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Psammonema gen.n. and Pseudochromadora Daday, 1889 (Nematoda, Desmodoridae) from sandy sediments of Gazi, Kenya PDF

29 Pages·1995·7.7 MB·English
by  VerscheldeD
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Preview Psammonema gen.n. and Pseudochromadora Daday, 1889 (Nematoda, Desmodoridae) from sandy sediments of Gazi, Kenya

BULLETIN DE L'INSTITUT ROYAL DES SCIENCES NATURELLES DE BELGIQUE, BIOLOGIE, 65: I I-39, 1995 BULLETIN VAN HET KONINKLIJK BELGISCH INSTITUUT VOOR NATUURWETENSCHAPPEN, BIOLOGIE, 65: 11-39,'I995 Psammonema gen.n. and Pseudochromadora DADAY, 1889 (Nematoda, Desmodoridae) from sandy sediments of Gazi, Kenya by Dominick VERSCHELDE & Magda VINCX Abstract Psammonema ovisetosum gen. et sp.n. and Pseudochromadora coomansi sp.n. were found in the Three new species (Psammonema ovisetosum gen. et sp.n., vicinity of Sonneratia alba trees, dwelling together with Pseudochromadora coomansi sp.n. and Pseudochromadora buc many other nematode species of 85 different genera. cobulbosa sp.n.; including all juvenile stages) belonging to a Pseudochromadora buccobulbosa sp.n. was found between known and to a new genus of the family Desmodoridae Bruguiera gymnorrhiza and Sonneratia alba trees, together (Nematoda, Desmodoroidea) were found in sandy sediments of with other nematode species of 34 different genera. the intertidal zone in front of the estuarine mangroves of Gazi, Kenya. Psammonema gen.n. differs from Pseudochromadora DADAY, 1889 in shape and number of somatic setae in Material and Methods pharyngeal region, in position and shape of lateral alae, and in the anterior position of the amphids on the head capsule. Com Benthic samples were taken (by D. VERSCHELDE) using ments are given on the ecto-symbiotic organisms, feeding habits a core of 3.5 em diameter which is pushed into the sedi of the species and on the ontogenetic transformations of some ment down to 20 em depth. Samples were fixed with a morphological characters. Key words: Marine Nematodes, Desmodoridae, systematics. hot (70°C) 4% formalin-seawater solution. Nematodes were transferred to pure glycerine by the method of SEINHORST (1959). Resume Drawing were made with the aid of a camera Iucida on a LEITZ DIALUX 20EB microscope. Trois especes (Psammonema ovisetosum gen. et sp.n., Pseudo Scanning Electron Microscope pictures were taken from chromadora coomansi sp.n. et Pseudochromadora buccobulbosa formalin fixed animals, transferred in OsO4 , dehydrated, sp.n.) d'un genre connu et d'un genre nouveau de Ia famille dried, and coated with 20-25 nm of gold (type of SEM: Desmodoridae ont ete trouvees dans les sables de Gazi, Kenya. JEOL JSM 840). Psammonema gen.n. differe de Pseudochromadora DADA Y, 1889 Type specimens are deposited in the collection of the par Ia forme et le nombre de sois somatiques dans Ia region Koninklijk Belgisch Instistuut voor Natuurwetenschap pharyngienne, par Ia position et en forme des ailes laterales, et pen (KBIN) of Brussels (Belgium), of the Museum par Ia position anterieure des amphides sur Ia capsule cephali que. La presence d'ectosymbiotes et leurs importance comme national d'Histoire Naturelle (MNHN) of Paris (France), source nutritionelle, ainsi que les transformations ontogeneti of th~ British Museum of Natural History (BMNH) of ques de certain characteres morphologiques sont commentariees. London (Great Britain), and of the Zoology Institute Mots-clefs: Nematodes marins, Desmodoridae, systematique. (ZIRUG) and Marine Biology Section (MBRUG) of the University of Gent (Belgium). Introduction Abbreviations In July and August of 1989, samples were taken in an a: body length divided by maximum body diameter; a(ar): estuarine mangrove system of the Gazi Creek (about 50 body length divided by body diameter measured anterior km south of Mombasa, Kenya). In these sediments, total to the region of the reproductive system; abd: anal body meiofauna densities vary between 1976 and 6707 diameter; amp h%: diameter