Biomass accumulation and shading effects of epiphytes on leaves of the seagrass, Heterozostera tasmanica, in Victoria,Australia

A method is described for estimating the rate of accumulation of epiphyte biomass on leaves of the seagrass, Heterozostera tasmanica (Martens ex Aschers.) den Hartog and for estimating the effect of epiphyte biomass on photosynthesis of the seagrass. Epiphyte biomass was determined by comparison of the weight per unit area of epiphyte-covered and epiphyte-free leaf blades. Epiphyte weight increased as age of the seagrass leaves increased. Linear regression on epiphyte biomass vs. leaf age estimated the rate of biomass accumulation. Rates varied from 5.7 to 104 μg epiphyte dry weight per cm² of leaf surface per day at three sites in Western Port and Port Phillip Bay, Victoria. Rates of accumulation of epiphyte biomass were generally higher during December through March (summer) than in May (autumn), August (winter) or October (Spring). Light attenuation by epiphytes increase linearly with biomass. The rate of biomass accumulation of epiphytes was compared with leaf growth rate, ambient photon flux density in H. tasmanica beds and the photosynthesis—photon flux density curve of H. tasmanica. This comparison demonstrated that epiphyte biomass can accumulate fast enough to shade H. tasmanica leaves and significantly reduce the time (to less than one half of the leaf life span) in which positive net photosynthesis of the leaf blade is possible.     

Effects of in situ light reduction on density and growth of the seagrass Heterozostera tasmanica (Martens ex Aschers.) den Hartog in Western Port,Victoria, Australia

Neutral density screens were used to reduce the level of irradiance available to an intertidal population of Heterozostera tasmanica (Martens ex Aschers.) den Hartog in Western Port, Victoria, Australia. When irradiance was reduced to 9 and 2% of control (ambient) levels, death of all leaf clusters of H. tasmanica resulted within 2 to 10 months. Reduction of irradiance to 35 and 25% of control levels resulted in a 25–50% decrease in leaf cluster density for the duration of the experiment (14 months). As irradiance level decreased leaf length increased (leaf length at 9% irradiance was twice leaf length in control areas) while leaf growth rate and leaf width remained the same. It is suggested that leaf growth rate per leaf cluster remains the same under reduced irradiance because of decreased likelihood of self-shading by surviving leaf clusters and increased surface area per leaf cluster. Density decreased more rapidly during summer than during winter at reduced light levels. This response may be due to an increase in the plant's light compensation point because of increased respiration at summer temperatures. Information on the lower limits of vertical distribution H. tasmanica in Western Port and Port Phillip Bay, Victoria together with the experimental irradiance reduction data suggests that H. tasmanica requires a minimum of ≈ 5% of surface irradiance for survival.     

The reproductive cycle of the asteroid Coscinasterias muricata in Port Phillip Bay, Victoria, Australia

The reproductive cycles of two populations of Coscinasterias muricata from Port Phillip Bay, Victoria, Australia are described in terms of organ indices, oocyte development and progesterone levels. Both Governor's Reef and South Channel Fort populations exhibited clearly defined reproductive cycles with two spawning periods, during summer and during spring. In both populations, the pyloric caecal index and gonadal index showed inverse cycles suggesting nutrient translocation from the pyloric caeca to the gonads for gametogenesis. Physiological changes, such as decreases in pyloric caecal index, and increases in gonadal index and oocyte diameter were observed following the months of increased progesterone concentrations in the female pyloric caeca. These results indicate a role for this steroid in the reproductive cycle. The results from the Governor's Reef population suggest that the influence of progesterone on the reproductive cycle of female C. muricata is regulated by photoperiod. Results also provide evidence of a role for seawater temperature in the reproductive process of this species.     

Activity of sperm and fertility in the potato moth, Phthorimaea operculella

In this investigation, two kinds of sperm (apyrene and eupyrene) were found in the potato moth. At each mating, a single spermatophore containing both types of sperm was passed to the female. Sperm storage was observed in males in the duplex and in the females in the spermatheca. The fertility of eggs was greater than 90 per cent. Sperm survival in females was from one to 12 days after mating, as determined by egg hatching. Parthenogenesis was absent.     

Limiting laws and counterion condensation in polyelectrolyte solutions: V. Further development of the chemical model

Counterion binding to polyelectrolyte chains is formulated as a chemical reaction M^z(free) → M^z(bound). Expressions for the chemical potentials of free and bound counterions are set equal to obtain the reaction equilibrium. The results are equivalent to those in the previous paper of this series. An additional result obtained here is that a polyion holds its bound counterion layer with a strength on the order of 100 $\text{kcal}\text{(mole cooperative unit)}$. The method is then applied to the calculation of the polarizability along the chain due to the bound (condensed) counterions.     

