Egg Capsule Production Research Articles

Microplastics Affect Rates of Locomotion and Reproduction via Dietary Uptake in Globally Invasive Snail Physa acuta

Given the omnipresence and potential of entering the food web, the recently emerged pollutant microplastics (MPs) has become a global threat. The impacts of MPs in marine ecosystems are well documented, but the freshwater environment is relatively understudied. Improper disposal of industrial and commercial waste introduces MPs in the freshwater environment where it is either transported to the ocean or eventually settles down to the bottom. To elicit the impacts on components of fitness, the effect of inert particles on the reproductive and behavioral performance on organisms can only be translated after long-term experiments, but most of the available information on freshwater benthos relies only on short-term experiments. This study investigated the rates of microplastic ingestion, locomotion and reproduction in the globally invasive snail Physa acuta (Gastropoda, Pulmonata) at six environmental concentrations (0, 2.5, 5, 10, 20 and 40 mg/200 mL) of polystyrene (PS) MPs particle (size = 32–63µm) for 93 days after maturity. The PS particle ingestion was confirmed by analysis of P. acuta excreta and tissue digestion. P. acuta displayed Type II functional response to MPs. We measured locomotion speed and reproductive rate for 93 days after maturation at 20, 30 and 40 mg/200 mL concentrations of PS MPs equivalent to 500 × 104, 750 × 104 and 1000 × 104 particles/200 mL, respectively. Average locomotion speed and egg capsule production were significantly lower in the MP applied environment than in the control. The percent reduction in ovisac production and egg hatching success were a direct function of MP concentrations in the medium., although, in a natural setup, plastic debris was observed as a frequent oviposition substrate for P. acuta favoring the species in dispersal. The present results point to a higher tolerance of P. acuta to MPs and their role as a vehicle of MP transfer from sediment to fish.

Identification of novel yolk ferritins unique to planarians: planarians supply aluminum rather than iron to vitellaria in egg capsules.

All animals, other than Platyhelminthes, produce eggs containing yolk, referred to as "entolecithal" eggs. However, only Neoophora, in the phylum Platyhelminthes, produce "ectolecithal" eggs (egg capsules), in which yolk is stored in the vitelline cells surrounding oocytes. Vitelline cells are derived from vitellaria (yolk glands). Vitellaria are important reproductive organs that may be studied to elucidate unique mechanisms that have been evolutionarily conserved within Platyhelminthes. Currently, only limited molecular level information is available on vitellaria. The current study identified major vitellaria-specific proteins in a freshwater planarian, Dugesia ryukyuensis, using peptide mass fingerprinting (PMF) and expression analyses. Amino acid sequence analysis and orthology analysis via OrthoFinder ver.2.3.8 indicated that the identified major vitellaria-specific novel yolk ferritins were conserved in planarians (Tricladida). Because ferritins play an important role in Fe (iron) storage, we examined the metal elements contained in vitellaria and ectolecithal eggs, using non-heme iron histochemistry, elemental analysis based on inductively coupled plasma mass spectrometry and transmission electron microscopy- energy-dispersive X-ray spectroscopy analysis. Interestingly, vitellaria and egg capsules contained large amounts of aluminum (Al), but not Fe. The knockdown of the yolk ferritin genes caused a decrease in the volume of egg capsules, abnormality in juveniles, and increase in Al content in vitellaria. Yolk ferritins of D. ryukyuensis may regulate Al concentration in vitellaria via their pooling function of Al and protect the egg capsule production and normal embryogenesis from Al toxicity.

Histomorphological and endocrine assessment of female Arabian carpetshark, Chiloscyllium arabicum (Elasmobranchii: Hemiscylliidae) from the Persian Gulf during annual reproductive cycle.

