Ultrastructure of the epidermis and digestive tract inSebastes embryos,with special reference to the uptake of exogenous nutrients

Synopsis Ultrastructural features of the epidermis and rectum were studied inSebastes schlegeli andS. melanops during the late stages of embryonic development, to confirm uptake of maternal substances. Ruthenium red (RR) and horseradish peroxidase (HRP) were used at fixation and in live embryos, respectively. Epidermal tissue of embryos after developmental stage 24 comprised two squamous cell layers. The outer, thinner cells and their intercellular spaces were easily infiltrated with RR, but the inner cells had no RR deposition. The HRP was not incorporated into the epidermis except in a few outer cells, which had well-developed microvillous projections of cytoplasm. Sacciform cells, chloride cells, and mucous cells distributed in the inner layer but protruding to the epidermal surface had no intracellular RR and HRP depositions. The rectal cells of embryos at about developmental stage 28 had many globular inclusions containing electron-dense substances. The rectal cells were found to take up and digest HRP actively. It is suggested that the embryonic epidermis is structurally loose and takes up low weight molecules, while rectal cells, after the opening of the mouth, actively ingest exogenous, high weight molecules.     

Reproductive cycles ofSebastes taczanowskii,compared with those of other rockfishes of the genusSebastes

Synopsis Seasonal reproductive cycles were examined in both sexes ofSebastes taczanowskii, captured in southern Hokkaido, Japan. The reproductive cycle in females was divided into four periods: recovery (July–August), vitellogenesis (September–March), gestation (April–May) and parturition (June). Spermatozoa were first observed in November in the ovarian cavity, where no structural specialization was present for sperm storage. Fertilization of oocytes appeared to occur in April, when the oocytes underwent a rapid process of final maturation. Embryos developed in the ovary quite synchronously and were released in June; empty ovaries indicated the rockfish has a single parturition. The reproductive cycle in males comprised five periods: resting (December–July), early maturation (February–May), mid-maturation (June–August), late maturation (September–October) and functional maturation (November). In November when active spermatogenesis had been completed, a large amount of spermatozoa was preserved in the sperm duct, and the males were therefore ready for mating. A comparison was made of the reproductive cycles of four species of the genusSebastes inhabiting southern and northern waters of Japan. It suggests that the northern species tend to prolong gametogenesis in both sexes while the southern species have the opposite tendency. Sperm storage in the ovary also tends to be longer in the northern than in the southern species.     

Reproductive styles and life history variables relative to exploitation and management ofSebastes stocks

Synopsis The characteristics of lightly and heavily exploited Pacific ocean perch,Sebastes alutus, stocks are evaluated relative to the predictions of life history theory. These long-lived species (50–100 year lifespan) show limited phenotypic plasticity and have little buffering against the effects of reduced lifespan. Reduced stock abundance has generated some compensatory increase in growth rate. Length at first maturity varies only slightly with increased growth rate, although age at maturity may decrease by 1–4 years. Grooth increases yield larger (15–20%) size at age and increased reproductive effort at younger ages, but lower size-specific fecundity for these faster-growing fish. This suggests an energy allocation protocol favouring growth over reproduction in these long-lived animals. Rockfishes have late recruitment to fisheries (ages 10–15), and the detection time for results of management actions is equally long. Their vulnerability to overfishing means that indices of population changes, more representative of fishing effects than the catch rate index presently used, are required. Reproductive value indices are shown to be extremely sensitive and continuous with population abundance changes. Their incorporation into monitoring programs would permit more timely evaluation of management actions. Management policies developed for shorter-lived species are shown to be inappropriate for rockfishes. The need for an improved match in the time frame of the species' life history, and that of management strategies, is stressed.     

Comparative study on ovarian structures in scorpaenids: possible evolutional process of reproductive mode