Changes in macrophage status in vivo during infection with and immunity to Leishmania enriettii

The changing status of peritoneal macrophages in guinea pigs infected with Leishmania enriettii has been examined. It was possible to demonstrate that, at certain times during a primary infection and following attempted reinfection of immune animals, the response of peritoneal macrophages to lymphokine contact in vitro was altered. At these times the harvested cells appeared to behave in vitro as if they had been at least partially activated in vivo before removal. They were unresponsive to lymphokine in the migration inhibition assay, and contact with lymphokine in culture caused a rapid increase in the level of glucose oxidation in these cells. It is suggested that changes in the response of macrophages to lymphokine in vitro may be one way of monitoring activation in vivo.     

A prestaining method for the quantitative assay of proteins on polyacrylamide gels

Dyes have been synthesised¹, which make it possible to prestain proteins prior to electrophoresis on polyacrylamide gels. After discussing the criteria which have to be fulfilled by the dyes, their method of application is described. The method has been tested on a number of selected acidic and basic proteins and also on peptide obtained by the digestion of bovine serum albumin with cyanogen bromide. Excellent reproducibility, stoichiometry and a sensitivity of 0.2 μg with some proteins has been obtained.     

In vitro stimulation of cell death in the moulting glands of Oncopeltus fasciatus by 20-hydroxyecdysone

The moulting glands of the milkweed bug, Oncopeltus fasciatus, normally degenerate just before the time of ecdysis to an adult (day 7 of the fifth instar). Morphologically normal cell death can be prematurely stimulated in vitro by 20-hydroxyecdysone. Breakdown is triggered by a 24-hr period of exposure to 20-hydroxyecdysone, but an additional incubation period is required before clear signs of degeneration are manifested. Glands removed after the onset of endogenous ecdysteroid secretion degenerate in vitro in the absence of added hormones. Thus, in the moulting glands of Oncopeltus, ecdysteroids appear to act as an important trigger for metamorphic cell death.     

Hyperpigmented patches in the skin of the newt Notophthalmus viridescens

In the integument of the red-spotted newt there occasionally appear patches of skin which are at the same time melanistic and iridescent. Such hyperpigmented patches have been found on the back, on the tail and on the dorsal surface of both fore and hind limbs. Cytological examination of several such areas revealed the presence of large numbers of chromatophores distributed throughout the dermis. The majority of the chromatophores consisted of atypically large and dendritic melanophores, which contained typical pigment granules. The iridescence resulted from a high incidence of iridophores. Xanthophores also were found in considerable abundance. This extensive and apparently random intermingling of melanophores, iridophores and xanthophores in limited areas constitutes a striking exception to the usual distributional patterns of pigment cells in this animal.     

The diversion of dimethylailylpyrophosphate from polyisoprenoid to cyclopiazonic acid biosynthesis in Penicillium cyclopium westling

During the production of α-cyclopiazonic acid (αCA) by Penicillium cyclopium, dimethylallyltransferase (EC. 2.5.1.1.) T, isopentenyl pyrophosphate isomerase (EC. 5.3.3.2) I, and a prenyl-aryltransferase, S, which produces β-cyclopiazonic acid (βCA) are all induced at the same time. This last enzyme appears maximally before the highest rate of α- or βCA production. Both transferases are not utilized to their maximum capacity, and the production of their end products seems to bear no relationship to their concentrations. Other controls therefore must play an important role in the utilization of their common substrate dimethylallylpyrophosphate (DMAPP). There are two possible control systems: (a), a direct competition by S and T for DMAPP; and (b), control by compartmentation. The first possiblility is the more likely, in view of some of the controls that could apply to the deflection. The three enzymes were separated so that possible controls on the deflection of DMAPP from polyisoprenoids could be studied. They all possessed a subunit structure and exhibited maximum molecular weithts (in the absence of divalent cations and presence of a thiol reductant) of 96 000 (S) and 64 000 (I and T) daltons. Mg²⁺ caused a diminution in size to 75 000 (S) and 50 000 (I and T) daltons. Mg²⁺ had the same effect on I and T but caused major disruptive changes to S. These effects were reversible by addition of EDTA. S was quite specific for DMAPP and cycloacetoacetyl-l-tryptophan (cAATrp) and exhibited Michaelis constants as follows; K_m^cAATrp, 6.0μM and K_m^DMAPP 2.0 μM. It had no obvious requirement for a divalent cation and had an isoelectric point of 5.3. I had a K_m of 6.7 μM and an isoelectric point of 4.5, and either Mg²⁺ or Mn²⁺ was essential. The Michaelis constants for T could not be given but its isoelectric point was 5.1. The enzyme carried out the two reactions normally associated with it (i.e., two additions of IPP to produce farnesyl pyrophosphate) and required Mg²⁺ to do so. The pH optima for S, I, and T were 6.5–7.5, 6.0, and 8.0 respectively. The early and major controlling factor was the appearance of the cosubstrate of S, cAATrp. Other factors were: (a), the appearance of αCA which inhibited T more effectively than S; (b), the removal of free Mn²⁺ and Mg²⁺, both essential for I and T but not for S, possibly brought about by chelation with cAATrp, α- and βCA; (c), the observed low pH of 6.0 when the activity of S was unaltered, I was at its highest, and T exhibited 50% of its maximum; and (d), an activation of I by low physiological levels of βCA and cAATrp which would enhance the rate of appearance of DMAPP to react with an existing pool of cAATrp.     

