Comparative ultrastructure of the terminal portions of the male copulatory apparatus in Planorbidae (Gastropoda: Pulmonata)

Terminal portions of the male copulatory apparatus of Planorbis planorbis, Segmentina oelandica, and Anisus vortex were studied using whole-mount preparations, serial semi-thin sections, and transmission electron microscopy. In the latter species, stylet formation was investigated at several stages of postembryonic development. Organization of the penial distal portion in the species studied varies greatly. In P. planorbis, the distal end of the penis lacks developed papillae and is armed with a stylet built up of the covering epithelial cells of the penis proper. In A. vortex, the stylet is formed by the secretory activity of the middle cells of the distal portion of the penis. To the time of maturation, the cells encompassing the stylet are broken down exposing its solid chitinous structure and characteristic shape. In S. oelandica, the distal end of the penis bears the long probably flexible papilla with the characteristics of an internal ‘skeleton,’ organized as a line of connective tissue cells and a system of hydrocoelic cavities.     

A new species of Gyraulus (Gastropoda: Planorbidae) from Ancient Lake Lugu,Yunnan-Guizhou Plateau,Southwest China

A new aberrant species of the planorbid genus Gyraulus, Gyraulus luguhuensis n. sp., is described from Lake Lugu (Lugu-hu, in Chinese), Southwest China. The generic assignment with Gyraulus is based on features of the genital anatomy that are characteristic for members of that genus, in particular the presence of a chitinized penial stylet. Gyraulus luguhuensis n. sp. differs from most other congeners by its large, thick shell with an elevated spire. Similarly, aberrant shells are known from congeners in other Ancient Lakes worldwide indicating a potentially convergent evolution of shell characteristics in exclusively lacustrine species. Gyraulus luguhuensis differs from other lacustrine Gyraulus species with similarly large shells in having a sub-terminal penis pore and an unkeeled shell.     

The morphology of gills of Haliotis tuberculata (Linnaeus, 1758)

Manganaro, M., Laurà, R., Guerrera, M.C., Lanteri, G., Zaccone, D. and Marino, F. 2011. The morphology of gills of Haliotis tuberculata (Linnaeus, 1758). —Acta Zoologica (Stockholm) 93 : 436–443. Although the morphology of abalone gills has been studied by some authors, up to date no data are available about the gills of Haliotis tuberculata. This study was carried out, by light and electron microscopy, on 10 wild adult H. tuberculata. Gills lamellae produce an undulated surface increasing the area in contact with water. At the level of skeletal rods, we observed a joint‐like structure that allows a checked movement. The left ctenidium is always decidedly larger than the right, probably because of the enormous size of the shell muscle. The cilia permit oxygenated water that leaves the afferent border and is thrust away at the tips of the lamellae by the extremely long cilia. Ciliary movement may take part in sweeping mucous secretions to capture extraneous particles and remove them from the gills. Three types of mucous cells are distributed along the epithelium of the afferent and efferent zones of the gill filament. They seem to play a role in the cleansing of gills in coordination with the muscle contraction and ciliary movement. The presence of microvilli on particular cells reflects their role associated with the absorption of substances from the environment. A haemolymphatic vessel is located in the central zone of the gill filament. The backbone of the haemolymphatic vessel is a chitino‐like structure, which gives support to the gills.     

Surface morphology of eggs of Euproctis chrysorrhoea (Linnaeus, 1758)

Candan, S., Suludere, Z. and Bayrakdar, F. 2007. Surface morphology of eggs of Euproctis chrysorrhoea (Linnaeus, 1758). —Acta Zoologica (Stockholm) 88 : 000–000. Filaments covering the egg batches and chorion structure were studied both by light and scanning electron microscopy in the brown‐tailed moth Euproctis chrysorrhoea (Linnaeus, 1758). Females lay eggs in masses on the underside of apple leaves. The egg batches are covered with brown hairs derived from the bodies of the female. Each female lays about 200–400 eggs. The spherical eggs are about 0.84 mm long and 0.47 mm wide. Newly deposited eggs are golden‐yellow and darken after the onset of embryonic development. The micropylar area appears somewhat depressed and has a circular outline. The region is surrounded by a rosette of 10–12 petal‐shaped primary cells, which are completely surrounded by a series of secondary and tertiary cells. The remainder of the egg is largely smooth, but shows aeropyles. These are located in the corners of ill‐defined polygons.     

