Comparative morphological studies on the visual systems in a binocular and a multi-ocular species of freshwater planarian

The visual systems of Bdellocephala brunnea Ijima & Kaburaki, a species with two eyes, and Polycelis sapporo (Ijima & Kaburaki), a species with multiple eyes, were investigated using light and electron microscopy. The eye of the binocular species consisted of 40–50 photoreceptor cells and 6–12 pigmented eyecup cells. The eye of the multi-ocular species was smaller and consisted in most specimens of one photoreceptor cell and one pigmented eyecup cell. The ultrastructure of the photoreceptor cells and of the pigmented cells was similar in the two species. Despite differences in numbers of constitutive cells, the arrangement of functional elements in the ocelli of these planarians is the same.     

Geographical distribution of Polycelis (Seidlia) auriculata in Japan

Polycelis (Seidlia) auriculata is endemic to mountain districts of Japan, from the central part of Honshû to the area of the Daisetsu Mts of Hokkaidô. In northern Japan, it sometimes occurs in cold-water biotopes of lowland areas. The progenitor of P. auriculata appears to have been the oldest immigrant into northern Japan among the Japanese Polycelis species, entering through a northern route as a preglacial faunal element. P. auriculata now shows a discontinious distribution in northern Japan. By virtue of its geographical and vertical distribution, ecological niche, variation in anatomy of the copulatory apparatus, and cytodemes, this species appears to be in the process of transformation.     

Dedifferentiation and redifferentiation of the penis of the freshwater planarian Bdellocephala brunnea

Following decapitation of Bdellocephala brunnea Ijima et Kaburaki and subsequent repeated removal of regenerating head-blastemas, the copulatory apparatus degenerated within 40–60 days. The copulatory apparatus disintegrated into cell clusters that further divided into separate neoblast-like cells that, in turn, eventually transformed into ordinary parenchymal cells by 60 days after decapitation. When the head of worms with a degenerate copulatory apparatus was allowed to regenerate by discontinuing excision of the head blastema, a new copulatory apparatus differentiated, ostensibly from the dedifferentiated cells. The neoblast-like cells appear to participate in the redifferentiation of the penis and of other parts of the copulatory apparatus.     

Production of cell- and tissue-specific monoclonal antibodies in the freshwater planarian Phagocata vivida

To provide a tool for studying regeneration in planarians, we have produced monoclonal antibodies against a variety of cells and tissues of the freshwater planarian Phagocata vivida (Ijima et Kaburaki). We obtained five kinds of monoclonal antibodies specific, respectively, to 1) the excretory system, 2) nerve cells, 3) rhabdoid-forming cells and body-surface mucus, 4) gastrodermal and epidermal cells, and 5) male germ cells and epidermis.     

Geographical distribution of Phagocata vivida in the Far East

Phagocata vivida (Ijima et Kaburaki, 1916) is common in cold-water habitats in mountainous and hilly regions in Japan; in Northern Japan it occurs in lowland areas. Comparative studies of the material from South Korea and Primorskiy in Northeast Siberia, Russia, show that Ph. vivida is distributed widely in these geographic areas. Phagocata miyadii Okugawa, 1939, reported from North Korea and Northeastern China is a synonym of Ph vivida. Geographical distribution of this species in the Japanese Islands now becomes very clear. Judging by its geographical and vertical distributions, the species probably is a preglacial faunal element that entered Japan by the northern route to Old Honshû Island along the coast of the Old Sea of Japan.     

A new species of the clingfish genus <Emphasis Type="Italic">Apletodon</Emphasis> (Teleostei: Gobiesocidae) from Sao Tome and Principe,Eastern Central Atlantic

The clingfish Apletodon wirtzi sp. nov. is described on the basis of ten specimens and colour photos from Bombom Island, Principe Group, Sao Tome and Principe, eastern central Atlantic Ocean. The species is very small, apparently not exceeding 16 mm total length; it is characterized by having three pores in the mandibular canal, the head length 2.2–2.5 in standard length: SL, the head broad, head width in males 3.6–4.0 (mean 3.8) in SL, the snout in males long, more or less pointed, conical, preorbital length in males 3.1–4.0 in head length, the occipital region with a large pinkish blotch behind each eye (in alcohol specimens), and the lower sides of the body with a row of dark blotches, scattered with white spots in between. The new species is compared with other species of the genus; a key to the males of the four known species of the eastern Atlantic genus Apletodon is presented. Supplementary material to this paper is available in electronic format at     