of the amp hid as a percen individuals 10 cm·2 of which 53.5% to 95.1% are tage of the corresponding head diameter; a w: amphidial nematodes (VANHOVE, S. et al., 1992). Many of those width; b: body length divided by pharyngeal length; bdcs: nematodes are representatives of the Desmodoroidea, a body diameter at level of the cephalic setae; bdnr: body group which often flourishes in the intertidal, coarse diameter at level of nerve ring; c: body length divided by (coral) sandy sediments of tropical beaches. tail length; cs: length of cephalic setae; da: distance from 12 D. VERSCHELDE & M. VINCX anterior to anus; des: distance from anterior edge to females. Amphids are located anteriorly on the head cephalic setae; dnr: distance from anterior edge to nerve capsule (anterior edge of the amphid touches the anterior ring; dv: distance from anterior to vulva; gub: length of edge of the head capsule), when the amphids are open gubernaculum measured along the arc; hw; head width; loop-shaped they can cover the whole length of the head L: body length; mbd: maximum body diameter; mbdph: capsule. maximum body diameter at level of the pharynx; ph: Buccal cavity with a crown of denticles, a large strong pharyngeal length ; spic: length of spicules measured along dorsal tooth and two small subventral teeth. Muscular the arc; t: tail length; tmr: length of non-annulated tail pharynx with (tripartite) slightly prolonged terminal bulb; end; V: position of vulva as a percentage of the total body thin lumen cuticle, bulb without real cuticular valves. length from anterior. Male reproductive system monarchic, arched spicules and conspicuous gubernaculum. Female reproductive system didelphic, amphidelphic with ret1ected ovaries; brood pro Descriptions tection can occur. Familia DESMODORIDAE FILIPJEV, 1922 Differential diagnosis Genus Psammonema gen.n. Psammonema gen.n. is closely related to Pseudochro madora DADAY, 1889 and Croconema COBB, 1920. Psam monema gen.n. differs from Pseudochromadora in position TYPE SPECIES and shape of the lateral alae (in Pseudochromadora the beginning of the broader lateral alae is located posterior Psammonema ovisetosum gen. et sp.n. to the pharynx; also in most of its species, body annuli interdigitate at level of the lateral alae), in the anterior position of the amphids on the head capsule (compared ETYMOLOGY to midway or posterior position in Pseudochromadora), in the presence of denticles in the buccal cavity (none in = = From Greek: psammos sand, nema thread (neuter) Pseudochromadora), in the fine cuticular pharyngeal lumen (thick lumen cuticle with conspicuous valves in the terminal bulb in Pseudochromadora), in the prolonged DIAGNOSIS tripartite pharyngeal endbulb (bipartite with strong and conspicuous valves in Pseudochromadora) and in the dif Cylindrical body with distinct head capsule and conical ferent types of somatic setae in females (no discrimina tail. Numerous fine body annuli, with a multi-layered cuti tion into different setae in Pseudochromadora). cle. Fine lateral alae present, extending from the level of Psammonema gen.n. differs from Croconema in the the first third of the pharynx to the anal region; they are presence of lateral alae (absent in Croconema), and in formed by the local lateral raising of each annule, without absence (or few additional setae) of subcephalic setae interdigitations among these annuli. Slender, long somatic (compared to many in Croconema). setae in eight longitudinal rows in the pharyngeal region, in six rows along the rest of the body. Females can have different kinds of somatic setae: in the last third of the Psammonema ovisetosum gen. et sp.n. body, setae are firm and thorn-shaped; when brood pro (Fig. 1, 2; Plate 1-3; Table I, 2) tection occurs, the ventro-lateral setae of the mid-thirci of the body are prolonged to help hold the eggs. TYPE SPECIMENS Thick head capsule with well set-off labial region: the labial region sits as a helmet on the rest (main part) of Seven males, thirteen females, fourteen