The present study aimed at assessing the annual reproductive cycle of female Arabian carpetshark, Chiloscyllium arabicum from the Persian Gulf by a macroscopic and microscopic evaluation of the reproductive tract. The annual cycle of gonadal steroids [17β-estradiol (E2), progesterone (P4) and testosterone (T)] was also assessed in this shark. In total, 130 female C. arabicum were collected from the Bahrakan Creek (located northwest of the Persian Gulf) between January 2018 and March 2019. Females were oviparous with an external-type ovary and only one functional ovary. Five sexual maturity stages were recognized based on macroscopic and microscopic evaluation: Immature I (August-October), Immature II (November-January), Mature (February-March), Pregnant (April-May) and Spent (June-July). The structural changes in the oviducts, oviducal glands and uterus throughout the annual reproductive cycle were consistent with their roles in the egg movement, the egg capsule production and sperm storage. The plasma levels of the gonadal steroids were associated with morphological changes in the reproductive tract. E2 showed two detectable peaks during March (close to ovulation) and June (just before mating). P4 and T displayed a peak just before ovulation.

Germline Defects Caused by Smed-boule RNA-Interference Reveal That Egg Capsule Deposition Occurs Independently of Fertilization, Ovulation, Mating, or the Presence of Gametes in Planarian Flatworms.

Few animals are known to lay eggs in the absence of ovulation or copulation, as it is presumably energetically wasteful and subjected to negative selection. Characterization of Smed-boule, a member of the DAZ family of germline RNA-binding proteins, revealed that egg capsule (or capsule) production and deposition occurs independently of the presence of gametes in the planarian flatworm Schmidtea mediterranea. Reduction of Smed-boule expression by RNA-interference (RNAi) causes ablation of spermatogonial stem cells and the inability of ovarian germline stem cells to undergo oogenesis. Although animals subjected to Smed-boule RNAi lose their gametes and become sterile, they continue to lay egg capsules. Production of sterile capsules is even observed in virgin Smed-boule(RNAi) and control planarians maintained in complete isolation, demonstrating that egg production in S. mediterranea occurs independently of ovulation, fertilization, or mating. Evidence suggests that this is a conserved feature amongst Platyhelminthes, and therefore relevant to the pathology and dissemination of parasitic flatworms. These findings demonstrate that Smed-boule functions at different stages during male and female germline stem cell development, and also demonstrate that egg capsule production by planarian flatworms occurs independently of signals produced by mating or ova.

Parental size and environmental conditions affect egg capsule production by Nassarius reticulatus (Linnaeus 1758) (Gastropoda: Nassariidae)

In shallow coastal habitats scavenging netted whelks Nassarius reticulatus attached egg capsules to the stipes of red algae Chondrus crispus and occasionally on Furcellaria lumbricalis and Plumaria plumose. In the laboratory egg capsules were laid on aquaria sides and lids by individuals ≥ 21 mm shell length. Larger size classes produced more egg capsules and spawned over a longer period and in doing so partitioned less energy into shell growth. Large netted whelks (25–28.9 mm) produced larger capsules which contained significantly more and larger eggs than those produced by smaller individuals (21–24.9 mm). Egg capsule production continued throughout the year by regularly fed N. reticulatus held at ambient seawater temperatures. Egg production increased in the spring and summer with peak production during June (15 °C), decreased between August and October and resumed again during the winter (November to February at ∼ 7 °C). During the summer (15–16 °C) egg capsules were smaller and contained smaller eggs than those deposited during the winter (7–10 °C), although the number of eggs · capsule − 1 was similar. Enforced food limitation reduced the number and size of the egg capsules, the number and size of eggs produced · female − 1 and the duration of the breeding period. Hatching success of N. reticulatus egg capsules was high (95%) even at winter seawater temperatures (11–8.5 °C) and the duration of embryonic development was fastest between 15 and 17.5 °C.

