五种裂腹鱼亚科鱼类外胚层发育不良因子A受体基因Edar的克隆和序列分析

裂腹鱼亚科鱼类具有丰富的体表附属器官变异,而Edar是控制这类结构发育的关键基因。以5种裂腹鱼的代表物种为材料克隆其Edar基因的编码区片段,序列分析表明:该基因编码的蛋白在裂腹鱼中存在长度不同的组氨酸重复序列,串联组氨酸插入可能与蛋白定位有关;基因树支持裂腹鱼与金线鲃具有最近的亲缘关系;分子进化分析未检测到正选择信号,裂腹鱼Edar基因的低复杂区可能是受选择区域。以上结果说明裂腹鱼Edar基因的结构变异可能与裂腹鱼表型变异和演化有关。     

The Renin-Angiotensin System in Fishes

It has been suggested that the renin-angiotensin system (RAS)in mammals may participate in the control of blood pressure,regulation of aldosterone secretion, or in renal functions byinfluencing intrarenal hemodynamics, or possibly by directlyaltering renal tubular sodium reabsorption. Comparative studieshave shown that this system is present among most vertebrates.Renal renin activity and juxtaglomerular cells (JGC), the possiblesite of formation and accumulation of renin, have not been foundin the cyclostomes and elasmobranchs. They seem to have evolvedin primitive bony fishes, being present in all living groupsof actinopterygians and sarcopterygians. Both renin and JGCmay also exist in a holocephalian, the ratfish, Hydrolagus colliei.The functions of the RAS are not yet denned in fishes. Thereis no clear evidence for sodium retaining function of the RASin fishes. Fish angiotensins (angiotensin-like substances) havechemical properties that differ from those of mammals and othertetrapods. It is possible that they also serve quite differentfunctions in fishes than in mammals.     

Long Term Effect of Cyprinid Fishes on Phytoplankton and Zooplankton Communities in a Shallow Water Protection Reservoir

The effects of fish kill and different fish stocks on the phytoplankton and zooplankton dynamics were studied in a shallow hypertrophic reservoir system. When fish stock was below 100 kg ha⁻¹, nutrient availability was not the main limiting factor for growth of phytoplankton. Consequently top‐down forces controlled phytoplankton. In the years with high fish stock (>100 kg ha⁻¹) the bottom‐up forces dominated as nutrient availability was the main limiting factor for growth of phytoplankton. We can conclude that significant water quality improvement can be achieved in the reservoir system by decreasing fish stock below 100 kg ha⁻¹. Although clear‐water phase could be stabilised temporary by macrophytes, stabilisation of good water quality requires continuous regulation of fish community. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Endocranial Anatomy of Therizinosauria and Its Implications for Sensory and Cognitive Function

Background

Therizinosauria is one of the most enigmatic and peculiar clades among theropod dinosaurs, exhibiting an unusual suite of characters, such as lanceolate teeth, a rostral rhamphotheca, long manual claws, and a wide, opisthopubic pelvis. This specialized anatomy has been associated with a shift in dietary preferences and an adaptation to herbivory. Despite a large number of discoveries in recent years, the fossil record for Therizinosauria is still relatively poor, and cranial remains are particularly rare.

Methodology/Principal Findings

Based on computed tomographic (CT) scanning of the nearly complete and articulated skull of Erlikosaurus andrewsi, as well as partial braincases of two other therizinosaurian taxa, the endocranial anatomy is reconstructed and described. The wider phylogenetic range of the described specimens permits the evaluation of sensory and cognitive capabilities of Therizinosauria in an evolutionary context. The endocranial anatomy reveals a mosaic of plesiomorphic and derived characters in therizinosaurians. The anatomy of the olfactory apparatus and the endosseous labyrinth suggests that olfaction, hearing, and equilibrium were well-developed in therizinosaurians and might have affected or benefited from an enlarged telencephalon.

