UCN-CEAZA
Coalescence in wild organisms of the intertidal population of Lessonia berteroana in northern Chile: management and sustainability effects.
Rodríguez, D., Oróstica, M., & Vásquez, J.
Lessonia berteroana is the subject of 85 % of the total harvest of Chilean brown seaweeds, representing close to 10 % of total kelp biomass worldwide harvested for alginic acid extraction. Frequent incidence of coalescent holdfasts was detected in natural populations, and this process gives rise to fused sporophytes. This study presents the coalescence events in natural populations in northern Chile. During 2011, in natural intertidal populations, 435 target sporophytes of different sizes were observed weekly and 63.90 % (278) showed physical signs of coalescent disks. We were able to distinguish five fusion modes depending on the number and size of each of the participant sporophytes and their spatial distribution. There was a progressive decrease of density and an increase in the number of stipes of each sporophyte over time. Two processes were recognized: active fusion of juvenile sporophytes and passive fusion of adult and senescent sporophytes. However, most of the coalescence processes were detected in juvenile sporophytes with a holdfast diameter of 0.5 to 2 cm. The minimum distance between pairs of coalescing sporophytes was 0.5 cm, and the maximum distance was 13 cm. For good harvesting practices, it is recommended that plants with over 20 cm holdfast diameter are harvested from natural populations because over this size, all of the plants have reproduced. Coalescence events would produce plants with legal size requirement; however, these plant units would not be reproductive, affecting the sustainability of this important coastal resource.
Año: 2013
Palabras claves: Lessonia berteroana population, Coalescence process, Management and sustainability.
Referencia APA: Rodríguez, D., Oróstica, M., & Vásquez, J. (2013). Coalescence in wild organisms of the intertidal population of Lessonia berteroana in northern Chile: management and sustainability effects. J Appl Phycol, 26(2), 1115-1122.
Host-use patterns and factors influencing the choice between anemone and urchin hosts by a caridean shrimp.
Ory, N., Dudgeon, & Thiel, M.
Small marine decapods often associate with other invertebrates in order to gain protection from predators. However, the factors that influence host choice by symbionts, such as shrimps, are poorly understood but may have important implications for the distribution and abundance of these mesoconsumers. In Hong Kong, the rhynchocinetid shrimp Rhynchocinetes brucei uses two alternative hosts: an urchin (Diadema setosum) and an anemone (Entacmaea quadricolor). We examined the association between R. brucei and its anemone and urchin hosts in the field and laboratory, investigating host choice and host fidelity. Underwater surveys on shallow rocky reefs in Hong Kong revealed that shrimps were rarely found outside refuges, such as crevices and holes, unless they were associated with anemones and urchins. Shrimps were more frequently associated with urchins than with anemones, although anemones were more abundant within the survey area. Host-choice experiments in the laboratory confirmed that, when given a choice, shrimps avoided open areas and associated with anemones, urchins or artificial refuges. Shrimps overwhelmingly chose urchins over artificial refuges, but did not show any clear preference for anemones over refuges. When offered a choice, shrimps displayed fidelity for their original host species (i.e. the host with which they were associated when collected from the field), suggesting that they imprinted upon the host. Host-imprinting may allow symbionts to efficiently relocate their original host species after separation (e.g. following nocturnal foraging trips) thereby, perhaps, reducing the risk of predation. However, host preference by R. brucei was facultative because shrimps would associate with an unfamiliar host when their original host was unavailable. This flexibility may allow shrimps to respond to local variability in host abundance.
Año: 2013
Palabras claves: Host-imprinting; Host selection; Refuge; Rocky reefs; Shrimp.
Referencia APA: Ory, N., Dudgeon, & Thiel, M. (2013). Host-use patterns and factors influencing the choice between anemone and urchin hosts by a caridean shrimp. Journal Of Experimental Marine Biology And Ecology, 449, 85-92.
Sea urchin Tetrapygus niger distribution on elevated surfaces represents a strategy for avoiding predatory sea stars
Urriago, J., Himmelman, J., & Gaymer, C.
