Ventral Depression Research Articles

Variations in the retinal designs of pulmonate snails (Mollusca, Gastropoda): squaring phylogenetic background and ecophysiological needs (I)

Abstract. The eyes of aquatic pulmonates differ from those of terrestrial pulmonates; the latter, in species such as Cepaea nemoralis and Trichia hispida, possess conventional, cup‐shaped retinas, but the aquatic species Lymnaea stagnalis, Radix peregra, Physa fontinalis, and Planorbarius corneus have retinas that are partitioned into dorsal and ventral depressions (“pits”). The pits are separated by an internal ridge, called the “crest”, and on account of their pigmentation can be seen in vivo. The dominant cellular components of the retinae of terrestrial as well as aquatic snails are pigmented cells and microvillar photoreceptors, the latter occurring in two morphologically distinct types (I and II). Aquatic snails with preferences for shallow water possess eyes with both type I and type II photoreceptive cells, but Pl. corneus, an inhabitant of deeper water, only has type‐I receptors, supporting an earlier finding that type I cells represent dim‐ and type II cells bright‐light receptors. On the basis of histological and optical comparisons, we conclude that the eyes of L. stagnalis and R. peregra, species that are known to escape and seek temporary refuge above the water surface, are well adapted to function in water as well as air, but that the eyes of P. fontinalis and Pl. corneus are less modified from those of their terrestrial ancestors.

A NEW SPECIES OF TORRENT FROG GENUS HYLODES (ANURA: LEPTODACTYLIDAE) FROM SOUTHEASTERN BRAZIL

We describe a new species of Hylodes from Parque Estadual do Ibitipoca, Conceicao do Ibitipoca, Municipality of Lima Duarte, State of Minas Gerais, southeastern Brazil. The new species is a member of the Hylodes lateristrigatus group, and it is characterized by small size, snout rounded in dorsal view and protruding in lateral view, presence of vocal slits and sacs, upper surface of finger discs without well developed scutes, dorsum light brown to gray with dark blotches, and details of the advertisement call. Descriptions of the tadpole, vocalizations, and information on natural history are provided. The tadpole has a ventral depression anterior to the coiled intestine, as in other species of the genus. Hylodes meridionalis (Mertens), previously considered a member of the H. nasus species group, is transferred to the H. lateristrigatus species group.

Scanning electron microscopy of the collar region of Deropristis inflata and Echinostoma revolutum

Scanning electron microscopy (SEM) was used to study the collar region of Deropristis inflata (Molin, 1858), an intestinal digenean of fish, and Echinostoma revolutum (Froelich, 1802), an intestinal digenean of birds. The results showed basic differences in the following morphological features. The collar of D. inflata was open ventrally and dorsally whereas that of E. revolutum was closed dorsally and ventrally, forming a kidney-like ring. The collar of D. inflata was located posterior to the oral sucker, some distance behind the anterior end of the body. That of E. revolutum was located terminally around the oral sucker. The collar of D. inflata had numerous collar spines which varied in size, shape and position. That of E. revolutum had 37 collar-spines, mainly homogenous in their general morphology and with a typical arrangement pattern for 37-collar-spined echinostomes. The collar of D. inflata had few tegumentary papillae whereas that of E. revolutum had abundant papillae. A ventral depressed area occurred in D. inflata, between the acetabulum and oral sucker, dividing the collar into two left and right independent parts. The ventral depression in E. revolutum extended from the ventral sucker to the posterior end of the collar, and was not divided. In D. inflata, tegumentary spines were located on the oral sucker, and the collar was posterior to the sucker. In E. revolutum, the oral sucker and the collar lacked tegumentary spines. The region immediately posterior to the collar also lacked spines in E. revolutum. The collar pattern of D. inflata is undoubtedly more primitive than that of E. revolutum.

