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Egg Capsules (egg + capsule)

Distribution by Scientific Domains

Earth and Environmental Science	62%
Life Sciences	37%

Selected Abstracts

Size at maturity and egg capsules of the softnose skates Bathyraja brachyurops (Fowler, 1910) and Bathyraja macloviana (Norman, 1937) (Elasmobranchii: Rajidae) in the SW Atlantic (37°00,,39°30,S)

JOURNAL OF APPLIED ICHTHYOLOGY, Issue 2009
L. Paesch
Summary The softnose skates Bathyraja brachyurops and Bathyraja macloviana represent an important portion of the skate catches of the Uruguayan trawling fleet in the southwestern Atlantic. From March to October 2004, specimens of these species were collected at 75,200 m depth range in the area situated between latitudes 37°00,,39°30,S. For B. brachyurops, total length at which 50% of the specimens were retained by the gear was 68.0 cm for both sexes; TL50 was estimated at 65.4 cm for males and 67.0 cm for females. For B. macloviana, total length at which 50% of the specimens were retained was 56.0,57.0 cm for both sexes; TL50 was estimated at 53.5 cm for males and 52.0 cm for females. Egg capsule length varied from 79,91 mm in B. brachyurops and 69,75.5 mm in B. macloviana. In both species, capsules displayed striated surfaces and similar gross morphology, although egg capsules of B. macloviana had more robust anterior horns and a smaller size than those of B. brachyurops. Egg capsules of the latter also exhibited microscopical prickles. Capsule edges were laterally keeled with a groove along the keel, and a straight and transverse velum was present in the egg capsules of both species. [source]

Egg capsules of the dusky catshark Bythaelurus canescens (Carcharhiniformes, Scyliorhinidae) from the south-eastern Pacific Ocean

JOURNAL OF FISH BIOLOGY, Issue 4 2010
F. Concha
The external morphology of the egg capsule of Bythaelurus canescens and its fixation to the substratum are described. Bythaelurus canescens egg capsules are typically vase-shaped, dorso-ventrally flattened, pale yellow in colour when fresh and covered by 12,15 longitudinal ridges. The anterior border of the capsule is straight, whereas the posterior border is semicircular. Two horns bearing long, coiled tendrils arise from the anterior and posterior ends of the capsule. The presence of longitudinal ridges and long coiled tendrils at both anterior and posterior ends of the capsule readily distinguish these egg capsules from those of other chondrichthyans occurring in the south-east Pacific Ocean. [source]

Maternal size and age affect offspring sex ratio in the solitary egg parasitoid Anaphes nitens

ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2007
Serena Santolamazza-Carbone
Abstract In this study, the effects of maternal age, diet, and size on offspring sex ratio were investigated for the solitary egg parasitoid, Anaphes nitens Girault (Hymenoptera: Mymaridae), both outdoors, during the winter, and inside a climatic chamber under favourable constant conditions. During the winter of 2005,2006, each of seven groups containing 40 1-day-old females was mated and randomly distributed among two treatments: (treatment 1) a droplet of undiluted honey ad libitum + one fresh egg capsule of the snout beetle Gonipterus scutellatus Gyllenhal (Coleoptera: Curculionidae) as host; (treatment 2) drops of water + one fresh egg capsule of G. scutellatus. We recorded the lifetime fecundity, the daily sex allocation, and the lifetime offspring sex ratio to study the existence of a relationship with maternal characteristics. Moreover, we assessed the effect of location (outdoors vs. indoors) and group (groups are representative of early, mid, and late winter) on sex ratio. The most important factor that biased the sex ratio was maternal body size: larger females of both treatments produced more female offspring. As females of A. nitens could gain more advantage than males from body size, larger mothers have a higher fitness return if they produce more daughters. The effect of the treatment was significant: starved females produced more females. Location and group were not significant. Fecundity and sex ratio were age dependent. Old mothers that received honey (treatment 1) had fewer offspring and a more male-biased offspring sex ratio, probably due to reproductive senescence and sperm depletion. Starved females (treatment 2) experienced reproductive decline earlier, perhaps because they invested more energy in maintenance rather than in reproduction. [source]

Egg capsules of the dusky catshark Bythaelurus canescens (Carcharhiniformes, Scyliorhinidae) from the south-eastern Pacific Ocean

Functional morphology of embryonic development in the Port Jackson shark Heterodontus portusjacksoni (Meyer)

