Hydrogen sulphide demand of long-lived vestimentiferan tube worm aggregations modifies the chemical environment at deep-sea hydrocarbon seeps

Abstract Lamellibrachia luymesi is a long‐lived vestimentiferan polychaete that produces biogenic habitat at hydrocarbon seeps on the upper Louisiana slope of the Gulf of Mexico. Lamellibrachia luymesi relies on endosymbiotic, chemoautotrophic bacteria for nutrition which are supplied with hydrogen sulphide acquired from seep sediments by the tube worms. In this study, an individual‐based model is developed for L. luymesi aggregations. The results show that aggregations can persist for centuries because of extremely low mortality rates. Recruitment patterns reflect intraspecific competition for settlement space, with the recruitment period estimated between 11 and 68 years. Substantial hydrogen sulphide requirements are estimated for large aggregations of L. luymesi, exceeding 30 mmol h^?1. In addition to modifying habitat through physical structure, L. luymesi may be considered to be an ecosystem engineer because of its profound effect on the chemical environment at hydrocarbon seep sites.     

A comparison of relict versus equilibrium models for insular mammals of the Gulf of Maine

For the mammalian faunas of 24 landbridge islands in the Gulf of Maine (0.003–279 km² in size), area accounts for 86% of variance in species richness. The slope, z , of the species-area curve is 0.247. For the seven largest islands (>10km²), the non-equilibrium hypothesis of relaxation following saturation in the post-Pleistocene is suggested by (1) elevated slope of the species-area curve (0.353), (2) correlation of species richness with island age ( r =- 0.81) and water depth to mainland ( r = -0.70), (3) highly non-random nested subsets of species ranked by island area, and (4) discontinuity with the extremely depauperate faunas of oceanic islands of the eastern North Atlantic. The alternative hypothesis of a dynamic equilibrium determined by recurrent immigration and extinction is supported by (1) documented turnover in 16 species, (2) correlation of species-area residuals with distance ( r = - 0.90), (3) distribution dependent upon vagility with reduction or absence of hibernators and other poor dispersers, (4) low levels of endemism, and (5) congruence of community structure with that of mainland fauna for both trophic level and body size.
I conclude that while some insular populations may be relictual, the faunal composition of most of these islands is dependent on recurrent colonization, much of which takes place over ice bridges. However, true equilibrium is perturbed by climatic shifts, range expansions, and human disturbance.     

Sterrhurus carpentariae nov. sp. (Digenea: Hemiuridae) from Lapemis hardwickii (Serpentes: Hydrophiidae) from the eastern Gulf of Carpentaria,Australia

A new species of hemiurid is described from a sea snake.     

EFFECT OF SALINITY ON PSEUDO‐NITZSCHIA SPECIES (BACILLARIOPHYCEAE) GROWTH AND DISTRIBUTION1

Salinity varies widely in coastal areas that often have a high abundance of Pseudo‐nitzschia H. Peragallo. Pseudo‐nitzschia is abundant in Louisiana waters, and high cellular domoic acid has been observed in natural samples but no human illness has been reported. To assess the threat of amnesic shellfish poisoning (ASP), we examined the effect of salinity on Pseudo‐nitzschia occurrence in the field and growth in the laboratory with special emphasis on the salinity range where oysters are harvested (10–20 psu). In Louisiana coastal waters, Pseudo‐nitzschia spp. occurred over a salinity range of 1 to >35 psu, but they occurred more frequently at higher rather than lower salinities. Seven species were identified, including toxigenic species occurring at low salinities. In culture studies, seven clones of three species grew over a salinity range of 15 to 40 psu, some grew at salinities down to 6.25 psu, and most grew at salinities up to 45 psu. Tolerance of low salinities decreased from Pseudo‐nitzschia delicatissima (Cleve) Heiden to P. multiseries (Hasle) Hasle to P. pseudodelicatissima (Hasle) Hasle emend. Lundholm, Hasle et Moestrup. In conclusion, although Pseudo‐nitzschia was more prevalent in the field and grew better in the laboratory at higher salinities, it grew and has been observed at low salinities. Therefore, the probability of ASP from consumption of oysters harvested from the low salinity estuaries of the northern Gulf of Mexico is low but not zero; animal mortality events from toxin vectors other than oysters at higher salinity on the shelf are more likely.     

Association of the whale shark Rhincodon typus with the cannonball jellyfish Stomolophus meleagris

This study describes the first record of the whale shark Rhincodon typus association with the cannonball jellyfish Stomolophus meleagris in the Gulf of California, Mexico. Whale sharks were observed swimming and feeding among swarms of jellyfish, suggesting competition and predatory behaviour given the overlap in food preferences between both species. This finding is relevant because of the species‐wide distribution and the importance of these interactions, which should be considered in conservation strategies of R. typus and management of cannonball jellyfish fisheries.     

