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Zoologia (Curitiba)

Print version ISSN 1984-4670

Zoologia (Curitiba, Impr.) vol.27 no.3 Curitiba June 2010

https://doi.org/10.1590/S1984-46702010000300024 

SHORT COMMUNICATION

 

Morphometric study of a Brazilian strain of Carchesium polypinum (Ciliophora: Peritrichia) attached to Pomacea figulina (Mollusca: Gastropoda), with notes on a high infestation

 

 

Roberto Júnio P. DiasI, 1; Adalgisa F. CabralI; Isabel C. V. Siqueira-CastroII; Inácio D. da Silva-NetoII & Marta D'AgostoI

ILaboratório de Protozoologia, Programa de Pós-graduação em Ciências Biológicas, Comportamento e Biologia Animal, Universidade Federal de Juiz de Fora. 36036-900 Juiz de Fora, Minas Gerais, Brazil
IILaboratório de Protistologia, Departamento de Zoologia, Universidade Federal do Rio de Janeiro. 21941-590 Rio de Janeiro, Rio de Janeiro, Brazil

 

 


ABSTRACT

During an ecological study of the epibiotic relationship between ciliate protists and Pomacea figulina (Spix, 1827) (Gastropoda, Ampullariidae), originating from an urban stream in southeast Brazil, a high infestation by the peritrich ciliate Carchesium polypinum (Linnaeus, 1758) Ehrenberg, 1830 (Ciliophora, Peritrichia) associated to the shell of one mollusc among 23 was observed. We provided a morphological and morphometric study of C. polypinum using observations of specimens in vivo, after protargol staining, and examined using scanning electron microscopy. The Brazilian-population of C. polypinum is characterized by: size of zooid in vivo 89 µm x 57 µm on average; colony regularly dichotomously branched with usually up to 40 zooids; macronucleus usually J-shaped; single contractile vacuole located in the upper third of body; myoneme not continuous throughout the colony; stalks contract despite the discontinuity of their individual myonemes; polykinety comprises three peniculi, each consisting of three kineties. The high infestation showed here could be related to the preference for eutrophic environments showed by C. polypinum and suggested that ciliate epibionts may be ecologically important in aquatic habitats.

Key words: Ampullariidae; epibiosis; gastropod; morphology; peritrichs.


 

 

The peritrich ciliate Carchesium polypinum (Linnaeus, 1758) Ehrenberg, 1830 is commonly found in freshwater ecosystems and is a good indicator of poor water quality (WEI et al. 2004). Ciliates of the genus Carchesium live in colonies containing zooids, contractile stalks and free-swimming telotrochs (ZAGON 1971) and have high colonization rates in eutrophic ecosystems (KUSUOKA & WATANABE 1989). They generally do not display host specificity and could be found on seaweeds, emerged and submersed macrophytes, and attached to different groups of aquatic invertebrates (FOISSNER et al 1992, COOK et al. 1998, MAYÉN-ESTRADA & ALADRO-LUBEL 2002), including the gastropod Pomacea figulina (Spix, 1827) (DIAS et al. 2008). In addition to colonize living hosts, they also attach to inert substrates and have been recorded in diverse lotic systems associated to sediment (KUSUOKA & WATANABE 1989, SOLA et al. 1996, MADONI & BASSANINI 1999, MADONI 2005, MADONI & BRAGHIROLI 2007).

Prosobranch molluscs in the Ampullariidae family are widely distributed in subtropical and tropical regions, freshwater ecosystems, preferentially inhabiting still waters in lotic systems. Molluscs in the genus Pomacea also tolerate organic pollution (THIENGO 1995), and are promising indicators of water quality (COLER et al. 2005). This condition increases the ecological opportunity for colonization by peritrich ciliates which present a high preference for eutrophic environments.

During an ecological study on the epibiont ciliate community and prosobranch molluscs Pomacea figulina (Gastropoda: Ampullariidae) (DIAS et al. 2008), collected in an urban stream, a high infestation of the peritrich ciliate Carchesium polypinum (Ciliophora, Peritirchia) associated to the shell of one mollusc, out of 23, was analyzed. The gastropod (5.0 x 4.6 cm) was collected from a sampling station (21°46'38.1"S, 43°24'0.4"W) in São Pedro stream, at an urban area of Juiz de Fora, Minas Gerais, southeast of Brazil. Water samples were collected and fixed with 10% formaldehyde (5 ml) to quantify the bacterial density (HOBBIE et al. 1977), and to assess chlorophyll concentration (5 ml) (APHA 1992). Water temperature, conductivity, pH and dissolved oxygen data were measured with portable equipment. In the laboratory, the mollusc was scrubbed with a blader on Petri dishes containing previously filtered water collected from the same place. The ciliates were observed in vivo through bright field and differential interference contrast microscopy, stained using the protargol technique (DIECKMANN 1995), and prepared for scanning electron microscopy (SILVA-NETO 1994). Examinations of in vivo and prepared slides were made with an Olympus BX51 bright field microscopy while the biometric analyses were performed using Image Pro-Plus 5.0 software. The ciliates were then identified according to ZAGON & SMALL (1970), ESTEBAN & FERNÁNDEZ-GALIANO (1989), and FOISSNER et al. (1992). The mollusc was sent to the Malacology Sector, Instituto Oswaldo Cruz, and identified by Dr Silvana Thiengo.

Morphological analyses revealed that a single species of a colonial peritrich Carchesium polypinum colonized P. figulina collected in São Pedro stream (Figs 1-3). The overall morphology of the Brazilian strain of C. polypinum described in the present study is very similar to the species studied by ZAGON (1970, 1971), ZAGON & SMALL (1970), CURDS et al. (1983), ESTEBAN & FERNÁNDEZ-GALIANO (1989), FOISSNER et al. (1992), so we considered both conspecific. We provided a morphometric characterization of the species based on 10 characters measured from living individuals and nine characters measured from protargol-stained specimens (Tab. I).

