Warning colouration in pseudocerotid flatworms (Platyhelminthes,Polycladida). A preliminary study

Many species of tropical and subtropical pseudocerotid flatworms are noted for their brilliant colour patterns and conspicuous behaviour and are suitable candidates for the investigation of aposematic colouration. This study gives the first experimental evidence of aposematic colouration in pseudocerotid flatworms. Coloured and uncoloured agar models of flatworms were used to determine whether a fish predator, the moon wrasse Thalassoma lunare, could learn to avoid colourful flatworms on the basis of their colour pattern. The results showed that uncoloured models were more significantly attacked than coloured models (1% significance) and that there was no significant difference between attacks made to live flatworms and their respective models. These results clearly indicate the operation of aposematism in brightly coloured flatworms and demonstrate the operation of mimicry as the agar models were essentially non-living mimics of the flatworms. This revised version was published online in July 2006 with corrections to the Cover Date.     

Stylochus (Imogene) matatasi n. sp. (Platyhelminthes,Polycladida): pest of cultured giant clams and pearl oysters from Solomon Islands

A large polyclad flatworm has been consistently found associated with mortalities of the cultured giant clam,Tridacna gigas (L.) and the fouling pearl oysterPinctada maculata (Gould) in Solomon Islands.Stylochus (Imogene) matatasi n. sp. is described and a brief account of its biology is given.ICLARM Contribution # 856.ICLARM Contribution # 856.     

A molecular framework for the phylogeny of the Pseudocerotidae (Platyhelminthes,Polycladida)

Systematic relationships within the cotylean family Pseudocerotidae were examined using nucleotide sequences of the D3 expansion segment of the 28S rDNA gene. A previously suggested separation of Pseudoceros and Pseudobiceros based on the number of male reproductive systems was confirmed. Regardless of the algorithm employed, Pseudoceros always formed a monophyletic clade. Pseudobiceros appeared to be paraphyletic; however, a constrained maximum parsimony tree was not significantly longer (2 steps, = 0.05). Additionally, the genera Maiazoon, Phrikoceros and Tytthosoceros were validated as taxonomic entities, and their relationships to other genera within the family were determined. Molecular data also supported species separations based on colour patterns. An intraspecific genetic distance of 1.14% was found for Pseudoceros bifurcus, whereas the intrageneric distance was 3.58%. Genetic distances among genera varied, with the closest distance being 2.048% between Pseudobiceros and Maiazoon, and the largest distance (8.345%) between Pseudoceros and Tytthosoceros.     

First records of Cotylea (Polycladida,Platyhelminthes) for the Atlantic coast of the Iberian Peninsula

A study of polyclad fauna of the Atlantic coast of the Iberian Peninsula was carried out from 2010 to 2013. The paper reports nine new records belonging to three Cotylean families: the family Euryleptidae Lang, 1884, Pseudocerotidae Lang, 1884 and the family Prosthiostomidae Lang, 1884, and describes one new species, Euryleptodes galikiassp. n.     

The colour pattern of Lineus atrocaeruleus (Nemertia)

The colouration of living specimens of Lineus atrocaeruleus (Lineidae, Nemertea) is bluish or brownish black with many transverse yellow rings. The pigments responsible for the colouration are granular and are elaborated by epidermal and dermal pigment cells, both of which contain uroporphyrins. Granules of melanic nature occur in the dermal pigment cells. The significance of the epidermal pigment cells is discussed.     

Floral colour change in Pedicularis monbeigiana (Orobanchaceae)

We examined the effects of the retention of colour-changed flowers on long- and short-distance attractiveness of bumblebees and the likelihood of successive flower visits by bumblebees in Pedicularis monbeigiana. The lower lip changed colour with age from white to purple. Hand geitonogamous pollination significantly reduced seed production. No pollen limitation occurred in this species. Purple-phase flowers contributed minimally to pollinator attractiveness at long distance. The combination of less reproductive flowers with a lower amount of reward and floral colour change enabled plants to direct pollinators to reproductive, highly rewarding white flowers at close range. A high percentage of purple-phase flowers in an inflorescence was associated with a marked reduction in the frequency of successive flower visits to individual plants. We suggest floral colour change in P. monbeigiana may serve as a mechanism for enhancing inter-individual pollen transfer and reducing intra-individual pollen transfer.     

