Ola A. Abu Samak. Department of Zoology, Damietta Faculty of Science, New Damietta, Egypt.

Transcription

1 MORPHOLOGY OF SCIAENOPHILUS PHARAONIS (COPEPODA: CALIGIDAE) WITH A REDESCRIPTION OF THE FEMALE, INFESTING MEAGRE FISH (ARGYROSOMUS REGIUS) IN EGYPTIAN MEDITERRANEAN WATERS Ola A. Abu Samak Department of Zoology, Damietta Faculty of Science, New Damietta, Egypt. Key words: Caligidae; Sciaenophilus pharaonis; Morphology; Argyrosomus regius; Sciaenidae; Mediterranean Sea; Egypt. ABSTRACT The male and female of the parasitic caligid copepod Sciaenophilus pharaonis (Nordmann, 1832) Humes, 1965, from meagre fish (Argyrosomus regius; Sciaenidae) captured from Egyptian Mediterranean coast, are described whereas the male for the first time. The host and locality records are new. The present study revealed that the body and most appendages of the male are smaller than those of the female. However, the free thoracic segment is larger than that of the female and the ratio of the cephalothorax and abdomen lengths to total body length are also higher in the male. The male also differs from the female in the structure of the third, fifth and sixth thoracic legs. The mouth tube is typical of the members of family Caligidae. The marginal membrane is made up of hairlike processes with short free extremities, which may provide a watertight tube during feeding. Numerous projections, including seta-like hairs, dome-like papillae and minute spines, covering the ventral surface of the lateral margin of the cephalothorax, which may have a sensory function. A forked sternal plate has been detected with the scanning electron microscope in Sciaenophilus pharaonis, in a similar position to the sternal furca of Caligus spp.. In contrast with Caligus spp., the longitudinal axis of the cephalothorax of attached specimens of S. pharaonis lies at an acute angle with the longitudinal axis of the rest of the body. An earlier report of S. pharaonis from the freshwater Nile perch (Lates niloticus) is discussed. 1

2 INTRODUCTION The genus Sciaenophilus was erected by Beneden (1852) for Sciaenophilus tenuis. Sciaenophilus pharaonis was originally described by Humes (1957) as Sciaenophilus inopinus, from the gills of the freshwater Nile perch (Lates niloticus) collected from Giza Fish Market, Egypt. Humes (1965) compared S. inopinus with another related species, Caligus pharaonis Nordmann, 1832, which was collected from the operculum of a marine fish, (Chrysophrys bifasciatus), in the Red Sea, Egypt. He concluded that S. inopinus is a synonym of Nordmann s species and listed it as S. pharaonis (Nordmann, 1832). All the previous studies concerning S. pharaonis were only based on the description of female specimens. In addition to Sciaenophilus pharaonis, 5 other species belong to this genus, namely: S. tenuis Beneden, 1852; S. benedeni Bassett-Smith, 1898; S. macrurus Heller, 1865; S. nibae Shen, 1957 and S. bennetti Causey, For a long time, species of the genus Sciaenophilus were confused with species of the genus Caligus Müller, Some authors (Wilson, 1905; Parker, 1968; Margolis et al., 1975) assigned them to Caligus, while others (Capart, 1941; Humes, 1957; 1965; Yamaguti, 1963; Kabata, 1979; Dojiri, 1983) related them to a separate genus namely Sciaenophilus. The availability of the previously undescribed males of Sciaenophilus pharaonis together with females in Egypt prompted the present study. The morphological features of the male were compared with those of the female, taking into consideration the differential generic criteria of Sciaenophilus and the closely related genus Caligus. MATERIALS AND METHODS About 20 male and 20 female specimens of Sciaenophilus pharaonis were collected from the inner surface of the operculum of meagre fish (Argyrosomus regius) caught from El-Lessan region of Ras El-Bar on the Mediterranean Sea, Damietta Governorate, Egypt. For light microscopy, the parasites were initially fixed in 10% formalin and transferred to 70% ethanol for storage. Parasites were stained for whole mount preparation with alum carmine, cleared in terpeniol and mounted in Canada balsam. All measurements were made on parasites relaxed in 85% lactic acid for at least 24 hrs (Humes and Gooding, 2

