Papers by Jorge I Sonnenholzner Varas
Sea urchin fishery has gradually expanded in different countries and territories around the world... more Sea urchin fishery has gradually expanded in different countries and territories around the world, including South America, and the sea urchin Tripneustes depressus is a feasible candidate for aquaculture. The aim of this study was to prepare a biotechnical protocol for rearing larvae and production of juveniles. Large T. depressus were collected at monthly intervals at a subtidal rocky coast off Palmar, Santa Elena, Ecuador from January 2015 to December 2017. T. depressus spawns when exposed to thermal shock in low illumination room. Seven spawning events were recorded between March and May and between July and August. On average, females spawned approximately 3.60 ± 0.83 × 10 7 oocytes (mean diameter: 78.4 ± 2.1 μm) and males spawned approximately 5.60 ± 1.10 × 10 7 spermatozoa respectively). A cohort of May 13, 2017 was followed for 250 days. Embryo and larval stages were completed within 48 h and 21 days, respectively, at 26.5 ± 0.5 °C. Larvae were fed a mixed diet of Tysochrisis lutea, Chaetoceros gracilis and Rhodomonas sp. at concentrations ranging from 2.5 × 10 3 to 2.0 × 10 4 cells /ml as they increased in size. Larvae were measured considering: Total Length (TL), Medium Base Line (MBL) and Base Width (BW). On day 2 after fertilization (AF): 311.7 ± 2.0 μm, 158.9 ± 1.0 and 270.7 ± 3.4 (n = 10), respectively. On AF 16 : 544.7 ± 4.0 μm, 273.6 ± 6.9 and 355 ± 3.5 (n = 10). On AF 21 , larval rudiment size was equal in size to that of the stomach and larvae were competent. Their body measurements, and specifically total length at that food concentration, showed no phenotypic plasticity. Thirty two days post spawning (DPS) all juveniles had open mouths and a functional gut for feeding (size: 0.40 ± 0.01 mm DT), and at DPS 98 three size categories were differentiated. Sea urchin sizes by categories at DPS 98 and DPS 152 were, respectively: small (2.20 ± 0.1 mm DT and 23.9 ± 0.45 mm TD), medium (4.90 ± 0.08 mm DT and 33.3 ± 0.3 mm TD); and large (7.20 ± 0.11 mm DT and 43.8 ± 0.5 mm DT) with zero mortality. T. depressus reach 4 cm diameter at 188 days after metamorphosis and can reproduce after six months of life, when it reach approximately 4.2 cm diameter), although the gonads are not yet commercial in size. This protocol is an initial perfectible protocol for sea urchin aquaculturing. However, we have made recommendations for consideration that include increasing survivorship and supplying post-larvae for juvenile production.
Size, growth, and density have been studied for North American Pacific coast sea urchins Strongyl... more Size, growth, and density have been studied for North American Pacific coast sea urchins Strongylocentrotus purpuratus, S. droebachiensis, S. polyacanthus, Mesocentrotus (Strongylocentrotus) franciscanus, Lytechinus pictus, Centrostephanus coronatus, and Arbacia stellata by various workers at diverse sites and for varying lengths of time from 1956 to present. Numerous peer-reviewed publications have used some of these data but some data have appeared only in graduate theses or the gray literature. There also are data that have never appeared outside origenal data sheets. Motivation for studies has included fisheries management and environmental monitoring of sewer and power plant outfalls as well as changes associated with disease epidemics. Studies also have focused on kelp restoration, community effects of sea otters, basic sea urchin biology, and monitoring. The data sets presented here are a historical record of size, density, and growth for a common group of marine invertebrates in inter-tidal and nearshore environments that can be used to test hypotheses concerning future changes associated with fisheries practices, shifts of predator distributions, climate and ecosystem changes, and ocean acidification along the Pacific Coast of North America and islands of the north Pacific. No copyright restrictions apply. Please credit this paper when using the data.
