Initiation Of Gametogenesis Research Articles

Gonad development and spawning of the Vulnerable commercial sea cucumber, Stichopus herrmanni, in the southern Great Barrier Reef

Despite the important ecological roles of commercial bêche-de-mer holothuroids in coral reef ecosystems their reproductive biology is poorly studied, including on the Great Barrier Reef (GBR). We investigated reproduction of Stichopus herrmanni, a commercially important species listed as Vulnerable, at One Tree Island, southern GBR. Gonad index, histology and spawning observations indicated an annual reproductive cycle with gamete release in the Austral spring and summer (November–February), as for populations of this species at a similar latitude in New Caledonia. Stichopus herrmanni releases gametes episodically, spawning multiple times during summer. Assimilation of spawning observations from OTI and elsewhere along the GBR and tropical Pacific revealed that gamete release by S. herrmanni is influenced by the lunar cycle, with spawning taking place around the new moon in summer. This species is an aggregative spawner with a behavioural change to attain elevated positions on the reef at dusk prior to spawning. After the spawning season, gametes remaining in the gonads are reabsorbed. Spent gonads completely lacked gametes. There was a quiescence in gonad development in winter with an absence of gonads in some specimens, indicating an aestivation-like period for reproduction. By late-winter (August) recovery stage gonads were distinguished by the initiation of gametogenesis, which coincided with increasing temperature and day length. Our findings contribute to the understanding of the reproductive biology of S. herrmanni, a consideration for future fisheries management in the protection of this Vulnerable species, especially with respect to the increasing global trade in bêche-de-mer.

Reproduction of the short-spined sea urchin Heliocidaris crassispina (Echinodermata: Echinoidea) in Hong Kong with a subtropical climate

Population density presumably serves as a negative feedback by modulating growth and reproduction. However, such density-dependent mechanisms have not been examined in most commercially exploited populations. In the present study, we evaluated how population density might affect the reproductive pattern of the commercially harvested sea urchin Heliocidaris crassispina at three sites with different densities in Hong Kong (Cape d’Aguilar, Sheung Sze Wan and Nine Pins). Monthly measurements of the gonad index and histological observations showed that the three populations exhibited a similar seasonal reproductive pattern, with the initiation of gametogenesis in winter (November) and maturation by late winter (March). Spawning took place over 8 months from March to October in Hong Kong, and lasted considerably longer than H. crassispina in more temperate regions. The gonad index was affected by density, with urchins in Cape d’Aguilar (the higher density site) having a lower mean value than those in the other two sites with lower densities. These results indicate that factors affecting density may influence reproductive output of H. crassispina, and such effect should be taken into account when considering the use of sea urchin refugia to enhance the stock.

Molecular characterization, tissue distribution of Follicle-Stimulating Hormone (FSH) beta subunit and effect of kisspeptin-10 on reproductive hormonal profile ofCatla catla(Hamilton, 1822)

Gonadotropin (GTH) hormones are glycoprotein which stimulates gonadal maturation in vertebrates. Follicle stimulating hormone is involved in initiation of gametogenesis and regulation of gonadal growth. FSHβ has been cloned and characterized from the brain of Catla catla. The FSHβ full-length of cDNA sequence of 523 bp comprised 3, 394 and 128 bp of 5′-UTR, open reading frame (ORF) 3′-UTR respectively. The coding region of C. catla FSHβ encoded a peptide of 130 amino acids. Phylogenetic analysis of C. catla FSHβ deduced amino acid sequence showed high similarity with Gobiocypris rarus followed by goldfish, Carassius auratus. The qPCR result shows that FSHβ mRNA is mainly expressed in pituitary while moderate and low expression was observed in testis and ovary respectively. Chitosan-nanoconjugated kisspeptin-10 (CK-10) of particle size 125 nm, polydispersity index of 0.335 to 0.65 and zeta potential of −34.95 mV were synthesized and evaluated at against naked kisspeptin-10 for their reproductive hormonal profile. Treatment of fish with CK-10 showed controlled and sustained surge of the reproductive hormones (FSH & LH) with peak at 12 h. The hormone levels of naked kisspeptin-10 treated fish decline after 6 h. The sustained release of this CK-10 will help in reducing maturation age, synchronization of ovulation and spawning in fish. This is the first report on use of chitosan-nanoconjugated kisspeptin-10 (CK-10) for reproduction in fish.

