Post by xki11x on Sept 25, 2009 10:41:30 GMT 11
How to determine the sexes in scorpions
(Sexual dimorphism)
Scorpions are not easy to tell its sex. Short of dissecting your scorpion to look for the primary sexual characteristics or wait till one give birth (to show it's a pregnant female), it is rather difficult for most to tell which is which. Other than 'The Biology of Scorpion' by Gary A. Polis (Stanford University Press, 1990), sexual dimorphism of scorpion is shrouded in mystery. I have through mainly the abovestated book, Scorpion's Enthusiast page by Dr Stockwell and other books/internet resources compiled, interpreted (correctly or otherwise) and simplified as far as possible the probable secondary sexual characteristics of scorpions. It must be acknowledged that many exceptions exist.
As understanding of basic morphology is recommended, please go through briefly the anatomy section of the page before reading further.
Secondary sexual dimorphism:
On chelae of pedipalp
Heavier crenulation (roughness) on the cutting edge of male scorpion
Possible depression on the manus in male during mating season. Postulated to be used for holding the female chelae during the mating 'dance'
Thicker and more prominent ridge like carina in male
Pedipalp is longer and narrower than female in Heterometrus sp.
Pedipalp is shorter and wider in male of some Tityus sp, Scorpio maurus and some Buthus sp
Size:
Adult female is relatively longer in carapace length than male. (due to difference in age, the relative difference have no basis of comparision except in a population pool). Reveres is true in Tityus trinitatus, Liocheles australasiae and a few other species.
The ratio between the length of the carapace and sternite VII is lower in the female. ie the female is also wider.
Metasoma/telson:
Adult male generally has a greater metasoma:carapace length ratio. This is due to the two phase growth of metasoma (faster growth in adult phase) of most males. For female, the growth of metasoma is almost linear. Especially pronounced in Ischnuridae (eg. Hadogenes sp.)
Telson is generally larger and more round in female. exceptions include Euscorpius sp and Anuroctonus sp
Pectens:
Most commonly used reference.
Pectens longer in male. However direct measure is not very helpful as pecten length grows with age and differs with species.
--------------------------------------
** From Dr Stockwell's Scorpion Enthusiast page, the pecten tip of male goes beyond the distal end of coxa IV while the tip of female do not reach the distal end of coxa IV.
---------------------------------------
Pectinal teeth is shorter and straighter in female.
The male generally has more pectinal teeth (in Stockwell's picture using Pandinus imperator, the female has 14 teeth while the male has 15)
Female pectens forms an obtuse angle at the basal piece while that of the male is more perpendicular. (smaller angle)
Highly illustrative pictures of female (left) and male (right) specimens of Urodacus armatus kindly provided for use by Harry Wilson.
Notice:
1) Longer pectines of the male
2) More number of pectinal teeth in the male
3) Shorter pectinal teeth of female
4) wider mesosoma width of female
5) slight difference in shape of genital operculum (rhomboidal for female and triangular for male)
6) distal tip of pectines extends beyond coxa IV for male.
7) The pedipalp of the male is apparently slightly larger though it is not completely visible.
As for the more obtuse angle of the male, it is against the convention (supposedly female angle > male) which from what I see is not surprising as in both antemortem and postmortem, the position can be highly varied and unreliable as a gauge.
It must be noted that not all scorpion species shows such marked sexual dimorphism. Many are very much more subtle
Genital operculum:
The male may have a pair of genital papillae protruding from the posterior margin of the genital operculum.
The genital operculum of male may be partially fused or completely separate. In females, it is usually completed fused.
Click here to link to Dr Stockwell's FAQ on sex. It contains pictures which explains things clearer. I'll add my own soon.
Some common misconceptions related to scorpion sex
1) The scorpions mate using their tails.
Fact: Scorpions do not literally have copulation as we commonly perceived. There is no direct contact between the primary sexual organ which is covered by the genital operculum. For more about how scorpions mate refer to mating. The telson however may be used by some species like male Hadogenes sp to sting the female to 'calm' her.
2) The scorpion defecate from the below .......<ventral abdomen region (sternites)>
Fact: Two mistakes are committed here. One scorpions do not really defecate as they do not take in solid food. The more correct term should therefore be excrete (like in our urine). Secondly, scorpions excrete not from anywhere but the anus which is at the distal joint of metasomal V (between metasoma and the telson). Flipping misconception 1 and 2 give the right answer.......
3) Female scorpions show the 'white stuff' between the two hard carapace of the abdomen
Fact: That white stuff is the pleural membrane which connects the tergite and the sternite. Pregnant scorpion especially those in late gestation period shows very much of the pleural membrane due to the stretching. However, overfed scorpions, regardless of sex, also show much of the pleural membrane. On the other hand, starving non-pregnant female may show little or no pleural membrane. This really ain't much help in differentiating the sexes.
4) Males are bigger.
Fact: Most males of most species are in fact shorter and narrower than females. However, many exceptions exist and in some species, the male are indeed bigger while a few others, there's no significant difference.
