Abstract
Investigations on the incidence of septate gregarines in shrimp have immense importance because of severe pathogenicity of the parasite. The septate gregarines infect the midgut of shrimp Peneaus monodon and severe infection disturbs the intestinal tissues. Mostly gregarines of the genus Nematopsis have been identified from cultured peneaid shrimp. It has worldwide in distribution. In India, gregarine parasites have so far been reported from penaeid shrimps of Bombay and Kerala. The species which was isolated from the midgut of shrimp Peneaus monodon collected from Kharibari area of Sunderbans. 9 out of 20 i.e. 45% of the randomly sampled hosts were found to be infected with a species of the genus Nematopsis. Different developmental stages including trophozoites, sporadins, and gametocysts of the Nematopsis sp. infecting the shrimp have been isolated. No correlations have been established between incidence of infection and environmental parameters.
Keywords: Nematopsis sundarbanensis, Peneaus monodon, Septate gregarines, Gut parasite, Sundarbans
Introduction
Gegarines are a diverse and successful group of protozoan parasites belonging to the phylum Apicomplexa, order Eugregarinorida Leger, 1900. The Eugregarinida are all parasitic and are restricted to invertebrates (Clopton 2002). Cephalobolus Kruse, 1959 and Nematopsis Schneider, 1892, are two common genera found in cultured penaeids (Lotz and Overstreet 1990; Lightner 1996) and other decapod crustaceans. Different stages of life cycle are isolated from gut of the host but oocysts of Nematopsis were also isolated from gills of mussels and oysters (Padovan et al. 2003). In India the gregarine parasites have been reported from penaeid shrimps of Bombay (Bower et al. 1994) and Kerala (Prasadan and Janardanan 2001). The paper deals with the incidence of septate gregarines from Peneaus monodon of Sundarbans, West Bengal.
Materials and methods
Host specimens were randomly sampled from the farms of Kharibari and Canning stations of Sundarbans region, West Bengal and brought alive to the laboratory or in moribund condition. In the laboratory the gut of the shrimps were removed aseptically with fine forceps, gut materials were scrapped out on glass slides in 0.8% saline and examined under phase contrast microscope for detection of fresh gamonts. The smeared slides are air-dried, fixed in methanol and stained in Giemsa for permanent preparation. Measurements of the trophozoites were taken with the aid of a calibrated ocular micrometer. All measurements are presented in μm as mean (±) SD followed in parentheses by the range. Drawings were made on stained material with the aid of a mirror type camera lucida. Photographs were taken with Olympus phase contrast microscope fitted with digital camera.
Results Nematopsis sundarbanensis n. sp. (Fig. 1 A–D, E; Tables 1 and 2)
Fig. 1.
A–D: Camera lucida drawings of different stages of life cycle of Nematopsis sundarbanensis n. sp. E. Photomicrograph of a trophozoite of Nematopsis sundarbanensis n. sp
Table 1.
Measurement and statistical analysis of Trophozoites, Association and gametocyst of Septate Gregarine Nematopsis sundarbanensis n.sp
| Character | Range | Mean | SD | SE | CV% |
|---|---|---|---|---|---|
| Trophozoite: TL | 5–12.5 | 7.4 | 2.15 | 0.48 | 29.05 |
| PL | 1–3 | 1.74 | 0.563 | 0.126 | 32.35 |
| DL | 4–9.5 | 5.93 | 1.71 | 0.38 | 28.84 |
| Association length | 11.5–50.5 | 32.66 | 11.95 | 3.98 | 36.65 |
| Primite: TL | 6–21 | 15.19 | 5.85 | 1.95 | 38.51 |
| PL | 1.5–5 | 3.22 | 0.94 | 0.314 | 29.19 |
| DL | 4.5–18.5 | 11.97 | 5.75 | 1.92 | 48.04 |
| DW | 7.65–13.6 | 8.97 | 1.812 | 0.405 | 20.2 |
| PW | 4.25–8.5 | 5.95 | 1.202 | 0.268 | 20.2 |
| Satelite: TL | 5.5–24.5 | 15.13 | 6.71 | 2.33 | 44.35 |
| Gametocyst | 6.8–10.2 | 8.33 | 1.061 | 0.237 | 12.74 |
Table 2.
