On Thu, 5 Oct 2000, Kevin Hume wrote:

> Colleagues of mine at Queen's University Belfast are doing behavioural
> studies on the "glass prawn", Palaemon elegans (Decapoda: Palaemonidae).
> However, there are some questions as to how one distinguishes between the
> sexes in this group.  The females are generally much larger than the males
> -- but is there a more objective method for those cases when size
> differences are not so clear cut?  Any suggestions would be most welcome,

>From the most obvious to least obvious...

1. Eggs on the underside of the abdomen.

2. Ovary (often seen through the transparent carapace, dorsal
medial). Color varies according to species, but ovary will increase in
size prior to molting and is similar in color as new eggs.

3. First and second pleopods (abdominal appendages) NOT modified for
"sperm transfer". Most simply, the second pleopod bears an appendix
masculina in MALES, but not FEMALES. You need a dissecing microscope to
see it in small species.

4. Females bear gonopores on or near the base of the third walking legs,
while males bear gonopores an the base of the last (fifth) walking
legs. These are difficult to see, even for experts.

I suggest you see a decent invert book or crustacean
reference. For appendix masculina try:

Bauer, R. T. 1976. Mating behavior and spermatophore
transfer in the shrimp Heptacarpus pictus
(Stimpson) (Decapoda: Caridea: Hippolytidae). J. Nat. Hist. 10 : 415-440.

or

Berg, A. B. V., and P. A. Sandifer. 1984. Mating behavior of the grass
shrimp Palaemonetes pugio Holthuis (Decapoda,
Caridea). J. Crust. Biol. 4(3) : 417-424.

Good luck!

-Curt
 

G. Curt Fiedler, PhD!
Zoology Department & Hawaii Institute of Marine Biology
University of Hawaii at Manoa
2538 The Mall, Edmondson hall
Honolulu, Hawaii  96822
Phone:  (808)956-4712
Fax: (808)956-9812

http://www2.hawaii.edu/~zoology/graduate/CurtPage.html