New records of brackish water Rotifera and Cladocera from Mexico

S. S. S. Sarma, S. Nandini¹, Pedro Ramírez García¹ y Juana E. Cortéz Muñoz²

Carrera de Biología, UNAM, campus Iztacala, Av. de los Barrios s/n, CP 54090. Tlalnepantla, Los Reyes Apdo. Postal 314, Edo de México. E-mail: sarma@servidor.unam.mx

¹ Proyecto CyMA, UNAM campus Iztacala, Av. de los Barrios s/n, CP 54090. Tlalnepantla, Los Reyes Apdo. Postal 314, Edo de México, México.

² IMTA, Instituto Mexicano de Tecnología del Agua. Paseo Cuauhnáhuac 8532, Jiutepec, Morelos 62550, México.

Resumen

Se colectaron mensualmente muestras de zooplancton en varios puntos de muestreo en la laguna salobre de Mecoacán (Tabasco), durante los años 1995-1997 las cuales revelaron la presencia de 37 especies de rotíferos y dos especies de cladóceros. En ese estudio, encontramos cinco nuevos registros de Rotífera y que son: Platyias ieloupi, Ploesoma hudsoni, Synchaeta bicornis, S. hyperborea y Trichocerca marina y un nuevo registro de Cladocera: Moina minuta. Asimismo se ilustran los nuevos registros y se presentan aspectos de su distribución.

Palabras clave: Registros nuevos, Rotíferos, Cladóceros, Tabasco, México.

Abstract

Zooplankton samples collected monthly from various parts of the brackishwater lagoon Mecoacan in State of Tabasco during the years 1995-1997 revelated the occurrence of 37 rotifer species and two cladoceran species of which five rotifers viz. Platyias leloupi, Ploesoma hudsoni, Synchaeta bicornis, S. hyperborea and Trichocerca marina and one cladoceran viz. Moina minuta are new to Mexican fauna. The recorded species are illustrated and aspects of their distribution are presented.

Key words: New records, Rotifer, Cladoceran, Tabasco, Mexico, Brackishwater

Introduction

In Mexico studies on zooplankton, particulary, Rotifera and Cladocera (Crustacea), in freshwater bodies have been well documented (Rico-Martínez and Silva-Briano, 1993); Sarma and Elías-Gutiérrez, 1997, 1999; Elías-Gutiérrez et al., 1998a). Some species of rotifers and cladocerans also occur in saline and marine environments (Wallace and Sneil, 1991; Dodson and Frey, 1991) and they received little attention.

The freshwater bodies in the central part of Mexico have been well explored rotifer and cladoceran taxa (see reviews of Sarna et al., 1998b for Cladocera). Similar information from other parts of Mexico, especially for rotifers is scarce (Örstan, 1995). For example no data on the rotifer taxa are available from the coastal states of Tabasco, Chiapas and Campeche (Elías-Gutiérrez et al., 1998a).

In this paper, we present the first study on the rotifers and cladocerans found in the brackishwater lagoon of Mecoacan in the State of Tabasco.

Materials and methods

The study site is a perennial brackishwater lagoon (Mecoacan) situated at 18°20' - 18°26' N and 93°01' - 93°15' W located in the State of Tabasco (Mexico). We collected zooplankton samples from the surface and at 1 and 2 m depths. For each sampling at least 100 l were filtered using 50 μm plankton mesh and were immediately preserved in 10% formalin. The samples were collected once a month over a 2-year period (1995-1997).

For the identification of Rotifera we followed mainly Koste (1978). However, we also consulted other literature as necessary (Koste and Shiel, 1987, 1989, 1990, 1991). Trophi preparation, when needed, was done using the dilute sodium hypochlorite solution. Cladocera were identified following Korovchinsky (1992) and Goulden (1968). All figures were drawn under a compound microscope using a calibrated camera lucida (Nikon Labophot Model 2).

Analysis of zooplankton samples from Mecoacan lagoon yielded 37 taxa of Rotifera and 2 species of Cladocera. Of these, 5 rotifer species and 1 cladoceran species are new records (marked with *) to the fauna of Mexico.

Rotifera:

Phylum: Rotifera

Order: Ploimida

Family: Epiphanidae

1. Epiphanes macrourus (Barrois & Daday, 1894)

Family: Brachionidae

2. Anuraeopsis fissa (Gosse, 1851)

]]> 3. Brachionus angularis (Gosse, 1851)

4. B. budapestinensis (Daday, 1885)

5. B. calyciflorus Pallas, 1766.

6. B. caudatus Barrois & Daday, 1894

7. B. falcatus Zacharias, 1898

8. B. havanensis Rousselet, 1911

9. B. plicatilis (O. F. Müller, 1786)

10. B. rotundiformis Tschugunoff, 1921

11. B. urceolaris (O. F. Müller, 1773)

12. Keratella americana Carlin, 1943

]]> 13. K. cochlearis (Gosse, 1851)

