Egg Capsule Deposition Research Articles

Observations on the Mechanism of Egg-capsule Deposition in Melongena Corona (Mollusca: Gastropoda) Based on a Time-lapse Video

We present observations on the mechanism of egg-capsule deposition in Melongena corona (Mollusca: Gastropoda) based on a time-lapse video.

Observations of Cyclope neritea Linnaeus 1758 Breeding Behaviour in Artificial Habitat

Cyclope neritea Linnaeus 1758 is a popular Mediterranean Sea gastropod mollusk. A scavenger associated with shellfish farming, and used for population genetics studies and monitoring of environmental pollution. The aim is to evaluate C. neritea’s propagation under long-term artificial condition. C. neritea is maintained in 34 ppt substitute sea-water, along with copepods, Tigriopus californicus Baker 1912 at 25 oC and 12/12 hr light/dark cycle. It is an oviparous marine gastropod laying scattered single-egg-containing capsules. The females with retarded egg-capsule deposition eat the egg immediately after deposition. Normal capsules are not attacked. Juveniles supplement their diet with eggs of their kind regardless of the stage of development. Intra- and extra-capsular development and growth were observed. Its transient longevity reasons the work for optimising the conditions for the successful maintenance, and popularising it for the ornamental fish habitats.

Effects of Invasive Seaweed Depend on Underlying Physical Habitat Structure

Photo 1. A Green heron, Butorides virescens, forages on a mudflat covered with macroalgae. The dominant alga, Agarophyton vermiculophyllum, is visible as tufts of red-brown thalli and intermixed with Ulva spp., including Ulva lactuca. Photograph credit: Alice Besterman. Photo 2. Agarophyton vermiculophyllum forms mats up to 5 cm in depth above mudflat sediments, and generally between 2 and 3 cm deep. Here, a mat of Agarophyton has accumulated at the edge of a salt marsh, with some stems of Spartina alterniflora visible. The eastern mud snail, Tritia obsoleta (formerly Ilyanassa obsoleta), uses Agarophyton as refuge and substrate for egg-capsule deposition. Photograph credit: Alice Besterman. Photo 3. We used spotting scopes to observe shorebirds foraging across expansive mudflats exposed at low tide in the Virginia Coast Reserve LTER. We identified birds to the lowest taxonomic level, as well as the substrate they were used for foraging (bare mud, macroalgal mats, shallow water, oyster reefs, etc.). In this photograph, oyster (Crassostrea virginica) reef patches are visible in the foreground of the mudflat. Photograph credit: Alice Besterman. Photo 4. Hundreds of shorebirds including Limnodromus griseus (Short-billed dowitcher), Pluvialis squatarola (Black-bellied plover), and Calidris alpina (Dunlin) forage on a bare, topographically smooth mudflat in the Virginia Coast Reserve. Photograph credit: Alice Besterman. These photographs illustrate the article “Mudflat geomorphology determines invasive macroalgal effect on invertebrate prey and shorebird predators” by Alice F. Besterman and Michael L. Pace published in Ecology. https://doi.org/10.1002/ecy.3540.

Field Monitoring of Tritia mutabilis (Linnaeus, 1758) Egg Capsule Deposition and Intracapsular Embryonic Patterns Using Artificial Substrates and Machine Learning-Based Approaches

Tritia mutabilis (Linnaeus, 1758) represents a marine gastropod species of ecological and economical importance especially in coastal areas of the central Adriatic Sea (Italy). T. mutabilis encloses its fertilized eggs within capsules which play a protective role in the embryo defense against adverse environmental factors. Egg capsules are attached to any hard substrates and the availability of adequate substrates for oviposition represents therefore a major determinant of reproductive output of this species. The aim of the present study was to provide the first comprehensive monitoring of T. mutabilis egg capsule deposition and intracapsular embryonic patterns using specific artificial substrates and innovative analytical approaches. Square-based pyramid structures were placed within an area subjected to small-scale fishing activity along the Italian coastal waters of the central Adriatic Sea and monitored from March to June 2019. In addition, a machine learning-based approach was developed in order to speed up and automate time-consuming counting procedures of egg capsules attached on each pyramid. Overall, egg capsules were deposited on the almost totality of the artificial substrates reaching values of the surface coverage per site ranging from 31 to 97%. These findings lead to a quantitative estimation of egg number per site included between 27,060 and 62,940 capsules. Our results demonstrate that using these artificial substrates together with monitoring of both egg capsule deposition patterns and intracapsular developmental stages may be useful to improve the T. mutabilis stock management.

