Reproductive biology of the antarctic opisthobranch Philine gibba Strebel

Monthly samples (August 1974 to February 1976) and cultured material have been used to describe ovotestis maturation, spawning, and larval development of the Antarctic opisthobranch Philine gibba Strebel. Ovotestis maturation took one year and mature individuals (mean shell length 12 ± 1.4 mm) spawned a single egg mass in April–May containing 975–4760 eggs, 379 μm in diameter.Development was non-pelagic but an active veliger was observed within the egg capsule. Juveniles (mean shell length 375 ± 55 μm), which hatched from August to October, resembled adults except for the presence of eye spots and an exposed shell. The mantle enclosed the shell by February when shell length was 890 ± 30 μm.     

Nautilid nurseries: hatchlings and juveniles of Eutrephoceras dekayi from the lower Maastrichtian (Upper Cretaceous) Pierre Shale of east‐central Montana

The nautilid Eutrephoceras dekayi (Morton 1834) is relatively abundant in the lower Maastrichtian (Upper Cretaceous) Pierre Shale of east‐central Montana. We analysed the morphology, size frequency distribution, and isotope composition of a large collection of 220 well‐preserved specimens including hatchlings, juveniles and adults. The newly hatched shell is approximately 14 mm in diameter with a body chamber one‐third whorl in angular length terminating in the nepionic constriction. Internally, the embryonic shell contains five septa. Juveniles are abundant and comprise two‐thirds of the sample whereas sub‐adults, defined by the incipient flattening of the venter, are rare. Adults comprise approximately one‐third of the sample and average 100 mm in diameter. The co‐occurrence of newly hatched shells, small juveniles and adults suggests that the eggs were laid in the same area in which the hatchlings developed. Based on the excellent preservation of the juveniles, we conclude that they did not float into the area after death, but lived in the region, implying that this area served as a nursery for young animals. The calculated temperatures of the embryonic shells are similar to those of the post‐embryonic shells and generally range from 16 to 18 °C. Upon hatching, the nautilids probably followed a demersal mode of life and lived in well‐oxygenated water ≤50 m deep. An examination of lethal injuries (puncture holes) suggests that all ontogenetic stages were equally vulnerable to predation. The proximity of the site to the Sheridan Delta suggests that the specimens were smothered by sudden pulses of sediment transported into the area by major storms.     

The embryonic phase and its implication in the hatchling size and condition of Atlantic bobtail squid <Emphasis Type="Italic">Sepiola atlantica</Emphasis>

Early life stages of cephalopods are somewhat complex due to the life history strategy or species specificity of generalized ontogenetic patterns and processes. This work aimed to determine the time length of embryonic development at different temperatures, and if the egg size is a determinant of hatchling size in Sepiola atlantica d′Orbigny, 1839–1842. Successful hatching occurred in 98.5–100% of the eggs for each female. As seen in other coleoid cephalopods, temperature determines the amount of time for embryonic development in S. atlantica, and the obtained data were very similar to other coleoid cephalopods. Developmental times for temperatures at 13 ± 0.4°C, 18 ± 0.3°C and 16.4 ± 1.1°C were 61.8 ± 3.8, 22.6 ± 1.7 and 40.1 ± 4.8 days. The duration of embryonic development and hatchling mantle length was not strictly related. The egg volume was positively related to hatchling mantle length. Our results provide new records on the duration of embryogenesis and other information on reproductive patterns in this species. Some hatching and post-hatching behaviour are shown and discussed.     