juveniles. the head capsule. Six inner and six outer labial setae Holotype male: slide RIT 466 (KBIN) located in the labial region. Four cephalic setae located Para types: allotype female: slide RIT 467 (KBIN). Other on the head capsule at the level of the anterior half of para types: slides RIT 466-467 (KBIN; 1 et, 1 9 , 11), the amphids. No subcephalic setae; however, in some 1995.127-128 (BMNH; let, 19), BN 268 (MNHN; 5J), specimens (two to four) 'additional setae' (Ergang 3821-3822 (ZIRUG; I et, 59 9 ), 10280-10281 (MBRUG; zungsborsten, LORENZEN (1973); soies additionnelles, DECRAEMER & GOURBAULT (1990); additional (sub 1C f' 2 9 9 ). cephalic) setae, VERSCHELDE & VINCX (1994)) are pre sent on the head capsule, located just at the posterior edge TYPE LOCALITY of the head capsule (or at the transition to the first body annule), these are not regarded to be real subcephalic setae Kenya, Gazi (09/08/1989): core sample (upper few em) because of their irregular presence and appearance. Sex taken of the coarse coral sands of the right front tip of ual dimorphism in shape of the amphids: open loop the sandbank, in the pits of the 'pits and bumps area', shaped in males, cryptospiral to closed loop-shaped in in the mouth of the Gazi Creek river. ••I 'I Psammonema gen.n. and Pseudochromadora DADAY, 1889 13 Table 1: Psammonema ovisetosum gen. et sp.n. (measurements in ,urn) Hoi. a Para a All. 9 Par9 9 n=6 n=7 mm max avg min max avg L 910 967 1039 1003 1063 861 1106 986 cs 4 5 7 6 5 4 6 5 des 10 5 9 7 8 4 10 8 amph % 37 36 44 40 36 36 45 41 aw 9 10 12 11 10 9 11 10 mbdar 42 41 44 43 dnr 76 73 82 79 92 74 88 79 ph 158 156 163 159 182 154 178 163 mbd ph 39 42 44 43 46 43 48 45 mbd 38 41 45 43 84 64 90 81 bdnr 36 37 40 39 41 37 41 39 bdcs 23 22 26 24 26 20 27 24 spic 48 46 52 50 gub 23 23 30 25 dv 805 672 839 758 v 76 75 83 77 da 820 872 928 900 951 767 989 882 abd 32 32 36 34 27 24 29 26 t 93 98 111 104 111 93 114 105 tmr 13 8 12 10 18 17 19 18 a 23.9 22.6 24.5 23.5 12.7 10.9 14.4 12.3 b 5.8 6 6.7 6.3 5.8 5.5 7.1 6.1 c 9.8 9.4 10.1 9.7 9.6 8.8 9.8 9.4 a(ar) 25.3 19.6 27 23.2 ETYMOLOGY annule posterior to the head capsule, as far as the region of the spicules (the alae fade out anterior to the cloaca); ovisetosum refers to the fact that the eggs are attached to they consist of a lateral raising of each body annule, but long somatic setae. without interdigitations of these annuli at the level of the lateral alae. Somatic setae in eight longitudinal rows in the pharyngeal region, in six rows further along the body: MEASUREMENTS Long, slender somatic setae most of the time alternating with tiny ones (which are not higher than the thickness Table I & 2. of the cuticle; Fig. 1A ). In the posterior body region (last third), the ventro-lateral row of somatic setae of each side splits in two (Plate lA,F) close rows: the more ventrally DESCRIPTION located setae are long, strong and firm (ten to fifteen setae oriented in a way one would expect of the supporting setae Males of species of the family Epsilonematidae; here they pro (Fig. 1; Plate 1). Cylindrical body with distinct head cap bably render support during copulation); the more lateral sule and conical tail (Fig. lB, Plate lA). Numerous, setae are short and blunt (hard to distinguish). In the same slender and clear body annuli with a multi-layered cuti region there are no long ventral somatic setae but instead cle. Slender lateral alae extending from about the 30th there are ten short spine-like setae ('pre-cloacal sup- I I 14 D. VERSCHELDE & M. VINCX ~~ so 1-lffi Fig. 1. - Psammonema ovisetosum gen. et sp.n. - A: Holotype male ( 0' 1), pharyngeal region; B: 0' 1, habitus; C: 0' 1, head cap sule; D: Para type male ( 0' z), left view on head capsule; E: 0' 2, right view on buccal cavity; F: Para type male ( 0' 3), spicule and gubernaculum; G: 0'1, tail; H: 111, head capsule; I: 111, buccal cavity; J: 111, habitus. '' Psammonema gen.n. and Pseudochromadora DADAY, 1889 15 Table 2: Psammonema ovisetosum gen. et