Intraspecific co-variation between egg and body size affects fertilisation kinetics of free-spawning marine invertebrates

Fertilisation of eggs of free-spawning marine invertebrates depends on factors affecting sperm concentration in the field and also on gamete characteristics such as egg size. In the free-spawning intertidal ascidian Pyura stolonifera mean egg size increased with maternal size in 2 separate populations. The largest ascidian produced eggs that were, on average, 50% greater in volume than the eggs produced by the smallest individual studied. There was no evidence to suggest that egg density varied with adult size and egg dry organic weight increased with maternal size. The fertilisation kinetics of this species were strongly affected by the variation in egg size, with the eggs of large individuals requiring much less concentrated sperm to achieve maximal levels of fertilisation success than the eggs of small individuals. We suggest that variation in egg size between individuals of different sizes and ages may be an important factor in determining fertilisation success for ascidians of this species.

Risk management for scuba diving operators on Australia's Great Barrier Reef

Australia's Great Barrier Reef is one of the world's most popular scuba diving destinations. Unfortunately, a series of recent diving injuries and deaths has tarnished the region's safety record. In particular, media attention surrounding the disappearance of American divers Thomas and Eileen Lonergan has focused attention on dive operators' legal responsibilities and the consequences of failing to discharge their duty of care to customers. This paper briefly examines the relevant Australian law for recreational diving operations, and reviews risk management strategies that may reduce or prevent the occurrence of future problems. (C) 2000 Elsevier Science Ltd. All rights reserved.

Clathrins A-C: Metabolites from a southern Australian marine sponge, Clathria species

A Clathria sp. collected in the Great Australian Bight has yielded the novel metabolites clathrins A (6), B (7), and C (8). Structures were assigned to clathrins A-C on the basis of spectroscopic analysis. Clathrin A (6) represents a plausible biosynthetic intermediate that provides an inferred link between marine sesquiterpene/benzenoids and mixed terpene/shikimate biosynthesis.

Muscle fibre types and size distribution in sub-antarctic notothenioid fishes

The presumptive tonic muscles fibres of Cottoperca gobio, Champsocephalus esox, Harpagifer bispinis, Eleginops maclovinus, Patagonothen tessellata, P. cornucola and Paranotothenia magellanica stained weakly or were unstained for glycogen, lipid, succinic dehydrogenase (SDHase) and myosin ATPase (mATPase) activity. Slow, intermediate and fast twitch muscle fibres, distinguished on the basis of the pH stability of their mATPases, showed intense, moderate and low staining activity for SDHase, respectively. Slow fibres were the major component of the pectoral fin adductor profundis muscle. The proportion of different muscle fibre types varied from the proximal to distal end of the muscle, but showed relatively little variation between species. The myotomes contained a lateral superficial strip of red muscle composed of presumptive tonic, slow twitch and intermediate fibres, thickening to a major wedge at the horizontal septum. All species also had characteristic secondary dorsal and ventral wedges of red muscle. The relative abundance and localization of muscle fibre types in the red muscle varied between species and with body size in the protandric hermaphrodite E. maclovinus. The frequency distribution of diameters for fast twitch muscle fibres, the major component of deep white muscle, was determined in fish of a range of body sizes. The absence of fibres <20 mu m diameter was used as a criterion for the cessation of muscle fibre recruitment. Fibre recruitment had stopped in P, tessellata of 13.8 cm L-T and E, maclovinus of 32.8 cm L-T, equivalent to 49 and 36.5% of their recorded maximum sizes respectively. As a result in 20-cm P. tessellata, the maximum fibre diameter was 300 mu m and 36% of fibres were in excess of 200 mu m The unusually large maximum fibre diameter, the general arrangement of the red muscle layer and the extreme pH lability of the mATPase of fast twitch fibres are all common characters of the sub-Antarctic and Antarctic Notothenioids, including Cottoperca gobio, the suggested sister group to the Notothenidae. (C) 2000 The Fisheries Society of the British Isles.

Water wave-driven seepage in marine sediments

The action of water waves moving over a porous seabed drives a seepage flux into and out of the marine sediments. The volume of fluid exchange per wave cycle may affect the rate of contaminant transport in the sediments. In this paper, the dynamic response of the seabed to ocean waves is treated analytically on the basis of pore-elastic theory applied to a porous seabed. The seabed is modelled as a semi-infinite, isotropic, homogeneous material. Most previous investigations on the wave-seabed interaction problem have assumed quasi-static conditions within the seabed, although dynamic behaviour often occurs in natural environments. Furthermore, wave pressures used in the previous approaches were obtained from conventional ocean wave theories: which are based on the assumption of an impermeable rigid seabed. By introducing a complex wave number, we derive a new wave dispersion equation, which includes the seabed characteristics (such as soil permeability, shear modulus, etc.). Based on the new closed-form analytical solution, the relative differences of the wave-induced seabed response under dynamic and quasi-static conditions are examined. The effects of wave and soil parameters on the seepage flux per wave cycle are also discussed in detail. (C) 2000 Elsevier Science Ltd. All rights reserved.

Discorhabdin R: A new antibacterial Pyrroloiminoquinone from two latrunculiid marine sponges, Latrunculia sp and Negombata sp.

Two sponge's belonging to the family Latrunculiidae (Negombata and Latrunculia sp.) collected during scientific trawling operations in Prydz Bay, Antarctica, and by scuba off Port Campbell, Victoria, have yielded a new antibacterial pyrroloiminoquinone, discorhabdin R (2). The structure was assigned as 2 on the basis of detailed, spectroscopic analysis and comparison with the known co-metabolite discorhabdin B (3).

