Invertebrate Biology, Volume 120, No. 2

Contents and Abstracts
© 2001 American Microscopical Society, Inc.

HEADER ILLUSTRATION: New Zealand glowworms, the larvae of Arachnocampa luminosa, snare prey in sticky droplets secreted along hanging "fishing lines", silk threads suspended from a web, in caves or niches in the bush where they are protected from wind. The larva, inconspicuous by day, is brilliantly bioluminescent, and well over a century ago, it was suggested that the light attracts insect prey. This has been assumed to be so ever since. Now, Broadley & Stringer (pp 170-177), in a series of ingenious experiments using transparent adhesive traps, have confirmed this hypothesis and learned more about the food habits of these "literally" attractive dipterans. (Photo by Ralph Buchsbaum)


Abstracts for all articles in this issue are presented below.
Individual abstracts can also be accessed directly by clicking on the highlighted titles here:

Food plaquette digestion in the ciliated protozoan Hyalophysa chattoni
Stephen C. Landers, Rex A. Treadaway, Jason W. Johnson, and Rebecca N. Luckie. pp 97-103

Temperate and tropical algal-sea anemone symbioses
Gisèle Muller-Parker and Simon K. Davy. pp 104-123

Macrodasyida (Gastrotricha): a cladistic analysis of morphology
Rick Hochberg and Marianne K. Litvaitis. pp 124-135

A carnivorous bdelloid rotifer, Abrochtha carnivora n.sp.
Claudia Ricci, Giulio Melone, and Elizabeth J. Walsh. pp 136-141

Influence of lowered salinity and elevated cadmium on the survival and metamorphosis of trochophores in Capitella sp. I.
Jan A. Pechenik, Richelle Berard, Dara Daniels, Timothy R. Gleason, and Denise Champlin. pp 142-148

Partial characterization of the secretory material from the dorsal bodies in the snail Helisoma duryi (Mollusca: Pulmonata), and its effects on reproduction
Spencer T. Mukai, Colin G.H. Steel, and A. Saber M. Saleuddin. pp 149-161

Apical antennal sensilla in nymphs of Libellula depressa (Odonata: Libellulidae)
Elda Gaino and Manuela Rebora. pp 162-169

Prey attraction by larvae of the New Zealand glowworm, Arachnocampa luminosa (Diptera: Mycetophilidae)
R. Adam Broadley and Ian A.N. Stringer. pp 170-177

Induced inflammatory process in the sea urchin Lytechinus variegatus
Maria B.B.C.D. Mangiaterra and José R.M.C. Silva. pp 178-184

The peripheral nervous system of an ascidian, Botryllus schlosseri, as revealed by cholinesterase activity
Paolo Burighel, Marina Sorrentino, Giovanna Zaniolo, Michael C. Thorndyke, and Lucia Manni. pp 185-198


Invertebrate Biology 120(2):97-103
© 2001 American Microscopical Society, Inc.

Food plaquette digestion in the ciliated protozoan Hyalophysa chattoni Abstract. The digestion of food plaquettes in the ciliated protozoan Hyalophysa chattoni was analyzed by light and electron microscopy. Through the use of nigrosin as a tracer for light microscopy and polystyrene microparticles for electron microscopy, we have demonstrated that food plaquettes transform to late-stage digestive vesicles. Eventually, in the phoront, some of the late-stage vesicles merge to form larger fusion vesicles, which are retained in the peripheral cytoplasm of the ensuing feeding stage. After the feeding stage settles and encysts, these vesicles are either retained by the daughter cells or are left in the divisional cyst as residual bodies. Food plaquettes, digestive vesicles, and fusion vesicles stain positively with neutral red and acridine orange, indicating an acidic pH. These results portray a unique digestive pathway in which stored, undigested material is reorganized into larger fusion vesicles as the cell prepares for additional feeding.

Additional key words: endocytosis, food vacuole, apostome, acridine orange, neutral red


Invertebrate Biology 120(2):104-123
© 2001 American Microscopical Society, Inc.

Temperate and tropical algal-sea anemone symbioses Abstract. In this review, we seek to develop new insights about the nature of algal-sea anemone symbioses by comparing such associations in temperate and tropical seas. Temperate seas undergo pronounced seasonal cycles in irradiance, temperature, and nutrients, while high irradiance, high temperature, and low nutrients are seasonally far less variable in tropical seas. We compare the nature of symbiosis between sea anemones (|actinians) and zooxanthellae (Symbiodinium spp.) in both regions to test tropical paradigms against temperate examples and to identify directions for future research. Although fewer anemone species are symbiotic in temperate regions, they are locally dominant and ecologically important members of the benthic community compared to the tropics.

Additional key words:


Invertebrate Biology 120(2):124-135
© 2001 American Microscopical Society, Inc.