Conclusion/Significance

This study presents the first appraisal of the evolution of endocranial anatomy and sensory adaptations in Therizinosauria. Despite their phylogenetically basal position among maniraptoran dinosaurs, therizinosaurians had developed the neural pathways for a well developed sensory repertoire. In particular olfaction and hearing may have played an important role in foraging, predator evasion, and/or social complexity.     

Five New Species of Henneguya (Protozoa: Myxosporida) from Ictalurid Fishes*

SYNOPSIS. Four new species of Henneguya (myxosporidan) are described from Ictalurus punctatus Rafinesque (channel catfish). They are as follows: Henneguya postexilis sp. n. and Henneguya longicauda sp. n. from the gills; Henneguya adiposa sp. n. from the adipose fin; and Henneguya diversis sp. n. from the liver, kidney, connective tissue of muscles and fins, and tumor-like external growths. Henneguya pellis sp. n. is described from the dermis of Ictalurus furcatus (LeSueur) (blue catfish). The development stages of all described species are discussed. Henneguya exilis Kudo was found on the gills of one I. punctatus; notes on its spore characteristics are presented.     

Viviparity: The Maternal-Fetal Relationship in Fishes

SYNOPSIS. Viviparity in the vertebrate line first makes itsevolutionary appearance among fishes. It has independently evolvedin a number of divergent piscine lineages. The 54 families ofextant fishes that bear living young include 40 families ofchondrichthyans (sharks and rays), one montypic family of coelacanths(Latimeria), and 13 families of teleosts. There is fossil evidencefor viviparity in holocephalans and chondrosteans. Viviparitypredominates among sharks and rays (40 families, 99 genera,420 species) but is less widespread among teleosts (13 families,122 genera, 510 species). Following an historical introduction,the organization of the female reproductive system, sites ofgestation, developmental sequences and superfetation are considered.The evolution of viviparity establishes specialized maternal-fetalrelationships, viz., 1) developmental, 2) morphological, 3)trophic, 4) osmoregulatory, 5) respiratory, 6) endocrinological,and 7) immunological. While the latter four categories are brieflynoted the major emphasis is on the trophic relationship andits morphological and developmental basis. First, a generaloverview is presented and then the maternal-fetal trophic relationshipsin each of the major groups of fishes are systematically reviewed.Pertinent anatomical, histological, ultrastructural, developmental,physiological, and biochemical studies are considered. Viviparousfishes are either lecithotrophic, i.e., exclusively yolk dependent,or matrotrophic, i.e., in receipt of a continuous supply ofmaternal nutrients during gestation. Nutrient transfer is accomplishedby 1) oophagy and adelphophagy, 2) placental analogues, and3) the yolk sac placenta. Placental analogues include: externalepithelial absorptive surfaces, e.g., skin, fins, gills; trophonemata,modifications of the uterine epithelia for the secretion ofhistotrophe or "uterine milk"; branchial placentae, close appositionbetween gill epithelia and either uterine or ovarian epithelialvilli; the yolk sac; pericardial amnion and chorion; follicularpseudoplacenta, close apposition between follicle cells andembryonic absorptive epithelia; hypertrophied gut; and trophotaeniae,external rosette or ribbon-like projections of the embryonicgut. Among chondrichthyans, the yolk sac placenta (840–1,050%),trophonematal secretion and embryonic absorbtion of histotrophe(1,680–4,900%) and oophagy and adelphophagy (1.2 x 106%)are the most efficient methods of nutrient transfer. Among teleosts,the follicular pseudoplacenta (1,800–3,900%), trophotaeniae(8,400%) and absorption of ovarian histotrophe through surfaceepithelia and a hypertrophied gut (1,100–34,000%) arethe most efficient. These values stand in contrast to the 30%40%loss of dry weight characteristic of oviparous fishes and viviparouslecithotrophes.     

