scispace - formally typeset
Search or ask a question

Showing papers in "The Biological Bulletin in 2013"


Journal ArticleDOI
TL;DR: The role that sexual selection, manifested through sperm competition, cryptic female choice, and evolutionary conflicts of interest between the sexes, can also play in mediating the action of egg chemoattractants and GRPs, and thus individual reproductive fitness is emphasized.
Abstract: Many marine invertebrate taxa are broadcast spawners, where multiple individuals release their gametes into the water for external fertilization, often in the presence of gametes from heterospecifics. Consequently, sperm en- counter the considerable challenges of locating and fertiliz- ing eggs from conspecific females. To overcome these chal- lenges, many taxa exhibit species-specific attraction of sperm toward eggs through chemical signals released from eggs (sperm chemotaxis) and species-specific gamete rec- ognition proteins (GRPs) that mediate compatibility of gam- etes at fertilization. In this prospective review, we highlight these selective forces, but also emphasize the role that sexual selection, manifested through sperm competition, cryptic female choice, and evolutionary conflicts of interest between the sexes (sexual conflict), can also play in medi- ating the action of egg chemoattractants and GRPs, and thus individual reproductive fitness. Furthermore, we explore patterns of selection at the level of gametes (sperm pheno- type, gamete plasticity, and egg traits) to identify putative traits targeted by sexual selection in these species. We conclude by emphasizing the excellent, but relatively un- tapped, potential of broadcast-spawning marine inverte- brates as model systems to illuminate several areas of re- search in post-mating sexual selection.

95 citations


Journal ArticleDOI
TL;DR: The impact of the harvest of LAL may decrease female fitness, and thus may contribute to the current population decline, as previously unrecognized behavioral and physiological deficits are found.
Abstract: The hemolymph of the American horseshoe crab, Limulus polyphemus, is harvested from over 500,000 animals annually to produce Limulus amebocyte lysate (LAL), a medically important product used to detect pathogenic bacteria. Declining abundance of spawning Limulus females in heavily harvested regions suggests deleterious effects of this activity, and while mortality rates of the harvest process are known to be 10%-30%, sublethal behavioral and physiological effects are not known. In this study, we determined the impact of the harvest process on locomotion and hemocyanin levels of 28 female horseshoe crabs. While mortality rates after bleeding (18%) were similar to previous studies, we found significant decreases in the linear and angular velocity of freely moving animals, as well as changes in their activity levels and expression of circatidal behavioral rhythms. Further, we found reductions in hemocyanin levels, which may alter immune function and cuticle integrity. These previously unrecognized behavioral and physiological deficits suggest that the harvest of LAL may decrease female fitness, and thus may contribute to the current population decline.

51 citations


Journal ArticleDOI
TL;DR: Sea anemone species richness is complementary to that of scleractinian corals at many scales; the findings affirm it at the global scale.
Abstract: We sought to determine if the global distribution of sea anemones (cnidarian order Actiniaria) conforms to the classic pattern of biogeography—taxon richness at the equator with attenuation toward ...

50 citations


Journal ArticleDOI
TL;DR: Ferulic acid (FA), a natural antioxidant, is tested as a putative AD neuroprotective compound and it is observed that FA is able to reverse morphological defects induced by Aβ oligomers in P. lividus embryos.
Abstract: Alzheimer's disease (AD) is a progressive, neurodegenerative disorder, characterized by loss of memory and impairment of multiple cognitive functions. Amyloid beta peptide (Aβ) is the main component of amyloid plaques observed in the brain of individuals affected by AD. Oxidative stress and mitochondrial dysfunction, induced by Aβ, are among the earliest events in AD, triggering neuronal degeneration and cell death. Use of natural molecules with antioxidant properties could be a suitable strategy for inhibiting the cell death cascade. Here, by employing the sea urchin Paracentrotus lividus as a model system, and Aβ oligomers, we tested the effectiveness of ferulic acid (FA), a natural antioxidant, as a putative AD neuroprotective compound. By microscopic inspection we observed that FA is able to reverse morphological defects induced by Aβ oligomers in P. lividus embryos. In addition, FA is able to neutralize reactive oxygen species (ROS), recover mitochondrial membrane potential, and block apoptotic pathways. Moreover, this model system has allowed us to obtain information about down- or up-regulation of some key molecules--Foxo3a, ERK, and p53--involved in the antioxidant mechanism.

