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Call number: LD2668 .T4 1929 S31

Means of reducing the quantity of water required for the washing unit operation in surimi processing were evaluated. The yield of flesh mechanically dewatered with a screw press and the degree of reduction in trimethylamine oxide (TMAO) content were used as indices of washing efficiency. Variations in water:minced flesh ratio, multiple exchanges and washing conditions near the mean isoelectric point of flesh proteins were techniques evaluated to optimize the yield and quality of washed minced flesh. Single exchanges in potable water produced solids and protein recoveries superior to those observed for multiple exchanges utilizing the same total amount of water. A single exchange of a water:minced flesh ratio of 3.0 produced the highest recoveries (73.32 and 74.07 % of flesh solids and protein, respectively) with the composition characteristics desired. Multiple potable water exchanges (water:minced flesh ratio = 1.0/exchange) at equal total water volume produced desired composition characteristics, but pressed flesh yield was reduced (65.9 and 68.5 % of flesh solids and protein, respectively). Washing (water:minced flesh = 1.0) under acidic conditions near the isoelectric point (pH 4.9-5.3) of the minced flesh protein followed by a potable water wash (water:minced flesh = 1.0) produced recoveries (73.02 and 76.20 % of flesh solids and protein, respectively) superior or equal to all of the wash regimes of equal total water volume. These recoveries were observed even with considerable loss during screening between exchanges and at a water usage 66 % of the single exchange (water:minced flesh ratio = 3.0) of potable water. The moisture content of pressed flesh was increased by both the total potable water:minced flesh ratio and by the number of exchanges to which minced flesh was exposed. Moisture contents mediated by the number of exchanges were a function of water volume and exposure time. Washing conducted in an acidic water:minced flesh mixture at pH 4.9-5.3 (near the mean isoelectric point of flesh proteins) produced pressed flesh with a moisture content 10.09-15.09 percentage points lower than minced flesh wash in an identical (total water:minced flesh ratio; means of separation between exchanges) potable water regime. Washing under acidic conditions produced the most efficient reductions in TMA0 and lipid content (91.4 and 31.1 % of flesh TMA0 and lipid, respectively). Superior reductions were accomplished through pH conditions favoring the extraction of amines and by the greater pressures produced during screw pressing by the altered physical characteristics of the flesh. Pressing between multiple potable water exchanges also showed better reductions than single exchanges involving only one pressing operation. "Folding test" evaluation of heat-set gels (kamaboko) produced from a standard surimi formulation (containing 4 % each of the cryoprotectants sucrose and sorbitol and 0.5 % condensed phosphate) with the addition of 5 % each of potato starch and dried egg white revealed a difference between potable water and acid-washed flesh. Potable water-washed flesh (one exchange; water:minced flesh ratio = 3.0) graded SA (the highest possible grade for the "folding test used by Japanese processors to test the gel strength of surimi". An A-B grade (second and third grade on a five point scale) was assigned gels produced from acid washed flesh. Texture profile analysis of gels revealed acid washed flesh to yield significantly lower gel elasticity (P [greater than or equal to] .007) and cohesiveness (P [greater than or equal to] .0223) than those prepared from potable water washed flesh. The gels were equal in hardness (P [greater than or equal to] .05). The two washing regimes produced gels with comparable (P [greater than or equal to] .05) expressible water contents. Low potable water (a single exchange; waterrminced flesh ratio = 3.0) and acidic (two exchanges; water:minced flesh ratio = 1.0/exchange; exchanges = first pH 5.0-5.3, second potable water) washing regimes improved surimi yield by 26 % and 34 %, respectively, over yields reported for the conventional shore-based processing operations. This was accomplished at water use levels conservatively estimated to be 20 % of those reported for these processes. / Graduation date: 1987

No description available.

Selected aspects of the life history of desert suckers were examined in four southeastern Arizona streams. Diet, age class structure, reproduction, and habitat use were analyzed from field data obtained from April 1987 through October 1988. Adults fed primarily on plant matter, while fry fed almost exclusively on diatoms. Aging of suckers by scales was not possible and length frequencies were too evenly distributed to determine age class structure. In 1988, ovary and teste development occurred from late January through April, with spawning commencing in May. Suckers primarily used pools with high water flow and significant (∼80%) cover formed by tree limbs, branches, leaves, and other debris. Deterioration or loss of suitable habitat is reducing the range of the sucker due to reductions in and manipulations of surface waters.

The digenean Stephanochasmus baccatus (Nicoll, 1907) is a parasite found in marine flatfish which are of importance to the mariculture industry in Scotland. In the area of study, Loch Ewe, on the North-west coast of Scotland, the first intermediate hosts are the gastropods Buccinum undatum (L. ) and Neptunea antiqua (L. ). Several species of teleost fish of the Order Heterosomata act as second intermediate host and the definitive host is Eutrigla gurnardus (L. ) or Myoxocephalus scorpius (L. ). Aspects of the host/parasite relationships at all the host levels were investigated. Samples of B. undatum and N. antiqua were collected from May to September and the incidence of the natural infections of the major digenean species were recorded. In some samples, height, weight and copulatory organ length were measured with a view to finding an indicator of parasitism. The histopathology of S. baccatus in the molluscan host was described and seasonal changes discussed in relation to observed variations in the infectivity of cercariae to second intermediate hosts. Groups of 1+ fish were experimentally infected with cercariae at intervals from May to September when no more S. baccatus infections were found in the molluscs. Differences in the infectivity of the cercariae during these months were demonstrated. The pattern of glycogen deposition in both the molluscan digestive gland-and the intra-molluscan larvae were studied in an attempt to explain the loss of infectivity in cercariae in July and August. A. reduction in infectivity of cercariae after ageing was demonstrated experimentally by infecting fish with cercariae which were freshly dissected out and with cercariae kept for 10 hours at 12°C. This loss of infectivity was correlated with loss of glycogen from cercarial tails. A variety of I-group intermediate host species were infected experimentally and the distribution of cysts in the body, fins, skin and muscle were compared with the turbot, Scophthalmus maximus (L. ) and the plaice, Pleuronectes lap tessa L. These were shown to differ significantly. Four species of intermediate host which are of culturable significance, S. maximus, P. platessa, the common. dab, Limanda limanda (L. ) and the Dover sole, Solea solea (L. ) were experimentally infected and the tissue responses to invasion and encystment of S. baccatus were examined sequentially. The inflammatory response and metacercarial growth in each species of fish were found to differ in some important aspects which affected the subsequent viability in the definitive host. The viability of metacercariae from P. platessa and S. maximus were tested by controlled infection of the definitive host M. scorpius. A number of wild caught definitive hosts were examined for natural infections. An attempt gras made to describe the seasonal cycle of events in the life history of S. baccatus based on the information from this and other studies. The relative significance of different host species in different geographic locations was discussed.

Sanguinicola inermis Plehn, 1905, a recently introduced fish pathogen in Britain, has caused considerable damage to the carp industry. Two severely affected fish farms in England were included in the study. The incidence of fish infection for both farms was high, being 74-84% in 0+ and 1+ carp. Studies were made on the infection process and details of route of entry, migration and maturation of the worm are presented. An apharyngeate, furcocercous, lophocercous cercaria which develops in the snail Lymnaea (Radix) peregra (Mü11) was shown experimentally to develop into an adult Sanguinicola inermis. Maximum penetration of cercaria was achieved within 30 minutes and fins appeared to be the preferred site. Large numbers of worms were found to remain in the skin after penetration where they continued to develop to maturity, a previously unreported feature of S. inermis infection. The greatest migration to preferred loci occurred at 60 days post infection immediately prior to egg production. The migratory route used was found to be the loose connective tissue as well as the circulatory system. The distribution of mature worms in major blood vessels changed with season. Light microscopical studies were made on the morphology of specimens collected from the two farms and these were identified as S. inermis. Scanning electron microscopy of the surface topography and transmission electron microscopy revealed details of the tegument and provided evidence for the absence of spines. The major developmental features of the worm are described. A marked increase in size occurred up to 36 hours post penetration. Subsequent growth was slower. Egg production by mature worms began 10 weeks post infection at 15°C. Distribution and development of eggs in tissues is described. Egg production continued throughout the year with peaks during the summer months despite the constant environmental conditions. The growth rate of 0+ fry was studied over a period of 16 weeks and heavily infected fish showed stunted growth and poor Specific Growth Rates, Protein Efficiency Ratios and Food Conversion Ratios. Haematological studies showed that infected fish suffered from hypochromic macrocytic anaemia with leucocytosis and an increased Erkhrocyte Sedimentation Rate. Three different phases of infection were recognized. During phase I, the invasive stage, mortality may occur if infection levels are extremely high, but lightly infected fish present as clinically normal. Phase II was found to be the most critical phase since the majority of fish (over 90%) died at this stage. Histopathology revealed the progress of the infection from cercarial invasion to worm migration, maturation, egg production and miracidial hatching. Pathological changes were observed in the skin in phase I. In phase II, the heart, gills and kidneys were severely affected by both mature worms and developmental stages. The infection reached a chronic stage during phase III evidenced by a granulomatous tissue reaction largely in response to residual eggs in tissues. An attempt was made to integrate the phases of infection, development of the worm and pathogenesis in order to elucidate the host-parasite relationships.

