A lunar clock changes shielding pigment transparency in larval ocelli of Clunio marinus

Living in the tidal zones of the sea requires synchronization with the dominant environmental influences of tidal, solar, and lunar periodicity. Endogenous clocks anticipate those geoclimatic changes and control the respective rhythms of vital functions. But the underlying mechanisms are only partly understood. While the circadian clocks in animals are investigated employing neurobiological, molecular, and genetic approaches, clocks with a lunar periodicity have been studied with reference to development and behavior only. Sites of their pacemakers, zeitgeber receptors, and coupled endocrine components are unknown. Here, a lunar-rhythmic change of shielding pigment transparency in the larval ocelli of the intertidal midge Clunio marinus is demonstrated for the first time as a possible access to the neurobiology of lunar timing mechanisms. We studied third instar larvae (Vigo strain) throughout the lunar cycle by light- and electron-microscopy as well as by x-ray fluorescence analysis for the identification of the pigment. Moonlight detection is a prerequisite for photic synchronization of the lunar clock. The larval ocelli of Clunio putatively may function as moonlight receptors and are also controlled by the circalunar clock itself, hence being primary candidates for tracing input and output pathways of the lunar pacemaker. Additionally, the demonstration of a reversible optical change of shielding pigment transparency in Clunio is a novel finding, not reported so far in any other animal species, and reveals a mechanism to enhance photosensitivity under the condition of very dim light. It represents a remarkable change of a sense organ from an imaging device to a radiometer. Its restriction to the developmental stage susceptible to lunar timing elucidates a unique sensory strategy evolved at the level of sensory input. It also raises basic questions about the biochemistry of optically active pigments, like melanin, and their intracellular control.     

Reproductive cycles in tropical intertidal gastropods are timed around tidal amplitude cycles

Reproduction in iteroparous marine organisms is often timed with abiotic cycles and may follow lunar, tidal amplitude, or daily cycles. Among intertidal marine invertebrates, decapods are well known to time larval release to coincide with large amplitude nighttime tides, which minimizes the risk of predation. Such bimonthly cycles have been reported for few other intertidal invertebrates. We documented the reproduction of 6 gastropod species from Panama to determine whether they demonstrate reproductive cycles, whether these cycles follow a 2‐week cycle, and whether cycles are timed so that larval release occurs during large amplitude tides. Two of the species (Crepidula cf. marginalis and Nerita scabricosta) showed nonuniform reproduction, but without clear peaks in timing relative to tidal or lunar cycles. The other 4 species show clear peaks in reproduction occurring every 2 weeks. In 3 of these species (Cerithideopsis carlifornica var. valida, Littoraria variegata, and Natica chemnitzi), hatching occurred within 4 days of the maximum amplitude tides. Siphonaria palmata exhibit strong cycles, but reproduction occurred during the neap tides. Strong differences in the intensity of reproduction of Cerithideopsis carlifornica, and in particular, Littoraria variegata, between the larger and smaller spring tides of a lunar month indicate that these species time reproduction with the tidal amplitude cycle rather than the lunar cycle. For those species that reproduce during both the wet and dry seasons, we found that reproductive timing did not differ between seasons despite strong differences in temperature and precipitation. Overall, we found that most (4/6) species have strong reproductive cycles synchronized with the tidal amplitude cycle and that seasonal differences in abiotic factors do not alter these cycles.     

Genetic adaptation in emergence time ofClunio populations to different tidal conditions

Summary 1. The emergence times of intertidalClunio-species (Diptera, Chironomidae) are correlated with special tidal conditions in such a way that the immediately following reproduction of the short-lived imagos can take place on the exposed habitat.2. If the habitat of aClunio-species is situated in the middle tidal region and exposed twice a day by the tidal cycle (T = 12.4 h), a tidal rhythm of emergence with an average period of 12.4 hours may result (example:Clunio takahashii).3. If the habitat is located in the lower tidal zone, exposed only at about the time of the spring tides, a semilunar rhythm of emergence is expected (examples:Clunio marinus andClunio mediterraneus). These semilunar rhythms are correlated with certain conditions of low tide which occur at the coastal locations every 15 days at about the same time of day. The semilunar rhythm is therefore exactly characterized by two dates: the lunar emergence time (a few successive days around full and new moon) and the diurnal emergence time.4. According to experimental investigations on the control of the emergence rhythm, the midges are able to determine both dates in advance.5. Coastal populations differ in their lunar and diurnal emergence times. These differences correspond to the time of low tide which exists at each location during the emergence days of the semilunar rhythm.6. Crossbreeding between stocks of different populations showed that the differences in diurnal emergence time are gene-controlled.

