Metamorphosis and developmental evolution in <Emphasis Type="Italic">Ophionereis</Emphasis> (Echinodermata: Ophiuroidea)

The brittle star Ophionereis schayeri has abbreviated non-feeding development through a reduced ophiopluteus and a vitellaria larva. The metamorphic changes involved with development from a bilateral larva to a radial juvenile were examined in detail. The reduced ophiopluteus has a continuous ciliated band that breaks up into discontinuous ciliary ridges at the vitellaria stage. As the vitellaria develops, the juvenile rudiment forms in the mid-ventral region. The rudiment then undergoes a morphogenetic movement to the left of the larval anterior/posterior axis. This results in a dramatic transformation from bilateral to radial symmetry and is accompanied by development of juvenile structures and settlement, 6–7 days after fertilisation. Ophiuroid development through one larval stage, the ophiopluteus, is termed Type I; whereas development through two larval stages, the ophiopluteus and vitellaria, is termed Type II. We examined the evolutionary changes in the expression of Type II development in Ophionereis by comparing the ontogeny of six species with a range of larval forms. O. fasciata has the ancestral-like planktotrophic ophiopluteus. Vestigial pluteal structures in the larvae of O. schayeri, provide a link between ophiopluteal and vitellarial forms during evolution of non-feeding development. The diversity of larval forms in Ophionereis indicates that evolution of non-feeding development through a vitellaria (Type II) may have involved an increase in egg size, reduction of pluteal structures and shortening of the time to metamorphosis. Assessment of the phylogenetic significance of Types I and II development awaits additional comparative data on the metamorphic stages of other ophiuroid genera.Communicated by G.F. Humphrey, Sydney     

Reproduction of sympatric populations of Patiriella gunnii,P. calcar and P. exigua in New South Wales,asterinid seastars with direct development

Three asterinid seastars, Patiriella gunnii (Gray), P. calcar (Lamarck) and P. exigua (Lamarck) are sympatric in southeast Australia and form part of a series of Patiriella species endemic to Australian shores. Reproduction of co-occurring populations of P. gunnii, P. calcar and P. exigua was investigated in New South Wales from December 1988 to February 1991. Their reproductive cycles were documented by the gonad index (GI) method and by histological examination of the gonads. The annual cycle of the pyloric caecae was also documented and the relationship between the two indices was examined. Oogenesis and spermatogenesis are described in histological detail. The three species produce large yolky eggs and have direct development. Vitellogenesis and weight-gain by the ovaries results from accumulation of periodic acid Schiff (PAS +) material by the oocytes. P. gunnii and P. calcar are gonochoric and have well-defined reproductive cycles, spawning in spring and summer. There was a sharp decline in the GI of P. gunnii in December due to potentially synchronous spawning. Histological examination revealed that initiation of gamete release occurred in August. Gamete release by P. calcar also started in August, with episodic spawning through December. P. gunnii and P. calcar have coincident 3 to 4 mo breeding seasons. In general, P. exigua is protandrous with a broad size range over which sex change occurs. Some P. exigua, however are simultaneous hermaphrodites at the outset of gonad formation and become increasingly female with growth. This species has continuous gametogenesis and oviposits its eggs on the undersides of intertidal boulders, with enhanced oviposition during winter and spring. Newly metamorphosed P. exigua occupy intertidal microhabitats and were located in the field from August to October. It is suggested that increasing sea temperature during spring may serve to cue gamete release by P. gunnii and P. calcar and that enhanced oviposition of P. exigua in winter may be in response to conditions optimal for development of the egg masses at this time. The GI of male and female P. gunnii and P. calcar did not differ, while male P. exigua had a significantly lower GI than the females. Small males are characteristic of this latter species, and it is suggested that the decreased male investment in P. exigua is associated with its non-planktonic development. The gonad and pyloric caeca (PCI) indices of P. gunnii exhibited a reciprocal relationship, indicating that the transfer of nutrients from the caeca to the gonads supports gametogenesis. These indices were partly reciprocal in P. calcar. It is suggested that gonadal growth in P. calcar may be less dependent on caecal reserves than that in P. gunnii. The PCI of P. exigua maintained a similar level throughout the year and was higher than the GI. Although the Patiriella species have coincident breeding periods, temporal differences in the intensity of spawning appears to reproductively isolate them in the field.     