Macrodasyida (Gastrotricha): a cladistic analysis of morphology Abstract. A cladistic analysis based on 33 morphological characters was performed for the 31 genera currently assigned to the order Macrodasyida (Gastrotricha). Outgroup analysis indicated that the order is monophyletic and that it is defined by the structure of the pharynx and the complex distribution of duo-gland adhesive organs. Of the 6 currently recognized families in Macrodasyida, our analysis confirmed that 4 families are monophyletic: Dactylopodolidae, Macrodasyidae, Thaumastodermatidae and Turbanellidae. Dactylopodolidae was further confirmed as the most basal family within the order based on the retention of several plesiomorphies. The other three families have well-defined autapomorphies but will require further investigation to increase inter- and intrafamilial phylogenetic resolution. Planodasyidae appeared to be a paraphyletic taxon with no obvious autapomorphies; genera clustered among members of a polyphyletic family, Lepidodasyidae. We recommend that future research on macrodasyidan phylogeny focus on issues of comparative morphology and ultrastructure in lesser-known taxa such as the Dactylopodolidae, and on the taxa Lepidodasyidae and Planodasyidae.

Additional key words: phylogeny, aschelminthes


Invertebrate Biology 120(2):136-141
© 2001 American Microscopical Society, Inc.

A carnivorous bdelloid rotifer, Abrochtha carnivora n.sp. Abstract. Here we describe a new bdelloid rotifer, Abrochtha carnivora n.sp., that preys on other bdelloids and monogonont rotifers. This is the first report of predatory behavior in bdelloids. Despite this extraordinary behavior, A. carnivora displays no major structural deviation from the standard body plan for members of the bdelloid family Philodinavidae: body with head (with ciliated corona), trunk, and foot, mastax with ramate trophi. The finding of such a carnivorous species, unique for the class, appears to contradict the common assumption that the wholly parthenogenetic bdelloids are evolutionary dead-ends.

Additional key words: Rotifera, Bdelloidea, Philodinavidae


Invertebrate Biology 120(2):142-148
© 2001 American Microscopical Society, Inc.

Influence of lowered salinity and elevated cadmium on the survival and metamorphosis of trochophores in Capitella sp. I. Abstract. It is well known that the competent larvae of many marine invertebrate species can be stimulated to metamorphose by exposing them to elevated concentrations of certain ions, neuroactive substances, and pharmacological agents. In this study we report that larvae of the euryhaline polychaete Capitella sp. I are induced to metamorphose within 24-48 h by reducing salinity from 30 ‰ to 12-15 ‰. At 10 ‰, however, fewer larvae metamorphosed and the normal metamorphic response to sediment was inhibited; competence was restored within 3 h of transferring the larvae back to full strength seawater (30 ‰). Larvae also metamorphosed within 24 h in response to increased external cadmium concentrations of 1000-2000 µg l-1. Further understanding of how reduced salinity and elevated cadmium stimulate (or inhibit) metamorphosis may lead to a better understanding of signal perception and transduction in this and other species.

Additional key words: larvae, metamorphosis, polychaete


Invertebrate Biology 120(2):149-161
© 2001 American Microscopical Society, Inc.

Partial characterization of the secretory material from the dorsal bodies in the snail Helisoma duryi (Mollusca: Pulmonata), and its effects on reproduction Abstract. Both dorsal body tissue extracts and dorsal body-conditioned medium stimulated in vitro polysaccharide synthesis in albumen gland explants in Helisoma duryi. This activity is heat- and protease-resistant. Dorsal body tissue extracts and dorsal body-conditioned medium were passed through solid-phase extraction cartridges, then eluted with increasing concentrations of methanol (20%, 70%, and 100%) and the various eluates tested for their biological activity. An active factor was found in the 100% methanol wash from both dorsal body tissue extracts and the conditioned medium. In addition, another bioactive factor in the conditioned medium eluted with 70% methanol. The endocrine dorsal bodies in the freshwater snail H. duryi were maintained in vitro, and following incubation, the culture medium was collected and tested for the presence of ecdysteroids. Radioimmunoassay of the culture medium demonstrated the presence of ecdysteroid-like immunoreactivity, suggesting the dorsal bodies are capable of secreting ecdysteroids in vitro. Identification of released ecdysteroids by HPLC/RIA revealed a number of immunoreactive fractions, which were tested for bioactivity. To test for possible physiological functions of ecdysteroids in Helisoma duryi, 20-hydroxyecdysone (a potent ecdysteroid in arthropods) was injected into non-egg laying (virgin) snails. Injections of ecdysteroid induced low egg-laying activity and the maturation of oocytes in the ovotestis. Incubation of albumen glands with ecdysteroid stimulated polysaccharide synthesis. The results are discussed in relation to the possible function(s) of ecdysteroids in pulmonate snails.

