Allelic inheritance in naturally occurring parthenogenetic offspring of the gonochoric sea star Patiria miniata

Abstract. In laboratory studies of fertilization using the gonochoric broadcast-spawning asterinid sea star Patiria miniata , we found many cases in which some mature eggs spawned by females formed cleavage-stage embryos and feeding bipinnaria larvae without fertilization by sperm. Segregation of maternal microsatellite alleles among the parthenogenetic offspring of known heterozygous females was consistent with several specific modes of asexual reproduction, including polar body suppression. Cryptic outcrossing by sperm contamination was ruled out by the failure to observe non-maternal alleles. The potential for asexual reproduction by the normally outcrossing members of P. miniata may suggest a shared propensity for asexuality among asterinid species from several clades in which isolated adults can produce offspring without outcrossing.     

Electron microscopy of extracellular materials during the development of a sea star,Patiria miniata (Echinodermata: Asteroidea)

The fine structure of conspicuous extracellular materials during the life history of a sea star (Patiria miniata) is described. The outer surface of the developing sea star is covered by two morphologically different cuticles that appear sequentially during ontogeny. The primary cuticle, which is about 120 nm thick and two-layered, is present from mid-blastula through the end of the larval stage. The secondary cuticle, which is about 1 micron thick and three-layered, first appears on the epidermis of the rudiment region of the larva and, after metamorphosis, covers the entire epidermis of the juvenile and adult stages. During ontogeny, there are only two conspicuous gut cuticles: the first lines the newly invaginated archenteron at the start of the gastrula stage, and the second lines the esophagus during the larval stage. A blastocoelic basal lamina first appears at mid-blastula and persists as subectodermal and subendodermal basal laminae. Ruthenium red-positive granules are detectable between the lateral surfaces of adjacent ectodermal cells during part of the gastrula stage; this transient intercellular material may possibly aid in lateral adhesion between cells.     

Predation by Patiria miniata (Asteroidea) on bryozoans: Prey diversity may depend on the mechanism of succession

Summary In environments where frequent disturbances interrupt the successional process there will usually be many patches of habitat at intermediate stages of succession. It is then relevant to consider the factors which control local diversity during succession. In offshore kelp forests across the whole Southern Californian Bight settlement panels were rapidly colonised by two species of cyclostome bryozoans (Tubulipora tuba and T. pacifica); but cheilostome bryozoans eventually became dominant during succession because they were able to grow over Tubulipora spp. When abundant, Tubulipora spp. were apparently able to reduce the number of colonies, and hence the number of species, of cheilostome bryozoans settling on the panels. Thus the rapid colonisers may delay the process of succession and reduce the diversity of bryozoans during succession. In field and laboratory experiments we found that the asteroid Patiria miniata preys on Tubulipora spp. but not on cheilostome bryozoans. The predator speeds up the successional process and increases bryozoan diversity by reducing the cover of Tubulipora spp. Other ways in which predators may influence diversity during succession are discussed. The effect of predation may depend on the abundance of the prey and the mechanism of succession.     

Pinocytosis of Ferritin from the Gut Lumen in Larvae of a Sea Star (Patiria miniata) and a Sea Urchin (Lytechinus pictus)

Pinocytosis of macromolecules from the gut lumen is demonstrated for the first time in larval stages of invertebrates. Developing sea stars ( Patiria miniata ) and sea urchins ( Lytechinus pictus ) were incubated in seawater containing ferritin, which was detected in cell organelles by transmission electron microscopy. Pinocytotic uptake of ferritin by gut cells of Patiria could be detected as soon as the larval mouth opened before the esophagus, stomach and intestine could be distinguished from one another; in contrast, no pinocytosis was detected at the comparable developmental stage (the prism larva) of Lytechinus . Pinocytosis was first detected in developing Lytechinus in pluteus larvae, especially in the stomach and intestine. In gut cells of both kinds of echinoderm larvae, the ferritin progressed rapidly from coated pits at the luminal cell membrane to secondary lysosomes (e.g. this progression took only about 10 min in stomach cells of Patiria larvae). Phagocytosis from the gut lumen was never observed after latex beads or starch granules were fed to larvae of Patiria and Lytechinus . Moreover, there was no evidence of pinocytosis of ferritin or phagocytosis of large particles by epidermal cells of larvae of either species.     

Physico-chemical properties of elastase from the sea star Patiria pectinifera

An elastolytic protease was purified from the hepatopancreas of the sea star Patiria pectinifera with specific activity of 100 units per 1 mg of protein. The molecular mass of the enzyme was estimated to be 30 KD by SDS-polyacrylamide gel electrophoresis. The isoelectric point of the enzyme was shown to be about 7.3 by gel isoelectrofocusing. The pH-dependence of the sea star elastase activity was determined toward Z-Ala-pNA. Values of kKaT and KM were equal to 36 s-1 and 1 mM, respectively. The kinetics of the thermal denaturation of purified elastase was studied at 40 and 60 degrees C. High thermostability and high activity of star elastase permit relying upon successful application of the enzyme in production of different cell cultures.     

