摘要:

This study was conducted to examine the nutritional value of eight algal diets for two species of abalone,Haliotis tuberculataandHaliotis discus hannai, by measuring biochemical composition of the algae and relating this to feeding rate, growth and biochemical composition of the animals. Nutritional value of algal diets can be divided into three categories for each species of abalone. ForH. tuberculatathe best performance was on the mixed diet andPalmaria palmataintermediate wasAlaria esculenta, Ulva lactucaandLaminaria digitata, and lowest growth was onLaminaria saccharinaandChondrus crispus.ForH. discus hannai, best performance was onA. esculenta, P. palmataand the mixed diet; intermediate was onL. saccharinaandL. digitataand lowest was onU. lactuca.It is generally accepted that high “balanced” levels of protein (>15%), lipid (3–5%) and carbohydrate (20–30%), with no detrimental substances in natural algae are essential for optimal growth performance of these abalone. The fact thatA. esculenta, L. saccharinaandU. lactucahad different dietary values for the two abalone species indicates specific nutritive requirements and/or digestive physiology. Overall,H. tuberculatagrew faster, had higher food conversion efficiencies and muscle yield thanH. discus hannai.Generally abalone fed on the highest category diets, had higher muscle yields and levels of protein, visceral lipids and muscle carbohydrate. Viscera and foot muscle are reservoirs for lipid and carbohydrate, respectively. The effect of algal diet on sexual maturation is similar to that on somatic growth.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672298

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The distribution of serotonin-like immunoreactivity was studied in the central nervous system and the gonad ofPecten maximus.Cerebral and pedal ganglia contain a well developed serotonin-immunoreactive neuronal subpopulation, whereas positive neurons are scarce in the visceral ganglion. The distribution pattern of immunoreactive elements in the gonad indicate that serotonin is involved in peripheral neurotransmission of this organ. Seasonal variations of monoamines (serotonin, dopamine and noradrenaline) have been investigated in the nervous system using HPLC. Lower concentrations of serotonin are observed during winter in the central nervous system; dopamine levels of the visceral ganglion are correlated to gonadal growth.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672299

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The ultrastructure of the uterus in gravid proglottids ofHymenolepis citelli, Vampirolepis nanaandVampirolepis microstomawas examined using transmission and scanning electron microscopy. The cellular and subcellular structures were similar in all three species, consisting basically of a syncytial layer attached to a basal extracellular matrix. All nuclei were juxtaluminal and each contained a single large centrally located nucleolus and prominent masses of central and peripheral heterochromatin. The cytoplasm showed evidence suggesting a high level of protein synthesis and secretion. It consisted primarily of granular endoplasmic reticulum with moderately dilated cisternae; most cisternae were completely filled with an electron-lucent flocculent material, but others contained electrondense granules. Free ribosomes and mitochondria were also present. The apical plasma membrane and a small amount of enclosed cytoplasm were folded into long microlamellae that extended into the uterine lumen. Larger epithelial folds and villi consisting of folded portions of the entire epithelium projected into the uterine lumen. The uterine epithelium along with its basul extracellular matrix and underlying cellular parenchyma were folded into the lumen at several points, forming epitheliomesenchymal folds and villi that closely apposed many of the eggs.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672300

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Reproductive strategy was studied in two euphausiid species.Euphausia superbaoccurs in large aggregations south of the Antarctic Convergence, living in extreme climatic conditions. In the Mediterranean Sea, populations ofMeganyctiphanes norvegicaexperience moderate seasonal variations and a stable temperature regime (13°C). Both species release their eggs in the water column and have similar basic patterns of development. The early seasonal development of the gonads ofE. superba(especially ovarian previtellogenesis) is associated with the ice-edge in spring. Egg production is strictly limited to the summer (December, January and February), but multiple spawns are then produced by individual females through a succession of short vitellogenic cycles. Both males and females undergo a sexual regression in winter when only basic activity of the gonads (gametogenesis) is maintained. Ovarian development ofM. norvegicastarts in January (previtellogenesis) in the Ligurian Sea before the spring bloom. Eggs are produced from February to May by successive vitellogenic cycles. Gonadal activity is reduced during summer and autumn. This timing is different from the northern populations of the species that rather spawn in spring and summer. In both species the seasonal variability in food availability is tempered by storage of carbohydrates and lipids in the fat body for subsequent yolk accumulation in the eggs. These two krill species appear to have adapted their reproductive cycle to different habitats by using the flexibility of the physiological cycles involved in gonad development, a strategy that allows them to enhance fecundity and to tune the reproductive effort with food availability for the offspring.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672301

