Life history of Gambusia holbrooki (Pisces, Poeciliidae) in the Ebro delta (NE Iberian peninsula)

We studied age, growth and reproduction of an introduced poeciliid, Gambusia holbrooki (Agassiz, 1859), in the Ebro delta marshes. Maximum ages observed were 2⁺ in females and 0⁺ in males. Growth commenced in March and continued until September. Females reached greater sizes, had a higher rate of growth and lived longer than males. The largest sizes found were 63 mm versus 32 mm . Multiple spawning occurred throughout the reproductive cycle (from May to September). The average brood size per female reached its maximum in July in the parental cohort (86 embryos/) and in August in the offspring cohort (29 embryos/). After reproduction the parental cohort decreased drastically. The relationship between fecundity (F) and total length (mm) was calculated for each month of the reproductive period. Sex-ratio deviated significantly from unity.Viviparity, several broods and large larvae provide G. holbrooki with several advantages over oviparous species. The capacity to adjust its life history to a particular environment could explain the life history differences between those in the Ebro delta and other populations.     

The life history of Ahnfeltiopsis paradoxa (Gigartinales, Rhodophyta) in laboratory culture

The life history of the red alga Ahnfeltiopsis paradoxa (Suringar) Masuda (Phyllophoraceae, Gigartinales) from Japan was completed in laboratory culture. Carpospores isolated from field-collected plants germinated to form circular crusts that were composed of a monostromatic hypothallium consisting of radiating filaments, a polystromatic perithallium consisting of tightly coalescent erect filaments, and hypobasal tissue derived from the hypothallium. The crusts were induced to sporulate by transferring them from short-day to long-day regimes at 15° and 2°C. Each crust produced several nemathecia along 1-4 concentric rings. Intercalary, cruciately or decussately divided tetrasporangia were formed in 4-6 (1-2 at the margin of the nemathecium) successive cells of a single filament of the nemathecia. Tetraspore germlings gave rise to basal discs from which upright axes developed. The upright axes first grew without branches or were sparsely branched and later bore many marginal reproductive proliferations. Procarps and spermatangia were formed in the proliferations on different individuals. Carposporophytes developed on female plants that were co-cultured with male plants. Gonimoblast filaments were formed from an auxiliary cell that fused with a carpogonium. Carposporangia developed from gonimoblast filaments and medullary cells contacted by the gonimoblast filaments. Carpospores were discharged through carpostomes formed in the thickened cortex. Tetraspores were cultured from field-collected crusts of a morphology similar to that of cultured tetrasporophytes. They gave rise to upright gametophytic axes similar in morphology to this species as seen in the field.     

On the life history ofTurnerella mertensiana (Rhodophyta,Gigartinales)

Turnerella (Gigartinales) withT. mertensiana known from northern Japan was studied to determine its life history. Carpospores cultured from foliose female plants gave rise on germination to crustose plants containing tetrasporangia, as noted previously inT. pennyi from the Atlantic. The crusts were slow to develop and required 3–5 years to achieve reproductive maturity. Tetraspores liberated in culturedT. mertensiana gave rise on germination eventually to thalli similar to gametophyticT. mertensiana. Thus this species may be said to adhere to the pattern of life history in which a large, foliose gametophyte alternates with a small crustose tetrasporophyte. The erect filaments of the small sporophytes branch laterally and tetrasporangial mother cells are found there, exemplifying an unusual method for crustose species to produce tetrasporangia.     

Life history and photoperiodic responses in Chondrus giganteus forma flabellatus (Gigartinaceae,Rhodophyta) from Japan

The life history and photoperiodic responses of the carrageenophyte Chondrus giganteus forma flabellatus (Rhodophyta) from Japan were investigated in culture. This entity has a Polysiphonia-type life history and the formation of both tetrasporangia and cystocarps is controlled by daylength. A night-break of 1 h in the middle of a 16 h night was effective in inhibiting reproduction, confirming the classical photoperiodic nature of the response. Tetrasporangia formed at daylengths of 12 h or less, whereas cystocarps only developed at daylengths of 10 h or less. The formation of spermatangia required daylengths of 12 h or less, but production was not inhibited by a night-break of 1 h in the middle of a 16 h night.     

Asexual life history by quadriflagellate swarmers of Ulva spinulosa (Ulvales, Ulvophyceae)

This is the first report of a Ulva species reproducing asexually solely by quadriflagellate swarmers. Ulva spinulosa Okamura et Segawa specimens were collected from Ukibuchi on the Pacific coast of Kochi Prefecture, southern Japan. Quadriflagellate swarmers were released from these specimens. The swarmers showed negative phototaxis before settlement. Thalli cultured from these swarmers also released quadriflagellate swarmers in culture. Microspectrophotometric studies demonstrated equivalent DNA in nuclei of vegetative cells in thalli of U. spinulosa and in sporo‐phytes of the other Ulva species with sexual life history (U. fasciata Delile). Furthermore, the quadriflagellate swarmers of U. spinulosa had the same DNA value, demonstrating that the quadriflagellate swarmers are produced without meiosis.     

The life history and culturing of Xestoleberis hanaii (Crustacea,Ostracoda)

Xestoleberis hanaii Ishizaki, 1968 is one of the most abundant species on the Japanese coast and can be collected in all seasons from intertidal calcareous algae on rocky shores. Several characteristics make this species a suitable `experimental animal' in the laboratory: (1) adaptability to artificial environments (room temperature, petri dish, artificial seawater, single cultured food-type), (2) high fertility (active copulatory behaviour, egg brooding within the carapace, high egg productivity) and (3) rapid growth rate. Females mate after the final moult (when the reach sexual maturity); oviposition of fertilized eggs takes place over a period of four days after the final moult. Eggs (about 40 in total) are laid a few at a time in the postero-dorsal brood space of the carapace; they hatch in about 9 d as A-7 instars which are then discharged from the brood space within a day or two. Seven moults take place within the next approx. 33 (female) or 39 (male) days to reach adulthood. Adult females live for about 18 weeks and may repeat the reproductive cycle three times; adult males live for about 14 weeks.     