Instar-specific head and body lengths of Hyalella(Amphipoda): criteria for starting and endpoints in experimental studies

Abstract Instar-specific data on head length and body length of Hyalella azteca was obtained from live specimens reared individually at 23 ± 1 °C under a 14L:10D photoperiod and with food ad lib. Both head length and body length were strong predictors of instar number through instars 1 – 10. The relationship between instar number and head length was linear (head length [m] = 104.28 + 61.05[instar]; r ²=0.98, P<0.001), whereas that between instar and body length was not (body length [m] = 1339.28 + 55.82[instar]²; r ² = 0.97 , P< 0.001). Head length measurements were easier to obtain and were more accurate than body measurements. Both measurements can be obtained without injury to the animal, permitting repeated observations on the same individual.     

Pseudobagrus brachyrhabdion, a new catfish (Teleostei: Bagridae) from the middle Yangtze River drainage, South China

Pseudobagrus brachyrhabdion sp. nov., from the Yuan Jiang and Xiang Jiang of the middle Yangtze River drainage in Hunan and Guizhou Provinces, South China, is described herein. It is distinguished from all other Pseudobagrus species with a truncate or slightly emarginated caudal fin by an unique combination of the following characters: supraoccipital plate and nuchal plate broadly interspaced and covered with skin; nasal barbels only at most reaching anterior margin of eye; maxillary barbels reaching slightly beyond posterior margin of eye; outer mandibular barbels extending to posterior margin of eye; dorsal fin with a somewhat convex distal margin, origin nearer to pectoral-fin insertion than to pelvic-fin insertion; dorsal-fin spine shorter than pectoral spine, with a somewhat serrated posterior margin; pectoral-fin spine with a smooth anterior margin; anal fin with 20–23 rays, base length 23.8–32.0% of standard length, posterior end of anal-fin base anterior to posterior end of adipose fin base; no longitudinal black band extending along flank; eyes large, diameter 16.3–23.7% of head length; and number of vertebrae 5 + 43–46.     

SPECIES DISCRIMINATION AMONG PELAGIC HETEROPODS: RESOLUTION OF THE PTEROTRACHEA HIPPOCAMPUS--P. MINUTA PROBLEM

Four species of Pterotrachea are currently recognized, two ofwhich (P. hippocampus Philippi, 1836, and P. minuta Bonnevie,1920) have very similar morphologies. These two species havebeen distinguished mainly on the basis of eye and visceral nucleusshapes; the former with wide, triangular eyes and a short, broadnucleus, and the latter with narrower, triangular eyes and ataller, more slender nucleus. Quantitative and qualitative morphologicaldata were obtained from specimens of P. hippocampus and P. minuta collectedduring two oceanographic sampling programs in the North AtlanticOcean. Comparisons of eye and visceral nucleus shapes (representedby their length to width and length to retinal width ratios,respectively), plotted against body length showed linear decreases,with no justification for the recognition of two separate species.Examination of eye shape across a wide range of body sizes showedthat the width of the retina increases disproportionately with bodygrowth (by elongation and medial upturning) beginning at a length ofabout 21-22 mm. As a result, the overall appearance of the eyeat this body size changes such that smaller animals (less than21-22 mm) have eyes corresponding with those of P. minuta, whilethe eyes of individuals larger than this body length match thoseof P. hippocampus. Several authors have distinguished femalesof the two species by the presence (P. hippocampus) or absence (P.minuta) of cuticular spines anterior to the eyes. Examinationof female specimens showed that those less than about 30 mmlacked these spines, while those above this size possessed them.Thus, cuticular spines represent a secondary female sexual characteristic. Other morphological features that have been used by previousauthors to distinguish the two species were examined and rejected.Because P. hippocampus was described prior to P. minuta, itis herein regarded as the senior synonym of P. minuta. (Received 12 June 1997; accepted 21 May 1999)     

A new batfish,Coelophrys bradburyae (Lophiiformes: Ogcocephalidae) from Japan, with comments on the evolutionary relationships of the genus

A new ogcocephalid batfish,Coelophrys bradburyae, is described on the basis of a single specimen collected from the Pacific coast off Aomori, Japan, at a depth between 557–595 m. The species differs from others of the genus by having a small eye (7.1 in head length), short upper jaw (3.7 in head length), short pectoral and pelvic fins (length 3.0 and 9.6 in head length, respectively), small illicial cavity (width 5.3 in head length), and no bifurcated tubercles on the lateral surface of the body. A key to the species ofCoelophrys is given and the evolutionary relationships of the genus discussed based on cladistic analyses: the sister relationship withHalieutopsis was confirmed and possible paedomorphic states, including the globose body, proposed as having evolved secondarily from a flat-bodied ogcocephalid ancestor.     