The reproductive modes of the Scorpaenidae are extremely varied: oviparity, viviparity, and even spawning of internally fertilized eggs or embryos (zygoparity or embryoparity), as in Helicolenus, are known. The ovarian structure of this family is divided into two types by the arrangement of the stroma and the ovarian cavity. One type is the ovary in which the lamella-like stroma develops from the ovarian hilus located on the dorsal side and where the ovarian cavity is located on the ventral side of ovary, classified as “cystovarian type II-1” by Takano (1989). In the other type, the stroma in the ovary develops radially around the blood circulatory system that traverses the center of the ovary, and then the ovarian cavity surrounds all the ovary, classified as “cystovarian type II-3” by Takano (1989). In the present analysis, previous reports about ovarian structure and the relationship to the reproductive mode of scorpaenids were described, and the ovarian structure of eight genera of Scorpaenidae was examined. The ovary of cystovarian type II-1 is seen only in viviparous genera and is not seen in oviparous genera. However, the cystovarian type II-1 is a general structure in other families of Scorpaeniformes, and this structure could be considered a primitive type of ovary rather than that acquired by the process of evolution from oviparity to viviparity. The ovary of cystovarian type II-3 is seen in all six oviparous genera and the one zygoparous genus examined. The ovary of this type is not found in any other family of teleosts, so it could be a structure originally divided in Scorpaenidae. In the genera having the cystovarian type II-3 ovary, there is a common feature of spawning: a floating egg mass encompassed by the gelatinous material. We postulate that the evolution of reproductive mode in the scorpaenid fishes is as follows: Sebastes and Sebastiscus have a primitive ovary in which viviparity has developed, whereas the genera that spawn a floating egg mass evolved the ovarian structure from primitive type to cystovarian type II-3, and further zygoparity, such as in Helicolenus, evolved from them.     

Reproduction and development ofSebastes in the context of the evolution of piscine viviparity

Synopsis Selected aspects of the reproduction and development ofSebastes and other rockfishes are reviewed in the context of piscine viviparity. Among the eight subfamilies of the Scorpaenidae, viviparity is confined to the subfamily Sebastinae; gestation is lumenal and the embryos usually develop to term within the egg envelope. Transitional states from oviparity to viviparity are evident in different species within the family. A scenario for the evolutionary origin of viviparity in rockfishes is derived from an analysis of scorpaeniform reproductive biology. Although viviparity is best developed in the genusSebastes, it is still in a primitive, unspecialized state. Rockfish viviparity is essentially lecithotrophic, i.e. embryonic nutrition is dependent on the energy reserves laid down during oogenesis. In other groups of viviparous fishes, lecithotrophy has been shown to be better suited energetically to seasonally unpredictable habitats, whereas matrotrophy requires a predictable food supply. During the evolution of an essentially primitive form of lecithotrophic viviparity in rockfishes, the advantages of high fecundity associated with oviparity were retained while an enormous increase in the survival rate of the developing embryos was acquired. The basic lecithotrophic pattern of oviparous development was not changed since it offered selective advantages both in terms of energetics and as a basis for retaining a large brood size.     

Ecology of pelagic larvae and juveniles of the genusSebastes

Synopsis Pelagic larvae and juveniles of the genusSebastes are widely distributed in the continental shelf and slope waters of subarctic to temperate oceans, with greatest abundance in the Northern Hemisphere. We review the ecology and distribution of these planktonic and micronektonic life stages in relation to oceanographic conditions. Special attention is paid to the west coast of North America, where abundance of larvae from samples collected during 1951–1981 is described. After transformation, the pelagic juveniles are widely distributed, often at great distances from benthic adult habitats. These stages are most frequently distributed in either midwater or near-surface habitats; this dichotomy may require different strategies for successful recruitment.     

Energy utilization by embryos during gestation in viviparous copper rockfish,Sebastes caurinus

Synopsis The energy utilized by developing copper rockfishSebastes caurinus embryos was measured through direct respirometry (0.408 cal embryo⁻¹) and compared with the change in energy content of embryos from fertilization to birth (0.361 cal embryo⁻¹). The difference between the energy consumed and energy lost during gestation indicates that 0.047 cal embryo⁻¹ or 11.5% of the energy utilized during gestation is contributed by the mother after fertilization. Available information on other membres of the genusSebastes suggests that matrotrophic viviparity may be the common mode of reproduction, but energy contribution varies greatly between species.     

Scorpionfishes of New Zealand (Pisces: Scorpaenidae)

Abstract

Recent collecting has increased the number of scorpionfish species known from New Zealand, particularly the Kermadec Islands. The following species are now represented in collections at the National Museum of New Zealand: Scorpaena papillosus (Bloch & Schneider); S. cardinalis Richardson; S. cooki Günther; Trachyscorpia capensis (Gilchrist & von Bonde); Phenacoscorpius megalops Fowler; Maxillicosta raoulensis Eschmeyer & Poss; Ectreposebastes niger (Fovrmanoir); Pterois volitans (Linnaeus); P. antennata (Bloch & Schneider); Ocosia apia Poss & Eschmeyer; Plectrogenium nanum Gilbert; and Scorpaenodes guamensis (Quoy & Gaimard). Helicolenus, represented by a complex of species, is not discussed here. All other species are figured and at least briefly described, and a key to their identification is provided.     

