The Fine Structure of the Cinctum of Ellobiophrya conviva (Ciliophora: Peritricha)

Ellobiophrya conviva clasps tentacles of the bryozoan Bugula neritina with a ring-like structure formed from aboral extensions of its body that taper into two slender arms. The tips of the arms overlap and join to form a unique organelle, the bouton. Each arm contains a massive myoneme that splays out at the bouton. The bouton consists of the cupped tips of the arms and a cavity, which is filled with dense homogeneous material. Long digitations containing longitudinal microtubules at their periphery project from the inner surface of the tip of each arm into the cavity. Deep folds of pellicle with pores opening into their depths line the wall of the cavity. Conventional kinetosomes are not visible in the bouton, but circular or elliptical arrays of microtubules are found at the bases of digitations. The nonfunctional scopula of the adult is in a depression enclosed by pellicular folds. The bouton is distant from the scopula, but its fine structure somewhat resembles it, supporting Chatton and Lwoff's hypothesis that the cinctal arms carry parts of the scopula at their tips. The fine structure of the cinctum supports their suggestion that the cinctal arms are homologous to the spasmonemes of vorticellid peritrichs.     

The fine structure of the cinctum of Ellobiophrya conviva (Ciliophora: Peritricha).

Ellobiophrya conviva clasps tentacles of the bryozoan Bugula neritina with a ring-like structure formed from aboral extensions of its body that taper into two slender arms. The tips of the arms overlap and join to form a unique organelle, the bouton. Each arm contains a massive myoneme that splays out at the bouton. The bouton consists of the cupped tips of the arms and a cavity, which is filled with dense homogeneous material. Long digitations containing longitudinal microtubules at their periphery project from the inner surface of the tip of each arm into the cavity. Deep folds of pellicle with pores opening into their depths line the wall of the cavity. Conventional kinetosomes are not visible in the bouton, but circular or elliptical arrays of microtubules are found at the bases of digitations. The nonfunctional scopula of the adult is in a depression enclosed by pellicular folds. The bouton is distant from the scopula, but its fine structure somewhat resembles it, supporting Chatton and Lwoff's hypothesis that the cinctal arms carry parts of the scopula at their tips. The fine structure of the cinctum supports their suggestion that the cinctal arms are homologous to the spasmonemes of vorticellid peritrichs.     

Diversity of the free-living marine and freshwater Copepoda (Crustacea) in Costa Rica: a review

The studies on marine copepods of Costa Rica started in the 1990’s and focused on the largest coastal-estuarine systems in the country, particularly along the Pacific coast. Diversity is widely variable among these systems: 40 species have been recorded in the Culebra Bay influenced by upwelling, northern Pacific coast, only 12 in the Gulf of Nicoya estuarine system, and 38 in Golfo Dulce, an anoxic basin in the southern Pacific coast of the country. Freshwater environments of Costa Rica are known to harbor a moderate diversity of continental copepods (25 species), which includes 6 calanoids, 17 cyclopoids and only two harpacticoids. Of the +100 freshwater species recorded in Central America, six are known only from Costa Rica, and one appears to be endemic to this country. The freshwater copepod fauna of Costa Rica is clearly the best known in Central America. Overall, six of the 10 orders of Copepoda are reported from Costa Rica. A previous summary by 2001 of the free-living copepod diversity in the country included 80 marine species (67 pelagic, 13 benthic). By 2009, the number of marine species increased to 209: 164 from the Pacific (49% of the copepod fauna from the Eastern Tropical Pacific) and 45 from the Caribbean coast (8% of species known from the Caribbean Basin). Both the Caribbean and Pacific species lists are growing. Additional collections of copepods at Cocos Island, an oceanic island 530 km away of the Pacific coast, have revealed many new records, including five new marine species from Costa Rica. Currently, the known diversity of marine copepods of Costa Rica is still in development and represents up to 52.6% of the total marine microcrustaceans recorded in the country. Future sampling and taxonomic efforts in the marine habitats should emphasize oceanic environments including deep waters but also littoral communities. Several Costa Rican records of freshwater copepods are likely to represent undescribed species. Also, the biogeographic relevance of the inland copepod fauna of Costa Rica requires more detailed surveys.     