Egg shell quality,clutch size and hatching success of the great tit (Parus major) and the pied flycatcher (Ficedula hypoleuca) in an air pollution gradient

Egg shell thickness, egg volume, clutch size and hatching success of Parus major and Ficedula hypoleuca were studied at 14 study sites around a copper smelter complex in Harjavalta, south-west Finland, in 1991–1993. In 1991–1992 unhatched eggs were collected to measure shell quality. F. hypoleuca was more susceptible to pollutants than P. major, the response of which was weaker in all aspects studied. Egg shells of F. hypoleuca were about 17% thinner and eggs were about 8% smaller in volume near the factory than at a distance of 10 km. The clutch size of F. hypoleuca was significantly smaller and hatching success markedly lower at a study site next to the factory complex than at all other sites. In P. major, variation in shell thickness and egg volume was not significantly related to the distance from the pollution source. Clutch size and hatching success of P. major did not significantly differ among study sites, although the trend in hatching success was in the same direction as in F. hypoleuca. Clutches of both species contained less shell material and both species had more nests without eggs near the factory than further away. The surface structure of the eggshells was studied by scanning electron microscope. Especially in F. hypoleuca, the egg shell surface was more rough and porous near the factory. The roles of Ca and heavy metals in shell thinning are discussed.     

Molecular data and phylogenetic analysis of Myxobolus pseudonobilis n. sp. infecting the gill filaments of silver carp,Hypophthalmichthys molitrix Valenciennes, 1844

In the present study, we combined morphological and phylogenetic methods to characterize Myxobolus pseudonobilis n. sp. infecting Hypophthalmichthys molitrix Valenciennes, 1844 from Chongqing, China. The morphology and molecular characteristics of M. pseudonobilis n. sp. were distinct from those of other previously described Myxobolus species. Mature myxospores were ovoid in frontal view with spore dimensions of 10.0 ± 0.4 (9.3–10.9) μm in length and 8.5 ± 0.2 (7.9–9.0) μm in width. Two polar capsules occupying approximately half of the myxospore length were unequal in size. The larger polar capsule containing 6 to 7 filament coils measured 5.2 ± 0.3 (4.5–5.8) μm in length and 3.6 ± 0.2 (3.2–3.9) μm in width, while the smaller capsule with 4 to 5 filament coils measured 3.9 ± 0.3 (3.0–4.4) μm in length and 2.5 ± 0.3 (2.1–3.6) μm in width. The comparison of molecular characteristics demonstrated similarities and genetic distances of 18S rDNA sequences of 95.19% - 98.20% and 1.82% - 5.46%, respectively, between M. pseudonobilis n. sp. and its morphologically similar species, and secondary structures were also distinctly different. Moreover, phylogenetic analysis showed that M. pseudonobilis n. sp. was clustered with other myxobolids possessing spores with a blunt anterior end and branched independently. In addition, the morphology of myxosporeans as an important indicator was discussed.     

Reproduction of the wedge sole (<Emphasis Type="Italic">Dicologoglossa cuneata</Emphasis> Moreau) in captivity: spawning parameters and influence of the natural temperature

In this work, the wedge sole (Dicologoglossa cuneata) spawning under a natural thermocycle has been studied. The spawning parameters were similar to those of other flatfish in captivity, the relative fecundity being very high (1.7 ± 0.1 × 10⁶ eggs kg female⁻¹ per spawning season). The percentage of floating eggs decreased with time and was directly related to egg diameter, daily relative fecundity and fertilization rate. Nevertheless, the hatching rate variations were not correlated to any other spawning parameter. The temperature range during the spawning season was very wide (11–21°C) though the largest spawns occurred between 12 and 16°C. The natural temperature cycle influenced wedge sole egg production, the winter temperature minimum indicating the onset of spawning, but the variations in the reproductive season did not appear to affect the daily egg production. Future research should focus on the photoperiod and its interaction with temperature as key factor for spawning.     

Embryology and early ontogeny of an endemic tooth‐carp fish,Aphanius sophiae (Heckel, 1847)

Understanding embryonic development and ontogeny of species is a crucial part of any further biology, ecology and conservation studies. The present study describes the first detailed normal embryonic development of a tooth‐carp, Aphanius sophiae (Heckel, 1847), from fertilization to post‐ hatching. Aphanius sophiae spontaneously spawned at 24 ± 1°C. The newly laid eggs were transparent and spherical (1.45 ± 0.20 mm). We documented developmental times at 24 ± 1°C to egg activation (0.5 hr), cleavage (3 hr), blastula (10 hr), gastrula (20 hr), neurula (24 hr), somite (28 hr), turnover (60 hr), blood circulation (70 hr) and hatching (330 hr). This study contributes to a further understanding of the embryology and the early ontogeny of A. sophiae and may help improve the culture of other threatened species of the genus Aphanius.     

