The aim of the present study was to obtain a basic knowledge of the hematology of Cichlasoma dimerus. The morphological features of blood cells were described according to the observations made by light and electron microscopy. Erythrocytes, thrombocytes and four types of leucocytes: lymphocytes, monocytes, heterophils and eosinophils, were distinguished and characterized. Thrombocytes are the most abundant blood cells after erythrocytes and are recognized easily from lymphocytes by morphological features and size. Heterophils and eosinophils are PAS positive. Hematological indices (RBC, WBC, PCV, Hb, MCV, MCH, MCHC and leucocyte differential count) were measured in one blood sample from 30 adult fish captured in Esteros del Riachuelo, Corrientes, Argentina (27 degrees 25'S, 58 degrees 15'W). The reference interval and the mean were determined for each hematological parameter evaluated. Contrary to other species, the percent of heterophils was found to be high in relation to the percent of lymphocytes. Low lymphocyte counts occurred in C. dimerus, as compared to these found in other fishes. Compared to most teleosts, this species has similar mean values for PCV and Hb and slightly higher for RBC. Statistical analysis revealed that differences in hematological parameters between male and female fish were not significant.

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Characterization of blood cells and hematological parameters in Cichlasoma dimerus (Teleostei, Perciformes).

Fish granulocytes: Morphology, distribution, and function

The immune system is composed of two subsystems-the innate immune system and the adaptive immune system. The innate immune system is the first to respond to pathogens and does not retain memory of previous responses. Innate immune responses are evolutionarily older than adaptive responses and elements of innate immunity can be found in all multicellular organisms. If a pathogen persists, the adaptive immune system will engage the pathogen with specificity and memory. Several components of the adaptive system including immunoglobulins (Igs), T cell receptors (TCR), and major histocompatibility complex (MHC), are assumed to have arisen in the first jawed vertebrates-the Gnathostomata. This review will discuss and compare components of both the innate and adaptive immune systems in Gnathostomes, particularly in Chondrichthyes (cartilaginous fish) and in Osteichthyes [bony fish: the Actinopterygii (ray-finned fish) and the Sarcopterygii (lobe-finned fish)]. While many elements of both the innate and adaptive immune systems are conserved within these species and with higher level vertebrates, some elements have marked differences. Components of the innate immune system covered here include physical barriers, such as the skin and gastrointestinal tract, cellular components, such as pattern recognition receptors and immune cells including macrophages and neutrophils, and humoral components, such as the complement system. Components of the adaptive system covered include the fundamental cells and molecules of adaptive immunity: B lymphocytes (B cells), T lymphocytes (T cells), immunoglobulins (Igs), and major histocompatibility complex (MHC). Comparative studies in fish such as those discussed here are essential for developing a comprehensive understanding of the evolution of the immune system.

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A Comparison of the Innate and Adaptive Immune Systems in Cartilaginous Fish, Ray-Finned Fish, and Lobe-Finned Fish

The features of unlesioned and lesioned trochlear nerves of goldfish have been examined electron microscopically. Lesioned nerves were studied between 1 and 107 days after cutting or crushing the nerve.

1.

Unlesioned nerves contained, on average, 77 myelinated axons and 19 unmyelinated axons. The latter were found in 1–2 fascicles per nerve. A basal lamina surrounded each myelinated axon and fascicle of unmyelinated axons. The numbers of myelinated axons, fascicles of unmyelinated axons and basal laminae varied by less than 5% over the intraorbital extramuscular segment of the nerve.




2.

Following interruption of the nerve, by either cutting or crushing, all of the axons and their myelin sheaths began to degenerate by 4 days in the distal nerve-stump. Both abnormally electron-dense and electron-lucent axons were observed. Both Schwann cells and macrophages appeared to phagocytose the myelin sheaths.




3.

Following a lesion, the Schwann cells and their basal laminae persisted in the distal nerve-stump. In crushed nerves, the basal laminae surrounding myelinated axons formed 97%, on average, of the Schwann tubes in the distal stump. The perimeters of the basal laminae were of similar size to those in the proximal stump, at least for the first 8 days after crush.




4.

