Lepisosteus Osseus Research Articles

The diencephalon and optic tectum of the longnose gar, Lepisosteus osseus (L.): cytoarchitectonics and distribution of acetylcholinesterase.

The cytoarchitecture of nuclei in the diencephalon and the distribution of acetylcholinesterase (AChE) in the diencephalon and optic tectum were analyzed in the longnose gar, Lepisosteus osseus, a non-teleost actinopterygian fish. Nuclei were identified in the preoptic area, thalamus, posterior tubercle, hypothalamus, synencephalon, and pretectum which are homologous to like-named nuclei in teleosts and other non-teleost actinopterygians. Of particular note, a nucleus in the rostral diencephalon, nucleus rostrolateralis, which has previously been identified only in the osteoglossomorph Pantodon, is present in the long-nose gar. The posterior pretectal nucleus, previously identified in teleosts and in the bowfin Amia, is also present in gars. The small size of the posterior pretectal nucleus in gars supports the hypothesis that this nucleus was small plesiomorphically. The distribution of AChE in the diencephalon and optic tectum corresponds in most respects to that found in teleosts. The superficial pretectal nuclei, including the posterior pretectal nucleus, are strongly positive for AChE. In contrast, most of the nuclei within the preglomerular complex are negative for AChE. Acetylcholinesterase is present in some of the fibers in the optic tracts and in most retinorecipient nuclei, as well as in some other nuclei and tracts.

The effect of armored skin on the swimming of longnose gar, Lepisosteus osseus

Fast-starts and steady swimming were compared for two piscivorous fishes, the longnose gar (Lepisosteus osseus), which has an integument armored with ganoid scales, and the unarmored tiger musky (Esox sp.). The body was similarly flexed by both species during fast-starts and steady swimming. Therefore, the heavy integument of the gar did not affect flexibility during swimming. Distance traveled in a given elapsed time during fast-starts was lower for the gar, which averaged 65% of the work done by the musky. On the basis of differences in muscle mass, gars would be expected to perform 72% of the work of muskies during a fast-start. The heavier integument of the gar was estimated to contribute about 90% to the reduced fast-start performance. In steady swimming, mechanical power requirements at a given speed were similar for both gar and musky. Therefore, steady swimming costs do not appear to be affected by armor. The critical swimming speed of gars was 1.9 body lengths/s compared with 3.4 body lengths/s for muskies, but the difference could not be attributed to differences in armoring. The slip speed at which gars first began to swim was 1.21 body lengths/s compared with 0.75 body lengths/s for muskies. Higher station-holding performance is probably not important to modern gars and esocids, but may have been advantageous during the early radiation of fishes.

Fish Utilization of Great Lakes Coastal Wetlands

Correspondence analysis was used to partition fish species associated with the open water of each of the five Great Lakes and nine coastal wetlands for which data were available. Included in the analysis were 113 species in 25 families. Three species complexes were suggested: a Great Lakes taxocene (31 species); a transitional community which utilized open water, nearshore, and wetlands (35 species); and a wetlands taxocene, comprised of 47 species found to be closely associated with coastal wetlands. The wetland species split into two main groups: permanent residents (e.g., brown bullhead Ictalurus nebulosus, mudminnow Umbra lima, longnose gar Lepisosteus osseus) and migratory species. Migratory species included three subgroups: (1) those that spawned in the wetlands and then left (e.g., northern pike Esox lucius, common carp Cyprinus carpio, white sucker Catostomus commersoni, walleye Stizostedion vitreum), (2) those that used the wetlands as a nursery area (e.g., northern pike, gizzard shad Dorosoma cepedianum, spottail shiner Notropis hudsonius), and (3) those that migrated into the wetland from other wetlands or a Great Lake for shelter, spawning sites, or food; as part of the sustaining process of dispersal of young; or as part of wandering behavior (e.g., burbot Lota lota, rainbow smelt Osmerus mordax, rainbow trout Oncorhynchus mykiss). It was found that most remaining coastal wetlands are degraded or altered to some degree, and are dominated by a characteristic silt- and turbidity-tolerant fish fauna (e.g., common carp, gizzard shad, goldfish Carassius auratus, and brown bullhead). Nevertheless, even degraded wetlands still functioned as important fish habitat by exporting large quantities offish, first to avian, piscine, and mammalian food chains through predation, and second to the Great Lakes as young-of-the-year sport and forage fish. The research implies that a wetland must maintain a connection with a Great Lake to promote and enhance efficient fish utilization of the high productivity of marshes; that additional resilience is provided to species which spawn in wetlands since they can produce two cohorts (one in wetlands and one in the Great Lakes), and that fluctuating water levels are important in sustaining habitat diversity and productivity.

