The reproductive cycle of the sea urchin Psammechinus miliaris (Echinodermata: Echinoidea) in a Scottish sea loch

2000 ◽  
Vol 80 (5) ◽  
pp. 909-919 ◽  
Author(s):  
Maeve S. Kelly
Keyword(s):  
Sea Urchin ◽  
Annual Cycle ◽  
Developmental Stages ◽  
Food Resource ◽  
Gonad Development ◽  
Market Place ◽  
Spawning Period ◽  
Psammechinus Miliaris ◽  
Population Recruitment ◽  
Time Of Year

The sea urchin Psammechinus miliaris was sampled at monthly intervals from two replicate sites at contrasting locations (littoral and subtidal habitats) on the west coast of Scotland. Samples were collected from November 1995 to October 1997. A study of gonad development showed a clearly defined annual cycle of gametogenesis with a single spawning period. Gonad indices (GIs) varied between locations, between sites at the same location and between study years. Gonad indices were maximal prior to the onset of the spawning period in June and July. Ripe gametes were shed by dissected urchins from June to September in 1996 and June to August in 1997 coinciding with the time of year when the gonad colour was best in terms of what is desired in the market place. Over winter the GIs were very low and gonads became very dark in colour. Higher summer GIs in the urchins from one littoral site suggested that the urchins there had a seasonal influx of a more nutritious or more abundant food resource. Histological determination of the reproductive state showed that for these food-limited populations high GIs do equate with the spawning period. The gametogenic cycle fits the six stage pattern described for other echinoid species. In females oocytes of various developmental stages were present throughout the annual cycle. Recruitment to the littoral location was monitored over two seasons by quantifying the number of urchins with a test diameter <5 mm appearing in the population. Recruitment appeared variable between sites and between seasons suggesting that the collection of juveniles resulting from natural settlement may not be a reliable alternative to hatchery produced spat. Although P. miliaris has commercial potential when in cultivation, this study provided no evidence of an opportunity for a commercial fishery.

The Mechanism of Cell-division

1953 ◽  
Vol s3-94 (28) ◽  
pp. 369-379
Author(s):  
M. M. SWANN
Keyword(s):  
Carbon Monoxide ◽  
Cell Division ◽  
Sea Urchin ◽  
White Light ◽  
Time Lapse ◽  
Psammechinus Miliaris ◽  
Energy Store ◽  
Time Lapse Photography

1. Developing eggs of the sea-urchin Psammechinus miliaris were subjected to carbon monoxide inhibition, which was controlled by changing from green to white light. The behaviour of the eggs was recorded by time-lapse photography. 2. If inhibition is applied before the eggs enter mitosis, their first cleavage is delayed by a time which is roughly equal to the period of the inhibition. 3. If the inhibition is applied when the cells have already entered mitosis, they complete mitosis and cleave with little or no delay, but their second cleavage is delayed by a time which is roughly equal to the period of the inhibition. 4. It is suggested that the necessary energy for the second mitosis and cleavage is being stored up during the first mitosis and cleavage, and that this energy store operates like a reservoir which is continually being filled but siphons out when it is full. Once the energy has siphoned out, it carries mitosis and cleavage through, even though the reservoir is not filling up because of carbon monoxide inhibition.

scholarly journals Spawning season, recruitment and early life distribution of Anchoa tricolor (Spix and Agassiz, 1829) in a tropical bay in southeastern Brazil

2008 ◽  
Vol 68 (4) ◽  
pp. 823-829 ◽  
Author(s):  
FG. Araújo ◽  
MA. Silva ◽  
MCC. Azevedo ◽  
JNS. Santos
Keyword(s):  
Early Life ◽  
Gonad Development ◽  
Late Summer ◽  
Sandy Beaches ◽  
Reproductive Season ◽  
Southeastern Brazil ◽  
Life Distribution ◽  
Beach Seine ◽  
Spawning Period ◽  
Fishery Resource

The pattern of the use of the Sepetiba Bay, a semi-closed 450 km² area in southeastern Brazil, by Anchoa tricolor was investigated to assess spawning period, recruitment and to detect spatial-temporal patterns of this major fishery resource. Fishes were sampled by seine nets, from spring, 1998 to winter, 1999 and by beach seine, from spring, 1998 to winter, 2000. Reproductive season, measured in terms of GSI, gonad development and appearance of recruits, indicate that reproduction occurs from August to March, when they reach the best condition. Recruitment peaks in winter/spring at sandy beaches where they stay until late summer, moving toward deeper bay areas during autumn. After that, they join adults and perform movements between the bay and the adjacent continental shelf to reproduce.

The Fertilization Reaction in the Sea-Urchin

1952 ◽  
Vol 29 (3) ◽  
pp. 469-483
Author(s):  
LORD ROTHSCHILD ◽  
M. M. SWANN
Keyword(s):  
Sea Urchin ◽  
Sea Urchins ◽  
Standard Errors ◽  
Conduction Time ◽  
Normal Sperm ◽  
Psammechinus Miliaris ◽  
Sperm Suspension ◽  
Small Incidence ◽  
High Concentrations ◽  
First Time