Introduction of the northern Pacific asteroid Asterias amurensis to Tasmania: reproduction and current distribution

The northern Pacific asteroid Asterias amurensis (Lütken) has been recently introduced to Tasmania and is now well-established in east and southeast Tasmania. This sea star is conspicuous throughout the Derwent River estuary and is particularly abundant in the Hobart port area. Reproduction of two populations of A. amurensis at Sullivans Cove and at Sandy Bay was investigated from August 1993 to October 1994 by gonadal histology and measurement of the gonad index (GI). An intense period of vitellogenic and spermatogenic growth started in April, with the breeding condition reached by June. In 1994, peak GI was recorded at Sullivans Cove in July and at Sandy Bay in August. Although these data indicated that the Sullivans Cove population spawned before the Sandy Bay population, histological examination revealed that major spawning activity occurred in both populations from July onwards. In the early part of the breeding season, gametogenesis proceeded in parallel with spawning, with released gametes being replaced by continual gametogenesis. Maintenance of a higher GI during the early part of the breeding season at Sandy Bay was due to prolonged gametogenic replacement at this site. Spawning continued to October 1994, resulting in a sharp decline in the GI. The cyclic expansion and regression of the genital haemal sinus coincident with germinal proliferation and growth, respectively, support the contention that haemal fluid provides nutrients for gametogenesis. In Tasmania, A. amurensis experiences temperature and photoperiod regimes similar to those experienced by endemic populations of this species in the north Pacific. Comparison of reproduction of A. amurensis in Japan and Tasmania at similar latitudes shows that gametogenesis of the northern and southern populations is 6 mo out of phase. This phase shift provides evidence for photoperiodic regulation of gametogenesis in A. amurensis. The similar trend in sea-temperature regimes associated with the stages of gametogenesis in northern and southern populations suggests that temperature also plays a modulatory role. Based on the periodicity of reproduction and the ontogeny of A. amurensis, the planktotrophic larvae of this species would be expected to be in the plankton for several months from the end of winter through summer. Considering the highly fecund, dispersive life-history of A. amurensis, the southeast Tasmanian populations have considerable potential to serve as a seed source for establishment of new populations of this asteroid elsewhere in Tasmania and in mainland Australia. Received: 18 October 1996 / Accepted: 22 October 1996     

Reproduction of sympatric populations ofHeliocidaris erythrogramma andH. tuberculata (Echinoidea) in New South Wales

Reproduction ofHeliocidaris erythrogramma (Valenciennes) andH. tuberculata (Lamarck) was compared through examination of oogenesis, spermatogenesis and monthly measurement of the gonad index. These species occur sympatrically in the Sydney region. Their reproduction was examined at two sites near Botany Bay, New South Wales, Australia, from February 1989 through January 1990.H. erythrogramma produces buoyant, 450µm-diam eggs and the sperm have a head region 10µm in length. By contrast,H. tuberculata produces negatively-buoyant, 95µm-diam eggs and the sperm have a head region 4µm in length. Histochemical examination of the gonads revealed that periodic acid Schiff-positive (PAS +) material stored in the nutritive phagocytes appears to support vitellogenesis in both species. InH. tuberculata this material is utilized in the formation of PAS + yolk oligolecithal eggs, whereas inH. erythrogramma the PAS + material appears to be converted to lipid yolk in macrolecithal eggs.H. erythrogramma had a seasonal reproductive pattern with a 3 mo summer spawning period, whereas both populations ofH. tuberculata had a 9 mo breeding period characterized by the continual presence of nutrient reserves and vitellogenic oocytes which rapidly replaced spawned ova. Spawning ceased only for 3 mo over the summer. Due to the 9 mo spawning ofH. tuberculata it is not clear what factors serve to cue reproduction in this species.     

Caste allocation in litter Pheidole: lessons from plant defense theory

The allocation to growth, defense and reproduction varies in social insects within a species' life cycle and between species. A life cycle model (Oster and Wilson 1978) generally failed to predict caste allocation in small litter-nesting colonies of Neotropical Pheidole. Two of its assumptions were often invalid: food was unlikely to be limiting in four of five populations, and sexual biomass production accelerated, not decelerated, with colony size in three of five populations. One of five Pheidole populations studied had higher caste ratios (soldiers /workers) in reproductive colonies as predicted, and in no species did caste functions conform to predictions. We also adapted three models from plant defense theory to study between-species patterns of caste allocation. Among 12 litter Pheidole the amount of sterile biomass devoted to soldiers varied from 18 to 62%. Queen size, growth rate, and soldier investment positively covaried. Only one model, the cost of replacement hypothesis (McKey 1979), correctly predicted that species with costly female alates invest more in defense. The two hypotheses linking apparency to defense may also be valid if fast-growing colonies are more likely to attract the attention of predators.     