sp.n. (measurements in .urn) lrv lm Jll n=7 n=2 n=2 mm max avg L 843 989 880 692 800 503 562 cs 4 6 5 4 6 3 5 des 4 7 5 6 7 6 5 amph% 36 46 42 39 47 42 46 aw 8 10 9 7 9 7 7 hw 21 24 22 18 19 17 15 dnr 66 74 70 56 73 59 57 ph 134 144 141 120 143 Ill Ill mbdph 39 44 42 36 39 29 32 mbd 40 57 48 35 37 27 31 bdnr 37 42 39 32 34 28 29 bdcs 20 24 22 18 20 18 17 da 742 889 782 598 700 429 476 abd 27 36 30 24 26 19 20 t 88 108 98 92 99 73 86 tmr 14 19 17 17 20 17 17 a 16 22 18 20 22 19 18 b 5.9 6.9 6.3 5.8 5.6 4.5 5.1 c 7.9 10 9 7.5 8.1 6.9 7.7 plements'; Fig. 1B ,G). The last pair oflatero-ventral 'sup anterior half of the amphids, at the transition of the nar porting' somatic setae is followed by a pair of short, firm rower anterior and wider mid of the second region of the pre-cloacal setae (Fig. lG). Following on these, there are head capsule (Fig. I C,D). Large open loop-shaped fovea eight pairs of short and strong latera-ventral somatic setae amphidialis extending along the entire length of the on the tail. At the level of the spicules there is an extra second. region of the head capsule, often filled by the pair of firm lateral somatic setae, which is also followed corpus gelatum (Plate IB,D). The first small somatic setae by seven or eight pairs laterally on the tail (Fig. 1G ). In just behind the head capsule, can be shifted anteriorly into total the tail shows seven longitudinal rows of somatic the interannual space between head capsule and first body setae: a pair of latero-ventral rows of firm somatic setae, annule or even onto the posterior edge of the head cap a pair of lateral rows of longer firm setae, a pair of dorso sule, so giving the impression that some specimens have lateral rows of small setae and a single dorsal row of long two to four 'additional setae' but as they do not occur · and slender setae. in all specimens and show the same position as the follow Head capsule (Fig. IC,D; Plate IB,D,E) consists of two ing somatic setae in the pharyngeal region, thGy are not regions: the labial region with its six internal and six exter regarded to be real subcephalic setae and so not typical nallabial sensillae, 'sits' as a helmet on the main (posterior for the genus (as presence and number of subcephalic setae or second) region of the head capsule which carries the often is a genus character). The holotype male has two four cephalic setae and the amphids. S.E.M. pictures single (i.e. not paired) small latero-ventral spines reveal the presence of a crown of fringes around the mouth posteriorly on the left side of the head capsule (Fig. 1C ). at the level of the internal labial setae (not clear with light Stoma with a crown cheilorhabdia in the cheilostome; a microscope; Plate 1B ). The extra thick inner layer of the circle of tiny denticles, a large and strong dorsal tooth main region of the head capsule is ornamented with and two small subventral teeth in the esophastome (Fig. numerous pores (vacuoles; Fig. 1C ,D) which do not show IA,E). Cylindrical pharynx with slightly prolonged tripar superficially (Plate 1E ). Four cephalic setae located at the tite, muscular endbulb (Fig. lA); lumen cuticle thin, II 16 D. VERSCHELDE & M. VINCX sometimes somewhat more pronounced in the endbulb. somatic setae. Ecto-sy~biotic organisms (see 'Mor The two partitions are clear in the endbulb, but not in phology') can occur along the body surface, when pre its lumen cuticle. sent most of them are located in the pharyngeal region. Reproductive system monarchic. Long testis located at Head capsule as in males (Fig. 2A,D; Plate 2B,D); six the left side of and also ventrally to the intestine. Long inner and six slightly smaller outer labial setae on the vas deferens (Fig. I B). Spicules arcuate, thickly helmet-shaped anterior part, crown of fringes at the level cuticularized with beak-shaped capitulum and clear of the inner labial setae (Plate 3D); four cephalic setae velum; gubernaculum with strange lateral parts which located just anterior to or at the mid-level of the