50 citations


Journal ArticleDOI
TL;DR: The results suggest that cuttlefish may vary their behavior in the presence of different teleost predators, while conspicuous movements such as swimming in the water column and startle displays may be more prevalent with relatively sedentary, bottom-associated predators.
Abstract: We evaluated cuttlefish (Sepia officinalis) re- sponses to three teleost predators: bluefish (Pomatomus saltatrix), summer flounder (Paralichthys dentatus), and black seabass (Centropristis striata). We hypothesized that the distinct body shapes, swimming behaviors, and preda- tion tactics exhibited by the three fishes would elicit mark- edly different antipredator responses by cuttlefish. Over the course of 25 predator-prey behavioral trials, 3 primary and 15 secondary defense behaviors of cuttlefish were shown to predators. In contrast, secondary defenses were not shown during control trials in which predators were absent. With seabass—a benthic, sit-and-pursue predator— cuttlefish used flight and spent more time swimming in the water column than with other predators. With bluefish—an active, pelagic searching predator— cuttlefish remained closely as- sociated with the substrate and relied more on cryptic be- haviors. Startle (deimatic) displays were the most frequent secondary defense shown to seabass and bluefish, particu- larly the Dark eye ring and Deimatic spot displays. We were unable to evaluate secondary defenses by cuttlefish to floun- der—a lie-and-wait predator— because flounder did not pursue cuttlefish or make attacks. Nonetheless, cuttlefish used primary defense during flounder trials, alternating be- tween cryptic still and moving behaviors. Overall, our re- sults suggest that cuttlefish may vary their behavior in the presence of different teleost predators: cryptic behaviors may be more important in the presence of active searching predators (e.g., bluefish), while conspicuous movements such as swimming in the water column and startle displays may be more prevalent with relatively sedentary, bottom- associated predators (e.g., seabass).

35 citations


Journal ArticleDOI
TL;DR: The Atlantic blue crab, Callinectes sapidus (Rathbun), is a highly mobile crustacean that must locomote to find food, evade predators, find mates, and avoid adverse conditions such as hypoxia.
Abstract: The Atlantic blue crab, Callinectes sapidus (Rathbun), is a highly mobile crustacean that must locomote to find food, evade predators, find mates, and avoid adverse conditions such as hypoxia. In this study we tested the effects of two levels of hypoxia (10.4 kPa, 50% air saturation = moderate hypoxia; 4 kPa, 20% air saturation = severe hypoxia) and hypercapnic hypoxia (50% air saturation O2 with Pco2 = 2 kPa) on fatigue during sustained continuous exercise. Fatigue was induced by an exercise trial that entailed continuous sideways hexapedal walking on an underwater treadmill. Fatigue was quantified using two methods: (1) a pull force test that measures the holding strength of the legs, and (2) the number of fatigue-resisting behaviors (180° turns and stopping). Fatigue was defined as a pull force of 67% or less of the initial pre-exercise pull force and was reached after 6.12 h of walking for crabs in well-aerated normoxic seawater, 4 h in 50% air saturation, 2.07 h in 20% air saturation, and 4.58 h in 5...

23 citations


Journal ArticleDOI
TL;DR: The overall results suggest that U. rigida extracts protect HeLa cells from death induced by oxidative stress, and it is likely that these effects are related to the phenolic, protein, and polysaccharide compounds contained in this alga.
Abstract: The rising demand for natural antioxidants instead of synthetic materials, especially in biomedical applications, has led to increased interest in the search for bioactive compounds with potent antioxidant activity. In the present study, we tested the antioxidant effect of both a crude extract and an ethanol precipitate of Ulva rigida in HeLa cells exposed to hydrogen peroxide (H₂O₂). HeLa cells treated with H₂O₂ (1 mmol l⁻¹ for 3 h) exhibited significant damage to their morphology, a significant decrease in cell survival, and a remarkable leakage of lactate dehydrogenase (LDH). However, the co-exposure of cells to H₂O₂ and the crude extract or ethanol precipitate of U. rigida induced fewer morphological cytotoxic effects, a significant increase in cell viability, and a significant decrease in LDH release. Biochemical studies have demonstrated that U. rigida extracts have a strong radicalscavenging activity and contain protein, sugar, and phenolic content. The overall results suggest that U. rigida extracts protect HeLa cells from death induced by oxidative stress, and it is likely that these effects are related to the phenolic, protein, and polysaccharide compounds contained in this alga. Hence, U. rigida can be used to treat diseases ascribed to oxidative disorders.

23 citations


Journal ArticleDOI
TL;DR: This work examines species-specificity of sperm motility activation and chemotaxis in the ascidians belonging to the order Phlebobranchiata and finds that there is a “one way” (no reciprocity) cross-reaction between P. mammillata and P. nigra in sperm activation, and between C. savignyi and A. sydneiensis in spermChemotaxis.
Abstract: Egg-derived sperm-activating factors and at- tractants activate sperm motility and attract the sperm, re- spectively. These phenomena constitute the first communi- cation signaling between males and females in the process of fertilization in many animals and plants, and in many cases, these are species-specific events. Thus, sperm motil- ity activation and chemotaxis may act as a safety process for the authentication between conspecific egg and sperm, and help to prevent crossbreeding. Here, we examine species- specificity of sperm motility activation and chemotaxis in the ascidians belonging to the order Phlebobranchiata: Ciona intestinalis, Ciona savignyi, Phallusia mammillata, Phallusia nigra, and Ascidia sydneiensis. Cross-reactivity in both motility activation and chemotaxis of sperm was not observed between C. savignyi and P. mammillata, or be- tween A. sydneiensis and Phallusia spp. However, there is a "one way" (no reciprocity) cross-reaction between P. mam- millata and P. nigra in sperm activation, and between C. savignyi and A. sydneiensis in sperm chemotaxis. Further- more, the level of activity is different, even when cross- reaction is observed. Thus, sperm motility activation and chemotaxis are neither "species-" nor "genus-" specific phe- nomena among the ascidian species. Moreover, the inter- action between the sperm-activating and sperm-attracting factors (SAAFs) in the ascidian species and the SAAF receptors on the sperm cells are not all-or-none responses.