A kinetic and structural comparison of chorismate mutase/prephenate dehydratase from mutant strains of Escherichia coli K12 defective in the PheA gene

Three classes of mutant strains of Escherichia coli K12 defective in pheA, the gene coding for chorismate mutase/prephenate dehydratase, have been isolated: (1) those lacking prephenate dehydratase activity, (2) those lacking chorismate mutase activity, and (3) those lacking both activities. Chorismate mutase/prephenate dehydratase from the second class of mutants was less sensitive to inhibition by phenylalanine than wild-type enzyme and, along with the defective enzyme from the third class of mutants, could not be purified by affinity chromatography on Sepharosyl-phenylalanine. Pure chorismate mutase/prephenate dehydratase protein was prepared from two strains belonging to the first class. The chorismate mutase activity of these enzymes is kinetically similar to that of the wild-type enzyme except for a two- to threefold increase in both the K_a for chorismate and the K_is for inhibition by prephenate. In both cases only one change in the tryptic fingerprint was detected, resulting from a substitution of the threonine residue in the peptide Gln·Asn·Phe·Thr·Arg. This suggests that this residue is catalytically or structurally essential for the dehydratase activity.     

Effects of ovariectomy and estradiol replacement therapy upon the sexual and aggressive behavior of the greater galago (Galago crassicaudatus crassicaudatus)

The effects of ovariectomy and estradiol treatment upon sexual and aggressive behavior were studied in a prosimian primate, the greater galago. Ovariectomized galagos were sexually unreceptive and frequently aggressive, but retained their sexual attractiveness to males. When females were treated with estradiol monobenzoate, however, their aggression and refusals of males' mounting attempts decreased markedly. Although males mounted these females, they usually failed to copulate, possibly because the females did not perform certain postural adjustments which assist males to intromit. Estradiol benzoate alone, even in large doses, does not fully restore patterns of mating behavior in ovariectomized female greater galagos. These observations on a prosimian primate are in striking contrast to the results of similar work on Old World monkeys and chimpanzees.     

A field study of the headbob displays of male green iguanas (Iguana iguana): Variation in form and context

Headbob displays play an important role in the social behaviour of male green iguanas (Iguana iguana). Four types of headbobs were identified, and the variability in form and context were determined from quantitative analyses of displays filmed in the field. The Roll is a conspicuous advertisement display. The Shudder, the most variable in form, occurred during close contact between males and females. The Roll-shudder is intermediate between the Roll and Shudder in its form and use. The Signature Bob, the most stereotyped display in form, punctuates much activity and is the most variable in contextual use. This display encodes species identity, and possibly individual identity. The conspicuous nature of the headbob displays was enhanced by the intensified colour of territorial males, and by the selection of highly visible display posts. This system of visual displays is viewed as the product of related sets of constraints, including the iguanas' physical capacities, the forest environment, and the social environment.     

The use of region-specific antibodies in the characterization and localization of vasoactive intestinal polypeptide-like substances in the rat gastrointestinal tract

Antisera specific for different regions of porcine VIP have been used in radioimmunoassay and immunohistochemical studies of immunoreactive VIP in rat small and large intestine. Cation exchange chromatography of intestinal extracts separated two major and one minor peak of immunoreactivity. One major peak eluted in a similar position to natural porcine VIP and was read equally by NH₂-terminal-specific, and mid- and COOH-terminal-specific antisera. A second major peak, and the minor peak, eluted earlier than porcine VIP, and were read significantly less well with mid- and COOH-terminal antisera compared with NH₂-terminal-specific antisera. All forms of VIP occurred mainly in extracts of muscle layers of the gut, and no antiserum revealed more than trace amounts of immunoreactivity in mucosal extracts. In immunohistochemical studies all antisera demonstrated fluorescent nerve fibres in the enteric plexuses, circular smooth muscle and lamina propria; some antisera demonstrated nerve cell bodies predominantly in the submucous plexus. NH₂-terminal-specific antisera also demonstrated a sparse population of mucosal endocrine-like cells in the ileum and colon that were not seen with other antisera. It is concluded that VIPergic neurons of the rat gut contain a peptide closely resembling porcine VIP and at least two less basic variants with similar NH₂-terminal antigenic determinants. VIP-like peptides may also occur in endocrine cells, but since these peptides appearto fact that the majority of neuronal VIP in rat gut exists in a form that is both chromatographically and immunochemically distinct from porcine VIP, and may well possess different biological properties.     