Pacific herring, Clupea harengus pallasi, possesses a pheromone in the milt and testes that triggers spawning behaviour in reproductively mature individuals of both sexes, and plays a role in synchronizing the school spawning that is distinctive of this species. The pheromone was found to be effective as a transient olfactory stimulus in eliciting a behavioural response that varied in the degree of expression and time course. Stimulus strength was found to influence the time course of the response, whereas differences in maturity, evident through examination of plasma levels of steroids, were correlated with a propensity to respond to the pheromone. Input from factors other than the spawning pheromone appear to be needed to elicit prolonged spawning; some of these factors also act through olfaction. Immediate effects of stress were not found to influence the response to the spawning pheromone. Plasma levels of reproductive steroids of herring during the spawning season were measured with radioimmunoassays. Peak levels of 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) were found to coincide with final maturation in females and the initiation of milt production in males, suggesting that this steroid is the maturation-inducing steroid of this species. Other features found to be distinctive of the reproductive physiology of the herring included low plasma levels of the unconjugated maturation-inducing steroid, high levels of 17α-progesterone (17-P) and 3α,17α-dihydroxy-5β-pregnan-20-one (3α,17-P-5β), and high levels of glucuronated steroids. Structural investigation of the pheromone with liquid chromatography/ mass spectrometry showed that it consists of at least two components which do not elicit a behavioural response individually. One of these compounds is sulphated 17,20β-P. The structure of proteinaceous hormones involved in controlling reproduction of the herring was also investigated. It was shown that this species possesses three forms of gonadotropin-releasing hormone (GnRH) in the brain, one with a structure that has not been reported before. These results indicate that the presence of three GnRH forms is a primitive, rather than derived, condition in the teleosts. The structure of the (β-subunit of gonadotropin II (GtH ll-β) of herring was also deduced by isolation of a cDNA for this molecule. The structure of the herring GtH ll-β was found to be quite different from other teleost molecules of this kind, and a phylogenetic analysis of known GtH ll-β structures suggests that the β-subunit of both mammalian gonadotropins may be most closely related to the β-subunit of teleost GtH-l. / Graduate

In addition to intensity and colour, the retinas of many invertebrates are capable of light detection based on its linear polarization (Wehner, 1983). The detection mechanism permitting this capability is based on the intrinsic dichroism of chromophores oriented along rhabdomeric microvilli. In vertebrates, however, except for anchovies (Fineran & Nicol, 1978), such axial dichroism is absent rendering vertebrate outer segments insensitive to the polarization of axially incident light. Nonetheless, there is evidence for polarization sensitivity in a few species of fish (goldfish, rainbow trout and sunfish). But the findings for goldfish and rainbow trout appear contradictory to those for the green sunfish (Parkyn & Hawryshyn, 1993), and a detection mechanism that could explain polarization sensitivity for lower vertebrates in general is unknown. This thesis was undertaken to try to solve some of these unknowns by investigating: 1) the neural polarization signal, at the level of the optic nerve, in fish species from four groups with distinct retinal cone mosaics (rainbow trout, green and pumpkinseed sunfishes, common white sucker, and northern anchovy), 2) the ultrastructure and light transmission properties of different cone types (single, twin and double cones) , and 3) the characteristics of the underwater polarized light field that could permit the observed laboratory behaviours in nature. I measured compound action potential (CAP) responses from the optic nerve of live anaesthetized fish to evaluate the possibility that a fish could detect the orientation of the electric field of linearly polarized light (mathematically-designated as the E-vector) . Results from these studies showed that rainbow trout and the northern anchovy were polarization-sensitive, but both species of sunfish and the common white sucker were not. In addition, CAP measurements conducted with rainbow trout exposed to light stimuli of varying polarization percentages showed, in conjunction with underwater polarized light measurements, that the use of polarized light in this animal was restricted to crepuscular time periods. To try to understand why some fish species were polarization-sensitive and others were not, I carried out microscopy studies of retinal cones. Optical measurements of transmitted polarized light through the length of cones showed: 1) small cone birefringence (retardance < 2nm) , and 2) preferential transmission of polarized light that was parallel to the partition dividing twin and double cones (single cones were isotropic). In addition, histological studies showed that the partition in trout double cones was tilted with respect to the vertical while that of twin cones in sunfish was straight. We envisioned that the higher index of refraction of the partition with respect to the surrounding cell cytoplasm would make it behave as a mirror, reflecting and polarizing incident light. A large optical model was built to test this idea consisting of two photodiodes evenly spaced on either side of a cover-slip "partition" upon which physiologically-relevant illumination was incident. Measurements using this model and theoretical calculations with refractive indices approaching those expected for double cone partitions and cytoplasm (Sidman, 1957) were consistent with the optical results obtained in situ. Thus the tilt in the partition of trout double cones relayed different amounts of light to each outer segment depending on the polarization of incident light, whereas a straight partition, as in sunfish, did not. Comparison of signals from orthogonally-arranged double cones and single cones in the centro-temporal retina of trout thus became the basis for a model neural network that could reproduce all the polarization sensitivity results known to date. To support the idea that an ordered (e.g. orthogonal) arrangement of double cones was a necessity for polarization detection, I showed that the common white sucker, a fish with double cones, had these arranged randomly in the centro-temporal retina (hence its lack of polarization sensitivity). Finally, the northern anchovy exhibited unique cones with lipid lamellae parallel to their lengths, forming a dichroic system for polarization detection somewhat analogous to that of cephalopods and decapod crustaceans. / Graduate

Ph.D. (Zoology) / Please refer to full text to view abstract