Further survey of chromosomal polymorphisms in the freshwater planarian Polycelis auriculata

Although the chromosomal number of Polycelis (Seidlia) auriculata Ijima et Kaburaki is basically 2n = 6, this species shows remarkable chromosomal polymorphisms in different populations. Among worms collected at 30 stations in the central part of Japan's Main Island and in Hokkaido, we found five new karyotypes, considered to be variations of tetraploidy and diploidy: 4n?fis¹. + 1 = 3SM + 2A + 3T₁ + 2T₂ + 4M = 14, 4n?fis².(B) = 2SM + 2A + 4T₁ + 2T₂ + 4M + (0?2B) = 14 –16, 4n?fis². + 1 = 2SM + 2A + 4T₁ + 2T₂+5M= 15, 4n?fis².?2 = 2SM + 2A + 4T₁ + 4M = 12, and 2nM- = 2SM + 2A = 4 (where SM = submetacentric; A = acrocentric; T₁ and T₂ = telocentric; M = metacentric; B = B-chromosome; fis¹. and fis². = occurrence of one or two centric fissions, respectively; and M- = deletion of a metacentric chromosome). These karyotypes exist singly in one individual or as various mixoploids within the same individual. No individual having only karyotype 2nM- has yet been found. This brings the total number of known karyotypes in P. auriculata to 17; these can be arranged in an order that we believe reflects their evolution.     

The fine structure of the eyes of some bristly millipedes (Penicillata, Diplopoda): additional support for the homology of mandibulate ommatidia

The eyes of adult Phryssonotus platycephalus (Synxenidae) and Polyxenus lagurus (Polyxenidae) were investigated by light and electron microscopy. At each side of the head, various numbers of eye cups are situated on projections, the eye hills. The eye cups of P. platycephalus and P. lagurus are similarly structured and considered homologous sense organs. Each corneal lens is biconvex and formed by four to six pigmented corneagenous cells with their nuclei displaced towards the mid-periphery of the eye cup. The corneal surface displays a conspicuous nanostructure of fingerprint-like ridges in P. platycephalus. However, the corneal surface appears smooth in P. lagurus. In P. platycephalus. A rudimentary crystalline cone is observed in each eye cup, always produced by a constant number of three eucone cells. The crystalline cone is wedged between the corneal lens and the distal rhabdom and consists of three distinct compartments. Each cone compartment is connected to the voluminous proximal nuclear region by one elongated cytoplasmic process, which runs through the infraretinular space. A dual type retinula is always arranged in two distinct horizontal cell layers. The distal retinula contains an unfixed number of four to five cells in P. lagurus, whereas it contains five to eight cells in P. platycephalus. The distal retinula cells form a large and fused axial rhabdom. A constant number of three proximal retinula cells give rise to a small axial rhabdom, which looks more or less triangular in cross sections. The basal matrix is rather thin, inconspicuous and lines the bases of the eye cups. The ultrastructure of the eye cups of P. platycephalus resembles that observed in the ommatidia of the centipede Scutigera coleoptrata. The present study lends additional support to the homology of mandibulate ommatidia, because of the common possession of crystalline cone cells and a bilayered dual type retinula in the eye cups of P. platycephalus. Ommatidia or unicorneal eyes that include eucone cells with nuclei displaced outside the cone compartments, as found in Scutigeromorpha and Penicillata, might also be interpreted as an additional autapomorphy of the Myriapoda. The suggested homology of scutigeromorph and penicillate eyes implies that penicillate eye cups have to be considered modified, probably miniaturized ommatidia.     

A remarkable new species in the lichen genusPlacopsis from Papua New Guinea (lichenized ascomycetes,Agyriaceae)

Placopsis auriculata Lumbsch & Kashiwadani is described from Papua New Guinea. This new species is characterized by the presence of campylidia-like helmet-shaped soralia and the presence of the gyrophoric acid chemosyndrome. Hiascic acid is reported for the first time from theAgyriaceae. The distinction of that species from other sorediate species ofPlacopsis is briefly discussed.     