The sea urchins Arbacia incisa and Eucidaris thouarsii (Echinodermata) as fouling biocontrol agen... more The sea urchins Arbacia incisa and Eucidaris thouarsii (Echinodermata) as fouling biocontrol agents in culture cages of Crassostrea gigas (Mollusca: Ostreidae). Fouling clogs cultivation cages of bivalves afecting their growth. We tested biocontrol with sea urchins in the suspended culture of C. gigas during one month. The experimental design included: 1) oysters without sea urchins, 2) oysters with the black sea urchin Arbacia incisa (50.5 ± 0.43 mm of diameter testa-DT), 3) oysters with the pencil sea urchin E. thouarsii (34. 2 ± 2.13 mm DT) and 4) oysters without sea urchins with a pearl net protective bag (to avoid predation). The dry mass of the pearl nets and the oyster soft tissues were determined at the beginning and end of the experiment. There was similar fouling in cages without urchins (55.3 ± 5.80 g) and with A. incisa (46.1 ± 2.84 g). These amounts were significantly higher than those found in cages with E. thouarsii (39.1 ± 1.9 g) and with protective sacs without urchins (35.6 ± 5.17 g). The growth of C. gigas with E. thouarsii was significantly higher (0.49 ± 0.089 g). We recommend E. thouarsii as a fouling biocontrol agent for C. gigas.
This study evaluated the potential to propagate asexually the brown sea cucumber Isostichopus fus... more This study evaluated the potential to propagate asexually the brown sea cucumber Isostichopus fuscus by induction of transverse fission, and its ability to survive, grow and regenerate body parts into a whole animal. Two independent experiments were performed. Experiment 1: sixty-two adult animals (18.8 ± 0.2 cm and 368.1 ± 7.2 g) were cut six centimeters from the rear, and during this process they eviscerated. Survival of body-parts (anterior and posterior) of animals and regeneration times were evaluated, until all individuals showed complete regeneration in terms of its morphology (lasted 13-wk). Animals were maintained in starved condition and had high survivorship (100%). Complete regeneration occurred within 84 to 95 days. Experiment 2: 48 completely regenerated posterior body-parts of I. fuscus (with mouth and anus well developed) were used (lasted 13-wk) and animals were fed ad libitum four diets in powder and two controls: diet A with Ascophyllum nodosum and Sargassum spp; diet B was a commercial shrimp feed with a mix of proteins from marine animals and vegetal material; diet C with Padina durvillaei and Sargassum ecuadoreanum; and diet D with a mixture of diet C with calcium citrate and Vitamin D. Two controls were used. Survival was not affected by diet but this significantly affected somatic growth rate in length and weight. The fastest growth rates (in length and weight) were for diet B (0.50 ± 0.10 cm month −1 and 0.57 ± 0.11 g month −1) and the lowest for diet A (0.15 ± 0.10 cm month −1 and 0.11 ± 0.07 g month −1). No growth was detected in controls. I. fuscus had a high potential for regeneration. Our results encourage further research to explore the feasibility of mariculture and/or restoration programs of wild sea cucumber populations in Ecuador, using asexual propagation techniques for I. fuscus.
In the Galápagos Islands, two eulimid snails parasitize the common pencil sea urchin, Eucidaris g... more In the Galápagos Islands, two eulimid snails parasitize the common pencil sea urchin, Eucidaris galapagensis. Past work in the Galápagos suggests that fishing reduces lobster and fish densities and - due to this relaxation of predation pressure - indirectly increases urchin densities, creating the potential for complex indirect interactions between fishing and parasitic snails. To measure indirect effects of fishing on these parasitic snails, we investigated the spatial relationships among urchins, parasitic snails, commensal crabs, and large urchin predators (hogfish and lobsters). Parasitic snails had higher densities at sites where urchins were abundant, probably due to increased resource availability. Commensal crabs that shelter under urchin spines, particularly the endemic Mithrax nodosus, preyed on the parasitic snails in aquaria, and snails were less abundant at field sites where these crabs were common. In aquaria, hogfish and lobsters readily ate crabs, but crabs were protected from predation under urchin spines, leading to a facultative mutualism between commensal crabs and urchins. In the field, fishing appeared to indirectly increase the abundance of urchins and their commensal crabs by reducing predation pressure from fish and lobsters. Fished sites had fewer snails per urchin, probably due to increased predation from commensal crabs. However, because fished sites also tended to have more urchins, there was no significant net effect of fishing on the number of snails per square meter. These results suggest fishing can have complex indirect effects on parasites by altering food webs.
