Developmental Stages Egg Research Articles

Generalised linear modelling of fecundity at length in southern rock lobsters, Jasus edwardsii

Accurate fecundity estimates are central to population modelling of reproductive status and egg production in a fishery. Southern rock lobster (Jasus edwardsii) fisheries are managed with the consideration of performance measures based on the level of current egg production relative to the unfished stock. Egg production is a function of the size at the onset of maturity, the size structure of the stock, and the fecundity at length of lobsters. Fecundity at length of the Tasmania stock of J. edwardsii has not been reported previously and was estimated from seven sites around Tasmania. Data were analysed by classical linear regression and also generalised linear models (GLM) with gamma and Poisson distributions. GLM with a gamma distribution produced the best fit and did not require a correction factor to generate a model on the linear scale. Individual fecundity ranged from 43,918 to 660,156 and could be predicted from carapace length according to the equation F = −1.707 + 2.969 (log length). The coefficient of length approximated three, implying the fecundity at length relationship is cuboidal. Despite the spatial heterogeneity in reproductive parameters in this fishery, the inclusion of spatial information and egg development stage into the analysis only explained an additional 1% of the variance in fecundity. Thus, it appears valid to apply the relationship across the fishery without spatial separation.

Egg Morphology and Stages of Embryonic Development of the Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae)

AbstractThe structure of the egg and embryonic developmental stages of glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera Cicadellidae), an important vector of Xyhlla fastidiosa are described and illustrated. This sharpshooter has narrow, flattened elliptical eggs with the anterior end less broad and more pointed than the posterior end. The anterior portion of the egg contains a keel-shaped structure with a ridge that stretches backward for a short distance and then transforms into a groove stretching longitudinally along the ventral surface of the egg. The eggshell apparently has two layers: an outer shell layer that peels off easily when handling the egg, and an inner layer that appears intact, tightly surrounding the yolk and other liquid contents of the egg. There were six discernible stages of embryonic development (195 h at 25°C): an initial undifferentiated stage at 0–90 h, appearance of the head cap at 90–100 h, eye spot migration at 100–130 h, active physiological stage at 130–180 h, a head cap ballooning stage at 180–190 h, and emergence of the first-instar nymph at 185–195 h. It was found that the general structure of the egg and embryonic developmental stages are similar to that of other cicadellids. However, the present work breaks down the embryonic development of leafhopper] eggs into more stages than previously described. The timing of H. vitripennis embryonic developmental stages could be used to improve the design of host-age effect experiments aimed at developing more efficient rearing methods for egg parasitoids to be released for control of H. vitripennis.

Spawning season, spawning grounds, and egg production of red sea bream in Hiuchi-nada, Seto Inland Sea

The spawning season and grounds of red sea bream in Hiuchi-nada, the central part of the Seto Inland Sea, were described using a new method based on monoclonal antibodies for identifying Pagrus major eggs, and the daily egg production (standardized by the incubation time and survival rate) was estimated. At the peak of spawning (May), the ranges of sea temperature, salinity, and chlorophyll a where red sea bream eggs occurred were 14.8–17.4°C, 32.0–33.0, 0.5–4.4 μg/L, respectively. The main spawning grounds of the red sea bream were confirmed as being the areas near the Geiyo Islands, Misaki Peninsula, Saijyo, Niihama. The spatial spread of red sea bream eggs increased with the egg developmental stage. The ranges of daily egg production in 2005 and 2006 were 0.3–19.3 and 0.2–6.7 × 109 eggs/day, respectively. In Hiuchi-nada, aquaculture farms are located close to the spawning grounds, and the potential spawning population from the aquaculture farms equaled or exceeded that of the estimated spawning population obtained by the egg production method. Red sea bream eggs in Hiuchi-nada might be produced by both wild and aquaculture-based spawning populations.

Female within‐nest spawning‐site preference in a paternal brooding blenny and its effect on the female mate choice

AbstractFemale spawning‐site preference within a nest and its effect on the female mate choice in a paternal brooding blenny Rhabdoblennius ellipes, were examined in rocky intertidal pools using artificial nests. The number of eggs deposited at the nest entrance site was lower than the number deposited at the center and at deep sites. Moreover, the within‐nest difference in the egg developmental stage indicated that eggs at the nest entrance site were deposited after those at the center and deep sites. These results indicated that females prefer to spawn eggs in the center and deep sites rather than at the entrance site. Owing to the higher egg mortality rate at the entrance site, females may avoid spawning at such sites. An analysis of the nests in the study area suggested that the within‐nest site preference affects female mate choice that is females avoided nests where only the entrance site was available for spawning and instead spawned in nests where the center and deep sites were available.