Scanning electron microscopy of the collar region of Deropristis inflata and Echinostoma revolutum

Scanning electron microscopy (SEM) was used to study the collar region of Deropristis inflata (Molin, 1858), an intestinal digenean of fish, and Echinostoma revolutum (Froelich, 1802), an intestinal digenean of birds. The results showed basic differences in the following morphological features. The collar of D. inflata was open ventrally and dorsally whereas that of E. revolutum was closed dorsally and ventrally, forming a kidney-like ring. The collar of D. inflata was located posterior to the oral sucker, some distance behind the anterior end of the body. That of E. revolutum was located terminally around the oral sucker. The collar of D. inflata had numerous collar spines which varied in size, shape and position. That of E. revolutum had 37 collar-spines, mainly homogenous in their general morphology and with a typical arrangement pattern for 37-collar-spined echinostomes. The collar of D. inflata had few tegumentary papillae whereas that of E. revolutum had abundant papillae. A ventral depressed area occurred in D. inflata, between the acetabulum and oral sucker, dividing the collar into two left and right independent parts. The ventral depression in E. revolutum extended from the ventral sucker to the posterior end of the collar, and was not divided. In D. inflata, tegumentary spines were located on the oral sucker, and the collar was posterior to the sucker. In E. revolutum, the oral sucker and the collar lacked tegumentary spines. The region immediately posterior to the collar also lacked spines in E. revolutum. The collar pattern of D. inflata is undoubtedly more primitive than that of E. revolutum.

Morphology and Taxonomy of Arcytophyllum serpyllaceum (Rubiaceae), a Transfer from Hedyotis

outline, and with a central punctiform hilum. The seeds as shown by scanning electron microscopy are very similar to those of Arcytophyllum muticum (Weddell) Standley, a prostrate, suffruticose species of Costa Rica, Panama, and South America. Seeds of Hedyotideae have been found to be very important in classification (Terrell, 1996). Seeds of Houstonia are crateriform and the hilum is on a hilar ridge (Terrell, 1996), whereas seeds of Hedyotzos serpyllacea are non-crateriform (without ventral depressions or cavities) and lack hilar ridges. Oldenlandia seeds are trigonous or conical and usually much smaller than those of the other genera. Hedyotis as presently recognized includes a heterogeneous array of species, as previously pointed out (Terrell, 1996). I have examined seeds of all of the Western Hemisphere species of Hedyotis, as well as those of many of the Asian species including the type, H. fruticosa L., and all of these seeds differ from those of Hedyotis serpyllacea. A systematic treatment of Arcytophyllum serpyllaceum (Hedyotis serpyllacea) is presented here. This extends the distribution of Arcytophyllum from Panama and Costa Rica into Guatemala and southern Mexico, and also records the first collection of H. serpyllacea in Oaxaca (first noticed by Robert King, cited as Terrell & King 4441).

Stomatogenesis in Kyaroikeus cetarius (Dysteriina, Kyaroikeidae, N. Fam.): Clues to Its Systematic Placement

ABSTRACTMorphogenesis in Kyaroikeus cetarius, a large phyllopharyngean parasite of odontocete Cetacea, begins with the midventral proliferation of four short rows of kinetosomes immediately to the left of four pre‐existing, somatic kinetofragments. The resulting field of eight short kineties is located within a shallow depression that gradually elongates and deepens to form the oral cavity of the opisthe. The four right‐most of these kineties sink into the developing oral cavity and divide transversely, producing three distinct sets of kinetofragments. The anterior and posterior sets each consist of four small fragments and ultimately produce the mid‐ventral, somatic kinetofragments of the proter and the opisthe, respectively. In addition, some kinetosomes from the anterior set give rise to the secretory organelle complex of the proter. The central group consists of two long and one short kinetofragment, which represent anlagen for the opisthe circumoral and preoral kineties, respectively. These anlagen migrate progressively anteriad while undergoing a pronounced counterclockwise rotation that eventually inverts the developing oral kineties. Simultaneously, two broad sheets of microtubules, one beneath each circumoral anlage, extend deep into the cytoplasm and unite to line the cytopharynx of the opisthe. Meanwhile, the remainder of the eight original kinetofragments move laterally out of the ventral depression to produce the left ciliary field of the opisthe. Morphogenetic events observed in K. cetarius are typical of cyrtophorid Phyllopharyngia and support inclusion of this genus within suborder Dysteriina.

