Photoperiodic regulation of feeding and reproduction in a brooding sea star from central California

Summary

Individuals of the sea star genus Leptasterias from the Monterey Peninsula, California, were maintained for 34 months under two contrasting regimes of seasonally changing photoperiod. In one regime the lights turned on and off in phase with local sunrise and sunset; in the other the daily photoperiod was kept 6 months out of phase with ambient photoperiods. Annual cycles of feeding, gametogenesis, and embryo brooding of the out-of-phase animals were all shifted out of phase with respect to those of the in-phase animals. These small, relatively hardy sea stars appear well suited for more detailed analyses of photoperiodism in asteroids.     

Photoperiodic regulation of gametogenesis in a North Atlantic sea star,Asterias vulgaris

Summary

Individuals of the sea star Asterias vulgaris from New Hampshire were maintained under two contrasting regimes of seasonally changing photoperiod. In one regime the lights turned on and off in phase with local sunrise and sunset; in the other, the daily photoperiod was kept 6 months out of phase with ambient photo- period. When dissected after being maintained for 18 months, the gametogenic condition of the out-of-phase animals was found to be 6 months out of phase with that of the in-phase animals. This experiment demonstrates that photoperiodic regulation of reproduction is important even in marine animals that normally experience marked seasonal changes in sea temperature.     

The annual gametogenic cycle of the sea anemone Metridium senile from the Gulf of Maine

A year-long study was conducted to quantify the reproductive cycle of the clonal sea anemone, Metridium senile, an important member of the benthic community in the Gulf of Maine (GOM). M.senile is an abundant sessile invertebrate that forms identifiable clonal aggregations that are maintained by pedal laceration but individuals can also reproduce sexually. Specimens were collected monthly from a shallow (< 10 m) subtidal site and the reproductive cycle of male and female anemones was described on a seasonal basis using histological preparation of the gonads and light microscopy. Gametogenesis was determined for both sexes and showed that females undergo spawning during the seasonal transition from summer to fall, while males have mature sperm within testicular cysts in the winter, spring, and summer. Environmental data recorded at the study site shows that the spawning period occurs during a period of peak water temperature (August-September), and rapid gametogenesis occurs during periods of high food availability (April). The low percentage of reproductively mature anemones and the dominance of asexual reproduction in this population are believed to be the result of the high flow regime at this site.     

Effect of Fixed Daylengths on the Photoperiodic Regulation of Gametogenesis in the Sea Urchin Strongylocentrotus purpuratus

Summary

The gametogenic response of the sea urchin Strongylocentrotus purpuratus was compared under treatments of different photoperiod regimes of fixed and seasonal changing daylength. Quantification of gametogenic activity in en- zymatically dissagregated ovaries and in histological sections of testes have shown that the sea urchin is sensitive to both fixed and variable daylengths. After one year at fixed short day (8L:16D) or fixed neutral day (12L:12D) the gonads were ripe and in active gametogenesis, the same as were gonads of animals reared at changing photoperiod and sampled during the short-day phase of the cycle. Under fixed long day (16L:8D) the gonads lacked significant amount of gametes and had the cell constitution found in gonads of animals reared at changing photoperiod and sampled during the long-day phase of the cycle. Measurement of a critical daylength related to the autumnal equinox seems to be part of the mechanism in the photoperiodic regulation of vitellogenic oocyte growth and spermatogenesis in these animals.     

ENVIRONMENTAL CONTROL OF GAMETOGENESIS IN LAMINARIA SACCHARINA. IV. IN SITU DEVELOPMENT OF GAMETOPHYTES AND YOUNG SPOROPHYTES1,2

Meiospores of Laminaria saccharina labeled with a fluorescent stain were put into the sea and recovered at frequent intervals. They developed into gametophytes which produced gametes throughout the year. Antheridia were produced earlier than oogonia. Gametogenesis was slowest during the late autumn and early winter. On the basis of nutritional studies and the seasonal distribution of nutrients, it was concluded that the rate of gametogenesis was not due to nutrient deficiency but most likely to light. Production of macroscopic sporophytes appeared to be limited by survival of microscopic sporophytes rather than gametogenesis. Macroscopic sporophytes became evident during the late winter and autumn. The greater light and perhaps higher temperatures of summer were suggested as agents limiting macroscopic sporophyte production during this period.     

