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Steindachneridion parahybae is a freshwater catfish endemic to the Paraíba do Sul River and is classified as an endangered Neotropical species. An increasing number of conservation biologists are incorporating morphological and physiological research data to help conservation managers in rescue these endangered species. This study investigated the embryonic and larval development of S. parahybae in captivity, with emphasis in major events during the ontogeny of S. parahybae. Broodstocks were artificially induced to reproduce, and the extrusion occurred 200-255 degree-hours after hormonal induction at 24°C. Larval ontogeny was evaluated every 10 minutes under microscopic/stereomicroscopic using fresh eggs samples. The main embryogenic development stages were identified: zygote, cleavage, including the morula, blastula, gastrula phase, organogenesis, and hatching. The extruded oocytes showed an average diameter of 1.10 ± 0.10 mm, and after fertilization and hydration of eggs, the average diameter of eggs increased to about 1.90 ± 0.60 mm, characterized by a large perivitelline space that persisted up to embryo development, the double chorion, and the poles (animal and vegetative). Cell division started about 2 minutes after fertilization (AF), resulting in 2, 4, 8 (4 x 2 arrangement of cells), 16 (4 x 4), 32 (4 x 8) and 64 (2 x 4 x 8) cells. Furthermore, the blastula and gastrula stages followed after these cells divisions. The closed blastopore occurred at 11 h 20 min AF; following the development, the organogenetic stages were identified and subdivided respectively in: early segmentation phase and late segmentation phase. In the early segmentation phase, there was the establishment of the embryonic axis, and it was possible to distinguish between the cephalic and caudal regions; somites, and the optic vesicles developed about 20 h AF. Total hatching occurred at 54 h AF, and the larvae average length was 4.30 ± 0.70 mm. Gradual yolk sac reduction was observed during the first two days of larval development. The first feeding occurred at the end of the second day. During the larval phase, cannibalism, heterogeneous larval growth and photophobia were also observed. This information will be important in improving the artificial reproduction protocols of S. parahybae in controlled breeding programs.Steindachneridion parahybae é um bagre de água doce, endêmico do rio Paraíba do Sul e é classificado como espécie neotropical ameaçada. Um número crescente de biólogos conservacionistas estão incorporando dados de pesquisas morfológicas e fisiológicas para ajudar os gestores de conservação no resgate destas espécies ameaçadas de extinção. Este estudo investigou o desenvolvimento embrionário e larval de S. parahybae em cativeiro, com ênfase nos principais eventos durante a ontogenia de S. parahybae. Reprodutores foram artificialmente induzidos à reprodução e a extrusão ocorreu com 200-255 horas-graus após a indução hormonal a 24°C. A ontogenia larval foi avaliada a cada 10 minutos sob microscópio/ estereomicroscópio, utilizando-se amostras de ovos recém coletados. Os principais estágios de desenvolvimento embrionário foram identificados: zigoto, clivagem, incluindo as fases, mórula, blástula e gástrula, organogênese e eclosão. Os ovócitos extrusados apresentaram uma média de diâmetro de 1,10 ± 0,10 mm e depois da fertilização e hidratação dos ovos, a média de diâmetro dos ovos aumentou para 1,90 ± 0,60 mm, caracterizado pelo grande espaço vitelínico que persistiu até o desenvolvimento do embrião, duplo córion e os polos (animal e vegetal). A divisão celular iniciou-se aproximadamente dois minutos após a fertilização (AF), resultando em 2, 4, 8 (4 x 2 arranjo das células), 16 (4 x 4), 32 (4 x 8) e 64 (2 x 4 x 8) células. Adicionalmente, seguiram as fases de blástula e gástrula depois das divisões celulares. O fechamento do blastóporo ocorreu às 11 h 20 min AF; seguindo o desenvolvimento, os estágios de organogênese foram identificados e subdivididos, respectivamente em: fase de divisão inicial e fase de divisão avançada. Na fase de divisão inicial, depois do estabelecimento do eixo do embrião, foi possível distinguir as regiões cefálica e caudal; os somitos e as vesículas ópticas se desenvolveram com aproximadamente 20 h AF. A eclosão total ocorreu com cerca de 54 h AF e o comprimento médio foi de 4,30 ± 0,70 mm. A redução gradual do saco vitelínico foi observada durante os primeiros dois dias de desenvolvimento larval. A primeira alimentação ocorreu no final do segundo dia. Durante a fase larval, canibalismo, crescimento larval heterogêneo e fotofobia também foram observados. Estas informações serão importantes para aperfeiçoar o protocolo de reprodução artificial em S. parahybae em programas de reprodução controlada.

