Physiological energetics of the ascidian Styela clava in relation to body size and temperature

The ascidian Styela clava is widely distributed in northern China and is thought to be important in the functioning of estuarine systems. This ascidian may experience highly variable physiological conditions, and its physiological responses to these are of interest considering its ecological role. This study presents data on the physiological parameters in relation to body size and temperature (12-28 degrees C) of S. clava. Respiration, excretion, feces, ingestion and absorption energy were positive related to size and its mass exponents (b-values) varied from 0.2930 to 0.7488. Respiration energy increased with increasing, but critical values were found at 20 degrees C for energy of ingestion and absorption, while 24 degrees C for energy in feces and excretion. At the range of 16-24 degrees C, the scope for growth, gross and net growth efficiencies of ascidians increased with increasing temperature. The energy budget equations of different sized ascidians were obtained at different temperatures. Excretion energy shared a minimal fraction in ingestion energy (1.30-2.47%), the ratios of feces energy and respiration energy to ingestion energy were 46.53-64.27% and 10.26-80.75%, respectively. The physiological data obtained in the present study indicated that S. clava could adjust its energy budget according to the environment and its physiological conditions to meet their nutritional and energetic demands. In the range of experimental temperature (12-28 degrees C), 16-20 degrees C was suitable for the rearing of S. clava to achieve optimum development, while deficient metabolic adjustment induced a negative scope for growth of S. clava at 28 degrees C.     

Calcitonin-like cells in the pharynx of the ascidian Styela clava

Summary A small group of granulated endocrine cells have been described in the endostylar region of the pharynx in Styela. These cells are argyrophilic and exhibit calcitonin-like immunofluorescence. Tests with antisera to other peptides all proved negative. Cells from animals exposed to elevated calcium levels showed a degree of degranulation. The possibility that these cells may represent ancestral ultimobranchial C cells is discussed.The authors are very grateful to Julia Polak and Susan Van Noorden, Royal Postgraduate Medical School, London, for the kind gift of all antisera used. Animals were collected by courtesy of Mr. David Houghton and his staff of the Admiralty Marine Trials Station, Portsmouth. This research was carried out during the tenure of SRC grant no. B/RG 82919 to one of us (M.C.T.) — The localization of polypeptide hormones in the pharynx and gut of protochordates     

Endocrine cells in the gut of the ascidian Styela clava

Summary Ultrastructural studies have shown the presence of two types of granulated endocrine cell in the gut of Styela clava. Type I, which occurs in the stomach and intestine contains small irregular granules, each with a distinct halo. Type II, found only in the oesophagus contains larger rounded granules, often with little or no halo. The characteristics of these two cell types are compared with those of endocrine cells found in the digestive tracts of other protochordates and discussed with special reference to the evolution of gastrointestinal endocrine cells in vertebrates.The authors are grateful to Mr. R. Jones for photographic assistance. Animals were collected by courtesy of the Admiralty Marine Trials Station, Portsmouth, This research was carried out during the tenure of S.R.C. grant no. B/RG 82919 to one of us (M.C.T.). The localization of polypeptide hormones in the pharynx and gut of protochordates     

Global phylogeography of the widely introduced North West Pacific ascidian Styela clava

The solitary ascidian Styela clava Herdman, 1882 is considered to be native to Japan, Korea, northern China and the Russian Federation in the NW Pacific, but it has spread globally over the last 80 years and is now established as an introduced species on the east and west coasts of North America, Europe, Australia and New Zealand. In eastern Canada it reaches sufficient density to be a serious pest to aquaculture concerns. We sequenced a fragment of the cytochrome oxidase subunit I mitochondrial gene (COI) from a total of 554 individuals to examine the genetic relationships of 20 S. clava populations sampled throughout the introduced and native ranges, in order to investigate invasive population characteristics. The data presented here show a moderate level of genetic diversity throughout the northern hemisphere. The southern hemisphere (particularly New Zealand) displays a greater amount of haplotype and nucleotide diversity in comparison. This species, like many other invasive species, shows a range of genetic diversities among introduced populations independent of the age of incursion. The successful establishment of this species appears to be associated with multiple incursions in many locations, while other locations appear to have experienced rapid expansion from a potentially small population with reduced genetic diversity. These contrasting patterns create difficulties when attempting to manage and mitigate a species that continues to spread among ports and marinas around the world.     