JOURNAL OF FISH BIOLOGY, Issue 4 2008
K. R. Rodda
The oviparous Port Jackson shark Heterodontus portusjacksoni embryo has a long incubation of 10,11 months during which it undergoes major morphological changes. Initially the egg capsule is sealed from the external environment by mucous plugs in either end of the capsule. Four months into incubation, the egg capsule opens to the surrounding sea water. Fifteen stages of development are defined for this species, the first 10 occur within the sealed capsule, the remaining five after capsule opening to hatching. The functional significance of major definitive characters such as circulation within the yolk membrane and embryo, rhythmic lateral movement of the embryo, external gill filaments, heart activity, internal yolk supplies, egg jelly and the significance of the opening of the egg capsule are described. The egg jelly in the sealed capsule functions to mechanically protect the embryo during early development, however, it eventually creates a hypoxic environment to the embryo as the available oxygen is used up. This generates several physiological challenges to the developing embryo. It is able to overcome these problems by morphological changes such as increasing the effective surface area for gaseous exchange with the development of external gill filaments, fins and extensive circulation in both the embryo and attached external yolk sac. These adaptations become limiting as the embryo grows and respiratory needs outweigh the available oxygen. At this time, the mucous plugs dissolve and the capsule becomes open to the external environment. [source]

Laboratory Study of the Intracapsular Development and Juvenile Growth of the Banded Murex, Hexaplex trunculus

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2010
Youssef Lahbib
Spawning, intracapsular development, and juvenile growth of Hexaplex trunculus were investigated in the laboratory. Each female deposited nightly an average of 138.83 ± 58.70 yellowish egg capsules per spawn. Each capsule contained 358.57 ± 102.45 eggs with an average diameter of 207.23 ± 18.18 µm. Observations on the intracapsular development showed that H. trunculus is a spiralian unequal-cleaving gastropod, with polar lobes being extruded at early segmentation. Embryos develop within the egg capsule through the provision of nurse eggs as an extraembryonic source of nutrition. Hatching occurred after 52 d of incubation. However, the hatchlings were not completely metamorphosed because velum was still present. At this moment, the average of shell length was 1.04 ± 0.13 mm (n = 107). The average number of hatchlings per capsule was 14.73 ± 4.40 including 3.4% malformed individuals. During the first 5 mo of life, juveniles rapidly grew in shell length (growth rate = 3.56 mm/mo). However, in the remaining period (26 mo), growth rhythm decreased considerably (growth rate = 0.64 mm/mo). The weight growth rhythm was irregular with alternation between fast and slow increases observed over the rearing experiment. This kind of data could be useful for assessing the potential of this species for future molluscan aquaculture programs. [source]

Fossilized embryos are widespread but the record is temporally and taxonomically biased

EVOLUTION AND DEVELOPMENT, Issue 2 2006
Philip C. J. Donoghue
SUMMARY We report new discoveries of embryos and egg capsules from the Lower Cambrian of Siberia, Middle Cambrian of Australia and Lower Ordovician of North America. Together with existing records, embryos have now been recorded from four of the seven continents. However, the new discoveries highlight secular and systematic biases in the fossil record of embryonic stages. The temporal window within which the embryos and egg capsules are found is of relatively short duration; it ends in the Early Ordovician and is roughly coincident with that of typical "Orsten"-type faunas. The reduced occurrence of such fossils has been attributed to reducing levels of phosphate in marine waters during the early Paleozoic, but may also be owing to the increasing depth of sediment mixing by infaunal metazoans. Furthermore, most records younger than the earliest Cambrian are of a single kind,large eggs and embryos of the priapulid-like scalidophoran Markuelia. We explore alternative explanations for the low taxonomic diversity of embryos recovered thus far, including sampling, size, anatomy, ecology, and environment, concluding that the preponderance of Markuelia embryos is due to its precocious development of cuticle at an embryonic stage, predisposing it to preservation through action as a substrate on which microbially mediated precipitation of authigenic calcium phosphate may occur. The fossil record of embryos may be limited to a late Neoproterozoic to early Ordovician snapshot that is subject to dramatic systematic bias. Together, these biases must be considered seriously in attempts to use the fossil record to arbitrate between hypotheses of developmental and life history evolution implicated in the origin of metazoan clades. [source]

Comparing fecundity in parthenogenetic versus sexual populations of the freshwater snail Campeloma limum: is there a two-fold cost of sex?