The life history and feeding ecology of velvet shell, Velutina velutina (Gastropoda: Velutinidae), a specialist predator of ascidians

Velvet shell, Velutina velutina (Müller, 1776), is a specialist predator of ascidians, like other members of the gastropod family Velutinidae. Globally, invasive ascidians have become problematic, ecologically and economically, yet ecological knowledge of velutinids remains limited. This study outlines the life history and feeding ecology of V. velutina in eastern Canada based on laboratory work complemented by field observations. The life history of V. velutina is closely linked with ascidians, which serve as prey and protection for their egg capsules. Egg capsules were embedded within tunics of Aplidium glabrum (Verrill, 1871) and Ascidia callosa Stimpson, 1852, with a preference for the latter. Seasonal behavioural shifts were consistent annually and corresponded with seawater temperature cycles. Feeding dominated during the coldest months (January–May), growth occurred as water temperature increased to the annual maximum (June and July), transitioning to mating during the warmest period (July–August), and egg capsule deposition dominated as water temperature declined (November–January). Larvae hatched between January and July after 2–4 months of development. Velutina velutina preyed on all ascidian species presented during this study, including golden star tunicate, Botryllus schlosseri (Pallas, 1766), and vase tunicate, Ciona intestinalis (Linnaeus, 1767), two non-indigenous species, although solitary species were preferred.

Life History, Knowledge, Bottlenecks, and Challenges for the Aquaculture of Concholepas concholepas (Gastropoda: Muricidae) in Chile

The carnivorous keystone muricid species Concholepas concholepas (Bruguiere, 1789) is known in Chile as “loco,” in Peru as “pata de burro, tolina, or chanque,” and in internationalmarkets as “false abalone.” The loco is present along the coast of Chile, in theArchipelago of Juan Fernandez and in southern and central Peru, and its range of distribution spans over 5,000 km of intertidal and shallow subtidal reefs. In Chile, the loco is a traditional food resource and has been heavily exploited since the early Holocene by intertidal food-gathers and free divers, and since the 1950s/60s by a small-scale artisan fleet of hookah-divers. In Chile, since the mid-1970s, the species has been mainly exported (foot-meat) to Asian markets, and between 1976 and 1980 market demands acted as a major driving force behind overexploitation of the loco. Since the 1990s, its fishery moved from an open access regime to a comanagement regulated policy based on territorial user rights for fisheries (TURF) and reproductive fishery bans. The loco, as an iconic species, played a key role in the implementation of TURF. In Peru, the loco fishery operates under a reproductive ban fishery regime and its export started in the late 1990s. In Chile, the loco is by far the most intensely studied of all exploited shellfishes in terms of evolution, paleobiogeography, biogeography, life history, behavior, physiology, ecology, genetics, and fishery. Moreover, the loco has been used as a biological model to study responses to global stressors such as ocean warming and acidification. During the past 20 y, several laboratory experimental attempts have been made to advance experimental, pilot, and commercial aquaculture of the loco. Nevertheless, the available information shows that no reliable and repeatable pilot or massive aquaculture protocols have yet succeeded. In this study, the extensive field and laboratory information for the most relevant life history phases of the loco, such as reproduction, mating, brood-stock holding, egg capsule deposition, larval posthatching, growing to competence, larval feeding, settlement and metamorphosis to juvenile stages, and pilot growing experiences to adult sizes are reviewed. In light of the available information, the most critical aquaculture bottlenecks are identified. Among them, the existence, from hatching to competence, of a long larval planktonic phase of about 3–4 mo, and the existence of cannibalism during postsettlement confined laboratory conditions are highlighted. Moreover, key aspects of the larval rearing of the loco, such as densities, field and laboratory food items, and temperatures are reported. The field collection of (1) competent larvae of locos in inshore coastal plankton; (2) new settlers from rocky shores; and (3) new settlers from fishery-discarded conspecific shells are also discussed. The collection of competent larvae was followed by laboratory induction to settlement and by two consecutive postsettlement rearing/growing phases (laboratory and field conditions) to overcome difficulties associated with the long larval phase and to speed up the time required to reach trading sizes. Furthermore, collection of new settlers was followed by rearing experiments under both laboratory and field conditions. The need of high demands of live prey (mainly mussels) during the laboratory rearing of the early benthic stages of loco is discussed, emphasizing that to implement ecologically sustainable aquaculture practices, parallel aquaculture of the appropriated prey is needed. A review of what is already known regarding the biology of C. concholepas is provided along with progress and pit-falls for the aquaculture of this species. The practicality for its aquaculture and the main challenges ahead are also discussed.