A cytochemical and immunofluorescence study of endocrine cells in the gut of the ascidian Styela clava

Summary Strong secretin-like immunofluorescence has been demonstrated in endocrine-like cells from the gastric epithelium of Styela. These cells also stain with lead haematoxylin and exhibit a brilliant formaldehyde-induced fluorescence, but do not show any other cytochemical features characteristic of the mammalian APUD series. Tests with antisera to glucagon, gastrin and somatostatin all proved negative. In the oesophagus tests with all four antisera proved negative. The significance of these results is discussed in relation to the phylogeny of vertebrate gastro-intestinal hormones.     

Isolation and characterization of twelve polymorphic microsatellite markers for the invasive ascidian Styela clava (Tunicata)

The invasive solitary ascidian Styela clava has spread extensively along European coasts since its first occurrence in the early 1950s. In order to characterize spatial and temporal patterns of genetic change during its establishment and subsequent spread, we developed 12 species‐specific loci from an enriched microsatellite library. Polymorphism was explored in one native and two introduced populations (N = 31 ± 1). Number of alleles per locus varied from two to 13 (mean = 7). The average expected heterozygosity within populations ranged from 0.539 to 0.580.     

Tolerance of the invasive tunicate Styela clava to air exposure

Styela clava is a subtidal invasive marine species in Northern Europe, Atlantic Canada, Australia and New Zealand. It grows attached to solid substrata, including boat hulls, ropes, moorings, piers and aquaculture equipment, all of which can aid its spread to new locations. It interferes with feeding of mussels and oysters, and increases their harvesting costs. Being subtidal, it could be assumed that tunicates would rapidly die in air and thus exposure to air would be a practical method to prevent their spread on boats and equipment. This study tested their survival when exposed to air for up to (1) 120?h at a constant temperature of 10?°C, (2) shade ambient 15–27?°C, and (3) full sun ambient 15–29?°C. Humidity was consistently high (78–100%). The results indicated that survival was longer when the air temperature was cooler. Larger individuals of S. clava generally survived for longer out of seawater than smaller individuals. The results predict that two weeks of exposure to air for two weeks could be an effective management method to eradicate S. clava from marine equipment when the air temperature is 10?°C. However, drying time would be less under conditions of low humidity and under direct sunlight.     

Effect of the ascidian Styela clava on the growth of small holothurians of the species Apostichopus japonicus

We studied the effect of the common ascidian Styela clava on the growth of small holothurians of the species Apostichopus japonicus (Selenka, 1867). In a traditional aquaculture system, the oxygen consumption rates, ammonia excretion rates, and ingestion rates of small A. japonicus were reduced significantly, which suggested that this group was stressed by the presence of large A. japonicus, and that this stress grew stronger with time. Oxygen consumption rates, ammonia excretion rates, and ingestion rates of small A. japonicus in an integrated aquaculture (IA) system with S. clava, microalgae, and A. japonicus were higher than those observed in the traditional culture system. Metabolic and digestive enzymes were more active in small A. japonicus in the IA system than in those in the traditional aquaculture system. These results suggest that the IA model did not affect the growth of large A. japonicas, but produced a marked positive impact on the growth of small individuals.     

In vitro allogeneic cytotoxicity in the solitary urochordate Styela clava.

Hemocytes from the solitary urochordate Styela clava can effect allogeneic cytotoxicity in vitro. Spectrophotometric and microscopic quantification of eosin-y dye exclusion revealed significantly greater frequencies of cell death in allogeneic hemocyte cultures when compared to autogeneic controls. This cytotoxic response was characterized by 1) transient activity such that specific cytotoxicity could be detected for only 4 hours of culture though continued specific killing may have been obscured by spontaneous cell death; 2) a necessity for cellular interaction demonstrated by the elimination of allogeneic cytotoxicity in the absence of cell contact; 3) killing of multiple targets by effector cells due to high levels of response at low allogeneic ratios; 4) insensitivity to altered temperature; 5) increased cytotoxicity in the absence of autologous plasma; 6) an absence of xenogeneic reactivity; 7) the presence of three hierarchical levels (low, intermediate, and high) of response. These data reflect events involved in the recognition of allogeneic cellular determinants resulting in specific cytotoxicity effected by immunocompetent cells. Such in vitro recognition and cytotoxic recognition and cytotoxic reactivity may be responsible for adaptive reactions caused by histoincompatibility in solitary tunicates.     