Characterization of the antioxidant enzyme, thioredoxin peroxidase, from the carcinogenic human liver fluke, Opisthorchis viverrini

The human liver fluke, Opisthorchis viverrini, induces inflammation of the hepatobiliary system. Despite being constantly exposed to inimical oxygen radicals released from inflammatory cells, the parasite survives for many years. The mechanisms by which it avoids oxidative damage are unknown. In this study, thioredoxin peroxidase (TPx), a member of the peroxiredoxin superfamily, was cloned from an O. viverrini cDNA library. O. viverrini TPx cDNA encoded a polypeptide of 212 amino acid residues, of molecular mass 23.57kDa. The putative amino acid sequence shared 60–70% identity with TPXs from other helminths and from mammals, and phylogenetic analysis revealed a close relationship between TPxs from O. viverrini and other trematodes. Recombinant O. viverrini TPx was expressed as soluble protein in Escherichia coli. The recombinant protein dimerized, and its antioxidant activity was deduced by observing protection of nicking of supercoiled plasmid DNA by hydroxyl radicals. Antiserum raised against O. viverrini TPx recognized native proteins from egg, metacercaria and adult developmental stages of the liver fluke and excretory–secretory products released by adult O. viverrini. Immunolocalization studies revealed ubiquitous expression of TPx in O. viverrini organs and tissues. TPx was also detected in bile fluid and bile duct epithelial cells surrounding the flukes 2 weeks after infection of hamsters with O. viverrini. In addition, TPx was observed in the secondary (small) bile ducts where flukes cannot reach due to their large size. These results suggested that O. viverrini TPx plays a significant role in protecting the parasite against damage induced by reactive oxygen species from inflammation.

Reproductive biology of spiny lobster Panulirus regius from the north-western Cape Verde Islands

Green (spiny) lobsters Panulirus regius were obtained by diving at Cape Verde, West Africa, during three sampling periods: May–November 2001, April–December 2002 and April–June 2003. Totals of 429 male lobsters and 423 females (852 in all) were caught. Half the females were ovigerous throughout the sampling periods. Female estimated size-at-50% maturity was 87.9mm carapace length (CL). Brood size and egg developmental stage were examined in 68 ovigerous females. The relationship between brood size (BS, thousands of eggs) and CL (mm) was BS = 1.59CL2.77. Females in the size-class 100–105mm and 115–120mm CL produced half the eggs in the population. Based on these results, an increase in the minimum landing size is proposed. The potential implementation of a maximum landing size is discussed.

Does intersexuality affect precopula and fecundity in Gammarus fossarum (Crustacea, Amphipoda)?

Intersexes of Gammarus fossarum and several other gammarid species seem to be functional females, however, knowledge on reproduction variables, which are of crucial importance for the existence of populations, in intersexes is still scarce. We proposed several hypotheses regarding body length (of singles and in precopula pairs), precopula behaviour (e.g. reduced pairing success) and fecundity (e.g. reduced brood size) of intersexes. Data obtained from G. fossarum populations in the streams Friedrichsbach and Lockwitzbach (Germany) were used to examine these hypotheses. At the Friedrichsbach and one of the two sampling sites of the Lockwitzbach, intersex singles were only in tendency larger than female singles. At the other Lockwitzbach site, intersex singles were significantly larger compared to female singles. Pairing success of intersexes was not reduced. Absolute brood size as well as the brood size normalised to body length did not differ significantly between females and intersexes regarding early stages, late stages or pooled data from all stages of egg development before hatching. For females and intersexes, the number of eggs (stage 1-5) in the marsupium did not significantly decrease during egg development. Hence, intersexes might not be a disadvantage for the population at least with regard to the examined reproduction variables in these populations of this gammarid species.

Utilizing a polymerase chain reaction method for the detection of Toxocara canis and T. cati eggs in soil

A polymerase chain reaction (PCR) technique has been used for the differentiation of T. canis and T. cati eggs isolated from soil and previously identified from microscopical observations. The method, using specific primers for the identification of the two Toxocara species, was assessed in both the field and laboratory. Successful results were obtained when only a single or large numbers of eggs were recovered from 40 g soil samples. The method is sensitive, allows analysis of material independent of the stage of egg development and can be adapted for the recovery of other species of parasites from soil.

