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Many abundant plants, invertebrates, and seaweed are clonal, and this allows the formation of high-density aggregations, foraging, and the placement of modules into new space, and rapid rates of expansion. For these species, population density and rates of expansion are functions of recruitment of asexual modules and post-recruitment vegetative growth and survivorship. In this study, we provide the first experimental test of the relative importance of these two processes in determining the abundance of a clonal seaweed using Caulerpa taxifolia, an invasive green alga that spreads rapidly and reaches very high abundance. We asked two main questions: What is the relative importance to abundance (biomass) of vegetative stolon growth and fragment recruitment during expansion of established patches? Does greater fragment recruitment result in greater abundance in established patches? Vegetative growth of stolons underpinned patch expansion. Plots with stolons growing into them always had a greater abundance than plots where stolons were removed, even when fragment recruitment was increased. Greater recruitment only resulted in greater abundance when stolons were absent, a situation analogous to the establishment of new populations. Although post-recruitment processes were more important in determining abundance during patch expansion, there was greater ambient fragment recruitment when stolons were present compared to when they were absent, and as the abundance of C. taxifolia increased, demonstrating an important feedback between stolon growth, abundance, and fragment recruitment. In established patches, greater fragment recruitment over six months (six levels ranging from 0 to 480 recruits x [m.sup.-2] x [mo.sup.-1]) had no effect on biomass. Our experiments demonstrate that the rapid expansion and high abundance of invasive C. taxifolia are underpinned by post-recruitment vegetative growth and, during expansion, by a feedback between vegetative growth and asexual fragmentation. Key words: Caulerpa taxifolia; clonal; fragmentation; invasive species; marine algae; population abundance; recruitment and post-recruitment processes; vegetative growth.

The tropical and subtropical marine green alga Caulerpa taxifolia has invaded several temperate regions throughout the world, including southeastern Australia. In this study, I examined how invasive C. taxifolia from temperate southeastern Australia differed from native C. taxifolia from subtropical Moreton Bay, Australia, in the traits proposed as being important to its invasion success: thallus size and density, levels of asexual reproduction (fragmentation) and total biomass. Against the prediction of a large size for invasive C. taxifolia, native populations from Moreton Bay had larger stolons and fronds than invasive populations. However, invasive populations consistently had much higher densities of stolons, fronds and fragmented fronds; and a greater biomass compared to native populations. Average densities at invasive sites exceeded 4,700 stolons and 9,000 fronds/[m.sup.2] and were as high as 27,000 stolons and 95,000 fronds/[m.sup.2], which are the highest reported for C. taxifolia anywhere. Average densities of fragmented fronds at invasive sites were as high as 6,000/[m.sup.2] and up to 45% of all stolons at invasive sites could be directly linked to asexual recruitment via fragmented fronds. Importantly, at invasive locations there was a strong association between asexual reproduction and abundance demonstrated by positive correlations between the density of fragmented fronds and total biomass. These findings are the first to describe quantitative differences between native and invasive C. taxifolia and to demonstrate a link between the high levels of asexual reproduction and high abundance in invasive populations. Although the causes and consequences of high levels of asexual reproduction remain to be explored, this study suggests that changes in demographic and life-history traits during the invasion by C. taxifolia into temperate habitats may contribute to its success there.