Purification and characterization of a humoral opsonin from the solitary urochordate Styela clava.

1. We have previously identified opsonic activity in the plasma of the solitary urochordate, Styela clava. 2. Here, we report the purification and further characterization of the opsonic molecule. 3. Two purification methods were employed. 4. Gel filtration yielded one strongly opsonic fraction that contained a single, electrophoretically-resolved protein. 5. Opsonic activity was dose-dependent and sensitive to tryptic digestion and heat denaturation. 6. SDS-PAGE and calibrated gel filtration indicated the opsonic protein was a 17.5 kDa monomer while isoelectrofocusing indicated a single pI of 7.0. 7. In an alternative procedure, a similar opsonic activity and protein were isolated by affinity purification using whole yeast cells.     

Protochordate immunity--II. Diverse hemolymph lectins in the solitary tunicate Styela clava

Hemolymph lectins (agglutinins) of the tunicate Styela clava were analyzed by agglutination, cross-absorption and carbohydrate-hemagglutination inhibition using several vertebrate erythrocytes. Lectin activity was heat labile, dependent on divalent cations and refractory to neuraminidase-treated erythrocytes. Four lectins with different carbohydrate specificities were found. Carbohydrate specificities included L-rhamnose, D-glucuronolactone, maltose, D-galactosamine, D-mannosamine, D-galactose, hyaluronic acid and bacterial lipopolysaccharide. Since S. clava lectins can be inhibited by carbohydrates found in the extracellular capsule or cell wall of most bacteria, we propose that the lectins may be part of the tunicate immuno-defense system.     

Clavaspirin, an antibacterial and haemolytic peptide from Styela clava.

We cloned the precursor of a novel peptide from a cDNA library prepared from pharyngeal tissues of the tunicate, Styela clava. Its sequence predicted a histidine-rich, amidated 23-residue peptide (FLRF(IG)SVIHGIGHLVHHIGVAL-NH2) that we named clavaspirin. A synthetic clavaspirin was prepared and it was found that it killed Gram-positive and Gram-negative bacteria, permeabilized the outer and inner membranes of Escherichia coli, lysed phosphatidylglycerol (POPG) liposomes, and was potently haemolytic towards human and bovine erythrocytes. Each of these activities was performed more effectively at an acidic pH. Circular dichroism measurements of synthetic clavaspirin revealed a largely alpha-helical structure and polarized and residue-specific FTIR spectrometry showed that its association with phospholipid membranes was influenced by pH. Peptides such as clavaspirin may equip tunicate haemocytes to mediate cytotoxicity and participate in antimicrobial defence.     

The metabolic rate of roach in relation to body size and temperature

Standard and routine metabolic rates of roach Rutilus rutilus for a wide size and temperature range (3–200 g, 5–23° C) were analysed by automated, computerized intermittent flow respirometry. The mass exponent b ranged from 0·68 to 0·82 for standard metabolism, and from 0·65 to 0·92 for routine metabolism depending on the experimental temperature. For routine metabolism b was lowest at 10° C. At both decreasing and increasing temperatures, b increased significantly. Roach were exponentially temperature-dependent for both metabolic levels. For roach <20 g, however, an asymptotic relationship was observed between temperature and routine metabolic rate. The 'flattening of the curve' in the latter case may be explained by reduced spontaneous activities at the lower threshold of the preferred temperature range.     

