Surrogate Broodstock Development in Aquaculture

Sullip Kumar Majhi

• Publisher: CRC Press
• Year: 2020
• ISBN:
  9781000202199
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Marine Biology
• Index: Biological Sciences

The rapidly changing climatic condition coupled with habitat destruction, aquatic pollution and increasing anthropogenic pressure on water bodies have resulted in decline of many important fish population and some of them even become endangered. As of now the breeding protocol for seed production in captivity is developed for only handful of fish species and mostly their seed is collected from natural resources for aquaculture. This factor limits the efforts for species diversification in aquaculture. There are approaches/ technologies to generate seed of such fish species for aquaculture, especially the species that are too large to propagate in captivity or species those do not response to hormonal treatments due to stress of confinement. One of the viable approach is surrogate broodstock development using adult fish as the recipient. The obvious advantage of using adult fish as recipient is that, the donor-derived gametes can be generated within few months after stem cell transplantation; oppose to using embryos or young hatchlings those take years together to attain sexual maturity.

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CHAPTER - 1

GENERAL INTRODUCTION

Germ Cell Transplantation was first demonstrated in mouse and was performed with dispersed testicular cell suspensions containing unknown numbers of spermatogonia cells derived from donor males and microinjected into sterilized male recipients, leading to establishment of donor-derived spermatogenesis and production of surrogate gametes. Since then, the technique has been extensively used for the purpose of basic research, reproductive medicine and treatment of infertility, but surprisingly remains, in part, unexplored in fish, even though germ cell transplantation has potential applications in fish bioengineering (see Fig. 1)

During the beginning of 20th century, making a breakthrough, a similar approach was developed by the Japanese scientists in fish using transplantation of primordial germ cells carrying green fluorescent protein into coelomatic cavity of rainbow trout hatchlings resulted in production of sperm with donor genetic characteristics that was capable of fertilizing the eggs. Further, using the same methodology, xenogenic transplantation between rainbow (Onchorhynchus mykiss) and masu (O.masu) trout were also successfully performed . However, germ cell transplantation using embryos and/or hatchlings requires very sophisticated instruments for the primordial germ cells isolation and quantum of labor for cell transplantation. Beside, the transplanted embryos takes considerably long time to reach adulthood and to produce the donor-derived functional gametes, for which significant amount of investment will be required for feeds and manpower inputs. Consequently, the hatchery units, which are the end user of the technique may not be interested to adopt the technique for the commercial production of valued fish seeds. In contrast, development of surrogate broodstock involving transplantation of spermatogonia cells derived from target species into a related adult fish species, depleted of endogenous germ cells using suitable ablative strategy and, for which captive breeding technique are well developed, might considerably shorten in production of donor-derived gametes and, make the technique of germ cell transplantation more simple and viable to be practically feasible for end users.

Fig. 1. Potential applications of germ cell transplantation in the field of reproductive biotechnology. A) Production of fish from surrogate parents. Using this technique, commercially important species can be quickly propagated by transplanting germ cells from target species into xenogeneic recipients. B) Transgenic production. This technique can be used by transfecting germ cells in vitro and transplanted into allogeneic recipients, followed by retrieval of germ cells. C) Preservation of genetic materials of endangered species. The cryopreservation and xenogeneic transplantation of germ cells from endangered species make it possible to regenerate them, even in case of extinction.

In this context, in this book, germ cell transplantation in adult fish is systematically narrated using two congeneric model species of atherinopsid fishes, the Pejerrey (Odontesthes bonariensis) and the Patagonian Pejerrey (O. hatcheri) as donor and recipient, respectively. These two species used as model due to the wealth of basic information available on its reproductive physiology, can be easily bred in captivity and availability of several genetic markers to distinguish them.

This book is composed of five chapters as follows: 1) Recipient preparation for surrogate broodstock development, 2) Surrogate broodstock development by surgical approach, 3) Surrogate broodstock development by non-surgical approach, 4) Importance of surrogate broodstock in aquaculture and 5) Instrument used for surrogate broodstock development in fish. These chapters aim to explore in depth from ablation strategy of endogenous germ cells in recipients prior to introduction of donor germ cells for production of donor-derived progeny from the surrogate parents by artificial fertilization and natural spawning.

It is anticipated that the contents of this book will have broader implications in aquaculture for production of progeny from the fish species that are difficult to propagate in captivity but posses high commercial value, which are too large for hatchery rearing and that do not spawn due to the stress of confinement, or whose maturation cycle is associated with complex migratory behavior.

CHAPTER - 2

RECIPIENT PREPARATION FOR SURROGATE BROODSTOCK DEVELOPMENT

Germ cell transplantation, a technique first demonstrated in mouse, is a promising reproductive technology with potential application in animal reproduction and conservation of endangered species from fish to mammals. This procedure, which is based on the transplantation of donor germ cells into a surrogate gonad, allows the speedy and theoretically unlimited production of donor-origin gametes from the donor without interference from the host’s genome, that is, the animals produced with transplanted cells are not transgenic animals. Thus, highly productive individuals could be propagated far above their reproductive capacity and beyond their lifespan without resorting to time-consuming procedures of gamete collection, cryopreservation, and artificial fertilization. In addition, germ cells could be harvested from immature as well as aging donor animals and can be induced to develop into functional gametes timely by transplantation into an adult, sexually-competent recipient animal. In this way, this procedure offers a way to preserve genetic material from animals that might otherwise die prior to sexual maturity or become senile, and this is extremely important in the case of rare, endangered and commercially important species. There has been recently a great interest in the application of germ cell transplantation to aquatic animals, in particular for fish. Fishes are generally prolific and germ cell transplantation using related species as recipients could be used to propagate commercially important species which are too large for hatchery rearing, that do not spawn due to the stress of confinement, or whose maturation cycle is associated with complex migratory behavior which cannot be reproduced in captivity.

One of the preconditions for surrogate broodstock development is the availability of a suitable host species whose gonads are physiologically and immunologically compatible with the donor’s germ cells and which meets the requirements of easy maintenance and breeding in captivity. Closely related species generally meet the physiological and immunological requirements, but the recipient animal preferably should be artificially depleted of its endogenous germ cells so that there is a relatively higher yield of donor-derived gametes. For instance, Brinster and colleagues showed that the introduced cells have improved access to the basal compartment of seminiferous tubules of mouse when the recipient testis is depleted of endogenous germ cells prior to transplantation. Several options for depletion of germ cells have been tested in mammals suc...