An electrophysiological study of the membrane properties of the immature and mature oocyte of the Batstar,Patiria miniata

Immature oocyte membrane properties of a starfish, Patiria miniata, were investigated by microelectrode techniques. The resting membrane potential in artificial seawater (ASW) was ?78.5 ± 6.7 mV (n = 61, inside negative). This was mainly accounted for by a selective permeability to potassium ions. Potassium ion-selective microelectrodes were used to measure intracellular K⁺ ion activity, which was 350 mM. The sodium to potassium permeability ratio was 0.02 ± 0.01 (n = 4). The current-voltage relation was nonlinear. The I–V curve included both areas of inward and outward rectification. The dependence of inward rectification upon the K⁺ ion electrochemical gradient was demonstrated. The membrane was capable of a regenerative action potential due to permeability changes for Ca²⁺ and Na⁺ ions. The Ca and Na components of the action potential were identified. The Ca component was reversibly suppressed by cobalt and irreversibly blocked by D-600. The Na component was tetrodotoxin (TTX) insensitive. The excitable response of P. miniata oocytes is similar to that described by Miyazaki et al. (1975a) for those of the starfish Asterina pectinifera.Immature oocytes were stimulated to mature with 10^?5M 1-methyladenine (1-MA) during continuous monitoring of the membrane potential. The resting potential in ASW became more inside negative during maturation. This change of the passive membrane property of the oocyte may be accounted for by the increased selectivity to K⁺ ions. The specific membrane resistance near the resting potential increased from 4.2 ± 1.4 to 21 ± 8.7 kΩ·cm² (n = 15) during maturation, while the specific membrane capacitance decreased slightly from 2 ± 0.5 to 1.7 ± 0.6 μF/cm² (n = 5). Maturation had little effect upon the active membrane properties.     

Comparative postcranial body shape and locomotion in Chlorocebus aethiops and Cercopithecus mitis

Body weight and length, chest girth, and seven postcranial limb segment lengths are compared between two guenon species, Chlorocebus (Cercopithecus) aethiops (vervets) and Cercopithecus mitis (blue monkeys), exhibiting different habitual locomotor preferences. The subjects, all adults, were wild caught for a non-related research project (Turner et al. [1986] Genetic and morphological studies on two species of Kenyan monkeys, C. aethiops and C. mitis. In: Else JG, Lee PC, editors. Primate evolution, proceedings of the Xth International Congress of Primatology, Cambridge. London). The morphological results are interpreted within the context of previously published observations of primate locomotion and social organization. The sample is unique in that the body weight of each individual is known, allowing the effects of body-size scaling to be assessed in interspecific and intersexual comparisons. C. mitis has a significantly (P < 0.05) greater body weight and trunk length than C. aethiops. A shorter trunk may function to reduce spinal flexibility for ground-running in the latter. Proximal limb segments (arm and thigh) are significantly greater in C. mitis, reflecting known adaptations to committed arboreal quadrupedal locomotion. By contrast, relative distal limb segments (forearm, crus, and foot) are significantly longer in C. aethiops, concordant with a locomotor repertoire that includes substantial terrestrial quadrupedalism, in addition to arboreal agility, and also the requisite transition between ground and canopy. Although normally associated with arboreal monkeys, greater relative tail length occurs in the more terrestrial vervets. However, because vervets exploit both arboreal and terrestrial habitats, a longer tail may compensate for diminished balance during arboreal quadrupedalism resulting from the greater "brachial" and "crural" indices that enhance their ground quadrupedalism. Most interspecific differences in body proportions are explicable by differences in locomotor modalities. Some results, however, contradict commonly held "tenets" that relate body size and morphology exclusively to locomotion. Generally associated with terrestriality, sexual dimorphism (male/female) is greater in the more arboreal blue monkeys. A more intense, seasonal mating competition may account for this incongruity.     

Ecogeographic variation in body size and shape of Cape sparrows (Passer melanurus) in southern Africa

Canonical discriminant analyses were used to assess whether four populations of Cape sparrows varied in body size and shape according to predictions from Bergmann's Rule. In accordance with Bergmann's Rule, birds from two hot, arid Namib desert sites (Namib 1 and Namib 2) were smaller than birds from two cool, mesic Transvaal sites. If heat dissipation through extremities (tarsi) is important to reduce water lost from evaporative cooling, birds under hot conditions in dry environments (Namib 2) should have longer tarsi than those in more humid hot environments (Namib 1). Contrary to this, males at Namib 2 had relatively longer wings hut shorter tarsi than at Namib 1, and female relative tarsus length did not vary between desert sites     

