Effects of Macroposthonia xenoplax on the Growth of Concord Grape

Concord grape (Vitis labrusca) plants were inoculated with Macroposthonia xenoplax at levels of 100, 1,000, and 10,000 nematodes. After 4 months, plants inoculated with 10,000 M. xenoplax were stunted, and root systems were darker and had fewer feeder roots than those in other treatments. The lower nematode inoculation levels suppressed top growth but did not affect root growth. M. xenoplax reproduced well on Concord grapes.     

CULTURE AND HYBRIDIZATION STUDIES ON GIGARTINA PAPILLATA (RHODOPHYTA)1

The foliose red alga Gigartina papillata (C. Ag.) J. Ag. was studied in culture to determine its life history and possible relationship to the life history of Petrocelis middendorffii (Ruprecht) Kjellman. Carpospores cultured from individual female plants gave rise to either crustose Petrocelis-like plants that reproduced by tetraspores, or to another generation of foliose female (cystocarpic) plants that reproduced by carpospores. Apices cultured from blades of individual field-collected female plants produced either papillae with many procarps that developed cystocarps only when crossed with male plants, or papillae with few procarps that produced cystocarps in the absence of male plants. The results are interpreted to demonstrate that two types of life history occur in G. papillata: one, a sexual life history involving a crustose tetrasporophyte; the other, a possibly apomictic life history involving only cystocarpic plants. Hybridization experiments demonstrated, that G. papillata is interfertile with Gigartina-phase gametophytes cultured from tetraspores of P. middendorffii. Sexual plants of G. papillata are postulated to represent the naturally-occurring gametophyte of P. middendorffii in California. The possible relationships of the sexual and apomictic plants of G. papillata are discussed.     

CULTURE STUDY OF REPRODUCTIVE CYCLES AND SYSTEMATICA IN MOUGEOTIA TRANSEAUI (CHLOROPHYTA)1,2

Asexual and sexual reproductive cyries are described and illustrated for a cultured homothallic strain of Mougeotia transeaui Collins. Reproduction is by aplanospores and zygospores. Aplanospore formation precedes zygospore formation and continues longer with regreening of older cultures occurring regularly from precocious germination of aplanospores. Aplanospores typically form when most of the protoplast moves into the central swollen region of a cell and two new cross walls form to delimit an aplanosporangium. Conjugation is scalariform without the movement and fusion of well-organized gametes. During zygospore maturation, three new cross walls form in the receptive gametangium and conjugation tube to produce a zygosporangium.     

Preliminary observations on reproduction in the Central American agouti,Dasyprocta punctata

Two adult male and three adult female agoutis have been reproducing at the Lincoln Park Zoo since 1978. Agoutis of the species D. punctata and D. fuliginosa are capable of breeding and producing offspring in every month of the year in captivity. The minimum interbirth interval of captive punctata is 127 days, and its gestation period is apparently less than 127 calendar days. In captivity, agoutis are likely to produce multiple offspring.     

Spawning of hermatypic corals in Bermuda: a pilot study

This study investigates spawning of 4 hermatypic coral species from the subtropical environment of Bermuda. Laboratory evidence of spawning behaviour is supported by synchronous field observations. Development of scleractinian planulae to postlarval stages is recorded. Diploria strigosa, D. labyrinthiformis, Montastrea annularis and M. cavernosa shed highly buoyant, pigmented eggs (300–440 µm diam.) during July to September 1986. Brief spawning periods, synchronous between conspecific colonies, were recorded for M. annularis (July and August) and M. cavernosa (August) within 1 d of the last quarter of the lunar cycle. In August, there were overlaps amongst the spawning dates of D. strigosa and the Montastrea species. Nocturnal spawning periods differed between M. annularis and M. cavernosa. This constitutes the first evidence from an Atlantic community of overlapping spawning dates amongst several faviid species, and of the accumulation of scleractinian eggs and planulae in surface slicks.     

Genetic alleviation of the self-fertilization complication when hybridizing monoecious Gelidium vagum

Fundamental genetic studies were initiated for the monoecious red alga Gelidium vagum. Color and sterility mutants were isolated and characterized to provide genetic tools, initially to identify hybrid plants when they occurred in crosses, and secondarily to eliminate self-fertilization altogether. When fertility phenotypes were scored, rapid onset of reproduction in culture was favored by long day-length, moderately high irradiance levels from fluorescent lights, warm temperature and the addition of Tris buffer to the medium. A recessive green mutant (designated grn 1) was characterized and used in subsequent crosses to allow a clear distinction between non-hybrid (green) and hybrid (red) offspring. Additional color mutants and a variety of reproductive mutants were also isolated and characterized. Male-sterile mutants had phenotypes ranging from apparently normal plants to those that produced no spermatia. Female-sterile mutants also included a variety of phenotypes, some plants having post-fertilization malfunctions during the development of the carposporophyte. Only a fraction of the sterility mutations have been phenotypically or genetically characterized, but some are straightforwardly inherited as stable, nuclear, single-gene defects. From the genetic recombination pattern, one female-sterile mutant may be loosely linked (39 cMorgans) to the grn 1 marker gene. Male sterility very effectively eliminated selfing without affecting the production of carpospores in crosses, thereby overcoming one of the most serious genetic difficulties in working with this monoecious species.     