Reproductive cycle of Ensis magnus in the Ría de Pontevedra (NW Spain): Spatial variability and fisheries management implications

Mesoscale differences in the reproductive cycle of the commercial sword razor clam Ensis magnus (Schumacher, 1817) were studied in six shellfish beds in the Ría de Pontevedra (NW Spain) between March 2008 and July 2010. The GCI accurately described the reproductive cycle as indicated by the histological analysis. Both methods showed that the reproductive cycle was similar at different sites and was characterized by a resting stage during summer and early autumn, initiation of gametogenesis in autumn and a period of successive spawning interspersed with gonad recovery during winter and spring. However, a 15-day to one month delay in advanced stages of gametogenesis and maturation was observed between the inner and the outermost site of the ria, as well as an extended spawning period in the outermost area. Lower bottom seawater temperatures at the outermost sites appeared to delay maturation and to prolong the spawning periods, whereas salinity fluctuations at the innermost sites appeared to reduce the length of the cycle. This study provides the first estimation of the size at which E. magnus reaches sexual maturity in the Iberian Peninsula, determined in 79mm, and it is also the first work in determining the mesoscale variation in gonadal development of any species of the superfamily Solenoidea. The results highlight the importance of carrying out mesoscale studies of the reproductive biology in coastal fisheries resources. Some of the findings of the present study have already been applied in the rotation scheme of the fishery harvesting plan.

Aspects of reproduction of striped venus Chamelea gallina in the Gulf of Cádiz (SW Spain): Implications for fishery management

This study analyzes the main reproductive aspects of a natural population of Chamelea gallina on the SW Spanish coast (Gulf of Cadiz): gametogenic cycle, size at first maturity, size at sexual differentiation and partial fecundity. Methodology involved the use of standard histological techniques, image analysis and the assessment of the variation of gonadal growth.Monitoring throughout one year (May 2010–April 2011) identified 5 gametogenic developmental stages and evidenced the existence of a long reproductive period between March and September. In May 70% of individual were in stage 4, reproduction period (sub-stages 4A: maturity and 4B: partial emission), whereas in June most individuals were partially emitting gametes (4B). An important peak of gamete emission took place between June and July, after that recovery stages were detected (sub-stage 4C). In September most of individuals were in stage 5 (spent). It was not possible to define a single spawning event, but signs of partial spawning of greater or lesser intensity were identified throughout the whole reproduction period. This period was followed by a short period of sexual rest (stage 1; October), before beginning a new gametogenic cycle and of energy storage processes in November. Most of the individuals remained in a pre-active stage (stage 2: initiation of gametogenesis) until February, although advanced gametogenesis stages (stage 3) were also observed in January. The size (shell length) at first maturity was estimated for males (8.41mm), females (10.29mm) and the whole population (9.34mm) using standard histological techniques.For the range of shell lengths studied (20–30mm), between 40% and 60% of the visceral mass of C. gallina was devoted to reproduction. Gonadal volume was dependent on shell length and was between 37.25 and 205.95mm3. Gonadal volume and oocyte volume fraction were the most decisive factors in estimating fecundity. C. gallina is a multiple partial spawner and partial fecundity values were estimated and comprised between 76,835 and 797,424 oocytes per female. Partial fecundity was linearly related with both shell length and live weight. Since the oocyte output highly varies as shell length increases, reducing the minimum legal catch size (25mm) or overfishing legal size classes (>25mm) could diminish the total oocyte output and, consequently, affect the recruitment and the size structure of the population. Therefore, fishery management decisions must be taken carefully.