Effect of female aging on the morphology and hatchability of resting eggs in the rotifer <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> Müller

This study examined the morphology and hatchability of Brachionus plicatilis resting eggs as a function of the aging of maternal fertilized mictic females. One-hundred twenty fertilized B. plicatilis (Australian strain) were individually cultured and monitored daily until death. All cultures were maintained at 25°C, 11 ppt, and fed the micro-algae Tetraselmis tetrathele. Resting eggs produced by the females were investigated using two parameters: egg morphology, and hatching rate. Under these culture conditions, females normally produce 1–6 (mean ± SD = 2.7 ± 1.2) resting eggs during their lifetime. However, the number of resting eggs with abnormal morphology increased as a function of maternal age. Among resting eggs with normal morphology (n = 225), 82.2% were produced during the first and second spawning, and had hatching rates of more than 60%, while the hatching rates were below 30% in resting eggs with a spawning order of >2. Thus, the quality of B. plicatilis resting eggs was negatively correlated with maternal age.     

Reproductive success of wild Lesser Rheas (Pterocnemia -Rhea- pennata pennata) in north-western Patagonia, Argentina

We studied the reproductive success of a wild Lesser Rhea population (Pterocnemia -Rhea- pennata pennata) during two reproductive seasons (2004/2005 and 2005/2006) in north-western Patagonia, Argentina. The parameters recorded included population and nest density, clutch size, hatching success, chick survival (up to 3 months of age) and percentage of chicks that reached the juvenile stage after the winter. We also estimated the percentage of males that attempted to nest and of those that were successful (those producing at least one chick), daily nest mortality rates (DNMR) at different stages of the nesting cycle and the probability that an egg that has been recently laid will produce a chick. On average, both years pooled, the density of this population of Lesser Rheas was 1.55 ± 0.2 individuals/km² (SE), nest density was 0.17 ± 0.04 per km ² , clutch size was 20.8 ± 6.4 eggs, hatching success was 74.4% ± 11.3, Mayfield’s probability of an egg that will produce a chick was 0.64, chick survival was 65.4% ± 14.5 and percentage of chicks that reached the juvenile stage was 26.3%. Nearly a quarter of Lesser Rhea males in the population attempted to nest during a breeding season, and the DNMR was significantly higher during the laying stage (most nest failures were due to anthropogenic disturbances related to livestock raising activities). Nesting success, hatching success, and chick survival of Lesser Rheas were higher than those of their most closely related species, the Greater Rhea (Rhea americana), whereas the percentage of chicks that reached the juvenile stage was similar due to high winter mortalities of chicks. We suggest that the increase in reproductive effort is a strategy of this species to overcome environmental constraints.     

First confirmed complete incubation of a flapper skate (Dipturus intermedius) egg in captivity

An egg of the critically endangered flapper skate Dipturus intermedius was successfully incubated to hatching in captivity in what is believed to be a first for the species. Water conditions (temperature, salinity, flow rate) were recorded, with mean water temperatures ranging from a monthly mean of 8.3 ± 1.2 to 13.2 ± 0.3°C and salinity from a monthly mean of 30.5 ± 1.2 to 36.6 ± 2.3 ppt. Hatching occurred after 534 days, suggesting that flapper skate eggs take c. 5700 growing degree-days to incubate to hatching. The egg's prolonged embryonic development raises concerns about flapper skate eggs' vulnerability to anthropogenic disturbance.     