The adaptive pattern of growth and reproduction of the colonial hydroid Clavopsella michaeli

The effects of variations in temperature, salinity and water movement on the laboratory growth and reproduction of a single clone of the bougainvilliid hydroid Clavopsella michaeli were examined. Unfavourable conditions resulted in reproducible oscillations of growth rate. They ranged from overall stimulatory effects (hormesis) to irreversible inhibition and shrinkage of colonies. Exposure to low concentrations (0.1–5 µg l^–1) of copper and mercury ions produced similar responses, which were therefore regarded as non-specific. A control mechanism, dampening these growth rate oscillations, supported higher colonial tolerance, that is adaptation, to environmental stresses of low intensity. When the counteractive capacity of the control mechanism was exceeded, inhibition occurred. Higher frequencies of gonozooids were observed in stressed colonies and were interpreted as an adaptive response.     

Neuroendocrine effects of light

The light/dark cycle to which animals, and possibly humans, are exposed has a major impact on their physiology. The mechanisms whereby specific tissues respond to the light/dark cycle involve the pineal hormone melatonin. The pineal gland, an end organ of the visual system in mammals, produces the hormone melatonin only at night, at which time it is released into the blood. The duration of elevated nightly melatonin provides every tissue with information about the time of day and time of year (in animals that are kept under naturally changing photoperiods). Besides its release in a circadian mode, melatonin is also discharged in a pulsatile manner; the physiological significance, if any, of pulsatile melatonin release remains unknown. The exposure of animals including man to light at night rapidly depresses pineal melatonin synthesis and, therefore, blood melatonin levels drop precipitously. The brightness of light at night required to depress melatonin production is highly species specific. In general, the pineal gland of nocturnally active mammals, which possess rod-dominated retinas, is more sensitive to inhibition by light than is the pineal gland of diurnally active animals (with cone-dominated retinas). Because of the ability of the light/dark cycle to determine melatonin production, the photoperiod is capable of influencing the function of a variety of endocrine and non-endocrine organs. Indeed, melatonin is a ubiquitously acting pineal hormone with its effects on the neuroendocrine system having been most thoroughly investigated. Thus, in nonhuman photoperiodic mammals melatonin regulates seasonal reproduction; in humans also, the indole has been implicated in the control of reproductive physiology.Summary of a Plenary Lecture presented by the author in Vienna, August, 1990     

Reproductive biology and management of captive black-footed ferrets (Mustela nigripes)

A captive breeding program is being conducted with black-footed ferrets (Mustela nigripes), an endangered species. Results of 5 years of study are reported. Simple, but specialized, nontraumatic handling techniques allowed assessment of reproductive status with minimal stress, which was important in breeding management. Black-footed ferrets are sexually mature and may successfully reproduce in their 1st year. Proestrus lasts approximately 2-3 weeks. Duration of estrus in unbred females was 32–42 days; females usually bred within 20 days. Most breeding activity occurred during April. Mean gestation length was 42.7 days (±0.7, range 42–45 days), litter size averaged 3.0 kits (±1.4, range 1–6 kits), and weaned kits/litter averaged 2.4 (±1.7, range 1–6 kits). Weaning rate of kits was 80%. Sex ratio of kits was essentially 1:1. Productivity was greatest among females ?3 years of age. Rapid expansion of the captive population is possible and will be important for genetic management of the species and for achieving the primary goal of the recovery program, which is to return black-footed ferrets to the wild.     

Measurement of chronic toxicity using the opossum shrimpMysidopsis bahia

The chronic toxicity of silver and endosulfan to the opossum shrimpMysidopsis bahia was determined using continuous-flow bioassays. The 28-day bioassays measured survival, fecundity, and growth (length and weight measurements). Maximum acceptable toxicant concentrations (MATC) were estimated from measured toxicant concentrations. MATC values were similar using either brood size or growth as a criterion for sublethal effects. As an alternative to the determination of fecundity impairment, measurement of growth reduction in response to exposure to toxicants may provide a useful tool in the assessment of chronic toxicity inMysidopsis life-cycle bioassays.