Buoyancy In Seawater Research Articles

Multiple seed dispersal modes of an invasive plant species on coastal dunes

Beach evening-primrose (Oenothera drummondii subsp. drummondii) is a perennial herb native to the coastal dunes of the Gulf of Mexico and southeastern USA. During the last century, the species was unintentionally introduced into coastal dune systems around the world. The purpose of this study was to explore the means of dispersal of this invasive in the newly established populations on the coastal dunes of Spain and to determine if they contribute significantly to the invasion process. After reconstructing the history of its spread in Spain from available records, we tested whether dispersion by marine currents can be a mechanism of colonization at regional scale, and whether the presence of native vertebrate participate in the expansion process at local scale. Through laboratory experiments, we demonstrated that the seeds of O. drummondii can be dispersed by seawater, since 0.63% present both buoyancy in seawater and subsequent germination after being washed with fresh water. This capacity for dispersal by marine currents could explain both the expansion of the species along the southwestern coast of Spain and the maintenance of its populations following disturbances such as storms. We also demonstrated that Iberian Hares and European Rabbits can disperse the seeds by endozoochory; seeds recovered from faecal pellets of these species were capable of germination (73 and 63%, respectively). Oenothera drummondii has become an invader only in coastal dunes where these dispersers are present, and with no control actions to regulate their populations. In conclusion, O. drummondii is an alien species with varying dispersal methods, polychory. This helps maintain already established populations and disperses seeds at a regional level, depending on the incidence of storms and the presence or absence of rabbits and hares for efficient local seed dispersion. Thus, management actions that restrict marine and animal dispersal likely have the benefit of limiting the invasive potential of O. drummondii.

Bone Mineral Density Reduction Explains Buoyancy Adaptations in Notothenioids

In aquatic vertebrates, dense skeletons and buoyant fat constitute important components for buoyancy regulation in addition to their roles in structural support and energy storage. Some fishes can fine‐tune buoyancy using their swim bladder, whereas others rely on neutral buoyancy or constant motion to regulate vertical position. The Notothenioidei provides a model system to study the phenotypic implications of differential use of the water column over a large radiation of closely related species. It has been suggested that to expand from ancestral benthic to pelagic habitats, some notothenioids, all of which lack the swim bladder, have reduced skeletal mass and display enhanced lipid deposition. This, apparently, adaptive osteopenia has interesting medical implications in understanding the balance between osteopenic bone and structural integrity of the skeleton.While relative buoyancy in seawater (%B) and dry skeletal mass have previously been studied in some notothenioids, little is known about the specific anatomical changes resulting in osteopenia; hypotheses include reductions of bone mineralization, reductions in bone size, and/or modifications of bone architecture. Here we used a high‐throughput procedure relying on quantitative X‐ray computed tomography (qCT) imaging on a collection of 436 notothenioid specimens (7 families, 24 genera, 53 species) to measure overall volumetric bone mineral density (vBMD), body size‐adjusted mineral content of the entire skeleton (BMCtotal), vertebrae (BMCvertebrae), and skull bones (BMCskull), and body size adjusted lipid content (LC). Dual‐energy X‐ray absorptiometry and magnetic resonance imaging on a subsample of 50 specimens was used for BMCtotal and LC validation.For 33 species in the collection, %B was available from the literature and we performed phylogenetic generalized least‐squares analysis with seven models to explain buoyancy (%B ~ BMCtotal, %B ~ BMCskull, %B ~ BMCvertebrae, %B ~ BMCtotal + BMCskull, %B ~ BMCtotal + BMCvertebrae, %B ~ BMCtotal + BMCskull + BMCvertebrae, %B ~ LC). This phylogenetically informed multivariate data analysis showed that the model %B ~ BMCtotal + BMCvertebrae best described the data, thus evolutionary reductions in %B are best explained by reductions in both BMCtotal and BMCvertebrae.In a series of studies, Eastman et al. established the link between buoyancy, skeletal mass, and LC in notothenioids, most recently in a comprehensive report spanning 54 specimens of 20 species (Eastman et al. J Morphol. 2014, 275:841–61). The present result confirms on a much broader scale the correlation between bone mineral content and buoyancy, and shows that vertebrae are the most important bone type for overall reductions in BMC. Based on qCT, micro‐CT, histology, and mechanical testing, we seek to answer to which extend the reduction in BMC compromises the mechanical integrity of the bone.Support or Funding InformationUS National Science Foundation grant PLR‐1444167This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Conservation choice on the rare endangered plants Glehnia littoralis.

