Variaciones en la alimentación y cambios de forma de un pejesapo de arrecife temperado durante la ontogenia temprana

The majority of rocky reef fishes have complex life cycles, involving transition from a pelagic to a benthic environment. This means that as they grow, their morphology, behaviour and feeding habits must change. Therefore, shape changes occurring during early development of these fishes will be related to diet changes. The clingfish Sicyases sanguineus was selected for this study, because it displays a noticeable variation in shape from pelagic larvae to juvenile stage, and it is expected that diet composition will change as well. The pattern of shape changes was studied using geometric morphometrics. A set of 9 landmarks were digitized in 159 larval and juvenile fish and the same specimens were used for gut content analysis. Allometric growth was most prominent early in the ontogeny, from 4 to 12 mm. Morphology changed from a thin and hydrodynamic shape to a more robust and deeper body prior to settlement. The diet of the clingfish during larval stages showed preferences for a variety of copepod stages. As individual grows the ingested prey volume increases, but not the number and width of prey. A partial least square analysis showed low covariance between shape changes and diet composition changes in prey number and volume, suggesting that the two processes were temporally decoupled. The biggest shape changes, a lengthening of the visceral cavity and a flattening of the head, occurred up to 12 mm standard length, while the largest feeding differentiation, shifting from copepods to microalgae, occurred after 16 mm. Results suggest that shape changes precede trophic changes in this clingfish species during the transition from a pelagic to a benthic habitat.La mayoría de los peces de arrecifes rocosos tienen ciclos de vida complejos, que involucran la transición de un ambiente pelágico a uno bentónico. Esto significa que a medida que un pez crece, su morfología, conducta y alimentación cambian. Por lo tanto, los cambios de forma que ocurren durante la ontogenia temprana estarán relacionados con los cambios dietarios en peces de arrecifes rocosos. Se seleccionó el pejesapo Sicyases sanguineus para este estudio porque presenta una notable variación en forma desde la larva pelágica al estado juvenil, y es esperable que la composición dietaria también cambie. El patrón de cambios de forma fue estudiado usando morfometría geométrica. Se digitalizó un total de 9 landmarks en 159 larvas y juveniles, y los mismos individuos se usaron para análisis de contenido estomacal. El crecimiento alométrico fue mayor al comienzo del desarrollo ontogenético, entre 4 y 12 mm. La forma cambió de delgada e hidrodinámica, a más robusta y profunda antes del asentamiento. La dieta de las larvas de pejesapo mostró preferencia por diferentes estados de desarrollo de copépodos. A medida que los individuos crecieron, se incrementó el volumen de las presas ingeridas, pero no el número o ancho de ellas. Un análisis de Cuadrados Mínimos Parciales mostró baja covarianza entre los cambios morfológicos y dietarios en número y volumen de presas, sugiriendo que ambos procesos están temporalmente desacoplados. Los mayores cambios morfológicos ocurrieron antes de los 12 mm, un alargamiento de la cavidad visceral y un aplanamiento de la cabeza, mientras que la mayor diferenciación dietaria ocurrió después de los 16 mm, cambiando de copépodos a macroalgas. Esto sugiere que los cambios morfológicos preceden a los cambios en dieta en esta especie de pejesapo durante la transición de un hábitat pelágico a uno bentónico

Hábitos alimentarios y superposición de la dieta durante el desarrollo larval de dos blanquillos (Pisces: Pinguipedidae)