Contributions to the knowledge of subterranean trechine beetles in southern China’s karsts: five new genera (Insecta,Coleoptera, Carabidae,Trechinae)

Recent discoveries reveal that southern China’s karsts hold the most diverse and morphologically modified subterranean trechine beetles in the world, albeit the first troglobitic blind beetle was only reported in the early 1990’s. In total, 110 species belonging to 43 genera of cavernicolous trechines have hitherto been recorded from the karsts of southern China, including the following five new genera proposed below: Shiqianaphaenops Tian, gen. n., to contain two species: Shiqianaphaenops majusculus (Uéno, 1999) (= Shenaphaenops majusculus Uéno, 1999, comb. n.), the type species from Cave Feng Dong, Shiqian, Guizhou, and Shiqianaphaenops cursor (Uéno, 1999) (= Shenaphaenops cursor Uéno, 1999, comb. n.), from Cave Shenxian Dong, Shiqian, Guizhou; and the monotypic Dianotrechus Tian, gen. n. (the type species: Dianotrechus gueorguievi Tian, sp. n., from Cave Dashi Dong, Kunming, Yunnan), Tianeotrechus Tian & Tang, gen. n. (the type species: Tianeotrechus trisetosus Tian & Tang, sp. n., from Cave Bahao Dong, Tian’e County, Guangxi), Huoyanodytes Tian & Huang, gen. n. (the type species: Huoyanodytes tujiaphilus Tian & Huang, sp. n., from Longshan, Hunan) and Wanhuaphaenops Tian & Wang, gen. n. (the type species: Wanhuaphaenops zhangi Tian & Wang, sp. n., from Cave Songjia Dong, Chenzhou, Hunan).     

The Vermetidae of the Gulf of Kachchh,western coast of India (Mollusca,Gastropoda)

Coral reefs are often termed underwater wonderlands due to the presence of an incredible biodiversity including numerous invertebrates and vertebrates. Among the dense population of benthic and bottom-dwelling inhabitants of the reef, many significant species remain hidden or neglected by researchers. One such example is the vermetids, a unique group of marine gastropods. The present study attempts for the first time to assess the density and identify preferred reef substrates in the Gulf of Kachchh, state of Gujarat, on the western coast of India. A total of three species of the family Vermetidae were recorded during the study and their substrate preferences identified.     

Biological data from a data‐deficient shark: the Arabian smoothhound Mustelus mosis (Carcharhiniformes: Triakidae)

The present study provides information on length distribution, reproductive biology and diet of Mustelus mosis based on individuals caught in waters off the eastern Arabian Peninsula. Although ageing of vertebral centra was attempted, band pairs were of low clarity and counts could not be confidently assigned.     

Aragonite infill in overgrown conceptacles of coralline Lithothamnion spp. (Hapalidiaceae,Hapalidiales, Rhodophyta): new insights in biomineralization and phylomineralogy

New empirical and quantitative data in the study of calcium carbonate biomineralization and an expanded coralline psbA framework for phylomineralogy are provided for crustose coralline red algae. Scanning electron microscopy (SEM) and energy dispersive spectrometry (SEM‐EDS) pinpointed the exact location of calcium carbonate crystals within overgrown reproductive conceptacles in rhodolith‐forming Lithothamnion species from the Gulf of Mexico and Pacific Panama. SEM‐EDS and X‐ray diffraction (XRD) analysis confirmed the elemental composition of these calcium carbonate crystals to be aragonite. After spore release, reproductive conceptacles apparently became overgrown by new vegetative growth, a strategy that may aid in sealing the empty conceptacle chamber, hence influencing the chemistry of the microenvironment and in turn promoting aragonite crystal growth. The possible relevance of various types of calcium carbonate polymorphs present in the complex internal structure and skeleton of crustose corallines is discussed. This is the first study to link SEM, SEM‐EDS, XRD, Microtomography and X‐ray microscopy data of aragonite infill in coralline algae with phylomineralogy. The study contributes to the growing body of literature characterizing and speculating about how the relative abundances of carbonate biominerals in corallines may vary in response to changes in atmospheric pCO₂, ocean acidification, and global warming.     

Nitrate uptake varies with tide height and nutrient availability in the intertidal seaweed Fucus vesiculosus

Intertidal seaweeds must cope with a suite of stressors imposed by aerial exposure at low tide, including nutrient limitation due to emersion. Seaweeds can access nutrients only when submerged, so individuals living higher compared to lower on the shore may have adaptations allowing them to acquire sufficient amounts of nutrients to survive and maintain growth. Using a combination of observations and experiments, we aimed to identify intraspecific variation in nitrate uptake rates across the intertidal distribution of F. vesiculosus, as well as test for acclimation in response to a change in tide height. We replicated our study at sites spanning nearly the entire Gulf of Maine coastline, to examine how local environmental variability may alter intraspecific variation in nitrate uptake. We found that average nitrate uptake rates were ~18% higher in upper compared to lower intertidal Fucus vesiculosus. Furthermore, we found evidence for both acclimation and adaptation to tide height during a transplant experiment. F. vesiculosus transplanted from the lower to the upper intertidal zone was characterized by increased nitrate uptake, but individuals transplanted from the upper to the lower intertidal zone retained high uptake rates. Our observations differed among Gulf of Maine regions and among time points of our study. Importantly, these differences may reflect associations between nitrate uptake rates and abiotic environmental conditions and seaweed nutrient status. Our study highlights the importance of long‐term variation in ambient nutrient supply in driving intraspecific variation of seaweeds across the intertidal gradient and local and seasonal variation in ambient nutrient levels in mediating intraspecific differences.