The distribution of F-actin during the development of Diphyllobothrium dendriticum (Cestoda)

The distribution of actin filaments in all developmental stages of the tapeworm Diphyllobothrium dendriticum was studied. It is the first investigation of the placement of microfilaments during the development of a flatworm, and the results show that actin filaments, in all developmental stages, can be found in the subtegument and the flame cells. Muscle fibers possibly corresponding to the longitudinal, transversal, and dorsoventral muscles of the adult and plerocercoid were already detected in the procercoid. Concerning the adult worm, a new set of longitudinal fibers in the peripheral parts of the adult proglottid was found. The ducts of the protonephridial system and the vitellarias were seen to be surrounded by longitudinally oriented actin filaments, while the uterine ducts and the vagina were encircled by microfilaments. Prominent layers of circular muscle fibers surrounded the cirrus and the seminal vesicle, and radial fibers were also detected. Areas faintly stained with TRITC-phalloidin were found in the developing germ cells, the cells of the genital anlage, vitelline cells, the tegument, and the main nerve cords. None of these structures were autofluorescent, which is also true concerning the intensively labeled oncospheral hooks.     

Pentastomid Nymph From the Brain of a Squirrel Monkey (Saimiri sciureus). I. Morphology of the Nymph

A Pentastomid nymph of the genus Porocephalus was identified following its removal from the brain–meningeal interface of a squirrel monkey, Saimiri sciureus. It was characterized by two inner and two outer hooks adjacent to the mouth opening, the presence of accessory lobes (or spines) on the outer hooks, a vertical slit-like mouth opening surrounded by a U-shaped conformation of integument, and annulation of the body surface. Stigmata, representing the openings of integumental chloride cells, were present on the dorsum of the head and tail, on anterior aspects of annulae on the body, and on anterior and posterior edges of annulae located on the ventral surface of the tail. These openings were not present on integumental folds at the bases of the inner and outer hooks, on the dorsal aspect of the tail flap, or in the deep grooves separating annulae. Although it was not possible to determine the species, based on the number of annulae this specimen may represent P. stilesi.     

Oncospheral hook morphogenesis in the davaineid cestode Inermicapsifer madagascariensis (Davaine, 1870) Baer, 1956

The fine structural characteristics of oncospheral hook morphogenesis in the davaineid cestode Inermicapsifer madagascariensis are described. The primordia of the hooks appear in the oncoblasts of embryos in the advanced stage of development, in which there is a greatly reduced number of blastomeres that exhibit a bilaterally symmetrical pattern in their organization.

The hook primordium, adjacent to the invaginated part of the nuclear envelope, is surrounded by an abundance of free ribosomes, mitochondrial aggregations and extended Golgi regions. Simultaneously with its elongation and transformation into a blade, the hook primordium material becomes differentiated to form an electron dense cortex and a less dense, inner, crystal-like core. At the beginning of shank formation, the blade of the hook protrudes outside the oncoblast. The membrane-enclosed point of exit of the blade is surrounded by a cytoplasmic sheath which later forms a circular, septate desmosome.

With oncoblast degeneration, muscle fibres attach directly to the collar and the base of the hook.     

Atherospio guillei (Laubier and Ramos, 1974) comb. nov. (Polychaeta: Spionidae) and closest relatives

Atherospio guillei (Laubier and Ramos, 1974) comb. nov. is redescribed based on new material collected during a benthic survey in the German Bight, North Sea. Main characteristics of this species are a deeply incised prostomium, modified neurochaetae on chaetiger 5 superior to a small bundle of capillaries, branchiae fully fused to notopodial lamellae with digitiform distal process from chaetiger 7 over a limited number of succeeding chaetigers, predominately unidentate curved hooks with closely applied sheath from chaetiger 13-15 and a pygidium surrounded by several pairs of lateral cirri. Atherospio is closely related to Pygospiopsis and Pseudatherospio. Interrelationships of these genera are discussed.     

A special technique for studying haptoral sclerites of monogeneans

The marginal hooks and anchors have been digested from the haptors of the monogeneans Gyrodactylus salaris and Discocotyle sagittata. These structures then can be measured and drawn more accurately than those surrounded by haptoral tissue. The technique also facilitates the study of isolated hooks with SEM. The results of studies using this digestion technique are presented.     