Karyotype delineation in Isidora truncata (Gastropoda: Planorbidae)

Metaphase chromosomes of a single Sardinian population of Isidora truncata were examined in an attempt to provide a picture of a standard karyotype to which Sardinian populations could be referred. Several new foci were identified and mapped.     

Squamation and scale character stability in cichlids, examined in Sarotheroden galilaeus (Linnaeus, 1758) (Perciformes, Cichlidae)

Squamation and scale morphology provide interesting characters for phyletic analysis within the Cichlidae. It is not known, however, to what extent these characters are genetically fixed or determined by environmental parameters. To clarify this point, a study on Sarotherodon galilaeus was conducted. This species has an extensive distribution and lives in markedly different environments. Most scale characters were found to be remarkably stable within the species. The only large variations occur in scale counts, extent of caudal fin Squamation, number of circuli and radii, and the extent of scale granulation. The Squamation pattern, the form of the circuli and radii, the shape of interradial rostrad projecting tongues, the denticles on the circuli in the rostral field, and especially the kind of granulation in the caudal field is similar in all specimens examined and is also retained in fish bred in aquaria for several generations. Thus it seems justified to assume that these characters are strongly determined by genetic factors and that their analysis can be useful in the determination of phyletic relationships.     

The male postabdomen and reproductive system of Bibio marci Linnaeus, 1758 (Hexapoda: Diptera: Bibionidae)

The male postabdomen and the internal parts of the male genital system of Bibio marci (Bibionomorpha) were examined and reconstructed 3‐dimensionally. Several features differ from the presumptive dipteran groundplan. The bases of the gonopods are fused with each other and with tergite IX. The penis is not tube‐shaped and only sclerotized on the ventral side. The vasa deferentia are S‐shaped, and two pairs of accessory glands are present. In contrast to these characteristics, the arrangement of the internal parts is probably close to the ancestral condition. With its specific shape, the penis is well suited for the transfer of a spermatophore. The dorsal sclerite of the copulatory organ probably represents the medially fused parameres. A cladistic analysis of 27 characters of the postabdomen yielded two most parsimonious trees, with the strict consensus as follows: Nannochoristidae (outgroup) + (Culicidae [Culicomorpha] + ((Nymphomyiidae + (Tipulidae + Trichoceridae)) + (Tabanidae [Brachycera] + (Bibionidae, Anisopodidae, Axymyiidae [Bibionomorpha])))). Potential synapomorphies of Bibionomorpha (including Axymyiidae) and Brachycera are the fusion of sternum IX with the gonocoxites, the fusion of the parameres forming the dorsal sclerite and the presence of an entire series of postabdominal muscles (M4, M20, M23, M26, M27, M31, M35 and M37). The results of the analysis are preliminary as it is based on a single‐character system with a limited taxon sampling. However, the main result – a clade Bibionomorpha + Brachycera – is fully compatible with current hypotheses on dipteran phylogeny.     

An analysis of fertilization in Bulinus cernicus (Gastropoda: Planorbidae)

Experiments have been carried out to determine whether cross–fertilization, multiple insemination and sperm sharing occur in Bulinus cernicus. Snails collected from Canal La Paix, Mauritius, were found to be polymorphic for glucose phosphate isomerase, and from this stock three snail colonies homozygous for GPI 2/2, GPI4/4 and GPI6/6 were selected. Thus, three markers were available to monitor cross–fertilization. Isolated snails produced egg–masses by self–fertilization 40 days post–hatching. Egg–masses produced by self–fertilizing individuals tended to be smaller than those from cross–fertilizing snails, 367 eggs per egg–mass as opposed to 5–34. The majority of snails (70%) switched rapidly to cross–fertilization after pairing. Multiple insemination by two partners was common, heterozygous progeny were produced in a random manner and did not reflect the sequence of mating. No evidence of sperm sharing was found, snails were found to be capable of passing on their own sperm while still producing eggs fertilized by sperm received from an earlier mating. Differences in mating behaviour were noted between snails representing the homozygous GPI colonies, with snails from one colony adopting the female role more readily than those from the other two, which predominantly mated as males.     