amphids, stretch out around the spicules (Fig. I F). Ten to fourteen cephalic setae are hollow and are open distally with a pore ventral pre-cloacal supplements (spine-shaped setae; Fig. (Plate 2D); large cryptospiral to closed loop-shaped (sex IB,G). ual dimorphism; Fig. 2D, 2A) fovea amphidialis located Caudal glands extending as far as the gubernaculum or at the anterior edge of the main region of the head cap spicules; valve in spinneret clear (Fig. IG). Tail with seven sule (Plate 2B); head capsule ornamented with numerous rows of somatic setae and short non-annulated tail end; pores in the deeper layers of the cuticle. As in males, in on S.E.M. pictures (Plate IC) a few inconspicuous, tiny some specimens the first somatic setae can be shifted for pores are visible on the non-annulated tail end, these are ward onto the posterior edge of the head capsule resulting not clearly seen by means of the light microscope; a pair in four 'additional' setae, two ventra-ventrally and two of latero-dorsal short somatic setae is present just dorsa-dorsally. posterior to the last tail annule. Stoma with crown of cheilorhabdia, followed by a pro minent dorsal tooth (6.um), two small (l-2.um) subventral teeth and a circle of denticles (Fig 2C,E). Pharynx with Females muscular, cylindrical corpus and prolonged, tripartite end (Fig. 2; Plate 2, 3). Body cylindrical with enlarged bulb (Fig. 2C); thin lumen cuticle. Broad cardia. posterior region in which the reproductive system is Slit-like vulva (Plate 3A) located in the posterior body located; slender conical tail (Fig. 2B,G; Plate 2A, 3C). region (V=75-83%). Short vagina vera thickly Body cuticle with numerous, slender annuli and lateral cuticularized, provided with a small sphincter muscle; alae (Plate 3B). Lateral alae extend from about the 40th longer vagina uterina also with thick cuticle and large annule posterior to the head capsule as far as the enlarged sphincter muscle. Reproductive system located within the body region of the reproductive system (at the level of enlarged posterior body region; didelphic, amphidelphic the antepudendum) where it is interrupted, posterior to with reflected ovaries; in some specimens the antepuden the vulva (at level ofpostpudendum) it turns up again and dum is located at the right side of the intestine, postpuden stops anterior to the anus (Fig. 2B,G; Plate 3C). In a few dum at the left; in other specimens both branches are specimens, this second part of the lateral alae, posterior located at the left of the intestine; uterus is situated ven to the vulva, is not present. trally to the intestine. Sperm cells present, located distally Somatic setae arranged in eight longitudinal rows in the and ventrally against the uterus wall, probably incor pharyngeal region, in seven rows in the region posterior porated within it. Eggs of different developing stages are to the pharynx and anterior to the enlarged body region, attached in two latera-ventral rows to the mid body region in eight rows at the level of the enlarged body region, and by means of special setae (Fig. 2B; Plate 2E): brood pro in four rows on the tail. There are three different types tection, a phenomenon where females carry their eggs of somatic setae in females: (1) slender 'normal' somatic along after they have left the reproductive system. Females setae (9-14.um long, l.um wide; Fig. 2C) alternating with can carry up to ten eggs. The eggs measure up to 49-53.um tiny ones in the pharyngeal region, arranged in a ventra in length and 43-44.um in width. ventral pair, a ventro-lateral pair, a dorso-lateral and Slender conical tail with only few slender somatic setae. dorsa-dorsal pair of longitudinal rows; (2) posterior to Caudal glands extend as far as the intestine (Fig. 2G). the pharyngeal region and anterior to the enlarged body Valve in spinneret clear. Non-annulated tail end with a region the setae of the two ventro-lateral rows and single pair of latera-dorsal setae just posterior to the last tail ventral row are very