22 citations


Journal ArticleDOI
TL;DR: Novel light-absorbing dichromatic chromatophores are found in limited regions of the integument of the mandarin fish and pharmacological treatment with norepinephrine induced aggregation of both the erythrosomes and cyanosomes of the novel dichromatics possess motile activity, suggesting that they contribute to the role of their color changes observed in response to various environmental signals.
Abstract: The bluish coloration of the integument in teleosts is usually generated by light-reflecting chromatophores, called iridophores, that contain very thin light-reflecting platelets in the cytoplasm. We previously reported, however, that novel light-absorbing chromatophores named “cyanophores” display a bluish hue in the integument of the mandarin fish Synchiropus splendidus and the psychedelic fish S. picturatus. In the present report, we found novel light-absorbing dichromatic chromatophores in limited regions of the integument of the mandarin fish. Light microscopy under transmission optics revealed that the novel dichromatic chromatophores in the dermis around the margins of the bluish regions display both bluish and reddish hues. In the cytoplasm, both erythrosomes and cyanosomes were observed under transmission electron microscopy. The morphological features of the cyanosomes contained in the novel dichromatic chromatophores did not differ from those in the cyanophores in blue regions. Pharmacological treatment with norepinephrine induced aggregation of both the erythrosomes and cyanosomes of the novel dichromatic chromatophores, suggesting that the dichromatic chromatophores possess motile activity, the same as other lightabsorbing chromatophores, which contributes to the role of their color changes observed in response to various environmental signals. The variety of colors, patterns, and spectacular color changes the animals can exhibit is a subject of much interest. The generation of color and color changes is important to many species because it provides protection and assists in survival in their habitats. The delicate changes in hues and patterns can also be used to communicate with conspecifics.

22 citations


Journal ArticleDOI
TL;DR: The data suggest that the evolution of egg size and egg energy content can be decoupled, possibly facilitating response to selective factors such as sperm limitation which could act on volume alone.
Abstract: Marine organisms exhibit substantial life-history diversity, of which egg size is one fundamental parameter. The size of an egg is generally assumed to reflect the amount of energy it contains and the amount of per-offspring maternal investment. Egg size and energy are thought to scale isometrically. We investigated this relationship by updating published datasets for echinoderms, increasing the number of species over those in previous studies by 62%. When we plotted egg energy versus egg size in the updated dataset we found that planktotrophs have a scaling factor significantly lower than 1, demonstrating an overall trend toward lower energy density in larger planktotrophic eggs. By looking within three genera, Echinometra, Strongylocentrotus, and Arbacia, we also found that the scaling exponent differed among taxa, and that in Echinometra, energy density was significantly lower in species with larger eggs. Theoretical models generally assume a strong tradeoff between egg size and fecundity that limits energetic investment and constrains life-history evolution. These data suggest that the evolution of egg size and egg energy content can be decoupled, possibly facilitating response to selective factors such as sperm limitation which could act on volume alone.

21 citations


Journal ArticleDOI
TL;DR: Green-lipped musssels have an aerobic scope of approximately 2-fold, and can reach a higher metabolic rate during feeding than during activity, and the two combined can raise the metabolic rate higher still; and display a marked diurnal behavior.
Abstract: In most animals, significant increases in metabolic rate are due to activity and to feeding (known as apparent specific dynamic action). We determined the energetic costs of activity and feeding in adult green-lipped mussels (Perna canaliculus). Maximal metabolic rate was determined, using closed-chamber respirometry, during byssus re-attachment, during specific dynamic action after 16 h of feeding with Isochrysis galbana, and for the two activities combined, in 23 mussels. Metabolic rate was significantly elevated above rest by about 1.9-fold during byssus attachment (17.1 ± 1.53 μg O(2) h(-1) g(-1) whole mussel wet weight at rest, increased to 27.9 ± 0.91 μg O(2) h(-1) g(-1)), and by 2.2-fold after feeding (31.4 ± 1.20 μg O(2) h(-1) g(-1)). Combined feeding and byssus attachment led to a still higher metabolic rate (34.0 ± 1.23 μg O(2) h(-1) g(-1)). Behavior was also significantly altered, with mussels being almost continuously open during attachment and after feeding (90%-99% of the time); however, the time spent open during the day decreased, reaching a minimum of 52% ± 9% 3 days after feeding, and remained low (67%-82%) for the following 45-day starvation period. Significant diurnal differences were observed, with mussels continuously (92%-100%) open at night. The key findings from this study are that green-lipped mussels (1) have an aerobic scope of approximately 2-fold; (2) reach a higher metabolic rate during feeding than during activity, and the two combined can raise the metabolic rate higher still; (3) display a marked diurnal behavior.