Predator-induced plasticity in egg capsule deposition in the mud snail Tritia obsoleta

Predator-induced plasticity in egg capsule deposition in the mud snail Tritia obsoleta

Sex and site-specific trends in veined rapa whelk (Rapana venosa) tributyltin bioaccumulation: considerations for biomonitoring

The imposition of male sexual characteristics onto the female (imposex) is present in wild populations of the non-native veined rapa whelk (Rapana venosa) in Chesapeake Bay, USA but does not appear to compromise reproductive function. Cultured whelks were used to test two hypotheses: (1) Observed imposex metrics will be similar to tributyltin (TBT) water concentrations at each of three sites; (2) Male and imposex/female whelks from the same site will have similar TBT body burdens. Cultured 2-year-old whelks were transplanted to three field sites in the York River, USA at the onset of their second reproductive season. Transplant site mean TBT water concentrations ranged from 1.4 ± 0.77 to 64.2 ± 57.8 ng l−1. Imposex incidence was 100% after 28 weeks with an observed M:F:IF ratio of 81:0:92 across all sites. Imposex stages (median vas deferens scale index = 4) and reproductive output were similar across sites. The imposex severity (IS = penis length/shell length) increased with increasing TBT concentrations. The relative penis length (RPLI) and relative penis size (RPSI) indices were positively related to site-specific TBT levels. Male whelks accumulated significantly higher TBT concentrations than female whelks at the site with the highest TBT concentration. Mean TBT concentrations in whelk egg capsules were significantly higher than concentrations in male or female whelk tissue. Egg capsule deposition provides a depuration mechanism for female whelks to reduce body burden of lipophilic TBT. Sex, season and reproductive status should be considered when using gastropod bioaccumulation to monitor TBT effects.

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.

Utilization of the invasive alga Gracilaria vermiculophylla (Ohmi) Papenfuss by the native mud snail Ilyanassa obsoleta (Say)

The recent invasions of the red alga, Gracilaria vermiculophylla, to the Atlantic and Eastern Pacific Oceans have the potential to significantly alter intertidal and subtidal soft sediment communities. In particular, G. vermiculophylla increases habitat complexity and provides a novel hard substrate in an otherwise two dimensional habitat. Following our observations that the native omnivorous mud snail Ilyanassa obsoleta utilizes G. vermiculophylla for egg capsule deposition, our field surveys demonstrated that the in situ abundance of egg capsules on G. vermiculophylla matched abundances on a native alga Ceramium virgatum and were at least 11–50 times greater than on all other co-occurring macrophytes. Additionally, through mesocosm experiments, we showed that I. obsoleta preferentially deposits eggs on the invasive G. vermiculophylla over native substrates. However, despite the thick layer of egg capsules found on G. vermiculophylla, no detrimental effects were seen on thalli growth. In contrast, growth of the native red alga Ceramium virgatum was significantly reduced when egg capsules were present, suggesting G. vermiculophylla can out-compete native macrophytes in areas of I. obsoleta abundance, while facilitating reproduction of the native mud snail. This novel interaction has the potential to significantly alter biological interactions in soft sediment communities through a variety of different mechanisms, including the alteration of trophic cascades via the increase in mud snail abundance. Furthermore, facilitation of the reproductive success of I. obsoleta may lead to increases in the occurrence of cercarial dermatitis, as I. obsoleta is a known intermediate host organism.

