First record in the Tropical Eastern Pacific of the exotic species Ficopomatus uschakovi (Polychaeta, Serpulidae)

Abstract The exotic Indo-West-Pacific species, Ficopomatus uschakovi (Polychaeta, Serpulidae) is recorded for the first time in the Tropical Eastern Pacific from two sites in La Encrucijada Biosphere Reserve, Chiapas, a coastal lagoon in the Pacific south of Mexico. The means of dispersal of this serpulid species still remains unclear, as the nearest port (Puerto Chiapas) is 70 km to the south, and there are no port installations or shrimp cultures in the lagoon. The record of this serpulid species, apparently widely distributed in this coastal lagoon, has implications regarding possible effects on the brackish-water ecosystem, since the invasion event very well may have occurred several years ago. It is recommended that an exhaustive study be carried out in the coastal lagoons of Chiapas to evaluate the real distribution and the effects of this invasive species on the ecosystem. A complete description, including photographs and drawings, is provided.

On the Pacific Coast of America, no indigenous species of Ficopomatus has been described (Bastida-Zavala 2008). However, F. enigmaticus, was recorded as an exotic species from San Francisco Bay, California (ten Weerdenburg 1978, Bastida-Zavala 2008), and, recently, F. miamiensis was recorded from Urías lagoon, near Mazatlán, southeast of the Gulf of California, as an exotic species related to shrimp-ponds; however, the introduction could have taken place 20 years ago, when shrimp larvae were imported from Florida (Salgado- Barragán et al. 2004, Tovar-Hernández et al. 2009).
The case of F. enigmaticus, a serpulid widely dispersed around the world and with a long historical record of invasions, is a well-known example, because it can have dramatic impacts in invaded habitats building large, reef-like colonies in some coastal lagoons that cause major changes in benthic communities, especially in the Lake of Tunis (ten Hove and van den Hurk 1993) and the Mar Chiquita Lagoon, Argentina (Schwindt et al. 2001, Luppi and Bas 2002, Bazterrica et al. 2012. Rioja (1943) recorded, for the first time, F. enigmaticus from Puerto Quequén, south of Mar del Plata, and now the species is widely distributed in the Mar Chiquita Lagoon, forming annular reefs and having several effects on the ecosystem and navigation of fishing boats in this lagoon-system (Schwindt et al. 2001, Luppi and Bas 2002, Schwindt et al. 2004a. Borthagaray et al. (2006) analysed the potential impacts of this invasive species in other lagoons of La Plata River, especially of the Uruguay coast.
The effects of F. miamiensis in Urías lagoon were considered to be positive in the shrimp-ponds because the population of these serpulids (densities higher than 230,000 ind/m 2 ) helps to clean the water and control the suspended particulates. However, the impact of the colonies attached to the mangrove roots is negative, because the serpulid competes with other fouling and filter-feeding invertebrates such as native barnacles, mussels and oysters (Tovar-Hernández et al. 2009).