Ionic and osmotic environment of developing elasmobranch embryos

Synopsis The elasmobranchs display a variety of ionic and osmotic environments for developing embryos. Oviparous species protect their eggs with a tough, fibrous capsule which is highly permeable to ions and urea even at oviposition. Thus the embryonic tissues are bathed by a solution ionically similar to sea water. In the more advanced reproductive style ofSqualus acanthias (a lecithotrophic live bearer) early embryos in egg capsules are retained in utero and bathed in a solution osmotically similar to maternal plasma. Several months into the 22 month gestation period the embryos can iono- and osmoregulate in a uterine solution resembling sea water. Embryos of more advanced viviparous species develop in a solution that is ionically and osmotically similar to maternal plasma. Iono- and osmoregulation by these embryos would appear to be unnecessary. Clearly, in the oviparous elasmobranchs, the ability of the embryo to regulate salts and urea is present at the earliest stage of development. The need for elasmobranch embryos to regulate osmolytes was reduced or delayed as viviparity evolved.     

Uptake of 14C DDT by wood frog embryos after short term exposure

Wood frog embryos at four different developmental stages and three temperatures were subjected to 0.025 ppm 14C DDT for 24 hr. Embryos within jelly capsules at stages 13, 16 and 18 accumulated about 0.16 ppm at 9, 15 and 21 degrees C. The protective jelly envelopes around embryos in stages 13, 16 and 18 contained about 0.014 ppm at all temperatures. Jelly-free hatching embryos in stage 20 accumulated about 6-10 times the level of earlier stages and showed effects of DDT poisoning. Jelly capsules around amphibian eggs restrict DDT uptake.     

Immunochemical identification and partial characterization of female-specific serum proteins in white-edged rockfish,Sebastes taczanowskii

Synopsis Female-specific serum proteins (FSSPs) in white-edged rockfish,Sebastes taczanowskii, were identified and partially characterized by immunochemical procedures. Two FSSPs, which clearly reacted with antiserum against egg proteins, were confirmed in the serum of mature females, and estrogen treatment induced similar FSSPs in the serum of mature males. Hence, the FSSPs were considered to be vitellogenin. The vitellogenin concentration in female fish was high during the vitellogenic period and low during gestation, parturition and the recovery period, indicating that vitellogenin is used only for yolk formation in the oocytes and not as a direct nutritional source for developing embryos during gestation. On the other hand, an FSSP (FS3), which was considered not to be vitellogenin, was also identified in the sera of mature females and males after estradiol-17β administration by using an antiserum (a-FS3) that removed the components of the male serum and egg extracts from the anti-mature female serum antiserum. Moreover, immunohistochemical observation with a-FS3 illustrated that FS3 was a major constituent of the ovarian fluid but not of vitellogenic oocytes. The cross-reactivities of these FSSPs among seven viviparous rockfishes demonstrated that vitellogenin existed in the sera of all rockfishes studied belonging to the generaSebastes andSebastiscus, whereas FS3 was not present in several species ofSebastes.     

In vivo absorption of 14C-glucose and 14C-glycine by the rat intestine during ochratoxin A toxicosis.

Ochratoxin A was administered orally at a dose level of 6 mg/kg/day for eight weeks to rats. Studies on the intestinal cellular macromolecules, activities of membrane bound enzymes and in vivo absorption of 14C-glucose and 14C-glycine exhibited significant alterations. The observed reduction in the absorption of these nutrients during ochratoxin A toxicosis is corroborated by the changes observed in the levels of cellular macromolecules and the activity of membrane bound enzymes which are involved in the transport system.     

Delayed effects of acute radiation injuries by radioactive carbon (14C-glycine)

A study was made of late biological effects of radioactive carbon (14C-glycine) applied in acute doses. The course of radiation sickness, at its acute stage, is similar to that of acute radiation sickness caused by external gamma-irradiation. The recovery is slow, and the disease becomes chronic exhibiting metabolism disturbances and early death of animals. Radioactive carbon has a pronounced blastomogenic action.     

Uptake of [2-14C]abscisic acid and distribution of 14C in apple embryos

Pyrus malus L. var. Golden delicious embryos were incubated with (±)-[2-¹⁴C]abscisic acid (ABA) (10^-5 M, 355 kBq mol^-1). After incubations of various durations, the radioactivity was measured in whole embryos, cotyledons, and embryonic axes.With either 48-h or 16-d incubation periods, the uptake of [¹⁴C]ABA depended upon the mode of culture used. The lowest values corresponded to the absorption by the embryonic axis, the highest to the absorption by the distal parts of the two cotyledons. The cotyledons accumulated the main part of the radioactivity under all conditions. Dormant and almost completely after-ripened embryos cultivated for 4 d showed no significant differences in the radioactivity uptake for identical modes of culture. There was a linear relationship between exogenous ABA concentrations (0.5 to 3.10^-5 M) and ABA uptake for embryos cultivated for 4 d with the distal parts of the cotyledons immersed in the medium.Abbreviations ABA abscisic acid. RM, RM⁺, C/2 M, and CM are different modes of embryo cultures: embryonic axis immersed alone (RM), together with the proximal parts of the cotyledons (RM⁺); distal parts of the cotyledons immersed alone (CM); embroyo flat on the medium, the root and the external surface of one cotyledon being in contact with the medium (C/2 M) - PP proximal parts of the cotyledons - DP distal parts of the cotyledons     