Gastropod egg capsules preserved on bivalve shells from the Lower Jurassic (Hettangian) of Poland

Fossil gastropod egg capsules have rarely been reported from the fossil record. This paper describes gastropod egg capsules preserved exclusively on cardiniid bivalves from Lower Jurassic (Hettangian) deltaic deposits of the Holy Cross Mountains area, central Poland. In most instances, only the bases of the egg capsules are preserved as dark outer rings with hollow cavities inside. Some specimens, however, are preserved as dark circular spots or even shallow depressions on the bivalve molds. The general occurrence, morphology, size and composition of the egg capsules as revealed by Energy Dispersive Spectroscopy (EDS) analyses and elemental mapping point to neritimorphs as the most probable producers. The egg capsules are composed primarily of organic matter with some calcium. Recent neritid gastropods possess aragonitic spherules within the egg capsule walls composed of conchiolin or chitin, which strengthen them and increase their chance of fossilization compared to egg capsules of other gastropods. Recent neritids lay their egg capsules on mollusk shells as well. The occurrence of Early Jurassic egg capsules only on redeposited cardiniid bivalve shells may suggest that the shells were the best medium for egg-capsule deposition. The occurrence of egg capsule bases together with dark circular spots, interpreted as compressed unhatched capsules, suggests that these egg capsules either hatched or were deposited at different times in the same place. The Early Jurassic egg capsules were preserved due to the strengthening role of the carbonate phase within the wall and rapid burial coupled with limited bioturbation in deltaic settings. The prodelta-delta front depositional environment, with high rates of sedimentation by rivers and sediment redistribution by wave and current action, was favorable for preserving these fossils.

Notes on oviposition and demography of a shallow water population of the edible snail Zidona dufresnei (Caenogastropoda: Volutidae) living in San Antonio Bay (northern Patagonia, Argentina)

Zidona dufresnei (Donovan, 1823) is a big-sized and long-lived snail endemic to the south-western Atlantic where it dwells in sandy bottoms between five and 115 m; females lay big egg capsules from which crawling juveniles emerge. An unusual population of Z. dufresnei inhabits the low intertidal and shallow subtidal zone of San Antonio Bay, the southernmost location of the species, where it faces many threats. The aim of this study is to describe some of the demographic and reproductive characteristics of this population and to compare them to those located in northern zones. Monthly samples of adults and egg capsules were obtained from October to April and their position was recorded; snails and capsules were gathered for examination in the laboratory. Sex-ratio was near 1:1 for the whole sampling period and the size–frequency distributions were similar for both sexes; females were wider and heavier than males at the same shell length. Maximum shell length was 120.5 mm in our study and so no female reached the minimum size at first gonadal maturity reported for other populations (128 mm); female size seems to limit the capsule diameter and the number and size of embryos that are lower than in other populations. Egg capsule and adult densities in the intertidal zone peaked in February and March respectively, averaging 1.34 capsules and 1.91 snails by 100 m2 during the sampling period; egg capsule deposition elapsed from November to March and peaked in December; females select cobble by size to lay egg capsules. Due to its restricted distribution and the low juvenile and adult dispersal, the unusual Z. dufresnei population dwelling in San Antonio Bay seems to be quite vulnerable to diverse anthropogenic impacts.

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.

Egg-capsule deposition and how behavioral interactions influence spawning rate in the squid Loligo opalescens in Monterey Bay, California

