Topic
Egg case
About: Egg case is a research topic. Over the lifetime, 52 publications have been published within this topic receiving 1313 citations.
Papers published on a yearly basis
Papers
TL;DR: Phylogenetic position, geographical distribution, benthic vs. pelagic habitat, adult size, egg-embryo size, feeding ecology, and embryonic osmoregulation are factors in the retention of oviparity or the evolution of viviparity.
Abstract: Patterns of chondrichthyan reproduction and development are diverse. Species either are reproductively active throughout the year, or have a poorly defined annual cycle with one or two peaks of activity, or have a well defined annual or biennial cycle. Based on embryological origin and adult morphology, their reproductive system is more similar to tetrapods than to teleosts. Primordial germ cells are of endodermal origin. The Wolffian ducts in males and Mullerian ducts in females become the functional urogenital ducts. Differentiation is under hormonal control. Unusual features of the reproductive system include an epigonal organ in males and females. It contains lymphoid and hemopoietic tissue. Leydig's gland, a modified region of the kidney, produces seminal fluid. In some species, sperm passing through the vas deferens, is enclosed in spermatophores. Rotating about their long axis, helical spermatozoa can move forward or reverse direction. Spermatogenesis often occurs in bicellular units, spermatocysts. These consist of a spermatogonium enclosed in a Sertoh cell. Fertilization is internal. Claspers, modified portions of the pelvic fins act as intromittent organs. In many viviparous sharks and rays, the female reproductive system is asymmetrical. Eggs of some sharks are the largest known cells. Yolk platelets contain lipovitellin. Oocytes have lampbrush chromosomes. Eggs released from the ovary into the body cavity are transported by ciliary action to the ostium of the oviduct. There they are fertilized. Physiological polyspermy is normal. The shell gland, a specialized region of the anterior oviduct, functions both in long term sperm storage and in egg case production. Egg cases of sharks and skates consist of unique collagenous protein with a 400 A period, organized as a cholesteric liquid crystal. Chimaeroid egg cases contain 550 A pseudotubules in orthogonal lattices. In small sharks, males copulate by coiling around the female. A parallel position is assumed by large sharks. Skates and rays copulate with ventral surfaces apposed or by a dorsal approach. Biting is a pre-copulatory release mechanism. Parental care, except for selective oviposition, is lacking. Heavily yolked eggs undergo meroblastic, discoidal cleavage. Development is lengthy, shortest (2–4 months) in rays, longer in skates (3–8 months) and longest (9–22 months) in sharks and chimaeras. Most sharks and all rays are viviparous. Chimaeras, skates, and some sharks are oviparous. Viviparity either involves a yolk sac placenta or is aplacental. If aplacental, the embryo derives nutrients either from yolk reserves, or by intra-uterine embryonic cannibalism, or from placental analogues which secrete “uterine milk.” Phylogenetic position, geographical distribution, benthic vs. pelagic habitat, adult size, egg-embryo size, feeding ecology, and embryonic osmoregulation are factors in the retention of oviparity or the evolution of viviparity.
485 citations
TL;DR: A novel egg-deposition mode for Phasmatodea is reported performed by an undescribed Vietnamese species of the enigmatic subfamily Korinninae that produces a complex egg case (ootheca), containing numerous eggs in a highly ordered arrangement.
Abstract: The eggs of stick and leaf insects (Phasmatodea) bear strong resemblance to plant seeds and are commonly dispersed by females dropping them to the litter. Here we report a novel egg-deposition mode for Phasmatodea performed by an undescribed Vietnamese species of the enigmatic subfamily Korinninae that produces a complex egg case (ootheca), containing numerous eggs in a highly ordered arrangement. This novel egg-deposition mode is most reminiscent of egg cases produced by members of unrelated insect orders, e.g. by praying mantises (Mantodea) and tortoise beetles (Coleoptera: Cassidinae). Ootheca production constitutes a striking convergence and major transition in reproductive strategy among stick insects, viz. a shift from dispersal of individual eggs to elaborate egg concentration. Adaptive advantages of ootheca formation on arboreal substrate are likely related to protection against parasitoids and desiccation and to allocation of specific host plants. Our phylogenetic analysis of nuclear (28S, H3) and mitochondrial (COI, COII) genes recovered Korinninae as a subordinate taxon among the species-rich Necrosciinae with Asceles as sister taxon, thus suggesting that placement of single eggs on leaves by host plant specialists might be the evolutionary precursor of ootheca formation within stick insects.
92 citations
TL;DR: It is suggested that oviparity in skates appeared as an adaptation to maximize fecundity (40–160 eggs per year, as compared to 2–18 pups annually or biannually in viviparous guitarfishes, the plesiomorphic sister clade of skates).