Eye design and color signaling in a stomatopod crustacean Gonodactylus smithii

Many species of stomatopod crustaceans have multiple spectral classes of photoreceptors in their retinas. Behavioral evidence also indicates that stomatopods are capable of discriminating objects by their spectral differences alone, Most animals use only two to four different types of photoreceptors in their color vision systems, typically with broad sensitivity functions, but the stomatopods apparently include eight or more narrowband photoreceptor classes for color recognition. It is also known that stomatopods use several colored body regions in social interactions. To examine why stomatopods may be so 'concerned' with color, we measured the absorption spectra of visual pigments and intrarhabdomal filters, and the reflectance spectra from different parts of the bodies of several individuals of the gonodactyloid stomatopod species, Gonodactylus smithii. We then applied a model of multiple dichromatic channels for color encoding to examine whether the finely tuned color vision was specifically co-evolved with their complex color signals. Although the eye design of stomatopods seems suitable for detecting color signals of their own, the detection of color signals from other animals, such as reef fishes, can be enhanced as well. Color vision in G. smithii is therefore not exclusively adapted to detect its own color signals, but the spectral tuning of some photoreceptors (e.g. midband Rows 2 and 3) enhances the contrast of certain color signals to a large enough degree to make co-evolution between color vision and these rather specific color signals likely. Copyright (C) 2000 S. Karger AG, Basel.

Tetraphyllidean metacestodes of teleosts of the Great Barrier Reef, and the use of in vitro cultivation to identify them

The tetraphyllidean metacestode diversity of 310 teleost fishes, including 87 species from 31 families, was examined from Heron Island, The Great Barrier Reef, Australia. Eleven metacestode 'types' were identified with the use of light microscopy. Host-specificity varied greatly among metacestode types. Incorporation of in vitro cultivation allowed generic identification for some types. Types 1 and 2 belong to Uncibilocularis Southwell, 1925, and have triloculate bothridia and one pair of Forked hooks with unequal prongs; Type 3 has quadriloculate bothridia. Hook development was insufficient to determine in which genus, Acanthobothrium van Beneden, 1849 or Calliobothrium van Beneden, 1850, this type may belong. Type 4 has unilocular bothridia with simple edges and belongs to Anthobothrium van Beneden, 1850. Type 5 has multiloculated bothridia which are invaginated within pouches. This type belongs to the Rhinebothriinae although its generic identity cannot be determined. The bothridia of Type 5 everted within 24 hours of in vitro cultivation and revealed the presence of two forms, one having 48 loculi per bothridium, the other 72 per bothridium. In vitro studies provide additional support for existing theories of onchobothriid scolex development.

Lorneamides A and B: Two new aromatic amides from a southern Australian marine actinomycete

A marine actinomycete (MST-MA190) isolated from a sample of beach sand collected near Lorne on the southwest coast of Victoria, Australia, has yielded two new aromatic amides, lorneamide A (1) and lorneamide B (2). The lorneamides belong to a novel class of tri-alkyl-substituted benzenes, and their structures were determined by spectroscopic methods.

Phorbasin A: A novel diterpene from a southern Australian marine sponge, phorbas species

A southern Australian Phorbas species has yielded a novel diterpene, phorbasin A (1), possessing an unprecedented carbon skeleton. The structure for phorbasin A was determined by detailed spectroscopic analysis.

Marine bioprospecting - Trawling for treasure and pleasure

This Microreview seeks to highlight the molecular diversity present in marine organisms, and illustrate by example some of the challenges encountered in exploring this resource. Marine natural products exhibit an impressive array of structural motifs, many of which are derived from biosynthetic pathways that are uniquely marine, Most importantly some marine metabolites possess noteworthy biological activities, activities that have potential application outside marine ecosystems, such as antibiotics, antiparasitics, anticancer agents etc... The isolation, spectroscopic characterisation and assignment of stereostructures to these unusual metabolites is both challenging and rewarding. Examples featured in this Microreview follow a common theme in that they are all recent accounts of the isolation of natural products from Australian marine sponges, carried out in the laboratories of the author. In addition to presenting brief comments on specific structure elucidation strategies, an effort is made to emphasize techniques for solving stereochemical issues, as well as to speculate on the biosynthetic origins of some of these exotic marine natural products.

Structure revision and assignment of absolute stereochemistry of a marine C-21 bisfuranoterpene

The C-21 bisfuranoterpene (-)-isotetradehydrofurospongin-1 (6), previously isolated from a Western Australian Spongia sp., has been reisolated from a specimen of Spirastrella papilosa collected during scientific trawling operations in the Great Australian Eight. A 2D NMR analysis of 6 has prompted reassignment of the published structure 5, while degradation and chiral HPLC analysis have allowed determination of the absolute stereochemistry.

Onnamide F: A new nematocide from a southern Australian marine sponge, Trachycladus laevispirulifer

A southern Australian marine sponge, Trachycladus laevispirulifer, has yielded a potent new nematocide with antifungal activity which has been identified as onnamide F (1). The structure for 1 was assigned by detailed spectroscopic analysis and chemical conversion to the methyl ester 2. Onnamide F contains a common structural motif previously described in a number of natural products exhibiting interesting pharmacological activities, including the insect chemical defense agent pederin (3), and the sponge metabolites the onnamides, mycalamides, and theopederins.