The aim of this study was to investigate how various diets influence testis maturation stages in mud crab (Scylla olivacea)
broodstock. Morphological and histological assessments were performed in triplicate (10 male crabs each). Daily,
subject crabs were fed a squid (Loligo sp.) and a fish (Decapterus sp.) diet at 5-10% of body weight. Diets were analyzed
following methods from the Association of Analytical Communities (AOAC). In comparison to control (wild) crabs, the
two diets generally did not cause significant differences (p>0.05) in body weight, carapace width and gonadosomatic
index (GSI), except in the GSI of squid-fed crabs (p<0.05). At the end of the experiment, crabs that reached Stage 3 testis
maturation included were 6 fish-fed individuals and 23 squid-fed individuals. Additionally, differences in crude protein
and fat levels across diets influenced the nature of male gonadal development. In conclusion, a squid diet was sufficient
to induce Stage 3 testis maturation in Scylla olivacea within 60 days of culture. Our results prove the usefulness in
developing appropriate feeding regimes for male Scylla olivacea broodstock.
The objectives of this study were to determine the effect of different cryoprotectants and sperm densities for longterm storage of orange mud crab, Scylla olivacea spermatozoa. Spermatozoa were obtained by homogenizing the spermatophores using a glass homogenizer in an ice-bath followed by centrifugation at 4°C. Spermatozoa were then suspended in calcium-free saline (Ca-F saline) containing 5% of the following cryoprotectants: Glycerol, dimethyl sulfoxide (DMSO) and methanol. Sperm which vibrated and rotated were counted as live during sperm viability assessment. Samples of spermatozoa were cooled to -196°C by two-step freezing, first to -80°C and then by plunging into liquid nitrogen (LN). Spermatozoa were gradually cooled at 1°C/min. Thawing was carried out in a 30°C water bath for 2 min. This yielded live sperm after storage in LN for 30 days. The best sperm viability was obtained from a density of 108 cells per mL in DMSO. There was no significant difference (p>0.05) among cryoprotectants toward sperm viability. However, sperm viability was significantly affected (p>0.05) by cell densities. In conclusion, DMSO gave the best protection to sperm cells of S. olivacea, but the effectiveness of DMSO as a cryoprotectant is influenced by sperm density.
This study was aimed to determine the ovarian maturation stages of wild and captive orange mud crab, Scylla olivacea fed with different diets via gonadosomatic status, oocyte diameter and histological examinations. Captive crabs were fed with blood cockle, Anadara granosa, or fish, Decapterus spp. Through the histological examinations, ovarian maturation stages of wild and captive S. olivaceawas classified into four stages: Immature (Stage 1), Early maturing (Stage 2), Pre-maturing (Stage 3) and Fully matured (Stage 4). Gonadosomatic Index of wild and captive crabs remained low during immature and 2 but increased significantly (p<0.05) in pre-maturing and 4 ovaries. Oocytes size were significantly different (p<0.05) in all ovarian maturation stages of wild and captive crabs. Follicle cells surround the oocyte of immature ovary and small yolk globules start to appear in early maturing ovary with large nucleus size. Oocyte size increased significantly (p<0.05) and yolk globule obviously appeared in pre-maturing ovary. Large and fused yolk globules appeared in the oocytes of fully matured ovary with nucleus was barely visible. The present study revealed that, ovarian maturation stages of S. olivacea are closely related to its morphological appearance and cellular development.
The body characteristics and yield indices of Clarias gariepinus, Bagrus bajad, Synodontis nigrita, Labeo senegalensis and Mormyrus rume from lower Benue River in Nigeria were determined in this study using 60 samples each for the fish species. Length, weight and fillet correlations were also determined during the study. Results obtained showed that M. rume, L. senegalensis and C. gariepinus had the highest percentage of edible parts (≥ 55%) compared to the other species (≤ 39%). Concerning correlations of the fillet with the morphological variables, results obtained suggest that fillet yield is independent of fish size (except for C. gariepinus which was positively correlated). Also, only samples of L. senegalensis showed isometric growth pattern; the other fish species had either positive (C. gariepinus and B. bajad) or negative (S. nigrita and M. rume) allometric growth. While the difference in fillet yield and body characteristics was attributed to the structural anatomy and other biological dynamics of the fishes, this study could not establish a connection between fillet yield and the length-weight relationship. It was concluded that M. rume, L. senegalensis and C. gariepinus would be better export products because of their higher fillet yields.