Influence of Light on the Bioelectric Potential of the Bean (Phaseolus vulgaris) Hypocotyl Hook

By use of surface electrodes electropotenlial measurements were carried out on hypocotyl hooks of Phaseolus vulgaris seedlings. The hooks were illuminated with a small spot of white, blue, red or far red light. The potential changes in bean hypocotyl hooks do not show the red-far red reversible characteristics of phytochrome-mediated processes. By experimenting with inhibitors of photosynthesis we could demonstrate that the light-triggered potential changes in green bean hooks are correlated to photosynthetic electron transport phenomena. The red-light-induced transient is a depolarization, whereas blue light induces a hyperpolarization. Etiolated beans exhibit no bioelectric potential changes when subjected to red or far red irradiations. Blue light and white light induce a strong hyperpolarization in etiolated hooks cells. This transient seems to be an action potential induced by light. The action potential is influenced by inhibitors of electron transport and oxidative phosphorylation. By comparing the action spectrum of the action potential induced by light with the absorption spectra of extracted carotenoids and xanthophylls from etiolated bean hypocotyl hooks, we observed similarities.     

Acanthocephalus tahlequahensis sp. n. (Acanthocephala: Echinorhynchidae) from the the stippled darter, Etheostoma punctulatum (Agassiz), in northeastern Oklahoma.

Acanthocephalus tahlequahensis sp. n. was recovered from the intestines of 4 species of freshwater fishes, Etheostoma punctulatum, E. spectabile, Nocomis asper, and Notropis pilsbryi, collected in northeastern Oklahoma. The new species is distinguished from all other species of Acanthocephalus, except A. japonicus (Fukui and Morisita 1936) Petrochenko 1956, and A. fluviatilus Paperna 1964, by having smaller proboscis hooks. The length of the proboscis hooks for males is 27 to 38 (33) mum and for females 35 to 46 (42) mum. A. tahlequahensis is smaller than either A. japonicus or A. fluviatilis, and has about half the number of longitudinal rows of proboscis hooks of A. japonicus and half the number of proboscis hooks in each longitudinal row of A. fluviatilus. In addition to having smaller hooks. A. tahlequahensis differs from other species of Acanthocephalus parasitizing North American fishes by its smaller, spindle-shaped trunk and more hooks in each longitudinal row.     

A new genus of Dilepididae (Cestoda) of the yellowbill Ceuthmochares aereus (Cuculidae) from the Ivory Coast

Bonaia africana n. gen., n. sp. (Cestoda: Dilepididae) has been found in Ceuthmochares aereus (Aves: Cuculidae) in the Ivory Coast (West Africa). This new tapeworm is mainly characterized by its unusual rostellar hooks that are implanted irregularly and which present a variable form and length in the same rostellum. The differential diagnosis, particularly in comparison with the closely related genera Liga and Amoebotaenia, is presented: Liga possesses an atrial bundle of setae and Amoebotaenia 1 row of well built hooks with a typical blade. It is assumed that the unusual disposition of the rostellar hooks described here could be a transitional form between the 1- and 2-row patterns or a degenerate derivative of a regular arrangement.     

A new species of Onchobothriidae (Tetraphyllidea) from Chiloscyllium plagiosum (Elasmobranchii: Orectolobidae) in China

A new species of cestode, Yorkeria xiamenensis n. sp., is described from the spiral valve of Chiloscyllium plagiosum from coastal waters of Xiamen, China. It is the first record of Yorkeria in China. The new species is distinguished from all other species of Yorkeria by its possession of the following characters: the length of specimens, 15.8 mm; 63-95 proglottids; 71-85 testes per proglottid; large medial and lateral hooks in scolex; and eggs with 2 long polar filaments. The new species most closely resembles Y. parva Southwell, 1927 in the follicular vitellaria and similar ratio of lateral-to-medial hooks (1:2.15 vs. 1:2-2.5). However, Y. xiamenensis n. sp. has a longer strobila, more proglottids, a smaller ratio of pedicel to cephalic peduncle, larger hooks, more testes, and a different host.     