A New Species of Hedyotis (Rubiaceae) from Jalisco, Mexico

Hedyotis macvaughii, a new species from Jalisco, Mexico, is described and compared with related taxa. It is a small wiry-stemmed perennial herb with filiform leaves, small funnelform flowers, and non-crateriform seeds. Among specimens lent by MICH was a previously unnamed species collected by Rogers McVaugh in Jalisco, Mexico. It is here described as a new species of Hedyotis. Hedyotis macvaughii Terrell, sp. nov. TYPE: Mexico. Jalisco: steep mountain sides 3-10 km generally E on the road to Mina del Cuale from the junction 5 km NW of El Tuito, Mpio. de Cabo Corrientes, elev. 850-1150 m, 16-19 Feb. 1975, R. McVaugh 26426 (holotype, MICH). Figures 1, 2. Herba perennis rhizomata. Caules 15-20 cm alti erecti. Folia filiformia. Inflorescentia diffusissima. Corolla alba infundibuliformis 3.0--4.5 mm longa. Capsulae subglobosae 1-2 mm longae. Semina 0.3-0.5 mm longa compressa ellipsoidea hilo punctiformi in crista ventrali. Perennial herbs with slender rhizomes. Stems 15-20 cm tall, subterete, erect, very slender, wiry, glabrous, widely and diffusely branched, internodes numbering ca. 5-6. Leaves 6-20 mm long, 0.3-0.7 mm wide, filiform, with 2 inconspicuous grooves beneath, obtuse, glabrous above and beneath. Stipules to 1 mm long and wide, inconspicuous, entire or few-toothed. Inflorescences widely spreading, diffuse, to ca. 15 cm wide, with many filiform branches, flowers heterostylous, in many 2-5-flowered cymes, pedicels filiform, to ca. 15 mm long. Calyces glabrous; lobes 4, 0.4-0.8 mm long, 0.20.5 mm wide, broadly lanceolate, obtuse. Corollas 4-lobed, 3.0-4.5 mm long, funnelform, white; tubes 2.0-2.7 mm long, 0.5-0.6 mm wide at base; lobes 1-2 mm long, 0.5-1.5 mm wide, ovate. Anthers 4, ca. 0.5-0.8 mm long. Pollen colporate type A. Stigmas 2-branched, ca. 0.5 mm long, linear. Pin flowers with stigmas slightly exserted at corolla throat, anthers located at /3-1J2 point of corolla tube. Thrum flowers with anthers slightly exserted at corolla throat, stigma not seen. Capsules 1-2 mm long and wide, subglobose, thin-walled, straw-colored, ?-7/s inferior, apices rounded or truncate, dehiscence loculicidal. Seeds several per capsule, 0.3-0.5 mm long, 0.2-0.35 mm wide, brown, dorsiventrally moderately compressed, in outline broadly elliptic, blong, or ovoid, sometimes irregularly angulate, non-crateriform, dorsal side almost smooth or obscurely reticulate, convex, ventral side finely reticulate, hilum punctiform on acentric hilar ridge, ridge obtuse or acutish, low to rather high, testa with areoles single or double walled. Chromosome number unknown. Hedyotis macvaughii (spelling in accordance with Greuter et al., 1994: Rec. 60 C.4.(a)) is somewhat geographically isolated from related species that occur to the eastward in Mexico, as there are no records of Hedyotis or Houstonia species occurring in Jalisco, Colima, Michoacin, or Nayarit (Standley, 1918; Terrell, 1991). The new species is distinct in its morphology. It is a small wiry-stemmed perennial herb with filiform leaves and small funnelform flowers (Fig. 1). The seeds (Fig. 2) lack any kind of ventral depression or cavity, hence are non-crateriform. They are moderately dorsiventrally compressed and have a punctiform hilum on a low to rather high hilar ridge. These seed characters ally the new species with Hedyotis rather than Houstonia, which has crateriform seeds, or Oldenlandia, which has distinctive 3-angled (trigonal) or conic seeds (Terrell, 1991). Lewis (Terrell et al., 1986) recognized three types of pollen aperture structure, based on the extent of thinning of the nexine in the equatorial region. Two of these types, colpororate and colporate type B, occur in Houstonia, whereas Hedyotis and Oldenlandia have predominantly colporate type A. For Hedyotis macvaughii, Lewis (pers. comm., May 1995) reported the occurrence of colporate type A pollen. There are three species that superficially resemble or might be confused with Hedyotis macvaughii: Hedyotis asperuloides Bentham, Houstonia palmeri A. Gray, and Houstonia longifolia Gaertner. Hedyotis asperuloides of Baja California, Mexico, is a small annual with corollas 3-11 mm long, anthers 1.0-1.3 mm long, stigma branches 1.0-1.4 mm long, capsules 1.3-5.0 mm long that are turbinate, NovoN 6: 128-130. 1996. This content downloaded from 157.55.39.215 on Wed, 31 Aug 2016 04:44:24 UTC All use subject to http://about.jstor.org/terms Volume 6, Number 1 1996 Terrell Hedyotis macvaughii from Mexico 129