Lophiosilurus alexandri is an endemic fish from the São Francisco River basin, Brazil. The aim of this study was to induce L. alexandri to spawn and to obtain data on several reproductive variables for this species. For induced spawning, adults were submitted to Cyprinus carpio pituitary homogenate (CPH). Nine of the 12 females (75%) responded positively to the treatment. The stripping of oocytes was performed 8.4 h after the second dose of CPH with the water temperature maintained at 26ºC. The number of stripped oocytes per gram of ova was 74 ± 5 oocytes g-1, and the mean oocyte diameter was 3.1 ± 0.2 and 3.6 ± 0.2 mm, before and after hydration, respectively. The oocytes were opaque, yellowish, demersal, highly adhesive, and covered by a gelatinous coat. The total fecundity was 4,534 ± 671 oocytes, and the fertilization rate was 59%. The initial and final fertilities were 2,631 ± 740 and 1,542 ± 416 embryos, respectively. Larval hatching occurred up to 56 h after fertilization, and the larvae had a total length of 8.4 ± 0.1 mm. This work provides important biological information for L. alexandri that can be used for management and conservation of this species.

The "surubim do Paraíba" (Steindachneridion parahybae) is a freshwater catfish endemic to the Paraíba do Sul River basin, Brazil. This species has been seriously threatened by environmental disturbances in the last several decades. Wild Steindachneridion parahybae males and females were collected in 2003 and taken to the hatchery of a power plant of the Companhia Energética de São Paulo (CESP). Steindachneridion parahybae broodstocks were artificially induced to reproduce in December 2003 using a combination of carp pituitary extract (CPE) and human chorionic gonadotropin (hCG). Oocytes and milt were stripped; the fertilized eggs were transferred to 60-liter conical incubators and hatched larvae distributed in nine horizontal trays. Exogenous feed was started just after yolk sac absorption. A high rate of cannibalism and photophobia were observed during the larval period, resulting in a 26% survival rate from larvae to fingerlings.

Steindachneridion parahybae is a freshwater catfish endemic to the Paraíba do Sul River and is classified as an endangered Neotropical species. An increasing number of conservation biologists are incorporating morphological and physiological research data to help conservation managers in rescue these endangered species. This study investigated the embryonic and larval development of S. parahybae in captivity, with emphasis in major events during the ontogeny of S. parahybae. Broodstocks were artificially induced to reproduce, and the extrusion occurred 200-255 degree-hours after hormonal induction at 24°C. Larval ontogeny was evaluated every 10 minutes under microscopic/stereomicroscopic using fresh eggs samples. The main embryogenic development stages were identified: zygote, cleavage, including the morula, blastula, gastrula phase, organogenesis, and hatching. The extruded oocytes showed an average diameter of 1.10 ± 0.10 mm, and after fertilization and hydration of eggs, the average diameter of eggs increased to about 1.90 ± 0.60 mm, characterized by a large perivitelline space that persisted up to embryo development, the double chorion, and the poles (animal and vegetative). Cell division started about 2 minutes after fertilization (AF), resulting in 2, 4, 8 (4 x 2 arrangement of cells), 16 (4 x 4), 32 (4 x 8) and 64 (2 x 4 x 8) cells. Furthermore, the blastula and gastrula stages followed after these cells divisions. The closed blastopore occurred at 11 h 20 min AF; following the development, the organogenetic stages were identified and subdivided respectively in: early segmentation phase and late segmentation phase. In the early segmentation phase, there was the establishment of the embryonic axis, and it was possible to distinguish between the cephalic and caudal regions; somites, and the optic vesicles developed about 20 h AF. Total hatching occurred at 54 h AF, and the larvae average length was 4.30 ± 0.70 mm. Gradual yolk sac reduction was observed during the first two days of larval development. The first feeding occurred at the end of the second day. During the larval phase, cannibalism, heterogeneous larval growth and photophobia were also observed. This information will be important in improving the artificial reproduction protocols of S. parahybae in controlled breeding programs.

Abstract The Steindachneridion parahybae is an endangered catfish from Brazil and strategies applied for gametes optimization are necessary. The aim of this study was to assess inseminating doses and water volume upon the fertilization, hatching rates and percentage of normal larvae in S. parahybae . Was used a randomized design in factorial scheme (4×4) with four inseminating doses: 1.0×104, 1.0×105, 1.0×106, 1.0×107spermatozoa oocyte-1 and four volumes of water: 1, 35, 65 and 95mL of water g-1 of oocytes. The combination of doses and volumes were performed in triplicates (n=48). Each incubator (1.5L of useful volume) with 1g of oocytes was considered as an experimental unit. Significant interaction between inseminating doses and volumes of water to the values of the fertilization rates and quadratic effect of doses and volume for the values of hatching rates were observed. The doses and volumes did not influence the percentage of normal larvae (87.70±5.06%). It is recommended the use of 5.5×106 spermatozoa oocyte-1 and 1mL of water g-1 of oocytes during in vitro fertilization procedure. These results allowed us to develop new biotechnological strategies applied to the conservation of S. parahybae .