Predation potential of three flatworm species (Platyhelminthes: Turbellaria) on mosquitoes (Diptera: Culicidae)

We conducted a field survey for flatworms to select species as potential biological control agents against Aedes aegypti and Culex pipiens (Diptera, Culicidae) breeding in artificial containers. Laboratory experiments were performed to determine the daily predation rate, differential predation on each mosquito larval instar, selective predation on either A. aegypti or C. pipiens, and predator tolerance to water from artificial containers. Girardia anceps (Tricladida, Paludicola, Dugesiidae), Mesostoma ehrenbergii and Bothromesostoma cf. evelinae (Rhabdocoela, Typhloplanoida, Typhloplanidae) were found in temporary puddles and permanent pools. In the laboratory, they killed between 52% and 100% of immature mosquitoes coexisting in the same habitat. No preference of flatworms for mosquito preys was detected. Predation rate was related to predator size and instar of preys. Girardia anceps and B. evelinae survived after a dry period and when re-flooding occurred, they laid eggs. Tolerance to water from artificial containers was highest in G. anceps and this species could be a suitable predator to reduce mosquito populations from artificial containers using an inoculative approach.     

Foliar form, colour and surface characteristics influence oviposition behaviour in the cabbage root fly Delia radicum

The effects of foliar form, colour and surface characteristics on the oviposition behaviour of the cabbage fly were investigated by presenting females with various leaf models made of paper. The models differed in shape, size, colour, surface coating, the presence of 3 dimensional folds and a stem. It was shown that in the presence of host leaf surface extracts physical factors can strongly influence oviposition behaviour. Females laid the most eggs around the base of bright green or yellow models having a stem, vertical folds and covered with a thin layer of paraffin. The vertical folds in the surface increased the chance of a behavioural transition from leaf run to stem run.

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Zusammenfassung Mit Hilfe von Papiermodellen von Kohlblättern wurde der Einfluss von visuellen und mechanischen Eigenschaften des Blattes auf das Eiablageverhalten der kleinen Kohlfliege, Delia radicum, untersucht. Die verwendeten Modelle unterschieden sich in Form, Grösse, Farbe, Oberflächen struktur und Stiel des Blattes. Es wurde gezeigt, dass physikalische Reize zusammen mit den chemischen Stoffe auf der Blattoberfläche stimulierend wirken. Ein natürliches Eiablageverhalten und die stärkste Eiablage wurde durch ein Modell ausgelöst, welches sich durch leuchtend grüne Farbe, Stiel und vertikale Falten und einen Paraffinnüberzug auszeichnete.

     

Condition and fecundity of the damselfly,Enallagma ebrium (Hagen): the importance of ectoparasites

Summary The extent, magnitude, and cause of natural covariation between degree of parasitism and other variables known or suspected of influencing host fitness (such as host age or body size) has been understudied. We demonstrate that degree of parasitism by larval water mites (Arrenurus spp.) was associated with reduced condition of males and with lowered fecundity of young females of the damselfly, Enallagma ebrium (Hagen) (Odonata: Coenagrionidae). We also demonstrate that degree of parasitism can covary with both age and size of host damselflies. We explain the putative causes of such natural covariation, and we suggest that degree of parasitism, host age, and host size can all interact to determine damselfly fitness. We expect that natural covariation between the host's phenotype and degree of parasitism will be frequently observed. Studies of such natural covariation will help researchers to assess better the importance of several variables on host reproductive success and to understand better the dynamics of host-parasite interactions.     

The adaptive significance of ontogenetic colour change in a tropical python

Ontogenetic colour change is typically associated with changes in size, vulnerability or habitat, but assessment of its functional significance requires quantification of the colour signals from the receivers' perspective. The tropical python, Morelia viridis, is an ideal species to establish the functional significance of ontogenetic colour change. Neonates hatch either yellow or red and both the morphs change to green with age. Here, we show that colour change from red or yellow to green provides camouflage from visually oriented avian predators in the different habitats used by juveniles and adults. This reflects changes in foraging behaviour and vulnerability as individuals mature and provides a rare demonstration of the adaptive value of ontogenetic colour change.     