Cranial osteology ofLongosuchus meadeiand the phylogeny and distribution of the Aetosauria

ABSTRACT The aetosaur Longosuchus meadei is known from several specimens from the Upper Triassic (Carnian) of Texas. The structure of the single well preserved skull (TMM 31185-84B) was restudied in light of the appearance of new material of other archosaurs subsequent to Sawin's original (1947) description. In particular, an ossified orbitosphenoid and several structures associated with the nasolacrimal duct system are described and discussed for the first time. Adaptations for herbivory in the Aetosauria include the ventral depression of the jaw joint, the edentulous beak, and the conical, unserrated teeth in later aetosaurs. The increased ossification of the braincase may serve to protect this region during food processing, and the nasolacrimal structures probably are associated with the lateral nasal sinus system widespread in archosaurs and particularly well developed in Longosuchus. The Aetosauria are a robust monophyletic group of Suchia that can be characterized by five synapo-morphies. Aetosaurus...

Cinco espécies de Lecithodendriidae (Trematoda) en murcielagos de Colombia, incluyendo tres nuevos generos

Velez, I. & V.E. Thatcher: Five species of Lecithodendriidae (Trematoda) in bats from Colombia, including three new genera. Three new neotropical genera and species of Lecithodendriidae (Trematoda) are described from Colombian bats. Sturniratrema umbilicata gen. et sp. nov. from Sturnira lilium differs from other genera in having an oval ventral depression, a dorso-ventrally curved cirrus and a genital pore lateral to the acetabulum. Chiropterotrema antioquiense gen. et sp. nov. from Carollia perspicillata is distinguished by having the acetabulum within a triangular ventral pit as well as an separation between the the male and female genital pores. Topsiturvitrema verticalia gen. et sp. nov. from Carollia perspicillata has a different orientation of the body, being nearly spherical but somewhat flatened in an anterior-posterior direction. This genus also has a deep ventral cleft separating two ventral lobes which are filled with eggs. Castroia silvai Travassos, 1928, is also reported from Anoura caudifer and Peropteryx macrotis. The first of these represents a new host record for the species. Addiotionally, Limatulum gastroides Macy, 1935, is reported from Lonchophyla robusta wich is another new host record.

