Orchestia Gammarellus Research Articles

Vitellogenesis and Its Control in Malacostracan Crustacea

Vitellogenesis in the amphipod Orchestia gammarella, in natantian decapods and probably in other Malacostraca involves two phases, primary and secondary vitellogenesis. Oogenesis from oogonia to the end of primary vitellogenesis is a continuous process. The primary proteic vitellus is endogenous. The secondary vitellogenesis takes place during the reproductive season. Fully grown primary follicles are surrounded by a permanent follicular tissue (secondary folliculogenesis). The resulting secondary follicles grow synchronously until ovulation. A tubular network has been observed in secondary follicle cells of prawns. The prominent feature of secondary vitellogenesis is the uptake of vitellogenin by the oocytes. This vitellogenin is synthesized by the fat body. Secondary vitellogenesis is controlled by neurohormones that have not yet been isolated and whose modalities of action still remain unclear. In Decapoda, the classical gonad-inhibiting hormone or GIH released by the sinus glands inhibits secondary vitellogenesis and the synthesis of vitellogenin. In Isopoda, vitellogenesis-inhibiting hormone is synthesized by neurosecretory cells in the median part of the protocerebrum. In Amphipoda, neurosecretory cells of this region secrete a neurohormone inducing secondary folliculogenesis and triggering secondary vitellogenesis. The neurohormones would control the formation of functional secondary follicles during the reproductive season. Other hormones are involved in control of secondary vitellogenesis. In Peracarida molting hormone is necessary for a normal synthesis of vitellogenin and the uptake of this protein by growing oocytes. In the amphipod Orchestia gammarella secondary folliculogenesis requires a low titer of ecdysteroids which characterizes postecdysis. The correlation between molt cycle and secondary vitellogenesis would be established in this way. After secondary folliculogenesis, the secondary follicle cells become endocrine and secrete the vitellogenin-stimulating ovarian hormone (VSOH).

Incorporation de la vitellogénine tritiée dans les ovocytes du Crustacé AmphipodeOrchestia gammarellus(Pallas) / Incorporation of tritiated vitellogenin into the oocytes of the crustacean amphipodOrchestia gammarellus(Pallus)

Summary During the secondary vitellogenesis the oocytes of Orchestia gammarellus accumulate yolk spheres and lipid droplets. We studied the uptake of tritiated vitellogenin by the oocyte and its accumulation in the yolk spheres.

Gill area relationships in an ecological series of gammaridean amphipods (Crustacea)

From scale drawings of over 1200 gills, total gill area has been determined by computer for the following ecological series of amphipods: Gammarus locusta (L.) (aquatic, marine), G.pulex (L.) (aquatic, freshwater), G. duebeni Liljeborg (high shore, brackish water), Echinogammarus pirloti (Sexton & Spooner) (high shore, fluctuating salinity), and Orchestia gammarellus (Pallas) (semi-terrestrial). Gill area/body dry weight relationships are established for each species and are shown to differ significantly from one another. For a given body weight Gammarus pulex possesses the largest gill area, followed by G. locusta then G. duebeni, Echinogammarus pirloti and Orchestia gammarellus. The anterior gills (G2-5) are equivalent in area (≈20% per pair) in the gammarids with G6 and 7 declining in area. In Orchestia, G2 and G6 each make up ≈25% of the total gill area. Gills 3, 4, and 5 are relatively small and G7 is missing altogether. A reduction in gill area, to reduce desiccation, is thus related to the acquisition of terrestrial habits; an increase in gill area may, however, be promoted in reduced salinities as a means of facilitating ion uptake.

Electron microscopic observations of the subepidermal fat-body changes following ovariectomy inOrchestia gammarellus(Pallas) (Crustacea: Amphipoda)

It has been proved previously that newly synthesized vitellogenin is no longer detectable in the haemolymph of Orchestia gammarellus females (Crustacea: Amphipoda) 5 to 8 days after bilateral ovariectomy. The present paper deals with the ultrastructural changes observed in the subepidermal fat body—site of vitellogenin synthesis—of these females. Briefly, the adipocytes acquire the features of non-protein synthesizing cells. It is concluded from these data that the ovaries act on vitellogenin synthesis and not—or not only—on vitellogenin release.