The food niches of the invasive Dugesia tigrina (Girard) and indigenous Polycelis tennis Ijima and P. nigra (Müller) (Turbellaria; Tricladida) in a Welsh lake

The invasion of Llyn Coron in North Wales by the American immigrant Dugesia tigrina resulted in the almost entire displacement of the native Polycelis tenuis and P. nigra populations. Because competition for food is the most important factor controlling and regulating populations of British lake-dwelling triclads, the diets of the invasive and native triclads in the lake were examined in an attempt to explain the successful invasion.A serological technique, the precipitin test, identified the gut contents of field-collected triclads. Niche breadth, electivity and niche overlap indices were used in analysis of the data. A broad food niche was recorded for all the triclad species. Oligochaetes predominated in the diet of D. tigrina followed by Asellus and chironomids, in almost equal proportions, snails and caddisflies, with mayflies scarcely eaten. Both Polycelis species fed heavily on oligochaetes followed by Asellus. P. tenuis ate slightly higher proportions of chironomids and caddisflies than snails and mayflies, whilst P. nigra consumed similar proportions of these four prey taxa. Gammarus, scarce in Llyn Coron, and cladocerans were not eaten by the Polycelis species and by only a few D. tigrina.To-date there has been no apparent shift in the diet of the Polycelis species as a consequence of the invasion by D. tigrina. In the absence of any evidence for the partitioning of food on the basis of prey size or condition, the considerable overlap in the diets of D. tigrina and the Polycelis species suggests the potential for severe inter-specific competition for food. The superior exploitation by D. tigrina of the available food resource requires explanation.     

The reproductive biology of Pellonula afzeliusi Johnels,and Sierrathrissa leonensis thys Audenaerde in Lake Kainji,Nigeria

Aspects of the reproductive biology of the two species of clupeids known to occur in Lake Kainji, Pellonula afzeliusi Johnels and Sierrathrissa leonensis Thys Van Den Audenaerde were studied for a period of twenty eight months. Mature individuals were found in both species all the year round but with a prolonged peak of activity from December to May, more distinct in P. afzeliusi than in S. leonensis.There were no significant length differences between mature males and females in both species. The smallest mature individuals were 28 mm standard length female; 27 mm standard length male in P. afzeliusi, while the corresponding figures for S. leonensis were 18 mm standard length female and 19 mm standard length male.No sexual dimorphism was observed. There was a simple correlation between fecundity and fish standard body length as well as weight in both species.     

The fine structure of the lateral eyes ofNeocarus texanus Chamberlin and Mulaik, 1942 (Opilioacarida,Acari, Arachnida,Chelicerata)

Summary Neocarus texanus, a primitive mite, bears two pairs of eyes, which are principally similar in ultrastructure. Each eye is covered externally by a cuticular cornea. It is underlain by flat sheath cells which send extensive processes into the retina. The retina is composed of distal and proximal cells. The 20 distal cells of the anterior eye are inversely orientated and form 10 disc-like rhabdoms. They represent typical retinula cells. Each rhabdom encloses the dendritic process of a neuron, the perikaryon of which is located outside the retina (proximal cells). The significance of this cell is not known. The retina is underlain by a crystalline tapetum. In the posterior eye 14 retinula cells form 7 rhabdoms in an arrangement similar to the anterior eye. The eyes of one side of the body are located within a capsule of pigment cells. Together the axons of the distal and proximal cells form the two optic nerves, one on each side of the body. The optic nerves leave the eyes anteriorly and terminate in two optic neuropils located in the brain.From structural evidence it is concluded, that the resolution of the eyes must be rather low.The peculiar proximal cells have not been observed previously in Acari. They probably resemble at best the eccentric cells and arhabdomeric cells of xiphosurans, scorpions, whip-scorpions and opilionids. Also, inverse retinae and tapeta of the present type have not been found in Acari until now, but are present in other Arachnida. Thus the eyes ofNeocarus texanus evidently represent a unique type within the Acari.     