(Sexual dimorphism)
Scorpions are not easy to tell its sex. Short of dissecting your scorpion to look for the primary sexual characteristics or wait till one give birth (to show it's a pregnant female), it is rather difficult for most to tell which is which. Other than 'The Biology of Scorpion' by Gary A. Polis (Stanford University Press, 1990), sexual dimorphism of scorpion is shrouded in mystery. I have through mainly the abovestated book, Scorpion's Enthusiast page by Dr Stockwell and other books/internet resources compiled, interpreted (correctly or otherwise) and simplified as far as possible the probable secondary sexual characteristics of scorpions. It must be acknowledged that many exceptions exist.
As understanding of basic morphology is recommended, please go through briefly the anatomy section of the page before reading further.
Secondary sexual dimorphism:
On chelae of pedipalp
Heavier crenulation (roughness) on the cutting edge of male scorpion
Possible depression on the manus in male during mating season. Postulated to be used for holding the female chelae during the mating 'dance'
Thicker and more prominent ridge like carina in male
Pedipalp is longer and narrower than female in Heterometrus sp.
Pedipalp is shorter and wider in male of some Tityus sp, Scorpio maurus and some Buthus sp
Size:
Adult female is relatively longer in carapace length than male. (due to difference in age, the relative difference have no basis of comparision except in a population pool). Reveres is true in Tityus trinitatus, Liocheles australasiae and a few other species.
The ratio between the length of the carapace and sternite VII is lower in the female. ie the female is also wider.
Metasoma/telson:
Adult male generally has a greater metasoma:carapace length ratio. This is due to the two phase growth of metasoma (faster growth in adult phase) of most males. For female, the growth of metasoma is almost linear. Especially pronounced in Ischnuridae (eg. Hadogenes sp.)
Telson is generally larger and more round in female. exceptions include Euscorpius sp and Anuroctonus sp
Pectens:
Most commonly used reference.
Pectens longer in male. However direct measure is not very helpful as pecten length grows with age and differs with species.
--------------------------------------
** From Dr Stockwell's Scorpion Enthusiast page, the pecten tip of male goes beyond the distal end of coxa IV while the tip of female do not reach the distal end of coxa IV.
---------------------------------------
Pectinal teeth is shorter and straighter in female.
The male generally has more pectinal teeth (in Stockwell's picture using Pandinus imperator, the female has 14 teeth while the male has 15)
Female pectens forms an obtuse angle at the basal piece while that of the male is more perpendicular. (smaller angle)
Highly illustrative pictures of female (left) and male (right) specimens of Urodacus armatus kindly provided for use by Harry Wilson.
Notice:
1) Longer pectines of the male
2) More number of pectinal teeth in the male
3) Shorter pectinal teeth of female
4) wider mesosoma width of female
5) slight difference in shape of genital operculum (rhomboidal for female and triangular for male)
6) distal tip of pectines extends beyond coxa IV for male.
7) The pedipalp of the male is apparently slightly larger though it is not completely visible.
As for the more obtuse angle of the male, it is against the convention (supposedly female angle > male) which from what I see is not surprising as in both antemortem and postmortem, the position can be highly varied and unreliable as a gauge.
It must be noted that not all scorpion species shows such marked sexual dimorphism. Many are very much more subtle
Genital operculum:
The male may have a pair of genital papillae protruding from the posterior margin of the genital operculum.
The genital operculum of male may be partially fused or completely separate. In females, it is usually completed fused.
Click here to link to Dr Stockwell's FAQ on sex. It contains pictures which explains things clearer. I'll add my own soon.
Some common misconceptions related to scorpion sex
1) The scorpions mate using their tails.
Fact: Scorpions do not literally have copulation as we commonly perceived. There is no direct contact between the primary sexual organ which is covered by the genital operculum. For more about how scorpions mate refer to mating. The telson however may be used by some species like male Hadogenes sp to sting the female to 'calm' her.
2) The scorpion defecate from the below .......<ventral abdomen region (sternites)>
Fact: Two mistakes are committed here. One scorpions do not really defecate as they do not take in solid food. The more correct term should therefore be excrete (like in our urine). Secondly, scorpions excrete not from anywhere but the anus which is at the distal joint of metasomal V (between metasoma and the telson). Flipping misconception 1 and 2 give the right answer.......
3) Female scorpions show the 'white stuff' between the two hard carapace of the abdomen
Fact: That white stuff is the pleural membrane which connects the tergite and the sternite. Pregnant scorpion especially those in late gestation period shows very much of the pleural membrane due to the stretching. However, overfed scorpions, regardless of sex, also show much of the pleural membrane. On the other hand, starving non-pregnant female may show little or no pleural membrane. This really ain't much help in differentiating the sexes.
4) Males are bigger.
Fact: Most males of most species are in fact shorter and narrower than females. However, many exceptions exist and in some species, the male are indeed bigger while a few others, there's no significant difference.
