The cellular basis of compensatory muscle growth in the teleost Odontesthes bonariensis

This study evaluates white muscle growth and in vivo cell proliferation during a fasting and refeeding trial, using pejerrey Odontesthes bonariensis as animal model, in order to better understand the cellular basis governing catch-up growth. Experiments consisted in two groups of fish, a control one continuously fed ad libitum, and a group fasted for 2 weeks and then fed for another 2 weeks. We examined how the formation of new muscle fibers and their increase in size were related to muscle precursor cell (MPC) proliferation under both experimental conditions. During fasting, the number of 5-ethynyl-2'-deoxyuridinepositive (EdU+) cells decreased along with myogenic regulatory factors (MRF) mRNA levels related to myoblast proliferation and differentiation, and the muscle stem cell-markerPax7 mRNA level increased. Analysis of myomere cross-sectional area, distribution of muscle fiber sizes and number of fibers per myomere showed that muscle hypertrophy but not hyperplasia was inhibited during fasting. Both higher igf2 mRNA level and the persistence of cell proliferation could be supporting new myofibre formation. On the other hand, an exacerbated MPC proliferation occurred during catch-up growth, and this increase in cell number could be contributing to the growth of both pre-existing and newly form small fibers. The finding that some MPCs proliferate during fasting and that muscle growth mechanisms, hyperplasia and hypertrophy, are differentially regulated could help to explain why re-fed fish could growth at higher rates, and why they return to the lost growth trajectory.

Comparative Analysis of Pejerrey Fish (Odontesthes bonariensis) Gonadal Development During Two Consecutive Spawning Seasons in Relation to Sex Steroids and Temperature Variation in Cochicó Lake (Pampas Region, Argentina)

Cochicó belongs to “Encadenadas del Oeste” system of lakes being a typical water body of the Pampas region. The most abundant fish species in this lake is the pejerrey (Odontesthes bonariensis) valued due to the quality of its flesh and as a game fish. The aim of this study was to compare the gonadal stages of pejerrey during two consecutive spawning seasons (August to December) in relation to sexual steroids and temperature in this lake. In general, pejerrey gonadal development, the Gonadosomatic index and the plasma levels of estradiol and testosterone fluctuated in relation with temperature. In 2014 samplings, females started to ovulating in early August, with a peak during September-October and ending in December with many of them with atretic oocytes. However, in 2015, a marked delay in maturation was observed with ovulated fish only in October and December. This fact may be because the minors mean temperatures recorded in this year. For males, it was possible to find spermiating animals during the whole spawning season and only arrested animals in December. Unexpectedly, histological gonadal analysis revealed for the first time pejerrey with testis-ova, probably due to the intensive use of agrochemicals in this region.

Evaluación del crecimiento del Pejerrey Odontesthes bonariensis (Pisces, Atherinopsidae) cultivados en jaulas flotantes en el Lago Titicaca

The pejerrey, is a species introduced to Lake Titicaca from the continental waters of Argentina. The study was carried out at the Titicaca Trout Fishing Company, located in front of the city of Pomata, Puno Region, at an altitude of 3882 msnm. The objective of this study was to evaluate the growth of Odontesthes bonariensis from two batches (A and B) grown in Titicaca, Peru, in floating cages developed in 2018 and 2019. Silverside juveniles of 77.9 mm in length were used. average 120 days old, sowing a total of 8500 individuals (batch A = 5300 and batch B = 3200), from artificial spawning of broodstock confined in floating cages. After 360 days in batch A, a maximum total length of 230.0 ± 2.10 mm was achieved, total weight 80.0 ± 1.73 g, the feed conversion was found at 1.7 ± 1.39. In batch B, a maximum total length of 231.7 mm ± 2.70 was obtained, total weight 83.07 ± 1.67 g and the feed conversion factor was found at 1.3 ± 0.67. The feed used was commercial trout feed. It is concluded that the trials of silverside growth in floating cages in Lake Titicaca (Peru), presented encouraging results, showing that the fish tolerates the type of culture and could become an alternative for the development of aquaculture in the region.

PREVALENCIA, INTENSIDAD YASPECTOS ECOLOGICOS DE CONTRACAECUM SP. (NEMATODE: ANISAKIDAE) EN PECES DE AGUA DULCE DE ARGENTINA

El género Contracaecum pertenece a la familia Anisakidae, la cual incluye parásitos de considerable importancia económica y médica. Las larvas de Contracaecum están asociadas con una amplia variedad de peces marinos y de agua dulce. Si bien, hay una gran cantidad de reportes que indican la presencia de anisákidos en peces de diferentes partes del mundo, los estudios en la región central de Argentina son escasos, pese a las prevalencias observadas en años recientes. Este estudio proporciona nuevos registros y analiza aspectos ecológicos de larvas de Contracaecum presentes en peces de ambientes acuáticos con diferentes características hidrológicas ubicados en el centro de Argentina. Se examinó un total de 1402 peces pertenecientes a nueve especies, seis familias y cuatro órdenes. Los helmintos fueron hallados en Astyanax eigenmanniorum (Characidae), Oligosarcus jenynsii (Characidae), Odontesthes bonariensis (Atherinopsidae), Hoplias malabaricus (Erythrinidae), Pimelodus albicans (Pimelodidae) y Rhamdia quelen (Pimelodidae). Estas últimas tres especies hospedadoras exhibieron prevalencias de hasta 100% e intensidades máximas de 162, 180 y 48 larvas/pez, respectivamente. La totalidad de los parásitos hallados se corresponden con larvas de tercer estadio de Contracaecum sp., compatibles con el tipo 2.

Talla de primera madurez del pejerrey argentino (Odontesthes bonariensis) en la laguna de Pacucha, Apurímac – Perú

El pejerrey argentino Odontesthes bonariensis es una especie de importancia para la seguridad alimentaria y economía local en varias regiones de la sierra del Perú. Es una especie que está sujeta a explotación pesquera en la laguna Pacucha, ubicada en la región Apurímac. Dado al valor que tiene como recurso, el objetivo de la investigación fue estudiar la biología reproductiva del pejerrey argentino Odontesthes bonariensis en la laguna de Pacucha. Los análisis se efectuaron a partir observaciones mensuales (quince meses) sobre ejemplares de pejerrey obtenidos por capturas exploratorias y de la pesca comercial. Los ejemplares capturados fueron sometidos a muestreo biométrico y biológico a fin de obtener datos para determinación de las características reproductivas, entre ellas la talla de primera madurez. Teniendo en cuenta que las hembras presentan considerable actividad reproductiva entre los meses de agosto y octubre, se consideró la información de dicho periodo para estimar la talla de primera madurez. Según los resultados obtenidos, los machos alcanzan la primera madurez a los 18,8 cm LT y las hembras a los 20,8 cm LT, valores menores a la talla mínima de captura establecida para el recurso en la región Apurímac.