Relative growth,morphological sexual maturity,and size of Macrobrachium amazonicum (Heller 1862) (Crustacea,Decapoda, Palaemonidae) in a population with an entirely freshwater life cycle

The objective of this study was to estimate the size of morphological sexual maturity based on the study of relative growth, to determine the maximum size of individuals, and to determine if there are different morphotypes of males in a population of Macrobrachium amazonicum with an entirely freshwater life cycle. Collections were made monthly, with the use of a net, from September 2006 through August 2007. In each individual, the following structures were measured: carapace length (CL, in mm), width of the second pleuron (PlL, mm), length of the carpus (CaL, mm), and length of the propodus (PrL, mm). Relative growth was analyzed by observing the change in growth patterns of certain parts of the body in relation to the independent variable CL. The maximum sizes found were 8.5 and 11.4?mm CL for males and females, respectively. The morphometric variables: length of the carpus (CL?×?CaL) for males, and width of the second pleuron (CL?×?PlL) for females gave the best estimates for the size at maturation, which was 4.26?mm CL for males and 5.39?mm CL for females. The growth pattern in the different stages and the beginning of differential growth seemed to be closely related to reproductive aspects. No indices were found that separated the males into four different morphotypes, as proposed in the literature for coastal or artificially farmed populations. Only the male morphotype termed translucent claw was found in this population. The different morphological patterns in different regions are probably explained by ecological differences in the environments inhabited by these groups, principally in the availability of nutrients and the salinity in which the larvae develop.     

Cloning and characterization of vitellogenin cDNA from the common Japanese conger (Conger myriaster) and vitellogenin gene expression during ovarian development

The major yolk protein precursor, vitellogenin (VTG) was detected in plasma from vitellogenic females and estradiol-17β (E₂)-treated immature females, but not in males and immature females by Western blotting in common Japanese conger Conger myriaster. Its molecular mass was approximately 180 kDa under denaturing and reducing conditions. The common Japanese conger VTG cDNA was cloned from the liver of vitellogenic female. It contains 5110 nucleotides including an open reading frame that encodes 1663 amino acids. The deduced amino acid sequence of the common Japanese conger VTG shares 80% identity with that of eel Anguilla japonica VTG-1, and 45–55%, 32–34% and 27–29% identity with the deduced amino acid sequences of other fish, amphibian and avian VTG with polyserin domain, respectively. In female common Japanese conger, VTG gene was highly expressed in the liver of this species similar with other oviparous vertebrates. The expression levels of VTG gene in the liver increased from the oil droplet stage to the tertiary yolk globule stage and were maintained until the migratory nucleus stage.     

The effect of salinity on respiratory metabolism,survival and moulting in the first zoea of Macrobrachium amazonicum (Heller) (Crustacea,Palaemonidae)

Survival, duration of intermoult cycle and respiratory metabolism were evaluated as a function of salinity (0–35‰; 25° C) in early zoeae of the cinnamon shrimp, Macrobrachium amazonicum. Zoeae are extremely resistant to salinity, mortality occurring only in fresh and sea-water after several days. Moulting occurs in all salinities, longer cycles being recorded in 0 and 35‰ S. The metabolism-salinity curve is broadly U-shaped between 0 and 28‰ S but declines sharply in sea-water. Such physiological responses characterise the early zoeae as strongly euryhaline and typically estuarine. Data are discussed in relation to the degree of adaptation of the organism to the freshwater biotope and the position of the species within the generic pattern of adaptive radiation.     

Effects of All-trans retinoic acid on germ cell development of embryos and larvae of the giant freshwater prawn, Macrobrachium rosenbergii

Embryos of the giant freshwater prawn, Macrobrachium rosenbergii, were treated with 1, 10 or 50 μg ml⁻¹ all-trans retinoic acid (AtRA) for 2 days. Survival and hatching rates were not affected. However, an increase in the number of primordial germ cells (PGCs), progenitors of gametes, and a slightly more advanced stage of the gonads were found in those treated with 10 or 50 μg ml⁻¹ AtRA. Newly hatched larvae were treated with 0.1, 0.5 or 1 μg ml⁻¹ AtRA for 2 days. Survival rates were lower in those treated with 0.5 or 1 μg ml⁻¹ AtRA; nevertheless, the gonads were slightly more developed. The results indicated that AtRA, an active metabolite of vitamin A, affected germ cell and gonad development of embryos and the larvae of giant freshwater prawn.     