Journal ArticleDOI
TL;DR: A molecular phylogenetic study based on nuclear 18S rDNA sequence data is presented, which includes 35 previously unsampled taxa and represents all recognized hemichordate families and reveals a previously unknown clade of at least four species of harrimaniid enteropneusts from cold waters.
Abstract: Hemichordates are instrumental to understanding early deuterostome and chordate evolution, yet diversity and relationships within the group have been understudied. Recently, there has been renewed interest in hemichordate diversity and taxonomy, although current findings suggest that much hemichordate diversity remains to be discovered. Herein, we present a molecular phylogenetic study based on nuclear 18S rDNA sequence data, which includes 35 previously unsampled taxa and represents all recognized hemichordate families. We include mitochondrial 16S rDNA data from 66 enteropneust taxa and three pterobranch Rhabdopleura species, and recover colonial pterobranchs and solitary enteropneusts as reciprocally monophyletic taxa. Our phylogenetic results also reveal a previously unknown clade of at least four species of harrimaniid enteropneusts from cold waters, including Antarctica, the North Atlantic around Iceland and Norway, and the deep sea off Oregon. These small worms (1-5 mm in length), occur from 130 to 2950 m and are not closely related to other deep-sea harrimaniids, indicating that diversity of enteropneusts within the deep sea is broader than previously described in the literature. Discovery of this clade, as well as larger torquaratorids from Antarctica, strengthens hypotheses of close associations between Antarctic and deep-sea fauna.

Journal ArticleDOI
TL;DR: Investigation of genetic variation, population structure, and evolutionary history of three caridean shrimp species in the Ryukyu Archipelago, Japan implies multiple colonizations of the archipelago by the three species, consistent with the center of accumulation hypothesis.
Abstract: Archipelagos of the Indo-West Pacific are considered to be among the richest in the world in biodiversity, and phylogeographic studies generally support either the center of origin or the center of accumulation hypothesis to explain this pattern. To differentiate between these competing hypotheses for organisms from the Indo-West Pacific anchialine ecosystem, defined as coastal bodies of mixohaline water fluctuating with the tides but having no direct oceanic connections, we investigated the genetic variation, population structure, and evolutionary history of three caridean shrimp species (Antecaridina lauensis, Halocaridinides trigonophthalma, and Metabetaeus minutus) in the Ryukyu Archipelago, Japan. We used two mitochondrial genes—cytochrome c oxidase subunit I (COI) and large ribosomal subunit (16S-rDNA)—complemented with genetic examination of available specimens from the same or closely related species from the Indian and Pacific Oceans. In the Ryukyus, each species encompassed 2–3 divergent (9.52%–...

Journal ArticleDOI
TL;DR: In this article, the authors quantified and compared two mechanical properties of oysters: hardness (resistance to ir- reversible deformation; GPa) and compressive strength (force necessary to produce a crack; N).
Abstract: The valves of oysters act as a physical barrier between tissues and the external environment, thereby pro- tecting the oyster from environmental stress and predation. To better understand differences in shell properties and predation susceptibilities of two physiologically and mor- phologically similar oysters, Crassostrea virginica and Crassostrea ariakensis, we quantified and compared two mechanical properties of shells: hardness (resistance to ir- reversible deformation; GPa) and compressive strength (force necessary to produce a crack; N). We found no differences in the hardness values between foliated layers (innermost and outermost foliated layers), age class (C. virginica: 1, 4, 6, 9 years; C. ariakensis: 4, 6 years), or species. This suggests that the foliated layers have similar properties and are likely composed of the same material. The compressive force required to break wet and dry shells was also not different. However, the shells of both six- and nine-year-old C. virginica withstood higher compressive force than C. virginica shells aged either one or four, and the shells of C. ariakensis at both ages studied (4- and 6-years-old). Differences in ability to withstand compres- sive force are likely explained by differences in thickness and density between age classes and species. Further, we compared the compressive strength of differing ages of these two species to the crushing force of common oyster predators in the Chesapeake Bay. By studying the physical properties of shells, this work may contribute to a better understanding of the mechanical defenses of oysters as well as of their predation vulnerabilities.

