Lepeophtheirus dissimulatus — Lewis 
197 
3 . 5 ] 
40 80 120 160 200 240 280 
Time in Hours 
FIG. 3. Greatest length of cephalothorax, including 
frontal plates, of developmental stages of L. dissimu- 
latus. co, Copepodite; ch, chalimus. 
DEVELOPMENT AND DESCRIPTION OF 
LIFE HISTORY STAGES 
As the eggs are extruded out of the oviducal 
opening at the posterior end of the genital seg- 
ment they are fertilized by sperm from the 
seminal receptacle (Wilson, 1905:526). Two 
spermatophores are implanted by the male on 
the external posterior ventral surface of the fe- 
male genital segment and open into the two 
oviducts through the seminal receptacles (Wil- 
son, 1905:527). The disk-shaped fertilized eggs 
are extruded as a uniseriate chain (Fig. 8 a). 
Each egg is wrapped in a cuticular material, 
presumably secreted by a cement gland in the 
genital segment of the female, that remains at- 
tached to the female until after the eggs hatch 
(Fig. 8£). The covering appears to serve as a 
protective structure for the eggs and developing 
embryos and as a means of connecting the eggs 
together in a string. 
Because of the flattening of the fertilized 
eggs, development is difficult to observe. From 
13-20 hr (at room temperature, approximately 
23 C) after extrusion, a reddish-colored eye 
spot becomes visible on the yellowish or whit- 
ish embryo. From 30 to 40 hr (at room tem- 
perature) after extrusion, movement is visible 
within the egg. As the movement of the em- 
bryo increases, the egg expands and finally rup- 
tures. Hatching occurs regularly, the distal egg 
hatching first, the proximal last. A lapse of be- 
tween 2 and 10 min occurs between the hatch- 
ing of one egg and the hatching of the succeed- 
ing one. In almost all cases, the egg chamber 
ruptures on the inner side of the egg string 
(i.e., the surface nearest the median longitudi- 
nal axis of the female). The first nauplius, by 
sporadic violent movements of its appendages, 
works its way out of the egg case and, after a 
short period of rest in which some swelling 
occurs, assumes the characteristic jerky, free- 
swimming habit of the naupliar stages. 
Body 
The externally unsegmented body of the first 
nauplius (Fig. 8c) is of a general obovoid shape 
in both dorsal and lateral aspects. The greatest 
length is slightly more than twice the greatest 
width, and the anterior end is broadly curved. 
The lateral margins of the posterior one-half 
of the body curve inward regularly to the ir- 
regularly-margined posterior end. The posterior 
end of the body has a slight median projection 
and two indentations, one on each side, from 
which the balancers arise. The balancers (Fig. 
16k) are unsegmented, slightly curved, rodlike 
structures that project laterally and have their 
distal end slightly flattened. 
The cuticle of the first nauplius is, in most 
specimens, slightly larger than the inner body; 
3.5 
3.0 
2.5 
I 20 
I 15 
1.0 
0.5 
* It 
d 9 
f <= 1 
40 
80 120 160 200 
Time in Hours 
240 280 
Fig. 4. Greatest width of body, excluding marginal 
flanges, of developmental stages of L. dissimulatus . 
n, Nauplius; co, copepodite; ch, chalimus. 