Comparative oogenesis in cardinal fishes (Apogonidae, Perciformes), with special focus on the adaptive structures of the egg envelopes

The present study compares gonad structure and oogenesis in 30 species of cardinal fish (Apogonidae) from the Indo-Pacific region. In all of the species studied the ovaries are bilobed, with each lobe possessing ovigerous lamellae whose numbers and dimensions increase concomitantly with growth of the fish and reproductive stage, and correlate with the total dimensions of the particular species. In species of the genus Siphamia, the ovarian lobes are associated with a fat body that is not found in species of the other genera studied. Some of the species studied (Siphamia spp.; Archamia spp.) demonstrate group-synchronized maturation of eggs, possibly with only one spawn per reproduction season. However, most of the Apogon spp., and other genera, have unsynchronized cycles, a characteristic of multiple spawners. The various stages of previtellogenic and vitellogenic development are similar in the different species, but differ in timing and dimensions of the oocytes around which the morphogenesis of the egg envelope (chorion) and follicle begins. Differentiation of the egg envelope and follicle cells parallels the vitellogenic stages of egg development. The number of eggs was found to correlate positively with the length of the body and ovary of the fish, whereas egg diameter was found to correlate negatively with body length. The surface of the egg envelope bears ridges that form patterns of various types, whose structures and dimensions seem to be species-specific, and which in most species converge upon the single micropyle on the animal pole. The exposed ridge mazes include a special fibrous web that anchors in the micropyle. The production and importance of these ridges, as well as the correlations between egg numbers per spawn, egg dimensions, and the oral dimensions of the paternal male, are discussed.

Fecundity of Lake Sturgeon (Acipenser fulvescens, Rafinesque) in Lake Winnebago, Wisconsin, USA

Summary Sturgeon species are known for their relatively high fecundity, with some reported to carry as many as 7.7-million eggs. However, the fecundity of lake sturgeon (Acipenser fulvescesn Rafinesque) has not been thoroughly studied, with limited information available primarily in gray literature and agency reports. Our objectives were to quantify (1) the fecundity and gonadosomatic index (GSI) of female lake sturgeon in a winter F4 stage of development; 2) the average size and weight of F4 lake sturgeon eggs; and 3) relationships between lake sturgeon fecundity and fish weight, length, and age. Total length, weight, age, gonad weight, fecundity, egg diameter, and egg weight were sampled from 14 female lake sturgeon in an F4 stage of egg development in February 2005 from the Lake Winnebago System in Wisconsin. Mean fecundity was 383,529 eggs and the mean GSI was 22.9. Egg diameter averaged 2.74 mm and egg weight averaged 17.34 mg. Weight was the best predictor of fecundity (r 2 = 0.66). Fecundity data for lake sturgeon larger than 35 kg are needed to allow better estimation of fecundity for larger fish.

Use of Luteinizing Hormone Releasing Hormone Analog and Human Chorionic Gonadotropin to Spawn Early‐Egg‐Stage Striped Bass

AbstractFemale striped bass Morone saxatilis with eggs in early stages of development were successfully spawned after being given a priming injection of luteinizing hormone releasing hormone analog followed by a resolving injection of human chorionic gonadotropin (HCG). Over 2 years, 18 of 19 injected fish spawned, producing over 3.5 million viable fry. Egg fertilization rates for all fish that spawned averaged 41%. This procedure, which differs from the traditional spawning method of HCG injection, can increase production by increasing the duration of the production season. In addition, broodfish that once would have been released at capture because they contained early egg developmental stages can now be spawned and used in production.

Egg-thiamine Status and Occurrence of Early Mortality Syndrome (EMS) in Atlantic Salmon from the St. Marys River, Michigan

Early mortality syndrome (EMS) is the term used to describe the mortality of juvenile salmonids due to thiamine deficiency within the Great Lakes basin. EMS appears to be related to the presence of thiaminase found in prey fish such as alewives Alosa pseudoharengus, rainbow smelt Osmerus mordax, and gizzard shad Dorosoma cepedianum. Since 1985, the Michigan Department of Natural Resources, in conjunction with Lake Superior State University's Aquatic Research Laboratory, has raised Atlantic salmon Salmo salar for stocking in the St. Marys River region near Sault Ste. Marie, Michigan. The current study correlates egg-thiamine concentrations from 45 individual family groups with egg and larval mortality as well as length, weight, and condition data obtained from spawning females. Thiamine concentrations were measured at three stages of egg-development using a newly developed rapid reversed-phase solid-phase extraction (RP-SPE) method of thiamine analysis. Results suggest a threshold average total egg-thiamine concentration of approximately 1.0 (nmol/g egg) for normal larval survival. Thiamine analysis indicated no significant change in egg-thiamine concentrations from prefertilization to the eyed stage of development. Female parent weight showed an inverse relationship with egg-thiamine levels. Thiamine immersion of larval sac-fry eliminated the occurrence of EMS for this study population. Due to low cost and ease of use, the RP-SPE method for large scale egg-thiamine analysis has the potential to impact basin wide management decisions with respect to salmonid stocking programs.

