scholarly journals Microscopic structure of the egg capsule of Atlantoraja cyclophora (Elasmobranchii: Rajidae: Arhynchobatinae)

2005 ◽  
Vol 5 (2) ◽  
pp. 305-308 ◽  
Author(s):  
María Cristina Oddone
Keyword(s):  
South America ◽  
Transverse Section ◽  
Microscopic Structure ◽  
Capsule Wall ◽  
Atlantic Region ◽  
Egg Capsules ◽  
Naked Eye ◽  
Egg Case ◽  
Egg Capsule

The microscopic structure of the egg capsules of Atlantoraja cyclophora, a species endemic to the Atlantic region of South America, is presented in this paper. In a transverse section, the dorsal face of the egg case is 70mu in width, and is subdivided into four layers. Ventrally, the egg capsule wall is 60 mu wide and composed of three layers. Both faces are covered by prickles which render the egg capsule surface striated to the naked eye.

Changes in macromolecular organization in collagen assemblies during secretion in the nidamental gland and formation of the egg capsule wall in the dogfish Scyliorhinus canicula

1993 ◽  
Vol 341 (1298) ◽  
pp. 419-436 ◽  
Keyword(s):  
Endoplasmic Reticulum ◽  
Liquid Crystalline ◽  
Secretory Granules ◽  
Capsule Wall ◽  
Micellar Phase ◽  
Scyliorhinus Canicula ◽  
Smectic A ◽  
Nidamental Gland ◽  
Collagen Molecules ◽  
Egg Capsule

The thickest layer (L 2 ) of the egg capsule wall of the dogfish, Scyliorhinus Canicula , is constructed largely from highly ordered collagen fibrils (Knight & Hunt 1976). This collagen is stored and secreted by the nidamental gland and passes through an extraordinary series of ordered phases, m any of which have well defined liquid crystalline structure. We have examined the changes in macromolecular packing of the collagen as it moves from the cisternae of the endoplasmic reticulum to secretory granules, is secreted and then formed into the egg capsule wall. Within the endoplasmic reticulum cisternae the collagen appears anisotropic but becomes assembled into a smectic A or lamellar phase in the Golgi cisternae. This phase persists in early secretory granules, where it is found in conjunction with a micellar phase. As these granules mature, the collagen passes through a cholesteric mesophase before adopting a columnar hexagonal arrangement. On merocrine secretion the granules’ contents revert rapidly to the smectic A-lamellar and micellar phases. As it passes along the nidamental gland tubules, the collagen is first converted into a second distinct micellar phase before assembling into the final fibrils that constitute the egg capsule. These phase transitions give powerful insights into the way in which the macromolecular arrangement of collagen molecules can be modulated and are discussed in the context of a range of other related structural transitions in collagens.

Egg-capsule Proteins of Selachians and Trout

1955 ◽  
Vol s3-96 (36) ◽  
pp. 483-488
Author(s):  
C. H. BROWN
Keyword(s):  
Egg Capsules ◽  
Histochemical Methods ◽  
Physical Chemical ◽  
Cuticular Proteins ◽  
Chemical Behaviour ◽  
Egg Capsule

1. The material of the egg-capsules of selachians and the chorion of trout eggs has been examined by physical, chemical, and histochemical methods. 2. The material of the egg-capsule of selachians has been found to be a quinonetanned protein. 3. The chorion of trout eggs is not quinone-tanned but its formation and chemical behaviour allies it with the invertebrate cuticular proteins rather than with the vertebrate keratins.

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)

2009 ◽  
Vol 89 (6) ◽  
pp. 1209-1214 ◽  
Author(s):  
Patricio Javier Pereyra ◽  
Maite Andrea Narvarte ◽  
Pablo Rafael Martín
Keyword(s):  
Shell Length ◽  
San Antonio ◽  
Anthropogenic Impacts ◽  
Sampling Period ◽  
Minimum Size ◽  
Subtidal Zone ◽  
Female Size ◽  
Western Atlantic ◽  
Egg Capsules ◽  
Egg Capsule

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.