A 91-year record of seasonal and interannual variability of diatoms from laminated sediments in Saanich Inlet, British Columbia

Diatom seasonal succession and interannual variability werestudied using laminated sediments from Saanich Inlet, BritishColumbia, for the years 1900–1991. Frozen sediment coresallowed fine-scale sampling of laminae for each year. Thus,three ‘seasons’ for each year were identified basedon species composition. Thalassiosira species were indicatorsof spring deposition. Skeletonema costatum was abundant in samplesfollowing Thalassiosira, probably deposited in late spring andsummer. Rhizosolenia sp. was most abundant in fall/winter samples.Diatom stratigraphies were related to sea surface temperature,salinity, sea level and the Pacific North American Index (PNA)using canonical correspondence analysis (CCA). CCA showed thatspecies of a particular season generally had optima for temperatureand salinity characteristic of that time. Interannual changesin diatom species composition and abundance were most prevalentin the decades 1920–1940, with the exception of S.costatumwhich showed cyclic changes in abundance. Skeletonema was moreabundant during periods of cool temperatures, while littoraldiatoms were more abundant during times of heavy winter rains.Sea level was an important variable in CCA and while its relationshipto diatoms is not clear, it may be related to variations innutrient supply to diatoms in surface waters.     

The reproductive biology of the leech Helobdella stagnalis (L.) in Utah Lake, Utah

The reproductive biology of the glossiphoniid leech Helobdella stagnalis in Utah Lake, Utah was studied for an 18-month period from June 1970 to December 1971. In this lake it was found that the overwintering adult leeches produce two broods of young in May and June. Evidence is presented to support the idea that the same individual can produce two broods. Two complete cycles of gametogenesis also take place. Continuous water temperatures were recorded at the study site to correlate with reproductive activity. Gametogenesis appears to be temperature dependent with the first generation of sperm taking 4 months to be produced in the fall and winter months while the second generation of sperm is produced in 6 weeks during the spring. Egg production follows a similar pattem.     

麦双尾蚜及其天敌在不同海拔高度的分布

在新疆塔城,麦双尾蚜Diuraphis noxia (Mordvilko) 在春麦田最集中分布于海拔600～800 m 高度,在冬麦田最集中分布于700～800 m 高度;冬麦田和同海拔高度的春麦田麦双尾蚜数量密切相关(r=0.91, P<0.01)。麦双尾蚜寄生性天敌蚜茧蜂类和蚜小蜂类,在春麦田最集中分布的高度为500～600 m,随着时间的延后,分布的高度范围逐渐扩展;冬麦田最集中分布的高度为600～800 m,略高于春小麦田。捕食麦双尾蚜的斑腹蝇幼虫在春麦田前期最集中分布的高度为500 m处,后期分布高度上升;冬麦田较集中分布的高度为600～800 m,也随着时间的延后也上升。     

A comparison of photoperiodic control of diapause between aestivation and hibernation in the cabbage butterfly Pieris melete

In the cabbage butterfly, Pieris melete, summer and winter diapause are induced principally by long and short daylengths, respectively; the intermediate daylengths (12-13 h) permit pupae to develop without diapause. In this study, photoperiodic control of summer and winter diapause was systematically investigated in this butterfly by examining the photoperiodic response, the number of days required to induce 50% summer and winter diapause and the duration of diapausing pupae induced under different photoperiods. Photoperiodic response curves at 18 and 20 degrees C showed that all pupae entered winter diapause at short daylengths (8-11 h), the incidence of diapause dropped to 82.3-85.5% at 22 degrees C without showing a significant difference between short daylengths, whereas the incidence of summer diapause induced by different long daylengths (14-18 h) was varied and was obviously affected by temperature. By transferring from various short daylengths (LD 8:16, LD 9:15, LD 10:14 and LD 11:13) to an intermediate daylength (LD 12.5:11.5) at different times after hatching, the number of cycles required to induce 50% winter diapause (7.28 at LD 8:16, 7.16 at LD 9:15, 7.60 at LD 10:14 and 6.94 at LD 11:13) showed no significant difference, whereas by transferring from various long daylengths (LD 14:10, LD 15:9, LD 16:8 and LD 17:7) to an intermediate daylength (LD 12.5:11.5) at different times, the number of cycles required to induce 50% summer diapause (5.95 at LD 14:10, 8.02 at LD 15:9, 6.80 at LD 16:8, 7.64 at LD 17:7) were significantly different. The intensity of winter diapause induced under different short daylengths (LD 8:16, LD 9:15, LD 10:14 and LD 11:13) was not significantly different with an average diapause duration of 87 days at a constant temperature of 20 degrees C and 92 days at a mean daily temperature of 19.0 degrees C, whereas the intensity of summer diapause induced under different long daylengths (LD 14:10, LD 15:9, LD 16:8 and LD 17:7) was significantly different (the diapause duration ranged from 75 to 86 days at a constant temperature of 20 degrees C and from 76 to 88 days at a mean daily temperature of 19.0 degrees C). All results suggested that photoperiodic control of diapause induction and termination is significantly different between aestivation and hibernation.     

