Phorbol diester treatment promotes enhanced adenylate cyclase activity in frog erythrocytes

Incubation of intact frog erythrocytes with 12-O-tetradecanoyl phorbol-13-acetate (TPA), a tumor-promoting phorbol diester which activates protein kinase C, results in an approximate two- to threefold increase in subsequently tested beta-adrenergic agonist-stimulated adenylate cyclase activity. This increase is due to an elevation in the Vmax of the enzyme rather than to a change in affinity for the agonist. TPA treatment of frog erythrocytes does not alter the affinity (KD) or the binding capacity (Bmax) for the beta-adrenergic antagonist [125I]cyanopindolol. In addition, agonist/[125I]cyanopindolol competition curves are not affected by TPA pretreatment nor is their sensitivity to guanine nucleotides. Incubation of frog erythrocyte membranes alone with TPA does not promote sensitization or activation of adenylate cyclase activity. Pretreatment of intact frog erythrocytes with TPA also produces approximately two- to threefold increases in basal, guanine nucleotide-, prostaglandin E1-, forskolin-, NaF-, and MnCl2-stimulated adenylate cyclase activities in frog erythrocyte membranes. This enhancement of adenylate cyclase activity by TPA is induced rapidly (t1/2 approximately equal to 5 min) and with an EC50 of about 10(-7) to 10(-6) M. Other tumor-promoting phorbol diesters or phorbol diester-like compounds including 4 beta-phorbol 12,13-dibutyrate, 4 beta-phorbol 12,13-didecanoate, and mezerein are effective in promoting enhanced adenylate cyclase activity. In contrast, phorbols such as 4 beta-phorbol, 4 alpha-phorbol 12,13-didecanoate, and 4-O-methylphorbol 12-myristate 13-acetate, which are inactive in tumor promotion and which do not activate protein kinase C, do not affect frog erythrocyte adenylate cyclase activity. These data are suggestive of a protein kinase C-mediated phosphorylation of one of the adenylate cyclase components that is distal to the receptor, i.e., the nucleotide regulatory and/or catalytic components.     

Synthesis of gamma-L-glutaminyl-[3,5-3H]4-hydroxybenzene and the study of reactions catalyzed by the tyrosinase of Agaricus bisporus.

gamma-L-Glutaminyl-[3,5-3H]4-hydroxybenzene was synthesized in order to study the kinetics of its hydroxylation by tyrosinase purified from Agaricus bisporus and to explore its role in the induction of the dormant state in the spores of this species. It was found to be unique among the monophenolic substrates for tyrosinase in that the lag period for the hydroxylation reaction decreased with increasing substrate concentration. Unlike previously studied compounds, this phenol appeared to function as an electron donor, allowing it to act as its own co-substrate in the hydroxylation reaction. Its catechol product, gamma-L-glutaminyl-3,4-dihydroxybenzene, was found to be a superior co-substrate, yielding its electrons more readily (oxidation peak potential +0.18 V as compared with +0.65 V for the phenol). In situ periodate oxidation of gamma-L-glutaminyl-3,4-dihydroxybenzene to gamma-L-glutaminyl-3,4-benzoquinone confirmed the co-substrate role of the catechol in the hydroxylation reaction. The tyrosinase-mediated oxidation of gamma-L-glutaminyl-3,4-dihydroxybenzene to gamma-L-glutaminyl-3,4-benzoquinone occurred with an apparent Km = 1.54 mM and Vmax = 0.36 mmol/min/mg of enzyme. gamma-L-Glutaminyl-4-hydroxybenzene acted as an inhibitor of the oxidation reaction.     

