Population dynamics and parasitation of planktonic and epibenthic crustaceans in the Baltic Schlei Fjord
1995; Elsevier BV; Volume: 42; Issue: 12 Linguagem: Inglês
10.1016/0967-0653(96)82409-4
ISSN1878-6731
Autores Tópico(s)Nematode management and characterization studies
ResumoThe planktonic and epibenthic crustacean fauna from two sites of the brackish Schlei fjord, Northern Germany, was invest igated over a six-month period. Calanoid and cyclopoid copepods were more abundan t in lower safinities, whereas benthic decapods, isopods and amphipods prevailed in the site of higher salinity. Cestodan larvae were found only in spring which may be due to the t iming of the respective fife-cycles. Parasites of benthic crustaceans, mostly d igenean metacercariae but also cestodans, acanthocephalans and nematodes, appeared from spring to late summer. Decreasing salinities caused lower intensities of the most abundan t parasite, Maritrema subdolum; only the true brackish-water species among the hosts were more heavily infested than those found in higher safinities. The correlation of parasite size and host size at infestation became apparent. Therefore, Crangon crangon is an optimal host for the large Podocotyle atomon metacercariae. Coevolutive trends be tween some hosts and parasites are made evident. I N T R O D U C T I O N C r u s t a c e a n s a re ve ry i m p o r t a n t l i nks in t he p e l a g i c as we l l as in t h e b e n t h i c food cha ins . Pa r t i cu l a r l y s m a l l e r s p e c i e s w h i c h a r e m o s t l y h e r b i v o r o u s a re t he m a i n p r e y for y o u n g or s m a l l s i z e d f i shes (Berg, 1979; Z a n d e r , 1979; S c h m i d t M o s e r & W e s t p h a l 1981; Z a n d e r & D6r ing , 1989: Z a n d e r & W e s t p h a l . 1992). Add i t i ona l ly , m a n y c r u s t a c e a n s p e c i e s t u r n e d ou t to b e ca r r i e r s of fish, b i rd a n d m a m m a l p a r a s i t e s w h i c h u s e th i s g r o u p as f irst or s e c o n d i n t e r m e d i a t e hos t s (Reimer , 1970). T h e r e f o r e . c r u s t a c e a n s c a n b e i m p o r t a n t t r a n s f e r o r g a n i s m s of h e l m i n t h s w i t h i n t h e l a t t e r ' s c o m p h c a t e d h f e c y c l e w h i c h o f t en i n v o l v e s h o s t a l t e r n a t i o n s ( O d e n i n g , 1974; Re imer , 1983). T h e r e is still, h o w e v e r , a l a ck of e c o l o g i c a l l i t e r a t u r e o n c r u s t a c e a n p a r a s i t e s ( M a c K e n z i e & G i b s o n , 1970; W e n d l and , 1985; L a u c k n e r 1992). T h e Bal t ic S e a is a b r a c k i s h s e a w i t h d e c r e a s i n g sa l in i t i e s f rom w e s t to eas t . W h e r e a s t he c e n t r a l Bal t ic p r e s e n t s a w i d e a r e a w i t h on ly 0 .8 -0 .6 % sa l im t i e s w h i c h m e a n s t h e a r e a of s p e c i e s m i n i m u m in t he s e n s e of R e m a n e (1958), s o m e f jords s u c h as t h e S c h l e i i n n o r t h e r n S c h l e s w i g H o l s t e i n ( G e r m a n y ) s h o w a c o n t i n u o u s d e c r e a s e (Ne l l en . 1967; S c h r i e v e r , 1974). A c c o r d i n g to t h e l a w of T h i e n e m a n n t1939], t h e n u m b e r of s p e c i e s ks Low in e x t r e m e h a b i t a t s , b u t t h a t of i n d i v i d u a I s is h i g h T h e q u e s t i o n is. t h e r e f o r e , w h e t h e r t he p o p u l a t i o n s of p a r a s i t e s b e h a v e i n t h e s a m e w a y as t h o s e of t h e i r hos ts . In o r d e r to so lve th i s p r o b l e m , t h e s t r u c t u r e a n d d y n a m i c s of c r u s t a c e a n p o p u l a t i o n s f rom t w o s i t e s w i t h d i f f e r e n t sa l in i t i e s a re c o m p a r e d : t h e o n e l v i n a in t h e a m e s o h a h n e zone , t h e o t h e r in t h e ~ m e s o h a l i n e z o n e w h i c h c o r r e s p o n d s to 9 Biologische Anstalt Helaoland. HamburcT 760 S. Gollasch & C. D. Zander the species minimum. Additionally, the invest igat ions follow the parasite communi ty concept of Esch et al. (1990), according to which the lowest level the inf racommuni ty is treated with respect to infestation intensit ies of crustacean parasites. INVESTIGATION SITE, MATERIAL AND METHODS The Schlei is a shallow, approx. 43-kin long fjord which flows into the Kiel Bight of the Baltic Sea (Fig. 1). The invest igat ion sites were Olpenitz, located near the mouth of the Schlei, and Missunde in the central Schlei (Fig. 1). Salinities as well as temperatures were measured during the invest igat ion t ime from April to September. Sahnities were be tween 12.8 and 14.5 %o in Olpenitz and 5.8 and 8.2 %0 in Missunde: the extreme values
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