Assessing metabolic constraints on the maximum body size of actinopterygians: locomotion energetics of Leedsichthys problematicus (Actinopterygii,Pachycormiformes)

Maximum sizes attained by living actinopterygians are much smaller than those reached by chondrichthyans. Several factors, including the high metabolic requirements of bony fishes, have been proposed as possible body‐size constraints but no empirical approaches exist. Remarkably, fossil evidence has rarely been considered despite some extinct actinopterygians reaching sizes comparable to those of the largest living sharks. Here, we have assessed the locomotion energetics of Leedsichthys problematicus, an extinct gigantic suspension‐feeder and the largest actinopterygian ever known, shedding light on the metabolic limits of body size in actinopterygians and the possible underlying factors that drove the gigantism in pachycormiforms. Phylogenetic generalized least squares analyses and power performance curves established in living fishes were used to infer the metabolic budget and locomotion cost of L. problematicus in a wide range of scenarios. Our approach predicts that specimens weighing up to 44.9 tonnes would have been energetically viable and suggests that similar body sizes could also be possible among living taxa, discarding metabolic factors as likely body size constraints in actinopterygians. Other aspects, such as the high degree of endoskeletal ossification, oviparity, indirect development or the establishment of other large suspension‐feeders, could have hindered the evolution of gigantism among post‐Mesozoic ray‐finned fish groups. From this perspective, the evolution of anatomical innovations that allowed the transition towards a suspension‐feeding lifestyle in medium‐sized pachycormiforms and the emergence of ecological opportunity during the Mesozoic are proposed as the most likely factors for promoting the acquisition of gigantism in this successful lineage of actinopterygians.     

Functional and ecological relevance of intraspecific variation in body size and shape in the lizard Podarcis melisellensis (Lacertidae)

Within populations, individual animals may vary considerably in morphology and ecology. The degree to which variation in morphology is related to ecological variation within a population remains largely unexplored. We investigated whether variation in body size and shape among sexes and age classes of the lizard Podarcis melisellensis translates in differential whole-animal performance (sprint speed, bite force), escape and prey attack behaviour in the field, microhabitat use and diet. Male and female adult lizards differed significantly in body size and head and limb proportions. These morphological differences were reflected in differences in bite strength, but not in sprint speed. Accordingly, field measurements of escape behaviour and prey attack speed did not differ between the sexes, but males ate larger, harder and faster prey than females. In addition to differences in body size, juveniles diverged from adults in relative limb and head dimensions. These shape differences may explain the relatively high sprint and bite capacities of juvenile lizards. Ontogenetic variation in morphology and performance is strongly reflected in the behaviour and ecology in the field, with juveniles differing from adults in aspects of their microhabitat use, escape behaviour and diet.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 251–264.     

Effects of galanin-like peptide (GALP) on locomotion, reproduction, and body weight in female and male mice

Galanin-like peptide (GALP) has been implicated in the neuroendocrine regulation of both feeding and reproduction. In male rodents and primates, intracerebroventricular (icv) infusions of GALP stimulate luteinizing hormone (LH) release, induce Fos expression in brain areas implicated in feeding and reproduction, and affect food intake and body weight in rodents. In gonad-intact and castrated male rats, icv administration of GALP also stimulates male sexual behavior. While the effects of GALP on male physiology and behavior are well documented, no studies have addressed such a role of GALP in females. We tested the effects of icv GALP infusions on LH release, locomotor activity, motor control, and body weight regulation in adult ovariectomized female mice hormonally primed with estradiol benzoate and progesterone. In addition, sexually-experienced male and female mice were treated with GALP and tested for sexual behavior. In females, GALP reduced open-field locomotor activity, the ability to maintain grip on an accelerating rotarod, and 24-h body weight in a dose-dependent manner. GALP also increased LH secretion in female mice, an effect that was blocked by pre-treatment with Antide, a gonadotropin-releasing hormone (GnRH) type-1 receptor antagonist. GALP infusions slightly decreased the occurrence of lordosis behavior in female mice and significantly increased the latencies with which females displayed receptivity. Unlike previous reports in male rats, GALP inhibited male sexual behavior in mice. Our data indicate that in female mice, GALP stimulates LH release via GnRH, and decreases body weight, motor control, and locomotor activity via GnRH-independent pathways. Furthermore, our sexual behavior and locomotor findings suggest species-specific differences in the mechanism and/or location of GALP action in the brains of rats and mice.     