Can Experience Alter the Avian Annual Cycle? Results of Migration Experiments with Indigo Buntings

Field experiments were conducted during 2 years testing whether premature release on their familiar, perennial breeding territories would cause indigo buntings (Passerina cyanea) to delete spring migration from their annual cycle. In the first year, male buntings were captured on their breeding territories in summer and held indoors for the winter on the photoregime that they would have encountered in nature as fall migrants and winter residents. The following spring they were released at the time buntings begin spring migration from the subtropics. Half were released on their breeding territories, to which they would normally have returned; half were released far to the south. Some of the males released on their territories remained and passed into breeding condition without having migrated, while some of those released to the south returned north to their territories. The results suggest that endogenous or photoperiodic mechanisms controlling the timing and occurrence of migration in this species can be overridden by experience. In the second year we tested alternative explanations for these results. Our second year's results seem to indicate (1) that birds that deleted migration in year one did not do so because of unfavourable weather and (2) that the birds that returned to their breeding sites in year one were actually migrating and not simply retracing their outward journey.     

Acclimation of photosynthesis and pigments to seasonally changing light conditions in the endemic Antarctic red macroalga Palmaria decipiens

The influence of seasonally fluctuating Antarctic daylengths on the photosynthetic apparatus of Palmaria decipiens was studied in culture experiments. Maximal photosynthetic activity (ETRmax) and maximal quantum yield (Fv/Fm), measured by in vivo chlorophyll fluorescence, and concentrations of pigments (phycobiliproteins and Chl a) were determined monthly. Fv/Fm remained constantly high between 0.62 and 0.67 during mid-autumn, winter and spring. ETRmax and pigment contents increased continuously in mid-autumn and winter and were highest in spring. A positive correlation between pigments and ETRmax was found. In summer, ETRmax, Fv/Fm and pigment levels decreased to their lowest values. P. decipiens acclimated by increasing phycobilisome (PBS) number and changing PBS structure, probably changing rod length and rod number. The data show that P. decipiens is efficiently adapted to the short period of favourable light conditions in the field. A photoperiodic control of pigment synthesis triggered by daylength is suggested.     

A Two Phase Photoperiodic Response Controlling the Annual Gametogenic Cycle in Harmothoe imbricata (L.) (Polychaeta: Polynoidae)

Summary

In the polychaete Harmothoe imbricata, a photoperiodic mechanism stabilises oogenesis during its early stages and prevents oocyte breakdown. During the autumn, photoperiods of 14 hr light per day or more cause the animals to abort gametogenesis and resorb their oocytes. Conversely, photoperiods of 13 hr or less stabilise gametogenesis and allow normal oocyte growth. The length of the exposure required to stabilise gametogenesis and prevent abortion lies between 42 and 55 days. This effect is in addition to a previously described phenomenon causing accelerated oocyte growth in the spring in response to moderately long photoperiods. The interaction between these two different photoperiodic responses is discussed.     

Photoperiod and Reproduction in Lobsters (Homarus)

SYNOPSIS. Photoperiodic control of lobster (Homarus) ovipositionranges from none in the European species (H. gammarus) to atwo-phase requirement in some populations of H. americanus.In the inshore population from Massachusetts two to three monthsof shortday photoperiod appear necessary to condition the ovaryfor final vitellogenesis following long-day onset (LDO). Thestimulus of LDO is only effective near the time of molt. Ifmolt follows LDO within 120 days, egg extrusion follows themolt in about 80 days. If LDO follows the molt, extrusion occursin about 125 days. Extrusion delayed in this way delays thefollowing molt, which is also delayed by the retention of eggson the pleopods. In lobsters from Prince Edward Island the photoperiodic responseseen at laboratory temperatures (ca. 14°C) appears to besubordinated to a response to other cues, probably temperature,when females are held on a near-natural temperature regime withwinter minimum of 2°C characteristic of inshore environments.H. americanus from the migratory outer continental shelf populationexperience winter temperatures rarely lower than 8°C andprobably require photoperiodic control to initiate migrationas well as vitellogenesis. The photoperiodic response may haveoriginated in offshore populations during the Pleistocene andspread to more northerly inshore areas as habitat opened afterthe retreat of the continental ice sheet.     