Journal ArticleDOI
TL;DR: An ethogram of male reproductive behavior in the most widespread Mediterranean killifish, the South European toothcarp Aphanius fasciatus, suggested that the breeding system is based on mate monopolization, with high levels of sperm competition and parasitic spawning.
Abstract: This work provides an ethogram of male reproductive behavior in the most widespread Mediterranean killifish, the South European toothcarp Aphanius fasciatus. The ethogram was obtained by video-recording the behavior of breeding groups under aquarium conditions. The behavioral analysis revealed the existence of seven behavioral states, with the expression of different forms of male-male competition: single and multiple courtship, single and multiple spawning, aggression, homosexual courtship, and post-mating cannibalism. These behaviors were organized into sequences that followed a first-order Markov chain. Single courtship was the most prevalent behavior, but more than one male, from two to five, could participate simultaneously in courtship and spawning. Results suggested that the breeding system is based on mate monopolization, with high levels of sperm competition and parasitic spawning. Results are discussed in light of the current literature on alternative mating tactics and male-male competition in teleost fishes.

Journal ArticleDOI
TL;DR: This work finds that ink from longfin inshore squid affected the approach phase of predation by summer flounder, primarily through its visual effects, and provides the basis for a comparative approach to identify deterrent molecules from inking cephalopods and to examine neural mechanisms whereby these chemicals affect behavior of fish, using the sea catfish as a chemosensory model.
Abstract: Chemical and visual defenses are used by many organisms to avoid being approached or eaten by predators. An example is inking molluscs—including gastropods such as sea hares and cephalopods such as squid, cuttlefish, and octopus—which release a colored ink upon approach or attack. Previous work showed that ink can protect molluscs through a combination of chemical, visual, and other ef- fects. In this study, we examined the effects of ink from longfin inshore squid, Doryteuthis pealeii, on the behavior of two species of predatory fishes, summer flounder, Paralichthys dentatus, and sea catfish, Ariopsis felis. Using a cloud assay, we found that ink from longfin inshore squid affected the approach phase of predation by summer floun- der, primarily through its visual effects. Using a food assay, we found that the ink affected the consummatory and in- gestive phase of predation of both sea catfish and summer flounder, through the ink's chemical properties. Fraction- ation of ink showed that most of its deterrent chemical activity is associated with melanin granules, suggesting that either compounds adhering to these granules or melanin itself are the most biologically active. This work provides the basis for a comparative approach to identify deterrent molecules from inking cephalopods and to examine neural mechanisms whereby these chemicals affect behavior of fish, using the sea catfish as a chemosensory model.

Journal ArticleDOI
TL;DR: These experiments support field observations that, in some marine habitats, cuttlefish will respond to vertically oriented background features even when the preponderance of visual information in their field of view seems to be from the 2D surrounding substrate.
Abstract: Cuttlefish and other cephalopods use visual cues from their surroundings to adaptively change their body pattern for camouflage. Numerous previous experiments have demonstrated the influence of two-dimensional (2D) substrates (e.g., sand and gravel habitats) on camouflage, yet many marine habitats have varied three-dimensional (3D) structures among which cuttlefish camouflage from predators, including benthic predators that view cuttlefish horizontally against such 3D backgrounds. We conducted laboratory experiments, using Sepia officinalis, to test the relative influence of horizontal versus vertical visual cues on cuttlefish camouflage: 2D patterns on benthic substrates were tested versus 2D wall patterns and 3D objects with patterns. Specifically, we investigated the influence of (i) quantity and (ii) placement of high-contrast elements on a 3D object or a 2D wall, as well as (iii) the diameter and (iv) number of 3D objects with high-contrast elements on cuttlefish body pattern expression. Additionally...

Journal ArticleDOI
TL;DR: Parts of oocyte maturation and fertilization in marine nemertean worms are reviewed and briefly compared with related findings that have been published for mammalian oocytes, and possible causes of the alternative responses displayed by oocytes in these two animal groups are addressed.
Abstract: In marine worms belonging to the phylum Nemertea, oocyte maturation and fertilization are regulated by the same general kinds of signals that control such processes in mammals. However, unlike mammalian oocytes that develop within follicles, nemertean oocytes characteristically lack a surrounding sheath of follicle cells and often respond differently to maturation-related cues than do mammalian oocytes. For example, elevators of cyclic adenosine monophosphate (cAMP) or cyclic guanos- ine monophosphate (cGMP) levels promote the resumption of meiotic maturation (germinal vesicle breakdown, GVBD) in nemertean oocytes, whereas increasing in- traoocytic cAMP and cGMP typically blocks GVBD in mammals. Similarly, AMP-activated kinase (AMPK) sig- naling keeps nemertean oocytes from maturing, but in mouse oocytes, AMPK activation triggers GVBD. In addi- tion, protein kinase C (PKC) activity is required for sea- water-induced GVBD in nemerteans, whereas some PKCs have been shown to inhibit GVBD in mammals. Further- more, although fertilization causes both types of oocytes to reorganize their endoplasmic reticulum and generate cal- cium oscillations that can involve soluble sperm factor activity and inositol 1,4,5-trisphosphate signaling, some dis- crepancies in the spatiotemporal patterns and underlying mechanisms of fertilization are also evident in nemerteans versus mammals. Thus, to characterize differences and sim- ilarities in gamete biology more fully, aspects of oocyte maturation and fertilization in marine nemertean worms are reviewed and briefly compared with related findings that have been published for mammalian oocytes. In addition, possible causes of the alternative responses displayed by oocytes in these two animal groups are addressed.

