This review discusses the new biotechnological tools that are arising and promising for conservation and enhancement of fish production, mainly regarding the endangered and the most economically important species. Two main techniques, in particular, are available to avoid extinction of endangered fish species and to improve the production of commercial species. Germ cell transplantation technology includes a number of approaches that have been studied, such as the transplantation of embryo-to-embryo blastomere, embryo-to-embryo differentiated PGC, larvae to larvae and embryo differentiated PGC, transplantation of spermatogonia from adult to larvae or between adults, and oogonia transplantation. However, the success of germ cell transplantation relies on the prior sterilization of fish, which can be performed at different stages of fish species development by means of several protocols that have been tested in order to achieve the best approach to produce a sterile fish. Among them, fish hybridization and triploidization, germline gene knockdown, hyperthermia, and chemical treatment deserve attention based on important results achieved thus far. This review currently used technologies and knowledge about surrogate technology and fish sterilization, discussing the stronger and the weaker points of each approach.

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Embryological studies in fish species are useful to the understanding of their biology and systematics. The available biological data in Leiarius marmoratus are scarce and additional information about its reproductive biology is needed, mainly because this species has been commercially exploited and used in production of hybrid lineages. In order to evaluate the temporal-morphological embryonic modifications in L. marmoratus, samples of nearly 200 embryos were collected at random at different stages of development, starting from fecundation (time zero). Embryos were fixed in modified Karnovsk's solution and 2.5% glutaraldehyde, processed and analysed under optic and electron microscopy. The incubation period of L. marmoratus was equal to 14.42 h at a mean temperature of 28.3 ± 0.07°C. The following stages of embryonic development were established: zygote, cleavage, gastrula, organogenesis and hatching. These stages were divided into phases, as follows: cleavage - phases of 2, 4, 8, 16, 32 and 64 cells and morula; gastrula - phases of 25, 50, 75 and 90% of epiboly and blastopore closure; and organogenesis - neurula, segmentation and pre-larval phases. The embryogenesis of L. marmoratus was typical of neotropical teleosteans, with peculiarities in species development.

The objective of our work was to describe a low toxicity cryoprotectant solution that allowed vitreous solid formation. Embryos of Prochilodus lineatus were submitted to sensitivity evaluations of six internal cryoprotectants (dimethyl sulphoxide -glycerol -GLY and 1,2-propanediol -PROP) at concentrations of 1-6 M; and two external cryoprotectants (sucrose -SUC and glucose -GLU) at concentrations of 0.1-1 M for 20 min. The capacity of the cryoprotectant solutions to exchange heat with the medium and to form glassy solids was evaluated by immersing 10 ll of cryoprotectant in liquid nitrogen. The PROP had a high survival rate at all concentrations evaluated, and was the only substance that allowed a vitreous solid formation.Thus, it is concluded that the PROP-6 M was the most adequate solution for embryonic vitrification processes, because heat exchange between the system (PROP 6 M/embryos/liquid nitrogen) was faster than for other cryoprotectants and combinations thereof; has low toxicity, promote high rates of dehydration in short periods, and reach the vitreous state, being a good candidate to be used in the tests of embryonic vitrification.

Summary Aiming to provide data on the biology of Leiarius marmoratus, which will aid in its production in captivity, as well as in studies for its preservation in the environment, this work had as objectives: analyze and describe main morphological alterations during larval ontogeny of the species. We analyzed 205 individuals, obtained by induced reproduction (Colpani Pisciculture) and kept in CEPTA/ICMBIO, Pirassununga, São Paulo, Brazil. Analyses were performed from hatching moment to 30th day. The specimens were classified into two periods: larval (Stages: vitelline, pre‐flexion, flexion, post‐flexion) and juvenile. Hatched larvae showed ident chromatophores only at anterior and posterior extremities of yolk sac. The standard length ranged from 2.16 mm (yolk) to 28.84 mm (Youth). Dorsal fin rays were initially observed at flexion stage (12–14 rays). Major alterations occurred during post‐flexion/juvenile stage, when dorsal, pectoral, pelvic, anal, and caudal fins were observed and pigmentation intensified throughout the lateral region, forming bands in the body, one between the end of the head and beginning of dorsal to pelvic fin, and another one beginning at dorsal to caudal peduncle and four longitudinal at the head.