Chaetal arrangement and chaetogenesis of hooded hooks in Lumbrineris (Scoletoma) fragilis and Lumbrineris tetraura (Eunicida,Annelida)

As the structure and arrangement of chaetae are highly specific for annelid species and higher taxonomic entities, we assume that rather conservative information guarantees formation of specific chaetae. Each chaeta of an annelid is formed within an ectodermal invagination, and the modulation of the apical microvilli pattern of the basalmost cell of this invagination determines the structure of the chaeta. Any hypothesis of the homology of chaetae could thus be tested by examining the process of chaetal formation. Investigations into the ultrastructure and formation of hooded hooks in different capitellids and spionids revealed that these chaetae can be homologized. The hood of each of their hooded hooks is formed by elongation of two rings of microvilli peripheral to the chaetal anlage, which give rise to the inner and outer layers of the hood. The hood layers are well separated and surround an empty space. Superficially similar hooded hooks are described for certain Eunicida. Presently available cladistic analyses suggest that the hooded hooks of eunicidans evolved independently of those in Capitellidae and Spionidae. Compared with the latter two families, we therefore expected to find differences in chaetogenesis of the hooded hooks in the eunicids Lumbrineris (Scoletoma) fragilis and Lumbrineris tetraura (Lumbrineridae). This was the case. In these eunicidans, the hood was formed by the bisected apical wall of the chaetoblast right after the mid‐apical section of the chaeta had been sunk deeply into the chaetoblast during its formation. The apical wall generated a brush of microvilli that preformed the hood. Because the microvilli of the hood showed some accelerated differentiation, they soon merged with those of the slowly growing setal shaft to form the broad manubrium of the hooded hook in lumbrinerids. Our study confirms the predicted differences in chaetogenesis of the superficially similar hooded hooks of capitellids and spionids compared with those of eunicids.     

Durettechina beveridgei n. g., n. sp. (Nematoda: Seuratidae) from Antechinus spp. (Dasyuridae: Marsupialia) from Australia

Durettechina beveridgei n. g., n. sp. (Nematoda: Seuratidae) is described from Antechinus flavipes (Dasyuridae) from Victoria and New South Wales. A single female from A. bellus from the Northern Territory may also be D. beveridgei. This new genus is compared with other genera of the Echinonematinae, to which it has been assigned. The genus has a unique body armature and most closely resembles Chabaudechina, in the armature of the cephalic bulb, but has four rather than five rows of hooks, and Linstowinema, in having body hooks on the cuticle of the anterior region, but has 18–22 hooks in each row rather than 14–16. The hooks of Durettechina are also smaller and have a less complex root morphology than those of Linstowinema. Durettechina resembles Seurechina and Chabaudechina in having caudal alae into which papillae extend, but differs from both these genera in the number and arrangement of the caudal papillae, as well as in the body armature. Durettechina, is most different from Bainechina, which has neither hooks on a cephalic bulb nor body hooks on the anterior region nor caudal alae.     

Development of secondary sexual characters and their relationship to ontogeny and seasonal reproductive period in Hyphessobrycon igneus (Ostariophysi: Characiformes)

Sexual dimorphism in size, anal‐fin shape and coloration of Hyphessobrycon igneus, Characidae, were examined. Males were more frequent at larger body sizes, confirming body size as a sexually dimorphic trait. Anal‐fin shape and the colour of all fins were the same for females and juveniles, differing only in adult males. Likewise, only adult males had bony hooks on fin rays; larger and more sexually mature males had the most numerous and developed hooks and hooks were most developed in degree and number during peak reproductive periods. Fin hooks regressed in number and developmental degree after the reproductive period, but restarted development with the beginning of the new reproductive period without completely disappearing. Results show that bony hooks have a development and regression cycle related to reproductive seasonality.     

Hook selectivity as a mitigating measure in the catches of the stingray Pteroplatytrygon violacea (Bonaparte, 1832) (Elasmobranchii,Dasyatidae)

Hook selectivity, sex ratio of catches and relative abundance (Catch Per Unit Effort – CPUE) were assessed for the pelagic stingray Pteroplatytrygon violacea (Bonaparte, 1872), caught by longline gear in the southwestern Atlantic Ocean over the continental slope and adjacent oceanic area. The catches were carried out at depths of 200–4000 m by research cruises in 2002 and 2003, from Cabo Frio (22°52′S) to Laguna (28°28′S); and by hook selectivity experiments from 2004 to 2008, from Itajaí (26°54′S) to Tramandaí (29°59′S). Hook selectivity experiments indicated higher catches of stingrays with ‘J’ hooks (9/0, 10° offset) commonly used by the pelagic longline fleet than with ‘circle’ hooks (18/0, 10° offset). ‘circle’ hooks reduce the longline by‐catches of this species. Most of the stingrays caught were males (6 : 1). One female aborted mid‐term embryos at the time of capture. CPUE was highest between spring and autumn and lowest during winter.     

