Marine Resources Center (MRC)
Permanent URI for this community
The Marine Resources Center (MRC) is a highly advanced facility for maintaining, culturing, and providing aquatic organisms essential to advanced biological, biomedical, and ecological research. Research is partitioned into two programs: The Program in Sensory Biology and Neuroethology; and The Program in Scientific Aquaculture.
Browse
Browsing Marine Resources Center (MRC) by Title
Results Per Page
Sort Options
-
ArticleA small change with a twist ending: a single residue in EGF-CFC drives bilaterian asymmetry(Oxford University Press, 2022-12-22) Truchado-García, Marta ; Perry, Kimberly J. ; Cavodeassi, Florencia ; Kenny, Nathan J. ; Henry, Jonathan Q. ; Grande, CristinaAsymmetries are essential for proper organization and function of organ systems. Genetic studies in bilaterians have shown signaling through the Nodal/Smad2 pathway plays a key, conserved role in the establishment of body asymmetries. Although the main molecular players in the network for the establishment of left-right asymmetry (LRA) have been deeply described in deuterostomes, little is known about the regulation of Nodal signaling in spiralians. Here, we identified orthologs of the egf-cfc gene, a master regulator of the Nodal pathway in vertebrates, in several invertebrate species, which includes the first evidence of its presence in non-deuterostomes. Our functional experiments indicate that despite being present, egf-cfc does not play a role in the establishment of LRA in gastropods. However, experiments in zebrafish suggest that a single amino acid mutation in the egf-cfc gene in at least the common ancestor of chordates was the necessary step to induce a gain of function in LRA regulation. This study shows that the egf-cfc gene likely appeared in the ancestors of deuterostomes and "protostomes", before being adopted as a mechanism to regulate the Nodal pathway and the establishment of LRA in some lineages of deuterostomes.
-
ArticleA Wox3-patterning module organizes planar growth in grass leaves and ligules(Nature Research, 2023-05-04) Satterlee, James W. ; Evans, Lukas J. ; Conlon, Brianne R. ; Conklin, Phillip ; Martinez-Gomez, Jesus ; Yen, Jeffery R. ; Wu, Hao ; Sylvester, Anne W. ; Specht, Chelsea D. ; Cheng, Jie ; Johnston, Robyn ; Coen, Enrico ; Scanlon, Michael J.Grass leaves develop from a ring of primordial initial cells within the periphery of the shoot apical meristem, a pool of organogenic stem cells that generates all of the organs of the plant shoot. At maturity, the grass leaf is a flattened, strap-like organ comprising a proximal supportive sheath surrounding the stem and a distal photosynthetic blade. The sheath and blade are partitioned by a hinge-like auricle and the ligule, a fringe of epidermally derived tissue that grows from the adaxial (top) leaf surface. Together, the ligule and auricle comprise morphological novelties that are specific to grass leaves. Understanding how the planar outgrowth of grass leaves and their adjoining ligules is genetically controlled can yield insight into their evolutionary origins. Here we use single-cell RNA-sequencing analyses to identify a ‘rim’ cell type present at the margins of maize leaf primordia. Cells in the leaf rim have a distinctive identity and share transcriptional signatures with proliferating ligule cells, suggesting that a shared developmental genetic programme patterns both leaves and ligules. Moreover, we show that rim function is regulated by genetically redundant Wuschel-like homeobox3 (WOX3) transcription factors. Higher-order mutations in maize Wox3 genes greatly reduce leaf width and disrupt ligule outgrowth and patterning. Together, these findings illustrate the generalizable use of a rim domain during planar growth of maize leaves and ligules, and suggest a parsimonious model for the homology of the grass ligule as a distal extension of the leaf sheath margin.