This study aimed to establish a hormonal induction protocol for spermiation of Brycon cephalus males, using Ala6, Pro9Net-mGnRH + metoclopramide (Ovopel®). Thus, 20 males were used divided into three inductor treatments [⅓ pellet/kg (T1), ⅔ pellet/kg (T2) and 1⅓ pellet/kg (T3)] and one control group (CO), which only received physiological solution applications (0.9% NaCl). All treatments were applied in a single dose. For evaluation of the availability of the treatment, the following seminal parameters were analyzed: seminal volume, subjective spermatic motility, duration of motility, pH, osmolality and spermatic concentration. T3 showed the highest seminal volume (4.66 ± 1.52 ml), and was significantly different in comparison with T1 (2.0 ± 0.9 ml), T2 (3.5 ± 1.3 ml) and CO (2.3 ± 1.2 ml). In relation to spermatic motility, T2 and T3 showed significantly higher levels [5, (81-100%)]. However, T3 showed significantly lower average sperm motility duration than T1, T2 and CO (30 ± 7 s; 28 ± 6 s; 32 ± 8 s, respectively). With regard to the seminal parameters of spermatic concentration, pH and osmolality, no significant variation was verified among treatments. In conclusion, mGnRH + metoclopramide used for hormonal induction of B. cephalus reproduction does not induce changes related to spermatic concentration, pH and osmolality parameters of the seminal fluid and the most adequate doses among tested treatments were ⅔ pellet/kg live fish.

We aimed to vitrify embryos of Prochilodus lineatus in a high-osmolarity cryoprotectant solution, evaluating, after the vitrification-thawing process, their morphological changes. Thus, 240 embryos in the 20-somite phase (20S) were exposed for 20 min to one main internal cryoprotectant solution (1,2-propanediol-PROP), divided into four immersion sequence steps of five minutes each. The first three steps were performed in solutions containing only a main internal cryoprotectant (PROP-2, 3 and 4 M), and the fourth step in a high-osmolarity solution combining internal (PROP + dimethyl sulphoxide-Me SO) and external cryoprotectants (sucrose-SUC). The final concentration of vitrification was PROP 5 M + Me SO 5 M + SUC 0.2 M. During vitrification, the straws exhibited a translucent solid appearance; however, during thawing, their structure became totally opaque and white. After thawing, the embryos suffered an increase in volume and presented morphological changes including protrusions on the surface of the yolk sac, yolk sac rupture, and optical vesicle degradation. On the inside, we observed intercellular spaces and a yolk syncytial layer (YSL) with altered chromatin. Yet, structures such as somites, neural tube, endoderm and epidermis presented cells with a nucleus and integral mitochondria. We conclude that the use of the tested cryoprotectant solution permits the formation of a vitreous solid and preserves part of the cells of the blastoderm. Yet, the heating protocol does not control recrystallization, resulting in the formation of serious morphological anomalies that prevent the preservation of the embryonic unit.

Summary In the Neotropical cichlid Cichla kelberi the spermiogenesis appears to be of the cystic type and is characterized by gradual chromatin condensation in juxtaposed clusters, nuclear rotation (with the flagellum perpendicularly to the nucleus), and consequent nuclear fossa formation. Besides, there is cytoplasma migration to the nuclear base while eliminating the cytoplasmic residual mass. The heads of the spermatozoa are round, with approximately 1.87 μm in diameter; the nucleus has clusters juxtaposed of condensed chromatin. The nuclear fossa in single arc shape is moderate and slightly eccentric to the nuclear base. The midpiece is short and presents a cytoplasmic sheath, which dilated in its extremes. The mitochondria are spherical or slightly elongated. The flagellum presents the classical axoneme 9 + 2 and one pair of fins. The Type I C. kelberi spermatozoon has its flagellum perpendicularly positioned in relation to the nucleus base. The presence of only one flagellum characterize it as the basic spermatozoon in teleost, known as single anacrosomal aquasperm spermatozoon. Besides the patterns of previously cited characteristics between its representatives, the cytoplasmic sheath and flagellum fins presence can be consider as characteristics of the Cichla genus.