Additional key words: albumen gland, polysaccharide, ecdysteroid, ovotestis, chromatography


Invertebrate Biology 120(2):162-169
© 2001 American Microscopical Society, Inc.

Apical antennal sensilla in nymphs of Libellula depressa (Odonata: Libellulidae) Abstract. In an ultrastructural study of the apical antenna of the last nymphal stages of Libellula depressa (Odonata: Libellulidae), we found long sensilla trichodea, 2 sensory pegs, and a coeloconic sensillum on the last article of the flagellum (the distal part of the antenna). The long sensilla trichodea are mechanoreceptors, almost identical to the long filiform hairs of some terrestrial insects and the first sensilla of this kind to be described in aquatic insects. Particular attention was given to the complex coeloconic sensillum, a compound sensillum innervated by 2 groups of 3 neurons wrapped in a dendritic sheath. A cuticular sleeve envelops the distal portion of the outer dendritic segment. The cuticle of the coeloconic sensillum shows wide channels and is contiguous to the underlying granular and fibrillar layer. Similar structures on the antennae of the adults of other dragonflies were identified as chemoreceptors in previous studies. We hypothesize that this larval coeloconic sensillum might likewise have a chemosensory function, responding to molecules that diffuse through the cuticle and the underlying granular and fibrillar layer, as no clear pore or pore-tubule system is visible. Alternative functions are also explored on the basis of morphological details.

Additional key words: dragonflies, sensory systems


Invertebrate Biology 120(2):170-177
© 2001 American Microscopical Society, Inc.

Prey attraction by larvae of the New Zealand glowworm, Arachnocampa luminosa (Diptera: Mycetophilidae) Abstract. The hypothesis that bioluminescence produced by larvae of the New Zealand glowworm, Arachnocampa luminosa, attracts prey was tested experimentally in Reserve Cave, Waitomo, New Zealand, and in its bush-clad entrance over a total of 200 days during winter, spring, and summer. We compared catches on transparent adhesive traps placed either over glowworms or over areas from which glowworms had been removed. Adhesive traps over glowworms caught significantly more invertebrates per trap per day than did control traps. Glowworms in bush attracted greater numbers and types of invertebrates than did glowworms in the cave. Diptera predominated in both bush (86% of the total catch) and cave (89%). Also caught were small numbers of Araneae, Coleoptera, Hymenoptera, Orthoptera, Trichoptera, Gastropoda, Acarina, and Neuroptera--listed in order of abundance--but no adults of A. luminosa were caught. Glowworms under adhesive traps survived with little or no food for up to 78 days.

Additional key words: bioluminescence, cave ecology


Invertebrate Biology 120(2):178-184
© 2001 American Microscopical Society, Inc.

Induced inflammatory process in the sea urchin Lytechinus variegatus Abstract. In vitro and in vivo studies confirmed endocytic activity of free phagocytic amebocytes in Lytechinus variegatus. Amebocytes in the perivisceral coelom were labeled with injected ferritin, and ferritin-labeled amebocytes were found in the peristomial connective tissue only one hour after injection of India ink or yeast into this tissue. The presence of ferritin inside the amebocytes indicates that these cells migrated from the perivisceral coelom to the peristomial connective tissue. After 24 hours, particles of India ink or yeast were observed inside the ferritin-labeled amebocytes, indicating the amebocytes' ability to respond to an inflammatory stimulus. These were the only inflammatory cells found in L. variegatus, using the above mentioned stimuli and time spans.

Additional key words: Echinoidea, Echinodermata, amebocytes, coelomocytes, phagocytes


Invertebrate Biology 120(2):185-198
© 2001 American Microscopical Society, Inc.

The peripheral nervous system of an ascidian, Botryllus schlosseri, as revealed by cholinesterase activity Abstract. In this study we present the first detailed description of the motor component of the peripheral nervous system of an ascidian showing its three-dimensional organization and the spatial relationships between nerves and contiguous organs. Nerves of the oozooid and blastozooid of the colonial ascidian Botryllus schlosseri were analyzed using a histochemical method for detecting cholinesterase activity in whole-mount preparations and in sections for light and electron microscopy. Except for the neural gland and gonads, all tissues are well innervated by cholinesterase-reactive neurites. Each blastozooid of the colony possesses an individual nerve plexus which is not in continuity with that of adjacent zooids. The innervation of the mantle, oral and cloacal siphons, branchial basket, heart, and gut are described. Most organs possess a complex network of nerves often with multiple origins from different pathways. A sophisticated pattern is described for the first time in the gut, which receives innervation from the endostyle, the roof of the branchial basket, and the posterior mantle. Dilated axonal regions but no obvious cell bodies were recognized in the peripheral nervous system revealed by cholinesterase activity. The localization of nerves is discussed together with a consideration of their physiological role.

Additional key words: cerebral ganglion, cholinesterase, Tunicata, Urochordata