Marine biodiversity of Costa Rica: Crustacea: Infraorder Anomura

The anomuran crabs are among the best known crustacean groups from the Pacific coast. However, this group is poorly known from the Caribbean coast of Costa Rica. In this compilation based on the literature and the collection at the Zoology Museum, Biology School, University of Costa Rica, we report the presence of 114 species of the Infraorder Anomura for Costa Rica, 20 species from the Caribbean, 96 species from the Pacific (two are present on both coasts). Twenty-nine species are new reports for Costa Rica, 15 from the Caribbean coast (74% of the total of species from that coast) and 14 from the Pacific (15% of the total from the Pacific). The range often species is extended to Costa Rica, siete from the Caribbean and three from the Pacific. Six species are reported for the first time from Cocos Island, where there are also four endemic species.     

Tectonic survey of the Central Pacific coast of Costa Rica

Three fossil coral samples (Pocillopora elegans and Pocillopora damicornis) were collected from a beachrock in Puerto Escondido, central Pacific coast of Costa Rica. The age of the samples ranged from 1272+/-60 to 2010+/-60 years BP. They represent some of the few Holocene fossil corals known from the Pacific coast of the Americas. The uplift rate for the central Pacific coast of Costa Rica was calculated in 0.4 to 2.1 mm year(-1).     

Marine biodiversity of Costa Rica: the phyla Sipuncula and Echiura

Fourteen species of Sipuncula belonging to 9 genera have been reported from Costa Rican waters, mostly from the Pacific coast. Three of these species are new records for Costa Rica (Phascolion strombus (Montagu 1804), Aspidosiphon (Aspidosiphon) muelleri Diesing 1851, and Aspidosiphon (Aspidosiphon) gracilis schnehageni (W. Fisher 1946)). One species of Echiura, Thalassema steinbecki Fisher 1946, in the order Echiuroinea, has been reported from the Pacific coast of Costa Rica.     

Structure of the brachiopod lophophore

Data on the development, structure, and functional morphology of the brachiopod lophophore are analyzed. The common origin of the tentacle apparatus in Lophophorata from the postoral ciliary band of the larva is shown. The brachiopod lophophore is based on the brachial axis consisting of the brachial fold running along the row of tentacles. The brachial axis may be attached to the brachial (dorsal) mantle lobe (trocholophe, schizolophe, and ptycholophe lophophores) or extend freely into the mantle cavity to form coiling brachia (spirolophe, zygolophe, and plectolophe lophophores). The circulation of water flows through the mantle cavity in the brachiopods with attached and free lophophores is described. A new hypothesis on the sorting of particles suspended in water during filtration is proposed.     

Sperm transfer and reproductive biology in species of hermaphroditic bivalves (Galeommatoidea: Montacutidae)

The histology of the reproductive organs is studied in the protandric hermaphroditic Tellimya ferruginosa. In NW Europe the species reproduces from May through August. Sperm transfer takes place when mature testis follicles are transplanted to the gills or walls of the mantle cavity in recipient hermaphroditic or female bivalves. Transplantation is accompanied by histological changes and sperm cells are released when transplants perish with age. Details are given on the reproduction in Montacuta percompressa which takes place from March through October in North Carolina, USA. All shelled bivalves are females and it is postulated that spermatogenic bodies attached to gills or other surfaces in the female's mantle cavity and previously considered to be dwarf males arise from transplanted larval gonads. The ultrastructure of the euspermatozoa and/or the anucleate paraspermatozoa is described in T. ferruginosa, T. tenella, and M. percompressa. The sperm of the first two species share a number of significant apomorphies with those of another montacutid, Brachiomya stigmatica. In the simultaneous hermaphroditic M. substriata the nucleate paraspermatozoa associate with the euspermatozoa to form spherical spermatozeugmata that are stored in the testis.     

