THE LIFE HISTORY OF FREE-RANGING ATLANTIC SPOTTED DOLPHINS (STENELLA FRONTALIS): AGE CLASSES, COLOR PHASES, AND FEMALE REPRODUCTION

Atlantic spotted dolphins (Stenella frontalis) were observed underwater and from the surface from 1985 to 1996 and photographed through successive years. Individuals were categorized into age classes by their degree of spotting and color phases. Dolphins spent an average of 3 yr in the two-tone color phase, 5 yr in the speckled phase, 7 yr in the mottled phase and up to 10 yr or more in the fused phase.
Sex ratios were close to parity, with old adults skewed towards females and juveniles and young adults skewed towards males. The average calving interval for 24 females was 2.96 years with a range of 1–5 yr. Females whose calves survived the first year had a significantly longer calving interval (3.56 years). The ages of first parturition for five females were estimated to be 10–12 yr. The age at sexual maturation was estimated to range from 8 to 15 yr.
Pregnancy rate fluctuated annually, with an average rate of 0.25 (range 0.07–0.57). Annual average birth rate was 0.08 (range 0.07–0.14), average calf production was 0.33 (range 0.06–0.52), average fecundity was 0.23 (range 0.13–0.30), and average recruitment was 0.06 (range 0.03–0.08). Most females who lost a calf conceived the same or following year.
Lactation lasted up to 5 yr, and 45% of visibly pregnant females were also lactating. Age of first parturition was associated with the mottled color phase. Average first-year mortality rate of calves was 0.24.     

REPRODUCTIVE MATURITY AND SEASONALITY OF MALE SPOTTED DOLPHINS, STENELLA ATTENUATA, IN THE EASTERN TROPICAL PACIFIC

We estimated age at attainment of sexual maturity and examined reproductive seasonality for male spotted dolphins, Stenella attenuata , from the eastern tropical Pacific Ocean. Maturity was determined by histological examination of testes. Average age at sexual maturation was 14.7 yr (the mean of two readers' age estimates). Testis and epididymis weight and seminiferous tubule diameters were reliable indicators of maturity, whereas age, length and color phase were less reliable. Seasonality was determined by changes in testis and epididymis weight, relative quantity of spermatids and spermatozoa, and lumen diameter, as well as an index of testis development (weight of the right testis and epididymis divided by length of the right testis). Testis and epididymis weights and index values peaked in July and August, midway between two predicted mating seasons for the northern offshore stock, but spermatozoa levels were elevated during the predicted breeding seasons.     

REPRODUCTION AND LIFE HISTORY OF THE RED ALGA GALAXAURA OBLONGATA (NEMALIALES,GALAXAURACEAE)1

Culture and morphological studies showed that Galaxaura oblongata (Ellis et Solander) Lamouroux has a triphasic life history with conspicuous gametophytes and small filamentous tetrasporophytes. Development of male and female reproductive structures is very similar and both begin with the enlargement of a terminal cell of a filament branch occupying a normal vegetative position within the apical pit of a thallus branch. In male thalli this modified branch forms a conceptacle in which spermatangia are produced. In female thalli, this modified branch forms a three-celled carpogonial branch consisting of a carpogonium, hypogynous cell and basal cell. Filament branches from the basal cell form a pericarp and the gonimoblast develops directly from the carpogonium. Carposporangia are produced in conceptacles which resemble the male conceptacles. About the time the first carposporangia are produced, the carpogonium, hypogynous cell and basal cell form a large fusion cell. Released carpospores germinate in a unipolar or bipolar manner and form small filamentous thalli. Under short day conditions, cruciate tetrasporangia are produced in small clusters. Tetraspores germinate similarly to carpospores and also form small filamentous thalli. Under low nutrient conditions, small cylindrical thalli develop on the filaments and these appear similar to gametophytes collected in nature.     

LIFE HISTORIES OF BLIDINGIA MINIMA (CHLOROPHYCEAE), ESPECIALLY SEXUAL REPRODUCTION1

Blidingia minima (Näg. ex Kütz.) Kylin from Muroran, Hokkaido, Japan, has been shown to exhibit four patterns of life history in culture. Sexual reproduction, reported fully for the first time in the genus, occurs in two of them. I. An isomorphic-heteromorphic complex in which erect, tubular sporophytes alternate with dioecious gametophytes of the same forms, with the irregular production by both phases of discoid or pulvinate (pincushion-like) microthalli capable of both sexual and asexual reproduction. II. An alternation of heteromorphic phases in which an erect, tubular sporophyte alternated irregularly with a gametophytic microthallus. III. An asexual alternation of heteromorphic phases in which an erect, tubular frond alternates irregularly with a microthallus by means of quadriflagellate zoospores. IV. An asexual, monophasic life cycle in which erect, tubular fronds are perpetuated by quadriflagellate zoospores. The first pattern occurred in spring populations from one of three sites. The second occurred in populations from two sites. The third and fourth occurred in all populations tested. The life history of Blidingia minima from Muroran is similar to that of Kornmannia zostericola from Muroran.     