3 1964) and are given in micrometers with the average followed by the range in brackets. Drawings were made with the aid of a camera lucida. For scanning electron microscopy (SEM), some individuals were initially fixed in 1% osmium tetroxide in 0.1M sodium cacodylate buffer (ph 7.2) for 2 hrs at 4 ºC and post-fixed in 2.5 % glutaraldehyde at 4 ºC overnight. They were washed in the buffer, dehydrated through an ascending series of ethanol, dried in CO 2, coated with gold and examined using a Jeol-JSM-5300 scanning electron microscope operating at accelerating voltages of 10 and 20 kv. RESULTS Body of male S. pharaonis (Figs. 1A & 2A) elongate, as in female (Figs. 1B & 2B). Average total length, excluding caudal rami: of male, 3372 ( ) µm; of female, 4078 ( ) µm respectively. In both sexes, cephalon and first three thoracic segments fused to form cephalothorax, measuring in male 719( ) µm x 684 ( ) µm and in female 799 ( ) µm x 674 ( ) µm (about 20% of total body length in both sexes). Cephalothorax flattened dorsoventrally, shaped like a ladle, at an angle of about 50º with longitudinal axis of body (Fig. 2C), divided dorsally into 4 unequal parts (large cephalic, small thoracic and two narrow laterals) by suture lines. Ventral surface of lateral margin of cephalothorax with distinct border, seen with SEM bearing parallel oblique ridges and three kinds of cuticular structures: seta-like hairs, dome-like papillae and minute spines. These structures do not occur posterior to third legs (Figs. 2E &F). Anterior region of cephalothorax formed by frontal plates (Figs. 1A & 3A). Each plate occupies distance from midline junction to proximal segment of first antenna (Figs. 3A & B), wider than long in both male and female and measuring in male 47 (44-49) µm x 164 ( ) µm and in female 71 (60-79) µm x 200 ( ) µm. Frontal organ, that produces frontal filament in chalimus larva, is seen in adult as circular depression, located ventrally at junction of frontal plates (Fig. 3B). Anterolateral end of each frontal plate in both sexes with subcircular lunule (Figs. 3B & 5A), just wider than long, 40 (33-45) µm x 60 (57-69) µm in male and 54 (50-58) µm x 90 (80-100) µm in female. 3

4 Fourth thoracic segment free in both sexes, markedly wider than long (Figs. 1A & 2A), 137 ( ) x 245 ( ) µm in male and 66 (60-70) x 139 ( ) µm in female (comprising about 19% in male and 8% in female of total cephalothorax length). Genital complex slightly cordiform in both sexes, comprising fused genital and fifth thoracic segments, markedly distinguished from fourth thoracic segment (Figs. 1A,B & 2A,B). It is longer than wide in male, being 1014 ( ) µm x 806 ( ) µm, (about 30% of total body length) and identical in length and width in female, that was 1098 ( ) µm x 1098 ( ) µm, (about 27% of total body length). Inside the genital complex of female, convoluted oviduct and segmented cement glands could be easily seen with light microscope (Fig. 1B). Egg strings uniseriate, elongate, 3250 ( ) µm x 253 ( ) µm, (about 80% of total body length) (Figs. 1B & 2B). Each string contains 39 (37-40) eggs, all disc-shaped except the first and the last ones (Figs. 1B & 3C). Abdomen, two-segmented, long, slender, slightly separated from genital complex (Figs. 1A,B & 2A,B), longer than wide in both sexes, 1833 ( ) µm x 351 ( ) µm in male and 1975 ( ) x 385 ( ) µm in female (about 54% in male and 48% in female of total body length). First abdominal segment elongate, 1785 ( ) µm x 351 ( ) µm in male and 1750 ( ) µm x 385 ( ) µm in female. Second abdominal segment small, 213 ( ) µm x 164 ( ) µm in male and 185 ( ) µm x 229 ( ) µm in female (about 12% in male and 9% in female of total abdomen length). Caudal rami with one segment in both sexes (Figs. 1 A, B & C), short, 72 (42-77) µm x 49 (60-110) µm in male and 163 ( ) µm x 100 (79-120) µm in female. Proximal and distal ends narrower than most of ramus (Fig. 1C). Each ramus with one outer and one inner short pinnate seta and between them four large pinnate setae. First antenna in both sexes two-segmented (Fig. 5A) typical for the family. Large proximal segment trapezoid, stout, much broader than distal segment, with ventrally 20 large plumose setae arranged in three groups (10 anteriorly directed, 8 posterolateral at the distal margin and two at the proximal margin). Long, slender distal segment armed with 4