long and firm (32-36.um long, 2-4.um annul e. wide; Fig. 2B; Plate 2E) and are specialised in holding the eggs attached to the female's ventral body side as a Juveniles kind of brood-protection; the two dorso-dorsal rows and (Fig. lH-1, 2F). All four juvenile stages were found. two dorso-lateral rows show 'normal' somatic setae; (3) the third kind of somatic setae is located in the enlarged posterior body region, these are strong thorn-like setae Fourth stage juveniles (13-18.um long (ave 15), 2-4.um wide (ave 4); Fig. 2B,G; General body shape, body annuli and shape of somatic Plate 2C,F) arranged in two dorso-dorsal rows, two dorso setae similar to males; head capsule and fovea amphidialis lateral rows, two ventro-lateral and two ventra-ventral similar to females; long conical tail. longitudinal rows; between vulva and anus these last two Lateral alae present, extending from about mid-way the rows become a single row again. On the tail there are two pharynx to about the twentieth annule (or further) ventro-lateral and two dorso-lateral rows of short, slim posterior to the anus. Somatic setae in six longitudinal I I Psammonema gen.n. and Pseudochromadora DADAY , 1889 17 A C-F so llffi B,Gl so j.lffi Fig. 2. - Psammonema ovisetosum gen. et sp.n. - A: Allotype female ( 9 1), head capsule; B: 9 1, habitus; C: 9 1, pharyngeal region; D: Para type female ( 9 :J, head capsule; E: 9 2, buccal cavity; F: Egg with J 1, attached to 9 1; G: Para type female ( 9 3), reproductive system ( 9 3: also used for S.E.M. pictures). I I 18 D. VERSCHELDE & M. VINCX rows, in four on the tail; a pair of latero-dorsal small Shape of head capsule as in J111; cephalic setae located somatic setae on the non-annulated tail end. posterior to the mid level of the fovea amphidialis. Large Head capsule, labial sensillae, position of cephalic setae, cryptospiral amphids (Fig. 1H ) located anteriorly on the shape and position of the fovea amphidialis similar to head capsule. females. Buccal cavity as in adults. Long cylindrical Buccal cavity as in adults. Long cylindrical pharynx with pharynx with prolonged muscular tripartite endbulb, muscular, not prolonged, bipartite endbulb. lumen cuticle thin; the two partitions are clear in the end Genital primordium consists out of two round cells. bulb itself but not in its lumen cuticle. Male reproductive system of early J y's is observed as a 1 slender string of cells extending from the rectum to the First stage juveniles anterior half of the body where the string is broader and First stage juveniles were only found inside eggs, which germ cells (spermatogonia) are visible. Spicules and guber are attached to the female body; so only few mor naculum not present, but the cells which will form them phological features are commented. are. Body with fine annuli. Somatic setae might be present (not Female reproductive system of an early J v: didelphic certain). Lateral alae not observed. 1 uteri aligned by cylindrical cells, reflected ovaries in which Head capsule present, ornamented with vacuoles; large germ cells are clearly present. Three pairs of cells align amphids. the future vagina uterina; the area where the vagina vera Buccal cavity with large dorsal tooth; rest is unclear. Long will be formed is indicated by a brownish granular cylindrical pharynx with round endbulb. pigmentation; the vaginal lumen is visible. In late J y's the adult reproductive system is completely 1 developed. Diagnosis Tail with well developed caudal gland cells, extending as Psammonema ovisetosum gen. et sp.n. is characterized by far as the rectum. Valve in spinneret clear. the combination of the following characters: shape of its head capsule with the helmet-like lip region; shape and anterior position of the amphids and the sexual dimor phism of the amphids; lateral alae which start anterior Third stage juveniles to the nerve ring in adults ..M ales are characterized by the Body shape, annuli and tail as in fourth stage juveniles. shape of their spicules and conspicuous