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Genetische Adaptation der Schlüpfzeiten vonClunio-Populationen an verschiedene Gezeitenbedingungen

Kurzfassung Die Schlüpfzeiten der in der Gezeitenzone lebendenClunio-Arten (Diptera, Chironomidae) sind mit bestimmten Wasserstandsbedingungen synchronisiert, und zwar derart, daß die unmittelbar anschließende Fortpflanzung der kurzlebigen Imagines auf dem trockengefallenen Habitat stattfinden kann. Wenn das Habitat einerClunio-Art in der mittleren Gezeitenzone liegt und parallel zu dem halbtägigen Gezeitenzyklus (T = 12,4 h) zweimal täglich auftaucht, dann kann sich eine 12,4stündige Schlüpfperiodik einstellen (Beispiel:Clunio takahashii). Wenn das Habitat in der unteren Gezeitenzone liegt und nur um die Zeit der Springtiden auftaucht, dann ist eine 15tägige (semilunare) Schlüpfperiodik zu erwarten (Beispiele:Clunio marinus undC. mediterraneus). Diese 15tägige Schlüpfperiodik ist synchronisiert mit bestimmten Niedrigwasserbedingungen, die an einem Küstenort alle 15 Tage jeweils um die gleiche Tageszeit auftreten. Sie wird daher durch zwei Daten eindeutig gekennzeichnet: (1) die lunaren Schlüpftage (wenige aufeinanderfolgende Tage um Voll- und Neumond) und (2) die tägliche Schlüpfzeit. Wie experimentelle Untersuchungen über die Steuerung der Schlüpfperiodik zeigten, können die Tiere beide Daten richtig vorausbestimmen. Die einzelnen Küstenpopulationen unterscheiden sich allerdings in Anpassung an die örtlichen Gezeiten- und Standortbedingungen recht auffällig in ihren lunaren und täglichen Schlüpfzeiten. Kreuzungsversuche zwischen Laboratoriumsstämmen verschiedener Populationen belegen, daß die Unterschiede in der täglichen Schlüpfzeit genkontrolliert sind.

     

Larval release rhythms and tidal exchange in the estuarine mudprawn, Upogebia africana

The mudprawn, Upogebia africana is common in intertidal regions of many South African estuaries. The life cycle is complex, incorporating a marine phase of development during the larval stages. Breeding peaks are in summer and first-stage larvae are released into the plankton at night. Maximum release activity and export to the marine environment follow a semi-lunar cycle synchronized to the time when high water in the estuary is crepuscular. This occurs after peak spring tidal amplitude. Estuarine reinvasion by postlarvae is also nocturnal, and maximum return occurs after neap's when low water at sea occurs around sunset. Rhythmic cycles of larval export and postlarval estuarine reinvasion are therefore asynchronous during the lunar cycle and are best explained by the timing of the change in light intensity relative to high and low water respectively. If maximum activity rhythms of Stage 1 and postlarvae are independent of tidal amplitude, then timing of maximum release and reinvasion during the lunar cycle would alter as the time of sunset shifts between solstices. Much of southern Africa experiences a semi-arid type climate and most estuaries close off from the sea for varying periods owing to sandbar development across tidal inlets. Larvae do not metamorphose if trapped in estuaries and recruitment ceases. Thus, mudprawn populations are directly affected by tidal inlet dynamics. In extreme cases populations become locally extinct if inlets remain closed for extended periods.     

Diel and lunar spawning periodicity of the hawkfish Paracirrhites forsteri (Cirrhitidae) on the reefs of Kuchierabu-jima Island, southern Japan

We observed spawning behavior of the hawkfish Paracirrhites forsteri on reefs of southern Japan. Spawning generally occurred after sunset, prior to the full and new moon with semi-lunar spawning peak periodicity. No egg predation was observed in spawning after sunset, and high tide often occurred at dusk in the lunar phases. Thus, diel timing and lunar synchronicity may increase larval survival. We found that the mating activity tended to start earlier in the day during early mating season than during mid-to-late mating season. The advantages of the earlier start of mating activity were also examined in relation to adult biology contexts.     