5 single small spine, posterolaterally directed midway along posterior margin and tuft of 13 setae at distal end arranged as four long plumose setae and 10 short naked setae. Second antenna in both sexes (Fig. 5B) three-segmented: narrow proximal segment with tapering anterior margin and rounded posterior margin; stout middle segment, subrectangular with posterior, small, spherical, naked process; long distal segment and slender with apical and strongly recurved hook. Postantennal process in both sexes (Fig. 5C) small, with two pointed distal processes, together resembling a forceps. Mouth tube in both sexes (Fig. 4A) ventrally located, midway between lunules (Fig. 3B), longer than wide with broader proximal end and narrow distal end, formed by partial fusion between labium and labrum. Rim of both labium and labrum fringed with long, thick hair-like structures (= membrane) in a single row on labium and double rows on labrum, with double or triple short, free extremities (Figs. 4C & D). Mandibles located symmetrically on each side of labial groove, coming together to form U - shaped structure, distal part of each mandible with 12 strong curved teeth (Fig. 4B). Inner surface of labium forming a ridge (= labial fold) provided with two hard cuticular bars, each armed with about 30 minute teeth and together forming the strigil (Fig. 4B). Each side of mouth cavity supported by a single buccal stylet lying at junction between labium and labrum (Fig. 4B). Postoral process a part of the first maxilla in both sexes (Fig. 5D) ventrally located on each side of mouth tube, with trapezoid proximal region and pointed distal region having slightly curved claw and armed with two accessory processes (one long curved, needle-like and other short with broader membrane at distal end). First maxilla in both sexes (Fig. 5E) small with broad spherical base armed with anteriorly directed process extended distally as single, strong, curved, hook-like structure. Second maxilla in both sexes (Fig. 5F) three-segmented: unarmed proximal segment; larger middle segment with small curved spine, anterolaterally directed; long slender distal segment with single, small, posterolaterally directed spine and at distal end two naked setae, arranged as one long anterior seta and one short posterior seta. Maxilliped in both sexes (Fig. 5G) two-segmented: large stout proximal segment with small, anteriorly directed spine at inner margin of the basal portion; long distal 5

6 segment forming a strong, inwardly curved claw. Sternal furca characteristic of members of genus Caligus was not detected in S. pharaonis, but sternal plate covering cephalothoracic segment at level of maxillipeds was seen with SEM and appeared forked (Fig. 3B). First thoracic leg in both sexes biramous (Figs. 3D & 5H), comprising coxa, basis, exopod and endopod. Coxa armed with three spines: one proximally and posteriorly directed and two distally and laterally directed. Basis unarmed, long and slender. Exopod one-segmented, armed with five, short, naked, apical setae and 6 long plumose setae along the lateral border. Endopod is vestigial. Second thoracic leg in both sexes biramous (Figs. 3D & 5I), comprising coxa, basis, exopod and endopod. Coxa small, with a long plumose posterior seta. Basis large and broad, armed with small anterolateral seta near base of exopod. Exopod three-segmented: large proximal segment, bearing one long apical spine and one short medial spine, small median segment, bearing single long apical spine and broad distal segment ornamented with 6 long pinnate medial setae, increasing in length from outermost inwards. Endopod three- segmented: small proximal segment bearing one plumose lateral seta (longest on second thoracic leg); large median segment bearing small outer spine, one long plumose apical seta and one long plumose lateral seta; rounded distal segment ornamented with 6 long, plumose apical setae. Setae on endopod increase in length from outermost inwards. Third thoracic leg in male biramous (Fig. 5J), protopodite fused with posterior border of cephalothorax, comprising one-segmented exopod armed with three lateral spines and 5 plumose apical setae, the middle two of which are longest, and the small onesegmented endopod. This leg in female consists of flattened plate fused with posterior border of cephalothorax (Fig. 5J), with three-segmented exopod and two-segmented endopod; first segment of exopod with single outer claw, second segment with one outer long plumose seta and third segment with four plumose setae and three spines increasing in length form innermost outwards. First segment of endopod with one, inner, long, plumose seta; second segment with six plumose setae increasing in length from outermost inwards. 6