Photoperiod and temperature as triggers in the seasonality ofDelesseria sanguinea

The red algaDelesseria sanguinea is strongly seasonal, producing gametangia in early tetrasporangia in mid- and new blades in late winter. A lamp was installed in the shallow subtidal off the Isle of Man, illuminating about 40 plants ofDelesseria for one hour in the night or day. Single blades from separate plants were held in laboratory tanks at different temperatures and in short days, long days and with a night-break. In the sea, the night-break prevented fertility in tetrasporophytes but some gametophytes became fertile. New blades were stimulated, arising 6 weeks early. Their lengths indicated a saturation level of about 10 μmol m⁻² s⁻¹ for one hour in 24. Growth rate calculations suggested a delay in stimulation until the ambient sea temperature dropped to 13°C. Tetrasporangia were formed after the night-break ceased in December but not January. In day-addition of light there was slight, if any, stimulation of blade production. In the laboratory, gametogenesis occurred readily in short days but not in long days or with a night-break. There was little or no effect of temperature between 8 and 14°C. Tetraspores were rarely formed in the laboratory. The timing of gametogenesis suggested a critical daylength of about 14 h. New blades were clearly stimulated by lower temperatures in the laboratory, few forming at 14°C and many at 7–10°C. They appeared mainly in long days or with a night-break but formed in short days after gametangia production. It is concluded that both gamete and tetraspore production are under photoperiodic control but require different conditions, possibly gametogenesis needing fewer cycles. There is some evidence for antagonism between new blade and reproductive structure initiation. The critical daylength could involve a timing differential of a month over the species geographical range. On the other hand it is suggested that its southern limit could be determined by the winter isotherm of 13°C, warmer than which might not allow blade initiation.     

The Influence of Nicotinic Acid and Plant Hormones on Flowering in Lemna

Nicotinic acid induces flowering in Lemna paucicostata 151 and381 and Lemna gibba G3 when they are grown in one tenth-strengthM medium under continuous light. For L. paucicostata 151 and381, the simultaneous addition of IAA, GA₃ or ABA to the mediumleads to an inhibition of the flower-inducing effect of nicotinicacid, while zeatin leads to a further stimulation of floweringabove that obtained by nicotinic acid alone. By contrast, inL. gibba G3 all four plant hormones inhibit the nicotinic acid-inducedstimulation of flowering. The effect of nicotinic acid on flowering in all three plantsis strongly daylength dependent when the plants are grown inhalf-strength Hutner's medium. Thus, nicotinic acid causes floweringin L. gibba G3 on continuous light but not on 9L:15D or 10L:14Dregimes. In L. paucicostata 381 nicotinic acid has a small effecton 12L:12D regime, a large effect on a 13L:11D regime and noeffect with daylengths longer than 14 hours, and in L. paucicostata151 nicotinic acid is only effective on daylengths shorter thanabout 11 hours. However, in L. paucicostata 151 and 381 treatmentwith both nicotinic acid and zeatin results in flowering undercontinuous light on half-strength Hutner's medium. Nicotinic acid is present in different Lemna but its concentrationdoes not appear to be influenced by changes in daylength. Thus,flowering clearly cannot be controlled by nicotinic acid actingalone, but the results of this study indicate that nicotinicacid could interact with other factors, possibly including oneor more of the known plant hormones, to influence the floweringprocess in Lemna. (Received August 28, 1985; Accepted October 29, 1985)     

REPRODUCTIVE CYCLES OF CERASTODERMA GLAUCUM(BRUGUIERE) AND C. EDULE (L.) WITH SPECIAL REFERENCE TO THE EFFECTS OF THE 1981-82 SEVERE WINTER

