North American Harpacticoid Copepods, 8 
The Danielssenia sibirica Group, with Description of 
D. stefanssoni Willey from Alaska 
Mildred Stratton Wilson 1 
Willey’s report (1920) on marine copepods 
of northern and northwestern coastal waters of 
North America included 12 species of Har- 
pacticoida, mostly from Canadian inshore local- 
ities. Among these was a new species, Daniels- 
senia stefanssoni , of particular interest because 
of its relationship to D. sibirica Sars from the 
northeastern Siberian coast Lang (1944, 1948) 
divided the six species of the genus into two 
groups. One, called the sibirica group, includes 
only these two related species occurring in 
closely situated regions of neighboring conti- 
nents. The present paper extends the known 
distribution of stefanssoni to the Chukchi Sea 
coast of Alaska, placing it not far distant from 
the nearest Asian occurrence of sibirica on 
Wrangell Island. Considering the scant knowl- 
edge of harpacticoid copepods of these two 
continental regions, it is not certain that the 
geographic separation is real, although it may 
be since such allopatry is suggested by other 
species-pairs and groups of freshwater, brackish- 
water, and marine copepods. 
The possible existence of a species-pair on 
the two continents is of considerable zoogeo- 
graphic interest and phylogenetic importance. 
Accurate determinations of the two species and 
of possible unknown species, recognition of 
variations, and phylogeny of the group and 
genus require detailed anatomical knowledge 
of D. stefanssoni . For these reasons, I have 
prepared this account of Alaskan specimens. A 
synopsis of literature, distribution, and com- 
ments on anatomy of D . sibirica, necessary for 
critical comparison with stefanssoni, are in- 
cluded. 
1 Arctic Health Research Center, U. S. Public 
Health Service, Anchorage, Alaska and Smithsonian 
Institution. Manuscript received August 9, 1965. 
Family tachidiidae 
Genus Danielssenia Boeck, 1872 
typica group (emendation of Lang, 1948) : 
D. typica Boeck, D. fusiformis (Brady) 
sibirica group (after Lang, 1948) : 
D. sibirica Sars, D. stefanssoni Willey 
unassigned species (emendatiton of Lang, 
1948): 
D. robusta Sars, D. perezi Monard 
comments on literature: Lang assigned 
four of the six species of the genus to the 
typica group, of which only D. typica and D. 
fusiformis are known from both sexes. Since the 
modification of leg 2 of the male is an im- 
portant character defining the two groups, the 
other two species ( robusta , perezi ) cannot be 
placed in any group at present, their relation- 
ship to all other species and to one another 
being considered indefinite. Even though they 
conform to the typica group in the number of 
setae on certain segments of the antennal 
exopod and of leg 4, they differ strikingly in 
forms of female leg 5 and in comparative 
lengths of endopod to exopod of legs 2-4. Al- 
though it may at times be true, it should not be 
considered incontrovertible that the number of 
setae of any given appendage is always a 
measure of degree of relationship of species in 
the Harpacticoida. An example of an undoubted 
species-pair that seemingly occurs allopatrically 
on the Eurasian and North American continents 
is that of Bryocamptus cuspidatus and B. tik- 
chikensis. The latter, described from Alaska 
(Wilson, 1958) and since found in Greenland 
(R0en, 1962), differs principally from the 
Eurasian cuspidatus in having 1 instead of 2 
inner setae on exopod segment 3 of leg 3. 
The form of female leg 5 of the D. sibirica 
435 