Two species of sandperch (Pinguipedidae: Perciformes), Prolatilus jugularis and Pinguipes chilensis, inhabit the coastal waters of the South Pacific. Both species have pelagic larvae with similar morphology, but their diet preferences are unknown. Diet composition, feeding success, trophic niche breadth and dietary overlap were described during larval stages for both species. In the austral spring, larval P. jugularis (3.83-10.80 mm standard length [SL]) and P. chilensis (3.49-7.71 mm SL) during their first month of life had a high feeding incidence ( > 70%) and fed mostly on copepod nauplii ( > 80% IRI), Rhincalanus nasutus metanauplii and Paracalanus indicus copepodites. The number of prey ingested was low (mean: 4-5 prey per gut) and independent of larval size; total prey volume and maximum prey width increased as larvae grew. Mouth opening and ingested prey were greater in larval P. jugularis than in P. chilensis, leading to significant differences in prey composition among larval species, in terms of prey number and volume. Pearre’s trophic niche breadth was narrow for both species (0.159±0.07 for P. jugularis; 0.156±0.03 for P. chilensis) and independent of larval size. Dietary overlap was high inter- and intra-species in larvae with a mouth gape 70%) y se alimentan principalmente de nauplii de copépodos ( > 80%IRI), metanauplii de Rhincalanus nasutus y copepoditos de Paracalanus indicus. El número de presas ingeridas fue bajo (media: 4-5 presas por estómago) e independiente del tamaño larval; el volumen total de presas y el ancho máximo de las presas se incrementó a medida que crecían las larvas de ambas especies. El largo de la mandíbula y el tamaño de las presas fue más grande en larvas de P. jugularis comparado con las de P. chilensis. Esto generó diferencias significativas en la composición de las presas entre especies, en términos de número y volumen de las presas ingeridas. La amplitud del nicho trófico de Pearre fue bajo para ambas especies (0.159±0.07 para P. jugularis; 0.156±0.03 para P. chilensis) e independiente del tamaño larval. La superposición dietética fue alta inter e intra-especies en aquellas larvas con apertura bucal < 900 μm. Estos resultados sugieren la importancia relativa de ambas especies como consumidores primarios de la trama pelágica en ambientes costeros con arrecifes rocosos

Larvae of Dactylopsaron dimorphicum (Perciformes: Percophidae) from oceanic islands in the southeast Pacific

Percophids are a family of small marine benthic fishes common over soft bottoms from inshore to the outer slopes in tropical to temperate regions of the Atlantic and in the Indo-West and southeast Pacific (Reader and Neira, 1998; Okiyama, 2000). Five species belonging to four genera have been recorded around the Salas y Gómez Ridge in the southeast Pacific, all of which are endemic to the area except for Chrionema chryseres, a species which also occurs off the Hawaiian Islands and Japan (Parin, 1985, 1990; Parin et al., 1997). Of these five species, larval stages have been described only for Osopsaron karlik and Chrionema pallidum (Belyanina 1989, 1990)

Comportamiento reproductivo y desarrollo de los estadios tempranos del bagre marino Aphos porosus, de la bahía de Valparaíso, Chile

Con el objetivo de estudiar el comportamiento reproductivo y describir los huevos y larvas del bagre Aphos porosus (Pisces: Batrachoididae), se realizaron observaciones durante 6 temporadas de desove en la zona intermareal rocoso de Montemar, bahía de Valparaíso, Chile. Se mantuvieron peces adultos en el laboratorio y se controló el desarrollo de huevos y larvas. También se realizó la fertilización artificial de huevos en el laboratorio. Se observó la llegada de los machos a la costa a partir de octubre, seguidos de las hembras en noviembre y diciembre de cada año. Los huevos fueron adheridos a las paredes verticales o inferiores de las piedras y grietas de las pozas del intermareal de Montemar y en las paredes de los estanques. Su diámetro fue de 5,3 ± 0,3 mm. La eclosión se produjo a los 18 d a 18,6°C y a los 21 d a 16,3°C. Las larvas recién eclosionadas midieron en promedio 4,8 mm de longitud total (LT) (rango entre 4,3 a 5,1 mm LT) y realizaron parte de su desarrollo adheridas al sustrato por el saco vitelino. Antes de consumir completamente el vitelo, las larvas ya presentaban el patrón de pigmentación y la forma del cuerpo similar a la de los juveniles. Al terminar de absorber el vitelo, las larvas midieron 20,5 a 24,0 mm LT y se liberaron del sustrato entre los 60 y 65 d de edad. Este trabajo constituye un aporte sobre aspectos no descritos del comportamiento reproductivo y la ontogenia de A. porosus, dentro del conjunto de especies de peces de la costa de Chil

Comportamiento del cardumen de preasentados de un pez rocoso en aguas someras. ¿Está relacionado con las condiciones ambientales?