The role of biofouling development in the loss of seed mussels in aquaculture

The efficient seeding of juvenile mussels is critical to the sustainability and profitability of mussel aquaculture. However, seeding mussels is highly inefficient, with many juveniles being lost in the following few months. One possible cause of these losses could be the development of biofouling assemblages. Therefore, the relationships between biofouling accumulation and losses of juveniles were assessed. Losses of juvenile mussels were initially high (42.9–49.1% over approximately one to two weeks), with lower rates of loss over the following four to five months. Biofouling development followed a successional pattern beginning with colonisation by amphipods, subsequent establishment of macroalgae, and the formation of an assemblage dominated by mussels and sessile invertebrates. However, biofouling development did not play a major role in the loss of juveniles. Rather, large-scale losses of mussels occurred shortly after seeding when biofouling was scant, suggesting alternative causes of loss were in operation.     

Ontogenetic changes in enzyme activities associated with energy production in the spiny lobster, Jasus edwardsii

The larval life of the spiny lobster Jasus edwardsii is one of the longest and most complex of any marine organism and is poorly understood due to the difficulty of studying cryptic, pelagic organisms. Hence, the capacity for active swimming in the phyllosoma, puerulus and juvenile stages and the use of possible metabolic fuel reserves was inferred from a number of enzyme activities, including citrate synthase, lactate dehydrogenase, and HOAD. High activities of CS and LDH in abdominal tissues of Stage 11 phyllosoma and pueruli are consistent with a capacity to commence active on-shore movement. The activities of LDH and HOAD showed positive allometry while CS was independent of body mass. The body mass dependence of LDH activity may reflect the developing ability of the lobster to initiate brief escape manoeuvres, and the scaling of HOAD reflects an increased use of lipid fuel reserves. Aerobic enzyme activities were higher in abdominal tissues than in cephalic tissues of pelagic pueruli, but high activities appear in the cephalic tissues of juveniles. These changes mirror a developmental shift in activity from pelagic oceanic swimming to a benthic existence on the seabed of the near shore. The low LDH activity in pueruli confirmed previous findings that they have limited feeding capacity, with carbohydrate contributing little towards the major energy reserves. The highest LDH activities occur in the abdominal muscles of juveniles and correlate with rapid tail-flicking escape behaviour. The activities of HOAD increased throughout development, and in the abdominal tissues of juveniles, may reflect lipid transformation and accumulation as an energy reserve. Enzyme activities, therefore, provide useful information concerning migratory behaviour that is presently unavailable from ecological studies.     

Biodiversity associated with restored small-scale mussel habitats has restoration decision implications

The global loss of marine ecosystem engineers has caused an unprecedented decline in biodiversity. Although wild shellfish habitats have been shown to support biodiverse ecosystems, little is known about how biodiversity is altered by restored shellfish habitats, particularly mussels. To explore the biodiversity response to restored mussel habitats we deposited mussels on the seafloor in 1.5?×?1.5 m plots across a gradient of benthic environments. To understand a holistic community response, this study looks at the response of three faunal classifications over 1 year: infauna, epifauna, and pelagic fauna, compared with adjacent control plots (no mussels). The restored mussel habitats recorded 42 times more demersal fish than control areas, while macroalgae and mobile benthic invertebrates had over a twofold increase in abundance. Overall, the addition of mussels to the seafloor resulted in a general reduction of infaunal abundance and biodiversity, but an increase in epifaunal and pelagic faunal abundances, specifically from those species that benefit from benthic habitat complexity and an increase in food availability. From a management perspective, we highlight location-specific differences to consider for future restoration efforts, including environmental conditions and potential observed factors such as nearby sources of species, particularly predators, and relevant demersal fish ranges. Ultimately, measuring biodiversity responses in small-scale studies will serve as a valuable guide for larger scale restoration efforts and this study recommends considerations to enhance biodiversity outcomes in restored mussel habitats.