The responses of the different stages of an organism's life-cycle to different environments can have important implications for their persistence in those habitats. The marine intertidal zone is considered among the most stressful of all marine environments, because daily exposure at low tide results in daily fluctuations in a range of important environmental factors. In this study we examined the link between daytime exposure and the performance of embryos, juveniles and adults of the seaweed Fucus gardneri across zones and seasons on San Juan Island, Washington, USA. Specifically we asked: (1) whether three measures of performance for F. gardneri: growth rates, surface area of reproductive tissue and survivorship differed between high- and mid-intertidal zones, and among months throughout the year and, then, (2) whether total daytime exposure within each zone each month was a good predictor of variation in these measures of performance. At our study site, seasonal differences in the timing of low tides result in long periods each day during summer of very harsh conditions (exposure to the air, high temperatures and low humidity) compared to winter when exposure to the air during the day is virtually absent. Contrary to the expectation of lower performance in the high zone, we found no consistent differences between zones over the entire year in any measure of performance for any stage. For nearly all traits, there were significant differences among months and, importantly, significant interactions between zone and month. Thus, for each stage there were some months when thalli in the high zone performed better and some months when thalli in the mid-zone performed better. Regressions between total daytime exposure and performance each month indicated some stage-specific effects. Larger thalli appeared more strongly affected by the amount of exposure per month; there were significant negative relationships between total daytime exposure and (1) growth rates of medium and large adults in the high zone and (2) the surface area of reproductive tissue of medium adults in the high zone and small adults in the mid-zone. The lowest survivorship for all stages occurred in the 2-3 months that followed summer, suggesting a cumulative effect of long daytime exposure in summer on survivorship. Post-settlement survivorship of embryos was very low throughout the year, with only 2 out of 5395 seeded zygotes surviving to a visible size. One-month post-settlement survivorship ranged from 0% to 16.7%, and there were no differences in the survivorship curves between high- and mid-intertidal zones for each cohort. Although it is often assumed that the performance of intertidal species is lower in high-intertidal zones because of exposure to environmental extremes for longer, our results do not support this paradigm. Instead, they indicate a complex and fluctuating pattern of variation in the performance of different stages of the F. gardneri lifecycle throughout the year in different intertidal zones.

Herbivores have major impacts on many marine algae and are assumed to have been important forces driving the evolution of algal chemical defenses. However, an evolutionary change in chemical defenses in response to herbivory requires that there is both heritable variation for that trait and a response by herbivores to such variation. The subtidal red alga Delisea pulchra produces four main secondary metabolites (furanones) that vary in concentration at a variety of spatial and temporal scales. Here we determined the heritability of furanone concentrations and then, with a series of feeding experiments, determined how feeding by herbivores associated with D. pulchra varied as a function of nonpolar extract and furanone concentration. Total furanone concentration showed significant broad-sense heritability ([h.sup.2.sub.c] = 0.234), but broad-sense heritability of the four individual furanones varied in magnitude, ranging from 0.058 to 0.321. Compound 3, which is often the most abundant furanone, was the only one of the foul furanones to show significant genetic variation. However, all four furanones were strongly genetically correlated, indicating that selection acting on any one of them will cause a corresponding change in the others. With the exception of the mesograzer gastropod Phasianotrochus eximius, herbivores generally consumed D. pulchra at lower rates compared to other common macroalgae. Macrograzers (sea urchins and large gastropods) were mostly deterred by nonpolar extract that contained levels of furanones that spanned the range of furanone variation in the field. The amphipod Ampithoe ngana was not deterred at the lowest extract concentration, and P. eximius was not deterred by any naturally occurring extract concentration. Compound 3 was deterrent to macrograzers at 3 and 5 mg/g dry mass, but was not deterrent at 1 mg/ g dry mass. Compound 3 was also not deterrent to A. ngana at any of those concentrations. For the most part D. pulchra in the field contains concentrations of furanones that are strongly deterrent to most herbivores. However, at some places and times, furanones do occur at lower concentrations that are not deterrent to herbivores. Given the heritable variation for furanones, when this overlap occurs there is the potential for selection by herbivores for higher concentrations of furanones in D. pulchra. Key words; chemical defense; Delisea pulchra: feeding deterrence; furanones; herbivores; heritability; marine algae; marine plant-herbivore interactions; natural selection; quantitative genetics.