Plesiophysa dolichomastix sp. n. (Gastropoda: Planorbidae)

A new species of planorbid mollusc, Plesiophysa dolichomastix (Greek dolichos = long, mastix = flagellum), collected from Lagoa da Pedra, municipality of Santa Rosa, state of Goiás, Brazil (15 degrees 01'S, 47 degrees 13'W) is described. It is indistinguishable by the shell characters from the five congeneric species described so far: P. striata (Orbigny, 1841), P. granulata ("Shuttleworth" Sowerby, 1873), P. guadeloupensis ("Fischer" Mazé, 1883), P. ornata (Haas, 1938) and P. hubendicki Richards & Ferguson, 1962. It differs from the anatomically studied species in the following characters: about 50 ovotestis diverticula, against 12 in granulata, 100 in ornata, unstated in hubendicki; and length of flagella - about as long as the penial complex -, against about 1/3 to 1/6 in the other three.     

Individual Growth of Planorbarius corneus (Planorbidae,Gastropoda) in Postlarval Ontogenesis

Russian Journal of Developmental Biology - Individual growth of 15 great ramshorn snail Planorbarius corneus individuals was studied in aquaculture at 20°С starting from 2 weeks after...     

Energy Metabolism in Postlarval Ontogenesis of Planorbarius corneus (Planorbidae,Gastropoda)

Russian Journal of Developmental Biology - The change in the rate and mass-specific rate of oxygen consumption was studied during individual ontogenesis of nine Planorbarius corneus individuals...     

Allozyme and morphology evolution in European Viviparidae (Mollusca: Gastropoda: Architaenioglossa)

The paper describes morphometric and allozymic differences among four European species of the family Viviparidae: Viviparus contectus (Millet, 1813), V. viviparus (Linnaeus, 1758), V. acerosus Bourguignat, 1862, and V. ater (Cristofori et Jan, 1832). Fourteen continuous biometrical characters were measured. Incremental discriminant-function analysis, principal-component analysis, and non-metric multidimensional scaling were applied to analysis of the morphometric differences. All the techniques confirmed a similar picture: a slight morphometric differentiation, with the variability ranges of the species overlapping. On the other hand, the allozymic differentiation, studied at 12 loci, eight of them intra and/or interspecific polymorphic, is much better marked, the intraspecific Nei's distances among the four V. contectus populations ranging from 0.0014 to 0.0397, mean 0.0166, and interspecific distances ranging from 0.2306 (V. ater–V. acerosus) to 0.9888 (V. contectus 2 and V. viviparus), mean 0.6871. The allele frequencies and genetic distances (Nei's distance and Cavalli-Sforza and Edwards’chord distance) were used to compute maximum likelihood, additive Fitch–Margoliash and ultrametric Fitch–Margoliash trees. All the trees presented a similar pattern, but the maximum-likelihood and additive trees, based on Cavalli-Sforza and Edwards’distance, seem to reflect the phylogeny best. The results are compared with the most parsimonious phylogenies inferred for radular, soft-part morphology and anatomy, and opercular data from other papers by us, and the inferred phylogenies are also compared. Although the inferred molecular and morphological phylogenies are little different in topology, the amount of evolution along the corresponding branches (measured as the number of changes averaged over all reconstructions) is very different, the value of correlation coefficient between the two phylogenies being statistically insignificant. The occurrence of interspecific hybrids is discussed, and the isolation-by-competition mechanism is postulated. The probable origin of V. viviparus from a founder population extremely restricted in number is stressed. The possible history of the group is briefly discussed. The species is suggested to have originated in an unusual habitat of melt water at a glacier foreland that could have promoted genotypic differentiation and sympatric speciation.     

Additive typogenesis in Thoanteus (Gastropoda: Bulminidae)

Thoanteus ferrarii sp. nov. from Crimea is described. The phylogeny of Thoanteus is reconstructed in a cladistic analysis and the evolution of this genus is discussed. Thoanteus ferrarii sp. nov. represents an early stage in the additive typogenesis of Thoanteus , in which the appendix retractor still inserts laterally at the appendix section A₁, a short distance from its proximal top, as in the Peristoma-like stem species of Thoanteus.     

Parental size and environmental conditions affect egg capsule production by Nassarius reticulatus (Linnaeus 1758) (Gastropoda: Nassariidae)

In shallow coastal habitats scavenging netted whelks Nassarius reticulatus attached egg capsules to the stipes of red algae Chondrus crispus and occasionally on Furcellaria lumbricalis and Plumaria plumose. In the laboratory egg capsules were laid on aquaria sides and lids by individuals ≥ 21 mm shell length. Larger size classes produced more egg capsules and spawned over a longer period and in doing so partitioned less energy into shell growth. Large netted whelks (25-28.9 mm) produced larger capsules which contained significantly more and larger eggs than those produced by smaller individuals (21-24.9 mm). Egg capsule production continued throughout the year by regularly fed N. reticulatus held at ambient seawater temperatures. Egg production increased in the spring and summer with peak production during June (15 °C), decreased between August and October and resumed again during the winter (November to February at ∼ 7 °C). During the summer (15-16 °C) egg capsules were smaller and contained smaller eggs than those deposited during the winter (7-10 °C), although the number of eggs · capsule⁻¹ was similar. Enforced food limitation reduced the number and size of the egg capsules, the number and size of eggs produced · female⁻¹ and the duration of the breeding period. Hatching success of N. reticulatus egg capsules was high (95%) even at winter seawater temperatures (11-8.5 °C) and the duration of embryonic development was fastest between 15 and 17.5 °C.     

Effects of intermittent starvation on mature Biomphalaria glabrata (Gastropoda: Planorbidae)

Mature Biomphalaria glabrata, submitted to four weeks of varied starvation times (0, 1, 3, 5, 6 & 7 d.week^–1, were thereafter refed during four weeks. The different intermittent starvation times had no significant effect on snails survival. As weekly starvation increased, the rate of change in body weight and fecundity decreased. In snails fed one or two d.week^–1, the rate of change in body weight was negative, while fecundity remained at a low level. Continuous hunger stopped oviposition.Starvation had no further effect on body growth after the first week of refeeding; however, its effect on fecundity remained significant over the two first weeks.     

On secondary hyperparathyroidism in orang-utans, Pongo satyrus (Linnaeus, 1758)

Orang-utan crania with alterations in bone structure which could be determined morphologically were studied and evaluated. The alterations in bone structure were referred to in the literature up to about 1939 as "rickets"; when vitamin D was given to the animals, the alterations diminished, until they were almost unnoticeable. From about 1941/52, the alterations were diagnosed as "Morbus Paget". Research on orang-utan crania has become possible through comparison of a larger number of single symptoms, occurring in a number of individuals. Out of a larger sample, the study was carried out on 5 individuals, showing these alterations in varying degrees. The individuals also covered various age groups, both sexes and both subspecies of orang-utans. The findings permit a diagnosis of secondary (or tertiary) hyperparathyroidism (= Morbus Engel-von Recklinghausen = fibrous cystic osteitis). The study also showed that orang-utans fall prey to Morbus Engel-von Recklinghausen in a shorter period and suffer more severely than humans. The frequency of orang-utans suffering from this disease, which are kept captive in zoos, is statistically far higher than the occurrence in humans. Orang-utans living under natural conditions do not suffer from the disease at all; according to the study of 500 animals. The authors also believe that there is a psychogenic basis for the occurrence of Morbus Engel-von Recklinghausen in zoo animals; psychological conditions such as apathy, disinterest, etc. are part of the illness, and these symptoms are also shown by animals having no outward signs of fibrous cystic osteitis. The authors believe that improved prophylaxis of orang-utans in zoos would lead to discovery of Morbus Engel-von Recklinghausen in early stages, and allow early therapy to arrest the disease. This is necessary for preservation of the species.     

Heritability of male outcrossing ability in the simultaneous hermaphrodite, Bulinus truncatus (Gastropoda: Planorbidae)

The heritability of phally, a dichotomous trait defined by the functional state of the male reproductive tract, was measured in a laboratory population of the simultaneous hermaphrodite snail Bulinus truncatus by means of a breeding experiment and a selection experiment. Euphallic individuals develop a fully functional male and female tract and are capable of receiving and donating sperm. In aphallic individuals the male tract does not develop fully, preventing sperm donation. There was no evidence of a heritable component to phally in the breeding experiment, but the selection experiment demonstrated a slight heritable effect. In both experiments there was more variation in the observed proportion of euphallics than expected by chance alone and no evidence of line or family effects, implicating environmental determination of male outcrossing ability even under controlled laboratory conditions. Previous studies of populations of B. truncatus reported that the proportion of euphallics was under strong genetic control. We suggest that there may be population differences in the extent of environmental control over phally, analogous to that reported for sex determination.