Recent evidence suggests that, contrary to what was believed previously, most Loligo spp. females spawn multiple times and do not die immediately following a single spawning event. The present study used sustained focal observations of male/female pairs of the opalescent inshore squid Loligo opalescens Berry to examine the structure and behavior of near-bottom spawning groups. The study was carried out in a small area (10 km2) of Monterey Bay, California (36°36.1′N; 121°53.4′W), at depths of 25–45 m, using video cameras mounted on remotely operated vehicles. Behavioral observations were made primarily during daylight hours over known spawning beds in April and November 2000, and August 2001. Squid formed large aggregations in the water column where pairing occurred. Most commonly, only small numbers of active spawners were found at the substrate depositing egg capsules, and the mean operational sex ratio in the spawning groups was 1.87 males:1 female (range=1.0–8.5), although the ratio fluctuated rapidly as roving lone males joined and departed from the small spawning groups. On average, females (n=40) deposited 2.67 capsules (range 2–7) per focal observation at an average interval of 8.47 min between depositions (n=67). Following deposition of the capsules, females broke away from their consort males and jetted upwards to rejoin large schools located many meters above the substrate. Egg-capsule deposition was often interrupted by lone males seeking a mate, or by the approach of predators including fish and marine mammals. The results suggest that most of the communal egg beds in southern Monterey Bay are built up slowly through daily intermittent spawning, not in large “big bang” reproductive events as often depicted for L. opalescens.

Responses of mud snails from low and high imposex sites to sex pheromones

Imposex, male secondary sexual characteristics in female snails, is a morphological indicator of sub-lethal exposure to organotin compounds. The relation between imposex and behavioral responses to sex pheromones was studied. Responses of snails to sex specific pheromones were determined in laboratory assays. Females and males from a low imposex site and females, imposex females and males from a high imposex site were tested. The snails from the low imposex site showed the expected strong behavioral dimorphism with females responding to male pheromone and males responding to female pheromone. In assays using snails from the high imposex site, female and imposex females showed no dimorphism in response to pheromones and males showed a relatively weak dimorphism. As there was no breeding or egg capsule deposition at the high imposex site, we conclude that even the morphologically normal snails were behaviorally and reproductively compromised.

Behavioral responses of sexually active mud snails: kariomones and pheromones.

We postulated that kariomones and pheromones function to organize egg capsule deposition and breeding aggregations of mud snails (Ilyanassa obsoleta). Sexually active male and female mud snails were exposed to water-born odors from juvenile snails, nonaggregated female snails, oysters, egg capsule depositing snails, sexually active males, sexually active females, and copulating snails and tested for a follow response using a ring assay. Neither sex responded to juvenile odor or to odor of sexually inactive females. Snails turned and followed water born odors from oysters, when tested with the odors of sexually active males, sexually active females, and copulating pairs, we found sex-specific differences in responses. Sexually active females followed the odor of sexually active males and ignored sexually active female odor. Sexually active males followed the odor of sexually active females and ignored sexually active male odor. Both sexes followed the odor of copulating pairs and egg capsule depositing snails. Snail activities in breeding aggregations are organized by at least three pheromones and one kariomone, and reflect the multifunctionality of the aggregations.

Chemical mediation of egg capsule deposition by mud snails.

Mud snails (Ilyanassa obsoleta = Nassarius obsoletus = Nassa obsoleta) deposit eggs in protective capsules on hard substrata in soft bottom environments. We studied sites of egg capsule deposition and snail movement responses to odors to determine if chemoreception plays a role in deposition site selection. From results of field surveys, laboratory experiments, and field experiments, we conclude that mud snails use chemoreception for capsule deposition. Attractive odors originate from mud snail and whelk egg capsules and from living bivalves. Evidence for attractive odors from conspecifics is equivocal. Capsules are deposited on living odor sources and nearby hard substrates. We hypothesize that deposition of capsules on living substrates increases the likelihood that embryos will survive by decreasing the chance of smothering of embryos by sediments.

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.

Development and ecological aspects of the echinospira shell ofLamellaria rhombicaDall (Prosobranchia; Mesogastropoda)

Abstract Aspects of the developmental biology of Lamellaria rhombica are presented, from egg capsule deposition through hatching, planktonic development, and metamorphosis. Attention is focused on the development and microstructure of the unique double shell in the veliger, and particularly on the buoyancy function of the outermost, “echinospira” shell in the free planktonic stage. Comparisons are drawn between this and other known echinospira larvae. The echinospira shell decreases the specific gravity of the veliger, yet is not positively buoyant itself. This, together with the increased surface area it presents, serves to decrease the sinking rate of the nonswimming veliger. By being neutrally buoyant, the echinospira shell does not interfere with the balance and orientation of the swimming larva.