The Evolution of Thyroidal Function in Fishes

Although the thyroid gland evolved from the gut, there is noevidence that thyroxine functions as part of the gastro-intestinalendocrine system nor does it have any major function analogousto the control of glucose by the pancreatic islets. The controlof the thyroid evolved from the pituitary control of the gonadsuggesting that an early role of thyroxine was in reproduction.This idea is supported by the presence of cycles of thyroidactivity associated with reproduction in both elasmobranchsand teleosts. In teleosts thyroxine is necessary for gonadalmaturation. The numerous other effects of thyroxine in teleostsmay have evolved from this maturational effect or have beenadded to it during the course of teleost evolution.     

The Physiology and Evolution of Urea Transport in Fishes

This review summarizes what is currently known about urea transporters in fishes in the context of their physiology and evolution within the vertebrates. The existence of urea transporters has been investigated in red blood cells and hepatocytes of fish as well as in renal and branchial cells. Little is known about urea transport in red blood cells and hepatocytes, in fact, urea transporters are not believed to be present in the erythrocytes of elasmobranchs nor in teleost fish. What little physiological evidence there is for urea transport across fish hepatocytes is not supported by molecular evidence and could be explained by other transporters. In contrast, early findings on elasmobranch renal urea transporters were the impetus for research in other organisms. Urea transport in both the elasmobranch kidney and gill functions to retain urea within the animal against a massive concentration gradient with the environment. Information on branchial and renal urea transporters in teleost fish is recent in comparison but in teleosts urea transporters appear to function for excretion and not retention as in elasmobranchs. The presence of urea transporters in fish that produce a copious amount of urea, such as elasmobranchs and ureotelic teleosts, is reasonable. However, the existence of urea transporters in ammoniotelic fish is curious and could likely be due to their ability to manufacture urea early in life as a means to avoid ammonia toxicity. It is believed that the facilitated diffusion urea transporter (UT) gene family has undergone major evolutionary changes, likely in association with the role of urea transport in the evolution of terrestriality in the vertebrates.     

Endocranial hyperostosis in Sangiran 2, Gibraltar 1, and Shanidar 5

Sangiran hominid 2 (S-2), Gibraltar hominid 1 (G-1), and Shanidar hominid 5 (SH-5) exhibit previously undescribed bilateral, paramedian hyperostosis of the endocranial frontal squama that spares the frontal crest, sagittal sinus, and ectocranial surface. The hyperostosis is localized to the frontal (usually the middle third) and parietal and is consistent with a diagnosis of hyperostosis calvariae interna (HCI), inclusive of hyperostosis frontalis interna. The hyperostosis in these specimens is compared to fossil hominids from Indonesia and Europe and to modern human cases of HCI. The three cases of HCI reported here document the existence and frequency of HCI in fossil hominids and push the antiquity of the disease back to nearly 1.5 millin years. The relatively great incidence of HCI in fossil hominids adds another confounding factor to the problematical issue of the taxonomic significance of cranial vault thickness. Am J Phys Anthropol 102:111–122. © 1997 Wiley-Liss, Inc.     

The Question of a Presupracleithrum in Brachiopterygian Fishes

The presupracleithrum is an exoskeletal pectoral bone that occurs in Paleozoic and Mesozoic actinopterygian fishes. It has been equated more than once with an opercular element in brachiopterygian fishes. In recent cladistic analyses, this alleged homology is used to assign brachiopterygians to actinopterygians. However, a comparison of brachiopterygian and actinopterygian crania shows clearly that the former lack a presupracleithrum.     