The colonies of C. polypinum are branched with inverted bell-shaped zooids arranged on the branches. The colonial assemblage has a main stalk that is joined to the substratum by a fixing disc. The colonies had usually up to 40 zooids. The zooids are found in symmetrical dichotomous colonies. Colonies range in length from 700 µm to 2 mm. Zooids in vivo from 76.9 to 110.6 µm in length, and between 35.6 and 83.6 µm in width. The size of impregnated zooids varied between 45.0-57.1 µm in length and 36.4-55.9 µm in width. The length of the zooid decreased by 42% when stained. Cytoplasm slightly greyish, usually containing several large bronwish food vacuoles (7-20 µm in diameter). A single contractile vacuole located in the upper third of body. Macronucleus J-shaped that usually descended to a region just aboral to the telotroch band. The macronucleus is large and occupies a significant proportion of the body volume. The micronucleus was located close to the J-shaped macronucleus. The peristomial disc in vivo is 50.1-107.8 µm wide and 5.0-20.8 µm thick. Located on the side opposite to the peristome is the lateral stalk, which in non-contracted specimens measured 10.8-17.4 µm in width. The lateral stalk surface had irregular folds as showed by scanning electron microscopy. The myoneme is not continuous throughout the colony. The stalks contract despite the discontinuity of their individual myonemes. Myoneme ranges from 1.2-4.9 µm in width, presenting fibers that extended anteriorly within the zooid, from the scopula to central part of the cell body. The myoneme stains heavily with silver, but the remainder of the stalk is transparent. As observed in other peritrichs, the infraciliature of the zooid of C. polypinum is formed by the oral infraciliature and the aboral ciliary wreath. The aboral ciliary wreath (trochal band) is constituted by a ridge of kinetosomes placed in two staggered rows surrounding the posterior end of the organism. The distance between the trochal band and the scopula is 9.2-17.6 µm. However, these numbers probably are smaller than the actual values because contraction is initiated by silver-impregnation. The oral infraciliature is well developed in this species. The oral apparatus is usual for peritrichs. The haplokinety and polykinety circle about one turn around the peristomial disc and make a further turn after plunging into the infundibulum. The polykinety comprises three peniculi (oral polykinetids) in the lower half of infundibulum, each consisting of three kineties. The oral polykinety 1 (P1) is paralleled at its point of separation by a second triple row of kinetossomes. The posterior ends of the three kineties of P1 terminate at slightly different levels. The oral polykinetid 2 (P2) appears to begin at a slight angle and from a single point presents a short distance from P1, turns slightly, and can then be clearly seen as three distinct ciliated rows of kinetossomes. P2 is interposed between oral polykinetids 1 and 3. The oral polykinetids 3 (P3), presents three short rows of kinetosomes, and appears approximately in the aboral one-third of the infundibulum (Figs 4-17, Tab. I).

The Brazilian strain of C. polypinum is similar to the population described by FOISSNER et al. (1992) in terms of body length (77-110 µm vs. 80-140 µm), number and position of contractile vacuoles, shape of macronucleus, number of zooids, and the oral infraciliature. As demonstrated by recent papers, the infraciliature revealed with silver impregnation is highly species-specific, especially the structure of infundibular polykineties in the oral apparatus, playing an essential role in the determination of species (CLAMP 1990, JI & SONG 2004, JI et al. 2005). Several published reports describe the morphology of the colony and zooids of C. polypinum (KAHL 1935, LOM 1964, CURDS 1969, ZAGON 1970, 1971, ZAGON & SMALL 1970, CURDS et al. 1983, ESTEBAN & FERNÁNDEZ-GALIANO 1989, FOISSNER et al. 1992), however, few morphometric characters were included in these studies. In the present study, we provide a characterization of the species based on new morphometric characters as used by UTZ (2007).

Studies emphasizing genetic variation within-species are needed to determine whether C. polypinum collected from different sites around the world could be considered a single genetic unit. For example, GENTEKAKI & LYNN (2009) concluded that colonies of C. polypinum isolated from different locations in the Grand River basin in Southwestern Ontario, Canada, probably are not a single morphospecies as previously thought.

The only snail infested by the peritrich ciliate Carchesium polypinum (Linnaeus, 1758) Ehrenberg, 1830 (Ciliophora, Peritrichia) observed in this study was collected near to the entrance of domestic sewage in the stream suggesting that the organic pollution level could be the cause of this high infestation. Direct discharge of domestic sewage into the water causes an elevation in the concentration of phosphates and other nutrients, increasing the density of bacteria, the main food for peritrich ciliates (PRIMC 1988). The high infestation showed here could be related to the preference for eutrophic environments showed by C. polypinum. The autecological data recorded for C. polypinum in the present study and in previous studies as revised by FOISSNER et al. (1992) are presented in table II. This observed infestation demonstrates that ciliate epibionts may be ecologically important in aquatic habitats and their relative biomass should be taken into consideration when benthic ciliates, in a given habitat, are assessed.

 

ACKNOWLEDGEMENTS

We would like to thank Silvana Thiengo (FIOCRUZ) for the identification of the snail, Sthefane D'ávila (UFJF) for making the schematic ink drawings, and Laura Utz for English revision. We also acknowledge the suggestions made by the editor. This study was financially supported by FAPEMIG and PROPESQ/UFJF.

 

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Submitted: 26.II.2009; Accepted: 23.II.2010.

 

 

Editorial responsibility: Marcus V. Domingues
1 Corresponding author. E-mail: rjuniodias@hotmail.com

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