1. The reactions of sea-urchin eggs (Psammechinus miliaris) to high concentrations of homologous spermatozoa have been investigated by a new method. 2. The method was to inseminate eggs with high concentrations of spermatozoa (108/ml.), which ensured that all eggs were fertilized for the first time at the beginning of the experiment; and then functionally to separate the eggs and spermatozoa at known times after the original insemination. 3. The proportion of polyspermic eggs in the suspension rises from zero at t=0 to a constant value at a time T, which is the conduction time of the block to polyspermy. In fourteen experiments on eggs from different sea-urchins, the estimated values of T were 17, 69, 72, 74, 94, 85, 26, 60, 31, 91, 85, 34, 75 and 67 sec. (arithmetic mean 63 sec.). The standard errors of the estimates of T, which are tabulated in the text, ranged from 5 to 15 sec. 4. These results confirm previous experiments which strongly suggested that the conduction time of the block to polyspermy was of the order of seconds; these earlier experiments were incompatible with a block to polyspermy lasting a fraction of a second. 5. At the same time experiments in this paper made it possible to estimate the fertilization parameter or sperm-egg interaction rate α, during the conduction of the block to polyspermy, and to compare it with the pre-fertilization α. In a given sperm suspension, α is a measure of the receptivity of the egg surface to spermatozoa. During the conduction of the block to polyspermy α was found to be markedly lower (1/20) than in unfertilized eggs. 6. This suggests that at fertilization there is a fast but incomplete block to polyspermy, whose conduction time may be 1 sec. or less. This is followed by the slower block which finally makes the egg impermeable to spermatozoa. This also confirms previous observations on the small incidence of polyspermy at normal sperm densities, which is not consistent with the concept of a slow block to polyspermy.

Distribution and abundance of euphausiid larvae in the Prydz Bay region, Antarctica

1991 ◽  
Vol 3 (2) ◽  
pp. 167-180 ◽  
Author(s):  
G.W. Hosie
Keyword(s):  
Antarctic Circumpolar Current ◽  
Developmental Stages ◽  
Euphausia Superba ◽  
Prydz Bay ◽  
Spawning Period ◽  
North East ◽  
East Wind ◽  
Thysanoessa Macrura ◽  
Circumpolar Current ◽  
The Antarctic

In January 1985 a net sampling survey was carried out on the distribution and abundance of euphausiid larvae in the Prydz Bay region. Euphausia superba occurred in low abundance, probably due to sampling preceding the main spawning period. Thysanoessa macrura occurred throughout the study area in consistently high abundance. Euphausia crystallorophias was marginally more abundant within its restricted range. Distinct north-south variations in larval age and developmental stages of T. macrura were observed indicating regional differences in spawning. Euphausia frigida was mainly confined to the upper 200 m of the Antarctic Circumpolar Current. E. superba larvae produced north of the shelf break, between 70°–83°E, moved north-east into the Antarctic Circumpolar Current. Larvae originating on the shelf moved rapidly west in the East Wind drift. E. crystallorophias had the same westward dispersion, but some larvae appeared to return eastward via the Prydz Bay Gyre and remain in the region. The data indicate that most E. superba larvae, providing they survive injuries cold temperature an food deprivation, will leave the area, suggests that Prydz Bay krill may not be a self maintaining stock.

scholarly journals An Updated Overview on the Regulation of Seed Germination

Plants ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 703 ◽  
Author(s):  
Gerardo Carrera-Castaño ◽  
Julián Calleja-Cabrera ◽  
Mónica Pernas ◽  
Luis Gómez ◽  
Luis Oñate-Sánchez
Keyword(s):  
Seed Germination ◽  
Developmental Stages ◽  
Developmental Process ◽  
Point Of View ◽  
Growth Stages ◽  
Tissue Properties ◽  
Specific Regulation ◽  
Time Of Year ◽  
The Right ◽  
The Impact

The ability of a seed to germinate and establish a plant at the right time of year is of vital importance from an ecological and economical point of view. Due to the fragility of these early growth stages, their swiftness and robustness will impact later developmental stages and crop yield. These traits are modulated by a continuous interaction between the genetic makeup of the plant and the environment from seed production to germination stages. In this review, we have summarized the established knowledge on the control of seed germination from a molecular and a genetic perspective. This serves as a “backbone” to integrate the latest developments in the field. These include the link of germination to events occurring in the mother plant influenced by the environment, the impact of changes in the chromatin landscape, the discovery of new players and new insights related to well-known master regulators. Finally, results from recent studies on hormone transport, signaling, and biophysical and mechanical tissue properties are underscoring the relevance of tissue-specific regulation and the interplay of signals in this crucial developmental process.

scholarly journals Gonad development and reproductive hormones of invasive silver carp (Hypophthalmichthys molitrix) in the Illinois River

2019 ◽  
Vol 102 (3) ◽  
pp. 647-659
Author(s):  
Emily K Tucker ◽  
Megan E Zurliene ◽  
Cory D Suski ◽  
Romana A Nowak
Keyword(s):  
Silver Carp ◽  
Gonad Development ◽  
Life History Strategy ◽  
High Plasma ◽  
Early Summer ◽  
Reproductive Hormones ◽  
Illinois River ◽  
Plasma Testosterone ◽  
Hypophthalmichthys Molitrix ◽  
Spawning Period

Abstract Reproduction is a major component of an animal’s life history strategy. Species with plasticity in their reproductive biology are likely to be successful as an invasive species, as they can adapt their reproductive effort during various phases of a biological invasion. Silver carp (Hypophthalmicthys molitrix), an invasive cyprinid in North America, display wide variation in reproductive strategies across both their native and introduced ranges, though the specifics of silver carp reproduction in the Illinois River have not been established. We assessed reproductive status using histological and endocrinological methods in silver carp between April and October 2018, with additional histological data from August to October 2017. Here, we show that female silver carp are batch spawners with asynchronous, indeterminate oocyte recruitment, while male silver carp utilize a determinate pattern of spermatogenesis which ceases in the early summer. High plasma testosterone levels in females could be responsible for regulating oocyte development. Our results suggest that silver carp have high spawning activity in the early summer (May–June), but outside of the peak spawning period, female silver carp can maintain spawning-capable status by adjusting rates of gametogenesis and atresia in response to environmental conditions, while males regress their gonads as early as July. The results of this study are compared to reports of silver carp reproduction in other North American rivers as well as in Asia.

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