Experimental Verification of the Metacercarial Stage of Rhipidocotyle lepisostei (Trematoda: Bucephalidae) with Notes on the Natural Occurrence of Its Adult Stage in Gars in Texas and Virginia

Bucephalid metacercariae found encysted in the caudal fin rays of striped mullet (Mugil cephalus) were fed to bucephalid-free spotted gars (Lepisosteus oculatus) in the laboratory. Gravid specimens of Rhipidocotyle lepisostei were recovered from the intestinal tracts of 2 of 3 gars from 7 to 28 days later. Further attempts to complete the entire life cycle were unsuccessful. Natural infections of adult R. lepisostei were found in the type host, the alligator gar Lepisosteus spatula, from Galveston Bay, Texas, and in the long-nose gar, Lepisosteus osseus, from the York River, Virginia. This report confirms the identity of the metacercarial stage in the mullet as R. lepisostei and extends the known range of this parasite from the Louisiana and Texas area to the U.S. Atlantic coast.

Distribution of Upper and Middle Ohio River Fishes, 1973–1985: I. Associations with Water Quality and Ecological Variables

ABSTRACT More than 200,000 adult and juvenile fishes of 100 species were collected near five electric generating plants located in the upper and middle Ohio River during 1973 through 1985. Catches were dominated by Notropis atherinoides, Dorosoma cepedianum, Pimephales notatus, Ictalurus punctatus, Cyprinus carpio, Lepisosteus osseus, Lepomis macrochirus, Pomoxis annularis, Notropis blennius, and Aplodinotus grunniens. Twenty-nine species occurred with greater frequency in the upper Ohio River, whereas 17 species were found predominately in the middle Ohio River sampling areas. Classification of these species based upon mode of reproduction, habitat preference, and mode of feeding indicated a distinct prevalence of species typically associated with smaller, free-flowing streams at upper Ohio River sampling sites. Species typically found in large, slow-moving water bodies dominated at middle Ohio River sites. These fish distributional trends may be partially related to significant upper-middle Ohio River d...

The ultrastructure and innervation of the ear of the gar, Lepisosteus osseus.

The endorgans of the inner ear of the gar were examined using transmission and scanning electron microscopy as well as nerve staining. The ultrastructure of the sensory hair cells and supporting cells of the gar ear are similar to cells in other bony fishes, whereas there are significant differences between the gar and other bony fishes in the orientations patterns of the sensory hair cells on the saccular and lagenar sensory epithelia. The saccular sensory epithelium has two regions, a main region and a secondary region ventral to the main region. The ciliary bundles on the main region are divided into two groups, one oriented dorsally and the other ventrally. Furthermore, as a result of curvature of the saccular sensory epithelium, the dorsal and ventral ciliary bundles on the rostral portion of the epithelium are rotated ninety degrees and are thus oriented on the animal's rostro-caudal axis. Hair cells on the secondary region are generally oriented ventrally. The lagenar epithelium has three groups of sensory hair cells. The groups on the rostral and caudal ends of the macula are oriented dorsally, whereas the middle group is oriented ventrally. Hair cell orientations on the utricular epithelium and macula neglecta are similar to those in other bony fishes. Nerve fiber diameters can be divided into three size classes, 1-8 microns, 9-13 microns, and 14 microns or more, with the smallest size class containing the majority of fibers. The distribution of the various classes of fiber diameters is not the same in nerve branches to each of the end organs. Similarly, the ratio of hair cells to axons differs in each end organ. The highest hair cell to axon ratio is in the utricle (23:1) and the smallest is in the macula neglecta (7:1). The number of sensory hair cells far exceed the number of eighth nerve axons in all sensory epithelia.