Influence of environmental factors and female size on reproductive output in an invasive temperate marine gastropod Rapana venosa (Muricidae)

Life history and reproductive strategies influence population dynamics at the inter- and intra-specific level. Environmental conditions suitable for gonad development and spawning, the reproductive range, may be a smaller portion of the broader species distribution. The only known breeding population of veined rapa whelks (Rapana venosa) in North America is in Chesapeake Bay, USA. There is considerable interest in the potential reproductive range of this non-indigenous species given the rapa whelk’s negative impacts on commercial shellfish species in both its native and introduced ranges. Weight-specific reproductive output is described for wild caught Chesapeake Bay rapa whelks maintained in flow-through mesocosms for 2 years. Measured reproductive output within and between egg capsule deposition seasons (years) in relation to water temperature, salinity, daylength, and female size is used to describe the rapa whelk’s reproductive range. Egg capsule production is influenced by seasonal and absolute water temperatures as well as seasonal daylength cycles. Egg capsule deposition by Chesapeake Bay rapa whelks begins at water temperatures of approximately 18°C and continues for 11–15 weeks. Forty to 70% of female whelks deposited egg capsules in most weeks during this season, producing 150–200 egg capsules female−1 week−1. Water temperatures >28°C caused reduced egg capsule production relative to temperatures of 20–25°C. Egg capsule production was positively related to seasonal changes in daylength, and two peaks of egg capsule deposition were observed in the 2001 and 2002 deposition seasons. The combination of declining daylength and higher water temperatures in late summer was associated with the cessation of egg capsule deposition. A lower average weight specific reproductive output in 130–145 mm SL rapa whelks (average 12 ± 1%) than in 90–106 mm SL rapa whelks (average 22 ± 1% of body weight) may reflect a life history that balances the physiological costs of maintaining a large body mass with the production of many planktonic larvae from multiple clutches of egg capsules per breeding season over a 10–15-year lifespan. Estimates of the cumulative day-degree requirements corresponding to the annual initiation of egg capsule deposition were 238 and 236 for 2001 and 2002, respectively. Reproductive output and day-degree requirements for Chesapeake Bay rapa whelks were similar to values calculated from previous studies of native muricids (Eupleura caudata and Urosalpinx cinerea). A latitudinal range of 30–41° (N and S) is predicted as the realized reproductive range for rapa whelk populations on the basis of the day-degree requirements for native whelks and reproductively active invasive rapa whelk populations.

On the reproduction and growth of some endemic gastropods of Lake Baikal

Reproduction and ontogeny of some Baikalian gastropods inhabiting the littoral were studied. To detect phases of enhanced hatching, growth and production of fresh egg capsules, SCUBA divers lifted stones from the littoral of the western shore of Lake Baikal and from River Angara monthly. All egg capsules and gastropods were recorded. Four different developmental phases of embryos were distinguished. In March the percentage of egg capsules with fully developed embryos is very high, but in April–June the percentage rapidly decreases due to enhanced hatching and a high production of newly laid capsules. From June to October the proportion of older developmental stages increases again. Freshly laid capsules were found at any time, but in March–April, the percentage is low while it is high from May to July. Embryogenesis does not take a few weeks as in most Palaearctic species but several months. Although embryos were found fully developed in autumn–winter, most hatching occurs in spring. In order to determine growth rate and time to maturity for different endemic gastropods, juveniles were kept in rearing cages in situ. The cages were lifted monthly and the snails measured. Results showed growth is very low from November to May and maximal in the period August to October. Thus, shell growth is not steady but cyclical. Compared with relatived species inhabiting smaller Palaearctic water bodies, the ontogeny of Baikalian gastropods is prolonged. It appears that in Lake Baikal Megalovalvata needs 2 years and Choanomphalus 2–3 years to become mature, while the Baicaliidae need at least 4 years to mature and 5 years to be fully grown. Growth rates are higher in the Angara River than in the Lake Baikal littoral.

Reproductive ecology and evolution in the invasive terrestrial planarian Bipalium adventitium across North America

Summary Comparisons between invasive species and their relatives can help in identifying traits that facilitate dispersal and colonization, and comparisons among populations within invasive species may highlight the roles of plasticity and evolutionary adaptation. Bipalium adventitium Hyman 1943 is an exotic, earthworm-eating soil flatworm that has become widespread and abundant in North America. As a first step in better understanding the ecology and evolution of this invasive planarian, we studied its reproductive traits in populations across its extensive geographic range and conducted an experiment on the effects of food availability. Colonization by B. adventitium is facilitated by hermaphroditism, sperm storage, and tough egg capsules containing multiple offspring, traits present in most Terricola. The egg capsules produced by B. adventitium were large (22.5 mg), hatched in 7–37 days (mean=23 days), contained 1–8 offspring (mean=3.4), and represented about 21% of a parent's predeposition mass. Many individuals produced multiple egg capsules. Although considerable intraspecific variation was detected for most reproductive parameters, significant differences among geographic populations were noted for egg capsule mass, mean offspring mass, and measures of total reproductive output. Intraspecific correlations between parent mass and the masses of egg capsules and offspring, and the results of our experiment showing that food availability affected egg capsule production, together suggest that thus far intra-population variation and plasticity have been more important than local evolutionary adaptation in the invasion of this species.

