Fishing, trophic cascades, and the process of grazing on coral reefs

Since the mass mortality of the urchin Diadema antillarum in 1983, parrotfishes have become the dominant grazer on Caribbean reefs. The grazing capacity of these fishes could be impaired if marine reserves achieve their long-term goal of restoring large consumers, several of which prey on parrotfishes. Here we compare the negative impacts of enhanced predation with the positive impacts of reduced fishing mortality on parrotfishes inside reserves. Because large-bodied parrotfishes escape the risk of predation from a large piscivore (the Nassau grouper), the predation effect reduced grazing by only 4 to 8%. This impact was overwhelmed by the increase in density of large parrotfishes, resulting in a net doubling of grazing. Increased grazing caused a fourfold reduction in the cover of macroalgae, which, because they are the principal competitors of corals, highlights the potential importance of reserves for coral reef resilience.     

Ellipsosomes: organelles containing a cytochrome-like pigment in the retinal cones of certain fishes

Ellipsosomes are dense spherical bodies containing a very large concentration of a heme pigment spectroscopically resembling pure cytochrome c. They are located at the outer ends of the inner segments of the cones of certain fishes. Although, superficially, they resemble the similarly located oil droplets in the cones of birds and reptiles, their ultrastructure and staining properties resemble those of the neighboring mitochondria. However, like the oil droplets, they may serve as intracellular color filters.     

川滇高原湖泊鱼类分布的聚类分析

对川滇高原湖泊鱼类的聚类分析表明,14个湖泊鱼类分布在种(亚种)级和属级均具有相似性。属级的相似性程度很低,但仍反映出它们在鱼类区系形成上的共同源流;种(亚种)级间的差异显著,反映了地理隔离和生态隔离对鱼类物种形成和分化过程中双重因素的严重影响。本文还对其相似性和差异性的形成因素作了分析。     

Role of the gastropod shell and operculum in inhibiting predation by fishes

In contrast to the diets of other cottid fishes and most teleosts, the diet of Asemichthys taylori is dominated by gastropod mollusks. Access to this underused prey appears to be made possible by morphological speializations of the neurocanium that allow Asemichthys to puncture the shells of its prey during mastication. Unpunched, the shell and operculum act as a barrier to digestion; more than 40% of the unpunched gastropods emerged alive in the feces. Asemichthys adjusted its punching behavior in an apparently adaptive way; other prey lacking such barriers to digestion were rarely punched. The ability of some shelled invertebrates to avoid digestion may make them less desirable as prey for many fishes that cannot masticate this kind of prey. The ability of shelled mollusks to survive in the digestive tracts of vertebrates may provide a dispersal mechanism for otherwise sedentary species.     

几种淡水小型鱼类吞食粘性鱼卵的初步观察

通过在室内进行８种淡水小型鱼类吞食鱼卵的试验观察表明：小型鱼吞食鱼卵带有普遍性，吞食强度依次为宽鳍、麦穗鱼、马口鱼、虎鱼、棒花鱼、鱼旁鱼皮、银鱼句、，其中７种鱼具有昼夜摄食节律，高峰期各异，但每天皆有１６ｈ的停食期．由此可见，小型鱼类通过摄食鱼卵，对能够在湖泊水库中自然繁殖的经济鱼类及凶猛鱼类的种群具有一定调控作用，对公鱼等孵化期较长的鱼类移植效果产生不良影响     

Community structure of corals and reef fishes at multiple scales

Distributions of numerical abundance and resource use among species are fundamental aspects of community structure. Here we characterize these patterns for tropical reef fishes and corals across a 10,000-kilometer biodiversity gradient. Numerical abundance and resource-use distributions have similar shapes, but they emerge at markedly different scales. These results are consistent with a controversial null hypothesis regarding community structure, according to which abundance distributions arise from the interplay of multiple stochastic environmental and demographic factors. Our findings underscore the importance of robust conservation strategies that are appropriately scaled to the broad suite of environmental processes that help sustain biodiversity.     

Evolution of urea synthesis in vertebrates: the piscine connection

Elasmobranch fishes, the coelacanth, estivating lungfish, amphibians, and mammals synthesize urea by the ornithine-urea cycle; by comparison, urea synthetic activity is generally insignificant in teleostean fishes. It is reported here that isolated liver cells of two teleost toadfishes, Opsanus beta and Opsansus tau, synthesize urea by the ornithine-urea cycle at substantial rates. Because toadfish excrete ammonia, do not use urea as an osmolyte, and have substantial levels of urease in their digestive systems, urea may serve as a transient nitrogen store, forming the basis of a nitrogen conservation shuttle system between liver and gut as in ruminants and hibernators. Toadfish synthesize urea using enzymes and subcellular distributions similar to those of elasmobranchs: glutamine-dependent carbamoyl phosphate synthethase (CPS III) and mitochondrial arginase. In contrast, mammals have CPS I (ammonia-dependent) and cytosolic arginase. Data on CPS and arginases in other fishes, including lungfishes and the coelacanth, support the hypothesis that the ornithine-urea cycle, a monophyletic trait in the vertebrates, underwent two key changes before the evolution of the extant lungfishes: a switch from CPS III to CPS I and replacement of mitochondrial arginase by a cytosolic equivalent.     