-
ArticleAcoustic detection and quantification of benthic egg beds of the squid Loligo opalescens in Monterey Bay, California(Acoustical Society of America, 2006-02) Foote, Kenneth G. ; Hanlon, Roger T. ; Iampietro, Pat J. ; Kvitek, Rikk G.The squid Loligo opalescens is a key species in the nearshore pelagic community of California, supporting the most valuable state marine fishery, yet the stock biomass is unknown. In southern Monterey Bay, extensive beds occur on a flat, sandy bottom, water depths 20–60 m, thus sidescan sonar is a prima-facie candidate for use in rapid, synoptic, and noninvasive surveying. The present study describes development of an acoustic method to detect, identify, and quantify squid egg beds by means of high-frequency sidescan-sonar imagery. Verification of the method has been undertaken with a video camera carried on a remotely operated vehicle. It has been established that sidescan sonar images can be used to predict the presence or absence of squid egg beds. The lower size limit of detectability of an isolated egg bed is about 0.5 m with a 400-kHz sidescan sonar used with a 50-m range when towed at 3 knots. It is possible to estimate the abundance of eggs in a region of interest by computing the cumulative area covered by the egg beds according to the sidescan sonar image. In a selected quadrat one arc second on each side, the estimated number of eggs was 36.5 million.
-
ArticleAdaptable night camouflage by cuttlefish(University of Chicago Press, 2007-02-12) Hanlon, Roger T. ; Naud, Marie-Jose ; Forsythe, John W. ; Hall, Karina ; Watson, Anya C. ; McKechnie, JoyCephalopods are well known for their diverse, quick‐changing camouflage in a wide range of shallow habitats worldwide. However, there is no documentation that cephalopods use their diverse camouflage repertoire at night. We used a remotely operated vehicle equipped with a video camera and a red light to conduct 16 transects on the communal spawning grounds of the giant Australian cuttlefish Sepia apama situated on a temperate rock reef in southern Australia. Cuttlefish ceased sexual signaling and reproductive behavior at dusk and then settled to the bottom and quickly adapted their body patterns to produce camouflage that was tailored to different backgrounds. During the day, only 3% of cuttlefish were camouflaged on the spawning ground, but at night 86% (71 of 83 cuttlefish) were camouflaged in variations of three body pattern types: uniform (n=5), mottled (n=33), or disruptive (n=34) coloration. The implication is that nocturnal visual predators provide the selective pressure for rapid, changeable camouflage patterning tuned to different visual backgrounds at night.
-
PreprintThe behaviour and ecology of the zebrafish, Danio rerio( 2007-03-07) Spence, Rowena ; Gerlach, Gabriele ; Lawrence, Christian ; Smith, CarlThe zebrafish is an important model organism in developmental genetics, neurophysiology and biomedicine, but little is known about its natural ecology and behaviour. It is a small, shoaling cyprinid, native to the flood-plains of the Indian subcontinent, where it is found in shallow, slow-flowing waters. Zebrafish are group spawners and egg scatterers, although females are choosy with respect to sites for oviposition and males defend territories around such sites. Laboratory studies of zebrafish behaviour have encompassed shoaling, foraging, reproduction, sensory perception and learning. These studies are reviewed in relation to the suitability of the zebrafish as a model for studies on cognition and learning, development, behavioural and evolutionary ecology, and behavioural genetics.
-
PreprintBiological versus electronic adaptive coloration : how can one inform the other?( 2011-11) Kreit, Eric ; Mathger, Lydia M. ; Hanlon, Roger T. ; Dennis, Patrick B. ; Naik, Rajesh R. ; Forsythe, Eric ; Heikenfeld, JasonAdaptive reflective surfaces have been a challenge for both electronic paper (e-Paper) and biological organisms. Multiple colours, contrast, polarization, reflectance, diffusivity and texture must all be controlled simultaneously without optical losses in order to fully replicate the appearance of natural surfaces and vividly communicate information. This review merges the frontiers of knowledge for both biological adaptive coloration, with a focus on cephalopods, and synthetic reflective e-Paper within a consistent framework of scientific metrics. Currently, the highest performance approach for both nature and technology utilizes colourant transposition. Three outcomes are envisioned from this review: reflective display engineers may gain new insights from millions of years of natural selection and evolution; biologists will benefit from understanding the types of mechanisms, characterization, and metrics used in synthetic reflective e-Paper; all scientists will gain a clearer picture of the long-term prospects for capabilities such as adaptive concealment and signalling.