INVERTEBRATE BIOLOGY, Issue 1 2009
Lisa T. Crummett
Abstract. The predominance of sexuality in eukaryotes remains an evolutionary paradox, given the "two-fold cost of sex" also known as the "cost of males." [Correction added after online publication 29 January 2009: in the preceding sentence, extraneous words were deleted.] As it requires two sexual parents to reproduce and only one parthenogenetic parent, parthenogens should have twice the reproductive rate compared with their sexual counterparts and their genes should spread twice as fast, if all else is equal. Yet, parthenogenesis is relatively rare and considered an evolutionary dead-end, while sexuality is the dominant form of reproduction in multicellular eukaryotes. Many studies have explored short-term benefits of sex that could outweigh its two-fold cost, but few have compared fecundity between closely related sexuals and parthenogens to first verify that "all else is equal" reproductively. We compared six fecundity measures between sexual and parthenogenetic populations of the freshwater snail, Campeloma limum, during a brooding cycle (1 year) across two drainages. Drainages were analyzed separately because of a significant drainage effect. In the Savannah drainage, fecundity was not significantly different between sexuals and parthenogens, even though parthenogens had significantly more empty egg capsules per brood. In the Ogeechee drainage, parthenogens had significantly more egg capsules with multiple embryos and more hatched embryos than sexuals. Taken over 1 year, embryo size was not significantly different between parthenogens and sexuals in either drainage. Given these results and the close proximity of sexual and parthenogenetic populations, it is perplexing why parthenogenetic populations have not completely replaced sexual populations in C. limum. [source]

Life history of Littorina scutulata and L. plena, sibling gastropod species with planktotrophic larvae

INVERTEBRATE BIOLOGY, Issue 1 2002
Paul A. Hohenlohe
Abstract. The intertidal, sibling species Littorina scutulata and L. plena (Gastropoda, Proso-branchia) are sympatric throughout most of their ranges along the Pacific coast of North America. Both species release disc-shaped, planktonic egg capsules from which planktotrophic veliger larvae hatch. Here I review existing data and present new observations on these species' life history, including age at first reproduction, spawning season, maximum fecundity rates, capsule morphology, egg size and number, pre-hatching development, larval growth at three food concentrations, potential settlement cues, planktonic period, and protoconch size. Previous classification of egg capsule morphologies used to distinguish the species is inaccurate; instead, capsules can be categorized into three types of which each species may produce two. Females of L. scutulata produced capsules with either two rims of unequal diameter or one rim, while females of L. plena produced capsules with one rim or two rims of nearly equal diameter. Females of each species spawned sporadically from early spring to early fall in Puget Sound. Larvae of L. plena hatched one day earlier than those of L. scutulata, and both species grew fastest in the laboratory at intermediate food concentrations. Larvae metamorphosed in the presence of a variety of materials collected from their adult habitat, including conspecific adults, algae, rocks, and barnacle tests. This is the first report of planktotrophic larvae in this genus metamorphosing in the laboratory. The total planktonic period of 8 larvae of L. scutulata raised in the laboratory was 37,70 days, and a single larva of L. plena metamorphosed after 62 days. Protoconch diameter of shells collected from the field was 256,436 ,m and did not differ significantly between the species. Previous allozyme and mitochondrial DNA work has suggested high levels of genetic variability in both species and greater genetic population structure in L. plena, despite the long spawning season and long-lived larvae in both species. The interspecific life history differences described here appear insufficient to produce consistent differences in gene flow patterns. [source]

Size at maturity and egg capsules of the softnose skates Bathyraja brachyurops (Fowler, 1910) and Bathyraja macloviana (Norman, 1937) (Elasmobranchii: Rajidae) in the SW Atlantic (37°00,,39°30,S)

Rapid and convergent evolution of parental care in hydrobiid gastropods from New Zealand

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2005
M. HAASE
Abstract Although parental care occurs in most phyla encompassing a wide array of forms, little is known about its evolution in invertebrates. Two types of egg capsules have been known among ovoviviparous New Zealand hydrobiid gastropods, elastic capsules and simple membranes. Based on a phylogenetic analysis using two mtDNA sequence fragments, I asked whether the second state was derived from the first or whether brooding had multiple origins. The evolution of ovoviviparity was also investigated in the context of habitat transition between brackish and freshwater. Maximum parsimony and Markov chain models of character state transformations in a maximum likelihood framework suggested that hydrobiids have invaded freshwater three times independently. Two of these invasions were followed by the evolution of ovoviviparity, probably in adaptation to changing water levels during periods of irregular precipitation. The syntopy of two congeneric species, one oviparous and the other one brooding, indicated that the transition between reproductive modes must have occurred rapidly. [source]