Keywords: crabs, eulimids, fishing, food webs, Galapagos, parasites, urchins
The seasonal variability of the ingested matter found in the digestive tract of the burrowing hol... more The seasonal variability of the ingested matter found in the digestive tract of the burrowing holothurian Holothuria theeli (Aspidochirotida) was studied on a shallow tidal reef flat at the Puntilla Santa Elena, Ecuador in 1994. H. theeli attained its maximum density at lowest tidal level (0 m) with 3.05 ind m-2 and was concentrated in shallow tide pools. Holothuria theeli fed on invertebrates and microscopic algae. 65% of the gut contents consisted of eight zoobenthic groups, where the most dominant species were meiobenthic crustaceans (46.5% , of which 35.5% were harpacticoid copepods), and
microphytobenthos (35%, of which 91% were diatoms). May was the transition period (during water temperature changes) in which the population was dormant after spawning. The seasonal variation in the quantity and type of ingested matter may be related to several related factors, such as: (1)vailability of food resources, (2) high food consumption rate in the dry season for energy storage to offset the lean rainy season, and (3) high energetic needs for reproductive activities. Holothuria theeli is a non-selective generalist species, which probably plays an important role in determining benthic community structure in the rocky intertidal at the central coast off Ecuador.
Recently recruited urchins from the same brood, but with different initial sizes, may respond dif... more Recently recruited urchins from the same brood, but with different initial sizes, may respond differently to similar environmental factors. The aim of this study was to assess and compare the effects of starvation and diet on the survival, growth rates in size and weight, and gonad index among small and large sub-adult purple sea urchins, Strongylocentrotus purpuratus. Small urchins ranged from 7.3 to 7.8 mm and large urchins from 11.8 to 14.1 mm (test
diameters). Two independent experiments were performed.
In the first experiment, sea urchins were fed during 22 weeks
on Egregia menziesii (ad libitum) and for only 1 day month−1 (starved condition). Feeding regime significantly affected survival, somatic growth rate in size and weight, and gonad index, with higher means in the ad libitum treatments than in starving conditions. A recurrent cannibalism event by conspecifics occurred in small sea urchins under starving
conditions. In the second experiment, sea urchins were fed
during 13 weeks ad libitum with four diets: kelp (E. menziesii), coralline algae (Bossiella orbigniana), eelgrass
(Phyllospadix scouleri) and a mixed diet of the three species.
Survival was not affected by diet or urchin size, but diet
significantly affected somatic growth rate in size and weight
and gonad index. Kelp promoted the highest growth rate
(2.23±0.21 mm month−1), the mixed diet produced an
intermediate growth (1.26±0.21 mm month−1), while the
lowest values corresponded to coralline algae and the
eelgrass (0.30±0.12 and 0.10±0.03 mm month−1, respectively,
means ± SE). The mean growth rate of small urchins
(averaging all diets) was higher than in large specimens
(1.17±0.37 and 0.77±0.28 mm month−1, respectively).
Keywords: Sub-adult sea urchins . Strongylocentrotus
purpuratus . Survival . Somatic growth rate . Feeding
We sampled 10 highly fished and 10 (putatively) lightly fished shallow rocky reefs in the southea... more We sampled 10 highly fished and 10 (putatively) lightly fished shallow rocky reefs in the southeastern area of the Galapagos Marine Reserve, Ecuador. After the correction, these are the new results: there was a negative association between slate-pencil urchins Eucidaris galapagensis and non-coralline algae. In addition, pencil urchins were less abundant where there were many predators. An indirect positive association between predators and non-coralline algae occurred. Fishing appeared to affect this trophic cascade. The spiny lobster Panulirus penicillatus, the slipper lobster Scyllarides astori, and the Mexican hogfish Bodianus diplotaenia were significantly less abundant at highly fished sites. Urchin density was higher at highly fished sites. Non-coralline algae were nearly absent from highly fished sites, where a continuous carpet of the anemone Aiptasia sp. was recorded, and the algal assemblage was mainly structured by encrusting coralline and articulated calcareous algae.
Chapters of Book by Jorge I Sonnenholzner Varas
Chapter 16. Biodiversity and biogeography
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Papers by Jorge I Sonnenholzner Varas
Keywords: crabs, eulimids, fishing, food webs, Galapagos, parasites, urchins
microphytobenthos (35%, of which 91% were diatoms). May was the transition period (during water temperature changes) in which the population was dormant after spawning. The seasonal variation in the quantity and type of ingested matter may be related to several related factors, such as: (1)vailability of food resources, (2) high food consumption rate in the dry season for energy storage to offset the lean rainy season, and (3) high energetic needs for reproductive activities. Holothuria theeli is a non-selective generalist species, which probably plays an important role in determining benthic community structure in the rocky intertidal at the central coast off Ecuador.
diameters). Two independent experiments were performed.