Ultrastructural investigations of presumed photoreceptive organs in two Saccocirrus species (polychaeta,saccocirridae)

In addition to the pigmented ocelli, four different types of photoreceptor-like organs without shading pigment have been found in Saccocirrus papillocercus and S. krusadensis. The sensory cells of these presumed ocelli are either ciliary or rhabdomeric with ciliary rudiments. With the exception of the multicellular type-2 ocelli they are bicellular consisting of a sensory cell and a supportive cell. In each ocellus the supportive cell forms a thin cup-shaped envelope around the sensory elements. In the type-2 ocellus, 7 supportive cells form an ovoid cavity leaving openings through which dendritic processes of an equal number of sensory cells enter the cavity. The pigmented ocelli possess an ocellar cavity communicating with the exterior through a pore in the eyecup, ciliary rudiments in both sensory and supportive cell, and additional non-photoreceptive sensory cells in the opening of the eyecup. The sensory organs show characteristic differences between the two species, such as presence or absence of a particular type of ocellus (type 2 is absent in S. krusadensis, type 3 in S. papillocercus), number of cilia in type-4 ocelli, density of microvilli, number of non-photoreceptive sensory cells in the pore of the pigmented ocellus, etc. These differences provide important characters which can be used for discrimination either of species or of subgeneric taxa in Saccocirrus. The phylogenetic significance of the different photoreceptive organs is discussed.     

MODELING ACTIVITY RHYTHMS IN FIDDLER CRABS

Burrowing crabs of the genus Uca inhabit tidal mudflats and beaches. They feed actively during low tide and remain in their burrows when the tide is high. The timing of this activity has been shown to persist in the absence of external light and tidal cues, indicating the presence of an internal timing mechanism. Researchers report the persistence of several variations in locomotor activity under laboratory conditions that cannot be explained by a single circatidal clock. Previous studies supported two alternative hypotheses: the presence of either two circalunidian clocks, or a circadian and circatidal clock to regulate these activity rhythms. In this paper, we formulate mathematical models to describe and test these hypotheses. The models suggested by the literature contain some important differences beyond the frequency of proposed clocks, and these are reflected in the mathematical formulations and simulation results. One hypothesis suggests independent phase oscillators, while the other hypothesis suggests that they are coupled in anti-phase. Neither model is able to recover all of the variations in locomotor acitivity observed under laboratory conditions. However, we propose a new model that incorporates aspects of both existing hypotheses and is able to reproduce all laboratory observations. (Author correspondence: verzi@math.sdsu.edu)     

The Nymphal Eyes of Parabuthus transvaalicus Purcell, 1899 (Buthidae): An Accessory Lateral Eye in a Scorpion

In P. transvaalicus nymphs, 5 pairs of lateral ocelli each composed of a corneal lens, R-cell units forming a latticed rhabdom, arhabdomeric cells and pigment cells are present. In addition, we found a pair of unpigmented accessory sense organs situated ventroposteriorly to the lateral ocelli in prenymphs as well as in first nymphs. They are composed of primary, rhabdomeric sensory cells, and we infer that they represent a second type of lateral eye. They also comprise sensory units, but lenses and screening pigment are lacking. Their position and cellular architecture corresponds well with that of the “rudimentary” lateral eye of the xiphosuran, Limulus. The occurrence of a bipartite lateral visual system in Chelicerata and Arthropoda is discussed.     

Casein kinase 2, circadian clocks, and the flight from mutagenic light

Circadian clocks play a fundamental role in biology and disease. Much has been learned about the molecular underpinnings of these biological clocks from genetic studies in model organisms, such as the fruit fly, Drosophila melanogaster. Here we review the literature from our lab and others that establish a role for the protein kinase CK2 in Drosophila clock timing. Among the clock genes described thus far, CK2 is unique in its involvement in plant, fungal, as well as animal circadian clocks. We propose that this reflects an ancient, conserved function for CK2 in circadian clocks. CK2 and other clock genes have been implicated in cellular responses to DNA damage, particularly those induced by ultraviolet (UV) light. The finding of a dual function of CK2 in clocks and in UV responses supports the notion that clocks evolved to assist organisms in avoiding the mutagenic effects of daily sunlight.     