Journal ArticleDOI
TL;DR: The results indicate that the microtransplantation of native cell membranes is useful to identify and characterize scarce membrane proteins, and support the role of GABA as an ionotropic neurotransmitter in cephalopods, acting through chloride-permeable membrane receptors.
Abstract: The squid has been the most studied cephalopod, and it has served as a very useful model for investigating the events associated with nerve impulse generation and synaptic transmission. While the physiology of squid giant axons has been extensively studied, very little is known about the distribution and function of the neurotransmitters and receptors that mediate inhibitory transmission at the synapses. In this study we investigated whether γ-aminobutyric acid (GABA) activates neurotransmitter receptors in stellate ganglia membranes. To overcome the low abundance of GABA-like mRNAs in invertebrates and the low expression of GABA in cephalopods, we used a two-electrode voltage clamp technique to determine if Xenopus laevis oocytes injected with cell membranes from squid stellate ganglia responded to GABA. Using this method, membrane patches containing proteins and ion channels from the squid’s stellate ganglion were incorporated into the surface of oocytes. We demonstrated that GABA activates membrane rec...

Journal ArticleDOI
TL;DR: Results show that cuttlefish mainly use an ambush strategy and that squid use a pursuit strategy, with possible causes for the ontogenetic differences in hunting behavior discussed.
Abstract: Animals adopt various forms of hunting according to their ecological, morphological, and cognitive features, and their specific hunting skills are acquired ontogenetically in relation to these features. It is noted that cuttlefish and squid hunt prey through the elongation of tentacles used specifically to capture prey. However, these two cephalopods have different lifestyles, leading to questions such as whether hunting skill is acquired similarly after birth and whether tentacle elongation is behaviorally identical. To address these questions, we observed and compared how captive pharaoh cuttlefish (Sepia pharaonis) and oval squid (Sepioteuthis lessoniana) attack prey during their early life stages. Like the adults, S. pharaonis hatchlings used the tentacular lunge attack, whereas S. lessoniana hatchlings used the arm-opening attack. S. lessoniana began to exhibit the tentacular strike attack after 30 days of age. In addition to timing of the emergence of a specific hunting mode, some differences were observed in the physical aspect of hunting behavior. For cuttlefish, maximum tentacle length and maximum speed of tentacle elongation increased from hatching to 30 days of age and then decreased. In contrast, for squid, maximum tentacle length increased from hatching to 30 days of age and then became constant. The distance to prey was positively correlated with maximum length and speed of tentacle elongation in S. pharaonis and with maximum swimming speed in S. lessoniana. These results show that cuttlefish mainly use an ambush strategy and that squid use a pursuit strategy. Possible causes for the ontogenetic differences in hunting behavior are discussed.

Journal ArticleDOI
TL;DR: It is found that the pulmonate Cornu aspersum moved using adhesive crawling on dry acrylic or glass substrates, but loped on dry concrete or wood, suggesting that this plasticity in gait is widespread among terrestrial snails.
Abstract: Some terrestrial gastropods are able to move using two gaits: adhesive crawling, where the entire foot is separated from the substrate only by a thin layer of mucus and the snail leaves a continuous mucus trail; and loping, where regions of the foot arch above the substrate and the snail leaves a discontinuous mucus trail. Loping has been interpreted as a means of rapidly escaping predators. We found that the pulmonate Cornu aspersum moved using adhesive crawling on dry acrylic or glass substrates, but loped on dry concrete or wood. Loping snails did not move more rapidly than snails using adhesive crawling. Snails moving on concrete secreted a greater volume of pedal mucus per area of trail than those moving on acrylic; locomotion on concrete thus requires greater expenditure of mucus than does locomotion on acrylic. Because loping snails deposit a smaller area of mucus per distance traveled than do snails using adhesive crawling, loping may conserve mucus when moving on porous, absorbent substrates. Members of several other terrestrial pulmonate taxa can also lope on concrete, suggesting that this plasticity in gait is widespread among terrestrial snails.

Journal ArticleDOI
TL;DR: This position paper focuses on structural modifications in N-methyl-d-aspartate receptors (NMDARs) that occur during postnatal forebrain development and attempts to provide a method for pursuing a more complete understanding of the functional ramifications of developmental alterations in NMDAR subunit composition.
Abstract: The numbers and types of ionotropic glutamate receptors at most vertebrate central excitatory synapses are altered as a function of changes in input activity patterns that occur during postnatal development. Activity-dependent developmental alterations in glutamate receptors underlie lasting changes in synaptic efficacy (plasticity) and metaplasticity (the plasticity of synaptic plasticity), which are critical elements of normal brain maturation. Understanding the specific involvement of glutamate receptors in synaptic development and function is made multiplicatively complex by the existence of a large number of glutamate receptor subunits, numerous subunit-specific amino acid sequences that regulate receptor function, and subunit-specific synaptic insertion restrictions imposed by associated anchoring proteins. Many receptor properties are altered when subunits are switched, so it is unclear which individual receptor property or properties underlie changes in synaptic function and plasticity during post...