Uptake and utilization of inorganic carbon by cyanobacteria

In the cyanobacteria, mechanisms exist that allow photosynthetic CO₂ reduction to proceed efficiently even at very low levels of inorganic carbon. These inducible, active transport mechanisms enable the cyanobacteria to accumulate large internal concentrations of inorganic carbon that may be up to 1000-fold higher than the external concentration. As a result, the external concentration of inorganic carbon required to saturate cyanobacterial photosynthesis in vivo is orders of magnitude lower than that required to saturate the principal enzyme (ribulose bisphosphate carboxylase) involved in the fixation reactions. Since CO₂ is the substrate for carbon fixation, the cyanobacteria somehow perform the neat trick of concentrating this small, membrane permeable molecule at the site of CO₂ fixation. In this review, we will describe the biochemical and physiological experiments that have outlined the phenomenon of inorganic carbon accumulation, relate more recent genetic and molecular biological observations that attempt to define the constituents involved in this process, and discuss a speculative theory that suggests a unified view of inorganic carbon utilization by the cyanobacteria.Abbreviations C_i Inorganic carbon - H-cells Cells grown under high CO₂ - L-cells Cells grown under low CO₂ - RuBP Ribulose-1,5-bisphosphate - WT Wild type     

Uptake and utilization of lyso-phosphatidylethanolamine by Saccharomyces cerevisiae

Phosphatidylethanolamine (PtdEtn) is synthesized by multiple pathways located in different subcellular compartments in yeast. Strains defective in the synthesis of PtdEtn via phosphatidylserine (PtdSer) synthase/decarboxylase are auxotrophic for ethanolamine, which must be transported into the cell and converted to phospholipid by the cytidinediphosphate-ethanolamine-dependent Kennedy pathway. We now demonstrate that yeast strains with psd1Delta psd2Delta mutations, devoid of PtdSer decarboxylases, import and acylate exogenous 1-acyl-2-hydroxyl-sn-glycero-3-phosphoethanolamine (lyso-PtdEtn). Lyso-PtdEtn supports growth and replaces the mitochondrial pool of PtdEtn much more efficiently than and independently of PtdEtn derived from the Kennedy pathway. Deletion of both the PtdSer decarboxylase and Kennedy pathways yields a strain that is a stringent lyso-PtdEtn auxotroph. Evidence for the specific uptake of lyso-PtdEtn by yeast comes from analysis of strains harboring deletions of the aminophospholipid translocating P-type ATPases (APLTs). Elimination of the APLTs, Dnf1p and Dnf2p, or their noncatalytic beta-subunit, Lem3p, blocked the import of radiolabeled lyso-PtdEtn and resulted in growth inhibition of lyso-PtdEtn auxotrophs. In cell extracts, lyso-PtdEtn is rapidly converted to PtdEtn by an acyl-CoA-dependent acyltransferase. These results now provide 1) an assay for APLT function based on an auxotrophic phenotype, 2) direct demonstration of APLT action on a physiologically relevant substrate, and 3) a genetic screen aimed at finding additional components that mediate the internalization, trafficking, and acylation of exogenous lyso-phospholipids.     

Uptake and utilization of lipids by Paramecium tetraurelia

Uptake rates of a variety of 14C-labeled fatty acids and complex lipids by Paramecium tetraurelia during 48 h of log-phase growth varied. Fatty acid uptake was maximal during lag phase of growth when phagosome (food vacuole) formation was minimal. Food vacuole formation was shown to be suppressed by the presence of exogenous lipids and by starvation. The rates of uptake of lipids were significantly greater than those of small organic compounds such as amino acids, cyclitols, fatty acid precursors and metabolic intermediates. Significant amounts of radioactivity from 14C-labeled fatty acids were metabolized to 14CO2. The uptake rates of different saturated, straight-chain fatty acids of even carbon numbers were different and were not correlated with chain length, results suggesting that the primary mechanism for uptake of these compounds was neither by bulk transport nor simple diffusion and that carrier-mediated processes could possibly be involved.