Long‐term cryopreservation of the giant freshwater prawn, Macrobrachium rosenbergii, spermatophores using glycerol (Gly) and ethylene glycol (EG) as cryoprotective agents (CPAs) was studied. The tolerance of sperm to cryopreservation was evaluated on the basis of sperm survival and fertilizing ability. The survival of the sperm was determined by trypan blue staining, while the fertilizing ability was assessed from artificial insemination of the cryopreserved spermatophores. The rates of embryo survival on day 5 after spawning and of spermatophores capable of producing embryos survived to hatching were determined. Storage of spermatophores at −20°C without CPA for a short period of up of 1–5 days decreased the sperm survival significantly and did not preserve fertilizing ability. Preservation at −20°C in the presence of 10% or 20% Gly or of 10% or 20% EG offered a simple and efficient short‐term storage up to 10 days. For a long‐term storage, cryopreservation in the presence of 20% EG at −196°C was more efficient than at −20°C. High sperm survival rates and high fertilizing ability were recorded from those cryopreserved at −196°C for up to 150 days. High sperm survival rates with moderate levels of fertilizing ability were obtained from those cryopreserved at −20°C for not more than 30 days. The results indicate that preservation at −196°C with 20% EG is a suitable procedure for long‐term storage of the giant freshwater prawn spermatophores.

The feasibility of fertilizing preovulatory lobster oocytes was examined in vitro under various experimental conditions. Large (1.6 mm diameter) and small (0.6 mm diameter) oocytes were compared in fertilization trials. Small oocytes were surrounded by a thin envelope thought to correspond to envelope 1A of mature oocytes. Large oocytes were surrounded by a fully formed vitelline envelope comprised of two distinct sublayers, 1A and 1B. Although sperm bound very effectively to the coat surrounding small oocytes, none penetrated the coat or fertilized the oocytes. Large diameter oocytes that were removed from follicles by dissection were fertilized by sperm from the proximal vas deferens of males and by sperm from the seminal receptacle of females. Fertilized oocytes showed a high degree of polyspermy. Higher numbers of sperm bound to, penetrated, and fertilized large diameter oocytes when inseminations were done in a saline solution (2.5LSH) than when done in artificial sea water (ASW). Sperm failed to bind to large diameter oocytes that were induced to ovulate in vitro by collagenase treatment. Contaminating enzymes may have destroyed the sperm receptor in envelope 1A of collagenase treated oocytes. Our in vitro fertilization method will allow the process of fertilization to be studied experimentally in lobsters, and it may be applicable to other decapods.Many aspects of lobster (Homarus) reproductive biology have been well characterized in numerous studies done during the past 100 years (reviewed by Aiken and Waddy, '80; Talbot, '90). The structure of the gametes has been examined in considerable detail at both the light and electron microscopic level (Herrick '09; Kessel, '68; Talbot, '81a,b; Pochon Mason, '68; Talbot and Chanmanon, 80a; Schade and Schivers, '80). Morphological changes occurring in sperm during the acrosome reaction have also been described (Pochon-Mason, '68; Talbot and Chanmanon, '80b), and the role of the cortical reaction in formation of the fertilization envelope has recently been analyzed (Talbot and Goudeau, '88).In spite of much interest in this topic, relatively little is known about the mechanism of fertilization in Homarus americanus. This is due to the biennial ovarian cycle characteristic of this species and the difficulty in obtaining ovulated unfertilized oocytes or freshly spawned oocytes. Studies of gamete interaction in the lobster would be facilitated by an in vitro technique for fertilizing eggs. Goudeau and Goudeau ('86) have successfully fertilized lobster eggs in vitro using sperm from the seminal receptacle of a female that was spawning. To catch a female in spawning, however, requires constant monitoring of mature females and is not practical for most experimental applications.The main purpose of this study was to examine the feasibility of fertilizing preovulatory lobster oocytes in vitro. Oocytes were collected from ovaries by dissecting them free of follicle cells and inseminating them in vitro with sperm from either the proximal vas deferens (PVD) of males...

The effect of photoperiod on growth of juvenile giant freshwater prawns, Macrobrachium rosenbergii de Man, was tested. The prawns were divided into four groups and each group was reared under one of the following light-dark conditions: continuous darkness (L0:D24), 12 hr light: 12 hr dark (L12:D12), 16 hr light: 8 hr dark (L16:D8), and 20 hr light: 4 hr dark (L20:D4). Body size was determined at the age of 45, 75, and 110 days by measuring total length, orbital length, and carapace length; body weight was determined at the age of 110 days. At 110 days of age, the prawns reared under L0:D24 photoperiod were significantly longer and heavier than those reared under other light-dark conditions. The survival rate of the prawns reared under L0:D24 photoperiod was also higher than that of other groups. This study indicates a positive effect of continuous darkness on growth and survival rate of juvenile giant freshwater prawns, M. rosenbergii.

Figure 4 Percentages of female prawns administered with a single injection of various concentrations of 5-hydroxytryptamine (5-HT) or octopamine (OA) exhibiting spawning at di¡erent periods of the day.Aquaculture Research, 2006, 37, 1259^1261 Ovarian development and spawning in Macrobrachium rosenbergii S Tanboonteck et al.