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Age and Size at Sexual Maturity of Same Age Group of Male Green Mud Crab (scylla Paramamosain)

Md. Latiful Islam
Centre for Marine and Coastal Studies, Universiti Sains Malaysia, Penang, Malaysia

Mollah NS Mamun Siddiky
Bangladesh Fisheries Research Institute, Brackishwater Station, Paikgacha, Khulna, Bangladesh

Abstract/ Executive Summary:

The present study was conducted to elucidate the age at sexual maturity and transformation of secondary organs of male mud crab. Five crabs were dissected at 15 days interval; testes were collected and preserved in Davidson’s fixatives for 24 hours, then transferred to 50% ethanol. Samples were chronologically dehydrated in 70% to 100% ethanol at 10% intervals; embedded, sectioned at 6 µm, stained with Haematoxylene-Eosin and observed under stereo microscope. Present observation revealed three distinct sexual maturation stages of male mud crab (Scylla paramamosain) with first sexual maturation in four months of age. Internal carapace width (ICW) showed discrete relation with external morphological features at ICW of 10.20 cm at pubertal molting. Asynchronies maturation was noticed with first fully sexually matured crab (20%) in 5th month of age and the median sexual maturity (MA50) occurs in 6.5 month of age. Findings of the present study suggested to being ready for captive mating of mud crab within 4 months of age after crab instars.

Keywords: Age, Sexual maturity, Same age group, Male, Mud crab

Location: Universiti Sains Malaysia (USM), Penang

Start Date: 00-00-2012

End Date: 00-00-2015

Program Area: Animal Health and Management

Commodity: Crab

Objectives:

The ultimate aims of this study are to identify the age at first maturity, major features of gonad at different development stages and to establish the maturity levels with external morphological features of the male green mud crab for setting proper matting protocols under captive condition.

Methodology:

Study site The experiment was conducted at the Centre for Marine and Coastal Studies (CEMACS) under Universiti Sains Malaysia (USM), Penang, Malaysia during 2012 to 2015. The study site located at North-East part of Penang Island under 5° 28' 2.3664''N and 100° 12' 2.8728''E in Global Positioning System (GPS). Source of experimental crabs Animal samples were managed by breeding the natural base female (P0) and consequent rearing the larvae in hatchery condition followed by communal growing the juvenile male crabs under captive condition in fiber glass tanks with a density of 2 crabs/m². Collection of crabs and measurement As the crabs reaches 4 months of age, 5 male crabs were randomly collected at 15 days intervals, euthanized by thermal-shock at −20 °C for 30 min, measured (TW: total weight and CW: carapace width) and recorded for each crabs. The allometric growth organs (propodus length, propodus width and chela height) were measured for each crab with the help of slide caliper following standard methods. 2.4 Dissection of crabs, gonad sample collection and preservation The anesthetized crabs were taken out from the freezer, the anterolateral and frontal spines were dissected. The upper cover (carapace) was gently removed to open the ovary/gonad. Necessary pictures on gonad morphological features were taken with a digital camera (Panasonic, DMC-FH25). The testis was gently removed, weighed followed by drying with blotting papers. The whole testes for each crab was separately preserved in Eppendorf tube filled with Davidson’s fixatives for 24 hours, then transferred to 50% ethanol until histological process performed. Histological slide preparation and observation Histological slide of gonad tissues were prepared through routine histological procedures of dehydration in ascending order of ethanol starting from 70% and ended at 100% at 10% intervals, xylene treatments, embedded in paraffin wax blocks, sectioning at 6 µm, placed onto a glass slide and stained with Haematoxylene-Eosin. The stained tissues were covered with a cover slip and observed under a light stereo microscope. Images of the cells of gonad development stages were taken by using a digital computer with an image capture analysis system (Image Cell B, Stereomicroscope, Camera-X cam-α, Olympus SZX91CAS, Japan). Histological classification of gonad development stages was performed according to previous author. Data was analyzed using Microsoft Excels 2010 and SPSS 20.

Source of Information: Journal of Entomology and Zoology Studies 2018; 6(5): 366-371 E-ISSN: 2320-7078 P-ISSN: 2349-6800

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Mud crab as a marine breeder crustacean required suitable environmental conditions for growth, maturity and reproductive development. Male mud crabs showed stepwise maturation with progress of age and size. Despite the same age group of population, a portion of male showed faster sexual maturity, whereas, the majority began maturing uniformly and the least portion showed slow maturation. First sexual maturity was noticed in 4 month of age and attained fully mature in 5 month of age. Depending on the age of male sexual maturity, this study suggested to being ready within 5 month of age for captive mating. However, this noteworthy observation on age at sexual maturity of male mud crab could be the footprint for setting up of further research on captive mating for genetic selection, line breeding and disease resistance.

Knowledge Management: Journal