Reproductive strategy of the invasive cockle Fulvia fragilis in the Bay of Tunis (Tunisia)

This study is the first work on the reproductive biology of lessepsian bivalve Fulvia fragilis. Monthly and bimonthly samplings were made in the period from April 2006 to October 2007, at the Bay of Tunis (northern Tunisia). From histological preparations of gonad, a gametogenic scale was drawn up based on eight stages: sexual rest; initiation of gametogenesis; advanced gametogenesis; ripe; partial spawning; advanced spawning; restoration; and spent. After examination of gonad preparations, F. fragilis appeared to be a simultaneous hermaphrodite species. Spawning was continuous all along the year, scarce in winter and with peaks during the rest of the year. The spawning peaks were positively correlated with the rise of the sea surface temperature and the nutrient availability. Furthermore, the presence of oocytes surrounded by spermatozoa in female and male follicles and in male gonoducts was observed. Self-fertilization may occur in this species. High summer mortalities probably due to the combination of vulnerability of the bivalve in response to the reproductive effort and high temperature stress were recorded. The F. fragilis reproduction strategy explains the success of its installation on the Tunisian coast.

Broodstock Conditioning in the Basket Cockle, Clinocardium nuttallii

Factors affecting broodstock conditioning in the hermaphroditic basket cockle, Clinocardium nuttallii, were examined in laboratory experiments. Although a 13-wk experiment conducted at 16°C failed to bring C. nuttallii broodstock into spawning condition under different dietary treatments, initiation of gametogenesis was apparent for those broodstock maintained at 2.5°C. Condition indices were significantly greater when broodstock were fed a combination of Isochrysis galbana (Tahitian strain, T-iso) and Chaetoceros gracilis (CG) or T-iso and Thallasiosira pseudonana (3H) than when fed a combination of Tetraselmis suecica (TS) and 3H or TS and CG, indicating that T-iso may be a better food source than TS for cockle broodstock conditioning.

Neuroendocrine disruption in Mya arenaria clams during gametogenesis at sites under pollution stress

This study examined the neuroendocrine status of clams on intertidal mud flats in the St. Lawrence Estuary and Saguenay Fjord areas during late gametogenesis. The impact of pollution was determined by a test battery of early stress markers (metallothioneins, heme levels, glutathione S-transferase activity), tissue damage (lipid peroxidation and DNA damage) and morphologic characteristics (age, soft-tissue weight ratio and growth index). Neuroendocrinal status was examined by tracking serotonin and dopamine metabolism, monoamine adenylate cyclase activity in synaptosomes, monoamine oxidase and arachidonate cyclooxygenase activities in relation to gametogenetic activity: pyrimidine synthesis, (aspartate transcarbamoylase activity or ATC), vitellogenin-like proteins and gonado-somatic index. The results show that clam soft tissue weights were reduced at sites close to harbours and higher at sites near domestic wastewater outfalls. The age-to-length ratio of clams was generally higher at impacted sites, suggesting reduced growth. The biomarkers of stress or damage confirmed that oxidative stress, DNA damage, metallothioneins and glutathione S-transferase activity were significantly increased at varying degrees, at the polluted sites. Vitellogenin-like proteins and gametogenetic activity were significantly increased at sites influenced by domestic wastewaters. Furthermore, the clams were still in active gametogenesis and not ready for spawning, as indicated by the concordance of the serotonin/dopamine ratio with vitellogenin-like proteins and pyrimidine synthesis. However, gonadal cyclooxygenase activity was increased at polluted sites and significantly correlated with most of the stress biomarkers, suggesting that the clams were in a state of inflammation rather than at the spawning stage. Finally, a multivariate analysis revealed that the sites were readily discriminated with high efficiency (>71%) and that both neuroendocrine physiological markers and stress responses were identified as the major components, thus explaining the global physiological response of the clams. We conclude that the effects of pollution compromise the clams' health status and that the initiation of gametogenesis in environments contaminated by municipal wastewaters or harbours contributes to the toxic effects of pollution.