The coastal herbs Glehnia littoralis have been domesticated as traditional medicines for many centuries. The domestication may have caused changes or declines of cultivated G. littoralis (CGL) relative to wild G. littoralis (WGL). By comparing fruit properties of CGL and WGL, we tested the hypothesis that domesticated G. littoralis have suffered major declines, and human cultivation cannot be sufficient to conserve this species. We collected fruits of CGL and WGL in the Shandong peninsula, China, and compared their buoyancy in seawater, germination potential after seawater immersion, and thousand-grain weights. Float rates of the WGL and CGL fruits were 95.6 (mean) ± 2.6% (standard deviation) and 30.0 ± 7.1%, respectively. The germination potential of CGL was significantly reduced, although the thousand-grain weights of CGL (21.85 ± 0.17 g) were higher than those of the WGL fruits (14.73 ± 0.21 g). These results suggest that the CGL have experienced significant declines relative to the WGL, presumably due to the loss of seawater inundation, selection and dispersal. These declines disfavour the persistence of CGL, and human domestication and cultivation are believed to be insufficient for conserving G. littoralis. Sand coasts where WGL still persists should be designated timely as nature reserves to conserve this species.

OBSERVATION OF EMBRYONIC AND LAVAL DEVELOPMENT OF DEVIL STINGER, INIMICUS JAPONICUS

Artificial rearing technique for Inimicus japonicus was conducted at Xishan experimental ground of Zhejiang Marine Fisheries Research Institute from May to June 2011.After obtaining fertilized eggs by artificial insemination,we observed the embryonic and larval development of devil stinger using microscope and described the development time and morphological characteristics of each development stage,which provide basic information for the artificial breeding and early development.The results showed that fertilized eggs had perfectly spherical shape and were transparent,and average egg diameter was(1.42±0.04) mm and without oil globule.Furthermore,the eggs showed buoyancy in seawater at salinity 31.Embryos were incubated in seawater(salinity 31) at(22±0.5)℃.The time-table of major embryonic development stages of devil stinger were as follows: blastodisc forming stage at 15min post fertilization(pf);2-cell stage at 25min pf;multicellular stage at 4h and 10min pf;bastula stage at 7h and 20min pf;gastrula stage at 13h and 20min pf;neurula stage at 25h 40min pf;organogenesis stage at 26h 10min pf;tail bud stage at 38h 10min pf;heart beat stage at 40h 30min pf;muscular contraction stage at 46h 20min pf;pro-hatching stage at 52h 10min pf;hatching stage at 52h 10min pf.Newly hatched larvae usually lied on the water surface and had 3.0 mm in average in total length(TH) with yolk sac length of 2.2 mm and height 1.7 mm.The larvae relied on their yolk for nourishment before the 3rd day post hatching at(21±0.5) ℃.4 days later,the yolk sac was consumed completely and started ingesting rotifers.About 13 days after hatching,the whole body length was(7.1±0.35) mm and fin ray appeared on the dorsal fin,indicating the larvae began turned into juvenile.On day 15 post hatching,the whole body length was(7.92±0.61) mm,and golden yellow maculation occurred on each fin.On day 25,whole body length was(13.66±0.55) mm,metamorphosis was completed with yellow brown of total body and the fish turned into young fish,while accompanied by a change from planktonic habits to demersal habits.The morphological development and changes of pigment pattern from embryonic to juvenile stage were observed.Pectoral fin bud was developed early after the later stage of embryo together with the fan-shaped membrane.Three days later,3—5 melanin pigments appeared in the neighbor of pectoral fin border of larvae,and yellow pigments were clearly seen in the border with arc distribution.Six days later,a small amount of melanin pigment was developed in the distal end of pectoral fin and yellow pigments showed more intensity.Twenty days later,vivid golden yellow maculation occurred on the outsized? fan-shaped pectoral fin.Two fin rays at the below of pectoral fin of adult fish were connected without membrane,presenting the dissociation state.In the juvenile stage,these fin rays,like the other fin rays,was connected by membrane,subsequently became the free fin ray.From the morphological observation,it is thought that two dissociated fin rays on the pectoral fin were differentiated from the pectoral fin rays.