Linstowinema breve n. sp. (Nematoda: Seuratidae) a parasite of Antechinus agilis (Marsupialia: Dasyuridae) from Australia

A new echinonematine nematode, Linstowinema breve sp. n., from the small intestine of the dasyurid marsupial Anthechinus agilis is described. The species is distinguished from its congeners by the possession of the following suite of characters: small size; first and third row of cephalic hooks similar in size; second row larger; 13-15 rows of body hooks without undulating edges on the dilated cuticle of the oesophageal region; oesophagus terminating at the level of the 5th-7th row of body hooks; ten pairs of caudal papillae; a large pair of lateral ad-cloacal papillae extend into small lateral alae. Linstowinema larvae previously recorded from A. agilis may be the same species. A key to species of the genus linstowinema is provided.     

Five new species of Pedibothrium (Tetraphyllidea: Onchobothriidae) from the tawny nurse shark, Nebrius ferrugineus, in the Pacific Ocean

The spiral intestines of 7 Tawny nurse sharks (Nebrius ferrugineus; Rhincodontidae) from Australia and French Polynesia were examined for tapeworms. These sharks hosted 5 new species of Pedibothrium. The 5 species were prepared for light and scanning electron microscopy. Whereas 3 of the species exhibit the bipronged hooks typical of members of Pedibothrium, 1 species was found to possess tiny unipronged hooks or to lack some, or all, hooks, and all individuals of the fifth species appeared to lack bothridial hooks entirely. Nonetheless, the otherwise remarkable similarities between these species and the species of Pedibothrium bearing bipronged hooks were considered to be sufficient to justify the placement of these 2 species in this genus. All 5 species possess proglottid features typical of Pedibothrium, including a uterus that extends anteriorly only to the level of the cirrus sac and a cirrus sac that is bent anteriorly and is crossed by the vagina. All 5 species also exhibit uniloculated bothridia. Of particular note was the fact that all 5 species exhibit bladelike spinitrichs with elongated distal tips, a form of microthrix currently known only from species of Pedibothrium. As a consequence, these species were treated as possessing modified hooks or as having lost hooks. The diagnoses of Pedibothrium and Onchobothriidae were emended to include these species. Each of the 5 new species bears a strong resemblance to 1 or more species of Pedibothrium hosted by a species of rhincodontid shark other than N. ferrugineus. Much of Southwell's type and voucher material of Pedibothrium was located and used to verify the identity of Pedibothrium kerkhami and many of the hosts from which Southwell's material of Pedibothrium was collected. This material suggests that P. kerkhami parasitizes Stegostoma fasciatum and not N. ferrugineus.     

Amapacanthus amazonicus n. g., n. sp. (Acanthocephala: Diplosentidae: Allorhadinorhynchinae) from Arius passany and Anableps microleps (Pisces) at Maraca Island off northern Brazil

Amapacanthus amazonicus n. g., n. sp. is described from the intestine of Arius passany (Valenciennes) and Anableps microleps Müller. The most important diagnostic features are: a small globular proboscis armed with 6 diagonal rows of 3 stout hooks; middle hooks conspicuously stouter and larger than anterior ones; terminal hooks as long as middle hooks but straighter and more slender; a double-walled proboscis receptacle; a trunk bearing spines anteriorly; and two tubular cement glands in the males. Amapacanthus n. g. is differentiated from Allorhadinorhynchus, Golvanorhynchus and Slendrorhynchus, the other genera of the Allorhadinorhynchinae, by the presence of a globular proboscis armed with a small number (18) of hooks. A key to the species of the Allorhadinorhynchinae is presented.     

