FISHERY BULLETIN: VOL. 73, NO. 1 



RATIO 



05 06 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.H 2.5 



—I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 r— 



N = 15 n = 2 



N = 37 n = 10 



N = 120 n = 12 r 



N = 10 n = 1 



N = 70 n = 7 



N = 15 n = 1 



T. NOUVELI ON ANCHIALINA ACILIS (EM) 



T. BOSCHMAI ON LEPTOMYSIS GRACILIS (WM) 



T. BOSCHMAI ON NEOMYSIS KADIAKENSIS (SA) 



T. BOSCHMAI ON NEOMYSIS KADIAKENSIS (SA) 



T. BOSCHMAI ON NEOMYSIS KADIAKENSIS (W) 



T. BOSCHMAI ON ACANTHOMYSIS PSEUDOMACROPSIS (SA) 



T. NIEZABITOWSKII ON LEPTOMYSIS MECALOPS (EM) 

 T. ALBATROSSI ON STILOMYSIS MAJOR (K) 



0.95 CI OF X 

 RANGE . 



^^ 



15 



Figure 2. — Length-diameter ratios of Thalassomyces found on Mysidae from the eastern Mediterranean (EM), western 

 Mediterranean (WM), Washington (W), southeastern Alaska (SA), and Korea (K). The horizontal line represents the sample 

 range, the vertical line the sample mean; the black rectangle represents the 0.95 confidence limits of the mean, and the distance 

 from the mean line to the edge of the white rectangle represents 1 standard deviation; N = number of gonomeres measured 

 and n = number of parasites (the numbers are unknown for T. nouveli and T. niezabitowskii). 



the external portions of the parasite could hardly 

 be retained during a molt. The control over molt- 

 ing could be by starvation as postulated by 

 Wickstead (1963) or by disturbance of the host's 

 neuroendocrine system as postulated by Hoffman 

 and Yancey (1966). The close association of other 

 Thalassomyces v^ith the nervous system (Boschma 

 1959; Kane 1964; Collard 1966) or the gonadal 

 areas (Einarsson 1945; Boschma 1959) suggests 

 some hormonal control over growth, molting, and 

 maturation of the host. 



The behavior of the parasitized mysids is not 

 noticeably affected. The swimming speed and 

 maneuverability of parasitized and nonparasi- 

 tized mysids appear to be the same; flexing and 

 twisting of the ellobiopsids as they are dragged 

 through the water apparently do not affect the 

 host. 



Hosts of r. boschtnai 



This species has been recorded as a parasite 

 of L. gracilis and Gastrosaccus lobatus (Nouvel) 

 in the Mediterranean Sea (Nouvel 1954; Hoenig- 



man 1954, 1960, 1963; Nouvel and Hoenigman 

 1955). Five mysids are known as hosts of T. 

 boschmai in the eastern North Pacific. In Puget 

 Sound, Acanthomysis macropsis (Tattersall), 

 A. nephrophthalma Banner, and N. kadiakensis 

 are hosts (Thorne 1968). In Alaska, A. pseudo- 

 macropsis (Wing 1965, Hoffman and Yancey 

 1966), N. kadiakensis (Wing 1965), and Metery- 

 throps robusta S. I. Smith have been observed 

 parasitized by T. boschmai. Meterythrops robusta 

 is a new host record. 



Seasonal Occurrence 



Thorne (1968) reported a seasonal pattern of 

 incidence of infection by mysids (the percentage 

 oiN. kadiakensis with ellobiopsids) by T. boschmai 

 at Port Orchard, Puget Sound, Wash. The inci- 

 dence of infection at Port Orchard was low in the 

 winter and spring (1 to 8% of adults, 1 to 21.5% 

 of immatures) and rose in the late summer to a 

 maximum in October (17% of adults, 35% of 

 immatures). A seasonal pattern of infestation is 

 not clear in the Alaska material. Although the 



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