We used random amplified polymorphic DNA (RAPDs) to examine small-scale spatial genetic structure in the red alga Delisea pulchra (Greville) Montagne at two locations near Sydney, Australia. We examined genetic structure among plants at four spatial scales ranging from 2 km apart down to < 50 cm apart between locations, among sites within locations, among quadrats within sites, and among plants within quadrats. Haploid stages of D. pulchra were absent from the populations studied, suggesting that they are maintained through asexual reproduction of diploid plants. Consistent with this, we found that 19 RAPD phenotypes scored in this study had multiple individuals, indicating the presence of clones in these populations. However, there were no RAPD phenotypes common to two locations separated by only 2 km. Analysis of molecular variance revealed that strong genetic differences occurred between plants from these two locations, with 46.3% of the total genetic variation occurring at this scale, most probably reflecting limited gene flow. Within each location, < 25% of the genetic variation was attributable to differences among sites or quadrats, indicating gene flow at those smaller scales. Most of the variation within each location occurred at the smallest spatial scale, among plants within 0.25 [m.sup.2] quadrats. Nonetheless, some pairwise genetic distances ([[PHI].sub.ST]) between sites or quadrats within locations were large, indicating some genetic divergence on smaller scales. Genetic distance was independent of spatial distance within both locations, suggesting that fine-scale differences within locations were most probably caused by variation in fine-scale patterns of water movement or fine-scale natural selection. We assessed the impact of one potential selective agent, grazing sea urchins, on the fine-scale genetic structure of D. pulchra. There was no evidence that grazing by sea urchins affected the genetic structure of D. pulchra. In combination with demographic data, our results indicated that local populations of D. pulchra within locations were relatively open and that fine-scale genetic structure was probably constrained by gene flow. At the larger scale however, strong genetic differentiation indicated little gene flow between locations and restricted dispersal of spores.

The influence of the extracellular matrix (ECM) and ECM components on preadipocyte development was examined in primary cultures of adipose tissue stromal-vascular (S-V) cells. Extracellular matrix derived from Engelbreth-Holm-Swarm (EHS) cells or tumors enhanced several aspects of adipogenesis in vitro. In comparison to uncoated and fibronectin substrata, EHS-ECM substratum markedly increased attachment, spreading, and hypertrophy of preadipocytes while antagonizing spreading of non-preadipocytes. In addition, adipocyte number increased (P < .05) on these substrata despite no increase in total cell number: this resulted in a greater (P < .05) proportion of preadipocytes. These effects of EHS-ECM were also observed with laminin substrata per se, whereas types I and IV collagen and fibronectin had no influence. In contrast to all other substrata, adipocyte number decreased and total cell number increased 2.5-fold on ECM derived from corneal endothelial cells; this resulted in the lowest proportion of preadipocytes. Challenging cultures with adipogenic media (+serum) did not counter the inhibitory influence of corneal endothelial ECM, whereas dexamethasone partially neutralized the inhibitory influence of this ECM. These studies clearly show that source or type of the ECM dictated the influence of ECM substrata on preadipocyte development in primary S-V cultures. However, these studies indicated that the ECM and in particular laminin may play a critical role in morphological aspects of preadipocyte development. Key Words: Adipocytes, Extracellular Matrix, Differentiation, Tissue Culture

Fetal hypophysectomy (hypox) slightly enhances lipid accretion in adipose tissue and markedly increases fat cell size and de novo lipogenesis. Thyroxine ([T.sub.4]) treatment (14 to 20 d) had no influence on fat cell size but markedly increased lipogenesis, lipid accretion, and apparent fat cell number in hypox fetuses. Although vascular development is intimately associated with preadipocyte development in the fetus, little is known concerning the regulation of vascular development per se by [T.sub.4] and other adipogenic hormones. Therefore, the purpose of the present study was to evaluate the development of qualitative traits of the adipocyte-associated vasculature after fetal hypox with and without [T.sub.4] treatment. Type IV collagen immunoreactivity of and lectin binding by capillaries in large fat cell clusters was reduced by hypox, and binding of the soybean agglutinin lectin was completely lost. Reactivity for cytosolic markers in capillaries was also reduced by fetal hypox. These blood vessel traits were not influenced by [T.sub.4] treatment. The quantitative aspects of capillary development in large fat cell clusters were not influenced by hypox or [T.sub.4] treatment. On a qualitative basis, blood vessels in the skin and in small fat cell clusters were not affected by hypox. Lectin binding by adipocytes was enhanced by hypox regardless of the size of clusters, and [T.sub.4] augmented this response to hypox. These studies demonstrate that endocrine regulation of the differentiation of the adipocyte-associated vasculature is more complex than the endocrine regulation of adipocyte differentiation per se. Key Words: Fetus, Hypophysectomy, Capillaries, Adipocytes, Cytochemistry

