Eyestalk Ablation to Increase Ovarian Maturation in Mud Crabs

Summary

Two eyestalk ablation protocols (i.e., cauterization and surgery approaches) were performed on anesthetized female crabs. The eyestalk ablation of mud crabs hastened the ripening of ovaries without decreasing the survival rate.

Abstract

Mud crabs (Scylla spp.) are commercially important crustacean species that can be found throughout the Indo-West Pacific region. During culture, the induction of ovarian maturation is important to meet the consumer demand for mature mud crabs and hasten seed production. Eyestalk ablation is an effective tool to enhance ovarian maturation in mud crabs. However, there is no standard protocol for the eyestalk ablation of mud crabs. In this study, two eyestalk ablation techniques are described: cauterization (the use of hot metal to ablate the eyestalk of an anesthetized crab) and surgery (the removal of the eyestalk using surgical scissors). Before eyestalk ablation, sexually mature females (CW > 86 mm) were anesthetized using an ice bag (−20 °C) with seawater. When the water temperature reached 4 °C, the ice bag was removed from the water. Flowing seawater (ambient temperature: 28 °C) was used for recovery from the anesthesia immediately after eyestalk ablation. Mortality did not occur during or after the process of eyestalk ablation. The eyestalk ablation protocol presented here accelerated the ovarian maturation of the mud crabs.

Introduction

All four mud crab species belonging to the genus Scylla are commercially important crustacean species in aquaculture^1,2. The growth of crustaceans, including mud crabs, and their transformation from the pre-mature (sub-adult or pubertal) phase to the sexually mature (adult) phase occur through a molting process that involves the periodic shedding of older and smaller exoskeletons. Carapace width (CW), chelipeds, and abdominal flap morphologies are widely used to determine the sexual maturity of Scylla spp.^3,4,

Protocol

This protocol follows the Malaysian Code of Practice for the Care and Use of Animals for Scientific Purposes outlined by the Laboratory Animal Science Association of Malaysia. The sacrifice of the experimental samples was done according to the National Institutes of Health Guide for the Care and Use of Laboratory Animals (NIH Publications No. 8023, revised 1978). Sexually pre-mature female mud crabs (orange mud crab S. olivacea) were collected from the local market (5°66′62′′N, 102°72.......

Discussion

This protocol was developed for the eyestalk ablation of the mud crab, Scylla spp., and can be applied as an efficient method to induce gonad maturation. This protocol can be easily replicated for the commercial ovary maturation of mud crabs and can be implemented to reduce the latent period (time from one spawning to another) in mud crab seed production.

The eyestalk ablation of crustaceans (i.e., freshwater prawn, marine shrimp) is typically done to induce gonad maturation and out-o.......

Materials

Name	Company	Catalog Number	Comments
Aeration tube	Ming Yu Three	N/A	aquarium and pet shop
Airstone	Ming Yu Three	N/A	aquarium and pet shop
Autoclave machine	HIRAYAMA MANUFACTURING CORPORATION	N/A	MADE IN JAPAN
Bleaching powder (Hi-Chlon 70%)	Nippon Soda Co.Ltd,Japan	N/A	N/A
Blow torch	MR D.I.Y. Group Berhad	N/A	N/A
Circular tank (32L)	BEST PLASTIC INDUSTRY SDN. BHD.	N/A	N/A
Cotton hand gloves (thick)	MR D.I.Y. Group Berhad	N/A	N/A
Cotton towel	MR D.I.Y. Group Berhad	N/A	N/A
Digital thermometer	Hanna Instrument	HI9814	Hanna Instruments GroLine Hydroponics Waterproof pH / EC / TDS / Temp. Portable Meter HI9814
Digital Vernier Caliper	INSIZE Co., Ltd.	N/A
Dissecting tray	Hatcheri AKUATROP	N/A	Research Center of Universiti Malaysia Terengganu
Dropper bottle/Plastic Pipettes Dropper	Shopee Malaysia	N/A	N/A
Ethanol 70%	Thermo Scientific Chemicals	033361.M1	Diluted to 70% using double distilled water
Fiberglass tank (1 ton)	Hatcheri AKUATROP	N/A	Research Center of Universiti Malaysia Terengganu
Fine sand	N/A	N/A	collected from Sea beach of Universiti Malaysia Terengganu
First Aid Kits	Watsons Malaysia	N/A	N/A
Flat head nickel steel metal rod (Screw driver)	MR D.I.Y. Group Berhad	N/A	N/A
Formaldehyde	Thermo Scientific Chemicals	119690010
Gas cylinder (butane gas) for blow  torch	MR D.I.Y. Group Berhad	N/A	N/A
Gas lighter gun (long head)	MR D.I.Y. Group Berhad	N/A	N/A
Glass beaker (100 mL))	Corning Life Sciences	1000-100
Ice bag	Watsons Malaysia	N/A	N/A
Perforated plastic baskets	Eco-Shop Marketing Sdn. Bhd.	N/A	N/A
PVC pipe 15mm	Bina Plastic Industries Sdn Bhd (HQ)	N/A	N/A
Refractometer	ATAGO CO.,LTD.
Refrigerator	Sharp Corporation Japan	N/A	Chest Freezer SHARP 110L - SJC 118
Scoop net	MR D.I.Y. Group Berhad		N/A
Seawater	Hatcheri AKUATROP	N/A	Research Center of Universiti Malaysia Terengganu
Siphoning pipe	MR D.I.Y. Group Berhad	N/A	N/A
Spray bottle	Mr. DIY Sdn Bhd	N/A	N/A
Stainless surgical forceps	N/A	N/A	N/A
Stainless surgical scissors	N/A	N/A	N/A
Submersible water pump	AS	N/A	model: Astro 4000
Tincture of iodine solution  (Povidone Iodine)	Farmasi Fajr Sdn Bhd	N/A	N/A
Tissue paper	N/A	N/A
Transparent plastic aquarium	Ming Yu Three	N/A	aquarium and pet shop
Waterproof table	Hatcheri AKUATROP	N/A	Research Center of Universiti Malaysia Terengganu