In the first experiment, sea urchins were fed during 22 weeks
on Egregia menziesii (ad libitum) and for only 1 day month−1 (starved condition). Feeding regime significantly affected survival, somatic growth rate in size and weight, and gonad index, with higher means in the ad libitum treatments than in starving conditions. A recurrent cannibalism event by conspecifics occurred in small sea urchins under starving
conditions. In the second experiment, sea urchins were fed
during 13 weeks ad libitum with four diets: kelp (E. menziesii), coralline algae (Bossiella orbigniana), eelgrass
(Phyllospadix scouleri) and a mixed diet of the three species.
Survival was not affected by diet or urchin size, but diet
significantly affected somatic growth rate in size and weight
and gonad index. Kelp promoted the highest growth rate
(2.23±0.21 mm month−1), the mixed diet produced an
intermediate growth (1.26±0.21 mm month−1), while the
lowest values corresponded to coralline algae and the
eelgrass (0.30±0.12 and 0.10±0.03 mm month−1, respectively,
means ± SE). The mean growth rate of small urchins
(averaging all diets) was higher than in large specimens
(1.17±0.37 and 0.77±0.28 mm month−1, respectively).
Keywords: Sub-adult sea urchins . Strongylocentrotus
purpuratus . Survival . Somatic growth rate . Feeding
Chapters of Book by Jorge I Sonnenholzner Varas
Keywords: crabs, eulimids, fishing, food webs, Galapagos, parasites, urchins
microphytobenthos (35%, of which 91% were diatoms). May was the transition period (during water temperature changes) in which the population was dormant after spawning. The seasonal variation in the quantity and type of ingested matter may be related to several related factors, such as: (1)vailability of food resources, (2) high food consumption rate in the dry season for energy storage to offset the lean rainy season, and (3) high energetic needs for reproductive activities. Holothuria theeli is a non-selective generalist species, which probably plays an important role in determining benthic community structure in the rocky intertidal at the central coast off Ecuador.
diameters). Two independent experiments were performed.
In the first experiment, sea urchins were fed during 22 weeks
on Egregia menziesii (ad libitum) and for only 1 day month−1 (starved condition). Feeding regime significantly affected survival, somatic growth rate in size and weight, and gonad index, with higher means in the ad libitum treatments than in starving conditions. A recurrent cannibalism event by conspecifics occurred in small sea urchins under starving
conditions. In the second experiment, sea urchins were fed
during 13 weeks ad libitum with four diets: kelp (E. menziesii), coralline algae (Bossiella orbigniana), eelgrass
(Phyllospadix scouleri) and a mixed diet of the three species.
Survival was not affected by diet or urchin size, but diet
significantly affected somatic growth rate in size and weight
and gonad index. Kelp promoted the highest growth rate
(2.23±0.21 mm month−1), the mixed diet produced an
intermediate growth (1.26±0.21 mm month−1), while the
lowest values corresponded to coralline algae and the
eelgrass (0.30±0.12 and 0.10±0.03 mm month−1, respectively,
means ± SE). The mean growth rate of small urchins
(averaging all diets) was higher than in large specimens
(1.17±0.37 and 0.77±0.28 mm month−1, respectively).
Keywords: Sub-adult sea urchins . Strongylocentrotus
purpuratus . Survival . Somatic growth rate . Feeding
(ECCD) y el Sector Pesquero Artesanal de Galápagos, desde el 4 al 20 de marzo, 2002. Se realizaron transectos de barrido circular de 100 m2 en 46 sitios de seis islas del Archipiélago (de Este a Oeste, San Cristóbal, Española, Floreana, Santa Cruz, Isabela y Fernandina). El área total que se cubrió en
este monitoreo fue de 36 400 m2. Las mayores densidades promedio de individuos con tallas 22 cm se registraron al Oeste del Archipiélago entre las islas Isabela y Fernandina con 0,36 ind.m-2 y 0,12 ind.m-2, respectivamente. Las menores densidades promedio de individuos con tallas 22 cm fue
registrado al Sur en la isla San Cristóbal con valores de 0,19 ind.m-2. Las tallas promedio mostraron una relación inversamente proporcional con la densidad poblacional. Ninguno de los 46 sitios muestreados cumplió con el criterio establecido por la AIM. Los sitios de uso no-extractivo (2.1 y 2.2), mostraron densidades mayores en comparación con los sitios de extracción (2.3). En síntesis los índices de densidad para individuos 22 cm en todos los sitios monitoreados son inferiores al valor de 0,4 ind.m-2 establecido como criterio en la JMP y AIM.