Journal ArticleDOI
TL;DR: It is proposed that membrane lipids displaying negative curvature act in concert with membrane proteins to contribute to the alteration and maintenance of bending in biological membranes.
Abstract: The importance of proteins in shaping the membranes that define the perimeters of organelles is well documented. By forming cross-links, motors, or scaffolds or by inserting into membranes, proteins can harness energy to deform membranes, particularly when high degrees of curvature are necessitated—as in small membrane vesicles, tubules of the endoplasmic reticulum, the edges of endo- plasmic reticulum sheets or Golgi apparatus cisternae, and membrane fusion intermediates (stalks). Here we propose that membrane lipids displaying negative curvature act in concert with membrane proteins to contribute to the altera- tion and maintenance of bending in biological membranes. We emphasize recent data from studies of sea urchin eggs and embryos and suggest how novel approaches can lead to future directions for investigating the roles of such lipids in vivo.

Journal ArticleDOI
TL;DR: The establishment of sea urchin cortical vesicle fusion is discussed as a model to study regulated exocytosis—a system in which the docked, release-ready, and late Ca2+-triggered steps of exocyTosis are isolated and can be quantitatively assessed using the rigorous coupling of functional and molecular assays.
Abstract: Regulated exocytosis is one of the defining features of eukaryotic cells, underlying many conserved and essential functions. Definitively assigning specific roles to proteins and lipids in this fundamental mechanism is most effectively accomplished using a model system in which distinct stages of exocytosis can be effectively separated. Here we discuss the establishment of sea urchin cortical vesicle fusion as a model to study regulated exocytosis—a system in which the docked, release-ready, and late Ca2+-triggered steps of exocytosis are isolated and can be quantitatively assessed using the rigorous coupling of functional and molecular assays. We provide an overview of the insights this has provided into conserved molecular mechanisms and how these have led to and integrate with findings from other regulated exocytotic cells.

Journal ArticleDOI
TL;DR: Investigation of the reproductive cycle and growth of the temperate New Zealand rhynchonelliform brachiopod Liothyrella neozelanica indicated a seasonal cycle with prolonged, potentially asynchronous spawning and a decrease in the proportion of the gonad area occupied by sperm during September suggests a level of spawning synchrony between sexes.
Abstract: The reproductive cycle and growth of the temperate New Zealand rhynchonelliform brachiopod Liothyrella neozelanica was examined over 12 months (December 2010 and December 2011). The research aimed to clarify the spawning cycle, life history, population size, and age structure of L. neozelanica and to enable more direct comparisons with the Antarctic brachiopod Liothyrella uva. Reproduction over the course of a year was quantified by monthly examination of gonad size and gametogenesis. Histological examination indicated a seasonal cycle with prolonged, potentially asynchronous spawning. Increased numbers of large oocytes in July followed by a significant decrease in September suggest that female spawning takes place in early austral spring. A decrease in the proportion of the gonad area occupied by sperm during September suggests a level of spawning synchrony between sexes. Somatic growth was modeled from 60 tagged individuals. A maximum size of ≈ 50-mm shell length is achieved at 17 years of age, and inst...

Journal ArticleDOI
TL;DR: Coleodesmium karaensis is the first enteropneust (and indeed the first hemichordate) found brooding embryos on the surface of the mother’s body, and clearly distinguishes it from the much more muscular members of Allapasus.
Abstract: A single specimen of a previously undescribed acorn worm in the family Torquaratoridae was trawled from a bottom depth of about 350 m in the Kara Sea (Russian Arctic). The new species is the shallowest of the exclusively deep-sea torquaratorids found to date, possibly an example of high-latitude emergence. On the basis of ribosomal DNA sequences and morphology, the worm is described here as the holotype of Coleodesmium karaensis n. gen., n. sp. It is most similar in overall body shape to the previously described enteropneust genus Allapasus, but is uniquely characterized by a tubular component of the proboscis skeleton ensheathing the collar nerve cord. Additionally, within the proboscis, the sparseness of the musculature of C. karaensis clearly distinguishes it from the much more muscular members of Allapasus. The holotype is a female bearing about a dozen embryos on the surface of her pharyngeal region, each recessed within a shallow depression in the dorsal epidermis. The embryos, ranging from late gas...