Observations on the gastric epithelium of ascidians with special reference to Styela clava

Summary Transmission electron microscopy shows the gastric epithelium of Styela clava to comprise at least three distinct cell types. Ciliated mucous cells which form the crest of each stomach ridge produce mucus by an unexpected route. Vacuolated cells lining the ridge sides appear to be absorptive in function. Gastric enzymes are produced by typical protein secreting cells scattered amongst the vacuolated cells. Undifferentiated cells are found in the crypts between ridges. The structure and function of the gastric epithelium in Styela is discussed with special reference to the wider concepts of ascidian gut organization.The author is grateful to Mrs. L. Rolph for technical help with scanning electron microscopy and Mr. J. Calvert and Mr. R. Jones for assistance with the transmission electron microscopy. Animals were collected through the kind offices of Mr. J. Sturges and other staff of the Admiralty Marine Trials Station, Portsmouth. This research was carried out during the tenure of SRC grant No. B/RG 82919 -The localization of polypeptide hormones in the pharynx and gut of Protochordates     

The distribution of neuropeptide Y-like immunoreactivity in the ascidian Styela plicata.

The occurrence of neuropeptide Y-like substances has been verified in the nervous system and alimentary tract of the ascidian Styela plicata. Neuropeptide Y-like immunoreactivity is present in a few small neurons and in a network of beaded nerve fibres of the cerebral ganglion. Neuropeptide Y-like immunoreactive material can be also localized in the endostyle and in a few cell bodies of the branchial walls. Moreover, immunofluorescent endocrine-like cells of the "open" type occur in the gastric folds. Finally, some possible functions of the ascidian neuropeptide Y are discussed.     

Testicle size of orang-utans in relation to body size

Few data are available for assessing the relative testicle size of orang-utans, Pongo pygmaeus, so measures were obtained for 31 individuals of varying age. It was shown that the volume of the testicles, calculated from in situ measures of testicle length and breadth, closely approximates testicle weight when multiplied by the specific gravity of solid tissue. Growth curves for body weight and data published for wild specimens were evaluated to obtain the weight most characteristic of male Pongo, and the ratio of testicle weight to body weight was calculated. The mean ratio for individuals with fully adult stature is 0.034, similar to but smaller than that of humans at about 0.050, and larger than the ratios reported for 5 gorillas at 0.013. The testicles mature faster than the body, however, so the mean ratio for young adult orang-utans is about 0.056 and resembles the ratio for humans more closely than the full adults. The differences between the ratios for a monogamous gibbon species, orang-utans, and humans is accounted for when testicle size relative to the weight of the female is considered. This is consistent with a sperm dilution effect produced by variation in the size of the female reproductive tract. The small relative testicle size of the gorilla is anomalous and requires verification as does the application of female size to scale the testicles. © 1993 Wiley-Liss, Inc.     

Pelvic dimorphism in relation to body size and body size dimorphism in humans

Many mammalian species display sexual dimorphism in the pelvis, where females possess larger dimensions of the obstetric (pelvic) canal than males. This is contrary to the general pattern of body size dimorphism, where males are larger than females. Pelvic dimorphism is often attributed to selection relating to parturition, or as a developmental consequence of secondary sexual differentiation (different allometric growth trajectories of each sex). Among anthropoid primates, species with higher body size dimorphism have higher pelvic dimorphism (in converse directions), which is consistent with an explanation of differential growth trajectories for pelvic dimorphism. This study investigates whether the pattern holds intraspecifically in humans by asking: Do human populations with high body size dimorphism also display high pelvic dimorphism? Previous research demonstrated that in some small-bodied populations, relative pelvic canal size can be larger than in large-bodied populations, while others have suggested that larger-bodied human populations display greater body size dimorphism. Eleven human skeletal samples (total N: male = 229, female = 208) were utilized, representing a range of body sizes and geographical regions. Skeletal measurements of the pelvis and femur were collected and indices of sexual dimorphism for the pelvis and femur were calculated for each sample [ln(M/F)]. Linear regression was used to examine the relationships between indices of pelvic and femoral size dimorphism, and between pelvic dimorphism and female femoral size. Contrary to expectations, the results suggest that pelvic dimorphism in humans is generally not correlated with body size dimorphism or female body size. These results indicate that divergent patterns of dimorphism exist for the pelvis and body size in humans. Implications for the evaluation of the evolution of pelvic dimorphism and rotational childbirth in Homo are considered.