Gametogenic periodicity in the chemosynthetic cold-seep mussel “Bathymodiolus” childressi

The gametogenic periodicity of the cold seep mussel “Bathymodiolus” childressi was analysed from a time series of samples from depths of ∼ 650 m surrounding the Brine Pool cold seep on the continental slope of the northern Gulf of Mexico. Occasional samples were retrieved from Bush Hill and GC 234 for comparison. At the Brine Pool, both females and males showed strong reproductive periodicity with the initiation of gametogenesis from December to March, followed by a period of gamete growth or proliferation and spawning from October to February. Gametogenesis was synchronized at all three sites. Gametogenic periodicity appears to be correlated with surface production that peaks during the winter months. Downward flux of detritus during this period may provide food for the planktotrophic larvae and also supplementary nutrition for the adult, which has chemosynthetic bacterial symbionts but is also capable of filter feeding. Individuals in all three populations carried parasites and these were especially common at Bush Hill and GC234, where it is suggested they have a major impact on reproductive output.

A new approach to kelp mariculture in Chile: production of free-floating sporophyte seedlings from gametophyte cultures of Lessonia trabeculata and Macrocystis pyrifera

Substantial amounts of Macrocystis and Lessonia are traditionally harvested and exported from Chile as raw material for alginate. Because of intense mari culture of abalone (Haliotis ssp.), herbivorous mol luscs that feed on brown kelps, pressure on local populations of Macrocystis and Lessonia has in creased to critical levels within the past 5 years, strongly supporting eiorts to produce algae maricul tured biomass. Here, we present our results on the de velopment of new techniques for large scale kelp mariculture in Chile. We have abandoned the tradi tional technique of direct spore seeding onto inocula tion lines. Instead, we used gametophyte cultures that were manipulated to enter gametogenesis and to produce synchronous batches of 10 4 10 5 embryos. Juvenile sporophytes were cultured under perma nent aeration and agitation, £oating unattached in contamination free glass bottles up to 10 L, plexiglass cylinders and 800 L greenhouse tanks. When hold fast initials were formed at a size of 8 cm, the sporo phytes were spliced into Nylon rope fragments and transferred to the sea. Twelve months after initiation of gametogenesis in the laboratory, Macrocystis pyrifera attained14 m length and 80 kg fresh weight m � 1 line in the sea. For Lessonia trabeculata 6m onths after gametogenesis initiation, 0.25 kg fresh weight m � 1 was attained in the sea.

Temperature and photoperiod drive Crassostrea gigas reproductive internal clock

This study examined the gametogenic cycle of Crassostrea gigas in controlled conditions over one year, with a focus on the initiation of gametogenesis. This work analysed also the role of temperature and photoperiod in the regulation of oyster reproduction. Broodstock were maintained in natural (NC), accelerated (AC) and perpetual winter (WC) conditions of temperature and photoperiod, with feeding ad libitum. Qualitative and quantitative analyses of the reproductive pattern were performed using biometric measurement approach, sex ratio determination, histology and a gonad filling index. Each experimental treatment led to different strategies for growth and resource allocation. The gametogenic cycle, appeared entirely modulated, accelerated or delayed, by coupled temperature/photoperiod parameters. Temperature played a key role in gonial mitosis regulation. Gonia proliferation was set off and sustained by winter temperature (8–11 °C) whatever the physiological state of oysters. Maturation of germ cells appeared to be a function of temperature and could proceed at low temperature, while ripe oysters were obtained at 8 °C in winter conditioning. The three conditioning methods used in this study, allowed the production of gametes throughout the year, including in the autumnal resting period. Moreover, stocks of ripe oysters could be maintained at low temperature during several months to produce spat when desired for aquaculture production.