Vitellogenesis in both sexes of gonochoristic mud shrimp, Upogebia major (Crustacea): analyses of vitellogenin gene expression and vitellogenin processing

The mud shrimp, Upogebia major is a gonochoristic species with distinct sexual dimorphism; however, the male has the “ovarian part of testis” in the gonad and mature-looking eggs appear in a similar reproductive cycle to the female. Vitellogenesis of U. major was investigated focusing on the characterization of vitellogenin (Vg) gene expression and Vg processing. Vg cDNA cloned by PCR-based methods was 7799 bp-long, encoding 2568 amino acids in a single open reading frame. The deduced amino acid sequence shared common characteristics conserved in other shrimp Vgs. The Vg gene was expressed in the hepatopancreas of females and males, the ovary, and the ovarian part of testis. Vitellins (Vns) were detected in the gonads of both females and males as three prominent polypeptides with apparent molecular masses of 82 kDa, 100 kDa, and 115 kDa. N-terminal amino acid sequences determined for the three polypeptides were present in the deduced amino acid sequence, demonstrating that they derived from a single long Vg polypeptide. Immunoblot analysis using polyclonal antibodies raised against two Vns (82 kDa and 100 kDa) confirmed Vg processing in the hepatopancreas, in the hemolymph and possibly in the oocytes, similarly in both sexes.     

Effect of thermal stress on the neurosecretory cells of the freshwater prawn,macrobrachium kistnensis (Tiwari)

The brain and thoracic ganglion neurosecretory cells of the freshwater prawn, M. kistnensis displayed characteristic changes following 24 hr exposure to warm (31.0° ± 0.5°C) and cold (13.0° ±0.5°C) stress. A and B cells from the brain showed significant elevation in their nuclear diameters after warm and cold stress. Warm stress depressed whereas cold stress enhanced the neurosecretory material intensity of A cells. However, the intensity of B cells neurosecretory material remained unaltered following both treatments. On the contrary nuclear diameters of both A and B neurosecretory cell significantly decreased and an increment in neurosecretory material intensity was revealed in the thoracic ganglion of both warm and cold stressed prawns.     

The ultrastructure of the yolk nucleus during early cleavage of Nassarius reticulatus L. (Gastropoda,Prosobranchia)

Summary In all blastomeres of Nassarius from 4- to 16-cell stage yolk nuclei occur. Most of them are spherical bodies, lying juxtanuclearly between the nucleus and the apical plasmalemma. Strangely they are not ultrastructurally uniform but fall into two categories (Fig. 5): Type I is a massive spherical accumulation of mitochondria embedded in a dense intermitochondrial substance, which appears to contain both granules and filaments. Type II is a ball of radially arranged small Golgi stacks clustered around a centre of Golgi vesicles and other organelles embedded in a ground cytoplasm structurally similar to the intermitochondrial substance of type I. The function of both types of yolk nuclei is unknown. These segmentation yolk nuclei have nothing to do with yolk synthesis any more. On the other hand there are no indications that yolk nuclei occurrence is correlated with the break-down of yolk because neither lipid droplets nor protein yolk granules are observed in or beside the yolk nuclei.We wish to thank Mrs. Chr. Mehlis for her valuable technical assistance as well as Professor J. Bergérard for the excellent working conditions on the Station biologique at Roscoff (France).     

