Tidal cycling and parental behavior of the cichlid fish,Biotodoma cupido

Synopsis Parental behavior of the substrate-brooding cichlid, Biotodoma cupido, was studied in a small creek entering the lower Essequibo River, Guyana, where the freshwaters are affected by semi-diurnal tides. Physico-chemical variables of the tidal cycle were associated with the parental behavior of B. cupido. During late ebb and early flood tides, while off-spring were nest dependent, parents displayed intense aggression toward brood predators, mainly characins. At low tide, when the concentration of dissolved oxygen decreased to about 4 mg 1^–1 and that of free carbon dioxide increased to 28 mg 1^–1, parents entered a state of somnolence and brood predators vanished. Early flood tide brought an immediate and dramatic reversal of hypoxic and hypercarbic conditions and an associated renewal of aggressive and predatory activity. At very low tide, parents orally transferred the brood to a secondary nest depression in deeper water. The significance of water-level fluctuation to the evolution of this behavior, as well as that of parent-brood itineracy and the related phenomena of oral incubation and movable nests, is discussed.     

A Sequential Scenario for the Origin of Biological Chirality

A sequential model is proposed regarding the origin of biological chirality. Three major stages are presumed: a symmetry breaking (prebiotic chiral disruption in enantiomeric mixtures of monomers), a chiral amplification (prebiotic increase of the chiral character of the monomers affected first by the symmetry breaking), and a chiral expansion (proto biological increase of the chiral character and spread of the chirality to molecules which were less affected by prebiotic chiralizations). As a symmetry-breaking mechanism, the model proposed by Deutsch (1991) is used, which involves a dissymmetric exposure of amino acids (AA) to ultraviolet circularly polarized light (UV-CPL) on evaporative seashores. It is presumed that the chiral amplification, up to a protobiologic significance, was influenced by a periodic overlapping of two abiotic events, a synchronization between tidal-based hydrous–anhydrous cycles, and littoral asymmetric photolysis cycles. This long-term astronomic asymmetry acted around 3.8–4.2 billion years ago and was unique to the Earth in our solar system. It is also presumed that the abiotic symmetry breaking is heterogenous, that only a few l-AAs were used in the beginning, and that the chirality expanded later to all 20 AAs based on a coevolutionary strategy of the genetic code and on a physiological relationship between AAs. In this scenario the d-chirality of pentoses in polynucleotides was attributed to both d-pentose/l-AA relationships and to a structural evolution. Received: 10 May 1996 / Accepted: 13 August 1996     

The lack of changes in nocturnal estuarine fish assemblages between new and full moon phases in Serpentine Creek,Queensland

Synopsis A series of 10 sites were sampled at new and full moon phases in a vertically homogenous estuary, Serpentine Creek, Queensland, Australia. Forty-five species (14,518 individuals) were caught and analysed using standardized Shannon & Gleason diversity indices, and total number of species and individuals. The coefficients of variation for these values were greater for times than for sites. There were no significant differences between 14 pairs of new and full moon phases for_t,_t,_t, and_t, or between mean number of individuals for the 16 most abundant species. If significant variations do exist within months, then experiments should be done between spring and neap tides as this study found no differences between the spring tides associated with new and full moon phases.     

Temporal and spatial pattern of common tern (Sterna hirundo) foraging in the Wadden Sea

In 1989, 313 foraging flights of common terns in the Wadden Sea were radio-tracked. The feeding trips lasted on average 115 min covering about 30 km per flight. Completely tracked flights had a mean radius of 6.3 km. The terns preferred distinct foraging areas in the Wadden Sea. These were visited at site-specific phases of the tidal cycle resulting in a temporal and spatial pattern of foraging, caused by the site-specific and tide-related fluctuations of food availability.Supported by the Deutsche Forschungsgemeinschaft     

An Appraisal of Tidal Activity Rhythms

Organisms of the marine littoral zone experience a much wider range of periodicities in their environment than do their terrestrial counterparts. Tidal cycles of semidiurnal, diurnal, lunar, and semilunar frequencies may all recur at the same locality, in addition to the diel cycle of light and darkness. The relationship of endogenous activity patterns to the prevailing geophysical variables thus poses problems for the temporal organization of the organism. The way in which intertidal animals synchronize their behaviour and physiology to such a diversely fluctuating environment, and the efficacy of different environmental factors as entraining agents is considered. Evidence pertaining to the endogenous control mechanisms, both physiological and behavioural, is reviewed, and the organization of the endogenous time-keeping system discussed in terms of identifiable oscillators of different frequencies.     

Lunar periodicity in the spawning of yellowtail damselfish,Microspathodon chrysurus

Synopsis The reproductive behavior of yellowtail damselfish,Microspathodon chrysurus, was studied off the Caribbean coast of Panama to determine if there is a lunar spawning cycle. Male damselfish prepare nest sites on dead coral surfaces within their permanent feeding territories. Spawning occurs at sunrise and lasts for approximately one hour. Males defend the eggs until hatching, which occurs before the morning of the sixth day of incubation. Males spawn only once a day, but may spawn many times within each reproductive phase. Reproductive activity is highest in the time periods from full to new moon. The timing of this lunar cycle differs from those reported for other marine fishes. The spawning pattern is not consistent with common explanations for lunar periodicity that are based on the role of tides or moonlight. Some implications of these results for the organization of tropical reef communities are discussed.     

Rocky shore zonation in the Ranee tidal power basin

Data from a series of rocky shore transects, within the enclosed basin of the Ranee estuary and immediately outside the barrage, describe the distribution and zonation patterns of the intertidal biota, after more than a decade of its regular operation as a tidal power station. In the absence of quantitative pre-barrage information, the distribution of species has been compared with published information on their former extent of penetration into the estuary.     

Tidal influence on the evolution of egg size in the grunions (Leuresthes,Atherinidae)

Synopsis The duration of natural in-beach-sand incubation of Gulf of California and California grunion embryos is dictated by the tidally-driven wave activity in their respective habitats. Analyses of these tidal regimes reveal that the incubation period can be three times longer on beaches of the California coast than on those of the northern Gulf.In response to the more irregular tides of California, Leuresthes tenuis, the less primitive of the two species, has evolved an egg volume 310% larger than the Gulf grunion, L. sardina. The. larger egg not only supplies greater yolk reserves for differentiation, growth and maintenance, but also produces a larger embryo. The more abundant yolk stores and greater embryo size helps California grunion embryos to remain viable in the sand longer than those of the Gulf grunion.     

Water level and currents of tidal and infragravity periods at Tague Reef, St. Croix (USVI)

A two-week study, at Tague Reef, St. Croix, USVI investigated the magnitude and spatial variation of tides, sea level differences, infragravity waves, and unidirectional cross-reef currents on a modern coral reef. Infragravity oscillations of water level (∼ 27 min period) of 1–2 cm height correlate with a quarter wavelength resonance over the shelf. Particle displacements associated with these waves may be important to the dispersive characteristics of the reef environment. Estimates of cross-reef mass transport per unit width ranged from 0.058 to 0.032 m²s ^-1. Sea level differences across the reef (1–4 cm) varied at diurnal and infragravity periods with contributions from wave set-up, and a small contribution from cross-shelf wind stress to the observed sea level differences. The quadratic bottom friction coefficient over the reef was estimated at 0.06–0.2, 20–70 times greater than on open shelves, reflecting the reef’s extreme bottom roughness. Accepted: 28 February 1998