New records of benthic marine algae and Cyanobacteria for Costa Rica,and a comparison with other Central American countries

We present the results of an intensive sampling program carried out from 2000 to 2007 along both coasts of Costa Rica, Central America. The presence of 44 species of benthic marine algae is reported for the first time for Costa Rica. Most of the new records are Rhodophyta (27 spp.), followed by Chlorophyta (15 spp.), and Heterokontophyta, Phaeophycea (2 spp.). Overall, the currently known marine flora of Costa Rica is comprised of 446 benthic marine algae and 24 Cyanobacteria. This species number is an under estimation, and will increase when species of benthic marine algae from taxonomic groups where only limited information is available (e.g., microfilamentous benthic marine algae, Cyanobacteria) are included. The Caribbean coast harbors considerably more benthic marine algae (318 spp.) than the Pacific coast (190 spp.); such a trend has been observed in all neighboring countries. Compared to other Central American countries, Costa Rica has the highest number of reported benthic marine algae; however, Panama may have a similarly high diversity after unpublished results from a Rhodophyta survey (Wysor, unpublished) are included. Sixty-two species have been found along both the Pacific and Caribbean coasts of Costa Rica; we discuss this result in relation to the emergence of the Central American Isthmus.     

Marine biodiversity of Costa Rica: class Polychaeta (Annelida)

Three hundred and thirty two species of polychaetes belonging to 50 families are reported for Costa Rica based on previously published reports. In a few families, available material was re-examined and appropriate changes in species identifications were made. Only three species, (Glycera oxycephala Ehlers, 1887; Hemipodia pustulata (Friedrich 1956); and Scolepis (Scolepis) squamata (Miller, 1806)) have been reported from the Caribbean coast of Costa Rica, and these three species have also been reported from the Pacific Coast. The families with more than 15 species are the Spionidae (26), Cirratulidae (24), Nereididae (21), Lumbrineridae (19) and Paraonidae (16). Despite extensive sampling on the Pacific coast over the last 25 years, the Costa Rican polychaete fauna, especially that of the Caribbean coast, remains poorly known.     

Ultrastructure of the Peritrich Ciliate Ambiphrya ameiuri and Its Attachment to the Gills of the Catfish Ictalurus punctatus1

Ambiphrya ameiuri is an ectocommensal peritrich that attaches to the gills of warm-water fishes and filters bacteria from the water. The ultrastructure of this protozoon, its attachment to the fish gills, and its effect on the gill tissue were investigated by scanning and transmission electron microscopy. The peritrich attached to the gills by fibers extending from the scopula. A microtubular array, apparently a barren kinetosome, was present in each lobular projection, but no scopular cilia were observed. At low densities Ambiphrya had no apparent harmful effects on the fish; however, at high densities respiration may be impeded. Ultrastructural studies indicate that this organism receives no nourishment from the host tissue.     

Morphology and biology of Polysaccus japonicus (Crustacea, Rhizocephala, Akentrogonida, Polysaccidae, fam. n.), a parasite of the ghost-shrimp Callianassa japonica

The morphology and biology of Polysaccus japonicus Høeg & Lützen, 1993 is described. Nearly all infected hosts are adults, the females of which become castrated. Each bears 4–50 (female) externae on the underside of the abdomen. The externae are interconnected via a root system within the host's perineural blood sinus. The externae pass through three moults. Cypris larvae inject spermatogonia into the immature externa's mantle cavity, which is where spermiogenesis occurs later. Multiplication of the male cells is probably supported by secretion from paired mantle cavity glands, presumably homologous to the receptacles of kentrogonid rhizocephalans. Late during the 2nd intermoult the visceral mass ruptures to release the ova into the mantle cavity where they become fertilized. The third moult results in opening of the mantle aperture which initiates a period of vigorous peristalsis of the muscular mantle. Following emission of the cypris larvae the externae perish leaving distinct scars. The root system always contains buds of various sizes and stage of development. When the scarred host moults, the most advanced buds emerge to give rise to a new generation of externae. This is thought to be repeated for the rest of the host's life.
The antennule of the cyprid has a relatively very long and slender 3rd segment, a unique construction among Akentrogonida. Because of this and the presence of special mantle cavity glands, a new family, Polysaccidae, is erected, which in some characters is intermediate between the Kentrogonida and the Akentrogonida.     