We ran field experiments to examine whether the micro-distribution of the sea urchin Tetrapygus niger on elevated surfaces represents a strategy for limiting predation by the sea stars Heliaster helianthus and Meyenaster gelatinosus. Several lines of evidence supported this hypothesis. (1) A survey of the distribution of the urchin and the 2 sea stars showed that urchins occur mainly on elevated surfaces, and sea stars on low surfaces. (2) In trials involving simulated attacks, the time needed by the urchin to sever contact with the sea stars was 48% less on elevated surfaces than on the bottom. (3) In trials involving sustained simulated attacks (high predatory risk) the urchins could detach themselves from the elevated surfaces to avoid being eaten. Finally, tethering experiments indicated that the urchin had a higher survival rate on elevated than low surfaces. Our observations indicate that M. gelatinosus represents a stronger predatory threat to T. niger than H. helianthus.
Año: 2012
Palabras claves: Tetrapygus niger · Heliaster helianthus · Meyenaster gelatinosus · Predator−prey interactions · Aggregation · Distribution · Tethering
Referencia APA: Urriago, J., Himmelman, J., & Gaymer, C. (2012). Sea urchin Tetrapygus niger distribution on elevated surfaces represents a strategy for avoiding predatory sea stars. Marine Ecology Progress Series, 444, 85-95.
Effects of patch size and position above the substratum during early succession of subtidal soft-bottom communities.
Pacheco, A., Thiel, M., Oliva, M., & Riascos, J.
Early macrobenthos succession in small, disturbed patches on subtidal soft bottoms is facilitated by the arrival of post-larval colonizers, in particular by active and passive dispersers along the seafloor or through the water column. Using a field experiment at two contrasting sites (protected vs. exposed to wave action), we evaluated the role of (a) active and passive dispersal through the water column and (b) the influence of small-scale spatial variability during succession of subtidal macrobenthic communities in northern Chile. Containers of two sizes (surface area: small—0.12 m2 and large—0.28 m2) at two positions above the natural substratum (height: low—3 cm and high—26 cm) were filled with defaunated sediment, installed at two sandy sublittoral sites (7–9 m water depth) and sampled after 7, 15, 30, 60 and 90 days, together with the natural bottom sediment. The experiment took place during austral fall (from late March to early July 2010), when both larval and post-larval stages are abundant. At the exposed site, early succession was driven by similar proportions of active and passive dispersers. A sequence from early, late and reference communities was also evident, but container position and size affected the proportional abundance of dispersal types. At the protected site, the successional process started with abundant colonization of active dispersers, but toward the end of the experiment, the proportion of swimmer/crawlers increased, thus resembling the dispersal types found in the natural community. At this site, the position above the sediment affected the proportional abundance of dispersal types, but patch size had no effect. This study highlights that macrobenthic post-larvae can reach at least 26 cm high above the bottom (actively or passively, depending on site exposure), thus playing an important role during early succession of sublittoral soft bottoms. The active or passive use of the sediment–water interphase may also play an important role in the connectivity of benthic populations and in the recovery after large-scale disturbances of sublittoral habitats.
Año: 2012
Palabras claves: Colonization, Disturbance, Macrobenthos, Size effects, Recruitment, Active and passive dispersal, Humboldt, Current, System.
Referencia APA: Pacheco, A., Thiel, M., Oliva, M., & Riascos, J. (2012). Effects of patch size and position above the substratum during early succession of subtidal soft-bottom communities. Helgoland Marine Research, 66(4), 523-536.
Effects of predation and habitat structure on the abundance and population structure of the rock shrimp Rhynchocinetes typus (Caridea) on temperate rocky reefs.
Ory, N., Dudgeon, D., Dumont, C., Miranda, L., & Thiel, M.