-
ArticleBryostatin enhancement of memory in Hermissenda(Marine Biological Laboratory, 2006-06) Kuzirian, Alan M. ; Epstein, H. T. ; Gagliardi, C. J. ; Nelson, T. J. ; Sakakibara, M. ; Taylor, C. ; Scioletti, A. B. ; Alkon, D. L.Bryostatin, a potent agonist of protein kinase C (PKC), when administered to Hermissenda was found to affect acquisition of an associative learning paradigm. Low bryostatin concentrations (0.1 to 0.5 ng/ml) enhanced memory acquisition, while concentrations higher than 1.0 ng/ml down-regulated the pathway and no recall of the associative training was exhibited. The extent of enhancement depended upon the conditioning regime used and the memory stage normally fostered by that regime. The effects of two training events (TEs) with paired conditioned and unconditioned stimuli, which standardly evoked only short-term memory (STM) lasting 7 min, were—when bryostatin was added concurrently—enhanced to a long-term memory (LTM) that lasted about 20 h. The effects of both 4- and 6-paired TEs (which by themselves did not generate LTM), were also enhanced by bryostatin to induce a consolidated memory (CM) that lasted at least 5 days. The standard positive 9-TE regime typically produced a CM lasting at least 6 days. Low concentrations of bryostatin (<0.5 ng/ml) elicited no demonstrable enhancement of CM from 9-TEs. However, animals exposed to bryostatin concentrations higher than 1.0 ng/ml exhibited no behavioral learning. Sharp-electrode intracellular recordings of type-B photoreceptors in the eyes from animals conditioned in vivo with bryostatin revealed changes in input resistance and an enhanced long-lasting depolarization (LLD) in response to light. Likewise, quantitative immunocytochemical measurements using an antibody specific for the PKC-activated Ca2+/GTP-binding protein calexcitin showed enhanced antibody labeling with bryostatin. Animals exposed to the PKC inhibitor bisindolylmaleimide-XI (Ro-32-0432) administered by immersion prior to 9-TE conditioning showed no training-induced changes with or without bryostatin exposure. However, if animals received bryostatin before Ro-32, the enhanced acquisition and demonstrated recall still occurred. Therefore, pathways responsible for the enhancement effects induced by bryostatin were putatively mediated by PKC. Overall, the data indicated that PKC activation occurred and calexcitin levels were raised during the acquisition phases of associative conditioning and memory initiation, and subsequently returned to baseline levels within 24 and 48 h, respectively. Therefore, the protracted recall measured by the testing regime used was probably due to bryostatin-induced changes during the acquisition and facilitated storage of memory, and not necessarily to enhanced recall of the stored memory when tested many days after training.
-
ArticleCephalopod genomics : a plan of strategies and organization(Genomic Standards Consortium, 2012-09-26) Albertin, Caroline B. ; Bonnaud, Laure ; Brown, C. Titus ; Crookes-Goodson, Wendy J. ; da Fonseca, Rute R. ; Di Cristo, Carlo ; Dilkes, Brian P. ; Edsinger-Gonzales, Eric ; Freeman, Robert J. ; Hanlon, Roger T. ; Koenig, Kristen M. ; Lindgren, Annie R. ; Martindale, Mark Q. ; Minx, Patrick ; Moroz, Leonid L. ; Nodl, Marie-Therese ; Nyholm, Spencer V. ; Ogura, Atsushi ; Pungor, Judit R. ; Rosenthal, Joshua J. C. ; Schwarz, Erich M. ; Shigeno, Shuichi ; Strugnell, Jan M. ; Wollesen, Tim ; Zhang, Guojie ; Ragsdale, Clifton W.The Cephalopod Sequencing Consortium (CephSeq Consortium) was established at a NESCent Catalysis Group Meeting, “Paths to Cephalopod Genomics- Strategies, Choices, Organization,” held in Durham, North Carolina, USA on May 24-27, 2012. Twenty-eight participants representing nine countries (Austria, Australia, China, Denmark, France, Italy, Japan, Spain and the USA) met to address the pressing need for genome sequencing of cephalopod molluscs. This group, drawn from cephalopod biologists, neuroscientists, developmental and evolutionary biologists, materials scientists, bioinformaticians and researchers active in sequencing, assembling and annotating genomes, agreed on a set of cephalopod species of particular importance for initial sequencing and developed strategies and an organization (CephSeq Consortium) to promote this sequencing. The conclusions and recommendations of this meeting are described in this White Paper.