Long‐term effects of prey‐availability, partnering and temperature on overall egg capsule output of ‘New Zealand flatworms’,Arthurdendyus triangulates

SummaryArthurdendyus triangulatusis an invasive terrestrial flatworm that preys on earthworms. To assessA. triangulatusegg capsule production, flatworms were maintained in ventilated polypropylene tubs (7.5 L) kept in controlled environment (CE) chambers or outdoors in the ground. Controlled environment chambers were maintained at 8°C or 14°C, flatworms kept singly or paired within tubs and offeredEisenia fetidaaccording to a weight equalling one‐eighth or one‐half of the mean flatworm weight, or left unfed. The tubs were a successful method for keeping flatworms, with some surviving for over one year. The greatest number of egg capsules produced by an individualA. triangulatuswas nine over a 16 week period for a flatworm kept at 14°C and fed at the one‐half regime (0.56 egg capsules flatworm‐1week‐1). Although the effects of treatments varied with CE chambers, there was some evidence from flatworms kept outdoors, that feeding affected egg capsule output, with those flatworms fed at the one‐half regime tending to produce more egg capsules (P= 0.057). Flatworms at the one‐eighth regime or that were unfed produced progressively lighter egg capsules and substantially declined in weight themselves. Nevertheless, even unfed flatworms continued to produce egg capsules for 18 weeks. The lightest egg capsule weighed 8 mg, whilst the heaviest was 180 mg. In the CE chambers at 14°C, there was evidence for two different reproductive/survival strategies. Some flatworms produced cumulatively more egg capsules the longer they survived, whereas others lived longer but produced fewer egg capsules. Flatworms kept without a partner still produced egg capsules up to 35 weeks later. Egg capsules contained a mean of 4.14 (CE chambers) or 4.62 (outdoors) juveniles, with a maximum of 11. Overall, juveniles were 45% of the weight of egg capsules, although larger egg capsules had more juveniles, which comprised a greater proportion of the egg capsule. The conversion of earthworm prey to egg capsule production was estimated at 13%.

Long-term study of growth in the New Zealand flatworm Arthurdendyus triangulatus under laboratory conditions

Summary In a 1-year laboratory study of the New Zealand flatworm Arthurdendyus triangulatus, individual growth, degrowth and regrowth were manipulated via the feeding regime, with the compost worm Eisenia fetida as prey. A mean growth rate of 25 mg live weight wk—1 was evident, individual rates ranging between 18 and 38 mg wk−1. Degrowth was associated with egg capsule deposition for which the maximum rate was 0.5 capsules wk−1. The more egg capsules produced, the greater the adult weight loss, degrowth rates ranging from 8 to 55 mg wk−1. Change in flatworm body weight (gain/loss) also correlated with the length of the food introduction interval, though weight could be maintained for circa 2 weeks. Weight loss was not simply a function of hunger, voluntary cessation of feeding (possibly related to egg capsule production) being a confounding factor. During the growth phase, individual predation rate ranged from 0.9 to 1.1 earthworms wk−1, rate of tissue consumption ranging from 346 to 485 mg wk−1. Conversion efficiencies of earthworm to flatworm tissue were estimated to range between 3.8% and 10.7%. The impact of this exotic planarian on earthworm populations is discussed.