Ultrastructure of Adult Gonads and Development and Structure of the Larva of Rhabdopleura normani (Hemichordata: Pterobranchia)

AbstractSexually mature adults, embryos and larvae of the pterobranch Rhabdopleura normani from Bermuda were studied with light and electron microscopy. The sexes are separate among the zooids of a colony, but a given colony may contain females and males. In zooids of either sex the single gonad is associated with a large haemal sinus in the trunk sac and is displaced laterally (to the right or to the left). The wall of the gonad is composed of three layers: an outer metasomal peritoneum, an internal lining of germinal epithelium and an intervening genital haemal sinus. The mature gametes lie in the lumen within the gonad. The spermatozoon is characterized by an elongate nucleus, no obvious acrosome, a long mitochondrial filament in a midpiece appendix and a single flagellum with a 9+2 axoneme. Females brood 200 μm eggs and embryos in their distinctive, basally coiled tubes. The yolky eggs undergo radial cleavage and develop into ciliated, lecithotrophic, oblong larvae (400 μm in length) that are characterized by: (1) yellow coloration peppered with black pigment spots; (2) a deep ventral depression; (3) a posterior adhesive organ; (4) an anterior apical sensory organ; (5) an evenly ciliated epitdermis. The ventral depression is not invaginating endoderm, but is instead a glandular epithelium that evidently secretes the larval cocoon and the adult tube. Internally, the peritoneum of the coelomic cavities begins to split from the periphery of a large, central mass of yolky mesenchyme cells. The larva swims using cilia, but also undergoes contractions, evidently powered by the peritoneal cells, which constitute a myoepithelium. The discussion considers pterobranch affinities with other deuterostomes and with lophophorates.

Settlement and Metamorphosis of Rhabdopleura normani (Hemichordata: Pterobranchia)

AbstractSettling and metamorphosing larvae of the pterobranch hemichordate Rhabdopleura normani from Bermuda were examined with light microscopy, providing the first detailed description of the morphological changes during larval metamorphosis in pterobranchs. The swimming larvae settle within 24 h after being released from the parent tube. The settled larva immediately everts the ventral depression and surrounds itself with a translucent, sealed cocoon. During metamorphosis, which takes place over 7–10 days within the protective cocoon, structural changes occur in the following sequence: (1) differentiation of the oral shield from the anterior region; (2) budding of the two arms from the mid‐dorsal surface; (3) development of the posterior stalk from the adhesive organ; (4) budding of the tentacles on the arms; (5) formation of the pharynx from invaginated ectoderm; (6) formation of the gut and pericardium from the remaining mesenchyme. The gut is the last structure to become functional. The larva relies on stored nutrients throughout metamorphosis. The metamorphosed juvenile builds a tube at an opening in the cocoon and begins to feed. Similarities with lecithotrophic bryozoan and enteropneust larvae are discussed.

Scanning electron microscopic studies of the body surface and external genitalia of a dicrocoeliid trematode,Concinnum epomopis Sandground 1973

A detailed study of the surface topography ofConcinnum epomopis (Dicrocoeliidae) was carried out with a scanning electron microscope. The ultrastructural observations demonstrate the absence of spines on the body surface; however, the tegument is complex, exhibiting distinct, minute, lateral undulations, predominantly on the ventral side. The pattern of the tegumentary lamellae in different regions of the body is described. Two types of sensory papillae, the pit-type and the aciliate dome-type exhibit a uniform and distinct pattern of distribution on the surface of the worm. The pit-type is limited to the ventral depression anterior to the oral sucker. The pre-acetabular ventral genital opening, the posterior terminal excretory pore and pre-equatorial opening of the Laurer's canal are devoid of structural specialization and sensory papillae. The cylindrical, everted cirrus is covered with anastomosing, longitudinal lamellae of tegument, between which lie minute aggregates of protuberances forming the cirral papillae.

