THE EXPLOSION OF THE SPERMATOZOA OF THE CRAB LOPHOPANOPEUS BELLUS (STIMPSON) RATHBUN

¹ DEPARTMENT OF ZOÖLOGY, OREGON AGRICULTURAL COLLEGE, CORVALLIS, OREGON

1. The spermatozoa of the black-clawed crab, Lophopanopeus bellus (Stimpson) Rathbun, are minute, greenish cells, which appear like spheroids when seen from the top or bottom and like ellipsoids when seen from the side.

2. The structure of these spermatozoa is very similar to that of the edible crab, Cancer magister Dana. In the centre there is a tube-like central body, and surrounding this in order of sequence is a secondary vesicle, a primary vesicle and a nuclear cup with slender radiating arms.

3. There are four types of spermatozoa produced in Lophopanopeus bellus, depending on the number of radial arms which they contain. There are three-, four-, five- and six-rayed spermatozoa, with the four- and five-rayed types predominating in numbers.

4. In sea water and isotonic solutions of various salts, no change occurs in the normal appearance of the spermatozoa. In hypotonic solutions of these salts the spermatozoa explode by an eversion of the two vesicles and the central body.

5. In ovarian fluids some of the spermatozoa explode violently, with a rupture and disintegration of one or both vesicles.

6. Acidulated sea water has a harmful effect on the spermatozoa, either causing swelling or shrinkage, with subsequent disintegration.

7. A lowering of the osmotic pressure in the medium that surrounds the spermatozoa, undoubtedly brings about their explosion.