LIFE HISTORY AND IN SITU GROWTH RATES OF ALEXANDRIUM TAYLORI (DINOPHYCEAE, PYRROPHYTA)

Alexandrium taylori Balech is a phototrophic marine dinoflagellate. It produced recurrent blooms during the summer months (July and August) of 1994 to 1997 in La Fosca beach (NW Mediterranean). In addition to a motile vegetative form, A. taylori had two benthic forms: temporary cysts and resting cysts. Temporary cysts were a temporally quiescent stage produced from the ecdysis of the vegetative cell in both natural populations and laboratory cultures. Temporary cysts may divide to form motile cells. Resting cysts had a thicker wall than the temporary cysts and had a red accumulation body. Gametes and planozygotes were also observed in laboratory cultures. Alexandrium taylori showed in situ diurnal vertical migration with an increase of vegetative cells in the water column in the morning through midday, with concentrations peaking in the afternoon followed by lower levels at night. Most vegetative cells lost their thecae and flagella, and with them their motility, turning into temporary cysts that settled in the early evening. The number of temporary cysts in the water column rose in the evening and at night. The temporary cysts gave rise to motile cells the following morning. Synthesis of DNA occurred in vegetative cells at night, and a preferential period of cell division occurred at sunrise. The estimated division rate in the field was 0.4–0.5 vegetative cells·day⁻¹. Temporary cysts had twice the DNA of a G₁ vegetative cell. The minimum in situ division rate of the temporary cysts was 0.14 day⁻¹. The role of the resting and temporary cyst population in the annual recurrence and maintenance of the A. taylori bloom is discussed.     

CULTURE STUDIES ON THE LIFE HISTORY OF CHORDARIA LINEARIS (PHAEOPHYCEAE) FROM TIERRA DEL FUEGO,SOUTH AMERICA1

Studies of laboratory cultures of Chordaria linearis (Hooker et Harvey) Cotton from southernmost South America revealed that this species has an obligate sexual life history in which a macroscopic sporophyte alternates with a monoecious microscopic gametophyte. Sexual reproduction is isogamous and under photoperiodic control. Gametes are produced only in short days, whereas in long days, asexual zoospores are formed that recycle the gametophyte generation. Unfused gametes develop into gametophytes, and sporophytes originate only from zygotes. Unlike other sexual members of the Chordariales, gametes of C. linearis have a reduced stigma and do not show phototaxis. They are released at the beginning of the night, not in the morning. In nature, C. linearis seems to be regularly infected by a dictyosiphonalean epiphyte resembling the rare arctic species Trachynema groenlandicum (Lund) Pedersen. The epiphyte is responsible for previous contradictory results obtained in laboratory cultures of C. linearis. This is the first record of Trachynema in the southern hemisphere.     

CULTURE STUDIES ON REPRODUCTION OF SPERMATOCHNUS PARADOXUS (PHAEOPHYCEAE,CHORDARIALES)1

The life history of Spermatochnus paradoxus (Roth) Kütz. isolated from the Mediterranean Sea was studied in culture. Meiospores develop to a microscopic stage (microthallus) which at 20°C perpetuates asexually by plurilocular sporangia and formation of new microthalli. At 9°C microthalli act as homothallic gametophytes. Fusion of isogametes results in a diploid microthallus which, after differentiation of an apical cell, leads back to Spermatochnus plants. In addition, gametes develop without fusion to form haploid macrothalli, the further fate of which has not been determined. Chromosome numbers alternate between n = 20 ± 2 in the microthalli and 2n = 41 ± 4 in macrothalli.     

AGE, GROWTH, AND REPRODUCTION OF THE FINLESS PORPOISE, NEOPHOCAENA PHOCAENOIDES, IN THE COASTAL WATERS OF WESTERN KYUSHU, JAPAN

Abstract: In the coastal waters of western Kyushu, Japan, a total of 97 incidentally taken or stranded finless porpoises, Neophocaena phocaenoides , was collected for studying age, growth and reproduction. An additional 17 specimens from the Inland Sea were used for a comparison of life history. Mean neonatal body length was 78.2 cm. Both males and females grew to around 140 cm by 5 yr of age. The maximum body lengths of males and females in western Kyushu were 174.5 cm and 165.0 cm, respectively, which were smaller than those recorded in other Japanese waters. Females probably attain sexual maturity at ages of 6–9 yr and at body lengths of 135–145 cm. Males probably mature sexually at ages of 4–6 yr, at body lengths of 135–140 cm and at weight of testis of 40–150 g. The lack of females aged 5–6 yr and males aged 4–5 yr precluded firm conclusions on ages at sexual maturity. Parturition in western Kyushu was estimated to be prolonged from autumn to spring, whereas in the Inland Sea and Pacific waters it was restricted from spring to summer with a peak in April. These geographical differences and available information on distribution implies that the finless porpoises in western Kyushu constitute a local population.     