-
PreprintChanges in reflectin protein phosphorylation are associated with dynamic iridescence in squid( 2009-07-18) Izumi, Michi ; Sweeney, Alison M. ; DeMartini, Daniel ; Weaver, James C. ; Powers, Meghan L. ; Tao, Andrea ; Silvas, Tania V. ; Kramer, Ryan M. ; Crookes-Goodson, Wendy J. ; Mathger, Lydia M. ; Naik, Rajesh R. ; Hanlon, Roger T. ; Morse, Daniel E.Many cephalopods exhibit remarkable dermal iridescence, a component of their complex, dynamic camouflage and communication. In the species Euprymna scolopes, the light-organ iridescence is static and is due to reflectin protein-based platelets assembled into lamellar thin-film reflectors called iridosomes, contained within iridescent cells called iridocytes. Squid in the family Loliginidae appear to be unique in that the dermis possesses a dynamic iridescent component, with reflective, colored structures that are assembled and disassembled under the control of the muscarinic cholinergic system and the associated neurotransmitter acetylcholine (Mathger et al. 2004). Here we present the sequences and characterization of three new members of the reflectin family associated with the dynamically changeable iridescence in Loligo and not found in static Euprymna iridophores. In addition, we show that application of genistein, a protein tyrosine kinase inhibitor, suppresses acetylcholine- and calcium-induced iridescence in Loligo. We further demonstrate that two of these novel reflectins are extensively phosphorylated in concert with the activation of iridescence by exogenous acetylcholine. This phosphorylation and the correlated iridescence can be blocked with genistein. Our results suggest that tyrosine phosphorylation of reflectin proteins is involved in the regulation of dynamic iridescence in Loligo.
-
PreprintCharacterization of EST derived SSRs from the bay scallop, Argopecten irradians( 2005-03-03) Roberts, Steven B. ; Romano, Christina ; Gerlach, GabrieleInterest in bay scallop conservation has resulted in organized stock enhancement efforts and increased attention to fisheries management issues. Genetic markers can facilitate the monitoring of enhancement efforts, characterization of wild populations, and optimize hatchery practices. We have identified eight polymorphic simple sequence repeat markers including one dinucleotide, six trinucleotide and one compound dinucleotide repeats, in expressed sequence tags generated from multiple bay scallop cDNA libraries. The numbers of alleles range from two to five. The expected and observed heterozygosities range from 0.093 to 0.720 and 0.095 to 0.600, respectively.
-
ArticleClicking for calamari : toothed whales can echolocate squid Loligo pealeii(Inter-Research, 2007-11-27) Madsen, Peter T. ; Wilson, M. ; Johnson, Mark P. ; Hanlon, Roger T. ; Bocconcelli, Alessandro ; Aguilar De Soto, Natacha ; Tyack, Peter L.Squid play an important role in biomass turnover in marine ecosystems and constitute a food source for ~90% of all echolocating toothed whale species. Nonetheless, it has been hypothesized that the soft bodies of squid provide echoes too weak to be detected by toothed whale biosonars, and that only the few hard parts of the squid body may generate significant backscatter. We measured the acoustic backscatter from the common squid Loligo pealeii for signals similar to toothed whale echolocation clicks using an energy detector to mimic the mammalian auditory system. We show that the dorsal target strengths of L. pealeii with mantle lengths between 23 and 26 cm fall in the range from –38 to –44 dB, and that the pen, beak and lenses do not contribute significantly to the backscatter. Thus, the muscular mantle and fins of L. pealeii constitute a sufficient sonar target for individual biosonar detection by toothed whales at ranges between 25 and 325 m, depending on squid size, noise levels, click source levels, and orientation of the ensonified squid. While epipelagic squid must be fast and muscular to catch prey and avoid visual predators, it is hypothesized that some deep-water squid may have adopted passive acoustic crypsis, with a body of low muscle mass and low metabolism that will render them less conspicuous to echolocating predators.