14. K. tropica (Apstein, 1907)

15. Platyias leloupi (Gillard, 1957)*

Family: Euchlanidae

16. Euchlanis dilatata Ehrenberg, 1832

Family: Lecanidae

17. Lecane bulla (Gosse, 1851)

18. L. curvicornis (Murray, 1913)

19. L. grandis (Murray, 1913)

20. L. stenroosi (Meissner, 1908)

]]> Family: Notommatidae

21. Eosphora najas Ehrenberg, 1830

Family: Trichocercidae

22. Trichocerca dixonnuttali Jennings, 1903

23. T. elongata (Gosse, 1886)

24. T. marina (Daday, 1890)*

25. T. ruttneri (Donner, 1953)

26. T. similis (Wierzejski, 1893)

27. T. stylata (Gosse, 1851)

Family: Gastropodidae

]]> 28. Ascomorpha saltans Bartsch, 1870

Family: Synchaetidae

29. Ploesoma hudsoni (Imhof, 1891)*

30. Synchaeta bicornis Smith, 1904*

31. S. hyperborea Smirnov, 1932*

32. S. pectinata Ehrenberg, 1832

33. S. stylata Wierzejski, 1893

Family: Asplanchnidae

34. Asplanchna brighwelli (Gosse, 1850)

35. A. sieboldi (Leydig, 1854)

]]> Order: Gnesiotrocha

Family: Filiniidae

36. Filinia longiseta (Ehrenberg, 1834)

Bdelloidea

37. Philodina sp.

The diversity of rotifers in the Mecoacan lagoon can be considered as high since rotifers predominantly occur in freshwater environments (Green, 1993, 1995). The salinity values in the present study varied between 5-35‰ through-out the study. Majority of the rotifer species encountered in this study are mostly tropical (Koste, 1978) and it is not surprising that we encountered them in Mecoacan lagoon where the mean observed water temperature was around 25°C. The euryhaline Brachionus plicatilis (Fig. 1) and B. rotundiformis (Fig. 2) were the most common species in our study. We discuss here the new records of zooplankton from the point of view of zoogeography.

T. marina (Fig. 4). Strong loricate species with prominent anterior spines. Characterized as stenohaline species. Commonly encountered in the plankton of coastal waters. Recorded from East and northern European seas, Caspian sea and Black sea (Koste, 1978).

Ploesoma hudsoni (Fig. 5). Specimens were collected from the Mecoacan lagoon when the salinity was 15‰. Koste (1978) regards this species as common in plankton collections of warmwater lakes and brackish water environments.

Synchaeta bicornis (Fig. 6). Large non-loricate species, easily identified by the presence of two antero-lateral horn structures, more prominent under preserved condition. Planktonic species recorded from South Sea, Netherlands, and in the brackish waters of the United States of America (Koste, 1978).

S. hyperborea (Fig. 7): Co-existed with S. bicornis. Earlier recorded from planktonic collections of coastal water of France and North Sea (Koste, 1978).

Cladocera:

Phylum: Arthropida

Class: Branchiopda

Order: Ctenopoda

]]> Family: Sididae

1. Diaphanosoma brevireme Sars, 1901

Order: Anomopoda

Family: Moinidae

2. Moina minuta Hansen, 1899*

Since cladocerans are predominantly found in freshwater systems, not much attention is paid to the brackwish and marine water species (Dodson and Frey, 1991). This is also the case in Mexico. For example, Elías-Gutiérrez et al (1998b) have listed predominantly the freshwater Cladocera of Mexico.

Moina minuta (Figs. 8a-f): Species characterized by a small head (Fig. 8a); antennules provided with long sensory seta on the anterior margin (Fig. 8d); at the base of the antenna two long sensory setae present (Fig. 8c), one of them longer than the combined length of basipod and first segment of exopod. On the basipod, between exopod and endopod one seta present. The present specimens agree with the description of first thoracic leg (Fig. 8b) given in Goulden (1968) based in the samples collected from Guatemala. However, slight differences are noticeable in the number of teeth on the pecten of the postabdomen (Fig. 8e) (8 in the present case vs 11-14 in Goulden (1968)) and the ventral margin of the carapace (Fig. 8f). Type locality is in Brazil. It is regarded as limnoplanktonic prefering saline and/or oligohaline rivers. Recorded from lakes and rivers opening to the ocean from the east coast of Central and South America (Goulden, 1968).

The present study thus adds one genus (Ploesoma) to the rotifer fauna of Mexico. This is one of the few studies in Mexico attempting to investigate marine rotifers (Rico-Martínez and Silva-Briano, 1993) and cladocerans (Elías-Gutiérrez et al. 1998b) from the taxonomic point of view. This study thus suggest more extensive investigations are needed to understand the diversity of rotifers and clarocerans in Mexico not only from the freshwater habitats, but also from marine and brackishwater environments.

Acknowledgements

This study was conducted under a collaboration of Mexican Institute of Water Technology (IMTA) and National Autonomus University of Mexico (UNAM) - Campus Iztacala. The samples were collected by the staff of Microbiology Division (Water Quality) of the IMTA. SSSS and NS are thankful to the National System of Investigators for support (No. 18723 & 20520).

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