Selective depletion of substance P-immunoreactive neurones in the transitional zone of the colon in piebald lethal mice

The distribution of substance P in the colon of piebald lethal (s¹/s¹) mice was studied by radioimmunoassay and immunohistochemistry. These animals inherit as a Mendelian recessive trait an aganglionic distal colon. In the region proximal to the aganglionic segment, there is an extensive transitional or hypoganglionic zone, in which the total number of nerve cells in the myenteric plexus is reduced, while those in the submucous plexus tend to be normal. Immunohistochemical studies indicate that substance P-immunoreactive neurones accounted for approx. 10% of the total number of normal myenteric neurones, but in the hypoganglionic region they accounted for about 5%, and this difference was statistically significant. By radioimmunoassay, the concentrations of substance P in both the aganglionic and the hypoganglionic regions of the colon were reduced compared with the corresponding segments in normal mice. However calculation of the mean substance P content per neurone revealed similar quantities (about 1 fmol) in both normal and s¹/s¹ mice. Substance P-immunoreactivity in the tissue extracts eluted in the same position as the synthetic peptide on ion exchange and gel filtration chromatography. It is suggested that a sub-population of substance P-immunoreactive neurones in the hypoganglionic zone is selectively depleted compared with other myenteric neurones. The factors involved remain to be elucidated, but this strain of mice could prove useful for studies of the mechanisms involved in differentiation and development of enteric peptidergic neurones.     

The relationship of age,sex, and reproductive state to assimilation efficiency in the adult milkweed bug, Oncopeltus fasciatus

The influence of age, sex, and reproductive state on efficiency of assimilation was examined in the milkweed bug Oncopeltus fasciatus. Amounts of food ingested and excreted decline with age in virgin males and females. Mated females laying eggs ingest significantly more food than virgin animals of either sex and also maintain a consistently higher assimilation efficiency. A qualitative analysis of the level of assimilation required for reproductive effort is discussed.     

Trans-bilayer pseudocontact shifts produced by lanthanide ions in the 1H and 31P-nmr spectra of phospholipid vesicular membranes and their temperature variation

1. Shifts in the ¹H and ³¹P-nmr signals originating from the outer and inner phosphorylcholine head-groups and from the lipid acyl chains are observed when phosphatidylcholine vesicles are treated with increasing extravesicular concentrations of the lanthanides Eu³⁺, Pr³⁺, Yb³⁺, and Dy³⁺. 2. The addition of KNCS to increase the binding of the lanthanide ions to the outer head-groups is used to demonstrate that the intravesicular group shifts are not caused by bulk susceptibility effects. 3. The magnitude and direction of the observed shifts in the ¹H-nmr spectrum are shown to be consistent with (a) pseudocontact interaction of the paramagnetic lanthanide ions with the outer phospholipid head-groups, (b) current views of the conformation of the phosphatidylcholine head-group in the presence of lanthanides, and (c) a conservation of magnetic field within the vesicles due to their spherical nature. 4. Variation of the shifts with temperature are compared for egg phosphatidylcholine and dipalmitoyl phosphatidylcholine. The temperature variation in shifts is also used to study phase transitions in each monolayer and phase separations in mixed lipid systems.     

Female secondary sexual coloration and sex recognition in the keeled earless lizard, Holbrookia propinqua

Relationships between male social behaviour and female reproductive coloration in the iguanid lizard Holbrookia propinqua were examined by introduction of tethered non-resident lizards into the territories of adult males. Introduced lizards were plainly coloured females, females having bright reproductive coloration, adult males, plain females painted to resemble brightly coloured females, bright females painted to mimic plain females, and males painted with the bright yellow and orange secondary sexual coloration of females. Resident males courted all unpainted females, despite being aggressively rejected by the brightly coloured ones. They also courted all but two females in each of the painted groups. All unaltered non-resident males were challenged, attacked or subjected to other aggressive behaviour by residents, but all non-resident males painted to resemble bright females were courted. This differential treatment is highly significant. It clearly demonstrates that the bright female pigmentation functions in sex recognition, identifying a female to males. Other stimuli, especially pheromonal and behavioural cues, may contribute to sex recognition. Because sex recognition alone seems insufficient to account for the evolution of bright female coloration in H. propinqua and several other iguanids, several proposed additional functions are discussed.