WING: ELLOBIOPSIDAE FROM NORTH PACIFIC 



number of infected hosts and the proportion of 

 hosts with more than one parasite were greatest 

 in the late summer, this may be an artifact of 

 sampling methods. Long-term sampling with 

 plankton nets at Auke Bay and Little Port 

 Walter has not captured parasitized mysids and 

 generally has not taken large numbers of mysids. 

 The light-baited trap is exceptionally effective in 

 capturing mysids but has been used only in 

 summer. Although no quantitative data are 

 available for the Auke Bay sample (AB65-108 — 

 Table 1), it contained several thousand mysids. 

 The two Little Port Walter collections con- 

 tained about 9,000 and 7,000 mysids respectively 

 (Table 3). 



Thalassomyces albatrossi n.sp. 



lAmallocystis fasciatus — Tattersall (1951), 



Boschma (1959). 

 Thalassomyces fasciatus — Collard (1966). 

 Thalassomyces n.sp. — Vader (1973b). 



Type location:^ Albatross stn. 4867, lat. 36° 

 31'N, long. 129°46'E; depth 150 fathoms; 1 

 August 1906. USNM 82439. 



Holotype: One slide with several gonomeres 

 and trophomeres separated and mounted whole. 

 Remainder left on the host. Host: Stilomysis 

 major Tattersall, female, 26 mm long; carapace 

 length, 7.9 mm. 



Paratype: Immature, bearing two tufts or stalks 

 of trophomeres, intact on host. Host: S. major, 

 female, from USNM 81268. 



Location: Albatross stn. 4862, lat. 36°20'N, 

 long. 129°50'E; depth 184 fathoms; 31 July 1906. 



Disposition of types: Holotype and paratype 

 deposited in Division of Crustacea, Smithsonian 



^The locale on the original collection labels is Cape Clonard, 

 Japan. Political changes since 1906 have resulted in name 

 changes, the area now being referable to near Yonghae, South 

 Korea. 



Institution, U.S. National Museum, Washington, 

 D.C., as Type USNM 24366 and USNM 24367. 



Specific Diagnosis 



The external portion of the parasite is visible 

 as one to four tufts of trophomeres located mid- 

 dorsally on the host's thorax. In the mature 

 parasite, each tuft contains up to 50 tropho- 

 meres, which arise by close dichotomous branch- 

 ing from the primary stalk. Trophomeres are 0.80 

 to 1.70 mm long. Each trophomere bears one to 

 four gonomeres, usually three. Mature distal 

 gonomeres are oval to elongate in shape — 0.4 

 to 0.7 mm long and 0.25 to 0.35 mm in diameter. 

 The length of the distal gonomere is 1.5 to 2.4 

 times the diameter. The penultimate and proxi- 

 mal gonomeres are usually shorter than the 

 distal gonomere but have about the same 

 diameter. 



[Diagnosis Propria: Pars parasiti externa 

 apparet unus ad quattuor racemi trophomerorum 

 medio dorso in animalis thorace positi. In ma- 

 turo parasito, unusquisque racemorum fert ad 

 quinquaginta trophomera, quae in duas partes 

 proximas ex stirpe principali dividuntur. Tropho- 

 mera sunt 0.80 ad 1.70 mm longa. Unumquidque 

 trophomerorum fert unum ad quattuor gonomera, 

 plerumque tria. Matura gonomera distalia sunt 

 conformatione ovata ad praelonga — 0.4 ad 0.7 mm 

 longa et 0.25 ad 0.35 mm per medium. Longitudo 

 gonomeri distalis est 1.5 ad 2.4 eius gonomeri 

 dimetientes. Gonomera paenultima et proximalia 

 sunt plerumque breviora quam gonomera distali, 

 sed sunt per medium fere eadem.] 



This species differs most clearly from other 

 closely related Thalassomyces {T. boschmai, T. 

 niezabitowskii , and T. nouveli) found on mysids 

 by having much longer terminal gonomeres 

 (which exceed 0.4 mm), a more elongate shape 

 of the gonomeres, and three or four tufts of 



Table 3. — Species and number of mysids and incidence of Thalassomyces boschmai in two 

 light-baited trap samples at Little Port Walter, 7-8 September 1966. 



175 



