INTRODUCTION. Ergasilids have attracted the interest of many scientists. since late nineteenth century. Of the many papers which

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INTRODUCTION Ergasilids have attracted the interest of many scientists since late nineteenth century. Of the many papers which have appeared, large number are purely descriptive.

1 INTRODUCTION Ergasilids have attracted the interest of many scientists since late nineteenth century. Of the many papers which have appeared, large number are purely descriptive. Ergasilus sieboldi is the type species of the genus and was first described by Nordmann (1832) from pike, white fish and eel in Europe. Since then the parasite has been redescribed by Wilson (1911), Neuhaus (1929), Markewitsch (1931), Gurney (1933), Halisch (1940), Yin (1956), srnirnova (1962), Yamaguti (1963), Fryer (1969,1982) and Kabata (1979). Neoergasilus japonicus was first described by Harada (1930) from freshwater fish in Formosa as Ergasilus japonicus. Yin (1956) created the genus Neoergasilus and differentiated it from Ergasilus by the structure of the first swimming leg which in Neoergasilus is more prolonged and the spine of the second segment of its exopod is swollen into a thumb-like projection. The basis of that leg also carries a triangular tooth supporting both rami. N. japonicus was further redescribed in USSR (Smirnova 1962), China (Yamaguti 1963), Czechoslovakia (Hanek 1968), France (Lescher-Moutoue 1979) and Britain ( Mugridge et al 1982 and Fryer 1982). It has been known that Ergasilidae exhibit the primitive cyclopoid morphology with few but effective, adaptations 24

2 for parasitism (Wilson 1911, Henderson 1927, Bauer 1962, Kabata 1979 and Cressey 1983). In literature, disputes on identity of ergasilid species appear to occupy large space of most discussions (Halisch, 1935a,b; Fryer, 1960,1964, 1965,1968; Roberts, 1969a,b,1970; Kabata, 1979 and Thatcher, 1981a,b,1984). Despite this, there are still no clear morphological lines j~,f)}~j; m= ~ pep~.djjj...d ~cjes_.-mast of the arguments, on species identification, are based on insignificant features which could be due to inaccurate observations. Roberts (1969a) reported that E. vesicolor recorded by McDaniel (1963) and E. lizae of Kelley and Allison (1962) was definitely E. arthosis while E. elegans(=e. versicolor) recorded by Muller (1936) was neither E. versicolor nor E. arthrosis but represent a different species, which later described by Roberts (1969b) as E. cerastes. According to Cressey and collette (1970) E. spatulus is very similar to E. arthrosis and can be separated from other similar species only by the row of spatulate spines on the first endopod segment of the second leg and the broad spines on the last segment of the first leg. According to Burris and Miller (1972) E. rhinos differs 25

from all North American species of the genus Ergasilus in the armature of the second antenna though the same authors acknowledge its similarity to E.

3 from all North American species of the genus Ergasilus in the armature of the second antenna though the same authors acknowledge its similarity to E. centrarchidarum except in the above mentioned character and the structure of the mouth appendages. Voth and Larson (1968) reported E. confusus from the fish in North Dakota (USA) but when specimens were re-examined by Johnson (1971) he claimed that was E. wareaglei. According to Johnson (1971) E. wareaglei could be considered E. centrarchidarum, except for the spherical inflation between the first two segments of the second antenna of the former. Bricker et al (1978) reported that E. megaceros and E. chautauquaensis are morphologically similar except for the length of the second antennae. According to Thatcher (1981b) E. leoporindis is similar to E. bryconis but it lacks the pectination on outer seta of the terminal segment of the first exopod and the former species is smaller and has a longer second antenna with a single sensillum on its third segment and not on the second as in E. bryconis. Thatcher and Robertson (1982) E. jaraquensis and E. bryconis are similar except that the former has two 26

"spinules" on the third segment of the second antenna, which are lacking in E. bryconis. Varella (1985) described two "spinules" on the third segment of the second antenna of E.

4 "spinules" on the third segment of the second antenna, which are lacking in E. bryconis. Varella (1985) described two "spinules" on the third segment of the second antenna of E. bryconis collected in the same locality. Thatcher and Robertson (1982) also claimed that while E. bryconis has 3 setae on each caudal ramus, E. jaraquensis has only 2 setae on the caudal ramus. However, Varella (1985) proved that E. bryconis, like all other ergasilids, has 4 setae on each caudal ramus. Paperna and Lahav (1971), who described E. fryeri from Tilapia zillii, reported that the same material was identified by Gussiev, Shul'man and Strelkov (USSR) as E. sieboldi (Lahav and Sarig, 1967) and that was confirmed also by Bauer, who rechecked the same materials. Paperna and Lahav (1971) admitted that the two species are identical in most details except leg 5 which has 3 terminal setae in E. fryeri while only 2 setae are present in E. sieboldi. Despite the large number of ergasilids described to date, the literature contains a fairly small number of fragmented, sometimes confusing, reports on the life cycle of ergasilid copepods. However, most of the dispute is centred around the number of the nauplial stages. According to Willson (1911) E. centrarchidarum has one nauplius and two metanauplius stages. Halisch (1940) described the same stages for E. briani while Gurney 27

(1933) described four naupliar stages for Thersitina gasterostei. yin (1956) mentioned five stages for Sinergasilus major though he described only two of them.

