Ellobiopsidae of Alaskan Coastal Waters— Hoffman and Yancey 
73 
Whether reproduction is sexual or asexual is 
unknown. These observations agree with the hy- 
pothesis accepted by Boschma (1949) for T. 
fagei concerning the assumed release of spores 
from the gonomere. jepps (1937) described 
spo.tula.tion in the distal structure which she 
termed the gonomere of Ellobiopsis chattoni. 
Hovasse (1951) observed sporulation of E. 
fagei. No observations of sporulation in a Thal- 
assomyces species are available. 
The external development of T. fagei is initi- 
ated by a small knob-shaped structure appear- 
ing through the middorsal region of the carapace 
of the host. This single knob bifurcates slightly, 
producing a bilateral structure (Fig. 4a) . The 
next stage appears to be the result of simul- 
taneous bifurcation of each of the previously 
formed lobes, resulting in a four-lobed struc- 
ture ( Fig. 4c ) . Further development of T. fagei 
is accomplished by repeated simultaneous dicho- 
tomous branching of each of the existing lobes. 
The simultaneous nature of the bifurcation is 
retained until the fifth or sixth division at which 
time the branching appears to get out of phase. 
In this study 77 specimens of T. fagei were 
examined. These were taken in plankton samples 
from three stations located in the Cook Inlet 
area of Alaska. The locations of the stations were 
as follows: at the mouth of Kasitsna Bay (59° 
28.7'N, 151°33 / W) and two stations in Tutka 
Bay (59°26.5 / N, 151°227 / W, and 59°25.5'N, 
151°19.5'W). 
The seasonal distribution of T. fagei was 
found to coincide in part with that reported for 
the same species parasitic on Thysanoessa iner- 
mis by Einarsson (1945). He found Thalas- 
somyce s' fagei (as Amallocystis sp.) on mature 
euphausids during May only. In our work dur- 
ing February and March of 1963 numerous 
Thysanoessa raschii were observed, but most of 
the individuals taken during this time were 
juveniles. Early stages of Thalassomyces fagei 
first appeared on the host early in April, 1963. 
Mature ellobiopsids were taken from late April 
until about the first of June. The external struc- 
tures of T. fagei were not present on the euphau- 
sids taken in February or March, nor were they 
present late in June. During May, 1963 we noted 
13% average infection of Thysanoessa raschii 
by Thalassomyces fagei. This was based on three 
samples containing 239 specimens of Thysano- 
essa raschii, of which 33 were parasitized. 
It appears unlikely, at least from the preserved 
material, that a mature Thalassomyces fagei 
could pass through the hole in the carapace of 
the host at molting. This is due to the fact that 
the host’s exoskeleton closely surrounds the stalk 
of the ellobiopsid. Since euphausids have a high 
intrinsic rate of molting, one can assume either 
that the euphausids continue to molt with their 
Fig. 3. Euphausid with a mature parasite. 