Relationship between egg specific gravity and egg quality in the Japanese eel, Anguilla japonica

Eggs from maturation-induced Japanese eels, Anguilla japonica, often sink in seawater immediately after artificial insemination and do not hatch. In the present study, the specific gravity of unfertilized eggs from individual females was measured in isotonic (about 310 mOsm/kg) and hypertonic (about 875 mOsm/kg) saline solutions and the relation of specific gravity to egg quality was examined. Egg specific gravity under isotonic conditions showed a significant negative correlation with egg fertility, hatchability and water content, suggesting that inadequate hydration of oocytes during final maturation, which leads to insufficient egg buoyancy, is one of the causes of poor egg quality. Some of the eggs that showed lower specific gravity than seawater under isotonic conditions exhibited higher specific gravity than seawater under hypertonic conditions, indicating that the buoyancy acquired by the eggs is sometimes lost after their transfer to seawater. Only eggs that retained low specific gravity under hypertonic as well as isotonic conditions exhibited high fertility and hatchability. Taken together with data from other studies, these results suggest that the poor quality of eggs that sink immediately after artificial insemination is attributable to at least two causes: the failure of oocytes to acquire sufficient buoyancy during maturation and the loss of buoyancy in seawater because of the inability of egg osmoregulation.

Early Development of Northeast Arctic Greenland Halibut (Reinhardtius hippoglossoides)

The early development of the Greenland halibut (Reinhardtius hippoglossoides) has not been described. This study presents some preliminary notes on the egg development of the Northeast Arctic Greenland halibut. Buoyancy and morphometric characteristics of artificially spawned eggs are compared with field sampled eggs, in order to identify these to species. The eggs in the ovary of ripening females were large (about 4 mm), transparent, almost equal in size and stuck to the walls of the ovary. In running, artificially spawned females the ovulated eggs were all easily released in one batch. This may indicate that Greenland halibut has a comparatively long period between each egg batch delivered. Artificially spawned eggs of the Greenland halibut had a diameter varying from 3.3 to 4.2 mm and a neutral buoyancy in seawater of ca. 33‰ (c. 5°C) during the first four days of development. During gastrulation the egg density increased until closure of blastopore. Eggs from field surveys had a diameter raging from 3.9 to 4.7 mm and a neutral buoyancy in seawater of 35.2‰ (ca. 5°C). This corresponds to a density near 1.0279 g/cm3. This density is found at depths around 650 m (34.9‰ salinity and 1.8°C) in the spawning

クロダイ仔稚魚の発育に伴う比重の変化

The specific gravity of black sea bream Acanthopagrus schlegeli larvae and juveniles was measured in a series of saline solutions. The volume of the swim bladder and wet and dry fish weights were also measured. During the egg and prelarval periods, they have a slightly positive or neutral buoyancy in sea water of ca. 1.024 specific gravity. During the postlarval period, specific gravity increased to a level ca. 1.028 and began to change diurnally. After inflation of the swim bladder, voluminal changes in it caused the postlarvae to be negatively buoyant during the day and neutlally buoyant at night. These changes could be induced by manipulation of the photocycle. No diel change in specific gravity could be detected in black sea bream of 20mm. These results indicate that levels in the specific gravity of black sea bream during the larval and juvenile periods are much lower than those reported for the red sea bream during this same period. It has been suggested that this difference influences the differences in behavior of these two sparids which results in differences in the vertical distribution from the pelagic to benthic life.