Seasonal variation in the gametogenic ecology of the Antarctic scallop Adamussium colbecki

Quasi-monthly samples of the Antarctic pectinid bivalve Adamussium colbecki were examined to determine the gametogenic pattern and periodicity. Both female and male gametogenic patterns show a very distinct seasonal development, with the initiation of gametogenesis in October and spawning in late September and early October of the following year. The duration of the gametogenic cycle is unusually short for Antarctic benthos, being 12 months. Reproductive effort (ratio of gonad mass to total tissue mass) is significantly higher in males than females, and males are ready to spawn earlier in the austral winter than females. The digestive gland also shows a strong seasonal cycle but develops earlier than the gonad. We propose that energy from the spring bloom is stored in the digestive gland before being transferred to the gonads. Gonad size, digestive-gland size and, to a lesser extent, adductor-muscle size, are related to adult size in most samples. The length of the gametogenic cycle suggests that reproduction in A. colbecki is more pectinid than Antarctic.

Molecular characterization of sea bass gonadotropin subunits (α, FSHβ, and LHβ) and their expression during the reproductive cycle

Reproduction is controlled by two pituitary gonadotropin hormones, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). This study reports the cloning, sequence analysis, and gene expression of gonadotropin (GTH) subunits from the European sea bass ( Dicentrarchus labrax). The GTH subunits were cloned from a sea bass brain–pituitary cDNA library. The nucleotide sequences of the common α, the FSHβ, and the LHβ subunit cDNAs were 625, 521, and 591 base pair (bp) long, respectively, encoding for mature peptides of 94, 105, and 115 amino acids (aa), respectively. Sequence analysis showed that sea bass FSHβ is more similar to higher vertebrate FSHβ’s (35–37%) than to LHβ’s (26–30%), whereas sea bass LHβ is more similar to LHβ’s (40–53%) than to FSHβ’s (26–41%). Phylogenetic analysis of fish GTH sequences grouped the β subunits into two groups, FSH and LH, distributed into four classes, corresponding to the accepted divisions of Elopomorphs, Ostariophysis, Salmonids, and Percomorphs. A dot-blot technique was developed to analyze GTH pituitary mRNA levels during the reproductive cycle of male sea bass. From October (initiation of gametogenesis) to February (spermiation), the expression of all three subunits in the pituitary increased in parallel, concomitantly with the gonadosomatic index (GSI) and the accumulation of LH protein in the pituitary, all values declining sharply at post-spermiation. This study demonstrates that the pituitary of sea bass contains two gonadotropin hormones and that both gonadotropins are probably involved in the control of gametogenesis, gamete maturation, and spermiation.

Reproduction of the sea urchin Evechinus chloroticus (Echinodermata: Echinoidea) in a New Zealand fiord

The reproductive cycle of Evechinus chloroticus (Val.) was examined at three (outer, mid, and inner) sites in Doubtful Sound, Fiordland over a 3‐year period. We found that sea urchins from all three populations had an annual gametogenic cycle, the timing of which was temporally and spatially consistent. Inter‐individual variation in the gametogenic cycle was noted within each population, however, initiation of gametogenesis was generally synchronous among males and females and among sites, occurring in May/June. Strong asynchrony in gamete maturation was observed in Deep Cove, occurring in males 4–5 months earlier than females. Spawning occurred in December at the inner and mid fiord sites, while occurring in January at the outer fiord site. Reproductive potential (maximum gonad index) and output (weight of gametes released/g of animal/year) varied spatially and temporally, where there was a consistent decreasing trend in reproductive potential and output with increasing distance away from the fiord entrance. Spatial variation in reproductive output may be associated, in part, with the strong ecological gradient found in Doubtful Sound, where there is a reported decrease in macrophyte biomass and cover towards the fiord headwaters. The implications of spatial differences in gonad production with respect to the population biology and fisheries management of E. chloroticus in the fiords are discussed.