Two new species of nudibranchiate molluscs from the west coast of North America, with a revision of the family Cuthonidae

Two species of nudibranch molluscs are described from the northeastern Pacific Ocean on the west coast of North America. These are: a new aeolid species of Cuthona Alder & Hancock, 1855 (family Cuthonidae) from the Oregonian marine zoogeographical province and a new dorid species of Acanthodoris Gray, 1850 (family Onchidorididae) from the Panamic province in the Gulf of California. The internal anatomy and external features of each species are compared with related species. Differences in structure of the radula, reproductive system and other morphological aspects are described. A revision of the family Cuthonidae is included. Evidence is presented to include the genera Trinchesia Ihering, 1879, and Precuthona Odhner, 1929, within the genus Cuthona. Cuthona alpha Baba & Hamatani, 1963, is synonymized with Catriona columbiana (O'Donoghue, 1922). We consider the New World Cuthonidae to be composed of the following five genera: Catriona Winckworth, 1941; Cuthona Alder & Hancock, 1855; Embletonia Alder & Hancock, 1851; Tenellia Costa, 1877; and Tergipes Cuvier, 1805.     

Sighting of Stenella attenuata, the spotted dolphin, in Culebra Bay, Costa Rica, 1999-2000

Parallel to a zooplankton study (1999-2000) observations were made (from an inflatable boat), on the presence of dolphins along a transect (-8 km long) on the axis of Culebra Bay (24 km2), Gulf of Papagayo, Pacific coast of Costa Rica. Dolphins were found during 20 of the 31 boat surveys conducted. The only species of cetacean found in the bay was Stenella attenuata, the spotted dolphin. These sightings were more frequent during the rainy season, particularly during the month of May of both years. The presence of S. attenuata in Culebra Bay might be associated to the abundances of fish and mollusks (their presumed prey: for example, squids), as evidenced by fishery statistics available for this zone of the Pacific coast of Costa Rica.     

Deposit feeding in Abra tenuis (Bivalvia: Tellinacea)

Deposit feeding in Abra tenuis is described in terms of the size of particles utilized.
Material is collected by the inhalant siphon performing a circular motion sucking in sediment from beneath and on the surface.
The size distribution of silica admitted into the mantle cavity is described and shown to be controlled by physical parameters. The density of a particle does not affect its uptake by the inhalant siphon. The size distribution of the sediment affects the size distribution of particles admitted to the mantle cavity.
No selection of material for ingestion in terms of size occurs after it has been taken into the mantle cavity. Thus the range of material ingested is ultimately controlled by a physical parameter, the inhalant opening.     

Two commensals on a host: habitat partitioning by a ciliated protozoan and a chironomid on the burrowing mayfly, Ephemera danica

SUMMARY 1. Two taxonomically unrelated species, the ciliated protozoan Scyphidia sp. and the chironomid Epoicocladius flavens (Malloch), share a commensal mode of life on nymphs of the burrowing mayfly Ephemera danica Müller in a small river in eastern England.
2. Both commensals were present all through the year, with an average level of infestation of 25.1% and 54.7% for Scyphidia sp. and E. flavens , respectively, of the total E. danica population.
3. Scyphidia sp. occurred more frequently on younger, smaller nymphs of E. danica and was totally absent from hosts of more than 10 mm in length. In contrast, E. flavens preferred hosts of larger body size, usually more than 10 mm. Change in dominance of infestation between the two commensals occurred in the host size range of 6–8 mm and this pattern of habitat partitioning on the basis of host size was consistent throughout the study period.
4. Amongst E. danica individuals colonized by E. flavens , larger hosts supported heavier commensal load. A similar trend, though weak, was also observed among hosts harbouring Schyphidia sp.
5. Both commensals are considered to benefit from the association with E. danica in that they gain enhanced mobility and security in otherwise inhospitable habitats. Although plausible on an evolutionary time scale, competition alone cannot constitute a proximate cause for the clear partitioning of habitat observed in the two commensal species.     