Journal ArticleDOI
TL;DR: The effects of letrozole (LZ), a potent nonsteroidal aromatase inhibitor (AI), on growth performance, sex inversion, and sex changes were investigated in yellow catfish, which display sexual dimorphic growth.
Abstract: The effects of letrozole (LZ), a potent nonsteroidal aromatase inhibitor (AI), on growth performance, sex inversion, and sex changes were investigated in yellow catfish (Pelteobagrus fulvidraco), which display sexual dimorphic growth. Growth performance was promoted significantly in the low-dose LZ treatment, compared with the control. Four LZ treatments produced dose-dependent male proportions that were significantly higher than that of the control. Histological examination of testes treated by LZ displayed a large amount of spermatozoa and enlarged lobule lumens, indicating that LZ treatments can potentially stimulate spermatogenesis. Changes of sex proportions 45 days after the end of the LZ treatments prove that the female germ cells possess a certain degree of bipotentiality. These results suggest that aromatase activity plays a vital role in sex differentiation, as in other teleosts, with inhibition of aromatase activity by AI bringing about sex inversion.

Journal ArticleDOI
TL;DR: How the study of SNBPs in the tunicates has been key to providing support to the H1 → PL → P transition is discussed, as a potential molecular mechanism to explain the lysine-to-arginine transition was first reported.
Abstract: Sperm nuclear basic proteins (SNBPs) are the chromosomal proteins that are found associated with DNA in sperm nuclei at the end of spermiogenesis. These highly specialized proteins can be classified into three major types: histone type (H-type), protamine-like type (PL-type), and protamine type (P-type). A hypothesis from early studies on the characterization of SNBPs proposed a mechanism for the vertical evolution of these proteins that involved an H1 3 PL 3 P transition. However, the processes and mechanisms involved in such a transition were not under- stood. In particular, it was not clear how a molecular tran- sition from a lysine-rich protein precursor (H1 histone) to the arginine-rich protamines might have taken place. In deuterostomes, the presence of SNBPs of the H-type in echinoderms and of protamines in the higher phylogenetic groups of vertebrates had long been known. The initial work on the characterization of tunicate SNBPs attempted to define the types and range of SNBPs that characterize this phylogenetically intermediate group. It was found that tu- nicate SNBPs belong to the PL-type. In this work we discuss how the study of SNBPs in the tunicates has been key to providing support to the H1 3 PL 3 P transition. Most significantly, it was in tunicates that a potential mo- lecular mechanism to explain the lysine-to-arginine transi- tion was first reported.

Journal ArticleDOI
TL;DR: It is hypothesize that the ability to discriminate anode from cathode is physiologically encoded, but its utility in providing spatial information under natural conditions remains to be demonstrated.
Abstract: It is well established that elasmobranchs can detect dipole electric fields. However, it is unclear whether they can discriminate between the anode and cathode. To investigate this subject, we employed a behavioral assay to determine the discriminatory ability of the yellow stingray, Urobatis jamaicensis. We conditioned stingrays with food rewards to bite either the anode (n=5) or the cathode (n=6) of a direct-current dipole located on the floor of an experimental tank. All individuals successfully performed the task after 18 to 22 days. Stingrays were then tested in experimental sessions when they were rewarded only after they identified the correct pole. Stingrays successfully discriminated between the poles at a rate greater than chance, ranging among individuals from a mean of 66% to 93% correct. During experimental sessions, stingrays conditioned to distinguish the anode performed similarly to those conditioned to distinguish the cathode. We hypothesize that the ability to discriminate anode from cathode is physiologically encoded, but its utility in providing spatial information under natural conditions remains to be demonstrated. The ability to discriminate polarity may eliminate ambiguity in induction-based magnetoreception and facilitate navigation with respect to the geomagnetic field.

Journal ArticleDOI
TL;DR: It is indicated that, like adults, juvenile horseshoe crabs express both daily and tidal patterns of activity and that at least one, and maybe both, of these patterns is driven by endogenous clocks.
Abstract: Adult American horseshoe crabs, Limulus polyphemus, possess endogenous circadian and circatidal clocks controlling visual sensitivity and locomotion, respectively. The goal of this study was to determine the types of activity rhythms expressed by juvenile horseshoe crabs (n = 24) when exposed to a 14:10 light/dark cycle (LD) for 10 days, followed by 10 days of constant darkness (DD). Horseshoe crab activity was recorded with a digital time-lapse video system that used an infrared-sensitive camera so animals could be monitored at night. In LD, 15 animals expressed daily patterns of activity, 6 displayed a circatidal pattern, and the remaining 3 were arrhythmic. Of the 15 animals with daily patterns of locomotion, 7 had a significant preference (P < 0.05) for diurnal activity and 3 for nocturnal activity; the remainder did not express a significant preference for day or night activity. In DD, 13 horseshoe crabs expressed circatidal rhythms and 8 maintained a pattern of about 24 h. Although these results suggest the presence of a circadian clock influencing circatidal patterns of locomotion, these apparent circadian rhythms may actually represent the expression of just one of the two bouts of activity driven by the putative circalunidian clocks that control their tidal rhythms. Overall, these results indicate that, like adults, juvenile horseshoe crabs express both daily and tidal patterns of activity and that at least one, and maybe both, of these patterns is driven by endogenous clocks.