Reproductive biology of the intertidal sea cucumber Actinopyga mauritiana in the Solomon Islands

Over a four year period, gonad index, examination of gonad tubules, and histology were used to study the reproduction in the sea cucumber Actinopyga mauritiana. This species reproduced annually during the warmer months of the year in Solomon Islands. This annual reproductive cycle progressed through five maturity stages: recovery, growing, mature, partly-spawned and spent. The recovery stage (March–May) was marked by initiation of gametogenesis and coincided with decreasing day length. The growing stage (June–September) was characterized by development of gametes through to the mature stage (October–December). Spawning occurred October through December and coincided with increased water temperature and day length. Spent gonads (January–March) contained a few unspawned gametes or completely lacked gametes. Although A. mauritiana had annual reproduction, individuals lacking or having indeterminate gonads were present year-round. Macroscopic examination of gonad tubules after biopsy provides a practical tool for assessing maturity condition of broodstock in the field during the reproductive season.

Cloning of cDNA encoding vitellogenin and its expression in red sea urchin, Pseudocentrotus depressus

Both male and female red sea urchins, Pseudocentrotus depressus, accumulate a large quantity of the major yolk protein (MYP) in the nutritive phagocytes of immature gonads before the initiation of game-togenesis. To examine the accumulation mechanism of this protein in the gonad, we cloned full-length cDNA encoding vitellogenin (Vg; the MYP precursor in the coelomic fluid), and investigated its expression in various tissues of immature adults. The nucleotide sequence of Vg contains an open reading frame of 4050 bp encoding 1349 amino acids. The deduced amino acid sequence near the N-terminal showed 25% homology to the vertebrate transferrin family. Vitellogenin mRNA was detected in the ovary, testis, stomach, intestine and rectum by Northern blot analysis, with the highest level of mRNA expression in the gonad. Weak expression was also detected in the esophagus and coelomocytes by RT-PCR. In situ hybridization demonstrated that nutritive phagocytes, which exclusively fill the lumina of the immature gonad, contained Vg mRNA. These results suggested that the MYP stored in the immature gonads is synthesized and accumulated mainly within the nutritive phagocytes.

Reproductive variability over a four-year period in the sea urchin Evechinus chloroticus (Echinoidea: Echinodermata) from differing habitats in New Zealand

The endemic New Zealand echinoid, Evechinus chloroticus (Valenciennes), was sampled approximately monthly from September 1990 to October 1994 at three sites in Tory Channel, Marlborough Sounds, New Zealand. These channel sites (outer, mid and inner) were up to 20 km from the open ocean and differed in their shore type, exposure to wave action and macrophyte abundance. E. chloroticus showed an annual reproductive cycle at each site, with gametogenesis commencing in the late austral winter and spawning in summer. Maximum gonad indices (reproductive potential) varied spatially, with the outer site generally having higher maximum gonad indices than the inner site, and temporally, with maximum gonad indices occurring earlier in 3 of the 4 seasons at the outer site than the inner site. The mid and inner sites showed much greater variation in maximum gonad indices (range 15.83 to 26.99% and 11.87 to 20.90%, respectively) than the outer site (range 19.31 to 22.95%). Reproductive output (weight of gametes released per gram echinoid) also varied, with the different sites showing significantly different outputs in the different years. A regression of maximum reproductive potential against reproductive output was significant ( p < 0.001), and had a positive slope with an r 2 of 0.79. While, the initiation of gametogenesis was relatively synchronous between sites and years, and is possibly cued by increasing daylength, it progressed at different rates among populations. Spawning did show spatial and temporal variability, occurring near the time of highest sea-surface temperatures (∼15 °C). The observed variations in reproductive cycle may be related to small-scale variability in diet and environmental conditions. Furthermore, asynchronous spawning, variable spawning duration, and variable reproductive output are likely to strongly influence annual recruitment variability in E. chloroticus, with different larval subpopulations contributing unequally in different years. The ecological consequences of this, both for the ability of E. chloroticus to propagate itself in space and time and for the management of the developing E. chloroticus fishery in New Zealand, are discussed.