Survey of imposex in dogwhelks (Nucella lapillus) from North Sea coasts

Following a North Sea Task Force (NSTF) initiative in 1991, and funding from the Department of Environment (DOE), The Scottish Office Agriculture, Environment and Fisheries Department Marine Laboratory (SOAEFD), Aberdeen, was awarded a contract to assess the impact of tributyltin compounds in dogwhelks in all North Sea coastal waters. These waters were surveyed in 1991 and 1992 to evaluate the distribution and effects of tributylin (TBT) compounds on the common dogwhelk, Nucella lapillus. Wild and, where necessary, transplanted dogwhelks were analysed for imposex. Historical records indicate that Nucella lapillus was once present, on suitable substrates, around the whole of the North Sea coastline. Wild dogwhelks could be collected in all countries except Belgium and Germany, where the species is present only on Helgoland (in numbers too small to be sampled). All wild populations of dogwhelks showed imposex. Near sites of intense boating activity, all populations examined contained some sterile females. At all sites where transplants were recovered, the dogwhelks were affected by TBT. Prolonged survival of dogwhelks at any of these sites would not be expected, except perhaps at Torsminde in Denmark. All sites studied were categorized with reference to their potential for the maintenance of self-sustaining Nucella populations. All sites in the southern part of the North Sea (i.e. the coastlines of Belgium, The Netherlands, Germany and southern Denmark) were placed in Category C (reduced egg capsule production) or D (adult females expected to be sterile). In Norway, sites near large harbours had only sterile females in the population (Category D), whilst those further from harbours probably had reduced egg capsule production (Category C). In Sweden, all wild sites were affected but probably had no reduction in egg capsule production (Category B). In France and the UK, sites near large harbours or areas of small-boat activity probably had reduced egg capsule production (Category C). Sites further from sources of TBT contamination probably do not have reduced egg capsule production ( Category B). One site on the north east coast of Scotland shows effects consistent with an area distant from a source of TBT pollution (Category A). Copyright © 1999 Crown Copyright

Reproductive Biology of the Gregarious Mediterranean Vermetid GastropodDendropoma Petraeum

The reproductive biology of the gregarious Mediterranean vermetid gastropodDendropoma petraeum(Mollusca: Gastropoda) has been studied in the south-eastern coast of Spain. It apparently is a gonochorisric species with the sex ratio biased toward females (71%). A broad peak of more intense reproductive activity occurs in spring months and an inactive reproductive period during winter. The gonad of the males develops about two months before those of females, and storage of sperm by females has been observed. Internal fertilization takes place after the capture of pelagic spermatophores.The egg capsules lie free within the female mantle cavity, and females brood up to 86 capsules simultaneously (the highest number reported for any vermetid gastropod). The size of the capsules is somewhat variable and increases slightly from those containing first stages of development (mean = 678×579 μm) to those containing late stages (mean = 996×693 μm). Each egg capsule usually contains a single large egg or embryo, but sometimes two (8.2% of the capsules) or rarely three (0.24%). Production of egg capsules by females seems to be continuous throughout the reproductive period (from March to October).The unsegmented eggs measure from 440 to 507 μm in diameter (mean = 482) and are the largest reported for any vermetid gastropod. Nurse eggs are not present, and therefore most of the intracapsular nutrition comes from the internal yolk of the embryo.Development is lecithotrophic without a pelagic larval phase. The late intracapsular veliger stage metamorphoses within the capsule and hatching occurs at a crawling juvenile stage.

Life cycle of the earthworm predator Artioposthia triangulata (Dendy) in Northern Ireland

The terrestrial planarian Artioposthia triangulata was sampled weekly for 4 y using shelter traps. Numbers of trapped and individual planarian weights were recorded. On each sampling occasion, planarians were allocated to one of four size categories on the basis of their weight. These data are presented and the life cycle in Northern Ireland is deduced. Planarian growth occurs during the autumn-spring period and coincides with earthworm (prey) availability. Weight loss in the early summer is associated with egg capsule production. These capsules take over 2 months to hatch, so that recruitment into the population occurs in late summer.