Changes in the ultrastructure of Nematospiroides dubius (Nematoda) intestinal cells during development from fourth stage to adult

Summary The general fine structure of intestinal cells and changes which occur in ultrastructure during development from fourth-stage to adult N. dubius are reported. In fourth-stage worms pigment granules are prominent in intestinal cells. In adults the number of pigment granules appears to be reduced and phagolysosomes containing membranous profiles and pigment material increase in number. Another reorganization of cell structure involves mitochondria which are randomly distributed in the cytoplasm of cells in fourth-stage worms, concentrated in the apical cytoplasm in worms in the molting process, and confined to the base of cells in adult worms. Other changes involved structure of the nucleus, rough endoplasmic reticulum and glycogen content of cells.This investigation was supported, in part, by NIH Fellowships I-FI-GM-32750 and 5-F02-AI-32750.     

Time-course changes in the expression of Na, K-ATPase and the morphometry of mitochondrion-rich cells in gills of euryhaline tilapia (Oreochromis mossambicus) during freshwater acclimation

Changes in expression of Na, K-ATPase (NKA) and morphometry of mitochondrion-rich (MR) cells in gills of tilapia were investigated on a 96-hr time course following transfer from seawater (SW) to fresh water (FW). A transient decline in plasma osmolality and Na+, Cl- concentrations occurred from 3 hrs onward. Gills responded to FW transfer by decreasing NKA activity as early as 3 hrs from transfer. This response was followed by a significant decrease in the NKA isoform alpha1-mRNA abundance, which was detected by real-time PCR at 6 hrs post transfer. Next, a decrease of alpha1-protein amounts were observed from 6 hrs until 24 hrs post transfer. Additionally, during the time course of FW transfer, modifications in number and size of subtypes of gill MR cells were observed although no significant difference was found in densities of all subtypes of MR cells. These modifications were found as early as 3 hrs, evident at 6 hrs (exhibition of 3 subtypes of MR cells), and mostly completed by 24 hrs post transfer. Such rapid responses (in 3 hrs) as concurrent changes in branchial NKA expression and modifications of MR cell subtypes are thought to improve the osmoregulatory capacity of tilapia in acclimation from hypertonic SW to hypotonic FW.     

The ultrastructure of the mid-gut cells of Nasonia vitripennis (Walker) (Hymenoptera,Pteromalidae)

Summary The ultrastructure of the mid-gut cells of female Nasonia vitripennis is described. The mid-gut consists of a uniform, single-cell epithelium. The cells of different gut regions were analysed using morphometric techniques in order to determine any differences in the components. The structure of the cells is described in the unfed animal, and after varying periods of feeding on host body-fluids. Tissues were sampled after 12 h and 24 h of feeding on host body-fluids and after 24 h feeding/24 h starvation. The cells were found to be complex and contain an organelle component that allows solute-transport and extensive lipid synthesis. A limited cytochemical analysis involving the lysosomal marker enzyme-acid phosphatase — and the respiratory enzyme — cytochrome oxidase was carried out.We are indebted to Professor E.W. Knight-Jones, in whose Department this work was carried out, and to the Science Research Council for financial support to one of us (I.D.)     

The morphology of juvenile stages of Crotonia pulcher (Beck, 1962) (Acari: Oribatida: Crotonioidea) with a redescription of the adult

The morphology of juvenile and adult stages of the Neotropical oribatid mite Crotonia pulcher (Beck, 1962) from Ecuador is described and illustrated. This species seems to be a member of the cophinaria group of Crotonia.     

The effect of eyestalk ablation on haemolymph osmotic and ionic concentrations during acute salinity exposure in the freshwater shrimp Macrobrachium olfersii (Wiegmann) (Crustacea,Decapoda)

The location, morphometry, climatic conditions, water balance, hydrology and hydrochemistry of lake Manzala were investigated.Mean annual salinity declined by about 82.7% since 1921, from 16.7 to 2.9% during 1985/86. The nutrient loading increased two or threefold over the past 20 years.These changes are attributed to an increase of the inflow of sewage and agricultural drainage water and restriction of water inflow at the Gamil Lake-Sea Connection since the late 1960's and early 1970's.     