Aerial performance of stalk-eyed flies that differ in eye span

Stalk-eyed flies have eyes placed laterally away from the head on elongated peduncles. The elongation of eye span may increase the energetic cost of flight, reduce flight performance via aerodynamic effects or via increased load, or necessitate compensatory changes in other body dimensions. Body mass and body dimensions were measured to test the hypothesis that elongation of eye span is correlated with increased head mass in two closely related species of stalk-eyed flies. Cyrtodiopsis whitei is sexually dimorphic, with the eye span of larger males exceeding body length. Cyrtodiopsis quinqueguttata is sexually monomorphic with eye span substantially less than body length. Although eye span was significantly longer in C. whitei, head mass did not differ between species after accounting for differences in body mass. C. whitei males had longer wings, heavier thoraxes, and lighter abdomens in relation to body mass than did female C. whitei or C. quinqueguttata of either sex. Three-dimensional tracking of flight paths showed that path velocity and the horizontal component of velocity did not differ according to species or sex, but the long-eyed C. whitei males showed reduced overall aerial performance by flying at shallower ascent angles and reduced vertical velocity. Although increased mass loading does not occur in C. whitei males, increased drag, aerodynamic effects from the wake of the eye stalks, and constrained visual processing are possible mechanisms which could cause their reduced performance. Accepted: 7 June 2000     

Revision of the genusgirella (girellidae) from east asia

The taxonomy of three species ofGirella from East Asian waters,G. punctata Gray, 1835,G. leonina (Richardson, 1846) andG. mezina Jordan & Starks, 1907, is reviewed and intraspecific (individual and ontogenic) variations detailed.Girella mezina is characterized by a very wide mouth and thick upper lip, the soft-rayed portion of the anal fin high and round, dorsal profile of the head abruptly slanting in front of the eyes in adults, a transverse yellow band on the body in life, and 3–4 rows of teeth along the outer jaw margins, the central cusp of each tooth being wider than the lateral cusps in adults.Girella punctata is characterized by usually 2 rows of teeth along the outer jaw margins, usually 7 transverse series of scales between the lateral line and median spinous portion of the dorsal fin (TRac), and usually 52–55 pored lateral line scales (LLp). The species is variable in body and caudal fin shape, extent of squamation on the opercular region, and number and position of dark spots on the scales. It also exhibits ontogenetic variation in the number of tooth-rows.Girella leonina is characterized by a conspicuously black opercular flap, essentially a single row of teeth along the outer jaw margins, usually 10–11 TRac and usually 59–64 LLp. Intraspecific variations were evident in the mouth position, scale condition and body color after death, and in the number of pores of cephalic lateral line canals. The holotype ofG. punctata, previously known only from a figure, is described for the first time.Girella melanichthys is synonymized underG. punctata with a lectotype designated for the former.     

A new genus and two new species of gobiid fishes (Perciformes) from the Chagos Archipelago,Central Indian Ocean

Synopsis A recent (1979) expedition to the Chagos Archipelago resulted in the collection of about 40 new taxa of fishes. A new genus,Trimmatom, and two new species,T. nanus andT. offucius, are described here. The new genus is characterized by having all pelvic-fin rays simple (unbranched), a scaleless body, no head pores, a wide gill opening extending anteroventrally to below the eye, and hypurals 1 and 2 fused to the complex formed by the fusion of the ural centrum and hypurals 3 and 4.T. nanuss andT. offucius are differentiated on the basis of fin ray counts and colour pattern.T. nanus is the smallest vertebrate yet to be described. Mature females with ovaries full of eggs are 8–10 mm in standard length.     

<Emphasis Type="Italic">Trichiurus nickolensis</Emphasis>, a new hairtail from Australia belonging to the <Emphasis Type="Italic">Trichiurus russelli</Emphasis> complex (Perciformes: Trichiuridae)

A new hairtail, Trichiurus nickolensis, is described on the basis of ten specimens collected off northwestern Australia, off the Northern Territory, and in the Gulf of Carpentaria, Queensland. The new species strongly resembles T. brevis Wang and You in Wang et al., 1992, off Hainan Island, South China Sea, and T. russelli Dutt and Thankam, 1966, off the Waltair Coast, Andhra Pradesh, India, in having the highest point of the supraoccipital crest situated directly above the posterior margin of the eye and a relatively short caudal peduncle. Trichiurus nickolensis differs from those two species in being strongly pigmented on the anterior section of the dorsal fin membrane (vs. slightly pigmented), and having a dorsal head margin that appears concave in lateral view, rises gently from snout tip to above middle of orbit, and then extends more steeply to dorsal fin origin (vs. rising gently from tip of snout to dorsal fin origin). The new species also has a greater number of dorsal fin rays (III, 138–143 vs. III, 127–132 and III, 127–131 in T. brevis and T. russelli, respectively) and total vertebrae (160–166 vs. 147–155 and 149–153), and shorter preanal length (mean 30% TL vs. 33% TL and 35% TL), head length (11% TL vs. 12% TL and 13% TL) and upper jaw length (4% TL vs. 5% TL and 5% TL).