The objective of this study was to determine whether AIMAX (a dithiocarbamoylhydrazine derivative) is suitable for determining the effects of norepinephrine (NE) depletion on reproduction in domestic animals. Therefore, the effect of AIMAX (n = 6) on concentrations of biogenic amines in the medial basal hypothalamus (MBH) and anterior hypothalamic area (AHA) of ovariectomized (OVX) rats primed with ovarian steroids was compared to that of diethyldithiocarbamate (DDC; n = 5), a potent dopamine-beta-hydroxylase (DBH) inhibitor, which is chemically similar to AIMAX. Rats that received only ovarian steroids and saline injections served as controls (n = 6). Treatment with DDC resulted in sedation and reduced body temperature. In contrast, rats behaved normally after AIMAX treatment. AIMAX reduced (P < .05) NE but increased (P < .05) dopamine (DA) concentrations in MBH and AHA compared with controls. Similar changes in NE and DA concentrations were observed in DDC-treated rats. However, elevated epinephrine (EPI) levels were measured in MBH and AHA of only DDC-treated rats. Serum LH concentrations were suppressed (P < .005) in both AIMAX- and DDC-treated rats compared with control animals. Because AIMAX, like DDC, suppressed hypothalamic NE content and LH secretion, AIMAX should be useful in studying effects of NE depletion on gonadotropin secretion in domestic animals. Key Words: Hypothalamus, Catecholamines, AIMAX, Rats

In the present study, a technique is described for measuring proliferation of primary porcine preadipocytes. Cultures of stromal-vascular (S-V) cells from dorsal subcutaneous adipose tissue were maintained under several growth conditions. Cells were isolated from cultures at various times and DNA was labeled with propidium iodide (PI) and analyzed by flow cytometry. Treatment of cultures with colchicine allowed identification of S-V cells in mitosis. The relative proportion of replicating cells was dependent on several factors, including serum concentration and cell density at the time of harvest. Using the AD-1 anti-preadipocyte/adipocyte monoclonal antibody, the preadipocyte subpopulation within the S-V cells was identified. Furthermore, by labeling cells with PI concomitant with AD-1, the proportion of replicating preadipocytes was quantified. It is now possible to identify and quantify replicating preadipocytes rapidly under various experimental conditions.

: Hypophysectomy of the pig fetus alters the number of fat cells and fat cell clusters as well as lipogenic enzyme activities in tissues compared with littermate controls. The objective of the present study was to determine whether the altered endocrine environment in vivo affected subsequent development and differentiation of preadipocytes in vitro. Hypophysectomy was performed in utero at 70 d of gestation. At 105 d of gestation, stromal-vascular cells from dorsal subcutaneous adipose tissues were cultured in several differentiation media. Overall, stromal-vascular cultures from hypophysectomized fetuses contained fewer fat cell clusters and concomitantly lower glycerol-3-phosphate dehydrogenase specific enzyme activity than did cultures from littermate controls. Fluorescence-activated flow cytometry using a monoclonal anti-adipocyte/preadipocyte antibody designated AD-1 revealed that hypophysectomy also reduced the proportion of cells expressing the AD-1 cell surface antigen. These results demonstrated that effects of fetal hypophysectomy on cells from adipose tissues are maintained and measurable in culture. In addition, one of the consequences of fetal hypophysectomy may be diminution in the relative proportion of adipocyte precursors. Key Words: Adipocytes, Hypophysectomy, Differentiation, Pigs, Fetus, Flow Cytometry