This study evaluates the swimming behaviour of pre-settled fish larvae of the triplefin Helcogrammoides chil­ensis (Tripterygiidae) in relation to local environmental conditions. Larval aggregations were recorded on rocky reefs off central Chile during the austral summer of 2014 and 2016 to describe their swimming behaviour (i.e. solitary, shoaling, schooling) and relate it to in situ water temperature, wind stress, wind speed and turbulence. Shoaling and solitary behaviour were influenced only by wind-induced turbulence in 2014 and by seawater temperature and wind stress in 2016. Schooling behaviour was not influenced by any of the environmental variables. In situ swimming behaviour of fish larvae has been little investigated, and this work proposes a non-invasive in situ methodology for studying fish larval behaviour.Este estudio evalúa el comportamiento natatorio de larvas pre-asentadas del trombollito de tres aletas Helcogram­moides chilensis (Tripterygiidae) en relación con las condiciones ambientales locales. Para describir su comportamiento natatorio (i.e. solitario, agregación y cardumen) los grupos de larvas fueron grabadas en video en el intermareal rocoso en Chile central, durante el verano austral de 2014 y 2016. Luego, estas conductas fueron relacionadas con la temperatura del agua de mar in situ, estrés y velocidad del viento y turbulencia. Los comportamientos solitarios y agregados fueron afectados solamente por la turbulencia inducida por el viento en el 2014, y por la temperatura del agua de mar y estrés del viento en 2016. El comportamiento de cardumen no fue influido por ninguna variable ambiental. El comportamiento natatorio in situ de larvas de peces ha sido escasamente estudiado, por lo tanto, este trabajo propone una metodología no invasiva in situ para estudiar el comportamiento de las larvas de peces

Larval fish assemblages in two nearshore areas of the Humboldt Current System during autumn-winter in northern Chile

This paper presents an analysis of spatial and temporal patterns in the fish larvae composition of two geographically adjacent nearshore areas within the Humboldt Current System (HCS), northern Chile. Five surveys were performed at Isla Santa María (ISM) and Punta Coloso (COL), Mejillones Peninsula. Ichthyoplankton were collected every 15 days in 2014 during the austral autumn-winter (May to August). A total of 412,410 fish larvae belonging to 36 taxa were identified, a high abundance compared with other HCS regions. Data also revealed similarities in species recorded compared with central Chile as well as differences compared with central Peru; a number of families were shared between these HCS regions and other systems (e.g., Canarias Current System). ISM was dominated by intertidal-subtidal species (e.g., Helcogrammoides cunninghami), while Engraulis ringens was most abundant at COL. Several species were positively correlated with dissolved oxygen (e.g., Auchenionchus microcirrhis), as well as temperature and Ekman transport (e.g., Sebastes oculatus), while the presence of others is negatively related to the same environmental parameters (e.g., Graus nigra). Results suggest that larvae differently utilize these two areas as a refuge or for feeding, and that adults might be coupling their spawning periods with short-term oceanographic features. Larval fish assemblages of nearshore areas in northern Chile are described here for the first time and highlight the important role of these two areas in the early developmental stages of fish species

Observations on the ontogeny of butterfish Stromateus stellatus larvae (Pisces: Stromateidae) off central Chile