Human disturbances, such as overfishing, may disrupt predator–prey interactions and modify food webs. Underwater surveys were carried out at six shallow-water reef barrens in temperate waters of northern-central Chile from October to December 2010 to describe the effects of predation, habitat complexity (low, medium and high) and refuge availability on the abundance and population structure of the rock shrimp Rhynchocinetes typus (Rhynchocinetidae), an important mesoconsumer on subtidal hard substrata. Three sites were within managed (restricted access) areas for fishermen, and three were unmanaged (open-access). Field observations and tethering experiments were conducted to examine the relationship between fish and shrimp abundances, and the relative predation rates on shrimps. Direct effects of predation on R. typus body-size distribution were examined from shrimps collected in the field and fish stomachs. The presence and the abundance of R. typus increased with habitat reef complexity and refuge availability. Shrimp abundance was negatively related to fish abundance in managed areas, but not in open-access areas, where shrimp densities were the highest. Also, predation rates and body-size distribution of shrimps were unrelated, although fish consumed more large shrimps than should be expected from their distribution in the field. R. typus occurred most often in shelters with wide openings, offering limited protection against predators, but providing potential aggregation sites for shrimps. Overall, direct effects of predation on shrimp densities and population structure were weak, but indirect effects on shrimp distribution within reefs appear to have been mediated through behavioural responses. Our study highlights the need to assess both numerical and behavioural responses of prey to determine the effects of predator loss on mesoconsumer populations.
Año: 2012
Palabras claves:
Referencia APA: Ory, N., Dudgeon, D., Dumont, C., Miranda, L., & Thiel, M. (2012). Effects of predation and habitat structure on the abundance and population structure of the rock shrimp Rhynchocinetes typus (Caridea) on temperate rocky reefs. Marine Biology, 159(9), 2075-2089.
Floating kelps in Patagonian Fjords: an important vehicle for rafting invertebrates and its relevance for biogeography.
Wichmann, C., Hinojosa, I., & Thiel, M.
Floating macroalgae are common dispersal vehicles for associated benthic invertebrates. In order to investigate the importance of kelp rafts for species dispersal in the Patagonian Fjord Region (PFR), the abundance and distribution pattern of floating kelps (Macrocystis pyrifera, Durvillaea antarctica) and of the invertebrate fauna associated with M. pyrifera were evaluated during austral spring of 2002–2005, 2008 and 2010. In the southernmost Magellan Region (MR), benthic M. pyrifera were additionally sampled to compare the community structures in both conditions. Floating kelps were abundant throughout the entire PFR, harbouring a diverse and abundant invertebrate fauna. The density of floating kelps increased towards the south. In the MR, a loss of species was observed between benthic and floating condition (e.g. decapods, echinoderms, several peracarid species), but a high diversity of organisms from all major phyla were observed on rafts. Throughout the PFR, the predominant rafting species belonged to the peracarids, molluscs and annelids, but the community composition differed between floating samples from the northern and southern zones of the PFR. Relative abundances of peracarids were higher in northern zones, whereas molluscs and annelids dominated in the southern areas. Species of the peracarid genera Peramphithoe, Gondogeneia, Bircenna and Limnoria were shared between all areas. The results suggest that kelp rafts not only contribute to local population connectivity in the PFR, but could also be an important dispersal vehicle for rafting species along the PFR in north–south direction, crossing the biogeographic boundary around Taitao Peninsula. Furthermore, the MR appears to be an important stepping stone for species dispersal via kelp rafting in the subantarctic region.
Año: 2012
Palabras claves:
Referencia APA: Wichmann, C., Hinojosa, I., & Thiel, M. (2012). Floating kelps in Patagonian Fjords: an important vehicle for rafting invertebrates and its relevance for biogeography. Marine Biology, 159(9), 2035-2049.
Reproductive biology of two species of squat lobsters – female receptivity and interbrood intervals.
Espinoza-Fuenzalida, N., Acuña, E., Hinojosa, I., & Thiel, M.
The reproductive biology of many species of anomuran crabs is only poorly known. Herein we studied the reproductive biology of two species of squat lobsters, Cervimunida johni Porter, 1903 and Pleuroncodes monodon (H. Milne Edwards, 1837), which are target of a trawl fishery operating on the continental margin along the Chilean coast. During the reproductive period (May-November) we maintained squat lobsters in the laboratory to examine whether mating is related to the reproductive molt of the female and to determine the interbrood interval between successive broods. In both species females mated during the intermolt period. Females became receptive shortly after having released larvae from a previous brood, when they formed pairs with males. The interbrood interval (from larval release until having a subsequent brood) lasted <72<72 hour in the majority of female C. johni, but was longer in P. monodon, where most females took 72-144 hours before producing a new brood. Despite longer interbrood intervals, copulatory mate-guarding was substantially shorter in P. monodon than in C. johni. These differences in reproductive behavior might be due to differences in the general biology of the two species, including mobility and intraspecific aggression. Mating during the intermolt period may have several advantages, namely reducing the risk of cannibalism and energy costs of molting during the reproductive season.
