Cardiorespiratory physiological phenotypic plasticity in developing air-breathing anabantid fishes (Betta splendens and Trichopodus trichopterus)

Articulo CientificoDevelopmental plasticity of cardiorespiratory physiology in response to chronic hypoxia is poorly understood in larval fishes, especially larval airbreathing fishes, which eventually in their development can at least partially “escape” hypoxia through air breathing. Whether the development air breathing makes these larval fishes less or more developmentally plastic than strictly water breathing larval fishes remains unknown. Consequently, developmental plasticity of cardiorespiratory physiology was determined in two air-breathing anabantid fishes (Betta splendens and Trichopodus trichopterus). Larvae of both species experienced an hypoxic exposure that mimicked their natural environmental conditions, namely chronic nocturnal hypoxia (12 h at 17 kPa or 14 kPa), with a daily return to diurnal normoxia. Chronic hypoxic exposures were made from hatching through 35 days postfertilization, and opercular and heart rates measured as development progressed. Opercular and heart rates in normoxia were not affected by chronic nocturnal hypoxic. However, routine oxygen consumption _ MO2 (~4 lmol O2/g per hour in normoxia in larval Betta) was significantly elevated by chronic nocturnal hypoxia at 17 kPa but not by more severe (14 kPa) nocturnal hypoxia. Routine _ MO2 in Trichopodus (6–7 lmol O2/g per hour), significantly higher than in Betta, was unaffected by either level of chronic hypoxia. PCrit, the PO2 at which _ MO2 decreases as ambient PO2 falls, was measured at 35 dpf, and decreased with increasing chronic hypoxia in Betta, indicating a large, relatively plastic hypoxic tolerance. However, in contrast, PCrit in Trichopodus increased as rearing conditions grew more hypoxic, suggesting that hypoxic acclimation led to lowered hypoxic resistance. Species-specific differences in larval physiological developmental plasticity thus emerge between the relatively closely related Betta and Trichopodus. Hypoxic rearing increased hypoxic tolerance in Betta, which inhabits temporary ponds with nocturnal hypoxia. Trichopodus, inhabiting more permanent oxygenated bodies of water, showed few responses to hypoxia, reflecting a lower degree of developmental phenotypic plasticity.Support for this study was provided by NSF operating grant IOS-1025823 and IOS- 1543301 to Warren Burggren. The Collaboration Network in Comparative Ecophysiology of Vertebrates UAEM-PRODEP 11067 also provided support

Cardiorespiratory physiological phenotypic plasticity in developing air-breathing anabantid fishes (Betta splendens and Trichopodus trichopterus)

Articulo CientificoDevelopmental plasticity of cardiorespiratory physiology in response to chronic hypoxia is poorly understood in larval fishes, especially larval airbreathing fishes, which eventually in their development can at least partially “escape” hypoxia through air breathing. Whether the development air breathing makes these larval fishes less or more developmentally plastic than strictly water breathing larval fishes remains unknown. Consequently, developmental plasticity of cardiorespiratory physiology was determined in two air-breathing anabantid fishes (Betta splendens and Trichopodus trichopterus). Larvae of both species experienced an hypoxic exposure that mimicked their natural environmental conditions, namely chronic nocturnal hypoxia (12 h at 17 kPa or 14 kPa), with a daily return to diurnal normoxia. Chronic hypoxic exposures were made from hatching through 35 days postfertilization, and opercular and heart rates measured as development progressed. Opercular and heart rates in normoxia were not affected by chronic nocturnal hypoxic. However, routine oxygen consumption _ MO2 (~4 lmol O2/g per hour in normoxia in larval Betta) was significantly elevated by chronic nocturnal hypoxia at 17 kPa but not by more severe (14 kPa) nocturnal hypoxia. Routine _ MO2 in Trichopodus (6–7 lmol O2/g per hour), significantly higher than in Betta, was unaffected by either level of chronic hypoxia. PCrit, the PO2 at which _ MO2 decreases as ambient PO2 falls, was measured at 35 dpf, and decreased with increasing chronic hypoxia in Betta, indicating a large, relatively plastic hypoxic tolerance. However, in contrast, PCrit in Trichopodus increased as rearing conditions grew more hypoxic, suggesting that hypoxic acclimation led to lowered hypoxic resistance. Species-specific differences in larval physiological developmental plasticity thus emerge between the relatively closely related Betta and Trichopodus. Hypoxic rearing increased hypoxic tolerance in Betta, which inhabits temporary ponds with nocturnal hypoxia. Trichopodus, inhabiting more permanent oxygenated bodies of water, showed few responses to hypoxia, reflecting a lower degree of developmental phenotypic plasticity.Support for this study was provided by NSF operating grant IOS-1025823 and IOS- 1543301 to Warren Burggren. The Collaboration Network in Comparative Ecophysiology of Vertebrates UAEM-PRODEP 11067 also provided support