Effects of hypoxia on egg capsule conductance inAmbystoma(Class Amphibia, Order Caudata)

2001 ◽  
Vol 204 (21) ◽  
pp. 3747-3753
Author(s):  
Nathan E. Mills ◽  
M. Christopher Barnhart ◽  
R. D. Semlitsch
Keyword(s):  
Surface Area ◽  
Oxygen Limitation ◽  
Effective Surface Area ◽  
Effective Surface ◽  
Egg Capsules ◽  
Hypoxic Conditions ◽  
Ambystoma Annulatum ◽  
Oxygen Conductance ◽  
Salamander Species ◽  
Egg Capsule

SUMMARYAquatic amphibian eggs frequently encounter hypoxic conditions that have the potential to limit oxygen uptake and thereby slow embryonic development and hatching. Oxygen limitation might be avoided if egg capsule surface area and oxygen conductance increased in response to hypoxia. We investigated this possibility in two salamander species, Ambystoma annulatum and Ambystoma talpoideum. The effective surface area of egg capsules increased in response to hypoxia, which increased the conductance for oxygen and enhanced oxygen transport. The ability of amphibian eggs to adjust their conductance in response to oxygen availability may increase survival in hypoxic environments.

Embryonic development and protein content of the embryos and intracapsular liquid of Melongena melongena (Caenogastropoda: Melongenidae)

2009 ◽  
Vol 90 (2) ◽  
pp. 347-351 ◽  
Author(s):  
Nicida Noriega ◽  
Patricia Miloslavich
Keyword(s):  
Embryonic Development ◽  
Protein Content ◽  
Shell Length ◽  
Protein Concentration ◽  
Food Source ◽  
Stages Of Development ◽  
Egg Capsules ◽  
One Stage ◽  
Egg Capsule

Eggs of Melongena melongena develop inside round, flat egg capsules which contain a gelatinous intracapsular fluid. To determine if this gel represents a nutritional source for the developing embryos, we measured the amount of proteins of the embryos throughout their development from the egg to the hatching stage as well as the protein content of the intracapsular liquid at the same stages of development. Egg capsules of M. melongena were collected at Golfete de Cuare, Venezuela between 1–2 m depth. Uncleaved eggs measured 352–480 μm and contained 8–15 μg of protein/egg. This amount of protein was not significantly different at the trochophore, veliger and pediveliger stages, however, it decreased significantly at the hatching stage to 6 μg/hatchling. About 95–98% of the eggs develop to the hatching stage, the remaining 2–5% remain intact in the egg capsule. Hatching takes place as a pediveliger measuring around 720 μm in shell length. The protein concentration of the intracapsular liquid was 0.18 μg/μl at the egg stage and it reached 0.13 μg/μl at the prehatching stage; however, the total amount of protein in the intracapsular fluid was not significantly different throughout the development from one stage to another. Results indicate that embryos of M. melongena use neither the intracapsular liquid as an extraembryonic food source, nor nurse eggs.

Imposex and organotin compounds in marine gastropods and sediments from the Mar del Plata coast, Argentina

2006 ◽  
Vol 86 (4) ◽  
pp. 751-755 ◽  
Author(s):  
Maximiliano Cledón ◽  
Norbert Theobald ◽  
Wolfgang Gerwinski ◽  
Pablo E. Penchaszadeh
Keyword(s):  
Digestive Gland ◽  
Dry Weight ◽  
Sediment Concentration ◽  
Capsule Wall ◽  
Marine Gastropods ◽  
Egg Capsules ◽  
Size Index ◽  
Penis Size ◽  
Contamination Event ◽  
Butyltin Compounds

The occurrence of imposex in Adelomelon brasiliana during two consecutive years near to Mar del Plata (the principal fishery port of Argentina) and its relation to tributyltin (TBT) and dibutyltin (DBT) content in muscle tissue and digestive gland was investigated using gas chromatography. Percentage of imposex affected females increased to over 80% in spring and summer of both years. However, its intensity, given by the relative penis size index (RPSI), fluctuated around low values. Adelomelon brasiliana digestive gland samples showed a very low concentration of TBT (36–46 ng/g dry weight). Egg capsules presented normal viable embryos, which had TBT concentrations similar to the capsule wall (15 ng/g) while the intracapsular liquid was only 2 ng/g, similar to the sediment concentration. The proportion and distribution of butyltin compounds (BTs) in sediments indicate a major contamination event.

