Dataset on reproductive status of ovary mud crab at different salinity levels

This article investigated how crabs responded to different culture salinities through ovarian maturation stages using combination of external morphology (ovarian coloration and gonadosomatic index), and histological assessment (oocyte structures and diameter sizes). A total of sixty immature crabs were sampled from coastal water of Setiu Wetlands, Kuala Nerus, Terengganu, Peninsular Malaysia, and were introduced to limb autotomy technique in order to induce molt. Crabs were reared until successfully molted, and leaves prior to hardened shell, before proceed with salinities acclimatization prior to salinity treatments (10, 20 and 30 ppt). Five crabs were randomly selected every 15 days throughout 60-day of culture (Day 15, 30, 45 and 60) for the assessment. The different between each ovarian maturation stages was recorded based on the color appearances, and Kruskal-Wallis analysis were done between gonadosomatic index and oocyte diameter sizes with different salinity treatments. Part of the data is associated with the recent articles [1], [2] and provided here as raw data of Supplementary materials.


a b s t r a c t
This article investigated how crabs responded to different culture salinities through ovarian maturation stages using combination of external morphology (ovarian coloration and gonadosomatic index), and histological assessment (oocyte structures and diameter sizes). A total of sixty immature crabs were sampled from coastal water of Setiu Wetlands, Kuala Nerus, Terengganu, Peninsular Malaysia, and were introduced to limb autotomy technique in order to induce molt. Crabs were reared until successfully molted, and leaves prior to hardened shell, before proceed with salinities acclimatization prior to salinity treatments (10, 20 and 30 ppt). Five crabs were randomly selected every 15 days throughout 60-day of culture (Day 15, 30, 45 and 60) for the assessment. The different between each ovarian maturation stages was recorded based on the color appearances, and Kruskal-Wallis analysis were done between gonadosomatic index and oocyte diameter sizes with different salinity treatments. Part of the data is associated with the recent articles [1,2] and provided here as raw data of Supplementary materials. © 2019 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4.0/).

Data
Included in this article are the raw data, descriptive data (means), and Kruskal-Wallis test on the effects of different water salinities on ovarian maturation stages of the orange mud crab, Scylla olivacea. The shared data are recordings from the works starting from the sampling site, which involved the mud crabs sampling activities, proceed with hatchery phases (rearing periods for limb autotomy procedure, acclimatization period, and salinity treatments), and laboratory works, where the assessment activities were performed e external morphology and histology determination; percentage of ovarian maturation based on coloration (Sheet 1), gonadosomatic index (Sheet 2), oocyte diameter sizes (Sheet 3), and characterization of external morphology and microscopic observation on each maturation stage (Sheet 4). Value of the data The high nutritional value and market demands for mature and gravid female mud crabs [1e7] has triggered the present study on ovarian maturation of mud crabs. Ovarian maturation might be one of the potential indicators [8,9] on how cultured animals adapt to fluctuating environments such as water salinity. The effects of water salinity on ovarian maturation stages (through external morphology and histological assessment) could be useful for other researchers investigating on adaptive evolution in climate change scenario for future study. Such data can be useful in developing baseline for culture purposes in captivity and hatchery practice in the future [10e13].

Sampling
A total of sixty immature female Scylla olivacea (carapace width, CW less than 9.06 cm; small and pale abdominal flap) (Fig. 1) were sampled from Setiu Wetlands Mangrove Forest, Terengganu, East Coast of Peninsular Malaysia (5 31 0 23.1 00 N 102 55 0 56.1 00 E) (Fig. 2). Conventional rectangular collapse crab pots (dimension: length x width x height ¼ 87 cm Â 56 cm x 30 cm; mesh size ¼ 1 cm) with openings at the middle of both end sections were used during sampling section [9]. Crab pots were deployed during the low tide in the evening (1600 h) and collected during subsequent low tide in the morning of the next day (0800 h). Only immature female crabs were chosen, and the crab samples were then transferred to the Institute of Tropical Aquaculture Marine Hatchery, Universiti Malaysia Terengganu for subsequent analysis.
The initial body weight (BW) and carapace width (CW) of each crab were measured and recorded. BW was measured using a digital balance (accuracy: 0.01 g; Shimadzu model, Japan), whereas carapace width, the distance between the tips of the 9th anterolateral spine of the crab carapace [1,5] was determined using a six-inch liquid crystal display (LCD) digital Vernier caliper (accuracy: 0.01 cm; Kingsmart brand, Hong Kong). The crabs were then proceed with limb autotomy procedure, placed individually in a container, fed with chopped yellowstripe scad fish, Selaroides leptolepis, at 10% of their BW twice daily (at 0900 and 1700 h), and were maintained until completed molted.

Limb autotomy
The chelipeds (claws) and pereiopods (walking legs) were cast off, leaving only the pleopods (swimming legs) for the crabs' movement [14]. The autotomized crabs were placed individually in a container, with ambient salinity (28e32 ppt), maintained temperature (27e29 C), moderate aeration, dark light intensity (tanks were fully covered with black net, except for feeding activities), and 100% water exchange every two days. The crabs were fed with chopped scadfish, Selaroides spp., at 10% of their body weight twice daily (at 0900 and 1700 h) [1,2] for observation of the molting activity.
Every 15 day throughout the 60-day study period (Day 15, 30, 45 and 60), five crabs were randomly selected for dissection and evaluation of ovarian maturation stages through coloration, gonadosomatic  index, and ovaries were fixed in Davidson's solution for further histological assessment to determine the oocyte structures and diameter sizes [1,3,4].

Data analysis
The ovarian maturation stages were distinguished by the coloration of the ovary referred to the previous studies; where translucent to creamy white (Stage 1), yellowish (Stage 2), pale to dark orange (Stage 3), and dark orange to reddish orange (Stage 4) [4e7].
As for the gonadosomatic index, GSI, the calculation was as follows [2,4]: Gonadosomatic index ¼ Ovary Weight ðgÞ Body Weight ðgÞ x100 Meanwhile, for oocyte diameter size and structure analysis, we referred to Amin-Safwan et al. [1], where 100 oocytes for each sample (x-axis) were measured using the advanced microscope (Leica Microsystem, Wetzlar GmbH, DM LB 2, Germany). The final reading of the oocyte diameter size was averaged accordingly to respective salinity treatments.
The collected data were analyzed using Kruskal-Wallis test analysis through the SPSS software (Version 22.0 for Windows; Statistical Package for the Social Science Inc. Armonk, NY: IBM Corp.), available at https://www.ibm.com/products/spss-statistics.