Adaptive female-mimicking behavior in a scorpionfly

This study provides a clear example of female-mimicking behavior by males in insects and evaluates quantitatively the adaptive significance of this behavior, which is poorly understood in many other organisms. Males of Hylobittacus apicalis provide females with a prey arthropod during copulation. Some males mimic female behavior when interacting with males that have captured nuptial prey, resulting in males stealing prey which they will use for copulation. Males that pirate prey copulate more frequently and probably incur fewer predation-related risks.     

Formation of giant planets by fragmentation of protoplanetary disks

The evolution of gravitationally unstable protoplanetary gaseous disks has been studied with the use of three-dimensional smoothed particle hydrodynamics simulations with unprecedented resolution. We have considered disks with initial masses and temperature profiles consistent with those inferred for the protosolar nebula and for other protoplanetary disks. We show that long-lasting, self-gravitating protoplanets arise after a few disk orbital periods if cooling is efficient enough to maintain the temperature close to 50 K. The resulting bodies have masses and orbital eccentricities similar to those of detected extrasolar planets.     

Fast trap jaws and giant neurons in the ant odontomachus

Ants of the ponerine genus Odontomachus use a trap jaw mechanism when hunting fast prey. When particular trigger hairs, located on the inner edge of the mandibles, are touched by prey, the jaws close extremely rapidly and trap the target. This trap jaw response lasts only 0.33 to 1 millisecond. Electrophysiological recordings demonstrated that the trigger hairs function as mechanoreceptors. Associated with each trigger hair are large sensory cells, the sensory axons of which measure 15 to 20 micrometers in diameter. These are among the largest sensory neurons, and their size implies that these axons conduct information very rapidly.     

河鲀和河鲀毒素之间关系的研究进展

从中国有毒河鲀的种类和分布、河鲀体内的河鲀毒素的来源、河鲀对河鲀毒素的耐受性、人工养殖河鲀的河鲀毒性等四个方面,介绍了当前国内外河鲀与河鲀毒素关系的研究进展情况,并提出了关于河鲀体内的河鲀毒素来源的新观点,认为河鲀体内的河鲀毒素可能是河鲀以细菌产生的河鲀毒素类似物为前体,生物合成而成的。养殖河鲑的毒性控制,需同时考虑食物链和河鲀本身的因素。     

Abortion, illegitimacy, and the American birth rate

In sum, it appears that legal abortion depressed overall fertility, but particularly illegitimate fertility, by giving women an opportunity to terminate their pregnancies when other means of birth control either had not been used or had failed. If legalized abortion had not been available, an estimated additional 39,000 illegitimate babies and 28,000 legitimate babies would have been born in 1971 in the United States. While this makes up a small part of total births (3,500,000), the illegitimate births prevented represent almost onetenth of all out-of-wedlock children born in the country in that year. In addition to preventing these births the legalization of abortion appears to have reduced the incidence of pregnancy-related marriages and thereby may have helped to limit subsequent marital disruption. Finally, legal abortion prevented large numbers of illegal abortions from occurring. Our data indicate that well over half-most likely between two-thirds and three-fourths-of all legal abortions in the United States in 1971 were replacements for illegal abortions. Further declines in illegitimate birth rates for the country as a whole will depend, in considerable part, on the extent to which legal abortion becomes more readily available and more widely used. Theoretically, greater use of efficient contraception could also cause illegitimate fertility to decline. But there are many reasons why women do not use efficient contraception even when they know about it and have access to the materials (25). Even though the use of abortion throughout the nation is now legalized by the Supreme Court decision, this does not necessarily mean that services will in fact be everywhere more readily available. Our interstate analysis suggests that should the liberalization of abortion laws be reversed, not only would there be an upturn in illegal abortions and pregnancy-related marriages, but also a marked rise in illegitimacy, particularly among women who do not have the means to obtain an illegal abortion.     

Brain peptides: what, where, and why?

Within the past decade, a large number of peptides have been described within the vertebrate central nervous system. Some of these peptides were previously known to be present in nonneural vertebrate tissues, as well as in lower species, in which they may serve as primitive elements of intercellular communication prior to the development of neuronal or endocrine systems. In vertebrates, these peptides are thought to have neurotransmitter or neuromodulatory roles and appear to be involved in the regulation of a number of homeostatic systems, although the mechanisms of their actions are still unclear.     

Origin of whales in epicontinental remnant seas: new evidence from the early eocene of pakistan

Pakicetus inachus from the early Eocene of Pakistan is the oldest and most primitive cetacean known. The dentition of Pakicetus resembles that of carnivorous mesonychid land mammals as well as middle Eocene cetaceans. The otic region of the cranium lacks characteristic specializations of whales necessary for efficient directional hearing under water. Pakicetus occurs with a land-mammal fauna in fluvial sediments bordering epicontinental Eocene remnants of the eastern Tethys seaway. Discovery of Pakicetus strengthens earlier inferences that whales originated from terrestrial carnivorous mammals and suggests that whales made a gradual transition from land to sea in the early Eocene, spending progressively more time feeding on planktivorous fishes in shallow, highly productive seas and embayments associated with tectonic closure of eastern Tethys.     