Setal Structure and Chaetogenesis in Scolelepis squamata and Malacoceros fuliginosus (Spionidae,Annelida)

In Scolelepis squamata and Malacoceros fuliginosus two alternatingly arranged transverse rows of setae are found in each ramus. These are capillary setae in all thoracic setigers, whereas in abdominal setigers they may alternate with hooded hooks. In M. fuliginosus only the abdominal neuropodia bear hooded hooks, whereas in S. squamata these setae are present in both rami in the abdomen. Here every second seta (the capillary one) degenerates before its formation is complete, leading to a single row of hooded hooks. In the transverse rows new setae are formed in a medio-lateral formative site in both species. Additionally in each ramus there exists one longitudinal row of capillaries which each possesses its own formative site. Ultrastructure and formation of the hooded hooks in S. squamata is very similar to that of hooded hooks in Capitellidae. The hood is preformed by a certain group of microvilli of the chaetoblast, which soon differentiates two layers of microvilli, raising an inner and an outer hood lamella. The hooded hooks and their arrangement are regarded as homologous characters in Spionidae and Capitellidae. This indicates a closer relationship of Spionidae with a taxon consisting of Capitellidae, Arenicolidae, Maldanidae, Oweniida, Terebellida, Sabellida, and Pogonophora.     

The statocyst of Vampyroteuthis infernalis (Mollusca: Cephalopoda)

The statocyst shows a remarkable combination of features of decapods and octopods confirming that Vampyroteuthis is a relic somewhere near the ancestor of both groups. The lining of the statocyst separates from the outer wall, forming an inner sac, filled with endolymph, surrounded by perilymph. This is the condition found in octopods, never in decapods. The macula is partly divided into a macula princeps and macula neglecta, as in decapods but never in octopods. There are numerous statoconia, but no large statolith has been seen. The crista has four parts as in decapods, but they are not sharply separated. There are numerous small anticristae, with the general form found in decapods, differentiated into pegs and hooks.
The wall of the inner sac contains numerous hair cells. These hairs protrude between the epithelial cells. The bases of the cells are drawn out into fine processes, presumably some dendritic and some axonal. There is thus a plexus of nerve fibres all over the wall, communicating with the crista nerve.
There is a very large posterior sac of unknown function, lying behind the crista. It contains only one large anticrista and the opening of Kölliker's canal, which is very large.     

Ultrastructure and formation of hooded hooks in Capitella capitata (Annelida, Capitellida)

 The hooded hooks of Capitella capitata are aligned in a transverse row inside each neuro- and notopodial rim of the last thoracic and all abdominal setigers. Each seta consists of a rostrum, a capitium, the spines of which surmount the rostrum, and a long, sigmoid shaft or manubrium, towards which rostrum and capitial spines are curved. A thin hood, complete except for a subapical opening and a short, subrostral cleft, encloses the apical portions of the seta. Generally, the tip of the rostrum extends beyond the hood. The hood consists of an outer and an inner lamella, between which is a compartment loosely filled with fibrillar material. Hooded hooks are generated at the dorsal edge of the neuropodial rim and at the ventral edge of the notopodial rim during the entire life of C. capitata. Chaetogenesis starts in a small compartment surrounded by the basal chaetoblast and four follicle cells. Initially a group of microvilli emanating from the chaetoblast preforms the rostrum. Next, stout microvilli appear adrostrally, each preforming a spine of the capitium. When both structures have been formed, the longitudinal axis of the anlage shifts, because the actin filaments inside the microvilli reorientate and initiate formation of the manubrium. During this initial phase of chaetogenesis the anlage sinks into the chaetoblast, until the latter finally enwraps the anlage, except the tip of the rostrum. The chaetoblast now generates microvilli that face the new setal structures and preform the hood. During further development the microvilli separate into two layers, an inner and an outer one. The inner layer of microvilli merges with the manubrium prior to the outer layer. Addition of setal material occurs between the bases of the microvilli and elongates the manubrium until it extends beyond the epidermal surface. The microvilli, which have continuously been withdrawn from the seta during chaetogenesis, remain in the basal section. Specific morphogenetic and structural correspondence between the hooked setae of species of Maldanomorpha, Psammodrilida and Oweniida, the uncini of species of the Sabellida, Terebellida and Pogonophora, and the hooded hooks of species of Capitellidae justify the hypothesis that all these setae are homologous. This hypothesis implies the existence of a monophyletic group consisting of all polychaetous Annelida with such setae. Accepted: 16 December 1997