-
Working PaperCreation of the Marine Resource Center at MBL( 2007-09) Halvorson, Harlyn O.The creation of the Station Biologique de Roscoff In France in 1859 heralded a century of study of marine animals. In the US, Congress created the U.S. Commission of Fish and Fisheries in 1871 to investigate declining fish stocks. With the formation of the Marine Biological Laboratory (MBL) in 1888, a wooden Supply Department building was constructed in 1924 to supply animals for research and educational programs. By 1939 this building was thought to be inadequate. Beginning in the 1970's efforts started to address the need for a new facility for marine animals under the directorship of Jim Ebert, Keith Porter and Paul Gross. Unfortunately efforts to fund the facility were unsuccessful. This article reviews the need for a new facility, the strategy developed by the MBL Board of Trustees, including the establishment of the laboratory for marine animal Health, the establishment of the National Association of Marine laboratories (NAML), and a National Academy of Science report that NIH encourage interest in non-mammalian systems for biomedical research. In 1988 MBL received the first phases of funding for a Marine Resource Center (MRC) on the Eel Pond as part of a Marine Biomedical Institute for Advanced Studies (MBIAS). Construction of the MRC began in January 1991 and the building was occupied in August 1992.
-
ArticleCulture-dependent characterization of the microbial community associated with epizootic shell disease lesions in American lobster, Homarus americanus(National Shellfisheries Association, 2005-10-01) Chistoserdov, Andrei Y. ; Smolowitz, Roxanna M. ; Mirasol, Feliza ; Hsu, AndreaEpizootic shell disease in the American lobster is an important factor affecting lobster fisheries in and around the Long Island Sound. It is a strictly dermal disease, because no correlation was observed between occurrence of epizootic shell disease and hemolymph infection. The culturability of bacteria from lesions was variable and averaged around 1.1%. The lesions contained two to four orders of magnitude more bacteria than healthy carapace surfaces of the same animal. Chitinoclastic bacteria comprised a very small fraction of bacteria present in the lesions, suggesting that their role in epizootic shell disease may be limited. Phylogenetic analysis of bacteria isolated from the lesions showed no typical bacterial pathogens of lobsters such as Aerococcus viridans or Vibrio fluvialis. Moreover, bacteria commonly associated with shell disease of other Crustacea or other forms of shell disease of the American lobster were not found. Two common groups of bacteria were isolated from lesions of all lobsters used in this research: one belonging to a species complex affiliated with the Flavobacteriaceae family and the second belonging to a series of closely related if not identical strains of Pseudoalteromonas gracilis. Bacteria isolated from only a few lobsters were related to Shewanella frigidimarina, Alteromonas arctica, Vibrio lentus, Shewanella fidelia, Pseudoalteromonas tunicata and Vibrio spp. Based on the analyses of culturable isolates, overall microbial communities found in lesions of lobsters from eastern Long Island Sound and Buzzards Bay appear to be similar to each other.
-
ArticleDevelopment and validation of a real-time quantitative PCR assay for the detection and quantification of Perkinsus marinus in the Eastern oyster, Crassostrea virginica(National Shellfisheries Association, 2009-08) DeFaveri, Jacquelin ; Smolowitz, Roxanna M. ; Roberts, Steven B.Perkinus marinus causes a devastating disease, known as Dermo, in the Eastern oyster Crassostrea virginica. Routine detection of the disease is traditionally accomplished by the use of the Ray/Makin assay, using Fluid Thioglycollate Medium (RFTM). A simple real-time quantitative PCR assay was developed as a diagnostic tool to detect and quantify P. marinus, to complement and serve as an alternate to the RFTM method. Using a dual-labeled probe approach, a sensitive assay was designed to accurately detect a range of one to several thousand P. marinus organisms present in oyster tissues. A simple extraction method was used to increase throughput of the assay. Cultured P. marinus cells were quantified prior to DNA extraction, generating a standard curve and allowing cell counts to be derived from PCR cycle threshold values. Direct comparison of the RFTM and real-time PCR methods was accomplished by using tissue samples from the same oyster for both tests. Plotting cycle threshold values against the known Mackin index value generated a standard curve with a coefficient of regression of 0.9. Our results indicate that correlations could be made between this molecular based approach and traditional methods, allowing results generated from the PCR assay to be easily translated into the understood Mackin scale.
-
ArticleDevelopment of a real time quantitative PCR assay for the hard clam pathogen Quahog Parasite Unknown (QPX)(Inter-Research, 2006-09-14) Lyons, M. Maille ; Smolowitz, Roxanna M. ; Dungan, Christopher F. ; Roberts, Steven B.Quahog Parasite Unknown (QPX) is a thraustochytrid pathogen responsible for catastrophic mortalities of the northern quahog (hard clam) Mercenaria mercenaria. A real-time quantitative polymerase chain reaction (qPCR) assay was developed to assist research efforts on QPX ecology and pathology. Sensitivity of the assay was evaluated with serial dilutions of QPX-cultured cells to determine the lowest concentration of DNA that remained detectable in both the presence and absence of extraneous environmental substances. QPX cells were quantified before DNA extraction to calibrate standard curves to cell counts. Based on our results, the qPCR assay is able to quantify QPX within the range of 1 to several thousand organisms per reaction. Specificity of the assay was assessed by testing 29 thraustochytrid-like protists isolated from suspension-feeding bivalves from China, Oregon, Maryland, and Virginia. Application of the assay was demonstrated with positive qPCR results from naturally contaminated environmental samples including marine aggregates (i.e. marine snow), clam pseudofeces, and inflammatory nodules from infected clams. This quantitative assay for QPX will provide a valuable tool for characterizing QPX parasite abundances in coastal environments and for improving clam disease diagnostics.
-
PreprintDevelopment of molecular biology at the University of Wisconsin, Madison( 2007-05) Halvorson, Harlyn O.Dramatic changes in the foundation of academic departments in our Universities are uncommon. With the demonstration that DNA was the cellular source of genetic information, and that this information could be regulated, the field of Molecular Biology was born. Later when scientists found that they could tinker with this information, the field matured. In an unusually rapid manner, Molecular Biology was integrated into the University of Wisconsin in the late 1950’s and early 1960’s. This article is a chronology of how it happened. What are the factors that made this transition possible in Madison? What lessons have we learned from this experience?
-
ArticleDGGE-based detection method for Quahog Parasite Unknown (QPX)(Inter-Research, 2006-06-12) Gast, Rebecca J. ; Cushman, E. ; Moran, Dawn M. ; Uhlinger, Kevin R. ; Leavitt, Dale F. ; Smolowitz, Roxanna M.Quahog Parasite Unknown (QPX) is a significant cause of hard clam Mercenaria mercenaria mortality along the northeast coast of the United States. It infects both wild and cultured clams, often annually in plots that are heavily farmed. Subclinically infected clams can be identified by histological examination of the mantle tissue, but there is currently no method available to monitor the presence of QPX in the environment. Here, we report on a polymerase chain reaction (PCR)-based method that will facilitate the detection of QPX in natural samples and seed clams. With our method, between 10 and 100 QPX cells can be detected in 1 l of water, 1 g of sediment and 100 mg of clam tissue. Denaturing gradient gel electrophoresis (DGGE) is used to establish whether the PCR products are the same as those in the control QPX culture. We used the method to screen 100 seed clams of 15 mm, and found that 10 to 12% of the clams were positive for the presence of the QPX organism. This method represents a reliable and sensitive procedure for screening both environmental samples and potentially contaminated small clams.