Larval release behaviors of the striped hermit crab, Clibanarius vittatus (Bosc): Temporal pattern in hatching

Ovigerous hermit crabs, Clibanarius vittatus (Bosc), were examined in the laboratory to (1) determine if the time of larval release is a synchronous event, (2) determine the influence of a damaged gastropod shell during the egg hatching process, and (3) describe larval release behaviors. Ovigerous hermit crabs from natural light:dark (LD) and tidal cycles were moved to constant conditions 2-3 days prior to the predicted time of larval release. Larval release was synchronous, occurring near the time of expected sunset. Females with early-stage embryos placed under constant conditions displayed a free-running circadian rhythm, suggesting that the rhythm is under endogenous control. Hermit crabs with early-stage embryos that were placed under a shifted LD cycle (advanced 12 h relative to the ambient photoperiod) before being placed under constant conditions advanced their larval release rhythm by 12 h, indicating the rhythm can be entrained by the LD cycle. Hermit crabs with an intact shell released larvae in bursts at sunset over several consecutive nights (period = 24.2 h). In contrast, hermit crabs with damaged shells released larvae at different times over the course of a single day. Ovigerous females with intact shells exhibit several stereotypical hatching behaviors. The female stands on her walking legs and thrusts her abdomen, moving the shell in an oscillating motion. This movement may assist in breaking the outer membrane of the egg case. The female generates a water current inside the shell with her scaphognathite and mouthparts, which transports the newly hatched larvae out of the shell. Females in damaged shells did not display these behaviors; instead, larval release was a prolonged event with little movement of the female, and often the newly hatched larvae were not viable. These results indicate that an intact shell plays an important role in the hatching process for this hermit crab.     

Impacts of exposure to mine tailings on zooplankton hatching from a resting egg bank

In the last five years, two colossal environmental disasters involving iron-enriched mine tailings have occurred in Brazil, affecting many aquatic ecosystems over the short, medium and long-terms. This study investigated whether these iron-enriched mine tailings affect the main biotic strategy to restore zooplankton populations affected by severe stress, i.e., hatching of dormant stages. A 30 day hatching experiment was conducted, using a resting egg bank from a natural lake, exposed to 3 concentrations of mine tailings: control (0 g), T25 (25 g) and T50 (50 g). A total of 22, 15 and 16 species hatched in the control, T25 and T50, respectively. Conochilus sp., Filinia terminalis, Hexartha mira, Bosmina longirostris and Ceriodaphnia silvestrii hatched only in the control, which suggests that these species are sensitive to any concentration of mine tailings. A gradual decrease in richness and hatchling abundance was recorded, from the control (8.0?±?1.0 SE species and 1597?±?73.9 hatchlings) to T25 (4.6?±?1.2 species and 1279?±?136.5 hatchlings) and then to T50 (2.3?±?1.2 species and 603.3?±?61.9 hatchlings). Our results suggest that exposure of zooplankton resting eggs to iron-enriched mine tailings may negatively impact these egg banks in natural ecosystems, with potential impacts on the restoration of zooplankton communities after even short-term exposures.

Graphic abstract

     

Higher risk of fatality by predatory attacks in earlier ontogenetic stages of modern Nautilus pompilius in the Philippines: evidence from the ontogenetic analyses of shell repairs

The shell repair scars of modern Nautilus pompilius in the Philippines presumably due to sub‐lethal predatory attacks were examined throughout ontogeny ranging from hatching to maturity, revealing the higher risk of fatality in earlier ontogenetic stages. The examinations throughout ontogeny demonstrate that: (1) sub‐lethal predatory attacks by other organisms have no preferred position through ontogeny; (2) the sizes of shell repair scars are similar throughout ontogeny and, therefore, the width and length of shell repair scars relative to shell diameter decrease from hatching towards maturity; and (3) the proportion of sub‐lethal predatory attacks within 10 mm increments of shell diameter are similar irrespective of shell diameter or decrease approaching maturity. The numbers of the irregular, radiating, black shell repair scars, indicating injury to the soft parts at shell breakage, decrease at a diameter >80 mm and none were found at <56 mm in shell diameter. Furthermore, the rarity of juvenile trapping data might be related to the higher fatality from predatory attacks in earlier ontogenetic stages, providing crucial information for the conservation of N. pompilius.     