Abstract: Mean predation rates (± SD) on egg cases of the skates Bathyraja macloviana, B. albomaculata, Amblyraja doellojuradoi, and Psammobatis spp. from the southwestern Atlantic were estimated to be 0.151 (±0.230), 0.423 (±0.344), 0.254 (±0.390), and 0.150 (±0.288), respectively. These estimates are within the ranges reported earlier (14–40%). Egg cases of B. albomaculata were preyed on in higher proportion than expected from their abundance and suffered a heavier predation rate where the snail Trophon acanthodes was present. Predation rates were not correlated with the thickness of the egg case wall, which indicates that other factors (ecological or chemical) could explain this pattern. Five types of boreholes were found in the egg cases: one was attributable to muricid gastropods, one to naticid gastropods, and a third type to an unknown gastropod (probably Fusitriton magellanicus); the remaining were of unknown origin. Cladistic analyses showed that skates are secondarily oviparous and have maximized adaptations for living in deep water. We suggest that oviparity in skates appeared as an adaptation to maximize fecundity (40–160 eggs per year, as compared to 2–18 pups annually or biannually in viviparous guitarfishes, the plesiomorphic sister clade of skates). If a predation rate of 24% (the mean of predation rates of all skate species studied to date) is applied to the range of fecundities reported for skates, the result is that 18–114 viable pups are produced annually per female skate. Even with a high mortality rate of 64% (the only direct estimate of natural mortality for any elasmobranch), each female skate produces 17–54 eggs annually. These values are higher than most elasmobranch fecundities. This maximization of fecundity is possible mainly because the fecundity of oviparous species is not limited by body size, as in viviparity. The protracted egg-laying season (4–12 months) of most skates (as in many other deep-sea fishes) maximizes the number of eggs laid.
67 citations
Journal Article•
TL;DR: The reproductive cycle of female and male thorny skates taken off the coast of New Hampshire from May 2001 to May 2003 is described and characterizes, indicating that the thorny skate is reproductively active year round.
Abstract: — The thorny skate (Ambly-raja radiata) is a large species of skate that is endemic to the waters of the western north Atlantic in the Gulf of Maine. Because the biomass of thorny skates has recently declined below threshold levels mandated by the Sustainable Fisheries Act, com-mercial harvests from this region are prohibited. We have undertaken a comprehensive study to gain insight into the life history of this skate. The present study describes and characterizes the reproductive cycle of female and male thorny skates, based on monthly samples taken off the coast of New Hampshire, from May 2001 to May 2003. Gonadoso-matic index (GSI), shell gland weight, follicle size, and egg case formation, were assessed for 48 female skates. In general, these reproductive para-meters remained relatively constant throughout most of the year. However, transient but significant increases in shell gland weight and GSI were observed during certain months. Within the cohort of specimens sam-pled monthly throughout the year, a subset of females always had large preovulatory follicles present in their ovaries. With the exception of June and September specimens, egg cases undergoing various stages of develop-ment were observed in the uteri of specimens captured during all other months of the year. For males (n=48), histological stages III through VI (SIII−SVI) of spermatogenesis, GSI, and hepatosomatic index (HSI) were examined. Although there appeared to be monthly fluctuations in spermato-genesis, GSI, and HSI, no significant differences were found. The produc-tion and maintenance of mature sper-matocysts (SVI) within the testes was observed throughout the year. These findings collectively indicate that the thorny skate is reproductively active year round.
46 citations
1 Jan 2008
TL;DR: Evidence indicates that the Alaska skate uses the eastern Bering Sea outer continental shelf region for reproduction and the middle and inner shelf regions as habitat for immature and subadults.
Abstract: A nursery site for the Alaska skate (Bathyraja parmifera)
was sampled seasonally from June 2004 to July 2005. At the small nursery site (~2 km2), located in a highly productive area near the shelf-slope interface at the head of Bering Canyon in the eastern Bering Sea, reproductive males and females dominated the catch and neonate and juvenile skates were rare. Seasonal samples showed summertime (June and July) as the peak reproductive time in the nursery although some reproduction occurred throughout the year. Timeseries
analysis of embryo length frequencies revealed that three cohorts were developing simultaneously and the period of embryonic development was estimated at 3.5 years and average
embryo growth rate at 0.2 mm/day. Estimated egg case deposition occurred mainly during summertime and hatching occurred during winter months. Protracted hatching times
may be common for oviparous elasmobranch species and may be directly correlated with ambient temperatures as evident from a meta-data analysis. Evidence indicates that the Alaska skate uses the eastern Bering Sea outer continental shelf region for reproduction and the middle and inner
shelf regions as habitat for immature and subadults. Skate nurseries may be vulnerable to disturbances because they are located in highly productive areas and because embryos develop slowly.
42 citations
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Performance Metrics
| Year | Papers |
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| 2021 | 1 |
| 2020 | 1 |
| 2019 | 1 |
| 2018 | 1 |
| 2016 | 3 |
| 2015 | 1 |