Irregular helicoids in leech cocoon membranes.
ABSTRACT Helicoids in the cocoon membrane of leeches Theromyzon tessulatum and Erpobdella punctata comprise a twisted superposition of layers, each containing a variable number of planes formed by unidirectional fibrils. Straight fibrils intersecting at different angles were displayed in tangential sections through the cocoon wall of each species. When the sectioning angle was below a certain value (i.e., the critical angle), bow-shaped lines apparent in oblique sections were replaced by a succession of layers containing straight fibrils, permitting a direct measurement of step-angle change between successive layers in a helicoid. By this methodology, we determined that no regularities exist in the succession of step-angles or in layer thicknesses within the cocoon membranes, but that the distribution of step-angles between layers was unique for each cocoon type.
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ABSTRACT: Clitellate annelids (i.e., oligochaetes including leeches) secrete cocoons as part of their normal reproductive cycle. Typically, the cocoon sheath is passed over the head of the leech and sealed at both ends by opercula (i.e., glue-like material secreted by the clitellum). Both the fibrous cocoon wall (CW) and opercula are chemically-related biomaterials that share unusual physiochemical properties, including thermal and chemical resiliency. To explore the underlying morphology of the operculum, we examined cocoons from four leech species (i.e., Myzobdella lugubris, Theromyzon tessulatum, Erpobdella obscura, and Erpobdella punctata) by transmission (TEM) and scanning electron microscopy (SEM). Transmission electron micrographs of all opercula revealed a common, ultrastructural pattern comprising an electron-dense mosaic of ordered polygons that surrounded interspersed cavities. The long axes of cavities were often oriented directionally, suggesting that operculum material is pliable prior to solidification and distorted as a consequence of cocoon deposition. Concomitantly, the operculum permeates jagged edges of the cocoon sheath sealing the cocoon, which provides a mechanically strong CW/operculum boundary. SEM of leech opercula revealed globular nanoparticles comparable to that observed in bioadhesives from disparate animal phyla (e.g., mussel, barnacle, sea star), suggesting a convergent mechanism of bioadhesion among animals. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.Journal of Morphology 08/2013; 274(8). DOI:10.1002/jmor.20150 · 1.55 Impact Factor
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ABSTRACT: The leech Hirudinaria manillensis, Lesson 1842 is of much interest for clinical and medicinal use. In this study, the effect of broodstock density (5, 10, 15, 20, 25, 30 and 50 ind tank− 1) on the reproductive efficiency of H. manillensis was examined. After 4 months of culture, the number of cocoons produced was significantly different among the different broodstock densities (F6, 34 = 4.560, P < 0.05), but fertilization ratio was not (F6, 34 = 1.319, P = 0.285). The average number of hatchlings per cocoon (5.72 ± 0.13 ind) and hatching rate (96.82 ± 1.31%) of the cocoons in the 5 ind tank− 1 treatment were significantly higher than those of the other treatments. The 50 ind tank− 1 treatment had the highest mortality of parent leeches (29.60 ± 2.48%). The size and wet weight of the cocoons were significantly different among the treatments, with the 5 ind tank− 1 treatment having the largest cocoon size (standard length and diameter) and wet weight. The time of juvenile release from the cocoons did not differ significantly among the different broodstock densities (P > 0.05).The effect of diet (FT1: live bullfrog, FT2: fresh cattle blood, and two blood plasma preparations FT3: NP-2002a and FT4: NP-2002b) on the feeding, growth and survivorship of the juvenile leeches was also studied. After 2 months of culture, juveniles in the FT2 (fresh cattle blood) treatment had the highest total food intake (13.11 ± 0.07 g). Juveniles in the FT3 (NP-2002a) and FT1 (live bullfrog) treatments had a significantly high feeding ratio 95.00 ± 1.16% and 91.33 ± 1.20%, respectively. Percentage weight gain (WG) and specific growth rate (SGR) of the juveniles in the treatment FT4 (NP-2002b) were the lowest, at 168.52 ± 15.82% and 1.64 ± 0.10%, respectively. Juveniles in the FT3 (NP-2002a) and FT4 (NP-2002b) treatments had the highest survival rates, at 96.00 ± 0.58% and 84.33 ± 0.88%, respectively.Aquaculture 04/2008; DOI:10.1016/j.aquaculture.2008.02.003 · 1.83 Impact Factor
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ABSTRACT: Leeches (Phylum: Annelida, Class: Hirudinea) are widely distributed all over the world in various habitats, such as freshwater, seas, desert, and oases (Gouda, 2006). In this study, the effect of light intensity, temperature and diet on the reproductive efficiency of Hirudinea sp. was examined with eight different conditions. After 3 months of culture, the number of cocoons produced was very significantly different among the different conditions (p=0.00). The average number of hatchlings per cocoon was significantly different (p # 0.05) where condition 1 gave the highest number (6.23±0.25), but hatching rate was not (p=0.354). The condition 5 produced the highest mortality of parent leeches (52±13.86%). The sizes of the cocoons were not significantly different among the treatments, with the condition 1 having the largest cocoon of 22.19±0.92mm and 13.26±0.07mm according to their length and diameter, respectively. The wet weight of cocoons was significantly different (p # 0.05) with the condition 1 producing the heaviest cocoons of 1.26±0.11g compared to condition 5 producing the lightest cocoons of 0.22±0.38g. The effect of diet (FT1: fresh eel blood and FT2: booster) on the growth and survivorship of the juvenile leeches was also studied. After 2 months of culture, the final body weight was significantly different among the treatments, with juveniles in the FT1 (fresh eel blood) had the highest final body weight (0.8893±0.012g). Percentage weight gain (WG) and specific growth rate (SGR) of the juveniles in the treatment FT2 (booster) were lowest with mean and standard deviation of 769.41±11.54% and 3.6±0.02%, respectively. Juveniles in the FT2 (fresh eel blood) treatment had the highest survival rate (93.33±5.77%).