Ultrastructure of the genus Enteromonas da Fonseca (Zoomastigophorea) and revision of the order of Diplomonadida Wenyon

Fine structure of 2 species of Enteromonas, one from the intestine of the salamander, Triturus vulgairs, and another from the feces of domestic rabbit, Oryctolagus cuniculi, is described. The pyriform cell has an anteriorly located nucleus. The 4 flagella originate from an area near the anterior end of the nucleus. The recurrent flagellum (R) is lodged in a ventral depression or cytostome. The kinetosomes, arranged into 2 pairs, anterior (no. 1, no. 2) and posterior ("3, R), are interconnected by microfibrils. One microtubular fiber, connected to kinetosome "1, is situated near the anterior surface of the nucleus. Another, subnuclear, microtubular fiber is homologous to the "crossed" fiber found in Diplozoa. The cytostome is bordered by 2 lips: the preeminent left lip is equipped with several rows of microtubules, while the right lip contains only a thin microtubular fiber associated with microfibrils. The cytostome occupies 2/3 of the ventral surface. The recurrent flagellum passos over the anterior surface of the cell and then comes to lie in the cytostome. The bacteria are phagocytosed in the bottom part of the cytostome between the 2 distended lips. They are digested in numerous vacuoles. The undigested residual bodies are evacuated by a rupture of the cell membrane. The ergastoplasm is concentrated near the cell periphery. Mitochondria and the Golgi apparatus are absent. In the cyst stage, the multinucleate cell is enclosed in a microfibrillar membrane; the axonemes lie free in the cytoplasm. Diplomonad forms of Enteromonas resembling Hexamita are numerous, except that the cytostome is different in these 2 genera. In such forms, the arrangement of the 2 individuals often has binary axial symmetry, but on occasion they are associated in a more anarchic fashion. The mastigont of Enteromonas is organized like that of a single zooid of a diplozoon. It is possible that the genus Enteromonas is ancestral to Diplomonadida and that the diplomonad state, transitory in Enteromonas, became permanently established in Diplomonadida. Enteromonas appears to be more primitive than the other genera of Diplomonadida. Thus we propose 2 suborders: Enteromonadina, subord. nov. with the genus Enteromonas, and Diplomonadina Wenyon, emend., with the genera Trepomonas, Trigonomonas, Hexamita, Spironucleus, Octomitus, Giardia. The arrangement of the kinetosomes and the existence of a cytostome are the principal characters common to Enteromonas and Retortamonadida, while their "accessory" fibers are not homologous. A more complete study of division of the 2 zooflagellate orders is necessary for the presentation of a more detailed evolutionary scheme of these groups.

Ultrastructural and other observations which suggest suctorian affinities for the taxonomically enigmatic ciliate Cyathodinium.

SYNOPSIS. Two species of the taxonomically enigmatic genus Cyathodinium, C. piriforme and C. cunhai, were studied in some detail at both light and electron microscopic levels. Data obtained strongly suggest suctorian affinities for the genus, since a number of structures or features are strikingly reminiscent of similar (if not homologous) structures recently discovered in ciliates belonging to the order Suctorida.Endosprits (suctorial tentacles?) of Cyathodinium show an arrangement of microtubules not unlike that known for several suctorians, especially Acineta and Tokophrya. Haptocysts or missile‐like bodies, ca. 600 mμ long, have been observed within endosprits and free in the cytoplasm; again this is reminiscent of the complex organelles recently described from several suctorian groups. Mouthlessness, coupled with the presence of a ventral depression (functioning in gathering prey at distal ends of endosprits?) and the presence of food vacuoles in the cytoplasm, further support a suctorian mode of feeding. Finally, stages in the curious life cycle of Cyathodinium suggest neoteny and a basic similarity to endogenous budding processes in certain suctorians.

Development, Structure, and Function of Coverings of Eggs of Floodwater Mosquitoes. III. Functions of Coverings1

In Aedes aegypti (L.), on which this paper is largely based, the envelopes composing the egg shell have different functions. The exochorion imbibes water from saturated atmospheres and releases it slowly while drying. An annular line of weakness, from which a cap later dehisces, is determined by a structural change in the chorion at or about the time when embryogenesis is completed. The chorion, by changes in stratification, tanning, and infiltration by water-repellent chemicals, combines with the endochorion to create a barrier to movement of water. Hatching is brought about when the embryo is activated to elevate its hatching spine against the fracture line while applying pressure toward the water, the larva rapidly expands and soon swims a ventral depression of the cap. Once exposed to sway.