scholarly journals Sexual dimorphism in mud crabs: a tale of three sympatric Scylla species

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e10936
Author(s):  
Hanafiah Fazhan ◽  
Khor Waiho ◽  
Yushinta Fujaya ◽  
Nita Rukminasari ◽  
Hongyu Ma ◽  
...  
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Discriminant Function ◽  
Discriminant Function Analysis ◽  
Function Analysis ◽  
Carapace Width ◽  
Sympatric Species ◽  
Sexually Dimorphic ◽  
Morphometric Characteristics ◽  
Mud Crabs

Sexual dimorphism is a common phenomenon in the animal kingdom. To test the consistency of sexual dimorphism patterns among sympatric species of the same genus, ten morphometric characteristics of mud crabs Scylla olivacea, S. tranquebarica and S. paramamosain were measured and compared using Discriminant Function Analysis (DFA). The descriptive analysis revealed that in all three species, body size dimensions and cheliped dimensions were significantly larger in males whereas the abdomen width was female-biased. Also, we described a morphological variation (carapace width, CW ≤ CW at spine 8, 8CW) that is unique to S. olivacea. Discriminant function analysis revealed that all nine morphometric characteristics were sexually dimorphic in S. olivacea, S. tranquebarica (except right cheliped’s merus length, ML) and S. paramamosain (except 8CW). The obtained discriminant functions based on the morphometric ratios (with CW as divisor) correctly classified 100% of adults of known sex of all three species. Further, based on the selected body traits, DFA was able to almost completely distinguish males (94%), but not females (74%), among the three Scylla species. This study highlights that congeneric species of portunids (e.g., Scylla spp.) show similar sexually dimorphic characteristics (body size and secondary sexual characteristics).

scholarly journals Morphological descriptions and morphometric discriminant function analysis reveal an additional four groups of Scylla spp

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8066 ◽  
Author(s):  
Hanafiah Fazhan ◽  
Khor Waiho ◽  
Emilia Quinitio ◽  
Juliana C. Baylon ◽  
Yushinta Fujaya ◽  
...  
Keyword(s):  
Discriminant Function ◽  
Discriminant Function Analysis ◽  
Function Analysis ◽  
Carapace Width ◽  
Morphological Characters ◽  
Equatorial Region ◽  
Natural Occurrence ◽  
Pure Species ◽  
Sulu Sea ◽  
Males And Females

There are four species of mud crabs within the genus Scylla, and most of them live sympatrically in the equatorial region. Apart from a report in Japan about the finding of a natural Scylla hybrid more than a decade ago after the division of genus Scylla into four species by Keenan, Davie & Mann (1998), no subsequent sighting was found. Thus, this study investigates the possible natural occurrence of potential hybridization among Scylla species in the wild. A total of 76,211 individuals from mud crab landing sites around the Malacca Straits, South China Sea and Sulu Sea were screened. In addition to the four-purebred species, four groups (SH 1, n = 2, 627; SH 2, n = 136; SH 3, n = 1; SH 4, n = 2) with intermediate characteristics were found, mostly at Sulu Sea. Discriminant Function Analysis revealed that all Scylla species, including SH 1 - 4, are distinguishable via their morphometric ratios. The most powerful discriminant ratios for each character and the top five discriminant ratios of males and females were suggested. The carapace width of SH 1 males and females were significantly smaller than pure species. Based on the discriminant ratios and the description of morphological characters, we hypothesize that the additional four groups of Scylla with intermediate characteristics could be presumed hybrids. Future work at the molecular level is urgently needed to validate this postulate.

scholarly journals Best parameters for sexual dimorphism in the facial thickness tissue with ultrasonic assessment

2008 ◽  
Vol 13 (2) ◽  
pp. 60 ◽  
Author(s):  
Iván Claudio Suazo Galdames ◽  
Guillermo Enrique Salgado Alarcón ◽  
Daniela Alejandra Zavando Matamala
Keyword(s):  
Sexual Dimorphism ◽  
Discriminant Function ◽  
Discriminant Function Analysis ◽  
Function Analysis ◽  
Tissue Thickness ◽  
Significance Level ◽  
Ultrasound Measurements ◽  
Males And Females ◽  
Ultrasonic Assessment ◽  
Best Parameters

<p>Knowledge of facial tissue thickness is crucial to facial reconstruction procedures in forensic sculpture. The literature still brings some controversy on the validity of data obtained for different population groups. The purpose of this study was to investigate sexual dimorphism in the thickness of the facial tissues. The study sample consisted of 43 volunteers, between 24 and 48 years of age, and of normal body mass. Ultrasound measurements of facial tissue thickness were obtained at 14 median and paramedian landmarks. A T test was used to compare measurements from males and females, with a significance level of at least 0.05. Discriminant function analysis was used to determine the points that showed most distinction between the sexes. Measurements at paramedian landmarks were greater in males, while those at median landmarks were greater in female subjects, except for Down’s A and B points. We conclude that sexual dimorphism in facial thickness justifies the pre-assignment of sex in reconstruction procedures in forensic sculpture</p>

scholarly journals Sexual dimorphism in black jaw tiliapia (Sarotherodon melanotheron) and banded jewelfish (Hemichromis fasciatus) from the Great Kwa River, Calabar, Nigeria

2017 ◽  
Vol 75 (4) ◽  
pp. 122-131
Author(s):  
Oju Richard Ibor ◽  
George Eni ◽  
Andem Bassey Andem ◽  
Akanimo Joseph ◽  
Azubuike Victor Chukwuka
Keyword(s):  
Sexual Dimorphism ◽  
Discriminant Function ◽  
Discriminant Function Analysis ◽  
Standard Length ◽  
Function Analysis ◽  
Gonad Weight ◽  
Pectoral Fin ◽  
Body Depth ◽  
Sarotherodon Melanotheron ◽  
Fin Length

AbstractIn this study, the pattern and magnitude of sexual dimorphic differences have been investigated in black jaw tilapia (Sarotherodon melanotheron) (n = 160; 74 males and 86 females) and banded jewelfish (Hemichromis fasciatus) (n = 120; 42 males and 78 females) from the Great Kwa River, Calabar, Nigeria. Fish samples were collected between July and December 2015. Fourteen morphometric variables, including body weight, total length, standard length, body depth, cheek depth, pre-orbital length, postorbital length, pectoral fin length (right and left), pelvic fin length (right and left), head length, gonad weight, eye diameter and four meristic variables, including number of pectoral fins (right and left) and number of pelvic fins (right and left), were taken using standard methods. Size-adjusted morphometric measurements subjected to step-wise discriminant function analysis were used to determine predictor variables to morphologically differentiate sexes for both species; magnitude of dimorphism between sexes was estimated using percentage classification accuracy of the discriminant function analysis. From the discriminant function analysis, the pectoral fin length and gonad weight positively contributed significantly to morphometric dimorphism (magnitude=69.2%) in male and femaleS. melanotheronsuggesting adaptation for reproductive function; while forH. fasciatusthe body depth and standard length were important contributors to sexual dimorphism (magnitude=84.2%) suggesting size dimorphism for aggressiveness, territorial behavior and improving swimming performance. Overall, our results indicate that the different magnitude of sexual dimorphism between the two species could be attributable to the type and functional role of sexual dimorphic traits.

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