Subcellular localization of vitellogenin in crustacean adipocytes by the unlabelled antibody enzyme method

The subepidermal fat body of the Amphipod Crustacean Orchestia gammarellus shows ultrastructural modifications related to vitellogenin synthesis. In the adipocytes of vitellogenic females, the rough endoplasmic reticulum is well developed whereas in those of males and non-vitellogenic females it is almost entirely absent; lipids and glycogen are, on the contrary, less abundant. The unlabelled antibody enzyme method shows the presence of vitellogenin in the dense bodies of the adipocytes of vitellogenic females. Adipocytes of males and non-vitellogenic females are not immunoreactive.

Étude de la synthèse de la vitellogénine chez les mâles intersexués d'Orchestia gammarellus (Pallas) (crustacé amphipode). Effets de la greffe d'un ovaire

In intersex males of Orchestia gammarellus (Crustacea, Amphipoda), vitellogenin is sometimes present in the haemolymph, but almost always in small amounts. However, no significant synthesis of vitellogenin can be shown in our experimental conditions. After the grafting of an ovary, vitellogenin becomes abundant, and a high level of synthesis, though subnormal, is observed in nearly half the cases. At the same time, secondary vitellogenesis occurs in the graft. The androgenic gland of the intersex male cannot prevent the ovary from functioning normally.

Quelques aspects des interactions hormonales entre la mue et la vitellogenèse chez le Crustacé Amphipode Orchestia gammarellus (Pallas)

The mechanisms which coordinate and regulate secondary vitellogenesis and molting in Orchestia gammarellus have been studied in natural and experimental conditions. The onset of secondary vitellogenesis, requiring a protocerebral factor and a low titer of ecdysteroids, occurs only after normal folliculogenesis. The secondary follicular tissue would secrete vitellogenin stimulating ovarian hormone (VSOH) which stimulates the subepidermal adipose tissue to produce vitellogenin. VSOH and ecdysteroids are indispensable to normal vitellogenin synthesis during secondary vitellogenesis. Moreover, the Y-organ controls vitellogenin entry into the oocytes. In secondary vitellogenesis the ovary would stimulate the secretion of molt inhibiting hormone (MIH) which would act on the epidermis, rendering this tissue unresponsive to the stimulatory action of ecdysterone. The Y-organ and the protocerebrum are involved in the control of the molting processes independently of their action on vitellogenesis.

THE EFFECTS OF TEMPERATURE ON SEXUAL DIFFERENTIATION IN THE TEMPERATURE SENSITIVE THELYGENIC—INTERSEXUAL OFFSPRING OFORCHESTIA GAMMARELLUS(PALLAS) (AMPHIDOPA; CRUSTACEA

An increase in temperature to 25 or 30°C during embryonic development and the first stages of post-embryonic development in the temperature-sensitive thelygenic offspring of Orchestia gammarellus, brings about a higher male ratio in the broods, that is to say weakens or cancels the action of the feminising factor. The effect appears much earlier at 30 than at 25°C. At 30°C, the results achieved partly depend on the stage of embryonic development during which the heat treatment is applied. The more sensitive stages correspond to gastrulation and the formation of germ layers. The sensitivity to the increased temperature depends on the sexual genotype of the individuals: the 2AYY are more sensitive than the XY animals.

THE EFFECTS OF TEMPERATURE ON SEXUAL DIFFERENTIATION IN THE TEMPERATURE SENSITIVE THELYGENIC—INTERSEXUAL OFFSPRING OFORCHESTIA GAMMARELLUS(PALLAS) (AMPHIPODA; CRUSTACEA)

Some females of Orchestia gammarellus generate offspring which include too many females as well as intersexual males. This thelygeny related to intersexuality is temperature sensitive; it disappears above 22°C. It is induced by a feminising parasite described in another work. We have studied how the temperature acts on pubescent thelygenic females having either a known or unknown genotype (♀ 2AYY). The increase of female breeding temperature up to 25 or 30°C has two kinds of consequences for their offspring: (i) an increase in the male ratio, that is to say the expression of the normal genetic sex in potential neo females, and (ii) a correlative decrease in the proportion of intersexual males. The strength of these effects varies according to several parameters: temperature, exposure duration and genotype of tested females.

