Tetrodotoxin (TTX) producing bacteria have been isolated from four species of planktonic chaetognaths: Flaccisagitta lyra. Parasagitta elegans. Zonosagitta nagae. and Eukrohnia hamala. TTX production in bacterial isolates from the four species of venomous chaetognath species was indicated by neuroblastoma cell culture bioassay and high performance liquid chromatography. A common species of marine bacterium, \~ibrio alginolyticits, was identified as most likely responsible for the production of TTX. Extracellular TTX in the culture medium at concentrations of 280-790 pg/ml indicated that I '. alginolyticus may be sufficiently capable of replenishing venom TTX within 24 h. It is suggested that this bacterium lives associated with these chaetognaths and is responsible for the production of the TTX in chaetognath venom.
The teeth of Flaccisagitta hexaptera are capable of penetrating the exoskeleton of copepods. The grasping spines, anterior, and posterior teeth are all capable of piercing the epidermis of larval fish as seen in a series of scanning electron micrographs. A new type of anterior tooth structure is observed. A chemosensory function is suggested for a new set of pores found between the sets of anterior teeth. The secretory nature of the vestibular pit is clearly seen for the first time.
Our perception of deep-sea communities has evolved as various sampling approaches have captured different components of deep-sea habitats. We sampled midwater zooplankton assemblages in Monterey Bay, California to quantify community composition (abundance and biomass) and biodiversity (at the Order level) across three depth ranges, and the effects of sampling methodology on community parameters. We collected zooplankton using two types of opening-closing trawls [Tucker Trawl and Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS)] and video recordings from a remotely operated vehicle (ROV). We quantified the relative contributions of microbes to community biomass using synoptic water-bottle casts and flow cytometry. Overall, the pelagic community was most similar between the Tucker trawl and ROV (dissimilarity = 52.4%) and least similar between the MOCNESS and ROV (dissimilarity = 65.8%). Dissimilarity between sampling methods was driven by the relative abundances of crustaceans and gelatinous taxa, where gelatinous animals (cnidarians, ctenophores, tunicates) were more abundant in ROV surveys (64.2%) and Tucker trawls (46.8%) compared to MOCNESS samples (14.5%). ROV surveys were the only method that sufficiently documented the most physically delicate taxa (e.g., physonect siphonophores, lobate ctenophores, and larvaceans). Biomass was also one order of magnitude lower in MOCNESS trawls compared to Tucker trawls. Due to these large differences, the relative contributions of microbes to total biomass were substantially lower in Tucker trawl samples (mean = 7.5%) compared to MOCNESS samples (mean = 51%). These results illustrate that our view of planktonic composition and community biomass is strongly dependent on sampling methodology.
A new species of deep-sea jellyfish, Crossota millsae (Cnidaria: Hydrozoa: Trachymedusae: Rhopalonematidae), is described from the North Pacific Ocean off California and Hawaii. Discrete depth sampling showed this species lives at depths below 1000 meters in both geographic locations. The species is more abundant off California than off Hawaii. The greatest population densities were found at~2500 m off California and at~1250 m off Hawaii. The burnt-tangerine color of the inner bell and bright pink to lavender color of the ring and radial canals, manubrium and gonads make living specimens of this species difficult to confuse with any other known species of hydromedusa. Sexually dimorphic differences in gonad morphology are evident. The pendant testes contained spermatids at various stages of spermatogenesis as observed using scanning electron microscopy. Ova develop directly into small medusae that reside subumbrellarly between the radial canals of the mother. Various developmental stages of C. millsae are shown in photographs and terminology of brooding and viviparity is discussed relative to other Cnidaria.
Vampyroteuthis infernalis is a cosmopolitan cephalopod that lives in the oxygen minimum layer between 600 and 800 m depth. Morphometric and physiological studies have indicated that V. infernalis has little capacity for jet propulsion and has the lowest metabolic rate ever measured for a cephalopod. Because fin swimming is inherently more efficient than jet propulsion, some of the reduction in energy usage relative to other cephalopods may result from the use of fins as the primary means of propulsion. V. infernalis undergoes a rapid metamorphosis which consists of changes in the position, size and shape of the fins. This suggests that there are changes in the selective factors affecting locomotion through ontogeny. The present study describes these changes in relation to models for underwater 'flight'. Citrate synthase (CS) and octopine dehydrogenase (ODH) activities, indicative of aerobic and anaerobic metabolism, respectively, were measured in fin, mantle and arm tissue across a range of body size of four orders of magnitude. The low enzymatic activities in both posterior and anterior fin tissue and the relatively high activity in mantle muscle prior to metamorphosis indicate that jet propulsion using mantle contraction is the primary means of propulsion in juvenile V. infernalis. The increase in CS activity with size after metamorphosis suggests an increased use of the fins for lift-based propulsion. Fin swimming appears to be the primary means of propulsion at all adult sizes. The negative allometry of CS activity in mantle and arm muscle is consistent with the scaling of oxygen consumption previously measured for V. infernalis and with the scaling of aerobic metabolism observed in most animals. The unusual positive allometry of fin muscle CS activity suggests that the use of fins is either relatively more important or more costly in larger animals. Positive scaling of ODH activity in all tissues suggests that fin propulsion, jet propulsion and medusoid 'bell-swimming' are all important for burst escape responses. Enzyme activities in Cirrothauma murrayi are consistent with fin-swimming observed from submersibles, while those in Opisthoteuthis californiana suggest a strong reliance on medusoid swimming using the arms. The transition from jet propulsion to paired-fin 'flight' with increasing body size in Vampyroteuthis infernalis appears functionally to be an ontogenetic 'gait-transition'.
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