Modulating effect of a magnetic field on Saprolegnia parasitica,Coker, 1923 infecting trout (Salmo trutta,L.) eggs

The aim of study was to investigate the effects of static magnetic fields [1 mT (miliTesla), 5 and 10 mT] on Saprolegnia parasitica growth, development, and cytotoxicity in the infection of trout eggs in hatcheries under laboratory and industrial conditions. The egg envelope (SEM) structures resulting from infection with and development of S. parasitica are also presented. S. parasitica mycelium was cultured on a microbiological medium SDA in Petri dishes (4 ± 0.2°C, 97% humidity) exposed to a magnetic field and in a control, to assess the mycelium growth rate. Effects of the magnetic field on cytotoxicity of S. parasitica after a 21‐day incubation on SDA medium were analyzed using the colorimetric cytotoxicity test MTT. Eggs of brown trout Salmo trutta were infected with S. parasitica by inoculum and incubated in glass vessels (4 ± 0.2°C) in a magnetic field and a control. The degree of mycelium invasion of the egg envelopes and the percentage of egg mortality were recorded daily thoughout the period of embrionic development. The magnetic field effects on brown trout eggs infected by wild strains of fungus‐like organisms (FLO) in the hatchery (4°C ± 0.1) were also investigated. Changes in the structure of brown trout egg envelopes as a result of infection and development of S. parasitica were examined in a FIB/SEM. The effects of magnetic fields of 5 and 10 mT on slowing the growth of mycelium of S. parasitica in vitro were also observed. Determining biochemical properties of S. parasitica also showed the effects of the magnetic field in differentiating the cytotoxicity. All magnetic field values showed a distinct decrease from medium to low values of S. parasitica cytotoxicity; the most effective reduction was observed at 5 mT. Magnetic fields in all tested levels slowed development of the mycelium on the incubated trout eggs, resulting in a decrease in the number of eggs infected by S. parasitica and thus permitting a greater hatching success. Similar effects were observed in other hatching conditions where eggs were also exposed. No negative effects of magnetic field treatment on the condition of the newly‐hatched larvae were observed. The SEM and FIB (Focused Ion Beam) analyses revealed penetration of S. parasitica via radial canals of the envelope. The magnetic field had no effect on the structure of hyphae or sporangia of S. parasitica, but did affect the growth rate of mycelium on the egg surface.     

Egg capsules, eggs and embryos of the southwestern Atlantic gastropod Coronium coronatum (Gastropoda: Muricidae)

The egg capsules, eggs and embryos of the muricid gastropodCoronium coronatum are described for the first time. Capsulesare sessile, bulliform, semi-circular, with a plug in the dorsalcenter. Sutures split the capsule into two asymmetrical halves.Recently laid capsules showed the presence of 3639 (n = 2) uncleavednurse eggs with a diameter of 180–210 µm (mean= 197.4 ± 8.9). The number of early embryos was 9–11.The size of the embryos was 320 x 320 to 820–880 µm.Nine pre-hatching embryos of 3.94 mm (n = 8, SD = 0.32)were found inside the older capsule. SEM illustrations of embryosand radulae are provided. Comparison of shell and radula ofembryos with the protoconch and radulae of adults of C. coronatumrevealed that the capsule belongs to this species. (Received 18 March 2006; accepted 10 October 2006)     

Assessment of egg quality and realised fecundity of whiting Merlangius merlangus L. in captivity

