WING: ELLOBIOPSIDAE FROM NORTH PACIFIC 



4. Primary stalks widely spaced when more 



than one per host. Mature gonomere 

 length-diameter ratio 0.7-1.9 (mean 



about 1.2) (5) 



Primary stalks closely spaced when more 

 than one per host. Mature gonomere 

 length-diameter ratio 1.5-2.4 (mean 

 about 2) T. albatrossi n.sp. 



5. Mature terminal gonomere shape ellip- 



soid, with the distal end the same size 



as the proximal end, to spherical 



T. boschmai (Nouvel) 



Mature terminal gonomere shape ovoid, 

 with the distal end smaller than the 



proximal end, to spherical 



T. niezabitowskii (Hoenigman) 



ELLOBIOPSIDS OF 

 NORTH PACIFIC MYSIDS 



Thalassomyces boschmai (Nouvel 1954) 



Thalassomyces sp. — Wing (1965), Hoffman and 



Yancey (1966), Thorne (1968). 

 Thalassomyces boschmai — Gait and Whisler 



(1970), Vader (1973b). 



Ellobiopsids of the genus Thalassomyces have 

 been observed on Mysidae from Alaska (Wing 

 1965; Hoffman and Yancey 1966); from Puget 

 Sound (Thorne 1968); and from southern British 

 Columbia (J. Gait, Friday Harbor Laboratory, 

 University of Washington, Friday Harbor, WA 

 98250, pers. commun.). New collections of Alaska 

 mysids (Table 1) plus supplementary material 

 from Puget Sound enabled me to identify these 

 ellobiopsids as T. boschmai. 



Characteristics of T. boschmai 



The identification of Thalasso?nyces spp. para- 

 sitizing mysids is based on external portions so 

 variable that for definitive identifications, several 

 characters must be examined. The external 

 characters used to identify a species are the total 

 size or height of the parasite, length of tropho- 

 meres, number of trophomeres per primary stalk, 

 number of gonomeres per trophomere, and size 

 and shape of gonomeres. The number of primary 

 stalks and the site of attachment are also useful 

 characteristics. Differences between specimens 

 from different localities may be associated with 



'Taken in light-baited trap; lat. 56°23'N, long. 134°39'W: 7-8 September 

 1966. 



^Taken in light-baited trap; lat. 58°2rN, long. 134°40'W; 24 June 1964. 



^Taken in Isaacs-Kidd mid-water trawl; lat. 57'10'N, long. 135°21'W; 

 21 April 1967. 



"Collection of Hoffman and Yancey (1966); lat 59°27'N, long. 151° 

 33W; October, December 1963 and February 1964. No collection number 

 because material was lost. 



local races and may to some extent be pheno- 

 typically associated with the host species. 



The height of the North Pacific T. boschmai 

 ranges from 0.75 to 1.70 mm; most of the speci- 

 mens are between 1.30 and 1.50 mm. The maxi- 

 mum height is larger than the 1.25 mm given 

 by Hoenigman (1954) for T. boschmai found on 

 Leptomysis gracilis G. O. Sars, but in the Pacific, 

 host mysids are much longer than the Mediter- 

 ranean Leptomysis (13 mm). Neomysis kadia- 

 kensis Ortman are often over 20 mm long. 

 Boschma (1959) noted a positive relationship 

 between the size of the host and the size of the 

 parasite T. fagei (Boschma) on euphausiids. 



Mature trophomeres constitute most of the 

 external mass of an ellobiopsid parasite. Within 

 a parasite, the lengths of the trophomeres 

 appear uniform, but they vary greatly between 

 parasites. Lengths of trophomeres from 18 para- 

 sites found on Acanthomysis pseudomacropsis 

 (Tattersall) and A'^. kadiakensis were from 0.72 

 to 1.32 mm. Because gonomeres are lost during 

 sporulation, old trophomeres are generally 0.3 to 

 0.7 mm shorter than those that still have three 

 or four gonomeres. 



The number of trophomeres per primary stalk 

 depends on the state of development and the 

 condition of preservation. Dichotomous branch- 

 ing close to the point where the trophomeres 



171 