Although larvae of the starry butterfish Stromateus stellatus (Family Stromateidae) are often observed in coastal waters of the southeastern Pacific Ocean, there is no formal description of the species’ early development. Using ichthyoplankton samples collected off central Chile, the larval development, including observations on osteology of late postflexion stage larvae, and temporal differences in larval densities in nearshore waters are described. Preflexion larvae have a short, rounded snout and a distinctive pigment pattern. Notable transformations throughout the development from early preflexion to postflexion are the increase in preanal length from less than 40 to more than 50% of body length (BL) and in body depth from 5 to 33% BL. Initially, larvae develop 3 melanophores on the dorsal contour of the body, small melanophores at the jaw angle, and a row along the ventral margin of the tail. Large melanophores dorsal and ventral to the gut, intestine, and above the swim bladder are also present in early preflexion. After notochord flexion, larvae develop light pigmentation on the sides of the tail, and heavy pigmentation on the head and trunk. The larvae share the general shape of the family, with a body that increases notably in depth and preanal length during development; they present characteristic pigmentation that differentiates them from larvae of related species. The larvae were recorded in low density (less than 6 ind. 100 m-3) in the nearshore during mid-spring (October) and early summer (late December until mid-January) off central Chile. The occurrence of the larvae in the plankton recorded in central Chile is consistent with information from literature of larval distribution and reproductive activity in adults

Feeding ecology of fish larvae from Chilean Patagonia during austral winter

Feeding habits of the ichthyoplankton from Chilean Patagonia (44-46°30’S) were studied during June-July 2012 (austral winter). Ichthyoplankton assemblage was composed by 10 species, with low abundance (3.8 to 16.73 ind. 1000 m-3). Most abundant larvae were Maurolicus parvipinnis, Leptonotus blainvilleanus and Sprattus fuegensis. These three species fed mainly on calanoid copepodites, Paracalanus indicus and Calanus sp. copepodites, and cyphonautes. Trophic overlap among dominant fish larvae was high (Schoener’s D &gt; 0.69) and no significant differences were detected in prey composition and size. Therefore, no resource partitioning occurred in planktonic fish larvae during winter 2012 in Chilean Patagonia

Desarrollo larval y variación de la forma de la doncellita Myxodes viridis (Teleostei: Clinidae)

Larval development and shape ontogeny of the kelpfish Myxodes viridis (Clinidae) are described for the first time. A total of 214 individuals ranging between 3.51 and 23.09 mm standard length collected off central Chile were assessed employing classic and geometric morphometrics, illustration with camera lucida and a double-staining technique for cartilaginous and bone structure observation. Based on characteristics such as yolk sac presence and fin formation, six stages of larval development were differentiated: yolk sac, preflexion, flexion, early postflexion, late postflexion and juvenile. Shape changes during development are subtle and occur smoothly, being more significant in the head and preanal length, and ontogenetic allometry accounts for almost 15%. Cartilage formation takes place first at the branchial arches and cranium; then hypural, haemal and neural arches are consecutively formed. Bony structure ossification occurs late in the development. Vertebral centra ossify directly, without cartilaginous matrix replacement.Se describe por primera vez el desarrollo larval y la ontogenia de la forma de la doncellita Myxodes viridis (Clinidae). Se utilizaron 214 individuos, que variaron entre 3.51 y 23.09 mm LE, recolectados frente a Chile central, para describir la morfometría clásica, geométrica, ilustraciones con cámara lucida y observación de estructuras cartilaginosas y óseas teñidas. Se diferenciaron 6 estados de desarrollo larvario basada en características como la presencia de saco vitelino y la formación de aletas: larva con saco vitelino, preflexión, postflexión temprana, postflexión tardía y juvenil. Los cambios de forma a través del desarrollo fueron sutiles y cambiaron levemente, siendo más significativos en la cabeza y longitud preanal y la alometría ontogenética correspondió a un 15% de los cambios de forma. La formación de cartílago ocurre primero en los arcos branquiales y el cráneo, luego se forman consecutivamente los elementos hipurales y los arcos hemales y neurales. La osificación de las estructuras ocurre tarde en el desarrollo. Los centros vertebrales se osifican directamente, sin reemplazo de la matriz cartilaginosa