An analysis of the phenotypic effects of certain colour pattern genes in Heliconius (Lepidoptera: Nymphalidae)

The colour patterns of Heliconius butterflies are built up from an array of serially homologous pattern elements known as the nymphalid groundplan. An analysis of the phenotypic effects of ten genetic loci from H. melpomene and H. cydno reveals that each alters the expression either of a single element of the groundplan or of an entire row of serially homologous elements. Five of the ten loci affect the size (or presence/absence) of specific pattern elements, two affect the colour in which a pattern element is expressed, two affect pattern-inducing activity of the wing veins, and one appears to affect an overall threshold for pattern determination. Three of the ten loci have identical effects on homologues of the fore- and hindwing. We show that most of the apparently large and qualitative phenotypic effects of these genes can be readily explained by relatively small and quantitative changes in the dimensions or positions of specific pattern elements.     

Differentiation of the body wall musculature in Macrostomum and Hoploplana (Turbellaria,Platyhelminthes)

Using the Phalloidin-Rhodamine flourescence-labelling technique for F-actin, we have studied the development of the body wall musculature in Macrostomum hystricinum marinum and in thepolyclad Hoploplana inquilina. The structure of the muscle grid in the freshly hatched Macrostomum (see also Rieger & Salvenmoser, 1991) and the young larva of Holplana served as reference systems for the embryonic development of the body wall musculature. In Macrostomum muscle fiber differentiation starts around 60% of developmental time between egg-laying and hatching, and in Hoploplana around 80% of embryonic development.In Macrostomum, early stages show TV-antenna-like arrangements of one longitudinal and several circular fibers. In Hoploplana our preliminary results show a particularly large, longitudinal fiber on either side of the body. These primary longitudinal fibers may serve as a founder cell for other longitudinal fibers and as spatial guides for the circular muscles. Similar founder cells have been reported during early muscle differentiation in leeches (Jellies & Kristan, 1988; Jellies, 1990). In Hoploplana, a special muscle system is present at the outset under the apical organ. It consists of what seems to be a spirally toranged fiber — when seen in head-on view — and of two additional fibers crossing this spiral, from the later developing posterior to the anterior lobe.TEM-studies of embryos of Macrostomum suggest that the longitudinal nerve cords represent an important guide during early differentiation of the pattern within the body wall musculature. Young stages of myoblasts can be identified along the main lateral nerve cord. Commonly, the myoblasts are seen to alternate with young neurons in their position along the nerve cord. Embryonic stages of Macrostomum hystricinum marinum were obtained from our cultures (Rieger et al., 1988). Immediately prior to fixation (Paraformaldehyde, Stephanini's fixative) the eggshells were punctured with tungsten needles. We noted some variability of developmental time for certain embryonic stages, which we cannot explain. Developmental stages of Hoploplana inquilina were collected at the Marine Biological Laboratory, Woods Hole, MA, USA according to the procedure outlined in Boyer (1987) and Boyer (1989). They have been timed in relation to normal developmental time to an early Müller's larva at about 100 hours.     

Alternative models for the development of the pattern of spaced heterocysts inAnabaena (Cyanophyta)

At least two plausible but very different mechanisms may underlie the de novo development of the pattern of spaced heterocysts inAnabaena. An experimental strategy is presented that should be able to determine whether one or the other of these mechanisms is incorrect.Dedicated to Prof. DrLothar Geitler on the occasion of his 90th birthday.     

A reconsideration of the genusRabdosiella (Lamiaceae,Nepetoideae, Ocimeae)

The two generaPlectranthus andIsodon are compared and found to be very dissimilar.Isodon ist considered to be misplaced inOcimeae subtribePlectranthinae and apparently is more closely related to subtribeHyptidinae. The disjunct genusRabdosiella is compared to these two genera and regarded to be polyphyletic. The AfricanR. calycina (Benth.)Codd is returned toPlectranthus and calledP. calycinusBenth., while the AsianR. ternifolia (D. Don)Codd is placed inIsodon sect.Pyramidium and calledI. ternifolius (D. Don)Kudo.     