     

Adaptive avoidance of reef noise

Auditory information is widely used throughout the animal kingdom in both terrestrial and aquatic environments. Some marine species are dependent on reefs for adult survival and reproduction, and are known to use reef noise to guide orientation towards suitable habitat. Many others that forage in food-rich inshore waters would, however, benefit from avoiding the high density of predators resident on reefs, but nothing is known about whether acoustic cues are used in this context. By analysing a sample of nearly 700,000 crustaceans, caught during experimental playbacks in light traps in the Great Barrier Reef lagoon, we demonstrate an auditory capability in a broad suite of previously neglected taxa, and provide the first evidence in any marine organisms that reef noise can act as a deterrent. In contrast to the larvae of species that require reef habitat for future success, which showed an attraction to broadcasted reef noise, taxa with a pelagic or nocturnally emergent lifestyle actively avoided it. Our results suggest that a far greater range of invertebrate taxa than previously thought can respond to acoustic cues, emphasising yet further the potential negative impact of globally increasing levels of underwater anthropogenic noise.     

Behavioural response thresholds in New Zealand crab megalopae to ambient underwater sound

A small number of studies have demonstrated that settlement stage decapod crustaceans are able to detect and exhibit swimming, settlement and metamorphosis responses to ambient underwater sound emanating from coastal reefs. However, the intensity of the acoustic cue required to initiate the settlement and metamorphosis response, and therefore the potential range over which this acoustic cue may operate, is not known. The current study determined the behavioural response thresholds of four species of New Zealand brachyuran crab megalopae by exposing them to different intensity levels of broadcast reef sound recorded from their preferred settlement habitat and from an unfavourable settlement habitat. Megalopae of the rocky-reef crab, Leptograpsus variegatus, exhibited the lowest behavioural response threshold (highest sensitivity), with a significant reduction in time to metamorphosis (TTM) when exposed to underwater reef sound with an intensity of 90 dB re 1 μPa and greater (100, 126 and 135 dB re 1 μPa). Megalopae of the mud crab, Austrohelice crassa, which settle in soft sediment habitats, exhibited no response to any of the underwater reef sound levels. All reef associated species exposed to sound levels from an unfavourable settlement habitat showed no significant change in TTM, even at intensities that were similar to their preferred reef sound for which reductions in TTM were observed. These results indicated that megalopae were able to discern and respond selectively to habitat-specific acoustic cues. The settlement and metamorphosis behavioural response thresholds to levels of underwater reef sound determined in the current study of four species of crabs, enables preliminary estimation of the spatial range at which an acoustic settlement cue may be operating, from 5 m to 40 km depending on the species. Overall, these results indicate that underwater sound is likely to play a major role in influencing the spatial patterns of settlement of coastal crab species.     

Genetic isolation between the Western and Eastern Pacific populations of pronghorn spiny lobster Panulirus penicillatus

The pronghorn spiny lobster, Panulirus penicillatus, is a circumtropical species which has the widest global distribution among all the species of spiny lobster, ranging throughout the entire Indo-Pacific region. Partial nucleotide sequences of mitochondrial DNA COI (1,142-1,207 bp) and 16S rDNA (535-546 bp) regions were determined for adult and phyllosoma larval samples collected from the Eastern Pacific (EP)(Galápagos Islands and its adjacent water), Central Pacific (CP)(Hawaii and Tuamotu) and the Western Pacific (WP)(Japan, Indonesia, Fiji, New Caledonia and Australia). Phylogenetic analyses revealed two distinct large clades corresponding to the geographic origin of samples (EP and CP+WP). No haplotype was shared between the two regional samples, and average nucleotide sequence divergence (Kimura's two parameter distance) between EP and CP+WP samples was 3.8±0.5% for COI and 1.0±0.4% for 16S rDNA, both of which were much larger than those within samples. The present results indicate that the Pacific population of the pronghorn spiny lobster is subdivided into two distinct populations (Eastern Pacific and Central to Western Pacific), with no gene flow between them. Although the pronghorn spiny lobster have long-lived teleplanic larvae, the vast expanse of Pacific Ocean with no islands and no shallow substrate which is known as the East Pacific Barrier appears to have isolated these two populations for a long time (c.a. 1MY).