Presence of fat droplets in the interrenal cells of the longnose gar.

Chondrichthyean interrenal cells contain a lot of fat droplets stainable with Sudan IV or Oil Red O, as in mammalian adrenocortical cells. However, the droplets are not detectable in the teleostean interrenal cells treated with these fat-soluble dyes. In the present study, six speci-mens of a holostean fish Lepisosteus osseus (longnose gar) were used and histological examinationwas made on the interrenal gland after fixing in 10% neutral formalin quid and stainlng with Oil Red O, in addition to Bouin's fluid fixation and H-E stain. From this examination, it was ascer-tained that the fat droplets are abundantly included in the interrenal cells of the longnose gar.From the viewpoint of fat droplet inclusion, therefore, the interrenal cells of this holostean fish are akin to those of cartilaginous fish, rather than the teleostean interrenal cells.

Ventilatory and Cardiac Reflex Responses to Hypoxia and NaCN in Lepisosteus osseus, an Air-breathing Fish

The hypoxic depression of gill ventilation, along with other ventilatory and cardiovascular responses to hypoxia, were studied in the bimodal breather, Lepisosteus osseus. Air-breathing frequency increased hyperbolically as water Po2 declined. The response of gill ventilation to changes in water Po2 was complex. Opercular pressure initially increased as Po2 fell, reaching maximal levels between 75 and 125 torr Po2. As the Po2 fell further, opercular pressure fell to about 50% of its maximal level. Heart rate rose as Po2 fell. Gill ventilation frequency did not change significantly with hypoxia. A 1/1 coupling between heart rate and gill ventilation was observed in four of nine fish in which heart rate was measured, during normoxia only. The Po2 in the dorsal aorta (DA) fell with hypoxia but did not change significantly in the ventral aorta (VA) at any level of aquatic hypoxia. External administration of NaCN had a large stimulatory effect on air-breathing frequency but did not significantly affect gill ventilation. Internal injections of NaCN into either the DA or VA produced a prolonged stimulation of gill ventilation and transiently stimulated air breathing, but the response to VA injections was much quicker. Heart rate was not significantly affected by NaCN. These data suggest that air breathing is initiated on stimulation of external chemoreceptors located in or near the gills, while gill ventilation is controlled by internal chemoreceptors. The depression of gill ventilation seen during hypoxia, contrasted to the exclusively stimulatory effects of the NaCN, further suggests that the internal chemoreceptors are positioned where they are able to sense the increased flow of oxygenated pulmonary blood during intense air breathing.

Chemoreflexive responses to hypoxia and NaCN in longnose gar: evidence for two chemoreceptor loci.

Interactions between internal and external O2 stimulus levels were assessed by measuring the ventilatory and cardiovascular responses to varying water (PWO2) and air bladder (PabO2) O2 levels and intravascular NaCN in anesthetized spontaneously ventilating Lepisosteus osseus. As PWO2 fell, air-breathing frequency (fab) increased. Buccal pressure amplitude (Pb) also increased as PWO2 fell from hyperoxia to normoxia, but hypoxic water depressed Pb. The PO2 in the ventral aorta (VA) fell as PabO2 fell, which stimulated fab and Pb when the gar was in normoxic or hyperoxic water. Thus gill ventilation and air breathing were normally controlled by both internal and external O2 levels, but aquatic hypoxia uniformly depressed gill ventilation regardless of changes in PabO2 levels. Heart rate and blood pressure were unaffected by these changes. NaCN stimulated hypoxic reflexes and bradycardia more quickly when given into the VA or conus than when given into the dorsal aorta. The animals appear to possess internal chemoreceptors that set the level of hypoxic drive and external chemoreceptors that inhibit gill ventilation and shift the ventilatory emphasis from water to air breathing.

