Echinostoma deserticum, Kechemir & Jourdane & Mas-Coma, 2002

Kechemir, Nadia, Jourdane, Joseph & Mas-Coma, Santiago, 2002, Life cycle of a new African echinostome species reproducing by parthenogenesis, Journal of Natural History 36 (15), pp. 1777-1784 : 1778-1782

Echinostoma deserticum n. sp.

Adult (gure 1A–C; based on 14–45-day-ol d experimental worms, measurements on 30 45-day-old worms). Body 5610–15170 (9240) long and 752–3108 (1793) wide. Minute spines extending from the oral sucker to the level of the posterior part of Mehlis’ gland. Collar well developed with 37 conspicuous collar spines. Arrangement of spines: ve grouped corner spines with three oral and two aboral, ve lateral in a single row and 17 dorsal in two rows alternating. Oral sucker subterminal 164–275 (205) in diameter. Ventral sucker in anterior quarter of body 462–979 (716) in diameter. Well-developed oval pharynx. Oesophagus short, bifurcating to form two caeca which extend to posterior end of body. Lateral excretory ducts con uent in posterior quarter of the body. Ovary median, ovoid 231–880 (539)Ö241–550 (369). Oviduct with conical oocapt connecting to Laurer’s canal which opens dorsally and to the median vitelloduct. Well-evident Mehlis’ gland complex behind ovary. Vitelline follicles in lateral elds extending from median region of the acetabulum to posterior extremity of the body where they sometimes become con uent. Uterus intercaecal with numerous loops opening into genital pore. Male genital system polymorphic including individuals with two testes (rare), one testis (gure 1B) or without testes (majority) (gure 1A). Of 37 adults obtained experimentally (10 being 14-days-old and 27 being 40-days-old), testes were absent in 23 (ve being 14-days-old and 18 being 40-days-old), the others (ve being 14-days-ol d and nine being 40-days-ol d) having only one 273–550 (403) Ö130–511 (323), which is present sometimes in a pre-ovarian atypical position. Among 10 adult parasites recovered in naturally infected Arvicanthis , one possessed two testes, ve possessed one testis and four none. Cirrus sac (gure 1C) well developed, 568–990 (794) long, situated between acetabulum and caecal bifurcation, generally on the left, containing long seminal vesicle, pars prostatica and ejaculatory duct. The posterior extremity of the cirrus sac seems completely closed and no sperm is present in the seminal vesicle.

Egg and miracidium (gure 2A, B). Eggs clear and operculate, unembryonated when laid. Intra-uterin e dimensions of eggs are 58–74 (67) Ö36–46 (40). Miracidium body (about 120 Ö65) covered with epidermal cells arranged in four rows having 6, 6, 4, 2 cells from anterior to posterior end. One apical gland and two penetration glands opening at anterior end. X-shaped eye spot in the end of the rst anterior quarter. Excretory system comprises two ame cells on either side of body, two excretory ducts with two excretory pores.

Sporocyst (gure 2C, D). Sporocyst often pyriform 200–265 (228) Ö104–160 (133), always attached to blood vessel between heart ventricle and aorta of the snail host, generally containing one redia and three or four germ balls.

Redia (gure 2E, F). Second generation of rediae white and elongate 690–1600 (970) long by 173–330 (254) wide according to age. Anterior conspicuous collar. Muscular pharynx 35–67 (55) Ö30–60 (45). Saccular gut contained black granulations. Two strong locomotor appendages in equatorial zone. Often less than 10 cercariae inside. Birth pore behind muscular collar.

Cercaria (gure 3A, B). Body 228–422 (306)Ö 103–165 (133) in size. A total of 37 collar spines arranged as in adult. Oral sucker 40–59 (47) Ö45– 56 (50). Acetabulum in posterior half of body 45–67 (54) in diameter. Six penetration gland cells opening behind dorsal lip of oral sucker. Six paraoesophageal gland cells opening anteriorly through six pores arranged bilaterally in two groups of two ventral and one lateral. Granular cystogeneous cells extend from pharynx to posterior extremity of body. Pharynx 14–31 (20) Ö20–34 (25). Oesophagus consisting of seven cells, bifurcating anterior to acetabulum to form two curved caeca extending almost to posterior part of body. Excretory system consists on each side of one thin descending duct forming a loop at pharynx level and one ascending dilated duct lled with large refractile granules in anterior half of body. Latter duct arrives into anterior part of bipartite excretory vesicle. Vesicle opens into duct which passes through anterior quarter of tail, bifurcates and opens laterally via two excretory pores. Eighten pairs of ame cells. Tail 325–499 (419) long with nger like narrowing at tip 81–116 (99). Six n folds, two dorsal (one anterior, one posterior), two ventral (one anterior, one posterior) and two lateral near the end of the tail, diYcult to see. Numerous cilia on the body and the tail.

Metacercaria (gure 3C). Metacercarial cyst 142–150 (146) in diameter. Outer cyst wall 10–15 (13) thick.