7 Fourth thoracic leg in both sexes (Figs. 3D & 5K) four-segmented: unarmed small coxa; long slender basis ornamented with two small postero-lateral spines, one-segmented triangular exopod, with one, long, naked apical seta; one-segmented endopod with four, long, outer, naked setae and one small apical spine. Exopodal and endopodal setae increase in length from outermost inwards. Fifth and sixth thoracic legs in both sexes rudimentary (Fig. 5L), projecting from postero-lateral border of genital complex; represented by small papillae with two naked setae in male and one, long naked seta in female. The measurements of all appendages are shown in Table 1. DISCUSSION The parasitic copepod Sciaenophilus pharaonis (Nordmann, 1832) Humes, 1965 is reported for the first time from the meagre fish, Argyrosomus regius. The parasite has not been reported previously in the eastern Mediterranean and the male is hereby described for the first time. The basic morphological features and the body measurements of female specimens of S. pharaonis, as determined in the present study, corroborate with previous observations of Nordmann (1832) and Humes (1957). The morphological features of the male parasite are similar to those of the female, with the exception of the third, fifth and sixth thoracic appendages. In addition, males are smaller in size, have larger free thoracic segments and higher ratios of both cephalothorax and abdomen lengths to the total body length. In this respect, the limited morphological variation detected between the present male and female S. pharaonis, agree with those reported for most copepod parasites, especially those belonging to family Caligidae (Hameed and Pillai, 1986; Lin, 1989; Lin et al., 1994; Boxshall and Bravo, 2000). The genus Sciaenophilus was erected by Beneden (1852) and was characterized by the comparatively small cephalothorax, small lunules, extremely large maxillipeds, elongate and slender abdomen and the absence of a sternal furca. This genus was considered for a long time as a subgenus of Caligus Müller, 1785 (see Heller, 1865; Bassett-Smith, 1898; Wilson, 1905; Margolis, et al., 1975). However, in other studies, it 7

8 was regarded as a distinct genus of the family Caligidae (see Humes, 1957, 1965; Yamaguti, 1963; Kabata, 1979; Dojiri, 1983). The present study supports the validity of the genus Sciaenophilus, confirming the absence of a sternal furca. However, SEM has revealed the presence in S. pharaonis of a small forked plate at the site of the sternal furca in Caligus, i.e. covering the cephalothoracic segment at the level of the maxillipeds. This plate was not visible with the light microscope. It has also been observed that the longitudinal axis of the cephalothorax of S. pharaonis lies at an angle to the longitudinal axis of the body when attached to the host. In contrast, this feature has not been reported in any previous study concerned with Caligus spp.. If this turns out to be a feature of other species of Sciaenophilus, it would be a useful differential criterion between the two confused genera. The mouth tube of S. pharaonis resembles, in general, that of most caligid species in which the labia converge forming a mouth tube or siphon (Markewitch, 1976). The marginal membrane at the rim of both labium and labrum is made up of long and thick hair-like structures with double or triple short free extremities, forming a single row on the labium and a double row on the labrum. In the only ultrastructure study of the caligid mouth tube, Kabata (1974) found a single row of hair-like structures forming a membrane on both the labium and the labrum in two species of Caligus (C. curtus and C. clemensi) and in one species of Lepeophtheirus (L. salmonis). He reported that sometimes, this membrane is provided with a row of short setae along the base as in C. curtus. Since the hairs are fused proximally, the marginal membrane could provide a watertight tube for the mouth during feeding, as suggested by Kabata (1974), creating a closed chamber, where the teeth of the strigil and mandibles can abrade host tissue. Three cuticular structures, namely seta-like hairs, dome-like papillae and minute spines, are present on the ventral surface of the lateral margin of the cephalothorax of S. pharaonis. This is the first time to demonstrate such structures in Sciaenophilus. The setalike hairs and dome-like papillae may have a sensory function. S. pharaonis was first recorded by Nordmann (1832) as Caligus pharaonis collected from the inner surface of the operculum of Chrysophrys auratus (Sparidae) taken from the Red Sea. The meagre, Argyrosomus regius (Sciaenidae), is a new host record for this 8