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The testis ofNassarius kraussianus(Nassariinae) produces two types of spermatozoa, a motile euspermatozoon and a non-motile paraspermatozoon. The euspermatozoon is filiform and about 95/μm long. The elongated head (40 μm long) is comprised of a slender nucleus (about 0.5 μm diameter) which is penetrated throughout by an intranuclear canal housing the anterior portion of the axoneme. A short (about 2 μm long) conical acrosome surmounts the nucleus anteriorly. The mid-piece (23 μm in length) consists of six to seven modified mitochondria which are helically arranged around the axoneme. Posterior to the mid-piece the tail is composed of a short glycogen piece and an end piece. The paraspermatozoon is spindle-shaped (about 50 μm long) and contains multiple (16–20) axonemes the basal bodies of which fuse anteriorly. Posteriorly, numerous small mitochondria and electron-dense bodies lie between the axonemes. Structural changes during eu- and paraspermiogenesis mirror those described for other species of gastropod mollusc with dimorphic spermatozoa. However unlike other molluscs, the cytoplasmic bridges which connect developing spermatids contain well developed stacks of endoplasmic reticulum which form a continuum with that in the cytoplasm of the spermatids. These structures may in some way facilitate the synchronous development of the spermatozoa.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672302

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The diversity of storage tissue cell types in bivalve molluscs is evident. In some species there are no specific storage cells, and the adductor muscle plays the role of a reserve tissue (Pectinidae). In others both muscular cells and specific storage cells are involved in storage and release of nutrients for gametogenesis (Veneridae). A few species have a specific storage tissue such as the mantle inMytiluscontaining two complementary types of cells. This specialisation can be correlated with the fertility of the species and with the variation of available food organisms. Vesicular connective tissue is found in species with a high level of fecundity which are subject to marked fluctuations in food availability (Mytilidae, Ostreidae). This can be considered as an adaptive behaviour to profit from uncertain supply of food supplies in order to produce the maximum number (and quality) of gametes in a precise period of the year.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672303

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Oogenesis in nereids is reviewed as a problem of regulatory physiology, and the current knowledge on the metabolic links between somatic tissues and growing oocytes is reported. One type of free-floating coelomocyte, the eleocyte, stores lipid and glycogen, is highly active in histolysis related to sexual maturation and secretes vitellogenin and metabolites in a sex-specific manner. Eleocytes are therefore considered principal distributors of metabolites during sexual maturation. A strategy is described for determining the flow of metabolites between eleocytes and oocytes both of which can be studied separately in cell culture. The metabolic links are regarded as being capable of, and sufficient for, regulating oocyte growth.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672304

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A wide range of cryoprotectants and cooling rates have been tested on the spermatozoa of two polychaete speciesArenicola marinaandNereis virens.The techniques were more successful withN. virens;with this species active sperm were recovered after immersion in liquid nitrogen following a variety of cooling protocols. Structural damage to the sperm of both species, however, was observed following freezing, and this was more severe in the case ofA. marina.Structural damage of the flagellum plasma membrane was most commonly observed. Biologically important changes in the sperm can be induced by the freezing procedures; for example acrosome eversion may be induced inN. virenssperm. Dissociation of the sperm ofA. marinacan be induced after freezing by the sperm activator quinacrine, but these sperm do not acquire forward motility probably due to flagellum damage.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672305

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Porcellio ficulneusVerhoeff inhabits xeric Mediterranean grassland habitats. During winter vitellogenesis takes place and mancas are released in April. Under natural conditions some oocytes (about 20%) were lost. Both high temperature (25°C) at long or short photophases affected the reproductive pattern. Thus at 25°C and constant light vitellogenesis was markedly shorter than under field conditions. Oocytes matured sooner, but many were resorbed. The marsupium was formed earlier and contained fewer eggs. In some cases mancas that had developed could not emerge from the marsupium and died inside. In conclusion,P. ficulneusresponds to warmer conditions by breeding earlier and reducing the number of offspring.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672306

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Adverse effects of extracts from the plantsArtocarpus altilisandAzadirachta indicaon egg laying and hatching in the tickBoophilus micropluswere quantified. A 50% inhibition of egg laying was achieved by a dose of 0.54 and 0.46 μg crude ethanol extract per tick, respectively. These doses also caused a 65% and 80% hatching failure, respectively. Extracts, particularly those ofA. indica, inhibit protein and lipid sequestration by ovaries and oocytes. GC-MS analyses revealed reductions in the quantities of four methyl esters sequestered from the ovaries into the oocytes oviposited on the 12th day of engorgement by the treated ticks in the order of (A. indicaeffects are in parentheses): undecanoic acid 10-methyl-,methyl ester 40% (100%); tetradecanoic acid, methyl ester 100% (100%); tetradecanoic acid, 12-methyl-,methyl ester 100% (100%) and pentadecanoic acid, 14-methyl-,methyl ester 30% (75%).

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672307

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor