Bipolar head regeneration induced by artificial amputation in Enchytraeus japonensis (Annelida, Oligochaeta)

The Enchytraeida Oligochaeta Enchytraeus japonensis propagates asexually by spontaneous autotomy. Normally, each of the 5-10 fragments derived from a single worm regenerates a head anteriorly and a tail posteriorly. Occasionally, however, a head is formed posteriorly in addition to the normal anterior head, resulting in a bipolar worm. This phenomenon prompted us to conduct a series of experiments to clarify how the head and the tail are determined during regeneration in this species. The results showed that (1) bipolar head regeneration occurred only after artificial amputation, and not by spontaneous autotomy, (2) anesthesia before amputation raised the frequency of bipolar head regeneration, and (3) an extraordinarily high proportion of artificially amputated head fragments regenerated posterior heads. Close microscopic observation of body segments showed that each trunk segment has one specific autotomic position, while the head segments anterior to the VIIth segment do not. Only the most posterior segment VII in the head has an autotomic position. Examination just after amputation found that the artificial cutting plane did not correspond to the normal autotomic position in most cases. As time passed, however, the proportion of worms whose cutting planes corresponded to the autotomic position increased. It was suspected that the fragments autotomized after the artificial amputation (corrective autotomy). This post-amputation autotomy was probably inhibited by anesthesia. The rate at which amputated fragments did not autotomize corresponded roughly to the rate of bipolar regeneration. It was hypothesized then that the head regenerated posteriorly if a fragment was not amputated at the precise autotomic position from which it regenerated without succeeding in corrective autotomy.     

Palp growth,regeneration, and longevity of the obligate hermit crab symbiont Dipolydora commensalis (Annelida: Spionidae)

Abstract. The polychaete Dipolydora commensalis is an obligate symbiont of hermit crabs and produces a burrow along the columella of the gastropod shells they inhabit. Adults of D. commensalis have short palps that they use to feed on particles dropped or brought in by the respiratory currents of hosts. To determine whether hermit crabs influence palp length, specimens of D. commensalis were isolated in glass capillary tubes and the growth of palps was measured over a 3‐week period. Palp length was also measured in worms isolated in gastropod shells with or without hermit crabs for 2 weeks. In addition, to determine whether adults of D. commensalis have regeneration capabilities like those of free‐living relatives, worms were cut at the fifth or 15th setiger and then monitored for 35 d. Worms extracted from shells and placed into capillary tubes had initial palp lengths of 1.0±0.4 mm (n=17); after isolation, palps were 40% longer (1.4±0.4 mm, n=17). Worms in gastropod shells with hermit crabs had an average palp length of 0.9±0.4 mm (n=31), whereas worms in shells without hermit crabs had palps that were 33% longer (1.2±0.5 mm, n=40). Adults of D. commensalis are capable of regeneration; 35 d after ablation at setigers 5 or 15, the average number of anterior setigers regenerated was 5 (n=15) and 9±1.3 (n=13), respectively. The average number of posterior setigers regenerated from the 15 setiger anterior fragments was 11±6 (n=10). The findings suggest that the palps (and sometimes anterior ends) of the worms are exposed during feeding and are cut during movement of the hermit crab. In the laboratory worms can live for >4 years, considerably longer than the functional life span of most gastropod shells inhabited by hermit crabs.     

Asexual reproduction in Pygospio elegans claparède (Annelida, Polychaeta) in relation to parasitism by Lepocreadium setiferoides (Miller and Northup) (Platyhelminthes, Trematoda)

Life-history theory predicts that parasitized hosts should alter their investment in reproduction in ways that maximize host reproductive success. I examined the timing of asexual reproduction (fragmentation and regeneration) in the polychaete annelid Pygospio elegans experimentally exposed to cercariae of the trematode Lepocreadium setiferoides. Consistent with adaptive host response, polychaetes that became infected by metacercariae of trematodes fragmented sooner than unexposed controls. Parasites were not directly associated with fission in that exposed polychaetes that did not become infected also fragmented earlier than controls. For specimens of P. elegans that were not exposed to trematodes, new fragments that contained original heads were larger than those that contained original tails, whereas original head and tail fragments did not differ in size for infected polychaetes. In infected specimens, metacercariae were equally represented in original head and tail fragments and were more likely to be found in whichever fragment was larger. Despite early reproduction, parasitism was still costly because populations of P. elegans exposed to parasites were smaller than controls when measured 8 weeks later and because exposure to cercariae reduced survivorship of newly divided polychaetes. Taken together, my results suggest that early fragmentation is a host response to minimize costs associated with parasitism.     

Secondary infections of Hymenolepis diminuta in mice: effects of varying worm burdens in primary and secondary infections.

In one (1 c) and six (6 c) cysticercoid primary infections of Hymenolepis diminuta in NIH (inbred) and CFLP (outbred) male mice 6 +/- 1 weeks old greater than 85% of the worms established but were rejected (destrobilated or expelled) subsequently. Rejection occurs more quickly in 6 c infections than in 1 c infections. Considerable worm growth occurs in 1 c and 6 c primary infections but worms from 6 c infections weighed less than worms from 1 c infections on all days studied. Expulsion of H. diminuta does not occur more rapidly in secondary infections than in primary infections; loss of 6 c secondary worms occurs at the same rate as 6 c primary worms but 1 c secondary worms survive longer than 1 c primary worms. Although worms are not lost more quickly in secondary than in primary infections, they are affected at an early age by the immune response which stunts their growth. Increasing the intensity of primary and secondary infections increases the severity of stunting of secondary worms. The results are discussed and it is suggested that immune responses to Hymenolepis spp. in rodents are common but that thresholds of worm numbers exist below which appreciable worm loss does not occur. Stunting due to crowding, which generally is attributed to inter-worm competition, may be in part immunologically mediated. For future immunological studies attempting to induce secondary responses to H. diminuta in mice, worm growth, not survival, is the criterion to evaluate.     

Infestation of the clam Chione fluctifraga by the burrowing worm Polydora sp. nov. in laboratory conditions

Burrowing worms that belong to Polydora spp. infest marine mollusks cultured worldwide, causing problems for production and marketing. The clam Chione fluctifraga is semi-cultured in Bahía Falsa, Baja California, NW Mexico, and some clams harbor burrowing worms. The present study was carried out to determine the identity of the worm species infesting the clam, the infesting process by cohabitation of infested and non-infested clams in aquaria with a variety of substrates (fine sand, gross sand, plastic bag used for clam culture, and aquarium without substrate) and turbulence conditions, and the occurrence of architomy phenomena in connection with infestation of the clam. The burrowing worm was considered as a nova species due to its singular limbate neurosetae and notosetae in the setiger 5, hooks in the setiger 6, eyes not present, and general pigmentation, among other characteristics. Infestation was similar in all substrates and turbulence conditions, but it was more abundant on clams previously infested than on those free of worms, showing a preferential settlement of worm infesting stages on pre-infested clams. Regeneration was observed in all segments of the worm: anterior (metastomium), medium, and posterior (prostomium); the complete regeneration time occurred in 40 days. This is the first record of architomy in a species of Polydora and this phenomenon could account for the increase of infestation intensity in pre-infested clams at the end of the study period. Infestation of clams by settling polichaete in the conditions studied, and the architomy process in this worm species, shows its great infesting capacity.     

Hymenolepis diminuta: Worm loss and worm weight loss in long-term infections of the rat

Infections of one and two Hymenolepis diminuta established in newly weaned rats continued to grow for the duration of the experiment (238 days), whereas infections of 5 worms per rat became asymptotic around Day 55 postinfection and remained at or below this level thereafter as shown by biomass and mean weight per worm measurements. Infections of 50 worms established in newly weaned rats became asymptotic around Day 28 postinfection and thereafter worms were lost from the rats. Initially the biomass fell with the loss of worms, but by Day 56 a new lower biomass persisted for the remainder of the infection period. This level was maintained, despite diminishing numbers of worms, due to the growth of surviving individuals to a weight exceeding the original weight at maturity by a factor of more than 2. Experiments using rats that were mature at the time of infection demonstrated that the same response occurred, but approximately 3 weeks earlier.     

Bromophenol accumulation and sediment contamination by the marine annelids Notomastus lobatus and Thelepus crispus

The occurrence of bromophenols in Notomastus lobatus and Thelepus crispus and associated sediment and porewater was determined. 4-Bromophenol, 2,4-dibromophenol, and 2,4,6-tribromophenol were identified in N. lobatus with the highest concentrations occurring in the anterior and posterior abdomen and substantially less in the thorax (345, 209, and 6.6 μg/ml of worm, respectively). The concentration of dibromobenzyl alcohol was highest in the tail (last 15 setigers) of T. crispus (1.02 mg/ml of worm), but did not differ among body parts as the bromophenols did in N. lobatus. Concentrations in sediments were significantly reduced from those in the worms and decreased from the inner burrow lining out to 5 cm from N. lobatus burrows. Similarly for T. crispus, concentrations of dibromobenzyl alcohol in the surrounding sediments and porewater were low and increased with proximity to the burrow. For both species, concentrations in surface sediment (upper 1 cm) did not differ from those at 6 cm depth. Several lines of evidence indicate that these compounds are produced by the worms and hence their presence in sediments is derived from the worms. The contamination of sediment by these bromophenols has important implications for the structure and activities of benthic-associated communities.     

Signification of the sexualizing substance produced by the sexualized planarians

Asexual worms of an exclusively fissiparous strain (the OH strain) of the planarian Dugesia ryukyuensis keep developing hermaphroditic reproductive organs and eventually undergo sexual reproduction instead of asexual reproduction, namely fission, if they are fed with sexually mature worms of an exclusively oviparous planarian, Bdellocephala brunnea, suggesting that the sexually mature worms has a sexualizing substance(s). The fully sexualized worms no longer need the feeding on sexual worms to maintain the sexuality. Here, we demonstrate that the sexualized worms produce enough of their own sexualizing substance similar to that contained in B. brunnea. In case of surgical ablation of the sexualized worms, the fragments with sexual organs regenerate to become sexual, while those without sexual organs, namely head fragments, regenerate to return to the asexual state. The asexual regenerants from the sexualized worms are also fully sexualized by being fed with B. brunnea. Additionally, it was reported that head region in sexually mature worms lacks the putative sexualizing substance necessary for complete sexualization (Sakurai, 1981). These results suggest that the fragments without sexual organ lack enough of an amount of the putative sexualizing substance and the sexuality is maintained by the sexualizing substance contained in the sexualized worms.     

Immunity to primary and challenge infections of Trichinella spiralis in mice: a re-examination of conventional parameters.

In young (6- to 8-week-old) NIH strain inbred mice expulsion of a primary infection of Trichinella spiralis began on day 8 and was virtually complete by day 11-5. In older mice expulsion occurred 1 or 2 days earlier. Experience of a primary infection elicited strong immunity to challenge, whether the challenge was given immediately after worm expulsion (day 14) or delayed (day 42). Challenge infections were expelled rapidly the majority of worms being lost during the first day. Immunity to challenge was elicited by low-level primary infections and was effective against large ventionally accepted parameters of immunity to T. spiralis in mice which, it is considered, are applicable only to mice with a genetically determined low-level of responsiveness to the parasite.     

Ectopic pharynxes arise by regional reorganization after anterior/posterior chimera in planarians

To elucidate the mechanisms underlying pharynx regeneration in planarians, we transplanted pieces excised from various regions of the body into the prepharyngeal or postpharyngeal region, since it has been shown that such transplantation experiments can induce ectopic pharynx formation. We confirmed the ectopic formation of pharynxes by expression of the myosin heavy chain gene specific to pharynx muscles (DjMHC-A). To investigate the cellular events after grafting, we also stained such transplanted worms by in situ hybridization using neuronal cell- and mucous producing cell-type-specific marker genes which can detect formation of brain and prepharyngeal region, respectively. When the head piece was transplanted into the tail region, ectopic formation of the head, prepharyngeal and pharynx region was observed in the postpharyngeal region anterior to the graft, while these organs were formed in the reversed polarity along the anterior-posterior (A-P) axis. Furthermore, in the tail region posterior to the graft, ectopic formation of the prepharyngeal and pharynx region was observed. In the reverse combination, when a tail piece was transplanted into the prepharyngeal region, ectopic formation of prepharyngeal and pharynx region was observed in the region between the head and the graft, and an additional ectopic pharynx was also formed in reverse polarity in the region between the graft and host pharynx. These results clearly indicated that ectopic pharynxes were formed as a consequence of the regional reorganization induced by interaction between the host and graft. Furthermore, chimeric analyses demonstrated that the cells participating in ectopic pharynx formation were not exclusively derived from the host or donor cells in the worm, suggesting that the stem cells of the host and donor may change their differentiation pattern due to altered regionality. To further investigate if regional reorganization is induced after grafting, expression of a Hox gene was analyzed in the transplanted worms by whole-mount in situ hybridization. The expression of the Hox gene along the A-P axis was apparently rearranged after grafting of the head piece into the tail region. These results suggest that grafting of the head piece may rearrange the regionality of the host tail, and that stem cells in the region newly defined as pharynx-forming may start to regenerate a pharynx.     

Diurnal migration of Echinostoma caproni (Digenea: Echinostomatidae) in ICR mice

Twenty-four female ICR mice, 12 acclimated to a 12 ∶ 12 light-dark cycle and 12 to a 12 ∶ 12 dark-light cycle for 7 days, were each infected with 10 metacercariae of Echinostoma caproni. Infected mice were maintained on their respective lighting regimes for 28 days. Six mice (3 from each group) were necropsied at 4-hr intervals beginning at 0700 hr. The small intestine was removed, opened, and the position of individual worms and worm clusters was measured to the nearest 0.1 cm. Each intestine was subsequently divided into 20 equal segments and individual worms and worm clusters were assigned to the appropriate segment based on the original measurements. All worms were found in the posterior 55% of the intestine (ileum). All posterior segments (10-20), with the exception of segment 18, harbored at least 1 worm at some time. A Monte Carlo simulation of worm abundance in segments 10-17 over all time periods indicated a random distribution, while the same analysis of segments 10-20 indicated a non-random distribution due to large numbers of worms in segment 20 and to the absence of worms in segment 18. To analyze temporal changes in worm distribution, mice were grouped by time of necropsy as follows: night (1900 and 2300 hr), morning (0300 and 0700 hr), and day (1100 and 1500 hr). During the night and morning, E. caproni was heavily concentrated in segments 10-17 and, during the day, worms were located more posteriorly, with a heavy concentration in the last segment (20).     

Inflammatory cell stimulation and wound healing in Sphaeridiotrema globulus experimentally infected mallard ducks (Anas platyrhynchos)

Thirty laboratory-reared mallard ducks (Anas platyrhynchos) were experimentally infected with Sphaeridiotrema globulus. Host cell-mediated immunity and wound healing in S. globulus infected ducks were evaluated by gross and histological examination. Establishment, location, and life span of S. globulus differed from previous reports of sphaeridiotremiasis in both naturally and experimentally infected waterfowl. No worms were recovered from the ceca, and worm migration occurred anterior to the ileo-cecal valve with greater dispersion (less worm crowding) at higher rates of infectivity. Parasite death and host lesion resolution were evident at days 8 to 10 postinfection (PI) in ducks fed a moderate dose (200 metacercariae, group A) with a 5% mean parasite recovery rate. Host death occurred at days 3 to 6 in ducks fed a high dose (550 metacercariae, group B) with a 16% mean parasite recovery rate. Mast cells increased significantly (P less than 0.005) in group A ducks from days 4 to 10 PI. Eosinophil proliferation was greater in group B than in group A on day 4 PI, but comparatively fewer eosinophils were identifiable in group B ducks on day 6 PI.     

Morphological characterization of the asexual reproduction in the acorn worm Balanoglossus simodensis

The acorn worm Balanoglossus simodensis reproduces asexually by fragmentation and subsequent regeneration from the body fragments. We examined the morphogenesis of its asexual reproduction. At first, we collected asexually reproducing specimens and observed their morphogenesis. Then, we succeeded in inducing the asexual reproduction artificially by cutting the worm at the end of the genital region. The process of morphogenesis is completely the same between naturally collected and artificially induced specimens. The stages during morphogenesis were established on the basis of the external features of the asexually reproducing fragments. The internal features of the fragments were also examined at each stage. In a separate phase of the study, the capacity for regeneration of some body parts was also examined by dividing intact worms into about 10 fragments. Although the capacity for regeneration varied among the different body parts, some fragments regenerated into complete individuals in 1 month. The process of regeneration was the same as that in the asexually produced fragments.     

Experimental infections with Cooperia oncophora (Railliet, 1918) in calves. Results of single infections with two graded dose levels of larvae.