Variation in the flash pattern of the firefly,Photuris versicolor quadrifulgens (Coleoptera: Lampyridae)

We sampled a population of signalingPhoturis versicolor quadrifulgens fireflies to quantify the variation in flash patterns emitted by males. Males produced five distinct flash patterns during their mate-searching flights. Four of the patterns consisted of two to five equal-intensity pulses and the fifth pattern type was a flicker, a group of rapid modulations in intensity. We found that the proportions of each pattern remained relatively constant from night to night throughout the season. The different flash patterns produced varied significantly with time of night; patterns having fewer pulses occurred earlier in the evening. Local density, an estimate of competition, did not significantly correlate with flash pattern type. On consecutive emissions, individuals changed their flash types with a mean probability of 0.12 (over all males), and they usually switched between patterns differing by a single pulse (from a two- to a three-pulse pattern, from a three- to a two-pulse pattern, etc.). The nightly temporal changes in flash patterns may be related to tradeoffs between female availability and energetic costs of signaling or the changes may be related to increased predation risk from visual predators.Photuris versicolor quadrifulgens was originally described by Barber (1951) as a subspecies ofP. versicolor. The genusPhoturis is currently under revision by Dr. James E. Lloyd, and this firefly will be given species status.     

Deletion analysis of the nitrogen fixation regulatory gene,nifL of Klebsiella pneumoniae

A number of in-frame deletions have been constructed in the Klebsiella pneumoniae regulatory gene nifL. The effects of each nifL mutation on NifA-mediated expression from the nifH promoter of K. pneumoniae have then been assessed with respect to both nitrogen and oxygen control. These experiments indicate that, in contrast to the situation with the homologous regulatory proteins NtrB and NtrC, NifA activity is not impaired in the absence of NifL. We conclude that the only function of NifL is to inactivate NifA in response to an increase in the nitrogen or oxygen status of the cell.     

Heterotrophic nitrogen fixation in oligotrophic tropical marshes: changes after phosphorus addition

In order to determine the impact of nutrient enrichment on phosphorus (P) limited wetlands, we established experimental P additions in marshes throughout northern Belize. P significantly increased macrophyte primary production, which led to the rapid elimination of cyanobacterial mats. The replacement of cyanobacterial mats by macrophytes constrained autotrophic nitrogen (N) fixation, increased the quantity, and changed the quality of organic matter input to the sediments. We predicted that the activity of sediment heterotrophic N fixers will be impacted by these alterations in carbon input. We used the acetylene reduction technique to measure potential (glucose amended) nitrogenase activity (NA) in sediments from controls and treatment plots that have been P enriched for four years and dominated either by Eleocharis cellulosa, or Typha domingensis for two years. NA in P-enriched plots was 2–3 orders of magnitude higher than NA in controls. NA was positively correlated with the soil reactive P, both total organic and microbial carbon, live root biomass, and total phospholipid fatty acids (PLFA) as an indicator of active microbial biomass. It was negatively correlated with the concentration of ammonium-N. Path analysis revealed that the indirect effect of P on NA through the root biomass was more important than the direct effect of P. NA of the upper sediment layer was consistently higher in Eleocharis than in Typha dominated plots, despite the higher litter input by Typha. We feel that the higher levels of lignin and phenolics occurring in Typha litter, relative to Eleocharis, constrained NA in Typha plots. Handling editor: Luis Mauricio Bini     

Notes on the biology of the freshwater planarian Dugesia bengalensis (Platyhelminthes Turbellaria Tricladida)

Dugesia bengalensis was described by Kawakatsu (Kawakatsu et al., 1983) from specimens collected in West Bengal. We have been studying populations from many different localities in Santiniketan and adjoining areas of West Bengal and can provide additional biological information.The species is hermaphroditic, and its breeding season was found to occur usually between October and March when the winter temperature falls below 25 °C. Outside of the breeding season, D. bengalensis is capable of asexual reproduction by binary fission (Mahapatra et al., 1987).Development of the reproductive organs appeared to be from neoblasts and other mesenchymal cells and, therefore, to be like that typical of other triclads with the exception that some of the neoblasts used for the reproductive tissue appeared to be derived from the intestinal region (Ghosh, 1988; cf. Teshirogi, 1986).During copulation, the partners were oriented in the same direction and not in a head-to-tail position as has been reported (Hyman, 1945) for some planarians.The oval, stalked cocoons were laid in marshy places, and during the period of summer (usually from April to June) they lay dormant in the sandy soil until the onset of the monsoon rains. Then, typically three or four months after they were laid, the cocoons hatched to yield three or four young, a remarkably low number for freshwater triclads (cf Ball & Reynoldson, 1981).