Quelques aspects du contrôle hormonal de la synthèse de la vitellogénine chez le crustacé amphipode Orchestia gammarella (Pallas)

The presence of a vitellogenin stimulating ovarian hormone (VSOH) in Orchestia gammarella has been demonstrated by gonadectomy and ovary grafting. Vitellogenin synthesis is not affected by molting hormone injection; it decreases after Y-organ (molting gland) cauterization. Studies in progress seem to indicate that the destruction of the median area of the protocerebrum is followed by a decrease of this synthesis.

Ultrastructural observation of oogenesis in the crustacea amphipoda Orchestia gammarellus (Pallas)

The oogenesis of the Crustacea Amphipoda Orchestia gammarellus can be divided in five stages taking into consideration both the oocyte ultrastructure and the physiology of the ovary. The primary oogonium (12 μm in diameter) is lodged within the germinative zone: after division, the daughter cell (or secondary oogonium) leaves this area and enters meiotic prophase. Stage I is represented by the oocyte with visible chromosomes (12–18 μm in diameter) the cytoplasmic ultrastructure of which is comparable to that of the oogonium. Stage II or previtellogenesis is characterized by a considerable growth of the oocyte (18–80 μm in diameter) which becomes enriched in ribosomes and vesicles of the rough endoplasmic reticulum; the oocyte does not yet contain any vitelline reserve (proteinaceous and lipid). Stage III or primary vitello-genesis (80–160 μm in diameter) is typified by the synthetic activity of the rough endoplasmic reticulum, corresponding to an endogenous accumulation of proteinaceous yolk. Stage IV or secondary vitellogenesis (160–800 μm in diameter) only appears during the period of reproduction; by means of endocytosis the oocyte accumulates yolk spheres in addition to lipid droplets, the origin of which is uncertain; towards the end of vitellogenesis, cortical granules become a feature that is noted for the first time in Crustacea. The last stage or maturation (800 μm in diameter) starts right before or immediately after the exuviation of the female and ends with fertilization.

Female-specific proteins (vitellogenin and lipovitellins) in Orchestia gammarella (crustacea, amphipoda): Isolation and identification by means of glutaraldehyde-polymerized antibodies

1. 1. DEAE cellulose chromatography of whole egg-maturing female extract followed by Sephadex G200 gel filtration and adsorption on polymerized specific antibodies yields a protein fraction which, besides vitellogenin (VTG) and different lipovitellins (LPV I, I′, II, and probably II′), contains two other proteins unique to females. 2. 2. Whether the latter are related to the VTG-LPV system, and hence involved in the process of vitellogenesis, or whether they are completely different proteins, remains to be determined.

Mue et vitellogenèse chez le crustacé amphipode Orchestia gammarella Pallas : II. Etude de la synthèse de la vitellogénine (“fraction protéique femelle” de l'hémolymphe) après destruction des organes Y

Cauterization of Y-organs in Orchestia gammarella is followed by a depression of vitellogenin synthesis. Correlatively, vitellogenesis is either absent when the operation is performed at the beginning of the intermolt or stopped when the operation is performed later.

Evidence for control of vitellogenin synthesis by an ovarian hormone in Orchestia gammarella (Pallas), crustacea; Amphipoda

Females of the amphipod crustacean Orchestia gammarella were bilaterally ovariectomized. Synthesis of vitellogenin completely ceased 5 to 8 days after the operation and was restored by an ovarian transplant. Based on these results, the existence of an ovarian hormone is postulated which controls vitellogenin synthesis. We propose to call this hormone “vitellogenin stimulating ovarian hormone” (VSOH).