Glucagon-like Peptide-1 in Fishes: The Liver and Beyond

The incretin hormone glucagon-like peptide-1 (GLP-1), coencodedand expressed in the proglucagon gene in intestine and endocrinepancreas of all vertebrates, is an important regulator of insulinsecretion in the postprandial state of mammals. Additionally,the hormone acts in concert with insulin to remove glucose fromthe plasma. In mammalian B cells, lung, intestine and brain,GLP-1 receptors activate the adenylyl cyclase/cAMP system ofmessage transduction, with ancillary involvement of calciumand inositoltrisphosphate. While the peptide is fairly conservedin vertebrates, the fishes show dramatic biochemical and physiologicaldifferences to the situation in mammals and an incretin functionin fishes is questionable. Fish GLP-1 acts preferentially onthe liver, and recently enterocytes and brain membranes havebeen shown to be potential targets. GLP-1 actions generallyoppose those of insulin and supplant or supplement those ofglucagon by activating glycogenolysis, gluconeogenesis and lipolysisin liver and by accelerating glucose transport and curtailingglucose oxidation in enterocytes. In brain and enterocytes,GLP-1 targets adenylyl cyclase, while in the liver adenylylcyclase and cAMP play subordinate roles only. Although phospholipaseC had been implicated in GLP-1 action, the prevalent route ofmessage transduction in fish liver needs to be elucidated. Theunique functional switch of GLP-1 from a hyperglycemic hormonein fish to a glucostatic incretin in mammals remains a matterof conjecture.     

The Question of a Dermohyal in Brachiopterygian Fishes

Since the turn of this century it has been suggested between whiles that brachiopterygians (i.e. the species of Polypterus and Calamoichthys) are actinopterygians. One of the arguments used recently by advocates of this widespread contention is the dermohyal, an exoskeletal branchial-arch element which they assert occurs in both groups. However, this argument has to be rejected: the dermohyal does not exist in brachiopterygian fishes. The writer proposes to maintain the view that brachiopterygians are not actinopterygians until better arguments to the contrary are forthcoming.     

The Luminescent Systems of Pony Fishes

The anatomy of bioluminescent organs and mode of light production in 18 species of pony fish have been investigated using fresh and preserved material. The luminescent systems are similarly arranged in all. Basically, the system consists of a light organ located at the distal end of the esophagus, and a series of abdominal accessory structures positioned in tandem for controlling light intensity and for directing and dispersing the light. Light is produced by numerous symbiotic luminous bacteria in the light organ. A simple classification of the luminescent systems is proposed. The light organs of Leiognathus elongatus and L. rivulatus show marked sexual dimorphism. The bacteria present in the light organs of many pony fishes are easily culturable, but not those from L. elongatus. Electron micrographs of the light organs of L. elongatus and L. rivulatus show the presence of numerous rod-shaped bacteria measuring approximately 0.8 µ x 2.4 µ and 0.8 µ x 7.3 µ, respectively. It is concluded that the light organ of L. elongatus contains another example of a type of non-culturable luminous bacteria that have been found elsewhere. Such bacteria appear to require from the host some special factor for growth and luminescence.     

The Evolution of Male and Female Parental Care in Fishes

In this paper we propose an explanation for (a) the predominanceof male care in fishes, and (b) the phylogenies and transitionsthat occur among care states. We also provide a general evolutionarymodel for studying the conditions under which parental careevolves. Our conclusions are as follows: (i) Parental care hasonly one benefit, the increased survivorship of young. It may,however, have three costs: a "mating cost," an "adult survivorshipcost," and a "future fertility cost." (ii) On average, malesand females will derive the same benefit from care. They probablyalso pay the same adult survivorship cost. However, their matingcost and future fertility costs may differ, (iii) A mating costusually applies only to males. However, this cost may be reducedby male territoriality and, in some situations, be entirelyremoved. Under this condition, natural selection on presentreproductive success is equivalent for males and females, (iv)When fecundity accelerates with body size in females, whilemale mating success follows a linear relationship with bodysize, future fertility costs of parental care are greater forfemales than males. Although further tests are needed, a preliminaryanalysis suggests this often may be the case in fishes. Thus,the predominance of male parental care in fishes is not explainedby males deriving greater benefits from care, but by males payingsmaller future costs. Males thus accrue a greater net fitnessadvantage from parental care (see expressions [6] and [12]).(v) The evolution of biparental care from uniparental male caremay occur because male care selects for larger egg sizes andincreased embryo investment by females. This increases the benefitto the female of parental care, (vi) By contrast, uniparentalfemale care may originate from biparental care when males areselected to desert. This occurs when female care creates a matingcost to males. In some cases male desertion may "lock" femalesinto uniparental care. However, in many other cases femalesmay be selected to desert, giving rise to "no care." (vii) Theorigin of uniparental female care from no care is rare in externallyfertilizing fishes. This is because the benefits of care rarelyoutweigh a female's future fertility costs (expression [9]).For internally fertilizing species, however, the benefit ofcare is high whereas the cost is probably low. Most of thesespecies have evolved embryo retention, (viii) When parentalcare begins with male care and moves to biparental care, ouranalysis suggests that care evolution will include cyclicaldynamics. Parental care in some fishes may thus be seen as transitionaland changing through evolutionary time rather than as an evolutionarilystable state. In theory, "no care" may be a phylogeneticallyadvanced state.     

The Conservation Status of Hypogean Fishes

Hypogean fishes are susceptible to five main threats: habitat degradation, hydrological manipulations, environmental pollution, overexploitation, and introduced alien species. Because they are endemic to small areas and have small populations, any threat could have serious consequences. For these reasons most populations have been considered threatened or vulnerable. International Union for the Conservation of Nature, and Natural Resources has produced five Red Lists of threatened animals since 1977 and have listed seven, eight, 31, 31 and 63 hypogean fishes, respectively, in some threat category. Before 1994 the categories were qualitative and workers could assess the same species in different ways. In 1994, a new set of quantitative categories were published. The 1996 list was the first to use these categories and three hypogean species were listed critically endangered, two endangered, 46 vulnerable and 12 data deficient. Some of these categories are incorrect or inappropriate and most of the data deficient ones can now be categorised. All 85 known species are categorised here and reasons given for their placements. The current list has three critically endangered, none endangered, 73 vulnerable, four near threatened, one least concern and four data deficient. Some species are relatively well known, others are poorly known. Some are receiving conservation attention, most receive none. A few captive populations have been established, some of which are breeding. Few populations could be restocked if extirpated. Knowing where to direct conservation efforts is a problem since morphological species are proving to be from more than one epigean invasion and therefore represent more than one species. Hypogean fishes merit protection but they may not receive more than cursory protection.     

The Morphology and Evolution of the Ear in Actinopterygian Fishes

SYNOPSIS. In this paper we consider various aspects of the anatomyand ultrastructure of the actinopterygian ear and make a numberof suggestions on the possible adaptive significance of thestructural specializations. The focus of the arguments is basedupon the substantial inter-specific variation in teleost auditorysystems as measured anatomically, behaviorally, and physiologically.It is potentially of considerable significance that the majorpoints of inter-specific variation in the teleost ear are associatedwith the gross morphology and ultrastructure of the otolithicorgan most often implicated in sound detection, the sacculus.Analysis of patterns of sacculus ultrastructure has led to theconclusion that there are, in effect, only about five differentsaccular ultrastructural patterns but that these patterns arebroadly found throughout the teleost fishes. Based upon patternsof inter-specific variation in the sacculus and in other aspectsof the ear and more peripheral auditory structures (e.g., swimbladder),it is argued that adaptations encountered in the teleost auditorysystem cannot be used as reliable taxonomic indicators amongfishes. Rather, it is proposed that the teleost auditory systemis quite maleable in the evolutionary sense, and that interspecificsimilarities in many features of the auditory system reflectconvergent evoluuon, rather than phylogenetic affinities. Theactual selective pressures operating in the evoluuon of thefish auditory system are still essentially unknown. In addition,we cannot be certain that similar ear patterns in differentspecies reflect convergent evolution (or common ancestry), orthat conversely, different ear patterns among species reflectdifferences in auditory function.