-
ArticleDisruptive body patterning of cuttlefish (Sepia officinalis) requires visual information regarding edges and contrast of objects in natural substrate backgrounds(Marine Biological Laboratory, 2005-02) Chiao, Chuan-Chin ; Kelman, Emma J. ; Hanlon, Roger T.Cuttlefish (Sepia officinalis Linnaeus, 1758) on mixed light and dark gravel show disruptive body patterns for camouflage. This response is evoked when the size of the gravel is equivalent to the area of the "White square," a component of its dorsal mantle patterns. However, the features of natural substrates that cuttlefish cue on visually are largely unknown. Therefore, we aimed to identify those visual features of background objects that are required to evoke disruptive coloration. At first, we put young cuttlefish in a circular experimental arena, presented them with natural gravel and photographs of natural gravel, and established that the animals would show a disruptive pattern when presented either with three-dimensional natural gravel or its two-dimensional photographic representation. We then manipulated the digital photographs by applying (i) a low-pass filter to remove the edges of the fragments of gravel, and (ii) a high-pass filter to remove the contrast among them. The body patterns produced by the cuttlefish in response to these altered visual stimuli were then video-recorded and graded. The results show that, to evoke disruptive coloration in cuttlefish, visual information about the edges and contrast of objects within natural substrate backgrounds is required.
-
ArticleDramatic fighting by male cuttlefish for a female mate(University of Chicago Press, 2017-05-02) Allen, Justine J. ; Akkaynak, Derya ; Schnell, Alexandra K. ; Hanlon, Roger T.Male cuttlefish compete for females with a repertoire of visually dramatic behaviors. Laboratory experiments have explored this system in Sepia officinalis, but corroborative field data have eluded collection attempts by many researchers. While scuba diving in Turkey, we fortuitously filmed an intense sequence of consort/intruder behaviors in which the consort lost and then regained his female mate from the intruder. These agonistic bouts escalated in stages, leading to fast dramatic expression of the elaborate intense zebra display and culminating in biting and inking as the intruder male attempted a forced copulation of the female. When analyzed in the context of game theory, the patterns of fighting behavior were more consistent with mutual assessment than self-assessment of fighting ability. Additional observations of these behaviors in nature are needed to conclusively determine which models best represent conflict resolution, but our field observations agree with laboratory findings and provide a valuable perspective.
-
ArticleDynamic displacement of normal and detached semicircular canal cupula(Springer, 2009-06-10) Rabbitt, Richard D. ; Breneman, Kathryn D. ; King, Curtis ; Yamauchi, Angela M. ; Boyle, Richard ; Highstein, Stephen M.The dynamic displacement of the semicircular canal cupula and modulation of afferent nerve discharge were measured simultaneously in response to physiological stimuli in vivo. The adaptation time constant(s) of normal cupulae in response to step stimuli averaged 36 s, corresponding to a mechanical lower corner frequency for sinusoidal stimuli of 0.0044 Hz. For stimuli equivalent to 40–200 deg/s of angular head velocity, the displacement gain of the central region of the cupula averaged 53 nm per deg/s. Afferents adapted more rapidly than the cupula, demonstrating the presence of a relaxation process that contributes significantly to the neural representation of angular head motions by the discharge patterns of canal afferent neurons. We also investigated changes in time constants of the cupula and afferents following detachment of the cupula at its apex—mechanical detachment that occurs in response to excessive transcupular endolymph pressure. Detached cupulae exhibited sharply reduced adaptation time constants (300 ms–3 s, n = 3) and can be explained by endolymph flowing rapidly over the apex of the cupula. Partially detached cupulae reattached and normal afferent discharge patterns were recovered 5–7 h following detachment. This regeneration process may have relevance to the recovery of semicircular canal function following head trauma.