Journal of Morphology

doi: 10.1002/jmor.1051980101pmid: N/A

El Shoura, Samir M.

doi: 10.1002/jmor.1051980102pmid: 29898574

The ultrastructure of the nymphal integument in the ixodid tick Hyalomma (Hyalomma) dromedarii is compared for stages of development during and after feeding, and up to the first step of molting, apolysis. The integument comprises a cuticular layer and underlying epidermal cells. The body cuticle, which consists of both sclerotized and non‐sclerotized parts, is divided into an outer, thin epicuticle, and an inner, thick, fibrillar procuticle. Pore canals in the procuticle are continuous with wax canals which traverse the epicuticle. As feeding progresses, the parallel, extensible epicuticular folds disappear due to the gut filling with ingested blood. The procuticular zone, however, becomes subdivided into an exocuticle, similar to the previously seen procuticle, and a lamellate endocuticle. Pore canals lose their parallel pattern and appear to have become deformed by stretching of the cuticle.

Mackie, G. O.; Singla, C. L.; Arkett, S. A.

doi: 10.1002/jmor.1051980103pmid: 29884016

Silver impregnations, immunofluorescence microscopy, and electron microscopy of the nervous system of Velella confirm previous reports that there are two nerve nets, one composed of small and the other of “giant” neurites. Only one of these systems, the small‐fibered open one, shows FMRFamide‐like immunoreactivity. It appears to be primarily a sensory network. Despite presence of a neuropeptide in these neurons, they did not contain dense‐cored vesicles. The “giant” nerve net (closed system) shows many connections that appear syncytial in the silver preparations. While it is confirmed that gap junctions are present between some neurites in the closed system, it is likely that fusion of neurites also occurs and that the system is a partial syncytium. Membrane complexes with gap junctions are abundant in the cytoplasm. It is suggested that fusion occurs by the engulfment of small neurons by large, resulting in an excess of cell membrane, which is internalized with gap junctions still intact. These internalized membranes appear to break up into vesicles eventually. A similar process may occur in the “giant” swimming motor neuron net of the medusa Polyorchis.

Donald, John A.; Lillywhite, Harvey B.

doi: 10.1002/jmor.1051980104pmid: 3199447

Fluorescence histochemsitry was used to study the adrenergic innervation of the large arteries and veins at six points along the body of the semiarboreal rat snake Elaphe obsoleta. Apart from the vessels adjacent to the heart, there was a marked contrast in the density of adrenergic innervation of anterior and posterior systemic arteries and veins. The anterior arteries and veins have little adrenergic innervation in contrast to the extremely dense innervation of the arteries and veins posterior to the heart. The innervation pattern is consistent with known physiological adjustments to gravity and suggests a mechanism for regulating dependent blood flow via sympathetic nerves. In comparison to the posterior systemic arteries, parallel segments of pulmonary artery taken from the same body position of Elaphe contained a much sparser innervation by adrenergic nerves. The sparser innervation can be correlated with less gravitational disturbance in the pulmonary artery, which is relatively short in this and in other arboreal snakes.

Smith, Patricia; Samuelson, Don; Brooks, Dennis

doi: 10.1002/jmor.1051980105pmid: 3199448

The anterior vasculature of the pony eye was examined by the corrosion cast method. The anterior segment of the pony eye has a vascular pattern which is similar but distinct from that of other mammalian species. Large iridal veins collateralized directly with the anterior vortex venous system. The intrascleral plexus was present but formed a fine, radially oriented, extensive network. This contrasted to the circumferential larger‐diameter intrascleral plexus noted in dogs and the canal of Schlemm present in primates. The intrascleral plexus only drained posteriorly in the pony as compared to that in other species where anterior collateralizations have been described. The pattern of aqueous outflow was found to have relevance clinically in veterinary medicine and could provide insight into the frequent occurrence and treatment of equine recurrent uveitis as well as diseases of the posterior segment.

Zeni, Cristina; Zaffagnini, Fulvio

doi: 10.1002/jmor.1051980106pmid: 29884017

Electron microscopy discloses nerve endings in contact with gland cells situated in the labrum of Daphnia. Swellings of nerve fibers are in close contact with gland cell membranes, either on the cell surface or inserted into infoldings of plasma membrane. The axonal processes are single or double and lack glial wrappings. Inside the nerve fibers are vesicles of different sizes and electron density. These include granular vesicles, which often are dense‐cored, and also clearer vesicles.