9 parasite, assuming the specific identity of the Mediterranean and Red Sea parasites. It is noteworthy that S. tenuis, S. benedeni and S. nibae, as well as S. pharaonis, have been reported from sciaenid fishes. Curiously, S. pharaonis was also reported from a freshwater fish, the Nile perch (Lates niloticus; Centropomidae) at Giza Fish Market, Cairo, Egypt (Humes, 1957). Humes study was based on 29 parasitic copepods collected during December 1952, and January-February, However, during a survey of Nile perch in 1997, no Sciaenophilus spp. were found on the gills or in the branchial cavity (previously unpublished observation) and it seems likely that L. niloticus is rarely infected at the present time. Humes (1957) suggested that L. niloticus occasionally enter brackish or salt water, like other members of the family, and A. regius is known to enter Bardawil Lagoon when hypersaline conditions are moderate (Paperna and Lahav, 1975). These fish movements would provide opportunities for contact between the two fishes and for the transfer of parasites from A. regius to L. niloticus. Survival of the parasite in brackish and fresh water may then be limited. If S. pharaonis is able to tolerate life in freshwater as well as in the sea, then the prevalence of the parasite may have declined on L. niloticus during the latter half of the last century. This correlates with a substantial increase in pollution of Nile waters during this period (Dekov et al., 1997), and there may be a causal connection between the two. Poulin (1992) suggested that parasitic copepods and branchiurans might be affected and consequently disappear at pollutant levels that have little effect on fish. REFERENCES Bassett-Smith, P.W. (1898). Some new parasitic copepods found on fish at Bombay. The Annals and Magazine of Natural History, 7: Beneden, P.J. van (1852). Note sur un quelques parasites d un poisson rare sur nos côtes (le maigre d Europe, Sciaena aquilla, Cuv.). Bulletin de l Académie Royale des Sciences de Belgique, 19: Boxshall, G.A. and Bravo, S. (2000). On the identity of the common Caligus (Copepoda: Siphonostomatoida: Caligidae) from salmonid netpen systems in southern Chile. Contributions to Zoology, 69: Capart, A. (1941). Résultats scientifique des croisières du navire-école Belge Mercator. Vol. III. 5. Copepoda parasitica. Mémoires du Muséum Royal d Histoire Naturelle de Belgique, sér. 2,

10 Dekov, V.M., Komy, Z., Araujo, F., Van Put, A. and Van Grieken, R. (1997). Chemical composition of sediments, suspended matter, river water and ground water of the Nile (Aswan-Sohag traverse). Science of the Total Environment, 201: Dojiri, M. (1983). Revision of the genera of the Caligidae (Siphonostomatoida), copepods predominantly parasitic on marine fishes. Ph.D. Dissertation, Boston University, Boston, Massachusetts, U.S.A. Hameed, M.S. and Pillai, N.K.S. (1986). A new species of Caligus (Copepoda: Caligidae) from Kerala. Indian Journal of Fisheries, 33: Heller, C. (1865). Reise der osterreichischen Fregatte Novara um die Erde in den Jahren 1857, 1858, Zoologica Theil. 2: Humes, A. G. (1957). Two new caligoid copepods from Egyptian fishes. Journal of Parasitology, 43: Humes, A.G. (1965). Sciaenophilus inopinus Humes, 1957, a synonym of Sciaenophilus pharaonis (Nordmann, 1832) comb. n. (Copepoda: Caligidae). Journal of Parasitology, 51: Humes, A.G. & Gooding, R.U. (1964). A method for studying the external anatomy of copepods. Crustaceana, 6: Kabata, Z. (1974). Mouth and mode of feeding of Caligidae (Copepoda), parasites of fishes, as determined by light and scanning electron microscopy. Journal of the Fisheries Research Board of Canada, 31: Kabata, Z., (1979). Parasitic Copepoda of British fishes. London: The Ray Society, 125: 468pp. Lin, C.-L. (1989). A new species of Caligus (Copepoda, Caligidae) parasitic on milkfish (Chanos chanos). Crustaceana, 57: Lin, C.-L., Ho, J.-S. and Chen, S.-N. (1994). Two species of Caligus (Copepoda: Caligidae) parasitic on blank sea bream (Acanthopagrus schlegeli) cultured in Taiwan. Fish Pathology, 29: Margolis, L., Kabata, Z. and Parker, R.R. (1975). Catalogue and synopsis of Caligus, a genus of Copepoda (Crustacea) parasitic on fishes. Bulletin of the Fisheries Research Board of Canada, 192: 117pp. Markewitch, A.P. (1976). Parasitic copepods on the fishes of the USSR. Indian National Scientific Documentation Centre, New Delhi, 445pp. Müller, O.F. (1785). Entomostraca, seu Insecta testacea quae in aquis Daniae et Norvegiae resperit. F.W. Thiele, Leipzig and Copenhagen, 136 pp. Nordmann, A. von. (1832). Mikrographische Beiträge zur Naturgeschichte der wirbellosen Thiere. Heft 2. G. Reimer, Berlin, Ger. I-xviii, Paperna, I. and Lahav, M. (1975). Parasites of fish of the hypersaline Bardawil Lagoon, North Sinai. A preliminary communication. Rapport et procés-verbaux des réunions. Commission Internationale pour l exploration scientifique de la Mer Méditerranée, 23: Parker, R.R. (1968). Caligus longicaudatus Brady, 1899 (Caligidae: Copepoda). Bulletin of the British Museum (Natural History). Zoology series, 15: Poulin, R. (1992). Toxic pollution and parasitism in freshwater fish. Parasitology Today, 8:

11 Shen, C.-J. (1957). Parasitic copepods from fishes of China. II. Caligoida, Caligidae (1). Acta Zoologica Sinia, 9: Wilson, C.B. (1905). North American copepods belonging to the family Caligidae. Part. I. The Caliginae. Proceedings of the United States National Museum, 28: Yamaguti, S. (1963). Parasitic Copepoda and Branchiura of fishes. Interscience Publishers, New York, London, and Sydney pp. Table I. Measurements (average maximum length X average maximum width in µm) of the appendages of the parasitic copepod, Sciaenophilus pharaonis (Nordmann, 1832) Humes, Appendages Male Female First antenna Second antenna Postantennal process Mouth tube Postoral process First maxilla Second maxilla Maxilliped First thoracic leg Second thoracic leg Third thoracic leg Fourth thoracic leg Fifth and sixth thoracic legs 125 x x x x x x x x x x x x x x x x x x x x x x x x x x 3 LEGEND OF FIGURES Figure 1. Schematic drawing of male (A) and female (B) parasitic copepod, Sciaenophilus pharaonis (Nordmann, 1832) Humes, 1965 and its enlarged single ramus (C). a, abdomen; ce, cephalothorax; cov, convoluted oviduct; e, eggs; es, egg string; fp, frontal plate; fs, free thoracic segment; g, gut; gc, genital complex; scg, segmented cement glands and sl, suture lines. Figure 2. Scanning electron micrographs of Sciaenophilus pharaonis (Nordmann, 1832) Humes, (A) male and (B) female in ventral view. (C) attitude of the parasite attached to host tissue (ht) and (D) cephalothorax in ventro-lateral view. (E and F) ventral views of margin of cephalothorax. a, abdomen; ce, cephalothorax; es, egg string; fs, free thoracic segment; gc, genital complex; lm, lateral margin; ms, minute spines; or, oblique ridges; p, dome-like papillae and s, seta-like hairs. 1

