R. N. Singhal

The effects of argulosis-saprolehniasis on the growth and production of Cyprinus carpoi

Growth profiles of male Cyprinus carpio, 12 uninfected (healthy) and 12 infected with the crustacean Argulus indicus and associated fungus Saprolegnia sp. are presented. The fish were maintained under controlled conditions and provided with ad libitum food for 8 weeks. The instantaneous (G) and relative (h) rates of growth, and production (P) in uninfected carp (0.003 to 0.036 g.d−1, 0.29 to 3.68%, 0.25 to 3.23 g respectively) were much higher than those of infected carp ( − 0.007 to 0.021 g.d −1, 0.71 to 2.17%, 0.59 to 1.76 g). The condition factor (K) for uninfected carp was 4.5 to 4.8 compared to 2.6 to 3.0 for infected carp. During each of the 8 wk the weekly change in weight of infected carp was about 4% less than that of uninfected carp. These data show that Argulus-Saprolegnia infections significantly suppress carp growth and indicate that comparative growth rates can be used as indicators of parasite stress.

Chemotherapy of six ectoparasitic diseases of cultured fish.

Abstract Periodic observations on ectoparasite infections of Saprolegnia, Trichodina, Myxobolus, Hemiclepsis, Argulus , and Posthodiplostomum on cultured fish were made at the Central Inland Fisheries Research Institute, Karnal and the Haryana Government Fish Seed Farm, Jyotisar (Kurukshetra) from August 1982 through July 1983. Chemotherapeutic control of the ectoparasites by gammexane (1-6-hexachlorocyclohexane), sodium chloride, formalin, potassium permanganate, malachite green, glacial acetic acid, calcium oxide, calcium hydroxide and picric acid was investigated. Malachite green and sodium chloride solutions were most effective on Saprolegnia ; sodium chloride, acetic acid or formalin on Trichodina ; calcium hydroxide, calcium oxide, potassium permanganate or formalin on Myxobolus ; glacial acetic acid and potassium permanganate on Hemiclepsis ; and gammexane on Argulus . None of the chemicals tested was effective on fish heavily infected with Posthodiplostomum although picric acid was successful on less heavily infected fish.

The physico-chemical environment and the plankton of managed ponds in Haryana, India

An investigation was made of the physical, chemical conditions of the water and substrate of nursery-cum-research-cum-rearing-cum-stocking ponds at Central Inland Fisheries Research Institute, Karnal. Temperature, pH, CO2, dissolved oxygen, chloride, phosphate, alkalinity, nitrates, organic matter, total solids, turbidity, electric conductivity, nitrogen, P2O5, sand, silt, clay, CaCO3, etc. were measured monthly. Statistical analysis of these factors showed some significant correlations. The phyto- and zooplankton were also sampled and the seasonal changes in abundance recorded.

Experimental transmission of Saprolegnia and Achlya to fish

Abstract Experiments were conducted to determine the mode of transmission of saprolegniasis by Saprolegnia diclina Humphrey- S. parasitica Coker complex and Achlya racemosa in Cyprinus carpio (common carp), Labeo rohita (rohu) and Cirrhina mrigala (mrigal). The fish were exposed to A. racemosa and S. parasitica by direct contact, scale removal or intramuscular injection. The results of these experiments indicate that natural infection is primarily brought about through surface abrasions.

Histopathology of hyperoxia in Nephelopsis obscura (Hirudinoidea: Erpobdellidae)

Abstract Small (10–15 mg) and large (300–350 mg) Nephelopsis obscura in the laboratory were exposed to supersaturated oxygen (250–300% saturation) at 4° and 15°C simulating winter and summer field conditions in southern Alberta. The results for both weight groups at both temperatures were very similar. Depigmentation, lethargy, and swelling of tissues were observed after 12 days, and after 14 days exposure histopathology showed lesions in the brain, subesophageal ganglia, nerve cord, ventral ganglia, epidermis, and muscles and oxygen emboli throughout the muscular and connective tissues.