In crushed nerves, single myelinated axons in the proximal nerve-stump gave rise to multiple sprouts, some of which reached the site of crush by 2 days, the distal stump by 4 days and the superior oblique muscle by 8 days. The regeneration of the unmyelinated axons was not examined.




5.

In both crushed and transected nerves, nearly all of the sprouts in the proximal and distal stumps were found within the basal laminae of Schwann cells, even though the sprouts were disorganized in the transected region where there were no basal laminae. The growth cones of the regenerating axons were always found apposed to the inner surface of the basal laminae, which may have provided an adhesive substrate that directed their growth.




6.

Terminal sprouts from the ends of myelinated axons in the proximal stump accounted for the majority of the regenerating axons in the distal stump, as only a few collateral sprouts were found in the proximal stump, and only a small amount of axonal branching was found within the distal stump itself.




7.

The largest axons in the distal stump were remyelinated first, and the number of remyelinated axons increased progressively between 8 and 31 days after crush, at which time there were about twice as many as in unlesioned nerves. The number of remyelinated axons remained constant at least until 107 days, the longest time considered, and none was observed to degenerate, whereas some axons that were not remyelinated appeared to degenerate.




8.

Although each basal lamina in the distal stump often surrounded several regenerating axons during the first 2 weeks post-lesion, each remyelinated axon became individually surrounded by a basal lamina, collagen fibres and extracellular space between 13 and 107 days, thereby increasing the number of basal laminae in the distal stump.




9.

Regenerated axonal terminals in the superior oblique were first observed 8 days after crush. The number of synapses increased progressively between 8 and 107 days, at which time they were as numerous as in unlesioned animals.

/pdf/degenerative-and-regenerative-changes-in-the-trochlear-nerve-1xg6ku997j.pdf

Degenerative and regenerative changes in the trochlear nerve of goldfish

The purpose of this study was to compare the phagocytosis of Aeromonas hydrophila, Edwardsiella ictuluri, Edwardsiella tarda and Micrococcus luteus by channel catfish neutrophils. Various aspects of opsonization effect and bactericidal ability of channel catfish neutrophils were investigated. Percent phagocytosis range from a low of 1% to a high of 91%. The highest percent phagocytosis and phagocytic indices routinely occurred with normal serum and were highest for M. luteus (91.78%, 55.25) and A. hydrophila (87.52%, 43.60). In all cases, the percent phagocytosis and phagocytic index was lowest in assays without serum. Channel catfish neutrophils displayed a bactericidal/static ability for each bacterium tested except E. tarda . Neutrophils exhibited a greater inhibitory capacity for A. hydrophila and M. luteus than for the other bacteria when in the presence of normal or inactivated catfish serum.

Differences in the phagocytosis of four bacteria by channel catfish neutrophils.

Ultrastructural studies on blood leukocytes of the channel catfish, Ictalurus punctatus, show the presence of heterophils (neutrophils), small lymphocytes, monocytes, and thrombocytes. Monocytes cannot always be distinguished from large lymphocytes. Cells resembling macrophages or transitional forms between monocytes and macrophages are occasionally seen. Blood eosinophils and basophils are not found. Thrombocytes and small lymphocytes are the most abundant leukocytes, while monocytes are the least frequently encountered leukocyte. Glycogen, present in all leukocytes, is most abundant in heterophils and least abundant in monocytes. Although monocytes are similar to heterophils in size and shape, a greater amount of rough endoplasmic reticulum, free ribosomes, and fewer granules are observed in monocytes. Heterophils possess oval or elongate granules, which often contain a crystalline or striated structure; small tubules which resemble smooth endoplasmic reticulum, and cristae which traverse the long axes of the mitochondria are frequently seen. Small lymphocytes are characterized by the presence of pseudopodia, many free ribosomes, numerous large mitochondria, dictyosomes (Golgi), and long profiles of rough endoplasmic reticulum. The dictyosomes are often associated with a large zone of exclusion. Bundles of microtubules are observed near the elongated ends of thrombocytes. Deep indentations of the plasmalemma, which give the appearance of vacuoles, are also seen in thrombocytes.

M. Samuel Cannon

Papers

An ultrastructural study of the leukocytes of the channel catfish, Ictalurus punctatus.