Ellobiopsidae of Alaskan Coastal Waters — Hoffman and Yancey 
71 
Species of Thalassomyces (formerly known as 
Amallocystis ) are different in many respects 
from those of Ellobiopsis. Each Thalassomyces 
consists of a tuft of trophomeres extending from 
a central stalk, whereas each Ellobiopsis has only 
one trophomere. The number of trophomeres 
extending from the stalk is used as a species- 
differentiating character in Thalassomyces. 
The gonomere (or gonomeres) which forms 
on the distal end of the trophomere is separated 
by a septum from the trophomere. Individuals 
of Ellobiopsis species have one or two gono- 
meres. If more than one gonomere is present, as 
in the Thalassomyces species and some Ello- 
biopsis species, each is separated from the next 
by a septum. Sporulation has not been described 
for any Thalassomyces species but is assumed to 
occur. Old individuals of Thalassomyces spp. 
may be found with numerous empty gonomeres; 
some with collapsed walls may remain attached 
to the trophomere. 
Various euphausids, mysids, and carideans 
have been reported as hosts for Thalassomyces 
species. The ellobiopsid may be attached ven- 
trally to the host’s abdomen, as in T. racemosus, 
to the dorsal surface of the carapace, as in T. 
fagei and Thalassomyces sp., or at the base of the 
rostrum, as in T. capillosus (Boschma, 1956). 
As a result of this study the ranges for three 
species of ellobiopsids have been extended to 
Alaskan waters. They are T. fagei, T. capillosus, 
and E. chattoni. T. capillosus is the only species 
of the three previously recorded in the north 
Pacific Ocean. The development of T. fagei is 
described, and seasonal distribution of this spe- 
cies is discussed. Metridia longa was found to be 
a host for E. chattoni . 
OBSERVATIONS AND DISCUSSION 
Thalassomyces fagei 
The genus was named Amallocystis until 
1959, when Boschma pointed out that, because 
of its priority, Thalassomyces is the valid name. 
The euphausid Thysanoessa raschii (M. Sars) 
has been recorded as host for this ellobiopsid on 
two previous occasions. Einarsson (1945) de- 
scribed Amallocystis sp. parasitic on T. raschii 
taken in May in Faxafloi to the west of Iceland. 
Boschma (1949) established that the Amallo- 
cystis sp. of Einarsson was A. fagei (Boschma), 
and later (1959) he corrected the generic name 
to Thalassomyces. Glover (1952) observed two 
specimens of this euphausid infected with T. 
fagei . One was taken in July and the second in 
August of 1948 in the region of May Island in 
the Firth of Forth. Initially T. fagei (Boschma) 
was described as an Antarctic species, but its 
distribution has been extended to include the 
northern Atlantic waters by reports of Einarsson 
(1945), Glover (1952), and Macdonald (1927). 
Macdonald reported the occurrence of Staph- 
locystis racemosus on the euphausid Meganyc- 
tiphanes norvegica taken in the Clyde Sea. 
Boschma (1949) believes that this ellobiopsid 
was T. fagei and not S. racemosus. 
In our investigation we also found T. fagei 
parasitic on Thysanoessa raschii. The specimens 
were taken during the spring of 1963 in three 
small inlets which are part of Kachemak Bay, 
Alaska (59°27'N, 151°33'W). The samples 
were taken in 20-minute oblique hauls of a l /2-m 
plankton net with a standard No. 2 mesh. The 
depth in the area did not exceed 53 fathoms. 
This is the first record of this species of ello- 
biopsid from the Pacific Ocean, and its range is 
thus extended from the Atlantic to the north- 
eastern Pacific. 
The ellobiopsid parasites are attached to the 
host by a stalk which extends through the dorsal 
side of the carapace and penetrates the tissues 
below. The parasite is located in a dorsal con- 
cavity on the carapace of the host which is not 
found in uninfected euphausids (Fig. 1). An 
infected T. raschii usually bears only one Thalas- 
somyces, although up to four were observed. A 
specimen bearing two parasites is shown in 
Figure 2. 
The mature parasite has 30-50 trophomeres 
which are ramifications of the single central 
stalk. The trophomeres are expanded distally 
into a club shape. Trophomeres with one to six 
gonomeres were observed, although more com- 
monly three to five occur. The gonomeres are 
spherical to slightly elliptical in shape. Figures 
3 and 4/ are a photograph and a camera lucida 
drawing respectively of a mature parasite. In 
older individuals some of the distal gonomeres 
are empty. The gonomere remnant may break 