ヒメエゾボラにおける同化量の季節変化

Seasonal changes in the assimilation energy of Neptunea arthritica in Usu Bay, Hokkaido were examined. In adults, energy directed to growth was largest in summer, and energy accumulated as reproductive output was largest in autumn. The assimilation energy levels that sustained metabolism during those periods were considerably higher than during winter and spring. The assimilation energy levels in immature individuals showed less variation than in adults.Net growth efficiency exhibited a convex curve with a peak (49.4%) at 2 years old. In both males and females, the proportion of assimilation energy utilized for reproductive output increased with age. The proportion of investment in females was 3 to 6 times that of males, owing to the production of egg capsules. The production efficiency of adults remained relatively constant at 35 to 40%, except for 5 years male, which showed 25.0%.

Egg-laying Season and Monthly Change in Egg Capsule Production of Clithon retropictus (Prosobranchia : Neritidae) in the Naka River of Izu Peninsula

Egg-laying Season and Monthly Change in Egg Capsule Production of Clithon retropictus (Prosobranchia : Neritidae) in the Naka River of Izu Peninsula

Toxicity of pesticides toAllobophora caliginosa(Oligochaeta : Lumbricidae)

Abstract Juvenile (4-week-old) earthworms reared in a laboratory were kept individually for 7 days in soil treated with several concentrations of various pesticides. Mortality and weight change were recorded. The relative toxicity of each pesticide - i.e., the cOlicentration (mg/kg of dry soil) of pesticide causing zero growth - compared with the standard, carbofuran (0.10), was aldicarb (0.09), phorate (0.30), aldoxycarb (0.40), methomyl (0.54), ox amyl (0.59), isazophos (0.93), fenamifos (5.72), fensulfothion (7.35), diazinon (12.4), copper (106), and citowett (525). Field trial data from 33 published reports show similar relative toxicity results. The toxicity of carbofuran to Lumbricus rubellus and Allobophora caliginosa was similar. Decreasing concentrations of carbofuran caused mortality, suppression of growth, and suppression of egg capsule production in mature (clitellate) A. caliginosa collected from the field. The concentrations of carbofuran safe to juvenile and clitellate A. caliginosa were similar. Use of a single batch of natural soil, an artificial soil, or the silica powder and glass bead media used in one of the proposed EEC tests could reduce variation between tests. The latter media would provide the most standardised conditions for a toxicity test. Juvenile A. caliginosa which are easily reared would be a more appropriate species for the EEC test than Eisenia fetida.

Growth rate as a measure of food value in thaidid gastropods: Assumptions and implications for prey morphology and distribution

Rates of body growth were measured for three species of rocky intertidal gastropods: Thais (or Nucella) lamellosa (Gmelin), T. (or N.) canaliculata (Duclos), and T. (or N.) emarginata (Deshayes). Three size classes of each predator species were grown experimentally in cages at two tidal heights on four size classes of each prey species: Semibalanus cariosus (Pallas), Balanus glandula Darwin, and Mytilus edulis L. Growth was also assessed for Thais canaliculata feeding on Mytilus californianus Conrad, and Thais emarginata feeding on Chthamalus dalli Pilsbry. Rates of body growth varied as a function of predator size, prey size and prey species. With one exception (large Thais canaliculata) intermediate sized Balanus glandula promoted the most rapid growth for all sizes of all three species of Thais; thus these potentially competing predator species have the same highest ranked prey. Among prey promoting slower growth, those encountered commonly in the normal habitats of the predator promoted more rapid growth than those encountered rarely, suggesting that past evolutionary experience has influenced present food value (= growth potential) of prey. For some predators, the ranking of prey species changed with predator size; Chthamalus dalli and similar sized Balanus glandula promoted comparable growth in small Thais emarginata but Chthamalus dalli promoted much slower growth than similar sized Balanus glandula in larger Thais emarginata. Rank differences based on prey size in Balanus glandula became more pronounced and in some instances changed with increasing predator size; larger B. glandula promoted relatively faster growth for large snails than for small snails in all Thais species. Finally, growth rates were correlated with two important attributes of fitness in T. canaliculata and T. emarginata; in general, prey promoting more rapid growth also resulted in an earlier age of first reproduction for initially immature snails and higher rate of egg capsule production for mature individuals. Thus, these growth rates provide a basis from which to examine quantitatively patterns of prey selection from an energy- or growth-maximization perspective. These patterns of predator growth also permit inferences about the possible influence of predation on the evolution of prey morphology, life-history, and microhabitat distribution. Size refuges from Thais predation were confirmed for both Semibalanus cariosus and Mytilus californianus. Both Balanus glandula and Mytilus edulis, on the other hand, were vulnerable to predation by all sizes of Thais examined (> 10 mm) regardless of prey size; thus, neither of these species achieves a size refuge. In addition, on rocky shores, vertical distributions of the prey species reflect general preference patterns of their predators: higher value prey species, i.e. those with less well developed defensive morphologies ( Balanus glandula, Mytilus edulis), generally occur higher on the shore. This pattern would be expected if preferred prey are consumed first lower on the shore where they are more available.