Sokolowski, Bernd H. A.; Popper, Arthur N.

doi: 10.1002/jmor.1051980107pmid: 3199449

The development of the sensory epithelium of the saccular macula of Opsanus tau was studied with transmission electron microscopy. In the 10–12 somite embryo all cells of the newly formed otocyst are morphologically undefined, having an apically placed cilium with an underlying basal body and parabasal body. Junctional complexes are characterized primarily by tight junctions and a few desmosomes. In the 17‐somite embryo the sensory cells begin to differentiate and are definable by the development of microvilli, which lack a cuticular plate. When the embryo has approximately 25–30 somites, ganglion cells differentiate and send their nerve processes toward the thin, disrupted basal lamina and the developing rhombencephalon. Desmosomes are more definable in the sensory regions at this age.

Hoggarth, Michael A.; Gaunt, Abbot S.

doi: 10.1002/jmor.1051980108pmid: 29879796

Glochidia are third‐class levers in which the valves form the lever arms and the single adductor muscle produces the force. In this study the lengths of the lever arms and the areas of glochidial valves and adductor muscles were determined for 57 species of unionid glochidia. The position of the adductor muscle relative to the dorsal margin of the larval valve was also determined for each species. From these data and an analysis of the possible configurations of adductor muscle and valve dimensions, we determined that most of the glochidia within the Unionidae emphasize area of sweep during valve adduction. These glochidia possess long resistance arms and short force arms and generally had small‐diameter adductor muscles. Other glochidia, however, were found to possess one or all of the following: short resistance arms, long force arms, and large‐diameter adductor muscles. It is suggested that these glochidia are adapted for strength of valve adduction and that for these larvae a trade‐off exists between strength of valve adduction and acceptable valve gape. Furthermore, this study suggests that the mode of attachment employed by glochidia has played a major role in the development of these bivalve larvae and has produced convergence in valve shape and adductor muscle size.

Thomopoulos, George N.

doi: 10.1002/jmor.1051980109pmid: 29898570

Larval salivary gland cells of seven Drosophila species from the melanogaster group were studied during the early third‐instar period. Similar cytoplasmic organization was seen in both the distal and proximal parts of the gland. The cytoplasm contained a large number of free ribosomes, but only a few rough endoplasmic reticulum profiles; the nucleolus was very large. Golgi complexes consisted mainly of vesiculated cisternae. Small secretory granules (diameter, 0.23–0.32 μm) are produced during this period and in some species contain both granular and filamentous material. These granules appeared to be secreted by a peculiar “apocrine‐type” secretion after enclosure of granules into microvillar “lacunae.” A digestive function is attributed to the secretory material. During the third instar, a close association between the salivary gland and the fat body also was observed. The physiological significance of this association seems to be related to the transfer of nutrients, enzymes, or membranous materials from fat body to salivary gland.

Sprando, R. L.; Russell, L. D.

doi: 10.1002/jmor.1051980110pmid: 3199450

Nuclear and cytoplasmic volume changes as well as the elimination of residual spermatid cytoplasm were investigated in the red‐ear turtle (Pseudemys scripta) and the rooster (Gallus domesticus). Nuclei of newly formed spermatids which were originally centrally located became eccentrically located within the cell in both species. Shortly thereafter the nuclear pole of the spermatid was found situated within deep crypts of a Sertoli cell. The cytoplasm of elongating spermatids was displaced along the nonacrosomal region of the nucleus and the proximal flagellum. In both species sheetlike Sertoli cell processes indented spermatid cytoplasm adjacent to the nucleus and appeared to segregate small packets of the cytoplasm. In the turtle, these packets of cytoplasm were separated from the spermatid. In both the turtle and rooster, a portion of the spermatid cytoplasm was displaced forward over the acrosomal region of the spermatid to resemble a hood. As spermatids were transported to the seminiferous tubular lumen, cytoplasmic lobes which projected forward of the spermatid head were formed by preferential flow of cytoplasm into one aspect of the cytoplasmic hood. In both species, at sperm release the cytoplasmic lobe was disengaged from the spermatid head to form a large residual body that was internalized and degraded within the Sertoli cell. Medium‐sized cytoplasmic lobes were pinched from the head and neck region of the turtle and rooster spermatids, respectively. In the turtle, small‐sized mitochondrial‐rich cytoplasmic fragments budded from the caudal head and midpiece of the spermatids and were phagocytosed by the Sertoli cell. Thus, cytoplasmic elimination occurred through (1) segregation of cytoplasmic packets by Sertoli penetrating processes (turtle), (2) elimination of large and medium‐sized residual bodies from the head (turtle and bird), and (3) budding of small mitochondrial‐rich cytoplasmic fragments from the region of the midpiece (turtle). In the turtle a 79% reduction in total cell volume occurred during spermiogenesis which was the result of an 84% cytoplasmic reduction and a 78% nuclear reduction. During spermiogenesis, the rooster lost 97% of its total cell volume due to a 97% cytoplasmic volume change and a 96% nuclear volume change.