Very high blood oxygen affinity and large Bohr shift differentiates the airbreathing siamese fighting fish (Betta splendens) from the closely related anabantoid the blue gourami (Trichopodus trichopterus)

Articulo científicoThe Siamese fighting fish, Betta splendens, and the blue gourami, Trichopodus trichopterus, are two closely related air-breathing anabantoid fishes. B. splendens is a sedentary facultative air breather frequenting often hypoxic waters, whileT. trichopterusisamoreactiveobligatory air-breather inhabiting betteroxygenated waters. Despite their close taxonomic relationship, previous studies have shown inter-specific differences in both physiological and morphological plasticity. Consequently, we hypothesized that B. splendens would have the higher blood oxygen affinity characteristics typical of more hypoxia-tolerant fishes. Whole blood oxygen equilibrium curves were determined at 27°C and pHs of 7.62, 7.44 and 7.25. At a pH of 7.62, the blood O2 affinity (P50) ofB. splendens was just 2.9mmHg, while that of T. trichopterus was ~5 times higher at 14.7mmHg. There were no significant differences in P50 between males and females in either species. The Bohr coefficient in B. splendens and T. trichopterus was −1.79 and−0.83, respectively. B. splendens, unlike T. trichopterus, showed a large Root effect. Hills cooperatively coefficient, n, was ~2 in both species, indicating a significant binding cooperative between oxygen and hemoglobin. Collectively, these differences in blood O2 transport characteristics in these two closely related species are likely correlated with the differing habitats in which they breed and inhabit as adults, as well as different activity levels. Finally, the very high blood O2 affinity of B. splendens is not extraordinary among air-breathing fish, as revealed by a review of the literature of blood oxygen affinity in airbreathing fishes.This work was support by US National Science Foundation Operating Grant1025823. The UAEMgrants “Collaboration Networkin Comparative Ecophysiology of Vertebrates” PRODEP 11067 and “Scientific Research, Innovation, and Development” 4503/2018/CI also provided support

A Three-Dimensional Functional Assessment of Heart and Vessel Development in the Larva of the Zebrafish (Danio Rerio)

There has been considerable recent interest in the development of the circulation in the zebrafish. Optical techniques typically used to visualize changes in heart size allow measurement of stroke volume during early vertebrate development, but this approach is complicated in zebrafish larvae because of the heart\u27s irregular shape and its significant change in morphology during the first 6 d of development. By use of a three-dimensional integration of the early zebrafish heart and vessels, we have greatly reduced measurement error of stroke volume and cardiac output and have determined the cross-sectional growth of major vessels in the developing zebrafish larvae. A dramatic 500%-600% increase in cardiac output (from 10 to 50-60 nL min(-1)) occurs on days 5 and 6 postfertilization in Danio rerio. Cross-sectional area of key vessels (dorsal artery, caudal artery, dorsal vein) as well as between-individual variation significantly decreased over the first 6 d of development. Associated with the decrease in cross-sectional area is a significant increase in red blood cell velocity on days 5 and 6 postfertilization. Together, the three-dimensional data of the cardiac and vascular systems have shown that the most profound physiological and developmental changes occur in days 5 and 6, which corresponds with the appearance of the adult form of the heart and the transition from diffusive to convective O-2 supply to internal tissues

