Ellobiopsidae of Alaskan Coastal Waters 
Ethelwyn G. Hoffman and Robert M. Yancey 1 
ABSTRACT: Four species of ellobiopsids were taken in Alaskan coastal waters. 
Thaiassomyces fagei (a synonym of Amallocystis fagei ) was found to parasitize 
specimens of the euphausid Thysanoessa raschii taken in Kachemak Bay, Alaska. 
The development of T. fagei external to the host from a small knob to the mature 
form was found to occur by repeated dichotomous branching. T. fagei occurred dur- 
ing April and May but was not observed at other times of the year. Thaiassomyces 
sp. was found to be parasitic on specimens of the mysid Acanthomysis pseudoma- 
cropsis taken in Kachemak Bay, Alaska. The range of Thaiassomyces capillosus, para- 
sitic on the caridean Pasiphaea pacifca, is extended from Coos Bay, Oregon, to Orca 
Bay, Prince William Sound, Alaska. Ellobiopsis chattoni was found to parasitize 
the copepod Metridia longa, a new host of this ellobiopsid. Specimens of E. chattoni 
were taken in the waters of southeastern Alaska, extending the range of E. chattoni 
from the Atlantic to the north Pacific. 
The systematic position of the family Ello- 
biopsidae Coutiere and the genera therein has 
been an enigma since their original description. 
According to Margaret Jepps (1937), T. Scott 
in 1897 first described the ellobiopsid now 
known as Ellobiopsis chattoni as a "? infusorian 
parasite” of the copepod Calanus fnmarchicus. 
She states also that in 1910 Caullery associated 
the ellobiopsids with the Dinoflagellata. Various 
authors have continued to consider these or- 
ganisms to be closely related to the dinoflagel- 
lates. Jepps points out that a relation with the 
fungi is possible. Boschma ( 1949, 1956, and 
1959) reviewed the entire group and preferred 
to consider them as "Protista of uncertain posi- 
tion.” He noted that the ellobiopsids have af- 
finities with the following groups: parasitic 
peridinians, flagellates, and possibly fungi of the 
family Saprolegniaceae, and that the group is 
made up of a number of heterogeneous elements. 
The family Ellobiopsidae is a rather hetero- 
geneous group consisting of several genera. 
Members of the genus Ellobiocystis are epi- 
bionts, whereas members of the genera Ellobi- 
opsis and Thaiassomyces are parasites. This study 
is concerned only with the last two genera. 
1 U. S. Bureau of Commercial Fisheries Biological 
Laboratory, Auke Bay, Alaska. Manuscript received 
August 20, 1964. 
Various pelagic crustaceans, including copepods, 
euphausids, and carideans, are hosts of species of 
Ellobiopsis and Thaiassomyces. 
Organisms of the genus Ellobiopsis parasitize 
several species of copepods. Various species of 
Calanus have been reported by Marshall et al. 
(1934), Marshall and Orr (1955), and Jepps 
(1937) to be parasitized by Ellobiopsis chattoni. 
Pseudocalanus (Marshall, 1949), Clausocalanus 
(Hovasse, 1951), Acartia (Boschma, 1956), and 
Metridia, in this work, have also been found as 
hosts of E. chattoni. 
Jepps (1937) described very early forms of 
this parasite which she found on the antennae 
and mouth parts of Calanus fnmarchicus. These 
first appeared as small knobs on the setae of the 
mouth parts. At maturity E. chattoni consists of 
a pear-shaped part, the trophomere, which is 
attached by a stalk to the host’s appendage. Dis- 
tal to the trophomere there may develop one or 
two rounded segments, the gonomeres, in which 
sporulation takes place. According to Jepp’s de- 
scription of sporulation in E. chattoni , small 
buds arise on the free surface of the gonomere, 
each of which undergoes a series of fissions, 
forming spores. The mechanism of spore release 
and the relation between free spores and the oc- 
currence of small knobs on the host appendages 
is unknown. 
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