Fuels for development: evolution of maternal provisioning in asterinid sea stars

For marine invertebrates, larval developmental mode is inseparably linked to the nutritional content of the egg. Within the asterinid family of sea stars there have been multiple, independent, evolutionary transitions to lecithotrophic development from the ancestral, planktotrophic state. To investigate the evolution of maternal investment and development within the Asterinidae, we quantified individual lipid classes and total protein for eggs and larval stages of closely related species representing three developmental modes (planktotrophy, planktonic lecithotrophy and benthic lecithotrophy). Within species, maternal provisioning differed between females indicating that egg quality varied with parentage. Maternal investment was related to egg size but, after correcting for egg volume, we identified two major oogenic modifications associated with the evolution of lecithotrophic development: (1) a reduction in protein deposition that probably reflects the reduced structural requirements of nonfeeding larvae, (2) an increase in deposition of a single class of energetic lipid, triglyceride (TG). The exception was Parvulastra exigua, which has benthic, lecithotrophic development and lays eggs with a lipid to protein ratio close to that of planktotrophs. This oogenic strategy may provide P. exigua larvae with a protein “weight-belt” that assists in maintaining a benthic existence. Asterinids with planktotrophic development used a significant portion of egg TG to build a feeding bipinnaria larva. For Meridiastra mortenseni, female-specific differences in egg TG were still evident at the bipinnaria stage indicating that egg quality has flow-on effects for larval fitness. In lecithotrophic asterinids, TG reserves were not depleted in development to the larval stage whereas protein stores may help fuel early larval development. Available data indicate that there may be two evolutionarily stable egg lipid profiles for free-spawning, temperate echinoderms.     

Microstructure of the paper nautilus (Argonauta nodosa) shell and the novel application of electron backscatter diffraction (EBSD) to address effects of ocean acidification

Electron backscatter diffraction (EBSD) is a powerful microscopic technique to characterise the crystallography of biomineralisation. Here, we use high-resolution EBSD to characterise one of the least studied shells in the ocean, the female argonaut brood chamber, and to examine the changes in shell microstructure in response to incubation in decreased pH conditions. The thin (225 μm) shell of Argonauta nodosa is magnesium calcite with an average magnesium content of ca. 5.1 Wt % MgCO₃. EBSD and scanning electron microscopy (SEM) revealed that calcification of the shell is bidirectional with formation of irregular crystalline grains. Following a 2 week incubation in a range of pH treatments (pH, 8.1–7.2), shell fragment weight decreased by dissolution in pH ≤ 7.8. EBSD and SEM revealed altered shell crystallography and microstructure at pH ≤ 7.4 due to preferential etching down crystallite grain boundaries and a change in crystalline orientation on both the inner and outer shell surfaces. Our study highlights the value of EBSD for the detailed examination of biogenic carbonates and its potential use in the field of ocean acidification research.     

EVALUATING THE PERSISTENCE OF RESIDENTIAL WATER CONSERVATION: A 1992–1997 PANEL STUDY OF A WATER UTILITY PROGRAM IN DELAWARE1

This study systematically evaluates residential consumer responses to a utility conservation initiative based on an econometric analysis of a sample of 510 households served by Artesian Water Company, Inc. (New Castle County of Delaware). Using a panel study approach covering the period from 1992 to 1997, this study shows that Artesian's water conservation program has had statistically significant and persistent impacts on residential water consumption.     

The Park Made of Oil: Towards a Historical Political Ecology of the Kenneth Hahn State Recreation Area

Within the park-deprived inner-city landscapes of Los Angeles, an unprecedented change is underway. Long considered to be the epitome of anti-nature, Los Angeles is witnessing a boom in park development and ecological restoration. Derelict, blighted and contaminated inner-city brownfield sites are being converted to greenspaces, nature parks and wildlife refuges. Indeed, Los Angeles has been the recent recipient of hitherto unimaginable political and fiscal support to ameliorate the dearth of parks in its neglected urban core. This paper situates the current round of park development within its historical context, by focusing on a very particular local site—the Kenneth Hahn State Recreation Area. Applying the theoretical lens of political ecology, the authors trace some of the political, economic, ecological and institutional factors from the late 1920s onwards, which engendered the creation of a park atop an oilfield. In so doing, the authors deepen the understanding of how local greenspace allocation, poverty, race and political power are oftentimes complexly entangled. Precursor to a much larger project currently in the planning and development stages, the creation of the Kenneth Hahn State Recreation Area reveals some of the ways that the Southern California oil industry has shaped nature spaces in Los Angeles.     

Silver accumulation by fungi

32 species of wild mushrooms were analysed by neutron activation for their silver and eight other trace element contents (Ag, Au, As, Cd, Cs, Cu, Hg, Se, Zn). In all 9 samples of 6 species of Agaricus, high silver concentrations of 10 to 133 ug.g^?1 (dry weight), median 30 ug.g^?1, were found. Puffballs also contained more silver than other species, and also the edible boletus; i.e. those species known to accumulate Hg and Cd. Gold levels tended to be higher where silver was higher, and resembled concentrations in green plants growing on gold mineralisation. Some fungi can accumulate up to 150 ug.g^?1 of caesium.