Die Temperaturabhängigkeit semilunarer und diurnaler Schlüpfrhythmen bei der intertidalen MückeClunio marinus (Diptera,Chironomidae)

On Helgoland (North Sea), the imagines ofClunio emerge during two seasonal periods (late spring and summer) from water temperatures of 8°–18 °C. The temperature dependence of the known semilunar eclosion rhythm ofClunio (correlated in nature with the spring tides every 14–15 days) was tested in the laboratory. Between 15° and 23 °C the semilunar eclosion maxima varied by only one day within the artifical 15-day zeitgebercycle, below 15 °C they were delayed up to 8 days at 8 °C. However, the days of pupation were approximately independent of the temperature level. One can conclude the existence of a temperature-independent physiological switch inducing the pupation only within a few days of the semilunar zeitgeber-cycle. Moreover, a semilunar synchronized differentiation of the imaginal discs already starts in the preceding larval instar, indicating an additional physiological switch. A model is suggested in which the semilunar eclosion rhythm and its relatively slight temperature dependence is explained by the action of two physiological switches which are coupled with the endogenous temperature-compensated lunar timing mechanism on the same days of the 15-day zeitgeber-cycle. In the laboratory, the diurnal eclosion and its underlying circadian timing mechanism (correlated on Helgoland with the time of spring low water in the late afternoon) also proved to be temperature independent between 12° and 20 °C. A comparison of field and laboratory data showed very similar results at temperatures around 18 °C (summer swarming period). In contrast, the midges emerged on all days of the semimonthly cycle of springs and neaps during the spring swarming period. This lack of semilunar synchronization may be the consequence of fluctuating temperatures during the larval and pupal development in spring time due to a general rise in the water temperature (4°–8 °C) and to short temperature rises up to 18 °C during exposure of the intertidal habitat at about low tide. Since some higher parts of theClunio habitat suitable for egg deposition are exposed on almost every day of the semimonthly cycle, even such animals that undergo lunar unsynchronized metamorphosis can reproduce within the short imaginal life duration (ca 2 h) if they emerge just about the time of low water. In correspondence with the daily delay in the times of low water by about 50 min, the diurnal eclosion rhythm was in fact modified with the tides during the spring period resulting in shifts of the diurnal eclosion time of up to 12 hours within the semimonthly cycle of springs and neaps.     

Genetic architecture of local adaptation in lunar and diurnal emergence times of the marine midge Clunio marinus (Chironomidae, Diptera)

Circadian rhythms pre-adapt the physiology of most organisms to predictable daily changes in the environment. Some marine organisms also show endogenous circalunar rhythms. The genetic basis of the circalunar clock and its interaction with the circadian clock is unknown. Both clocks can be studied in the marine midge Clunio marinus (Chironomidae, Diptera), as different populations have different local adaptations in their lunar and diurnal rhythms of adult emergence, which can be analyzed by crossing experiments. We investigated the genetic basis of population variation in clock properties by constructing the first genetic linkage map for this species, and performing quantitative trait locus (QTL) analysis on variation in both lunar and diurnal timing. The genome has a genetic length of 167-193 centimorgans based on a linkage map using 344 markers, and a physical size of 95-140 megabases estimated by flow cytometry. Mapping the sex determining locus shows that females are the heterogametic sex, unlike most other Chironomidae. We identified two QTL each for lunar emergence time and diurnal emergence time. The distribution of QTL confirms a previously hypothesized genetic basis to a correlation of lunar and diurnal emergence times in natural populations. Mapping of clock genes and light receptors identified ciliary opsin 2 (cOps2) as a candidate to be involved in both lunar and diurnal timing; cryptochrome 1 (cry1) as a candidate gene for lunar timing; and two timeless (tim2, tim3) genes as candidate genes for diurnal timing. This QTL analysis of lunar rhythmicity, the first in any species, provides a unique entree into the molecular analysis of the lunar clock.     

