrate hyaline cartilage. The tissue is characterized by the presence of irregularly-shaped cells suspended in an abundant matrix. Cell and matrix contents stain metachromatically with cationic dyes such as toluidin blue. Each cell gives off extensions which ramify via a network of channels throughout the matrix. Thereby, a system of inter-connecting canaliculi is established, with many similarities to the intercanalicular systems seen in vertebrate bone and cartilage tissues. In the electron microscope, the squid cartilage cells are seen to have very abundant endoplasmic reticulum and Golgi complex material. Mitochondrial transformations involving loss of cristae, the appearance of filaments in the mitochondrial matrix, and figures suggesting budding, also occur. Nuclear pores are numerous and easily detected. The matrix is characterized by the presence of a system of decussating fibrils which form polygonal figures, with granules usually evident at the points of intersection of fibrils. By chemical analysis the tissue contains 3- and 4-hydroxyproline and hydroxylysine. Preliminary wide single x-ray diffractions show a pattern characteristic for unoriented collagens, with 12 Å (intermolecular) and 2.86 Å (helix) reflections.
Journal of Morphology 08/1970; 131(4):417-30. DOI:10.1002/jmor.1051310405 · 1.74 Impact Factor
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