First record of Limnodrilus claparedeianus Ratzel, 1868 (Annelida: Oligochaeta: Tubificidae) in Anzali Wetland, Guilan province, Iran

[Short Communication]

First record of Limnodrilus claparedeianus Ratzel, 1868 (Annelida: Oligochaeta: Tubificidae) in Anzali Wetland, Guilan province, Iran

F. Nazarhaghighi¹, R. Mousavi Nadoushan², N. Shabanipour^*3, M. R. Fatemi¹, A. Mashinchian Moradi¹

1. Dept. of Marine Biology, Graduate School of Marine Science and Technology Islamic Azad University, Science and Research Branch, Tehran, Iran.

2. Faculty of Marine Science & Technology, Islamic Azad University, North branch, Tehran, Iran.

3. Faculty of science, University of Guilan, Rasht, Iran.

* Corresponding author’s E-mail: shabani@guilan.ac.ir

ABSTRACT

Oligochaeta worms are important organisms in aquatic ecosystem. Their omnipresence makes them as an indicator of environmental changes and health of aquatic ecosystem. The members of the family Tubificidae and in particular, genus Limnodrilus are considered as the most tolerant oligochaets to aquatic pollution. Therefore identification and biological characteristics of this taxon are of great help to evaluate the ecosystem of water bodies. Limnodrilus claparedeianus were collected from Anzali Wetland with a grab of 0.04 m² capacity at 13 stations from August 2012 through June 2013. Penis sheath was one of the main characteristics to identify them. Results showed their maximum and the minimum density in spring (601.27±  466.8346 Ind.m^-2) and in autumn (156.12 ±136.3Ind.m^-2) respectively which was significantly different (P<0.05). Comparative spatial distribution of L. claparedeianus among 13 stations revealed significant differences in the west stations (P<0.05). According to the results, correlation analysis did not exhibit any relation between abundance of L. claparedeianus and total organic matter, abundance of the species and percentage of silt in substrate sediment.

INTRODUCTION

Benthic macro-invertebrate communities in wetlands are important component of the aquatic environment which plays momentous roles in the energy pathway and nutrient cycling, assessment of the ecological entirety and bio-monitoring of aquatic habitats (Lae, 1994; Gordon, 2000; Acharyya & Mitsch, 2001; MRC, 2010). They also establish an important connection as food reservoir for fishes and other animals in aquatic food chain (Blay & Dongdem, 1996; Arslan et al., 2007). Among benthic communities, oligochaetes are common and abundant animal groups, which are strongly influenced by environmental conditions. Out of more than 5000 known species of class Oligochaeta, approximately 1100 species live in freshwater (Suriani et al., 2007). Environmental richness of oligochaete species is directly related to food availability and quality, substrate type, oxygen availability and biological interactions. Furthermore this group are not much motile and mostly are considered as indicators of specific trophic state of aquatic habitat (Behrend et al., 2012). Generally, oligochaetes have wide geographical distribution patterns and their population can sometimes reach quite large number. Many species prefer eutrophic water, living on muddy sediments with abundant detritus organic matter. Anzali Wetland is an internationally known inland water body in north of Iran and has gained more reputations as being connected to Caspian Sea. It hosts a wide variety of animal species and therefore possesses great ecological concern to remain under continuous monitoring. The present study introduces Limnodrilus claparedeianus and its distributional peculiarities as a monitoring index.

MATERIALS AND METHODS

Study area

Anzali Wetland (37◦28_ N, 49◦25_ W) represents an internationally important wildlife reservoir and sanctuary with an open surface area of 58 km² which is listed under Ramsar Convention (Pourang, et al. 2010) (Fig. 1). Urbanization and population growth, industrial and agricultural activities, and also tourism are major sources of pollutants discharged into the Wetland directly or via rivers indirectly.

 The southern part of the wetland is mainly under rice cultivation and patches of woodland, while the northern part is bordered by sand dunes, grassland and scrubby vegetation (Ayati, 2003).

Sampling and sample preparation

The specimens of Limnodrilus claparedeianus were collected seasonally from 13 stations in Anzali Wetland from August 2012 through June 2013 (Fig. 1 and Table. 1). The oligochaetes were collected with grab (0.04 m²) accompanied with bryophytes and other submerged plants and also from bottom surface layer.

The sediments were passed through a 500 μm mesh size sieves on spot and sieved particles were preserved in 10% formalin. In the laboratory, samples were then isolated and transferred to 70% ethanol.

Worm specimens were dipped in Amman’s lactophenol for transparency, mounted on microscope slides covered by a cover slip and left for several hours before examination.

All measurements and photographs for preserved specimens were taken and analyzed by TSVIEW 5 mega pixel camera and software (version 6.2.4.5).

Identifications followed detailed description made by Kathman and Brinkhurst (1998) and Douglas (2001).

Certain collected specimens during this study are now deposited in Dr. Tarmo Timm’s fresh water annelid collections, Centre for Limnology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences under code number S-4333.

Total organic matter of sediment and the granulometric analysis followed the procedures described by Moghaddasi et al. (2009).

Fig. 1. Study area and sampling sites.

Table 1.  Coordination of sampling sites.

DATA ANALYSIS

Data analysis was done by SPSS version 18. Data normality was assessed using the Kolmogorov-Smirnov test.

For normally distributed data, One-Way ANOVA was performed. Otherwise, the Mann-Whitney U test and Kruskal -Wallis test was applied. For entry data to computer and calculation of mean, standard error, charting and other operations, Excel 2007 was used.

RESULTS

Morphological descriptions

Live specimens were red in color but formaldehyde preserved ones turned into milky cream. Worm body was 7 to 35 mm in length and 3 to 4 mm in diameter. The cylindrical body showed bilateral symmetry and at least 40 to more than 100 segments were

counted. Eye spots were absent. Caudal region was undifferentiated with conical prostomium (Fig. 2a, b). Dorsal and ventral chaetae commenced from second body segment, regularly and alternatively at upper and lower regions of body (Fig. 2d). All chaetae were bifid and similar, upper tooth longer than lower tooth or slightly equal and hair were absent in dorsal bundle (Fig. 2c). Anterior segments were comprised of 6-8 chaetae per dorsal bundle and 2 chaetae per ventral bundle. Clitellum was seen in segments X to XII. Like other oligochaets, L. claparedeianus was hermaphrodite where male and female organs appeared simultaneously over transparent body wall (Fig. 2a). Paired penial sheath distinguishable in segments XI was one of the main identifying characteristics (Fig. 2: a, g).

Table 2. Abundance (mean ± SD) of L. claparedeianus.

Fig. 2. (a) Anterior end of L. claparedeianus, location of penial sheaths (arrow) and clitellum (ellipse). (b) Conical head region of L. claparedeianus. (c) Dorsal and ventral chaetae. (D) Location of dorsal (upper arrow) and ventral chaetae (lower arrow). (E, g) micrographs and (h, k) Schematic figures of penial sheath anterior end. (f) Penis (arrow) located within the transparent penial sheath.

Fig. 3. Seasonal mean abundance of L. claparedeianus.

Table 3. List of identified oligochaetes in Anzali Wetland (JICA, 2005).

Fig. 4. Spatial mean abundance of L. claparedeianus

Fig. 5. Mean abundance of L. claparedeianus in 13 stations is compared in four seasons.

Table 3. List of identified oligochaetes in Anzali Wetland (JICA, 2005).