Año: 2012
Palabras claves: female receptivity, mating, reproduction, squat lobsters, trawl fishery.
Referencia APA: Espinoza-Fuenzalida, N., Acuña, E., Hinojosa, I., & Thiel, M. (2012). Reproductive biology of two species of squat lobsters – female receptivity and interbrood intervals. Journal Of Crustacean Biology, 32(4), 565-574
Microplastics in the Marine Environment: A Review of the Methods Used for Identification and Quantification.
Hidalgo-Ruz, V., Gutow, L., Thompson, R., & Thiel, M.
This review of 68 studies compares the methodologies used for the identification and quantification of microplastics from the marine environment. Three main sampling strategies were identified: selective, volume-reduced, and bulk sampling. Most sediment samples came from sandy beaches at the high tide line, and most seawater samples were taken at the sea surface using neuston nets. Four steps were distinguished during sample processing: density separation, filtration, sieving, and visual sorting of microplastics. Visual sorting was one of the most commonly used methods for the identification of microplastics (using type, shape, degradation stage, and color as criteria). Chemical and physical characteristics (e.g., specific density) were also used. The most reliable method to identify the chemical composition of microplastics is by infrared spectroscopy. Most studies reported that plastic fragments were polyethylene and polypropylene polymers. Units commonly used for abundance estimates are “items per m2” for sediment and sea surface studies and “items per m3” for water column studies. Mesh size of sieves and filters used during sampling or sample processing influence abundance estimates. Most studies reported two main size ranges of microplastics: (i) 500 μm–5 mm, which are retained by a 500 μm sieve/net, and (ii) 1–500 μm, or fractions thereof that are retained on filters. We recommend that future programs of monitoring continue to distinguish these size fractions, but we suggest standardized sampling procedures which allow the spatiotemporal comparison of microplastic abundance across marine environments.
Año: 2012
Palabras claves:
Referencia APA: Hidalgo-Ruz, V., Gutow, L., Thompson, R., & Thiel, M. (2012). Microplastics in the Marine Environment: A Review of the Methods Used for Identification and Quantification. Environmental Science & Technology, 46(6), 3060-3075.
Mining of EST-SSR from 454 pyrosequencing in the surf clam Mesodesma donacium (Lamark, 1818).
Aguilar-Espinoza, A., Guzmán-Riffo, B., Haye, P., & Gallardo-Escárate, C.
Novel simple sequence repeats (SSR) were identified from 454 transcriptome pyrosequencing ESTs in the surf clam Mesodesma donacium. From 7,734 ESTs annotated with SSR motives, 75 putative EST-SSRs were selected according their repetitive DNA sequence and functional annotation (Gene ontology), of these, 15 were characterized on 45 individuals of two wild populations located in two different biogeographic transition zones of the coast of Chile (30 and 42°S). Most loci were in Hardy–Weinberg equilibrium, and the polymorphic information content (PIC) ranged from 0.243 to 0.634. Pairwise Fst between sampled populations was estimated in 0.478. These EST-SSR markers promise to be useful for future management strategies of this overexploited species.
Año: 2012
Palabras claves: Pyrosequencing 454, Expressed sequence tag (EST), Microsatellite, Mesodesma donacium
Referencia APA: Aguilar-Espinoza, A., Guzmán-Riffo, B., Haye, P., & Gallardo-Escárate, C. (2012). Mining of EST-SSR from 454 pyrosequencing in the surf clam Mesodesma donacium (Lamark, 1818). Conservation Genet Resour, 4(4), 829-832.
The marine brooder Excirolana braziliensis (Crustacea: Isopoda) is also a complex of cryptic species on the coast of Chile.
Varela, A. & Haye, P.