lateral parts of Somatic setae slightly smaller than in J1v, arranged in six the gubernaculum; by the pair of latero-ventral rows of longitudinal rows. Lateral alae present, raised only in the 'supporting' setae anterior to the cloaca. Females are posterior part of the body or not at all; alae extend from characterized by three types of somatic setae; by the the level of the posterior half of the pharynx to posterior posterior position of the vulva and by the presence of a to the anus. kind of brood-protection unknown up to now, namely: Shape of the slightly shorter head capsule and position special, long setae embrace the eggs. of labial setae similar to females, head capsule ornamented with pores but less pronounced. Four cephalic setae located at or just posterior to the mid-level of the fovea Discussion amphidialis. Large cryptospiral amphids located at the Hitherto, brood protection within Desmodoridae has been anterior edge of the main head region, extending as far reported by OTT (1976) for Croconema ovigerum OTT, as the middle of the rostral length. No subcephalic setae. 1976, and by GOURBAULT & VINCX (1990) for Buccal cavity as in adults. Pharyngeal tripartite endbulb Croconema otti GOURBAULT & VINCX, 1990, and slightly shorter than in J v· 1 Pseudochromadora incubans GOURBAULT & VINCX, 1990. Genital primordium in an early, probably female, J 111 In both Croconema species, the same kind of brood pro consists out of a group of cells. In an older, male, J the 111 tection mechanism was found: a single row of eggs is genital primordium is a slender string of cells (individual attached to the lateral side of the female's body with cells not distinct) located in the posterior half of the body embryos within, which seem to have been fertilized at the extending as far as the rectum. same time. OTT (1976) suggested that the eggs are attached by the use of some adhesive substance as, quote, 'the body setae in the area where the eggs are carried Second stage juveniles neither seem to be different from the strong somatic setae (Fig. 1H -J). Cylindrical body with well set off head cap of the rest of the body, nor are special glands or pore sule and long conical tail (Fig. 11). Numerous slender structure apparent in this region', unquote. In annuli. Slender lateral alae extending from the pharyngeal Pseudochromadora incubans, the mechanism is somewhat region as far as the tail region. Somatic setae in six rows different: quote, 'a string of up to three eggs at different in the pharyngeal region; posterior to it the ventral row stages is attached to the modified prevulval region', is missing in one specimen (not present or all setae broken unquote (GOURBAULT & VINCX, 1990); again there are off?); in another specimen both dorsal and ventral row no special setae involved in the attachment of the eggs. are lacking posterior to the pharyngeal region. In Psammonema ovisetosum sp.n. we find a brood pro- '' Psammonema gen.n. and Pseudochromadora DADAY, 1889 19 tection mechanism unknown up to now, where two rows BN 268-269 (MNHN; 6 a a , 1 9 , llJ), 1995.129-131 of eggs at different developmental stages are held ventro (BMNH; 2aa,lJ), 3822 (ZIRUG; 19), 10281 laterally to the mid body region by means of special, long (MBRUG; .1 a ,31). setae. TYPE LOCALITY Genus Pseudochromadora DADA Y, 1889 Kenya, Gazi (1-8-1989). Mouth of the Gazi Creek: samples of coarse sandy sediments taken on the sandbank Pseudochromadora coomansi sp.n. in front of and on the beach behind Sonneratia bushes. (Fig 3, 4; Plate 4, 5; Table 3, 4) ETYMOLOGY TYPE SPECIMENS This species has been named in honour of Prof. Dr. A. Coomans. 