HABITAT DIFFERENCES IN THE TIMING OF REPRODUCTION OF THE INVASIVE ALGA SARGASSUM MUTICUM (PHAEOPHYTA,SARGASSACEAE) OVER TIDAL AND LUNAR CYCLES1

Sargassum muticum (Yendo) Fensholt is an invasive species that is firmly established on intertidal and subtidal rocky shores of Europe and the Pacific coast of North America. Local success and spread of S. muticum is thought to rely on its reproductive potential that seems dependent on exogenous factors like tidal and lunar cycles. This study is the first to compare the reproductive patterns (periodicity of egg expulsion and embryo settlement) of this invader in two different habitats: the middle and low intertidal. The combination of monthly, daily, and tidal samples at triplicate sites within each habitat showed a semilunar periodicity of egg expulsion and embryo settlement coincident with increasing tidal amplitude just before full and new moons. In both habitats, duration of each egg expulsion event was ～1 week, and embryo settlement occurred during the first daily low tide and with the incoming high tide during spring tides. However, both expulsion and settlement started 1–2 d earlier, expulsion saturation was faster, and settlement was higher in the mid‐ compared to the low intertidal. Our results suggest that the exact timing of gamete expulsion and embryo release of S. muticum responds to local factors, including tidal cues, which result in differences between mid‐ and low‐intertidal habitats.     

Elevated Temperature Alters the Lunar Timing of Planulation in the Brooding Coral Pocillopora damicornis

Reproductive timing in corals is associated with environmental variables including temperature, lunar periodicity, and seasonality. Although it is clear that these variables are interrelated, it remains unknown if one variable in particular acts as the proximate signaler for gamete and or larval release. Furthermore, in an era of global warming, the degree to which increases in ocean temperatures will disrupt normal reproductive patterns in corals remains unknown. Pocillopora damicornis, a brooding coral widely distributed in the Indo-Pacific, has been the subject of multiple reproductive ecology studies that show correlations between temperature, lunar periodicity, and reproductive timing. However, to date, no study has empirically measured changes in reproductive timing associated with increased seawater temperature. In this study, the effect of increased seawater temperature on the timing of planula release was examined during the lunar cycles of March and June 2012. Twelve brooding corals were removed from Hobihu reef in Nanwan Bay, southern Taiwan and placed in 23 and 28°C controlled temperature treatment tanks. For both seasons, the timing of planulation was found to be plastic, with the high temperature treatment resulting in significantly earlier peaks of planula release compared to the low temperature treatment. This suggests that temperature alone can influence the timing of larval release in Pocillopora damicornis in Nanwan Bay. Therefore, it is expected that continued increases in ocean temperature will result in earlier timing of reproductive events in corals, which may lead to either variations in reproductive success or phenotypic acclimatization.     

The larval ocelli of Golfingia misakiana (Sipuncula, Golfingiidae) and of a pelagosphera of another unidentified species

 The inverse cerebral ocelli of the pelagosphera larva of Golfingia misakiana and of another unidentified larva are composed of two or three sensory cells and one supportive pigmented cell. The sensory cells bear an array of microvilli as well as a single cilium with poor undulation of its membrane; the photoreceptive organelles are regarded as the rhabdomeric type. A striking feature of these cells is the cores, which extend within the microvilli from the tip into the midregion of the cell. It is suggested that these structures are identical with the submicrovillar cisternae found in the cerebral inverse eyes of larvae of Polychaeta. The findings allow the conclusion that in the pelagosphera of the Sipuncula, contrary to the teleplanic veliger larvae of Gastropoda, a lengthy pelagic cycle is not correlated with the development of a ciliary photoreceptor. Additionally, it is assumed that the pigment cup ocelli in larvae of Sipuncula are homologous with the cerebral inverted pigment cup ocelli of larvae of Polychaeta. Accepted: 19 March 1997     

The Pyrexia transient receptor potential channel mediates circadian clock synchronization to low temperature cycles in Drosophila melanogaster

Circadian clocks are endogenous approximately 24 h oscillators that temporally regulate many physiological and behavioural processes. In order to be beneficial for the organism, these clocks must be synchronized with the environmental cycles on a daily basis. Both light : dark and the concomitant daily temperature cycles (TCs) function as Zeitgeber (‘time giver’) and efficiently entrain circadian clocks. The temperature receptors mediating this synchronization have not been identified. Transient receptor potential (TRP) channels function as thermo-receptors in animals, and here we show that the Pyrexia (Pyx) TRP channel mediates temperature synchronization in Drosophila melanogaster. Pyx is expressed in peripheral sensory organs (chordotonal organs), which previously have been implicated in temperature synchronization. Flies deficient for Pyx function fail to synchronize their behaviour to TCs in the lower range (16–20°C), and this deficit can be partially rescued by introducing a wild-type copy of the pyx gene. Synchronization to higher TCs is not affected, demonstrating a specific role for Pyx at lower temperatures. In addition, pyx mutants speed up their clock after being exposed to TCs. Our results identify the first TRP channel involved in temperature synchronization of circadian clocks.     