Larval and early post-larval development of the protobranch bivalve Solemya velum (Mollusca: Bivalvia)

1992 ◽  
Vol 72 (2) ◽  
pp. 383-402 ◽  
Author(s):  
R.G. Gustafson ◽  
R.A. Lutz
Keyword(s):  
Shell Morphology ◽  
Marine Bivalve ◽  
North West ◽  
Larval Stages ◽  
Egg Capsules ◽  
The North ◽  
New Information ◽  
Solemya Velum ◽  
Ciliary Tuft ◽  
Egg Capsule

Early development in the north-west Atlantic awning clam, Solemya velum (Solemyoida: Solemyidae) was examined by light and scanning electron microscopy. Embryonic and pericalymma larval stages, typical of protobranch bivalves, developed within individual adhesive gelatinous egg capsules and offspring emerged at hatching as benthic crawl-away juveniles. Fertilized eggs were light orange in colour, spherical, and had a yolk-mass diameter of approximately 190 μm. Entirely ciliated cylindrical pericalymma larvae, with a length and width of 318 μm and 208 μn, respectively, were obtained within 24 h. These larvae lacked an apical ciliary tuft, possessed nine rows of calymma cells, and actively rotated within the egg capsule. During metamorphosis, which occurred within 48 h of fertilization, the transitory larval ectoderm was entirely ingested. The prodissoconch measured roughly 320 μm in length by 215 μm in height. The foot and ciliated gill buds were well developed by four days after fertilization and subsequent growth contributed to the dissoconch or adult shell. Hatching began at 13 d after fertilization when the shell measured approximately 402 μm in length by 251 μm in height. Actively crawling and burrowing juveniles were cultured for six months after fertilization and an ontogenetic sequence of encapsulated and juvenile shell morphology was obtained for identification purposes. Current contradictory hypotheses regarding the phylogeny of marine bivalve develop-mental types are reviewed in light of new information on the Order Solemyoida.

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

2021 ◽  
Vol 8 ◽  
Author(s):  
Paolo Cocci ◽  
Emanuele Troli ◽  
Mauro Angeletti ◽  
Francesco Alessandro Palermo
Keyword(s):  
Machine Learning ◽  
Adriatic Sea ◽  
Quantitative Estimation ◽  
Artificial Substrates ◽  
Small Scale ◽  
Stock Management ◽  
Fishing Activity ◽  
Egg Capsules ◽  
Analytical Approaches ◽  
Egg Capsule

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.

A Subantarctic rare gastropod reveals a new type of spawn among heterobranchs

2020 ◽  
Vol 190 (2) ◽  
pp. 508-517
Author(s):  
Javier Di Luca ◽  
Pablo E Penchaszadeh ◽  
Guido Pastorino
Keyword(s):  
Developmental Stages ◽  
Average Diameter ◽  
Additional Source ◽  
Capsule Wall ◽  
Egg Capsules ◽  
Adaptive Value ◽  
New Type ◽  
Taxonomic Implications ◽  
Level Identification

Abstract Spawn and specimens of Toledonia biplicata comb. nov. were collected from Burdwood Bank during March 2013. Species-level identification was derived from radular, shell and spawn characters. A low number of eggs laid per spawn (one to three), absence of an external gelatinous mass and a considerably thickened capsule wall (~50 µm) constitute a unique combination of spawn characters among heterobranchs. Egg capsules are ovoid in shape and measure 600–763 × 450–656 µm. They are filled with albuminous liquid, allowing complete intracapsular development of a single embryo. The developmental stages recognized are uncleaved eggs (153 µm in average diameter), veliger stages (279–378 µm in maximal length) and prehatchling juveniles (442–609 µm). Toledonia biplicata increases its volume 40-fold during its intracapsular development, whereas other comparable cephalaspids increase ≤ 4-fold. The role of the capsule wall as protection and an additional source of food is discussed. The adaptive value of these characters in relationship to the environmental conditions of the Magellanic region is discussed. A comparison with the spawn of other cephalaspids, nudibranchs and pleurobranchids is conducted, and the taxonomic implications are discussed. This is the first description of the spawn and developmental stages of a representative of the genus Toledonia.

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