Speciation is a direct consequence of isolated populations in taxa with low dispersal potential. The brooding crustacean Excirolana braziliensis, with a presumably wide geographic range of distribution (~16° N-41° S in the Pacific and ~19° N-35° S in the Atlantic), has been detected to correspond to cryptic species on the coast of Panama. Latitudinal variations in reproductive features in E. braziliensis have been attributed to phenotypic plasticity, however, the differences may be the result of divergent populations. Considering that the taxon has been reported to be a complex of cryptic species in other geographic areas and given the phenotypic differences detected along its distribution range, we hypothesized that E. braziliensis is a complex of species in the coast of Chile. We used partial cytochrome c oxidase subunit I (COI) sequences from 132 individuals with the diagnostic morphology of E. braziliensis collected along ~2200 km of coast to determine the genetic structure of E. braziliensis. Phylogenetic and phylogeographic analyses showed three distinct clades with 14 to 19 % of genetic divergence and high values of genetic differentiation. Intra and inter-clade divergence revealed the existence of a species complex of E. braziliensis on the coast of Chile, supporting growing evidence of the high abundance of cryptic species in marine invertebrate taxa.
Año: 2012
Palabras claves: cryptic species, genetic differentiation, genetic distance, marine peracarids, phylogenetics.
Referencia APA: Varela, A. & Haye, P. (2012). The marine brooder Excirolana braziliensis (Crustacea: Isopoda) is also a complex of cryptic species on the coast of Chile. Rev. Chil. Hist. Nat., 85(4), 495-502.
Effect of two temperatures on ammonia excretion rates of Seriolella violacea (Palm fish) juveniles under rearing conditions.
Nerici, C., Silva, A., & Merino, G.
Nitrogenous compounds can be toxic to aquatic animals, especially when they are reared for production purposes at high stocking densities. Seriolella violacea is a pelagic fish, native from the easterly South Pacific Ocean. This species has shown desirable behavioral and metabolic characteristics under captivity conditions, which leaded the Marine Fish Laboratory from the UCN to increase its efforts on the research and development to validate S. violacea as a new aquaculture option. Therefore, the objective of this study is to determine the excretion rates of palm fish juveniles weighing 300–500 g at two different temperatures: 14 °C and 18 °C. Total ammonia as nitrogen (TAN) excreted was 4.4 ± 0.9 and 7.1 ± 1.9 mg TAN/kg fish/h for 14 °C and 18 °C respectively. The experiments were carried out in a recirculating system operating as a farm-like situation. Tests were performed in 1000 L rearing tanks operating as open respirometers. The results of the present study indicate that TAN excretion rates on S. violacea juveniles, is temperature dependent. Data obtained in these experiments are valuable information for the engineering design of land based aquaculture systems for palm fish.
Año: 2012
Palabras claves: Seriolella violacea; Excretion rates; Ammonia; Recirculating aquaculture system; Water quality
Referencia APA: Nerici, C., Silva, A., & Merino, G. (2012). Effect of two temperatures on ammonia excretion rates of Seriolella violacea (Palm fish) juveniles under rearing conditions. Aquacultural Engineering, 46, 47-52.
Floating Seaweeds and Their Communities.
Rothäusler, E., Gutow, L., & Thiel, M.
A wide diversity of floating seaweeds is found in temperate and subpolar regions of the world’s oceans where sea surface currents and winds determine their traveling velocities and directions. The importance of floating seaweeds as dispersal agents for associated organisms and for the algae themselves varies depending on the supply from benthic source populations and on their persistence at the sea surface. Persistence of floating algae depends on water temperature, grazing activity, epifaunal load, and, to a lesser extent, on prevailing irradiance conditions. In temperate regions, persistence of floating algae is primarily limited by warm sea surface temperatures and high densities of motile and sessile epifauna whereas at higher latitudes algae can successfully compensate grazer-induced tissue loss by continuous growth at the prevailing low water temperatures. Accordingly, floating seaweeds can bridge large oceanic distances especially at high latitudes allowing for connectivity among distant benthic populations of algae and associated rafters.
Año: 2012
Palabras claves:
Referencia APA: Rothäusler, E., Gutow, L., & Thiel, M. (2012). Floating Seaweeds and Their Communities. Ecological Studies, 359-380.