12 Figure 3. Sciaenophilus pharaonis (Nordmann, 1832) Humes, (A) Scanning electron micrograph of antero-lateral region of cephalothorax, in dorsal view. (B) Scanning electron micrograph of anterior region of cephalothorax, in ventral view. (C) Light micrograph of part of an egg string. (D) Scanning electron micrograph of posterior region of cephalothorax, in ventral view. A1, 1 st antenna; e, eggs; efp, edge of frontal plate; fo, frontal organ; fp, frontal plate; fs, free thoracic segment; L1, 1 st thoracic leg; L2, 2 nd thoracic leg; L4, 4 th thoracic leg; l, lunule; m, maxilliped; mot, mouth tube and sp, sternal forked plate. Figure 4. Scanning electron micrographs of mouth tube of Sciaenophilus pharaonis (Nordmann, 1832) Humes, 1965, in ventral view. (A and B) mouth parts. (C) single row of hair-like structures on labium rim (=labial membrane). (D) double rows of hair-like structures on labrum rim (= labral membrane). bs, buccal stylet; df, debris of food; fe, free extremities; h, hair-like structures; lf, labial fold; li, labium; lim, labial membrane; lr, labrum; lrm, labral membrane; mc, mouth cavity; mt, mandibular teeth and st, strigil. Figure 5. Schematic drawing of appendages of Sciaenophilus pharaonis (Nordmann, 1832) Humes, (A) 1 st antenna and lunule, (B) 2 nd antenna, (C) postantennal process, (D) mouth tube and postoral process, (E) 1 st maxilla, (F) 2 nd maxilla, (G) maxilliped, (H) 1 st thoracic leg, (I) 2 nd thoracic leg, (J) 3 rd thoracic leg, (K) 4 th thoracic leg and (L) 5 th and 6 th thoracic legs. 2

13 مورفولوجية الطفيلى مجدافى األرجل سينوفيلس فيريونس )كاليجيدى( مع إعادة وصف األنثى اللذان يصيبان أسماك اللوت )أرجيروزيمس ريجيس( فى مصر عال عبد الحليم أبو سمك قسم علم الحيوان كلية العلوم بدمياط جامعة المنصورة دمياط الجديدة مصر. اهتمت الدراسة الحالية بوصف تركيب جنسى الطفيلى المجدافى األرجل سينوفيلس فيريونس )نوردمان 1832( هامس 1965 مع إعادة وصف األنثى وذلك من العينات الطفيلية المجمعة من أسماك اللوت ( أرجيروزيمس ريجيس ) والمصادة من الشواطئ المصرية للبحر المتوسط. وقد أظهرت الدراسة الحالية تميز ذكر الطفيلى بصغر حجم الجسم و الزوائد وكبر حجم العقلة الصدرية الحرة و زيادة نسبة طول كل من الرأسصدر و البطن إلى الطول الكلى للجسم و باختالف شكل و تركيب األرجل الصدرية الثالثة و الخامسة و السادسة مقارنة بمثيالتها فى األنثى. وقد دعمت الدراسة الحالية الفصل التصنيفى بين أنواع جنس سينوفيلس وأنواع أقرب جنس مماثل له و المسمى كاليجيس على أساس وجود أثرى لصفيحة قصية مشقوقة و الوضع المائل للرأسصدر على المحور الطولى للجسم و التى يمكن إضافتهما إلى الصفات التصنيفية األصلية والتى صنف على أساسها جنس سينوفيلس سابقا. و أيضا أظهرت الدراسة الحالية أن أجزاء فم الطفيلى سينوفيلس فيريونس تتكون من نفس األجزاء الرئيسية والتى تميز أفراد الفصيلة الكاليجيدية. و أن وجود الشعيرات الكثيفة الشبيهة باألشواك والتى تغطى الحافة الجانبية الخارجية للرأسصدر تشير إلى احتمال قيامها بدور مهم أثناء اتصال الطفيلى بعائله. كما أدى التسجيل الجديد لمكان معيشة الطفيلى وعائله خالل الدراسة الحالية القتراح أن ارتفاع نسبة الملوثات فى دلتا نهر النيل خالل الخمسين عاما الماضية هو السبب الرئيسى لتغير توزيع عائل الطفيلى وبيئة وجوده عن المرصودة بواسطة العالم هامس فى الوصف األصلى للطفيلى عام 1957.

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17 Table (1): Measurements (average maximum length X average maximum width in µm) of the appendages of the parasitic copepod, Sciaenophilus pharaonis (Nordmann, 1832) Humes, Appendages Male Female First antenna Second antenna Postantennal process Mouth tube Postoral process First maxilla Second maxilla Maxilliped First thoracic leg Second thoracic leg Third thoracic leg Fourth thoracic leg Fifth and sixth thoracic legs 125 x x x x x x x x x x x x x x x x x x x x x x x x x x 3