Potent synchronization of peripheral circadian clocks by glucocorticoid injections in PER2::LUC-Clock/Clock mice

In mammals, the central clock (the suprachiasmatic nuclei, SCN) is entrained mainly by the light-dark cycle, whereas peripheral clocks in the peripheral tissues are entrained/synchronized by multiple factors, including feeding patterns and endocrine hormones such as glucocorticoids. Clock-mutant mice (Clock/Clock), which have a mutation in a core clock gene, show potent phase resetting in response to light pulses compared with wild-type (WT) mice, owing to the damped and flexible oscillator in the SCN. However, the phase resetting of the peripheral clocks in Clock/Clock mice has not been elucidated. Here, we characterized the peripheral clock gene synchronization in Clock/Clock mice by daily injections of a synthetic glucocorticoid (dexamethasone, DEX) by monitoring in vivo PER2::LUCIFERASE bioluminescence. Compared with WT mice, the Clock/Clock mice showed significantly decreased bioluminescence and peripheral clock rhythms with decreased amplitudes and delayed phases. In addition, the DEX injections increased the amplitudes and advanced the phases. In order to examine the robustness of the internal oscillator, T-cycle experiments involving DEX stimulations with 24- or 30-h intervals were performed. The Clock/Clock mice synchronized to the 30-h T-cycle stimulation, which suggested that the peripheral clocks in the Clock/Clock mice had increased synchronizing ability upon DEX stimulation, to that of circadian and hour-glass type oscillations, because of weak internal clock oscillators.     

Astronomically controlled deep-sea life in the Late Cretaceous reconstructed from ultra-high-resolution inoceramid shell archives

The periodicity of the mutual position of celestial bodies in the Earth-Moon-Sun system is crucial to the functioning of life on Earth. Biological rhythms affect most of the processes inside organisms, and some can be recorded in skeletal remains, allowing one to reconstruct the cycles that occur in nature deep in time. In the present study, we have used ultra-high-resolution elemental ratio scans of Mg/Ca, Sr/Ca and Mn/Ca from the fossil, ca. 70 Ma old inoceramid bivalve Inoceramus (Platyceramus) salisburgensis from deep aphotic water and identified a clear regularity of repetition of the geochemical signal every of ~0.006 mm. We estimate that the shell accretion rate is on average ~0.4 cm of shell thickness per lunar year. Visible light–dark lamination, interpreted as a seasonal signal corresponding to the semilunar-related cycle, gives a rough shell age estimate and growth rate for this large bivalve species supported by a dual feeding strategy. We recognize a biological clock that follows either a semilunar (model A) or a tidal (model B) cycle. This cycle of tidal dominance seems to fit better considering the biological behaviour of I. (P.) salisburgensis, including the estimated age and growth rate of the studied specimens. We interpret that the major control in such deep-sea environment, well below the photic zone and storm wave base, was due to barotropic tidal forces, thus changing the water pressure.     

Ocelli in a Cnidaria polyp: the ultrastructure of the pigment spots in Stylocoronella riedli (Scyphozoa,Stauromedusae)

Within the Cnidaria, the occurrence of ocelli at the polyp stage is only known in the species of Stylocoronella (Scyphozoa, Stauromedusae). The light-sensitive organs of S. riedli are ultrastructurally investigated. In this interstitial-living species, each of the up to 24 ocelli is composed of between seven and nine monociliary sensory cells and between one and four pigment cells. A striking feature of the photoreceptive cilia is their peculiar axonemal pattern. This is expressed (a) by the presence of a third central microtubule at a certain point and (b) by the balloon-like swelling of the distal portion of the cilium, with clearly scattered microtubules in this area. Although the polyps of S. riedli show no distinct reaction to light stimuli, the ultrastructural results corroborate the hypothesis that these organs are light-sensitive organs. The possible function of the pigment granules is discussed.Abbreviations bb basal body - c cilium - co collar - csv crescent-shaped vesicle - cv clear vesicle - dcv dense-core vesicles - k kinetosome - m mitochondrion - mvb multivesicular body - n nucleus - oc ocellus - pc piment cell - pg pigment granule - sc sensory cell - sr striated rootlet - v vesicle