Mucus as a mediator of gametogenic synchrony in the sea cucumber Cucumaria frondosa (Holothuroidea: Echinodermata)

The data presented here demonstrate that the sea cucumber Cucumaria frondosa secretes a biologically active mucus that helps maintain gametogenic synchrony among conspecifics. Either a whole mature individual or a sample of its freshly collected mucus was able to initiate gametogenesis in conspecifics that were in the gametogenic recovery stage when other environmental conditions, including daylength, were maintained constant. Similar results were obtained when the mucus was kept in seawater for less than 3 h prior to its use, whereas after 6 h in seawater, the mucus had lost its inducing properties. Laboratory experiments showed that the mucus was produced in lesser amount during late summer and autumn; the production rapidly increased in early January to reach a peak a few months before the June spawning, in 1992 and 1993. The increment of mucus production was concurrent with the initiation of gametogenesis. Synthesis of mucus was maximal in individuals having attained gametogenic maturity and minimum in individuals with less developed gonads. At first relatively stable in seawater, the mucus gradually lost its integrity within a period of 3–5 h, suggesting that the mucus may be carried over long distances by currents, thus allowing a transfer of information before its complete degradation. This phenomenon was observed in the field where streams of mucus could be followed by SCUBA divers as far as 20–30 m away from the secreting animal. The data presented here are the first evidence of the important role played by mucus secretion during the gametogenic processes of an echinoderm.

Immunocytochemical localization of testis ecdysiotropin in the pupa of the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae).

Antiserum against testis ecdysiotropin isolated from the gypsy moth, Lymantria dispar, reacted with neurons in the protocerebrum, optic and antennal lobes, subesophageal, thoracic and abdominal ganglia, as well as in nerve tracts extending through the optic lobes, tritocerebrum, and interganglionic connectives of the pupal stage of these insects. Testis ecdysiotropin is a peptide required by immature moths to initiate production of testes ecdysteroid, which is necessary for the development of the male reproductive system and initiation of spermatogenesis. Antiserum against testis ecdysiotropin also detected an accumulation of testis ecdysiotripic-like material between the inner and outer testis sheaths of pupae. The localization of this peptide in the imaginal disks of the last larval stage, cells and nerve fibers in the optic and antennal lobes of the pupa of both sexes, as well as in the testes during development of the adult reproductive system indicates that testis ecdysiotropin has a much larger impact on adult metamorphosis than development of the reproductive system and initiation of gametogenesis. Although this peptide may have a modulatory role in the central nervous system (CNS), it may also initiate a cascade of activity required for the development of the adult nervous system, in addition to its role in reproduction.

Dissection of the Blue-Light-Dependent Signal-Transduction Pathway Involved in Gametic Differentiation of Chlamydomonas reinhardtii.

Gametogenesis of the green alga Chlamydomonas reinhardtii may be viewed as a two-step process that is controlled by the environmental cues of nitrogen deprivation and blue light. Initiation of gametogenesis is induced by nitrogen deprivation, resulting in mating-incompetent pregametes, when cells are kept in the dark. For the completion of gametic differentiation light is required. Pregametes were treated with pharmacological compounds to influence the light-dependent conversion to mature gametes. Dibutyryl-cyclic 3[prime]5[prime] adenosinemonophosphate, papaverine, and genistein were found to inhibit the progression of gametogenesis in the light. Treatment of pregametes in the dark with either staurosporine or papaverine resulted in their conversion to mature gametes. Apparently, papaverine has different effects in the dark and in the light; the effect of staurosporine suggested that a protein kinase C-like component inhibits the conversion of pregametes to gametes, a block that normally is relieved by illumination. This hypothesis was corroborated by the observation that activators of protein kinase C, N-heptyl-5-chloro-1-naphthalenesulfonamide, N- (6-phenylhexyl)-5-chloro-1-naphthalenesulfonamide, and the phorbolester phorbol-12-myristate 13-acetate inhibited gametogenesis in the light. Genistein and dibutyryl-cyclic 3[prime]5[prime] adenosinemonophosphate were able to inhibit the dark activation caused by staurosporine treatment, suggesting that their targets work downstream from the "protein kinase C-like" kinase. Surprisingly, staurosporine and papaverine worked synergystically on the activation of pregametes in the dark.