Effects of anoxia and hyperoxia on the neurons in the leech Nephelopsis obscura (Erpobdellidae): Ultrastructural studies

Abstract The ultrastructure of neurons in the leech Nephelopsis obscura exposed to anoxic or hyperoxic conditions in the laboratory were studied and compared with neurons in normoxic control animals. Oxygen stress alters the shape and structure of membranous organelles, including mitochondria, endoplasmic reticulum, and Golgi complex, and also damages nuclear and cytoplasmic membranes. Mitochondria, ribosomes, and neurotransmitter vesicles are all markedly reduced in number and become swollen with fragmented cristae in neurons exposed to either anoxia or hyperoxia. Clumping of nuclear chromatin, dilatation of the Golgi complex, degranulation of the endoplasmic reticulum, loss of neurotransmitter vesicles, and degenerative changes are more severe in neurons following anoxia than in those exposed to hyperoxia. These morphological changes may partly explain the behavior of freshwater invertebrates exposed to wide seasonal fluctuations in oxygen concentration of lake or pond water.

Karyology of Erpobdella Punctata and Nephelopsis Obscura (Annelida: Hirudinoidea)

SUMMARYMeiosis of Erpobdella punctata and Nephelopsis obscura (Hirudinoidea: Erpobdellidae), has been studied in both testes and ovaries. At prophase I and metaphase I eight bivalents occurred in the majority of the nuclei in E. punctata; eleven in N. obscura. Spermatogonial metaphases showed 16 and 22 chromosomes in E. punctata and N. obscura, respectively. It was therefore concluded that the chromosome number of E. punctata is n = 8, 2n = 16 and N. obscura is n = 11, 2n = 22. These findings—the first for North American leeches—are discussed in relation to the chromosome evolution and phylogenetic schemes proposed by previous authors for the Hirudinoidea.

Descriptions of the Reproductive Organs of Nephelopsis obscura and Erpobdella punctata (Hirudinoidea:Erpobdellidae)

During the study of the anatomy of mature Nephelopsis obscura and Erpobdella punctata the structure and distribution of the male and female reproductive organs were observed. The gonopores in N. obscura and E. punctata were separated by one and two annuli, respectively. In N. obscura, the multifollicular testes lie in two lateral columns in the form of bunches occupying the posterior third quarter of the body. Two U-shaped, elongated and tubular ovaries were present dorsal to the sperm duct and ventral to the alimentary canal, occupying five segments (XIII to XVII). The ratios between the body length and the length of the gonads (ovaries and testes) varied between 0.22 and 0.81. The length ratio of the testes to the ovaries ranged from 0.27 to 0.30. The reproductive organs of E. punctata were similar, although the ovaries and testes were longer.

Unimpaired RNA synthesis in neurons and epithelial cells in a freshwater leech exposed to the organophosphate insecticide chlorpyrifos

Chlorpyrifos (Dursban) is an organophosphate insecticide widely used mainly for control of mosquito larvae. This study used the dominant freshwater leech Nephelopsis obscura as a representative aquatic invertebrate to test toxicity of chlorpyrifos on a nontarget species. RNA synthesis in neurons of the cerebral ganglion, epithelial cells of the intestine, and the tegument of small immature (50-70 mg) and large mature (300-400 mg) N. obscura was examined histochemically with acridine orange fluorochrome after exposure to chlorpyrifos in concentrations of 16, 32, 64, 128, and 144 ppb for as long as 6 weeks. The maximum environmental concentration of this insecticide in lake water, when used properly, is 4.25 ppb. There was no mortality, and no behavioral changes were observed in experimental animals, except for transient curling and cutaneous mucus secretion at the highest concentrations of chlorpyrifos. No pathological changes were observed in the intensity of RNA fluorescence or in the distribution of RNA within the cytoplasm of neurons or epithelial cells in any specimens, unlike N. obscura exposed to anoxia, hyperoxia, or salinity. Chlorpyrifos in the concentrations studied does not appear to adversely affect nucleic acid metabolism in N. obscura.

Cosexuality in the Leech, Nephelopsis obscura (Erpobdellidae)

Summary Hermaphroditism of the erpobdellid leach Nephelopsis obscura is described on the basis of macroscopic and histological studies of the gonads. Perivitellogenic cells (female primordial germ cells) proliferate from the septa of segments XII and XIII in individuals of 26–30 mg and spermatogenic cells from segments XII to XIII of 20–25 mg specimens. The majority of hatch- lings develop functional testisacs when they reach 170 mg and functional ovisacs when they reach 250 mg. Oocytes proliferate only after the formation of stage 5–6 spermatozoa. Thus, N. obscura is a sequential cosexual hermaphrodite with spermatogenesis and mature spermatozoa development commencing before oogenesis. During the second cycle of gametogenesis observed in larger animals, both mature spermatozoa and ova co-occur and N. obscura exhibits simultaneous hermaphroditism.