The morphology and ultrastructure of the peripheral olfactory organ in newly metamorphosed coral-dwelling gobies, Paragobiodon xanthosomus Bleeker (Gobiidae, Teleostei)

We examined the peripheral olfactory organ in newly metamorphosed coral-dwelling gobies, Paragobiodon xanthosomus (SL=5.8mm+/-0.8mm, N=15), by the aid of electron microscopy (scanning and transmission) and light microscopy. Two bilateral olfactory placodes were present in each fish. They were oval-shaped and located medio-ventrally, one in each of the olfactory chambers. Each placode had a continuous cover of cilia. The placode epithelium contained three different types of olfactory receptor neurons: ciliated, microvillous and crypt cells. The latter type was rare. Following a pelagic larval phase, P. xanthosomus settle to the reef and form an obligate association with one species of coral, Seriatopora hystrix. Their well-developed olfactory organs likely enable larvae of P. xanthosomus to detect chemical cues that assist in navigating towards and selecting appropriate coral habitat at settlement. Our findings support past studies showing that the peripheral olfactory organ develops early in coral reef fishes.     

Representational Difference Analysis (RDA) reveals differential expression of conserved as well as novel genes during caste-specific development of the honey bee (Apis mellifera L.) ovary

In highly eusocial insects, such as the honey bee, Apis mellifera, the reproductive bias has become embedded in morphological caste differences. These are most expressively denoted in ovary size, with adult queens having large ovaries consisting of 150-200 ovarioles each, while workers typically have only 1-20 ovarioles per ovary. This morphological differentiation is a result of hormonal signals triggered by the diet change in the third larval instar, which eventually generate caste-specific gene expression patterns. To reveal these we produced differential gene expression libraries by Representational Difference Analysis (RDA) for queen and worker ovaries in a developmental stage when cell death is a prominent feature in the ovarioles of workers, whereas all ovarioles are maintained and extend in length in queens. In the queen library, 48% of the gene set represented homologs of known Drosophila genes, whereas in the worker ovary, the largest set (59%) were ESTs evidencing novel genes, not even computationally predicted in the honey bee genome. Differential expression was confirmed by quantitative RT-PCR for a selected gene set, denoting major differences for two queen and two worker library genes. These included two unpredicted genes located in chromosome 11 (Group11.35 and Group11.31, respectively) possibly representing long non-coding RNAs. Being candidates as modulators of ovary development, their expression and functional analysis should be a focal point for future studies.     

The effects of chemical and visual communication, space availability, and substratum color on growth of the juvenile freshwater prawn Macrobrachium rosenbergii (De Man)

The effects of chemical and visual communication, space availability, and substratum color on the growth of juvenile Macrobrachium rosenbergii (De Man) were studied by recording the changes in average weight and length of prawns kept at controlled densities in the laboratory for periods of 6 wk of in communal and individual compartments with constant unidirectional water currents. Chemically mediated growth inhibition increased in proportion to the number of prawns ahead of a given compartment in the water current. Since ammonia and nitrite concentrations were below reported toxic values, progressive accumulation and transmission through water currents of some other chemically mediated growth inhibitor may explain the observed differences in growth rates between compartments. Growth slowed with increasing prawn density (communal areas) and with decreasing individual compartment size (individual areas). Prawns held in contiguous individual compartments, allowing visual communication, exhibited a significantly (P < 0.01) more rapid growth rate than prawns reared in visually isolated compartments. Growth rates for individuals kept on black substrates were significantly greater (P < 0.05) than those of prawns held in aquaria with white or blue substrates. When substrates composed of all three colors in alternating bands were used, prawns showed a significant preference (P < 0.01) for black backgrounds during the afternoon and for the water column during the morning. Possible implications of these findings to the intensive aquaculture of M. rosenbergii are discussed.     

