Peter A. Cook

The role of bacteria in the digestion of seaweed by the abalone Haliotis midae.

Abstract The polysaccharolytic enzymes of the abalone Haliotis midae and its resident gut bacteria were investigated. Bacteria isolated from the abalone gut were able to degrade the polysaccharides laminarin, carboxymethylcellulose (CMC), alginate, agarose and carrageenan. Detection of alginate lyase, CMCase, laminarinase, agarase and carrageenase in the hepatopancreas, which was devoid of bacteria, indicated that H. midae produces a range of polysaccharases. The endogenous polysaccharases of abalone fed either Ecklonia maxima or Gracilaria verrucosa varied in response to diet. It is proposed that bacteria resident in the digestive system of H. midae assist in the digestion of alginate, laminarin, agarose, carrageenan and cellulose.

Congruent patterns of genetic variation in a burrowing freshwater crab revealed by allozymes and mt DNA sequence analysis

Five populations of the burrowing freshwater crab, Potamonautes calcaratus representing a total of 100 specimens, were collected from the Kruger National Park, South Africa. The population genetic structure of this species was investigated using both nuclear genetic markers (allozymes), and direct sequencing of a 610 base pair fragment the cytochrome oxidase 1(CO 1) subunit of the mitochondrial DNA. Electrophoresis of 21 allozyme loci revealed that moderate levels of genetic differentiation (F(ST) = 0.12) was present among populations. Sequence data for 20 individuals revealed the presence of ten haplotypes, the distribution of which showed no geographic structuring. The ΦCT of 0.43 corroborates a moderate degree of genetic structuring. The nucleotide diversity (π) was low and ranged from 0.00 to 0.007. Sequence divergence amongst populations ranged from 0.49% to 1.47%. Both genetic markers revealed moderate population structuring, supporting the conclusion that populations share a common recent ancestry, with moderate levels of recent gene flow. These results provide evidence that allozyme and sequencing data may be congruent and that these independent markers can detect similar patterns of genetic differentiation. Results are discussed in light of contemporary factors that have been likely in sculpting the genetic structure.

Induction of triploidy in the South African abalone using cytochalasin B

An investigation into triploidy induction in the South African abalone, Haliotis midae, was conducted. It was found that 0.5 mg l–1 of Cytochalasin B (CB) in seawater induced triploidy when administered to coincide with the normal timing of the release of either polar body one (PB1) or two (PB2). This concentration of CB produced 70.9% triploid induction in the PB2 treatment and 48.4% induction at PB1. Significant numbers of tetraploid larvae were found in the PB1 treatment. These resulted from the presence of excess sperm (polyspermy) but only when CB was present. Although larval survival after triploid induction was lower than the control animals, it was considered high enough for use in commercial hatcheries.

Development of a Monoclonal Antibody Detection Assay for Species-Specific Identification of Abalone

Species identification based on biochemical and molecular techniques has a broad range of applications. These include compliance enforcement, the management and conservation of marine organisms, and commercial quality control. Abalone poaching worldwide and illegal trade in abalone products have increased mainly because of the attractive prices obtained and caused a sharp decline in stocks. Alleged poachers have been acquitted because of lack of evidence to correctly identify species. Therefore, a robust method is required that would identify tissue of abalone origin to species level. The aim of this study was to develop immunologic techniques, using monoclonal and polyclonal antibodies, to identify 10 different abalone species and subspecies from South Africa, the United States, Australia, and Japan. The combination of 3 developed monoclonal antibodies to South African abalone (Haliotis midae) enabled differentiation between most of the 10 species including the subspecies H. diversicolor supertexta and H. diversicolor diversicolor. In a novel approach, using antibodies of patients with allergy to abalone, the differentiation of additional subspecies, H. discus discus and H. discus hannai, was possible. A field-based immunoassay was developed to identify confiscated tissue of abalone origin.

The influence of temperature variations and thermal pollution on various aspects of the biology of the prawn Palaemon pacificus (Stimpson)

Abstract The influence of different temperatures 10, 15, 20, and 25°C on the food consumption, growth, moulting rate, and respiration of Palaemon pacificus (Stimpson) from Langebaan Lagoon, west coast of South Africa, was studied under laboratory conditions. At 10°C mortality was high so that food consumption and moulting rate could not be determined as these were very low. At higher temperatures, food consumption was found to be temperature dependent, the rate at 25°C being twice that at 15°C. Growth rate was most favourable at 25°C. At 28°C growth rate was lower than at 20°C but higher than at 15°C. The intermoult period was 17 days at 15°C, and 11 and 10 days at 20, and 25°C, respectively. It seems that from an energetic point of view, 25°C is the most favourable temperature for P. pacificus . Several indices of growth efficiency at different temperatures are presented. The appearance of this prawn in South African west coast localities such as Langebaan during the summer and its disappearance during winter, can be explained by its temperature preferences. The possibility that thermal pollution from a nuclear power station may be beneficial to this prawn, is discussed.