STUDIES ON THE ROLE OF THE LATERAL LOBES AND THE OVOTESTIS OF THE PULMONATE SNAILBULINUS TRUNCATUSIN THE CONTROL OF BODY GROWTH AND REPRODUCTION

The small lateral lobes (LL) are paired ganglia connected with the lateral side of the cerebral ganglia. Extirpation and implantation experiments demonstrate that (neuroendocrine) centres in the LL decrease body growth and increae the production of eggs and egg capsules. Castration is followed by an acceleration of body growth and a reduction of egg capsule production. Since reimplanted ovotestes (OT) degenerated rapidly, it could not be established whether this effect is hormonal or neuronal. The results clearly suggest that the OT is not involved in the endocrine control of cellular differentiation, growth and synthetic activity of the female accessory sex organs. The ways in which LL and OT may control the antagonistic processes of body growth and reproduction are discussed.

The reproductive physiology of the intertidal prosobranch Thais lamellosa (Gmelin). II. Seasonal changes in biochemical composition.

1. Seasonal changes in protein, lipid and polysaccharide level and content were studied in several body components of Thais lamellosa. Male soft body components consisted of the visceral mass, including the testis-digestive gland and remaining visceral mass, and the foot. Female soft body components consisted of the visceral mass, including the ovary-digestive gland, capsule-albumin gland, and remaining visceral mass, and the foot. 2. Seasonal changes in protein, lipid and polysaccharide content in body components, except the foot, were predominantly due to changes in indexes and not biochemical level. The foot was not important as a depot for any of the biochemical constituents. Protein was the dominant constituent in the visceral mass, lipid was intermediate in level and content and polysaccharide level and content were lowest. 3. The gonad-digestive gland complex was a lipid depot for both sexes. No other body component of either sex served as a lipid depot. 4. The ovary-digestive gland lipid content was at its maximum value in September but the capsule-albumin gland protein content did not reach its maximum value until December when it was 2.3 times the September value. The accessory reproductive tract reaches its maximum size just prior to capsule deposition. 5. The ratio of protein:lipid:polysaccharide content lost from the female visceral mass during aggregation was 18.3:2.3:1.0. Protein loss was split evenly between female catabolism and egg capsule production. Lipid loss went entirely to egg capsule production. Polysaccharide loss was split between female catabolism and egg capsule production. 6. Individuals interested in the efficiency of alternate reproductive strategies must consider the costs of aggregation and capsule wall deposition to species utilizing this type of strategy. Energetic costs of aggregation, starvation and production of encapsulated embryos are just as high as costs involved in broadcast fertilization among molluscs.

The storage and structure of proteins used in the production of egg capsules by the mollusc Cominella maculosa

Neogastropod prosobranch molluses produce species-specific egg-capsules. Two proteins, different at least structurally, are used in the production of these capsules by most species. The storage of these two proteins in the egg-capsule glands of the species Cominella maculosa was investigated in an attempt to discover whether both proteins were produced and stored separately or whether only one basic molecule was produced and stored in the gland to be subsequently used to form the two different protein structures present in the egg-capsules; ribbons and filaments. The two proteins were found to be produced and stored separately, but in very similar membrane-bounded granules or spherules. One of the proteins was found to be stored in the gland in a different structural form to that eventually used in the production of the egg-capsules.