Potential predictors of egg quality were assessed in whiting Merlangius merlangus L. permitted to spawn in a tank from which eggs were collected. These included fertilisation rate, the proportion of viable buoyant eggs, egg diameter, and egg wet and dry weights; all were influenced by temporal effects and were negatively correlated with days from start of spawning. The spawning period was protracted, from February to June. Mean daily egg production per female was 2.74 ± 2.43 g and 2338 ± 2075 eggs, equivalent to 14.6 ± 13.1 g kg^?1 day^?1 female^?1. Egg diameter was 1.21 ± 0.04 mm, egg wet weight 1.20 ± 0.21 mg, dry weight 0.10 ± 0.02 mg, and mean fertilisation rate and hatching rates were 76.8 and 73.3%, respectively. The incubation period ranged from 72 to 80 degree days and was dependent on temperature (x) and described by the equation y = 25.92 e^?0.1219x. Realised fecundity was also assessed to determine if this gave a more accurate measure of reproductive potential, and this was compared with potential fecundity estimated from predictive regressions on fish length from fisheries data. Realised egg production of 20 females of 185 g mean weight and 256 mm fork length was 4 444 360 (95% CL 4 093 961–4 743 018), similar to predicted seasonal egg production based on gravimetric fecundity measurements of wild caught fish.     

Brooding in Psolus patagonicus (Echinodermata: Holothuroidea) from Argentina, SW Atlantic Ocean

The mode, season, and time of brooding, egg diameter, egg number per brood, and the characteristics of newly released juveniles of Psolus patagonicus were investigated off Mar del Plata, Buenos Aires, Argentina, between October 1999 and February 2001. Individuals were attached to the Patagonian scallop, Zygochlamys patagonica. Spawning occurs between February and March. The mean egg diameter, 887 ± 26 μm, is the highest reported for the family Psolidae. Eggs are brooded under the mother’s sole until they develop into crawling juveniles within 7 months. The largest embryos reached a length of 1,941 ± 228 μm in September. During the brooding period (February–September) the number of brooded embryos decreased while their size increased. Our study confirms brooding behaviour in female P. patagonicus.     

Effects of Tissue Collection Methods on Morphometrics and Survival of Captive Neonatal Northern Bobwhite

ABSTRACT We assessed effects of tissue collection methods (i.e., patagial microbiopsy and down feathers) and chick age at sampling on morphometrics and 21-day survival of 600 captive neonatal northern bobwhite (Colinus virginianus). We observed minimal effects on morphometrics and no difference in survival among patagial microbiopsy (x̄ = 0.96 ± 0.03), down feathers (x̄ = 0.92 ± 0.04), and control (x̄ = 0.86 ± 0.05) methods. DNA analysis from patagial microbiopsy, down feather, and egg tooth samples showed greater concentrations of DNA from patagial microbiopsy (x̄ = 10.28 ± 1.74 μg/ml) than either down feather (x̄ = 4.10 ± 1.74 μg/ml) or egg teeth (x̄ = 2.35 ± 1.74 μg/ml).     

Embryonic development of the false limpet Siphonaria lateralis from Atlantic Patagonia

Siphonariids are pulmonate gastropods inhabiting rocky intertidal habitats, and many studies have focused on these false limpets around the world. In the southern South Atlantic, studies on reproduction and development in species of Siphonaria are scarce. We studied the embryonic development and egg masses of Siphonaria lateralis at its northernmost distribution in Atlantic Patagonia. In S. lateralis, as in most species of Siphonaria, individuals spawn benthic egg masses that strongly attach to intertidal rocky substrata. A single spherical egg that measures ~120 µm develops inside the egg capsule of S. lateralis. Considering the relatively small egg size, and reports from previous studies, the developmental modality of S. lateralis might be expected to include a planktotrophic larval phase. However, we found that hatchlings emerged as 1‐mm crawling juveniles, probably owing to the presence of intracapsular fluid, which may provide the energetic requirements for direct development. The embryonic size changed little from the egg to veliger stages, and then increased rapidly until the hatchling stage. We compared development in S. lateralis with development in the sympatric Siphonaria lessonii, in which egg size was reported to be ~80 µm and hatching occurs as planktotrophic veliger larvae. In these two species, spawn and early intracapsular developmental modes are remarkably different; these differences represent contrasting ways to survive in the harsh and physically stressful intertidal Patagonian coasts.