Two experiments were carried out in which calves reared parasite-free were infected with a single dose of 3rd-stage larvae of Cooperia oncophora. In the first experiment the calves received 20 000 or 200 000 infective larvae and they were autopsied 28 or 56 days after the infection. In the second experiment the doses were the same but the animals were killed 14, 84 or 140 days after infection. If a dose of 20 000 was given, clinical signs were never observed, while at a dose level of 200 000 the weight gain was less on 56 and 84 days after the infection compared with the low-infected groups or the control animals. After 170 days the differences in weight gain were compensated. Faecal egg output was higher in the 200 000 groups only in the first period of patency, thereafter the calves in the 20 000 groups produced more. No obvious differences between the two infection levels were observed with regard to the haematological data. In the low-infected groups worm counts were only slightly lower when the results after 28 days were compared with those after 56 days. Also, the worm numbers after 14 days were almost equal to those after 84 days, while at 140 days 1 animal still had the same number, the other one had lost its worm burden. In the high-infected groups the worm loss was much quicker. After 28 days a great part of the population had already been lost. Obviously, at the 200 000 level the reaction of the host against the parasite was much stronger. Adult worms were expelled at a higher rate than early 4th-larval stages. In the first experiment worm measurements revealed differences between the length of females, males and spicules of males, these being significantly longer in the low-infected groups. Analysis of the distribution of worms over the small intestine showed that in the low-infected groups worms were mainly restricted to the first 6 metres. In the high-infected groups the worm population was distributed more evenly over the whole small intestine.     

Scanning electron microscopic observations of Thelazia callipaeda from human

Four females and a male nematode isolated from 2 patients who visited eye clinics in Seoul were identified as Thelazia callipaeda and their ultrastructures were observed by scanning electron microscopy (SEM). General features of the worms were slender and attenuated at both ends. Vaginal opening was located at 0.27 mm from the anterior end, and in front of the esophago-intestinal junction. In the body cuticle transverse striations varied characteristically through the body. The number of cuticular transverse striations was 400-650/mm at head portion, 250/mm at middle portion and 300-350/mm at tail portion. The SEM observation of the mouth part of the females showed 6 cord-like cuticular thickenings in hexagonal arrangement and an amphid was observed. A lateral line, a vaginal opening, a pair of phasmids, and an anus were identified in the body portion. A pair of papillae and 6 cord-like cuticular thickenings were on the mouth part of the male. It was difficult to observe structures at the tail of the male except wrinkle-like structures. Most of the larvae isolated from the uterus of a female worm were sheathed and thus cuticular striations were not seen. Others were un-sheathed and revealed cuticular striations. The oval membrane which encysted sheathed larvae was also observed. These are the 18th and 19th record of human thelaziasis in Korea as the literature are concerned.     

The length of Ostertagia ostertagi in populations of uniform age

Michel J. F., Lancaster M. B. and Hong C. 1978. The length of Ostertagia ostertagi in populations of uniform age. International Journal for Parasitology8: 437–441. The conclusion that, in calves exposed to daily infection with larvae of Ostertagia ostertagi, adult worms are constantly lost and replaced was based, in part, on the observation that the length of the worms present decreased with time. The underlying assumption that worms do not shrink was examined in an experiment in which groups of calves received 8300, 25,000 and 75,000 larvae respectively in a single occasion and were killed at various times between the 20th and 132nd day thereafter.The length of the worms was inversely related to the initial worm burden but as worm burdens declined the worms did not grow. Instead, in the groups that received 25,000 and 75,000 larvae, decreases in worm length of 7% and 8% respectively were seen when most of the worms had been lost. Although it appears very probable that this was due to the more rapid loss of large worms than of small, the point could not be conclusively demonstrated.     

Biological variation between two Brazilian geographical isolates of Echinostoma paraensei

The biological behaviour and morphometric data from two allopatric isolates of Echinostoma paraensei (Rio Bonito - RB and Sumidouro - SU) collected from naturally infected Nectomys squamipes from two secluded Atlantic Forest fragments were studied. Mice that had been experimentally infected with ten encysted metacercariae of each isolate were monitored weekly in two trials to analyse worm burden and the kinetics of worm distribution along the intestine. The total number of uterine eggs, wet weights and measurements of the worms and body, acetabulum, testes and ovaries were also analysed. The RB isolate showed a higher worm burden, 7.7+/-0.8, and a longer life span, 16 weeks, compared to a worm burden of 5.8+/-1.1 and life span of 9 weeks for the SU isolate. Worms of the RB isolate were clustered in the duodenum and in the bile duct while the SU isolate worms were dispersed along the small intestine of infected mice. Both isolates developed similarly as regards morphometric data and wet weight, although the total number of uterine eggs was greater in RB. The degree of intraspecific variation observed in the worm distribution along the intestine, worm burden and life span raises questions regarding the use of these criteria for species differentiation. These findings suggest that variation in biological parameters found between the E. paraensei isolates could result from geographical isolation and, in particular, the environmental conditions of transmission. Further studies on E. paraensei polulations from different forest fragments will contribute towards an understanding of the speciation of this parasite.