Estudio fisiológico de larvas de peces: retos y oportunidades

Physiological studies of larval fishes have lagged far behind those of adults, yet offer tremendous opportunities for expanding our knowledge of the basic biology of both marine and freshwater fishes. Physiological studies of larval fishes can also improve research and management in areas of applied science, such as aquaculture, fisheries, and environmental assessment. Additionally, larval fishes can be highly effective as general animal models for understanding evolution, development and disease processes in vertebrates. While the small size of larval fishes may initially seem to preclude detailed physiological measurements, physiologists have taken advantage of larval transparency and permeability to drugs and toxins to collect many forms of quantitative physiological data. In this essay we present a number of microtechniques currently employed in larval fish to study the cardiovascular, muscular, neurological, and ionoregulatory systems. Several interesting phenomena, including allometry, developmental plasticity and epigenetic effects, are then discussed from the perspective of the specific contributions that have been or can be made by studies of fish larvae. Ultimately, the integration of larval fish physiology with studies of morphology and behaviour, is both highly feasibly and likely to strengthen basic and applied research in fishes.Los estudios de fisiología en larvas de peces, están mucho más atrasados que los de peces adultos, sin embargo ofrecen enormes oportunidades para ampliar nuestro conocimiento sobre la biología básica de peces marinos y de agua dulce. Éstos también pueden mejorar la investigación y gestión en ciertas áreas de la ciencia aplicada, como la acuicultura, pesquerías y estudios ambientales. además, las larvas de peces pueden ser eficaces como modelos animales para comprender la evolución, el desarrollo y los procesos de enfermedades en vertebrados. mientras que su pequeño tamaño pudiera aparentar la imposibilidad de obtener medidas fisiológicas detalladas, los fisiólogos han aprovechado la transparencia larval y la permeabilidad a las drogas y toxinas para obtener diversas formas de datos fisiológicos cuantitativos. en este ensayo, presentamos un número de microtécnicas empleadas actualmente en larvas de peces, para estudiar los sistemas cardiovascular, muscular, neurológico y de regulación iónica. Varios fenómenos interesantes, incluyendo la alometría, plasticidad del desarrollo y los efectos epigenéticos, se discuten desde la perspectiva de las contribuciones específicas, existentes o potenciales de los estudios en larvas de peces. en última instancia, la integración de la fisiología en las larvas de peces, con los estudios de morfología y comportamiento, no sólo son altamente factibles, sino una probable pieza clave en la investigación básica y aplicada en peces

Cardiac and Metabolic Physiology of Early Larval Zebrafish (Danio rerio) Reflects Parental Swimming Stamina

Swimming stamina in adult fish is heritable, it is unknown if inherited traits that support enhanced swimming stamina in offspring appear only in juveniles and/or adults, or if these traits actually appear earlier in the morphologically quite different larvae. To answer this question, mature adult zebrafish (Danio rerio) were subjected to a swimming performance test that allowed separation into low swimming stamina or high swimming stamina groups. Adults were then bred within their own performance groups. Larval offspring from each of the two groups, designated high (LHSD) and low stamina-derived larvae (LLSD), were then reared at 27°C in aerated water (21% O2). Routine (fH,r) and active (fH,a) heart rate, and routine (Ṁo2,r) and active (Ṁo2,a) mass-specific oxygen consumption were recorded from 5 days post fertilization (dpf) through 21 dpf, and gross cost of transport and factorial aerobic metabolic scope were derived from Ṁo2 measurements. Heart rate generally ranged between 150 and 225 bpm in both LHSD and LLSD populations. However, significant (P < 0.05) differences existed between the LLSD and LHSD populations at 5 and 14 dpf in fH,r and at days 10 and 15 dpf in fH,a. Ṁo2,r was 0.04–0.32 μmol mg−1 h−1, while Ṁo2,a was 0.2–1.2 μmol mg−1 h−1. Significant (P < 0.05) differences between the LLSD and LHSD populations in Ṁo2,r occurred at 7, 10, and 21 dpf and in Ṁo2,a at 7 dpf. Gross cost of transport was ∼6–10 μmol O2·μg−1 m−1 at 5 dpf, peaking at 14–19 μmol O2 μg−1 m−1 at 7–10 dpf, before falling again to 5–6 μmol O2 μg−1 m−1 at 21 dpf, with gross cost of transport significantly higher in the LLSD population at 7 dpf. Collectively, these data indicate that inherited physiological differences known to contribute to enhanced stamina in adult parents also appear in their larval offspring well before attainment of juvenile or adult features

Dynamics of Epigenetic Phenomena: Intergenerational and Intragenerational Phenotype 'Washout'

This review contains a discussion of epigenetic dynamics in comparative biology with a focus on a more organismal level perspective, befitting of comparative physiology, that considers complex phenotypic changes

Role of Hypoxia in the Evolution and Development of the Cardiovascular System

Article on the role of hypoxia in the evolution and development of the cardiovascular system