Theletrum lamothei sp. nov. (Digenea), parasite of Echidna nocturna from Cuajiniquil, Guanacaste, and other digenes of marine fishes from Costa Rica.

A new species of Theletrum is described from the intestine of two palenose morays, Echidna nocturna, collected in Cuajiniquil, Guanacaste Province, Costa Rica. The new species differs from the type species, T. fustiforme Linton, 1910 by having a subspherical pars prostatica, a subspherical seminal vesicle extending anteriorly to the anterior border of the acetabulum, by the presence of a poorly developed hermaphroditic sac, and by having a larger body size. We also report eight additional species of digeneans parasitizing marine fishes in several localities along the Atlantic and Pacific coast of Costa Rica: Bianium simonei, Didymozoinae (metacercariae), Ectenurus virgulus, Hypocreadium myohelicatum, Lecithochirium microstomum, Pseudolecithaster sp., Stephanostomum casum, and Tergestia laticollis. In addition, we present an updated list of helminth parasites of marine fish from Costa Rica and discuss the importance of including parasites as an integral part of biodiversity inventories.     

Studies on the reproduction of cirripedes. I. Introduction: Copulation,release of oocytes,and formation of the egg lamellae

A brief outline is given of the sequence of events leading to the production of egg lamellae in operculate and pedunculate cirripedes.Details are given of the copulatory act as regards random and possibly directed movements of the penis; the question of mutual ‘recognition’ is discussed. The time spent by a spermatozoon in the penis is estimated. The release of ripe oocytes is described and the results of some experiments suggesting the presence of an agent suppressing their release in the earlier stage of maturation are given. It is shown that seminal plasma can induce muscle contractions and the possible significance of this is discussed.The behaviour subsequent to copulation is described. Fully motile spermatozoa are found in the mantle cavity and may be expelled in the mantle cavity current. The bulk of the semen sets to a translucent jelly which is eventually lost from the mantle cavity. The formation of this gel is due to general autolysis. The production, properties, and functions of the egg membranes and the oviducal sac are discussed.     

Siphonariid development: Quintessential euthyneuran larva with a mantle fold innovation (Gastropoda; Panpulmonata)

Recent phylogenetic revisions of euthyneuran gastropods (“opisthobranchs” and “pulmonates”) suggest that clades with a planktotrophic larva, the ancestral life history for euthyneurans, are more widely distributed along the trunk of the euthyneuran tree than previously realized. There is some indication that the planktotrophic larva of euthyneurans has distinctive features, but information to date has come mainly from traditional “opisthobranch” groups. Much less is known about planktotrophic “pulmonate” larvae. If planktotrophic larvae of “pulmonates” share unique traits with those of “opisthobranchs,” then a distinctive euthyneuran larval-type has been the developmental starting template for a spectacular amount of evolved morphological and ecological disparity among adult euthyneurans. We studied development of a siphonariid by preparing sections of larval and postmetamorphic stages for histological and ultrastructural analysis, together with 3D reconstructions and data from immunolabeling of the larval apical sensory organ. We also sought a developmental explanation for the unusual arrangement of shell-attached, dorso-ventral muscles relative to the mantle cavity of adult siphonariids. Adult siphonariids (“false limpets”) have a patelliform shell but their C-shaped shell muscle partially embraces a central mantle cavity, which is different from the arrangement of these components in patellogastropods (“true limpets”). It is not obvious how shell muscles extending into the foot become placed anterior to the mantle cavity during siphonariid development from a veliger larva. We found that planktotrophic larvae of Siphonaria denticulata are extremely similar to previously described, planktotrophic “opisthobranch” larvae. To emphasize this point, we update a list of distinctive characteristics of planktotrophic euthyneuran larvae, which can anchor future studies on the impressive evolvability of this larval-type. We also describe how premetamorphic and postmetamorphic morphogenesis of larval mantle fold tissue creates the unusual arrangement of shell-muscles and mantle cavity in siphonariids. This result adds to the known postmetamorphic evolutionary innovations involving mantle fold tissue among euthyneurans.