Materials and methods
From 19-24 September, 2011, we visited several sites to collect marine invertebrates in Chiapas, including Puerto Chiapas (or Puerto Madero, as its old name), La Encrucijada Biosphere Reserve, Chocohuital, Boca del Cielo Lagoon, Paredón (Mar Muerto Lagoon) and ending in Oaxaca, in San Dionisio del Mar (Superior Lagoon). Serpulid samples were taken from hard substrates such as rocks, mangrove roots and artificial structures (e.g. piers, submerged buildings, etc.). The preliminary examination of the specimens included only the samples from La Encrucijada Biosphere Reserve because Ficopomatus tubes were immediately identified in the field. In the other sites in Chiapas and Oaxaca the typical tubes of Ficopomatus were not found. Most specimen lots were deposited in the Colección de Invertebrados Marinos, Universidad del Mar, Puerto Ángel, Oaxaca (UMAR-Poly), other samples were deposited in the collections of El Colegio de la Frontera Sur, Chetumal, Quintana Roo (ECOSUR), and in the Universidad Autónoma de Nuevo León, Monterrey, México (UANL). Topotypical specimens examined came from the Los Angeles County Museum of Natural History, Allan Hancock Foundation, Los Angeles, California, USA (LACM-AHF).
The specimens were fixed with 10% formalin and preserved in 70% alcohol. The line drawings were made using camera lucida, the photographs were taken with a digital camera (Nikon Coolpix). Opercula were generally found to be covered in silt and algae, and were, therefore, cleaned with a fine brush.
Standard measurements and counts were total length, measured from the most distal part of the operculum to the pygidium; thoracic length, from the apron to the base of the collar; thoracic width, measured across the collar region; the number of thoracic chaetigers, the number of radioles in each lobe of the branchial crown; opercular length, from the base of peduncle to the end plate; and opercular diameter, measured across the dorso-ventral axis of the end plate.
The collar is entire, with well-developed lobes. The collar chaetae include coarsely serrated chaetae and hooded (capillary) chaetae. The thoracic membranes are fused dorsally, ventrally forming a small apron. The thorax has six chaetigers with hooded (limbate) chaetae, and saw-shaped uncini. A short achaetous region is present between the thorax and abdomen. Most of the abdominal segments possess geniculate chaetae and rasp-shaped uncini.   (Fig. 3B).
Apart from the spines of the operculum, the main character that separates Ficopomatus uschakovi from F. enigmaticus and F. miamiensis is the dorsally fused thoracic membranes. This autapomorphy of F. uschakovi is regarded to be of generic level by Pillai (2008), but is not followed by us.
In the local community the serpulid tubes on the mangroves are called 'broca' (more or less 'drill'), just like all other sessile invertebrates with calcareous covers, such as barnacles and oysters.

Discussion
The presence of a species, resembling F. uschakovi, from La Encrucijada Biosphere Reserve was initially brought to the attention of the authors two years ago (S.I. Salazar-Vallejo et al. pers. comm. 2009). Previously, no other record of the species existed throughout the Tropical Eastern Pacific. However, the observations in the field show that F. uschakovi is widely distributed in La Encrucijada, suggesting that the invasion event of this species may have occurred several years ago.
Although ballast water, sediment transport and fouling are the main means of dispersal of aquatic exotic species (Carlton and Geller 1993, Ruiz et al. 2000, Okolodkov et al. 2007, the means of dispersal of F. uschakovi in La Encrucijada Biosphere Reserve still remains unclear, as the nearest port (Puerto Chiapas) is 70 km to the south, and there are no port installations or any shrimp cultures in the lagoon. The local people mentioned that these serpulids had gone unnoticed until now and apparently negative effects to the ecosystem have not been detected, except the fouling of the fishing boats, which require frequent cleaning.
Mass occurrence of F. uschakovi was observed ( Fig. 2A), however, not to the extent of the reef-like structures, formed by F. enigmaticus in Argentina (Schwindt et al. 2004a, b) and by F. miamiensis in Mazatlán (Tovar-Hernández et al. 2009). However, similar impacts as caused by the latter species may be expected for F. uschakovi. Therefore, it is necessary to conduct detailed monitoring of F. uschakovi in the sites that have been invaded. It is also recommend that an exhaustive study in the coastal lagoons of Chiapas be conducted to evaluate the real distribution and the impact generated by F. uschakovi. ence of this species in La Encrucijada. We thank Edmundo Aguilar López, Teófilo González and Candelario Girón (CONANP, Chiapas), for their support during the visit to La Encrucijada Biosphere Reserve. The help in the field of Jani Jarquín-González (INECOL, Xalapa), Carmen Méndez (CICIMAR, La Paz) and Violeta Jiménez (UNSIJ, Ixtlán) was invaluable; Esmeralda Morales (UMAR, Puerto Angel), is thanked for the fast processing of the samples. The gastropod shell was identified by Norma Barrientos (UMAR). The specimens from Sri Lanka were examined in a visit to Los Angeles in 2004, hosted kindly by Leslie Harris (LACM-AHF). We appreciated the corrections and comments of Harry ten Hove (NCB Naturalis, Leiden), one anonymous referee and Chris Glasby (as editor) to the latest version. This work is part of the study of marine exotic species made by the Mexican network of exotic species (UMAR-UANL-UABC), supported by the project Programa de Mejoramiento del Profesorado 103-5/09/1353.