Effects of the myosin inhibitor 2,3-butanedione monoxime (BDM) on cell shape, locomotion and fluid pinocytosis in human polymorphonuclear leucocytes

We investigated the role of myosin in polymorphonuclear leucocyte (PMN) shape changes, locomotion, and fluid pinocytosis using the myosin inhibitor 2,3 butanedione monoxime (BDM). Treatment of resting spherical PMNs with BDM produced spheroid cells showing small continuous shape changes (IC(50)=15.5 m m BDM) and occasionally small blebs. Cell polarity, as induced by the chemotactic peptide fNLPNTL or by colchicine, and locomotion were completely suppressed (IC(50)=8.4 to 10 m m). Suppression of fNLPNTL- or colchicine-induced cell polarity produced spheroid cells, suppression of PMA-induced shape changes and fluid pinocytosis produced non-motile spherical cells (IC(50)=25 to 30 m m BDM). BDM suppressed formation of lamellipodia but not formation of blebs. Suppression of microvilli by BDM as observed in resting spherical cells was partially antagonized by PMA. The results suggest that myosin is involved in stabilizing the shape of resting spherical cells, including microvilli, and that myosin is required for cell polarity, locomotion, fluid pinocytosis and for formation of lamellipodia, but not for formation of blebs.     

Clinal variation in body size and sexual dimorphism in an Indian fruit bat, Cynopterus sphinx (Chiroptera: Pteropodidae)

Geographic variation in body size and sexual dimorphism of the short‐nosed fruit bat (Cynopterus sphinx) was investigated in peninsular India. Bats were sampled at 12 localities along a 1200 km latitudinal transect that paralleled the eastern flanks of the Western Ghats. The geographic pattern of variation in external morphology of C. sphinx conforms to the predictions of Bergmann's Rule, as indicated by a steep, monotonic cline of increasing body size from south to north. This study represents one of the first conclusively documented examples of Bergmann's Rule in a tropical mammal and confirms that latitudinal clines in body size are not exclusively restricted to temperate zone homeotherms. Body size was indexed by a multivariate axis derived from principal components analysis of linear measurements that summarize body and wing dimensions. Additionally, length of forearm was used as a univariate index of structural size to examine geographic variation in a more inclusive sample of bats across the latitudinal transect. Multivariate and univariate size metrics were strongly and positively correlated with body mass, and exhibited highly concordant patterns of clinal variation. Stepwise multiple regression on climatological variables revealed that increasing size of male and female C. sphinx was associated with decreasing minimum temperature, increasing relative humidity, and increasing seasonality. Although patterns of geographic size variation were highly concordant between the sexes, C. sphinx also exhibited a latitudinal cline in the magnitude and direction of sexual size dimorphism. The size differential reversed direction across the latitudinal gradient, as males averaged larger in the north, and females averaged larger in the south. The degree of female‐biased size dimorphism across the transect was negatively correlated with body size of both sexes. Canonical discriminant analysis revealed that male‐ and female‐biased size dimorphism were based on contrasting sets of external characters. Available data on geographic variation in the degree of polygyny in C. sphinx suggests that sexual selection on male size may play a role in determining the geographic pattern of sexual size dimorphism.     

Observations of novel locomotion in the sea star Luidia senegalensis (Lamark, 1816) (Asteroidea: Paxillosida)

During abundance surveys of the nine-armed sea star Luidia senegalensis (Lamark, 1816) in shallow waters north of Cubagua Island, Venezuela, novel locomotive behaviour was recorded in one sea star. The animal was observed to ‘walk’ with four arms in contact with the benthos whilst the remaining five were held erect. This previously unreported means of locomotion may be: for chemosensory detection of the surroundings; to alter the characteristic track pattern left in sediments as a means to avoid detection by predators; or, to lift the arms to attract commensal cleaners, thus eliminating epibiont commensals that may occupy the ambulacral groove. Whilst the predators of L. senegalensis remain unknown, earlier observations of serranid fish biting this species may support the notion of this behaviour as a predator avoidance strategy.     

Sexual dimorphism of body size and shell shape in European tortoises

Adult body size and shape were examined in almost 1400 individuals of the tortoises Testudo graeca , T. hermanni and T. marginata from Greece. The size at maturity was greater in females than in males in all three species. Maximum and mean adult sizes were also greater in females than in males in T. graeca and T. hermanni . Males grew to a larger size than females in T. marginata , and mean adult size was similar in the sexes in this species. Sexual dimorphism of shape (adjusted for size covariate) was shown in most of the characters examined, and the degree of this dimorphism differed significantly among the three species. Differences were related to their contrasting courtship behaviours: horizontal head movements and severe biting in T. marginata , vertical head bobs and carapace butting in T. graeca , and mounting and tail thrusting in T. hermanni . There was no difference in the frequency of observations of courtship or fighting among the three species, but courtship was about 10 times more common than combat in males. All species showed greatest courtship activity in autumn; copulation was rarely observed in T. hermanni (only 0.36% of courting males) and not seen in the other species in the field. Observations made throughout the activity season indicated that feeding was equally common in males and females in all three species. Differences in shape were more likely to be the result of sexual selection than of natural selection for fecundity. Detailed predictions are made for sexual dimorphism of other characters in these species.