Reproduction and Development in Mollusca

About this book

Reproduction and Development in Mollusca is perhaps the first attempt to comprehensively project the uniqueness of molluscs, covering almost all aspects of reproduction and development from aplacophorans to vampyromorphic cephalopods.

Molluscs are unique amongst others for the presence of a protective external shell, defensive inking, a geographic distribution from a depth of 9,050 m to an altitude of 4,300 m, gamete diversity, and the use of nurse eggs and embryos to accelerate the first few mitotic divisions in embryos. Other remarkable aspects are the natural occurrence of androgenics in a couple of bivalves, viable induced tetraploids, gigantism induced by elevated ploidy, and the complementary role played by mitochondrial genome in sex determination by nuclear genes, together with the uptake and accumulation of steroid hormone from surrounding waters.

In molluscs, sexuality comprises of gonochorism (< 75 %) and hermaphroditism, which itself includes simultaneous hermaphroditism (> 24%), protandry (< 1 %), Marian hermaphroditism and serial hermaphroditism. The presence of a shell affords iteroparity and relatively longer life span in prosobranchs and bivalves, but its absence affords semelparity and short life span in opisthobranchs and cephalopods. Within semelparity, gonochorism facilitates faster growth and larger body size, but hermaphroditism small body size. In opisthobranchs and cephalopods, sex is irrevocably determined at fertilisation by a few unknown genes and is not amenable to any environmental influence. However, the sex-determining mechanism is more a family trait in bivalves. Primary sex differentiation is also fixed and not amenable to environmental factor but secondary differentiation is labile, protracted and amenable to environmental factors. Both sex differentiation and the reproductive cycle are accomplished and controlled solely by neurohormones. In these processes, the role of steroid hormones may be alien to molluscs.

Contents

Introduction
- Molluscan Science
- Taxonomy and Distribution
- Thermal Vents and Cold Seeps
- Energy Budgets
- Life Span and Generation Time
- Spermatogenesis and Fertilization
- Ontogenetic Development
- Locomotion and Dispersal
- Molluscan Fisheries

Shell and Reproduction
- Structure and Diversity
- Latitudes, Predators and Parasites
- Shell and Resource Allocation
- Symmetry and Sinistrals
- Chemical Defense

Sexual Reproduction
- Reproductive Systems
- Gonochorism
- Pathenogenesis
- Hermaphroditism
- Mates and Mating Systems
- Alternative Mating System (AMS)
- Multiple Paternity
- Encapsulation and Nurse Eggs
- Poecilogony and Dispersal Dimorphism
- Brood Protection and Viviparity
- Fecundity

Regeneration and Asexual Reproduction
- Gastropods
- Clio pyrimidata

Aestivation
- Seasonal Aestivation
- Tidal Aestivation
- "Biological Weapon"

Sex Determination
- Inheritance of Color and Symmetry
- Karyotypes and Heterogametism
- Spawning Induction and Cryopreservation
- Ploidy Induction and Gigantism
- Mitochondrial Genome
- Sex Determination Models

Sex Differentiation
- Neuroendocrines
- Steroid Hormones
- Endocrines Disruption
- Parasitic Disruption

Ocean Acidification
- Chemistry of Seawater
- Pelagic Molluscs
- Benthic Molluscs
- Persistent Carry-over Effects
- Effects on Prey-Predators

Uniqueness of Molluscs
- Shell and Iteroparity
- Gamete Diversity
- Gigantism and Polyploidy
- Sexuality and Paternity
- Double Uniparental Inheritance (DUI)
- Vertebrate Type Steroids
- Aestivation vs Cysts

References

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