Morphometric comparison of the new species with previously described species of the genus Nematopsis n.sp
| Measurement | N. messor | N. quadratum | N. annulipes | Nematopsis sundarbanensis n. sp. |
|---|---|---|---|---|
| Association length | 114–178 (140.9) | 404–678 (492.7) | 213–317 (259.9) | 11.5–50.5 (32.66) |
| Primites: Total length | 59–94 (72.7) | 177–370 (285.3) | 86–185 (138.4) | 6–21 (15.19) |
| Protomerite length | 13–23 (18.6) | 53–69 (59.7) | 17–36 (28.5) | 1.5–5 (3.22) |
| Deuteromerite Width | 30–58 (40.3) | 89–162 (128.1) | 38–94 (59) | 7.65–13.6 (8.97) |
| Protomerite width | 23–43 (34) | 54–121 (90.8) | 33–56 (39.9) | 4.25–8.5 (5.95) |
| Ratio PL: TL | 1:3.9 | 1: 4.8 | 1: 4.9 | 1:4.7 |
| PW:DW | 1:1.1 | 1:1.1 | 1:1.3 | 1: 1.5 |
| Satellites Total length | 51–86 (68) | 152–308 (207.3) | 101–147 (121.4) | 5.5–24.5 (15.13) |
| Deuteromerite width | 25–46 (33.9) | 50–117 (83.1) | 26 -79 (49.2) | 6–14.5 (7.78) |
| Trophozoites: Total length | 31.3 | 56.1 | 37.1 | 5–12.5 (7.4) |
| Protomerite length | 9.9 | 13.2 | 7.4 | 1-3 (1.74) |
| Deuteromerite length | 21.4 | 42.9 | 29.7 | 4–9.5 (5.93) |
| Ratio PL: TL | 1:3.16 | 1: 4.25 | 1:5.01 | 1: 4.25 |
| PL: DL | 1:2.16 | 1: 3.25 | 1: 4.01 | 1: 4.04 |
| Gametocyst | 54–86 (66.7) | 139–246 (206.4) | 112–119 (115.5) | 6.8–10.2 (8.33) |
| References | Prasadan and Janardanan (2001) | Prasadan and Janardanan (2001) | Prasadan and Janardanan (2001 | Present study |
Sporadins: Multi associative, association caudofrontal.
Primites: These septate gregarines contain two segments i.e. protomerite and dueteromite, epimerite is absent. The protomerite is hemispherical in shape. It stains light with Giemsa. It is separated from the deuteromite by a straight septum which is constricted at the sides. The deuteromite is elongated with a slight constriction at the middle or it appears more or less dumble shaped and stains deep with Giemsa. Nucleus is ovoid in shape situated at the middle of the deuteromite.
Satellite: Protomerite absent. Only deuteromite is present. Shape of the satellite deuteromite is similar to that of primite.
Trophozoite: The mature and immature trophozoites contain only two segments i.e. protomerite and dueteromite, epimerite is absent in the septate gregarines which have been collected from the gut of shrimp. The protomerite is wide at the anterior end and narrow at the posterior end. It stains light with Giemsa. The deuteromerite is elongated with slight constriction at the middle or it appears more or less dumble shaped. It stains deep with Giemsa. A rounded nucleus is present at the middle of deuteromerite just in the region of constriction. The anterior end of the dueteromite is straight while the posterior end is blunt and rounded.
Gametocyst: Narrow at one end and broad at the other. Both the ends are rounded almost resembling the shape of a water drop. Epicyst thin. Gametocysts are surrounded by a single epicyst.
Taxonomic summary
Type specimen: Syntypes, No. Z/Par/G/6408/09; deposited in the Parasitology laboratory, Department of Zoology, University of Kalyani, West Bengal, India.
Type host: Peneaus monodon
Type locality: Canning, Matla estuary, 24 Parganas (S) and Kharibari, 24 Parganas (N) West Bengal, India
Collection time: July, August’ 2008
Site of infection: Intestine
Prevalence: 09 out of 20 hosts sampled and examined randomly. i.e. 40% of the sampled hosts are infected.
Discussion
The present species differs from other three described species namely Nematopsis messor, N. quadratum, and N. annulipes (Prasadan and Janardanan 2001) in shape and size in following significant ways:
(i) A prominent lens shaped structure is present at the anterior end of the protomerite of N. messor but it is absent in the species under description, (ii) the shape of the nucleus of the species also differs. It is ovoid in shape in the present species while it is spherical in the other species, (iii) Protomerite absent in the satellite, the described species but it is present in the other two species, (iv) Each gametocyst of the species under study resembles the shape of a water drop whereas, the gametocysts are rounded to spherical in shape in N. messor, N. quadratum and N. annupiles, (v) A single epicyst encloses the gametocyst of the present species as it is found in other two species.
In India, the gregarine parasites have so far been reported from penaeid shrimps of Bombay (Bower et al. 1994). It is the first record of septate gregarines from the Black Tiger shrimp of Sundarbans region. On the basis of above taxonomic and comparative study based on the morphology of trophozoites, sporadins, gametocysts the species described in this paper is designated as a new species under the genus Nematopsis and hence Nematopsis sundarbanensis.n.sp. is designated.
Acknowledgments
One of the authors (JC) is thankful to University Grants Commission, New Delhi for financial support to run the project (Project no. F. 32-483/2006 (SR).
Abbreviations
- SD
Standard deviation
- SE
Standard error
- CV (%)
Coefficient of curvature
- TL
Total length of the protomerite
- LP
Length of Protomerite
- WP
Width of Protomerite
- WD
Width of Dueteromerite
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