Gonadal changes in two species of Cerastoderma occurring indiscrete populations in South Wales were monitored by stereologicalanalysis during the breeding seasons of 1981 and 1982. Fecundityand spawning efficiencies were determined quantitatively. Therelationship between reproductive activity and changes in meatcondition are discussed. Both species are opportunistic breeders. Their normal patternsof reproduction are similar, consisting of minimum activityin winter and peak activity during spring/early summer. Thetwo species were affected differently by the severe winter of1981–82—C. glau-cum exhibited a single, ‘epidemic’spawning and resumed gametogenesis after a 4-month resting period.C. edule adopted a ‘polycyclic’ pattern withouta resting period. Both of these unusual reproductive strategies,augmented by reduced predation resulted in heavy spatfalls. (Received 20 March 1985; revised 20 March 1985;     

Seasonal migrations of the common Goby,Pomatoschistusmicrops (Kroyer), in Morecambe Bay and elsewhere

Summary Seasonal changes in abundance, and also reproduction, of the gobiid Pomatoschistus microps in intertidal pools on mussel beds at Morecambe, Lancashire, were studied from 1956 to 1961. During winter the shore was largely vacated by this species which returned for breeding purposes in spring. Spawning took place in upper shore pools from April to August. After a planktonic life of between 6–9 weeks, young fishes were recruited to the demersal population usually from June to September. A correlation between seasonal migrations and sea temperature is postulated. Geographical variation in occurrence and extent of migration in P. microps and the related sublittoral P. minutus is considered in relation to minimum winter sea temperatures over the southern Boreal and Baltic sea areas. Offshore winter migration has been found to take place in areas where such temperatures normally fall below 5° C, but not where minimum sea temperature is above 7° C. The effect of the severe winter of 1962–63 on certain populations of P. microps is described.     

Physiology and biosynthesis of lychnose in Cerastium arvense

The synthesis and accumulation of lychnose and isolychnose in leaves of Cerastium arvense during late fall and winter were shown to be controlled mainly by the temperature regime, while the photoperiodic regime had only a quantitative effect. Labelled lychnose and isolychnose were formed from [¹⁴C]raffinose in a cell-free enzyme preparation of leaves of Cerastium arvense in accordance with the equation: raffinose+raffinose (iso-)lychnose+sucrose.Dedicated to Professor Dr. Hubert Ziegler on the occasion of his 60th birthday     

Photoperiod differentially modulates photic and nonphotic phase response curves of hamsters

Circadian pacemakers respond to light pulses with phase adjustments that allow for daily synchronization to 24-h light-dark cycles. In Syrian hamsters, Mesocricetus auratus, light-induced phase shifts are larger after entrainment to short daylengths (e.g., 10 h light:14 h dark) vs. long daylengths (e.g., 14 h light:10 h dark). The present study assessed whether photoperiodic modulation of phase resetting magnitude extends to nonphotic perturbations of the circadian rhythm and, if so, whether the relationship parallels that of photic responses. Male Syrian hamsters, entrained for 31 days to either short or long daylengths, were transferred to novel wheel running cages for 2 h at times spanning the entire circadian cycle. Phase shifts induced by this stimulus varied with the circadian time of exposure, but the amplitude of the resulting phase response curve was not markedly influenced by photoperiod. Previously reported photoperiodic effects on photic phase resetting were verified under the current paradigm using 15-min light pulses. Photoperiodic modulation of phase resetting magnitude is input specific and may reflect alterations in the transmission of photic stimuli.     

Role of photoperiod and melatonin in seasonal acclimatization of the djungarian hamster,Phodopus sungorus

The Djungarian hamster,Phodopus sungorus, shows a clear annual cycle in some thermogenic parameters such as nonshivering thermogenesis (NST) and cold resistance. These seasonal changes were found to be basically controlled by natural changes in photoperiod. Further support for this view was obtained by exposing the hamsters to artificial long and short photoperiods.Implantation of melatonin during fall and winter results in an increased thermogenic capacity in both short and long day hamsters comparable to that shown by values of control hamsters exposed to short photoperiods during winter. This thermotropic action of melatonin and of short photoperiod could be found only in fall and winter whereas during spring and summer, melatonin, like photoperiod, had no influence on thermogenic capacities. These results show that the actions of melatonin and photoperiod vary with the season and that they depend upon the photoperiodic history of the hamsters. Our results further indicate that the pineal gland with its hormone melatonin is involved in mediation of photoperiodic control of seasonal acclimatization.