Parentage analyses of freshwater goby Rhinogobius sp. OR using microsatellite DNA markers and egg developmental stages of eggs in the nest

Parentage analyses of the paternally caring goby Rhinogobius sp. OR were performed using microsatellite DNA markers and examination of developmental stages of eggs collected from five nests with parental males in the wild. Four of five nests had egg masses with eggs at the same developmental stages from single females. In one nest, the egg mass with eggs at three different developmental stages originated from four females, and eggs of whole developmental stages were observed within the egg mass of each female. This observation suggests that in this goby embryonic stage is an inaccurate indicator of the number of mates.

Differences in egg thermotolerance between tropical and temperate populations of the migratory locust Locusta migratoria (Orthoptera: Acridiidae)

The migratory locust Locusta migratoria L., which is widely distributed throughout the world, exhibits within- and between-population variation in cold tolerance. To understand physiological adaptation in populations, we studied the genetic basis of thermotolerance in Hainan (tropical) and Liaoning (temperate) populations and measured expression of Hsp70 and Hsp90 mRNA in both populations at low (0 °C) and high temperatures (40 °C). Phenotypic variation of thermotolerance is heritable. Heritable characteristics differed among different stages of locust egg development, as well as among different measures of thermotolerance. Nuclear genetic factors, rather than cytoplasmic factors, contribute to differences in cold tolerance between the tropical and temperate populations of the migratory locust; for heat tolerance, maternal effects were involved in three stages of egg development. Expression of Hsp90 mRNA was induced in temperate population after heat shock (40 °C×12 h), whereas expression of Hsp70 and 90 was induced in tropical population after cold shock (0 °C×12 h). We suggest that thermotolerance of locust eggs has a complex genetic basis and heat shock proteins may be involved in differences of thermotolerance between locust populations.

Restricted expression of a median Hox gene in the central nervous system of chaetognaths

Hox genes encode a set of evolutionarily conserved transcription factors that regulate anterior-posterior patterning. Here we report the first developmental expression of a Hox gene from Chaetognatha. These metazoans have been shown recently to be part of the protostome group of bilaterians. We describe the analysis of the SceMed4 gene (a Spadella cephaloptera Median Hox gene) including its expression from late stages of egg development to 7 days after hatching. In all of these stages, SceMed4 is expressed in two lateral stripes in a restricted region of the developing ventral ganglion.

Nonenzymatic preparative-scale synthesis of dityrosine and 3-bromotyrosine

Dityrosine (3,3 -bityrosine) occurs in many biological systems and is formed by the action of peroxidases, reactive oxygen species/free radicals, or ionizing radiation. Dityrosine is found in extensible proteins such as elastin, resilin, and calmodulin and polymeric structures found in insect eggs, yeast spores, and sea urchin egg developmental stages [1]. Dityrosine has shown promise as a marker for identiWcation of cellular aging and damage from protein cross-linking in several pathological conditions such as atherosclerosis [2] and amyloid Wbril formation [3]. Eosinophil peroxidase has been postulated to promote oxidative tissue injury in conditions such as asthma, allergic inXammatory disorders, and helminthic infections [4]. Halogenated tyrosine residues in proteins are speciWc biomarkers of eosinophilmediated tissue injury in vivo. Recent reports in the literature have identiWed 3-bromotyrosine as a speciWc indicator of eosinophil-peroxidase-mediated protein oxidation [5]. To adequately measure dityrosine and 3-bromotyrosine formation in biological samples, an eYcient method for production of suYcient quantities of standard compounds is necessary. Several methods that employ an enzymatic synthesis of dityrosine using