The effect of starvation on the ultrastructure of the digestive cells of Dolops ranarum (Stuhlmann, 1891) (Crustacea: Branchiura)

Transmission electron microscopy was conducted on the digestive epithelium of the crustacean ectoparasite Dolops ranarum to elucidate its ultrastructure for the first time, both in a nourished and starved condition. Specimens were collected from the Limpopo Drainage System in South Africa, and the specimens were killed and dissected in Todd's fixative. The anterior midgut is composed mostly of absorptive cells or R cells, while the diverticula are composed of R cells and of F cells, which are moderately abundant in rough endoplasmic reticulum. They are probably responsible for producing digestive enzymes. The posterior midgut is composed of papilliform B cells with large apically located vesicles and R′ cells devoid of cell inclusions. Under starvation, specimens survive for a maximum of 12 days; R cells show the most conspicuous changes in ultrastructural characteristics. It is concluded that D. ranarum has adapted to short-term survival only without a host.     

Changes in the gene expression of adiponectin and adiponectin receptors (AdipoR1 and AdipoR2) in ovarian follicular cells of dairy cow at different stages of development

Adiponectin is one of the most important, recently discovered adipocytokines that acts at various levels to control male and female fertility through central effects on the hypothalamus-pituitary axis or through peripheral effects on the ovary, uterus, and embryo. We studied simultaneous changes in the gene expression pattern of adiponectin and adiponectin receptors 1 and 2 (AdipoR1 and AdipoR2) in granulosa and theca cells, cumulus-oocyte complex, and in corpus luteum in healthy bovine (Bos tarus) follicles at different stages of development. The expression levels of adiponectin, AdipoR1, and AdipoR2 mRNA were lower (P < 0.05) in granulosa and cumulus cells in comparison with that in theca cells and oocyte. In contrast with the oocyte, AdipoR1 in granulosa, theca, and luteal cells was expressed (P < 0.05) more than AdipoR2. Adiponectin expression increased (P < 0.05) in granulosa cells and in cumulus-oocyte complex during follicular development from small to large follicles. Opposite results were observed in theca cells. Expression of adiponectin was highest in the late stages of corpus luteum (CL) regression, whereas lower expression was recorded in active CL (P < 0.05). AdipoR1 and AdipoR2 expression increased during the terminal follicular growth in granulosa and theca cells (P < 0.05) and during the luteal phase progress in CL. There was positive correlation between adiponectin mRNA level in granulosa cells from large follicles and follicular fluid estradiol concentration (r = 0.48, P < 0.05) and negative correlation between adiponectin mRNA abundance in theca cells and follicular fluid progesterone concentration (r = -0.44, P < 0.05). In conclusion, we found that the physiologic status of the ovary has significant effects on the natural expression patterns of adiponectin and its receptors in follicular and luteal cells of bovine ovary.     

The life history of Labiostrongylus eugenii, a nematode parasite of the Kangaroo Island wallaby (Macropus eugenii): development and hatching of the egg and the freeliving stages

Smales L. R. The life history of Labiostrongylus eugenii, a nematode parasite of the Kangaroo Island Wallaby (Macropus eugenii): development and hatching of the egg and the free living stages. International Journal for Parasitology7: 449–456. Labiostrongylus eugenii (Trichonematidae) occurs in the stomach of the Kangaroo Island Wallaby. Egg morphology is similar to that of other strongyloids. When incubated at 25°C embryogenesis is completed in about 30 h. An incomplete moult occurs within the egg, and larvae hatch at a sheathed second-stage $\text{43}\text{1}\text{2}\text{–83}\text{1}\text{2}$ h later. Development occurred at all temperatures between 2° and 37°C with an optimum about 25°C and an upper limit near 37°C. The hatching process is very rapid, taking about 2 min. It is signalled by increased larval activity followed by a change in shell permeability. The larva hatches at that pole of the shell which has become plastic.The sheathed second-stage larva measures 659.50 ± 22.54 μm by 27.98 ± 1.22 μm. Its internal structures are concealed by a mass of opaque granules which were demonstrated as neutral lipid by oil red O staining. A second incomplete moult at 3–4 days results in a doubly sheathed infective larva from which the lipid gradually disappears. The mouth never appears patent and the larvae neither feed nor grow but rather decrease in size with age. Optimal temperatures for larvae range between 15°–25°C with 37°C about the upper limit. The significance of this developmental pattern is discussed.