DEVELOPMENT, SEXUAL DIMORPHISM, and INDIVIDUAL VARIATION IN THE SKELETON OF THE FINLESS PORPOISE, NEOPHOCAENA PHOCAENOIDES, IN THE COASTAL WATERS OF WESTERN KYUSHU, JAPAN

Development, sexual dimorphism, and individual variation were examined in the skeleton of the finless porpoise in the coastal waters of western Kyushu, Japan. Skulls ceased growing by 4 yr. Postcranial skeletons ceased increasing in size at an age older than 11 yr. The finless porpoise was estimated to attain cranial maturity by 4 yr and physical maturity at 14–23 yr. Sexual dimorphism was not detectable in most of the cranial characters but was detected in more than half of the postcranial characters. Females tended to show larger values of postcranial characters. The shape of the pelvic bone was obviously different between males and females. Thus, a discriminant function was proposed to determine sex using measurements of this bone. Individual variation was greatest in the feeding apparatus such as length of the rostrum, and least in the braincase.     

LIFE CYCLE OF A STEPHANODISCUS SP. (BACILLARIOPHYTA)1

Studies of the life cycle of a centric diatom, tentatively identified as Stephanodiscus neoastraea Håkansson & Hickel, showed that sexual reproduction occurred every year in a freshwater lake (Lough Neagh, Northern Ireland). Male and female gametes were produced in cells below 55% of the maximum diameter during a 3–4-week period in late summer, following the return of nitrate concentrations above 10 μM NO_3-N. The frequency of sexual reproduction was linked to the cycle of diameter size reduction and regeneration. The times of largest decreases in cell diameter were during nutrient stress in summer and low light conditions in late autumn, rather than during the main spring growth period. So, environmental conditions (combined with the limited life-spans of individual cells) affected the rate of diameter reduction and, therefore, the length of the life cycle (3–4 years).     

Habitat Preference, Reproduction and Diet of the Earthworm Eel, Chendol keelini (Teleostei: Chaudhuriidae)

The ecology of the earthworm eel, Chendol keelini, was studied in the field over a period of nine months. In addition this information was supplemented by aquarium observations. The species was most abundant in pools where it was associated with leaf litter and mats of fine tree roots along the banks. It fed on benthic invertebrates, especially chironomid and ephemeropteran larvae. C. keelini is sexually dimorphic; adult males develop a headhump and grow to a larger size than females. Reproduction was seasonal; the reproductive phase coincided with the wet season and lasted for several months. Fecundity was around 40 eggs per clutch. The eggs were spherical, between 1.2 and 1.5mm in diameter, and possessed a pair of long filaments for adhesion to the substrate. Females probably spawned more than once during the breeding season. The length frequency distributions and juvenile growth suggest that C. keelini is a short-lived species that matures during the first year with few individuals surviving to the second breeding season.     

LIFE HISTORY AND SYSTEMATIC POSITION OF PSEUDOCHORDA GRACILIS SP. NOV. (LAMINARIALES,PHAEOPHYCEAE)1

Pseudochorda gracilis sp. Nov. (Pseudochordacease, Laminariales) is described from the Japan Sea coast of Hokkaido/ the species is subtidal, epilithic and annual, appearing in spring and maturing in winter. Erect thalli grow solitary or in tufts on a small discoid holdfast. They are simple, cord-shaped and hollow, with inner hyphal filaments, cylindrical medullary cells and paraphyses consisting of 3–6 cells. Hair tufts are observed only in young thalli. Unilocular sporangia are sessile and narrowly ovate. In culture, P. gracilis shows a heteromorphic life history with oogamy, characteristic of the order Laminariales. Gametophytes are dioecious and dimorphic. Gametophytes mature under lower temperature conditions (usually below 10°C), and sporophytes mature under low temperature and short-day conditions (5°C, SD). The seasonal growth pattern of the species results from the photoperiod-temperature conditions controlling saprophyte maturation.     

从西藏金发藓科植物初步研究兼论青藏高原的隆起

西藏金发藓科植物,已知有7属,30种,4变种;其中新种5个,新变种3个。从水平分布看,大多集中雅鲁藏布江流域附近,因该流域是印度板块北缘与欧亚大陆南缘的缝合线,因而金发藓科植物得以高度集中。本文讨论了该科在本区的地理分布和区系成份的分析等问题,并讨论了青藏高原的隆起对该群藓类的影响。     

长江口白鲟幼鱼的形态、生长及其食性的初步研究

1985年6—10月于长江口共获得白鲟当年的1龄幼鱼标本49尾(体长80—530毫米),进行了有关形态、生长以及食性的观察研究。①幼鱼形态与成鱼基本相似,其体长与体长,眼径以及体长／吻须长呈明显的正相关;③6月21日至10月12日间的幼鱼长度生长方程为Lg=79．9723e^0.0213t(式中Lg为体长,毫米;t为天数),其相对增长率以8月为最快;④长江口白鲟幼鱼摄食频度为100％,平均胃饱满指数为198．46,它们是肉食性鱼类,以底栖小型虾类和鱼类为主食,食物共有8类16个可鉴别种类;④考虑到这种珍稀鱼类的种群与资源衰退现状,建议在长江河口区制定必要韵保护措施。