Microvolt electric signals from fishes and the environment

Pulses in the 0.01 to 40 microvolt range, probably generated by white fiber muscle action potentials, were remotely received through dipole antennae from five fishes and one amphibian in aquarium tests. In natural environments, however, no biologically generated signals have been detected. Received instead were a multitude of similar signals originating from unknown sources. The dominant types of these "atmospheric" signals and their reception rates change diurnally and can easily be confused with the fish-generated signals.     

几种近海底层鱼类和中上层鱼类隐蔽伪装色的比较

为了探明近海不同生态类型鱼类隐蔽伪装色的差异,研究了6种中上层鱼类和5种底层鱼类的隐蔽伪装色,结果表明:无论近海中上层鱼类(包括大甲鲹Megalaspis cordyla、斑■Hemiramphus far、五条■Seriola quinqueradiata、竹■鱼Trachurus japonicus、蓝圆鲹Decapterus maruadsi、蓝点马鲛Scomberomorus niphonius)还是近海底层鱼类(海鳗Muraenesox cinereus、斑尾复虾虎鱼Synechogobius ommaturus、带鱼Trichiurus japonicus、单角革鲀Aluterus monoceros、龙头鱼Harpadon nehereus),黑色素细胞和黄色素细胞均为背部多腹部少,差异显著;相比近海底层鱼类,近海中上层鱼类背腹部体色差异更加明显,中上层鱼类黑色素细胞和黄色素细胞差异更大;虹彩细胞在背腹部皮肤中都存在,而近海底层鱼类的腹部主要为虹彩细胞;红色素细胞在近海底层鱼类中很少存在,但在中上层鱼类中较多。上述结果显示,鱼类背部体色的深浅主要与皮肤中黑色素细胞和黄色素细胞的数量有关,腹部体色的形成主要与虹彩细胞的多少有关。     

春兰人工诱变的研究

以春兰种子和茎尖为外植体进行组织培养，形成原球茎后，用紫外光和秋水仙素进行人工诱变，结果表明：较高剂量的紫外光照射，可导致细胞核的变形、皱缩、线粒体液泡化，在一定照射剂量的条件下，可提高细胞无丝分裂的频率，其中以劈裂式无丝分裂的频率最高，诱发再生植株出现多种变异，用一定剂量的秋水仙素处理，也出现一些变异植株，但机率较少。     

西北太平洋公海日本鲭(Scomber japonicus)胃含物及其摄食等级研究

为了解我国公海灯光围网渔业开发现状及其主要渔获经济品种的基础生物学及其食性特征,根据2016年8-11月及2017年4-11月在西北太平洋公海生产船取样的日本鲭（Scomber japonicus）基础生物学现场测定数据,对其食性特征、摄食等级、生态位宽度等进行研究。结果表明,西北太平洋日本鲭主要摄食虾类、鱼类和桡足类等9大类16小类饵料生物,其中,虾类是最重要的饵料种类,以磷虾类最多;鱼类以未定种鱼类和远东拟沙丁鱼（Sardinops sagax）为主,鱼类饵料的质量百分比（W）比虾类高,但数量比例（N）不及虾类一半。日本鲭在夏、秋季比冬、春季胃含物种类的丰富度、摄食等级相对更高,具有一定的季节性变化。叉长小于300 mm或体质量小于300 g的日本鲭摄食强度与胃饱满指数（P）无明显变化;叉长大于300 mm或体质量大于300 g时,摄食等级与胃饱满指数均随体长或体质量增大呈现增大趋势;叉长大于300 mm的日本鲭由于摄食更多大型饵料,生态位宽度比叉长小于300mm的日本鲭普遍低。结果为今后西北太平洋日本鲭渔业的资源管理及可持续开发提供基础依据。     

广东鲂(♀)×团头鲂()杂交子一代及其双亲同工酶的比较

采用聚丙烯酰胺垂直平板电泳法对广东鲂、团头鲂及其杂交子一代肌肝眼 3种组织的 4种同工酶(EST、LDH、MDH、SOD)进行电泳 ,分析其酶谱组成和活性差异。结果显示父母本同种组织中大部分同工酶的表达酶谱较相似 ,尤其以眼组织的LDH、肝组织的MDH以及 3种组织的SOD同工酶的表型最为相似 ,表明两种鱼的亲缘关系较近 ,是本远缘杂交成功的遗传物质基础。同时父母本的某些同工酶谱又存在有稳定的种间差异 ,如肝组织的LDH。杂交子一代同工酶表型有些具有来自双亲的区带总和 ,有些则单独表达父本或母本的基因 ,更有些出现父母本没有的表型     

Freezing resistance in polar fishes

Arctic and antarctic fishes, living in contact with sea ice at -1.9 degrees C, have plasma equilibrium freezing points near -1.2 degrees C which are dependent on salt concentrations. These supercooled fishes have plasma protein concentrations much higher than other polar animals have, and the proteins impede ice propagation at temperatures down to -2 degrees C. Plasma protein concentration increases as environmental water temperature decreases.