Vztah imunokompetence jelce tlouště (Leuciscus cephalus) a parazitace mnohobuněčnými cizopasníky

Bc. Karolína Lamková, Ph.D.

Master's thesis

Abstract:

V roce 2004 2005 byl uskutečněný výzkum parazitofauny jelce tlouště ve vztahu k sezónním změnám imunokompetence (2004) a analýza vztahu imunokompetence a reprodukce v podmínkách různé investice hostitele do reprodukční funkce (2005). Celkem bylo na vybrané lokalitě vyšetřeno 183 jedinců. 1) V první části, ve které jsme se zaměřili na studium sezónních změn vybraných imunologických a fyziologických parametrů ve vztahu k parazitizmu byly potvrzeny statisticky významné rozdíly při porovnání parametrů imunokompetence, parazitické diverzity a abundance některých skupin mnohobuněčných cizopasníků. 2) Při porovnání parazitace v podmínkách různé investice hostitele do reprodukční funkce (období prereprodukční, reprodukční a postreprodukční) byly potvrzeny rozdíly při měření imunitních parametrů. Některé z nich je možno vysvětlit na principu alokace energie (teorie kompromisů) a to především negativní vztah: hmotnosti sleziny a kondičního faktoru, gonado-somatického faktoru a hmotnosti sleziny (prereprodukční fáze), hmotnosti sleziny a kondičního faktoru, kondičního faktoru a gonado-somatického indexu (postreprodukční fáze). Dále byly zjištěny statisticky významné vztahy při porovnání imunitních parametrů, parazitické diverzity a abundance některých skupin mnohobuněčných cizopasníků. 3) V samostatné kapitole této práce jsme se zaměřili na analýzu jedinců v reprodukční fázi. Zaznamenané výsledky je možno interpretovat na základě již zmíněných hypotéz. Potvrzen byl mechanismus Hamilton Zuk hypotézy (vztah endoparazitů a třecí vyrážky), nebyla potvrzena hypotéza imunokompetenčního handicapu i když se zdá, že androgeny by mohly hrát určitou roli v imunokompetenci rybího hostitele. Dále byla potvrzena sperm protection hypotéza (pozitivní vztah mezi spermatokritem a slezinou, trend pozitivního vztahu spermatokritu a třecí vyrážky).

Abstract:

1)A link between immunocompetence of chub (Leuciscus cephalus L.) and parasitism The role of immune function is recently widely investigated in the context of trade-off between the different lifehistory traits. Each potential host is exposed to variety of parasites that may negatively influence its viability, and then the host must develop a performing immune system in order to generate the resistance towards the parasites and to reduce the fitness losses caused by parasitism. Therefore, we hypothesized and tested a link between fish immunocompetence and parasitism. We performed the investigation of chub parasitofauna from one locality of Svitava River in four seasonal samples (spring, early summer, late summer and autumn) during 2004. Several measures connected fish immunocompetence and physiological status were selected and measured: blood cell counts, hematocrit,leucocrit, phagocyte activity and spleen size. We tested the seasonal changes in those parameters. Parasite communities of all seasonal fish samples were analysed. The total parasite species richness varied from 17 to 20 per sample.The highest parasite diversity was recorded in the first sample (Shannon index diversity). Monogenea were the group with the highest prevalence and mean abundance in all samples. Digenea were the second abundant group in all samples. The high values of prevalence but low mean abundance were recorded for Acanthocephala in the first and third samples (spring and later summer). The positive correlation between spontaneous and activated phagocyte activity was found in the majority of fish in all samples. The statistical significant differences were found aminy seasonal samples for the groups Monogenea and Mollusca being more abundant in spring, Cestoda being more abundant in early summer and Acanthocephala being more abundant in autumn. Infracommunity metazoan parasite species richness was significantly higher in spring sample. Moreover, we found significantly higher numbers of protozoan Myxobolus spp. in autumn sample. The analyses of immunocompetence revealed that spleen size is higher in autumn sample. Measures connected with phagocyte aktivity were higher in late summer or autumn samples. Special types of neutrophils were found in significantly higher numbers in the spring samples. The results indicated thepotential connection between fish immunocompetence and parasitism. 2)THE LINKS BETWEEN IMMUNOCOMPETENCE, REPRODUCTION AND PARASITISM IN CHUB (LEUCISCUS CEPHALUS) Life-history theory predicts that each organism has a limited amount of energy which is allocated among different expensive activities performing the maintenance and reproduction. The ability of immune system to defense hosts against parasites is one of the most important determinant of life history influencing reproductive success. Therefore, the aim of this study was to analyze the relationships between immunocompetence and parasitism in three different periods: prereproductive, reproductive and postreproductive. The different investments between reproduction and immunity were hypothesized in each period following the trade-off prediction in energy allocation, hypothesis of Hamilton and Zuk (1992) and immunocompetence handicap hypothesis. Moreover, the sperm protection hypothesis was tested predicting that better elaborated sexual ornamentation indicates the better sperm quality of males but with increasing risk of parasitism. A total of 90 males of chub (Leuciscus cephalus) were collected from one locality (the confluence of the Svitava and Svratka) and analyzed. The selected physiological and immunological parameters (gonad size, condition factor, hematocrit, leucocrit, respiratory burst, spleen size, the proportion of blood cells, spermatocrit, breeding tuberles) were measured and the fish were investigated for metazoan parasites. No significant difference was found for spleen size among prereproductive, reproductive and postreproductive samples. No significant difference

Abstract:

was observed for blood cells (lymphocytes, monocytes, neutrophils). In the reproductive period the wide range of the values measured in individuals for respiratory burst (chemiluminescence) was found when comparing with prereproductive and postreproductive periods. The significant difference was found for condition factor (CF) and gonado-somatic index (GSI) among samples with higher values for the fish in the prereproductive period. In the prereproductive period the total metazoan parasite diversity was not associated with any measure of immunocompetence or the investment in reproduction. The positive association was found between GSI and CF, whilst the spleen size was negative associated with both variables, which could be interpreted in the view of trade-off in energy allocation. A positive relationship between spleen size and parasite diversity was observed only in the reproductive period. Moreover, the total parasite abundance increased with the number of fagocytes. We also confirmed that the expression of sexual traits reflects the sperm quality of the males and is connected with higher endoparasite abundance which is consistent with sperm protection hypothesis. Sexual ornamentation reflects the degree of parasite infection which should be interpreted in the view of the mechanism of Hamilton and Zuk hypothesis. In the postreproductive period, both spleen size and the number of fagocytes showed a trend of negative associations with total parasite diversity and abundance. However, the highly parasitized individuals showed the higher condition factor. A negative association between GSI and CF was found. The results of the analyses of three different periods in the relation to the reproduction could partially support the immunocomptence handicap hypothesis.

Keywords

immunocompetence, fish, parasitism, season changes, reproduction, imunokompetence, sezónní změny, parazitismus, Leuciscus cephalus, jelec tloušť

Language used: Czech

Date on which the thesis was submitted / produced: 26. 5. 2006

Thesis defence

• Date of defence: 8. 6. 2006
• Supervisor: doc. RNDr. Andrea Vetešníková Šimková, PhD.

Masaryk University

Faculty of Science

Master programme / field:
Biology / General Biology