29 0' 0'; 33 9 9 ; 60 JJ. Holotype male: slide RIT 468 (KBIN) MEASUREMENTS Para types: allotype female: slide RIT 469 (KBIN). Other paratypes: slides RIT 469-470 (KBIN; 4a,l09 9 ,51), See Table 3 & 4. Table 3: Pseudochromadora coomansi sp.n. (measurements in .um) Hoi. a Para a All. 9 Par<;:> 9 n=7 n=7 mm max avg mm max avg L 814 787 933 865 847 800 948 862 cs 7 4 7 6 6 4 7 5 des 5 4 7 6 8 4 8 6 amph% 32 29 33 31 27 24 30 26 aw 8 8 8 8 7 7 8 7 lpt(max) 4 4 6 5 dnr 66 54 78 69 70 61 73 68 ph 123 107 136 124 125 109 135 125 mbdph 37 37 40 39 41 37 40 39 mbd 42 38 46 42 57 43 54 49 . bdnr 33 33 37 35 36 32 36 35 bdcs 21 21 22 22 23 20 24 22 Sp!C 42 38 47 42 gub 22 23 26 24 dv 501 490 584 526 v 59 59 63 61 da 717 672 816 753 737 692 827 754 abd 30 28 32 29 23 22 25 23 98 108 134 122 112 96 122 109 tmr 24 22 29 27 28 24 31 27 a 19.4 17.9 22.3 20.4 14.9 14.8 21.5 17.9 b 6.6 6.3 8.3 7 6.8 5.9 8 6.9 c 8.3 6.7 8.2 7.1 7.6 7.4 8.8 7.9 20 D. VERSCHELDE & M. VINCX Table 4: Pseudochromadora coomansi sp.n. (measurements in ,urn) J4 J3 J2 Jl n=7 n=7 n=5 n=3 mm max avg min max avg mm max avg mm max avg L 685 890 763 564 757 662 431 633 533 251 400 332 cs 6 7 6 3 7 5 5 6 5· 3 7 5 des 4 8 6 3 7 5 2 8 5 4 6 5 amph % 23 30 26 25 31 28 23 27 25 26 28 27 aw 6 7 6 6 7 6 5 6 5 4 5 4 hw 23 26 24 19 24 22 19 25 22 14 19 16 dnr 63 79 70 59 70 64 47 63 57 50 50 50 ph 107 124 115 104 114 109 79 106 95 71 81 78 mbdph 35 42 38 32 34 33 28 33 31 20 25 23 mbd 32 43 38 26 32 30 23 29 27 15 19 17 bdnr 32 40 36 28 32 30 27 32 30 23 bdcs 18 20 19 17 19 18 14 17 16 13 14 13 da 605 782 658 478 647 568 359 557 459 201 337 274 abd 19 28 25 19 23 21 17 23 20 13 17 15 87 119 104 83 108 92 74 94 82 50 63 57 tinr 21 27 23 19 26 22 17 21 "19 12 13 13 a 17 25 20 19 27 22 19 22 20 17 22 19 b 6.1 7.4 6.7 5.3 7 6.1 5.3 6.2 5.6 3.5 4.6 4.2 c 6 8.3 7.4 6.7 8.4 7.2 5.8 7.2 6.5 5 6.3 5.7 DESCRIPTION short, very firm, broad setae. Many of these probably are connected with hypodermal gland cells, (especially the Males ventral row of somatic setae), these glands could secrete (Fig. 3; Plate 4). Robust, cylindrical body with large head a gluten on which the sometimes numerous ecto-symbiotic capsule, bent pharyngeal region (Plate 4D), and elongated organisms (Cyanobacteria or Bacteria) 'feed'. The ecto cylindrico-conical tail (Fig. 3A). Thick body cuticle with symbiotic organisms on the cuticle (when present) well developed broad body annuli (diameter = 2,um) and sometimes are so slim they could easily be mistaken for distinct interannual spaces (l-2,um). Body annuli are fine, hair-like setae. ornamented with a long, slim vacuole (visible as a long Broad, well developed head capsule (Fig. 3B,C; Plate 4A) slit, Fig. 3F); with exception of the last few tail annuli ornamented with numerous small dimples; head capsule (Fig. 3E); this ornamentation is one of the deeper layers exist out of two regions: a shorter anterior retractable of the cuticle. One pair of lateral alae is present (Fig. 3A; lip region (Fig. 3B) and a larger posterior, thickly Plate 4E). They are formed by the local raising of inter cuticularized (extra thick inner layer) region on which the digitations of the body annuli (Fig. 3F); they extend from amphids are located; the transition between the two about the 83rd body annule (counted laterally), starting regions is sometimes marked by a suture (more distinct posterior to the pharynx, as far as the level of the first in females and juveniles than in males). Six inner and six postcloacal thorns. outer labial setae located on the anterior region of the Firm, broad somatic setae (2-7 ,urn long) arranged in six head capsule; the four cephalic setae are situated at the longitudinal rows: a single dorsal row, a single ventral level of the transition (suture) between anterior and row, a dorso-lateral pair and a ventro-lateral pair. Ven posterior part of the head capsule; no subcephalic setae tral setae between copulatory thorns and cloaca are (Plate 4A). Unispiral fovea amphidialis. somewhat thorn-shaped (Plate 4E). On the tail, they are Buccal cavity with large dorsal tooth and two tiny subven arranged in four rows (no dorsal, no ventral row). Next tral teeth. Cylindrical pharynx with slightly enlarged buc to the postcloacal thorns, there is a latero-ventral pair of cal bulb and large, bipartite (one partition), muscular

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