Experimentation hyperbare (110 atmospheres) chez un crustace amphipode talitridae

Males and females of the Amphipod crustacean Orchestia gammarella (Talitridae) in period of sexual activity were isolated and compressed in an experimental hyperbaric chamber at pressures between 20 and 110 ATA with oxygen-helium (heliox) mixture (PIo2 = 300 torr). Stay duration under pressure was 16 days. This stay under pressure did not induce any important disorder like a high pressure nervous syndrome except excitement during compression between 70 and 110 ATA; phenomena of shedding of skin and reproduction did not change; rate of masculinity of the lineage was not modified. Slow decompression did not bring out bends. 110 ATA pressure with heliox mixture does not appear to induce obvious deterioration neither in cellular metabolism nor in physiological functions for instance, the intricate functions of reproduction.

The proximate and fatty acid composition of some estuarine crustaceans

The lipid content of Crangon crangon, Gammarus salinus, Neomysis integer, Praunus flexuosus and Orchestia gammarella collected from the reservoir of the Oldbury power station on the Severn Estuary ranged from 25 to 33% of the dry weight over the course of one year while the corresponding values for ash averaged 15–24%. Water accounted for 75–80% of the wet weight except in the case of O. gammarella (70%). The unusually high lipid values were probably connected with the highly favourable environmental conditions in the reservoir while both the size and reproductive condition of the animals were also important in determining the size of the lipid store. Phospholipids accounted for as much as 33% of the total lipid in C. crangon and for as little as 24% in N. integer and P. flexuosus. The predominant fatty acids in both the neutral and phospholipids of all species were 16:0, 18:1, 20:5 and 22:6.

Molting and vitellogenesis in Orchestia gammarella Pallas (crustacea amphipoda): study of the female-specific protein synthesis after ecdysterone administration (author's transl)

Ecdysterone, administered to Orchestia gammarella females (200 mug/g), has no positive effect on the female-specific protein synthesis and vitellogenesis.

The Female-specific Protein (Vitellogenic Protein) in Crustacea with Particular Reference toOrchestic gammarella(Amphipoda)

Comparative electrophoretic studies of male and female hemolymph in Crustacea have led to the discovery of a lipoglycoprotein fraction present in females and absent from males. The female-specific protein fraction also contains a pigment which has been identified in a small number of species and appears to be a carotenoid. Further observations indicated that the presence of this fraction is coincident with the presence of maturing ovocytes in the ovary. The major protein component of the vitellus is also a lipoglycocarotenoprotein complex. Comparative analyses have shown that the female-specific protein fraction present in hemolymph and the major protein component of the vitellus are electrophoretically and immunochemically identical. Moreover, in the Amphipod Orchestia gammarella both components appear to have the same molecular weight, estimated as approximately 3 × 105 by Sephadex G 200 gel filtration. Although there is ample evidence to support the idea that the female-specific protein is synthesized externally to the ovary, the site of synthesis still remains unknown. Experimentally induced sex reversal in O. gammarella indicates that the synthesis of the female specific protein is under ovarian control.

A bilateral gynandromorph of Nephrops norvegicus (Decapoda: Nephropidae)

A bilateral gynandromorph specimen of Nephrops norvegicus (L.) from the Irish Sea is described. Previous records of gynandromorphs within the Nephropidae are discussed, together with other types of sexual abnormality found in N. norvegicus. It is suggested that the bilateral asymmetry is due to a chromosomal aberration in the first embryonic cleavage division, and that further division is determinate. In addition, it appears that the androgenic gland in N. norvegicus, Homarus gammarus and H. americanus does not have the same mode of action as that reported for Orchestia gammarella and O. cavimana.

Biological Science: Adaptive Significance of a Biased Sex Ratio in Orchestia

IN ecological studies of the marine supralittoral genus Orchestia (Crustacea, Amphipoda) many populations have been found that have biased sex ratios (ref. 1 and unpublished results of D. J. W.). Thelygeny has also been found in some of the terrestrial species of Orchestia2, and in the sublittoral, species, Orchestia gammarella (Pallas), both amphogenous and thelygenous populations have been found3. I have investigated the possibility that biased sex ratio populations have an adaptive advantage in altering reproductive potential and the phylogenetic mechanism controlling its origin.