Plasma Corticosteroid Stress Response of Fourteen Species of Warmwater Fish to Transportation

Plasma corticosteroid concentrations were measured in 14 species of fish immediately after they were electrofished from reservoirs on the Alabama River and after they had been transported for 2 h. There was no corticosteroid response in spotted gars Lepisosteus oculatus. Bowfins Amia calva, longnose gars Lepisosteus osseus, and freshwater drums Aplodinotus grunniens had only small corticosteroid increases (14–39 ng/mL) during transportation. Corticosteroids increased by intermediate amounts (59–184 ng/mL) during transportation in blue catfish Ictalurus furcatus, paddlefish Polyodon spathula, largemouth bass Micropterus salmoides, channel catfish Ictalurus punctatus, river carpsuckers Carpiodes carpio, white bass Morone chrysops, striped bass Morone saxatilis, and crappies Pomoxis sp. The greatest increases were 223 ng/mL in gizzard shad Dorosoma cepedianum and 286 ng/mL in common carp Cyprinus carpio. Spotted and longnose gars, largemouth bass, and common carp also were held in tanks for about 2 months at 21°C and then stressed by confinement in a dip net for 30 min. The confinement caused significant increases (P < 0.01) of plasma corticosteroid concentration in all four species. Dip-net confinement appears to be a useful method for comparing corticosteroid responses among species of warmwater fish.

Absence of juxtaglomerular cells in the kidneys of freshwater stingrays and primitive bony fishes.

The juxtaglomerular (JG) cells in the mammalian kidneys are known to secrete a kidney hormone called renin. JG cells are present also in the kidneys of holocephalian and teleostean fishes. However, the kidneys of cyclostomes and elasmobranchs are lacking in these cells. The present histolgical investigations using Bowie's stain were performed to clarify whether or not JG cells are present in the kidneys of South American freshwater stingrays Potamotrygon spp., the sterlet Acipenser ruthnus, the bester (intergeneric hybri of A.ruthenus ?? ×Huso huso ?? ), and the longnose gar Lepisosteus osseus. However, JG cells were not detectable in the kidneys of any these fishes lnvestigated.

Cellular localization of pepsinogens by immunofluorescence in the gastrointestinal tracts from four species of fish

Using antiserum against human pepsinogen I and pepsinogen II, we investigated the cellular localization of pepsinogens by immunofluorescence in the stomach and proximal intestine of four species offish (Ambloplites rupestris, Lepisosteus osseus, Lepomis gibbosus, and Perca flavescens). In each species, only the oxynticopeptic cells in the corpus of the stomach stained with antiserum against pepsinogens I and II. Fluorescent cells were absent in the surface epithelium of both the stomach and small intestine. The results indicate that the oxynticopeptic cells are the source of pepsinogen in fish and suggest that these cells contain two immunochemically distinct pepsinogens that share antigenic determinants with human pepsinogens I and II.

Use of Oligohaline Marshes by Fishes and Macrofaunal Crustaceans in North Carolina

Fishes and invertebrate macrofauna (nekton) inhabiting three low salinity, intertidal rivulets were sampled biweekly from July 1981 through June 1982. Twenty-nine species of fishes (24,335 individuals, 9.671 kg wet weight) representing 19 families and four species of invertebrates (6,812 individuals, 4.708 kg wet weight) were collected. The most abundant species were spot (Leiostomus xanthurus), grass shrimp (Palaemonetes pugio), bay anchovy (Anchoa mitchilli) and Atlantic menhaden (Brevoortia tyrannus). Only a few large predacious fish (e.g., largemouth bass,Micropterus salmoides) were collected in the rivulets although largemouth bass and longnose gar (Lepisosteus osseus) were abundant in a nearby permanently flooded area. The number of species was greatest during the warmer months and lowest, during the winter. There were three seasonal peaks of numerical abundance: spring peak attributed to the influx of junvenile spot Atlantic menhaden, Atlantic croaker (Micropogonias undulatus), and southern, flounder (Paralichthys lethostigma); summer peak due to grass shrimp; and fall peak to bay anchovy and grass shrimp. The occurence of these species was not correlated with salinity in the study area. Average densities of spot and Atlantic menhaden in the oligohaline rivulets at the peak of juvenile recruitment were similar to the average densities of these species reported for salt marshes. The results suggest that oligohaline estuarine areas contain important nursery habitat for some euryhaline species.

Gastrin immunoreactive cells in the gastrointestinal tracts from four species of fish

Using antiserum against human gastrin, we have demonstrated cross reactivity in endocrine cells from the gastrointestinal tracts of four fish species (Ambloplites rupestris, Lepisosteus osseus, Lepomis gibbosus, and Percaflavescens). In the corporic stomach, positive cells were found in the surface and glandular epithelium and subepithelial connective tissue of A. rupestris but only the surface and glandular epithelium of L. gibbosus whereas no immunoreactive cells were found in either L. osseus or P. flavescens. In the pylorus of A. rupestris and P. flavescens, immunoreactive cells were few in number in the surface epithelium but numerous in the underlying lamina propria. In the pylorus of L. osseus and L. gibbosus, no positive cells were seen in the lamina propria but in the former a few were present in the surface epithelium. In intestine of A. rupestris, L. gibbosus, and P. flavescens immunoreactive cells were present in both surface epithelium and subepithelial connective tissue. Possible explanations for the notable species differences are discussed.

Mitogenic effect of myelinated vs unmyelinated garfish nerve extracts

Mitogenic activities in crude extracts of unmyelinated olfactory nerves and myelinated trigeminal nerves of the garfish Lepisosteus osseus were compared. Extracts of each nerve type were added in a range of protein concentrations to serum-starved, subconfluent cultures of BALB/c 3T3 cells. At low protein concentrations (50–250 μg/ml) myelinated nerve extracts produced more [ 3H]thymidine incorporation in the cultured cells than unmyelinated nerve extracts, while at higher concentrations (500–1000 μg/ml), the latter caused as much DNA synthesis as the myelinated nerve extracts, surpassing them at the highest concentrations tested. The results suggest that both axonal and myelin components contribute to the growth-promoting activity in nerve tissue.

The monoamine-containing neurons in the brain of the garfish, Lepisosteus osseus

The morphological organization of monoamine (MA)-containing neurons in the brain of the longnose gar ( Lepisosteus osseus) was studied by means of fluorescence histochemical methods. In this species, one of the few living representatives of the holostean group of actinopterygian fishes, by far the largest number of MA cells is found within the preoptico-hypothalamic complex. Multitudinous small-sized MA cells, with a short club-like process protruding into the third ventricle, are present along the ependymal wall of the lateral and posterior hypothalamic recesses. This population of CSF-contacting MA cells, comprising both catecholamine (CA) and serotonin (5-HT) type cells, gives rise to numerous efferent fibers, some of which proceed rostrally toward the telencephalon while others course dorsally to reach the midbrain tegmentum and optic tectum. Many fibers, however, arborize directly within the hypothalamus, particularly around blood vessels where they form patches of highly fluorescent material. Small CA cells are also scattered along the preoptic recess wall. They do not directly contact the CSF but also appear to contribute to the CA innervation of telencephalon. At brain stem levels, a few CA cells are scattered at the base of the rostral midbrain, in the isthmal tegmentum, and in the central and dorsal (vagal lobe) portions of the medulla. Some CSF-contacting CA cells are also present around the central canal at upper spinal cord levels. One of the most striking features of the MA systems in Lepisosteus is the remarkable development of the 5-HT neuronal network. A prominent 5-HT cell column extends rostrocaudally in the raphe region from the caudal midbrain to upper spinal cord levels. In the caudal midbrain and isthmus, the 5-HT cells also invade the lateral tegmemtum and profusely innervate various brain stem structures as well as large portions of telencephalon, particularly the dorsal nucleus of area ventralis (Vd). The CA innervation of telencephalon is relatively weak, except in the olfactory bulb where numerous CA varicosities were found. These findings in Lepisosteus suggest that the pattern of MA system organization in the holostean brain is far more similar to that seen in primitive vertebrates, such as cyclostomes—where the 5-HT systems are highly elaborated relative to the CA systems—than it is to the pattern in more advanced fishes such as teleosts.

Localization of neurons afferent to the optic tectum in longnose gars.

Afferent pathways to the optic tectum in the longnose gar were determined by unilateral tectal injections of HRP. Retrogradely labeled cells were observed in the ipsilateral caudal portion of the rostral entopeduncular nucleus and bilaterally in the rostral half of the lateral zone of area dorsalis of the telencephalon. The following diencephalic cell groups were also labeled following tectal injections: the ipsilateral anterior, ventrolateral, and ventromedial thalamic nuclei, the periventricular pretectal nucleus, and the central pretectal nucleus (bilaterally); the ventromedial thalamic and central pretectal nuclei revealed the largest number of labeled cells. At midbrain levels, retrogradely labeled cells were seen in the ipsilateral torus longitudinalis, nucleus isthmi, and accessory optic nucleus; cells were labeled bilaterally in the torus semicircularis and a rostral tegmental nucleus. Only a few cells were labeled in the contralateral optic tectum, suggesting that few of the fibers of the intertectal commissure are actually commissural to the tectum. At hindbrain levels, retrogradely labeled cells were seen bilaterally in the locus coeruleus, the superior, medial, and inferior reticular formations, the eurydendroid cells of the cerebellum, and the nucleus of the descending trigeminal tract; the contralateral dorsal funicular nucleus also exhibited labeling. Clearly, the tectum in gars receives a substantial number of nonvisual afferents from all major brain areas, most of which have been reported in other vertebrates. The functional significance of these afferent sources and their probable homologues in other vertebrate groups are discussed.

Serum esterase variation and characterization in populations of the longnose garpike, Lepisosteus osseus

1. 1. Serum esterase variation in populations of Lepisosteus osseus, sampled from North and South Carolina, was investigated employing acrylamide gel electrophoresis. 2. 2. North Carolina populations were found to be monomorphic with respect to serum esterase activity. 3. 3. All South Carolina populations proved to be polymorphic; each individual sampled from these populations possessed one of two phenotypic profiles. 4. 4. Serum esterases were characterized utilizing eserine sulfate, diisopropylfluorophosphate, and sulfhydryl-group inhibitors.

Projections of the optic tectum in the longnose gar, lepisosteus osseus

Efferent projections of the optic tectum were studied with the anterograde degeneration method in the longnose gar. Ascending projections were found bilaterally to 3 pretectal nuclei — the superficial pretectal nucleus, nucleus pretectalis centralis and nucleus pretectalis profundus — and to a number of targets which lie further rostrally — the central posterior nucleus, dorsal posterior nucleus, accessory optic nucleus, nucleus ventralis lateralis, nucleus of the ventral optic tract, rostral part of the preglomerular complex, suprachiasmatic nucleus, anterior thalamic nucleus, nucleus ventralis medialis, nucleus intermedius, nucleus prethalamicus and rostral entopeduncular nucleus. Projections of the tectum reach the contralateral side via the supraoptic decussation and are less dense contralaterally than ipsilaterally. Descending projections resulting from tectal lesions include: (1) a tectal commissural pathway to the core of the torus longitudinalis bilaterally and the contralateral tectum and torus semicircularis; and (2) a pathway leaving the tectum laterally from which fibers terminate in the ipsilateral torus semicircularis, an area lateral to the nucleus of the medial longitudinal fasciculus, lateral tegmental nucleus, nucleus lateralis valvulae, nucleus isthmi and the reticular formation. A component of this bundle decussates at the level of the lateral tegmental nucleus to project to the contralateral reticular formation. On the basis of comparisons of these findings with the pattern of retinal projections in gars and other data, it is argued that the nuclei previously called the lateral geniculate and rotundus in fish are not the homologues of the nuclei of those names in land vertebrates but are rather pretectal cell groups. The overall organization of both retinal and tectal projections in gars is strikingly similar to that in land vertebrates; at present, the best candidate for a rotundal homologue is the dorsal posterior nucleus.

Fine structure of the garfish spermatozoon

The spermatozoon of the holostean fish species gar (Lepisosteus osseus) agrees in its main features with those of primitive teleosts. Thus, it lacks an acrosome and has a short midpiece with a ring-shaped mitochondrion. There are two centrioles and both have end regions with doublets of a characteristic form. The proximal centriole is joined to a fibrous body, which sends an extension to a posterior central fossa of the nucleus. The sperm tail has two lateral sidefins which are roughly in the plane of the two central microtubules. The close correspondence between the teleost and the holostean spermatozoa is in agreement with the proposed close affinity between these two fish groups. A survey shows that other fish groups have other types of spermatozoa.