LACK OF EVIDENCE FOR AN ANTISCHISTOSOMAL ACTIVITY OF MYRRH IN EXPERIMENTAL ANIMALS

In a multicenter investigation of the potential antischistosomal activity of myrrh, a resin obtained from an African plant, different derivatives of the resin, including the commercial preparation Mirazid, were tested at different doses in mice and hamsters infected with Schistosoma mansoni. In mice infected with the Egyptian (CD) strain of S. mansoni, four of six groups treated with Mirazid did not show significant worm reduction, while the remaining groups showed significant but trivial reductions. In mice infected with the Puerto Rican (Mill Hill) strain of S. mansoni, a Mirazid solution was toxic for mice at high doses and produced modest or no worm reduction at lower doses. In hamsters and mice infected with Puerto Rican (NMRI) and Brazilian (LE) strains of S. mansoni and treated with the crude extract of myrrh in doses ranging from 180 to 10,000 mg/kg, no signs of antibilharzial activity were observed. Total tissue egg load and egg developmental stages were not affected by any of the treatment regimens. These results were in contrast to those obtained in praziquantel-treated animals in which 94% worm reduction and 100% egg reduction was observed. Based on the findings of this work, we cannot recommend the use of Mirazid in human cases of schistosomiasis.

Buoyancy measurements and vertical distribution of eggs of sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus)

Measurements were made of the density and settling velocity of eggs of sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus), using a density-gradient column. These results were related to observed vertical distributions of eggs obtained from stratified vertical distribution sampling in the Bay of Biscay. Eggs of both species had slightly positive buoyancy in local seawater throughout most of their development until near hatching, when there was a marked increase in density and they became negatively buoyant. The settling velocity of anchovy eggs, which are shaped as prolate ellipsoids, was close to predictions for spherical particles of equivalent volume. An improved model was developed for prediction of the settling velocity of sardine eggs, which are spherical with a relatively large perivitelline volume; this incorporated permeability of the chorion and adjustment of the density of the perivitelline fluid to ambient seawater. Eggs of both species were located mostly in the top 20 m of the water column, in increasing abundance towards the surface. A sub-surface peak of egg abundance was sometimes observed at the pycnocline, particularly where this was pronounced and associated with a low-salinity surface layer. There was a progressive deepening of the depth distributions for successive stages of egg development. Results from this study can be applied for improved plankton sampling of sardine and anchovy eggs and in modelling studies of their vertical distribution.

Why egg-caring males of Isaza (Gymnogobius isaza, Gobiidae) refuse additional females: preliminary field observations

Like many other gobies, males of the Isaza goby, Gymnogobius isaza endemic to Lake Biwa, Japan, conduct parental care of eggs at nests, and females are likely to choose mates while visiting nests. The reproductive strategy should induce polygyny, but Isaza males never accept additional females in one breeding cycle. Sampling data of broods indicated that the egg mass areas were much smaller than the nest sizes, suggesting that nest size is not the limiting factor in obtaining further eggs from additional females. The brood size greatly decreased as the duration of care progressed. Few individuals including caring males ate eggs, and heterospecific egg predators were rarely observed. Sixty percent of egg masses at the middle stages of egg development were infected with aquatic fungi, some being covered with a fungus mat that drastically reduced survivorship. Infected egg masses contained more eggs than non-infected ones at the same stage, indicating that large egg masses are prone to be frequently destroyed by fungi. It is likely that the activity of parental males is lowered during the long care periods at low water temperature in early spring. Such lowered activity of caring males might be responsible for infections in large broods that would have needed more care. We propose the hypothesis that male rejection of additional females may be related to optimal brood size, which will be less susceptible to fungus infection and produce more hatching young than otherwise. This hypothesis will explain not only male avoidance of additional females but also some unique reproductive behaviors of this fish such as some females’ spawning of a portion of of the mature eggs in one nest.

Pallisentis rexus from the Chiang Mai Basin, Thailand: ultrastructural studies on egg envelope development and the mechanism of egg expansion.

Pallisentis rexus Wongkham & Whitfield, 1999 (Eoacanthocephala: Quadrigyridae) infects the freshwater snakehead fish, Channa striata, in the Chiang Mai Basin, Thailand. All stages of egg development within the body cavity of the female parasite were observed, using transmission electron microscopy. Changes in mature eggs after contact with water were also investigated. The mature egg has five egg envelopes separated from each other by four gaps. The fertilization membrane, which is formed first, is pushed centrifugally by other, subsequently formed, envelopes and gaps, which produces a final total shell thickness of 8-36 microm around the acanthor. The disappearance of the outermost layer and the unpleating of an adjacent inner layer causes the expansion of eggs on contact with water. The volume of an expanded egg is approximately 27 times that of an unexpanded one, but the density of eggs is reduced from a value greater than water to one almost equal to water. This is believed to aid the dispersion of eggs.