Water and salt balance of halibut eggs and larvae (Hippoglossus hippoglossus)

Eggs of halibut [Hippoglossus hippoglossus (L.)] have a negative buoyancy in sea water of 35‰ S, in contrast to eggs of most flatfish species. The cause of this was investigated. The osmolality of the yolk is 350–420 mOsm during embryonic development. This is within the range for marine teleost serum and for yolk of pelagic eggs. Concentrations of major inorganic ions are comparable with those of pelagic plaice eggs [Pleuronectes platessa (L.)]. The values for Na+, K+ and Cl- are 6, 85, and 64 mmol · (1 H2O)-1 after fertilization, and at the time of hatching the corresponding values are 17, 11, and 80. Large amounts of other inorganic constitutents are excluded for osmotic reasons. Malfunction in the regulation of osmolality or of inorganic constituents is thus unlikely to be the cause of negative buoyancy. The relative dry weight of the chorion (“egg shell”) in halibut eggs is less than in several pelagic egg types, excluding the chorion as the main contributor of negative buoyancy. It is concluded that a high content of organic matter in the rest of the egg is the cause of the negative buoyancy.

Lipid compositions, water contents, swimbladder morphologies and buoyancies of nineteen species of midwater fishes (18 myctophids and 1 neoscopelid)

Lipid compositions, water contents, swimbladder morphologies and specific gravities were studied for 19 species of oceanic midwater fishes, chiefly myctophids (lanternfishes) collected offshore from Oregon and California from 1975–1979. Three groups of species were recognizable. The first group had bodies low in both lipid and water content; they were denser than seawater, regardless of swimbladder morphology, which varied from absent through non-inflated to inflated. The second group had bodies low in lipid but high in water content; they were neutrally buoyant, evidently because of their high content of water, although their swimbladders were never inflated. The majority of the members of the aforementioned groups contained higher proportions of triglycerides than wax esters. The third group had bodies with high lipid but low water content; those with high triglyceride content had swimbladders ranging from non-inflated to (less commonly) inflated, were denser than seawater, and the lipid percentage of their body weights varied both with size and season, indicating that triglycerides function mainly as an energy store. The adults of species in the third group with a higher content of wax esters than triglycerides lacked inflated swimbladders, were neutrally buoyant, and the lipid percentage of their body weights was relatively constant with size and season, indicating that wax esters permit these fishes to attain neutral buoyancy in seawater.

Density regulation inSarsia tubulosa (Hydrozoa)

The majority of wild-caughtSarsia tubulosa M. Sars medusae are less dense than the surrounding water. The bell ofS. tubulosa is the buoyant structure; the tentacles and manubrium sink if cut off from the bell.S. tubulosa individuals placed in dilute seawater sink initially but recover positive or neutral buoyancy and normal activity within a couple of hours. In all cases observed animals were able to achieve positive buoyancy in seawater of 20.25 ‰ S and some individuals were able to adjust to lower salinities. In most cases where positive buoyancy was not attained within two hours the animal did not achieve positive buoyancy within twelve hours and died within that period. While the mechanism of regulation is not known, ionic pumping, possibly involving the extrusion of sulphate ion, has been suggested to be responsible for the buoyancy of mesoglea in other jellyfishes.

Salt Water Tolerance of Seeds of Gossypium Species as a Possible Factor in Seed Dispersal

Several wild species, and wild forms of the cultivated species of Gossypium occupy coastal or insular habitats. The seeds and/or capsules of these forms have a limited buoyancy in sea water, which is, however, sufficient to provide opportunity for dispersal along shore-lines, to off-shore islands, and from island to island in certain cases. Seeds of coastal and insular forms usually have hard seed coats and can remain viable after long periods of immersion in sea water. The seeds of Gossypium barbadense var. darwinii have both sufficient buoyancy and salt water tolerance to have enabled them to reach the Galapagos Islands from the mainland of South America. The possible roles of man and ocean currents in the dispersal of these cottons is discussed.