5 (1933) described four naupliar stages for Thersitina gasterostei. yin (1956) mentioned five stages for Sinergasilus major though he described only two of them. More recent work by Zmerzlaya (1972) on E. sieboldi, Musselius (1967) and Mirzoeva (1972,1973) on S. lieni, Ben Hassine (1983) on E. lizae and Varella (1985) on E. bryconis also revealed three stages of nauplial development. Fryer (1978) concluded that the development of the nauplii is very imperfectly known for most ergasilid species but is probably similar in all. Kabata (1981) believed that the six nauplii of the free living cyclopoid copepods tend to be abbreviated in parasitic copepods and in all ergasilids only three naupliar stages have remained. However, Urawa et al (1980a) confirmed that N. japonicus has six nauplius stages. As far as the copepodid stages are concerned all early studies have confirmed that in ergasilids so far studied five stages exist in addition to the free living adult cyclopoid stage (Gurney, 1933; Yin, 1956; Mirzoeva, 1972; Zmerzlaya, 1972; Urawa et al, 1980b; Ben Hassine & Raibaut, 1981; Ben Hassine, 1983 and Varella, 1985) with the exception of Halisch (1940) who described only four stages for E. briani. In view of all these discussion and arguments, bearing in mind all previous studies on E. sieboldi and N. japonicus, the present.study was carried using SEM for the first 28

6 time to investigate the morphology of the parasi tic females in order to elicit more of the external anatomy of these species. As the morphology represents a major criterium in the taxonomy of ergasilids (Wilson 1911, Harada 1930, Yin 1956, Yamaguti 1963, Fryer 1965, Robert 1970 and Kabata 1979,1981) this study was meant to shed more light on the taxonomy of these genera and hence the whole family. Despite the earlier findings by Zmerzlaya (1972) on E. sieboldi life cycle, successful rearing of the free living stages in laboratory conditions during the course of this study gave an opportunity to study the development and morphology in more detail using SEM. The morphology of the free-living stages might offer valuable clues to intrafamilial relationships (Kabata 1976) as the larval morphology has not been taken into taxonomic and phylogenic consideration (Izawa, 1987). 29

MATERIAL AND METHODS Females Ergasilus sieboldi were collected from tench, carp, rainbow trout and bream taken from different sites in Middle Thames valley throughout the period 1986-1988.

7 MATERIAL AND METHODS Females Ergasilus sieboldi were collected from tench, carp, rainbow trout and bream taken from different sites in Middle Thames valley throughout the period Females Neoergasilus japonicus were also collected from the fins of bream taken from Boldermere Lake (Surrey) in the summer The copepods were carefully removed from the gills and fins of the respective host fish, washed in distilled water to remove mucus and large debris. Specimens were fixed in 4% phosphate buffered glutaraldehyde for hours at 4 0 C, then washed in 1% phosphate buffer and rinsed in distilled water. To remove any debris, specimens were placed in a dilute solution of Tween-80 (3 drops in 100 ml of distilled water) for 30 minutes and transferred to an ultrasonic cell disruptor to sonicate for seconds (Felgenhaur, 1987). Specimens were washed in 3 changes of distilled water and shaken in 16% glycerol solution for 12 hours to draw out any attached mucus. To remove the glycerol, specimens were changed three times in 20% ethanol, shaken continuously for 6 hours, followed by dehydration in increasing grades of ethanol to dry absolute ethanol, critical point dried, mounted on aluminium stubs, coated with gold and viewed with a Cambridge Stereoscan

8 1137 specimens of E. sieboldi and 218 specimens of N. japonicus were examined for the external anatomy. Similarly free-living stages of E. sieboldi were prepared and examined for external anatomy. 31

ZOOLOGISCHE MEDEDELINGEN

ZOOLOGISCHE MEDEDELINGEN UITGEGEVEN DOOR HET RIJKSMUSEUM VAN NATUURLIJKE HISTORIE TE LEIDEN (MINISTERIE VAN CULTUUR, RECREATIE EN MAATSCHAPPELIJK WERK) Deel 43 no. 11 20 december 1968 PARABOMOLOCHUS GLOBICEPS