A possible rôle of α-amylase isoenzymes from the style of the mussel Choromytilus meridionalis (Krauss) following thermal acclimation

Separation of the proteins comprising the crystalline style of the mussel Choromytilus meridionalis (Krauss) by anion exchange chromatography shows that there are three fractions displaying α-amylase activity in both warm- and cold-acclimated mussels. These fractions correspond with one or more proteins which remain unbound to the resin (Peak I), a bound fraction which is eluted at 100–150 mM NaCl (Peak II) and a further fraction which is eluted at 200–250 mM NaCl (Peak III) but which may represent contamination carried over from Peak II. Cold-acclimation to 8°C results in the appearance of a fourth α-amylase fraction (Peak IV) which is eluted from the column between 300–400 mM NaCl. Thermal acclimation also results in changes in the activities of Fractions I–IV such that a specific activity of 0.47 mg glucose liberated per A280 unit of protein per 8 min incubation at 8°C in Fraction IV is increased nearly 10-fold to a specific rate of 4.10 in protein Fraction I following acclimation to 22°C. It is suggested that an increased of digestive activity may be of equal importance to a suppression of metabolic costs in the maintenance of energy flow into growth and reproduction in ectothermic organisms which experience an increase of environmental temperature, especially in bivalves such as C. meridionalis which do not show a compensatory increase in filtration rate.

An assessment of the use of low-level aerobic swimming in promoting recovery from handling stress in rainbow trout

Transportat ion and handling may stress fish (Barton and Peter, 1982; Barton et al., 1986), leading to the undesirable consequence that fish are unloaded from transport units in a stressed condition (Barton et aL, 1980; Specker and Schreck, 1980). Characteristically, such stress results in alterations to both behaviour (Sigismondi and Weber, 1988) and physiological state (Mazeaud et al., 1977), which may give rise to t ransport mortality (Wedemeyer, 1976). Consequently, economic and ethical considerations have prompted numerous studies into methods that reduce transport stress (e.g. Wedemeyer, 1972; Barton and Peter, 1982; Carmichael et aL, 1984; Robertson et aL, 1988) and the manipulation of the t ransport water osmolality, cold water transport , and anaesthetic t reatment prior to transport , have shown some success. All of the aforementioned methods of fish t ransport reduce the magnitude of t ransport stress, but little work has focused on promoting stress recovery. Since the initial loading of fish into the t ransport container is the most stressful component of t ransport (Miles et al., 1974; Specker and Schreck, 1980), we were curious to know if the recovery process could be initiated during t ransport itself, leading to the arrival of fish in a less stressed condition. It was examined whether low-level aerobic swimming following handling stress would hasten stress recovery in rainbow trout (Oncorhynchus mykiss) over that of unswum fish. Freshwater adapted rainbow trout (225-322 mm, n = 45) were maintained and acclimated at 15°C in 2000 1 circular tanks, under a 12:12h light:dark cycle. Prior to each experiment, individual fish were removed from the holding tanks and subjected to between 18 and 24h of isolation and starvation in dark, aerated 100 1 plastic containers. Individual trout were subsequently removed from the isolation containers by dipnet, and subjected to 3.0 min of air exposure entailing 2.5 min of struggling in the dipnet, and a further 0.5 min holding the fish on a measuring board for measurement. Trout were then transferred to the swim chamber

Implications for the assessment of crystalline style activity in bivalves when using the Bernfeld and Nelson-Somogyi assays for reducing sugars

Abstract The crystalline style enzymes of Choromytilus meridionalis Krauss and other bivalves include amylase, laminarinase and cellulase which are potentially capable of liberating reducing sugars from a wide variety of structural carbohydrates. However, although colorimetric analyses of reducing sugars by the Bernfeld and Nelson-Somogyi assays give qualitative agreement, during quantitative assays using glucose for calibration purposes, there is a two to seven-fold discrepancy between the two methods, depending on the enzyme and substrate reagents used. The Bernfeld assay yields the higher reducing sugar estimate, although the Nelson-Somogyi assay is some eight times more sensitive. It seems likely that the quantitative discrepancy between the two methods can be accounted for by variability in the colour response to different end products. However, when the appropriate calibration standard is used, the two methods are in close agreement. Since these two reducing sugar assays have been previously used with an inappropriate standard (glucose) to make quantitative estimates of reducing sugar release, in an effort to calculate the energetic gain from crystalline style activity, it seems likely that such energy balance studies may be in error and these have been reevaluated.

Sex determination of live Galjoen (Coracinus capensis Cuvier) using a biochemical technique.

Abstract A method to determine the sex of adult galjoen by biochemical analysis of a blood sample is described. The test measures the amount of yolk protein (vitellogenin) present by determining the levels of alkali-labile protein-linked phosphorus in the blood plasma. Vitellogenic females show values averaging 20 μg protein phosphorus per ml plasma, whilst males and non-vitellogenic females show levels normally less than 1 μg and not exceeding 5 μg/ml. This method allows most females to be positively identified several months prior to, and during, the spawning season.