versión On-line ISSN 0718-1957
Rev. biol. mar. oceanogr. v.41 n.2 Valparaíso dic. 2006
Revista de Biología Marina y Oceanografía 41(2): 245-248, diciembre de 2006
First record of Phyllochaetopterus socialis Claparède, 1870 (Annelida: Polychaeta) in Mar del Plata Harbor, Buenos Aires, Argentina
Primer registro de Phyllochaetopterus socialis Claparède, 1870 (Annelida: Polychaeta) en el puerto de Mar del Plata, Buenos Aires, Argentina
Mariano Albano1, Juan Pablo Seco Pon1, Sandra Obenat1 and Gabriel Genzano2,3
1 Departamento de Biología, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Casilla de correo 1216, 7600 Mar del Plata, Argentina
Agregados del poliqueto tubícola Phyllochaetopterus socialis Claparède, 1870 fueron registrados por primera vez en el Puerto de Mar del Plata (38°02’S; 57°31’30”W), Buenos Aires, Argentina, en diciembre de 2003 mediante buceo autónomo a 6 m de profundidad. Los agregados fueron observados sobre sustrato duro, en el límite inferior del submareal. El presente trabajo amplia el rango de distribución de dicha especie para Sudamérica, de la cual se tienen registros confirmados únicamente para el sur de Brasil y el Río de la Plata (Argentina).
Palabras clave: Macrobentos, fauna asociada, Chaetopteridae, gusanos tubícolas, buceo autónomo
Chaetopteridae is a taxon found worldwide from intertidal sediments down to abyssal regions, comprising about 65 species of tubiculous worms placed in four genera: Chaetopterus, Mesochaetopterus, Spiochaetopterus and Phyllochaetopterus. This group posed species that bury their tubes, generally in sands or muds while others attach their tubes to hard substrates (Rouse & Pleijel 2001).
Depending on the species, body can be divided in two or three conspicuous regions, a peristomium that may have one or two pairs of tentacular cirri and palps of variable length. The anterior region holds unirramous parapodia while median and posterior regions present birramous parapodia; setaea include capillary, limbae setae and modified spines in setiger 4 with uncini pectiniform in posterior setigers (Fauchald 1977).
Phyllochaetopterus is a genus comprised of 17 species (Fauchald 1977), which P. socialis Claparède, 1870 was found in New Zealand, South Africa, India (including Pakistan, Ceylon, Burma and Malaya), Mediterranean Sea, Mexico and Costa Rica (Rioja 1941, Fauvel 1953, Day 1967, Probert & Wilson 1984, Ariño 1987, Abbiati et al. 1994, Dean 1996), but its assumed cosmopolitan distribution is under discussion (Bhaud pers. comm.)
Recently, it has been described for South America along the southern rocky shore of Brazil (Nalesso et al. 1995) and into estuarine areas of Río de La Plata (Obenat et al. 2001). This last study constitutes the first record for Argentinean continental shelf waters. Both studies agree that this species, among others marine benthic invertebrates, is associated with hard substrata such as rocks, empty mollusk shells and handmade hard objects.
An ecosystemic engineer status has been suggested for this tubiculous worm due to the intricate architecture of its tubes (aggregates, mats), which provide refuge and food supply for numerous marine species (Gettleson et al. 1985, Nalesso et al. 1995, Obenat et al. 2001).
Whilst a collecting trip to the Mar del Plata Harbor (38º02’S, 57º31’30”W), Buenos Aires, Argentina, during December 2003, aggregates of Phyllochaetopterus socialis were first registered during SCUBA dives performed at the north breakwater of this locality; this record extends the geographical distribution of this species in the south western Atlantic Ocean.
MATERIAL AND METHODSStudy area
The Mar del Plata Harbor is limited by two artificial breakwaters chiefly composed of ortoquartzitic blocks (Fig. 1). Mean water depth is about 5 m, ranging between 3 and 10 m. Water of low turbidity along with low salinity, dissolved oxygen and pH characterize the area (Rivero et al. 2005). This harbor has an appreciable pollution due to naval traffic, industrial discharged sewage and others contributions of surroundings waters (Bastida 1971).
Aggregates (mats) of Phyllochaetopterus socialis were first registered during SCUBA dives performed at 6 m at the north breakwater of Mar del Plata’s Harbor (Fig. 1), on December 2003. Three dives were conducted on February 2004 when aggregates of P. socialis were randomly selected and sampled; whole mats were collected by hand, rubbed into plastic bags under water and then fixed with a formaldehyde solution (4%) on land. Water column displacement was performed in the laboratory in order to calculate the volume of the mats. Each sample was sieved and the macrozoobenthic organisms retained (> 0.5 mm) were preserved in 4%-formaldehyde solution.RESULTS
Mats of P. socialis (Fig. 2) were observed arising from hard substrate between the lower limits of the subtidal floor belonging to the north breakwater of the Mar del Plata’s Harbor. Aggregates were sticked to different sides of the blocks, equally hanging or arising from them. Accumulation of organic material was observed at the basal structure of P. socialis mats. Mean volume of the mats was 291.6 cm3 (SD=190.4, n=3). An overall of 917 marine invertebrate organisms belonging to six taxa were counted associated to P. socialis mats, constituting a specific richness of 25 species. Most abundant taxa (expressed as a percentage of number of organisms/250 cm3) corresponded to Crustacea (90.5%), meanwhile Mollusca (7.83%) and Polychaeta (1.65%) were less representated. In addition, the colonial bryozoan Bugula stolonifera, the red alga Pterosiphonia sp. and the green alga Bryopsis sp. were also found attached to the tubes of this polychaete, remarking the importance of the mats as substrata and refuge for many associated organisms.
The present study extends the geographical distribution of Phyllochaetopterus socialis for South America and constitutes the first record for Mar del Plata’s Harbor.
Although Phyllochaetopterus socialis was not included in a regional scope of exotic marine species in the southwestern Atlantic Ocean (Orensanz et al. 2002), several specialists are discussing on its invasive exotic status.
Unfortunately, in the southwestern Atlantic Ocean baselines information from long - term monitoring are rare, turning very difficult to establish the starting point of a successful introduction. In the case of P. socialis, the first observations of this species into Mar del Plata harbor were during 1994 (Genzano pers. comm.), but just confirmed in this study.
It is remarkable that small tubes of P. socialis were occasionally observed in a quartzitic rocky outcrops front of Mar del Plata city (38°10’S, 57°26’W, 20 m depth) during December 2002. These scarce tubes attached directly on the rocks and never conformed mats. Further monitoring will be necessary in order to analyze if this species establishes successfully in this area, such as occurred in Mar del Plata harbor.
Observations conducted during this survey agree with Nalesso et al. (1995) and Obenat et al. (2001) results over hard substrata species association. The intricate structure of P. socialis tubes causes the accumulation of organic material, favoring the establishment of several detritivores species. These living shelters could have a special importance to juvenile’s forms of many marine organisms (Spivak pers. comm.).
Due to the ecosystemic engineer status suggested by several authors (Gettleson et al. 1985, Nalesso et al. 1995, Obenat et al. 2001), further monitories of P. socialis aggregates in Mar del Plata Harbor are needed to characterize the macrozoobenthic fauna associated and conduct further comparisons with Nalesso et al. (1995) and Obenat et al. (2001) results.ACKNOWLEDGMENTS
To Dr. Rodolfo Elías for the Mar del Plata Harbor map. To Lic. Laura Mauco for helping and criticizing the present study. We would also like to thank to the anonymous referees for many helpful comments and suggestions to improve the manuscript.
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