Morphology and life history of Halopteris filicina (Sphacelariales, Phaeophyceae) from Korea

The vegetative morphology and life history of Halopteris filicina (Grateloup) Kutzing, collected from Korea, were examined in laboratory culture. Field plants attaining 3–5 cm in height were epilithic, tufted, yellowish-brown, and produced numerous erect axes with alternately distichous branches from compact basal discs. They were cultured under a 12:12 h LD photoperiod at 10°-C, 15°C and 20°C to observe the influence of temperature on reproduction. At 10°C plants grew only vegetatively, whereas at 15°C and 20°C they produced unilocular sporangia. Unispores released from sporangia developed into monoecious, anisogamous gametophytes that formed plurilocular female and male gametangia on the same lateral branches. The zygotes, by fusion of female macrogametes and male microgametes, developed into sporophytes bearing unilocular sporangia, whereas the unfused female gametes germinated parthenogenetically. This species was confirmed to have an isomorphic life history, basically similar to the other species of Sphacelariales.     

Morphology and life history of Scytosiphon canaliculatus comb. nov. (Scytosiphonales,Phaeophyceae) from Japan*

Morphology of field material and life history in culture were studied in Scytosiphon canaliculatus (Setchell et Gardner) comb. nov. from northern Japan. Erect gametophytes of S. canaliculatus are cylindrical, tubular, up to 7 mm wide and 40 cm long, and without regular constrictions. S. canaliculatus has pronounced anisogamy and ascocysts accompanied with plurilocular gametangia. The life history of S. canaliculatus showed an alternation between erect gametophytes and crustose prostrate sporophytes bearing unilocular sporangia. Since field sporophytes of S. canaliculatus were found to be identical with Hapterophycus canaliculatus Setchell et Gardner (Ralfsiaceae, Phaeophyceae), it is proposed to transfer H. canaliculatus to the genus Scytosiphon. In the field, gametophytes with plurilocular gametangia appeared in spring and disappeared in summer. Sporophytes with unilocular sporangia were collected in late autumn and winter. Unilocular sporangia were produced at 15°C in short-day culture conditions and unispores developed into erect gametophytes at 5–15°C. It is suggested that the seasonal Occurrence of gametophytes in the field is due to the seasonal formation of unilocular sporangia, which is regulated by temperature and photoperiod.     

Somatic embryogenesis from cultured mature cotyledons of cassava (Manihot esculenta Crantz)

Somatic embryogenesis was obtained from mature cassava cotyledons explants. A two-step medium sequence was developed for efficient embryogenesis. Application of 2,4-D (4 mg l^-1) yielded proembryogenic masses which developed into somatic embryos after transfer to a medium containing NAA (0.01 mg l^-1), BA (0.1 mg l^-1) and GA₃ (0.1 mg l^-1). The 2,4-D concentrations used for embryo initiation strongly influenced embryo development. Among the cultivars tested, TMS 30395 was most responsive. Full strength MS basal medium alone or with 4 x MS micro salts was efficient for the formation of somatic embryos. Casein hydrolysate, adenine sulfate, nicotinic acid, glycine, tryptophan, and serine were ineffective for embryo development. High sucrose concentration (6%, w/v) inhibited the induction of somatic embryos, while 6% sucrose was optimal concentration for the development of somatic embryos after an induction treatment using 2% sucrose. Addition of 0.52 mg l^-1 ABA to the induction media resulted in an increase in somatic embryos production. The ploidy levels of the regenerated plantlets were determined by flow cytometry analysis. Fifty regenerants tested were all tetraploids as the source plants and were morphologically normal. The implications of these results are discussed in relation to genetic transformation using the cotyledons as the explant source.Abbreviations ABA abscisic acid - BA 6-benzylaminopurine - DAPI 4,6-diamidino-2-phenylindole - SR 101 sulforhodamine - GA₃ gibberellic acid - MCPA methyl- chlorophenoxyacetic acid - NAA naphthalen-acetic acid - PCPA P-chlorophenoxyacetic acid - 2,4-d 2,4-dichlorophenoxyacetic acid - 2,4,5 T 2,4,5-trichlorophenoxyacetic acid     

Seasonal changes in abundance and shifts in dominance of life history stages of the carrageenophyte Sarcothalia crispata (Rhodophyta, Gigartinales) in south central Chile

The population dynamics of the carrageenophyte Sarcothalia crispatais described from subtidal beds at two localities in south-central Chile. Seasonal fluctuations in total density and biomass were not evident. Frondswere identified to phase by the presence of reproductive structures and theresorcinol reaction. The monthly changes in abundance of each kind offrond were determined. Permanent gametophytic or sporophyticdominance was not evident: the more exposed site showed a seasonal shiftfrom sporophytic dominance in summer to gametophytic dominance inwinter, whereas the more protected site showed an interannual shift fromgametophytic to sporophytic dominance. The differences between localitiesand years suggest a very local population dynamics with large contributionof self-seeding to the maintenance of the S. crispata beds.     

Life history of Chnoospora implexa (Chnoosporaceae, Phaeophyceae) in culture

The life history of the brown alga Chnoospora implexa J. Agardh (Chnoosporaceae, Scytosiphonales) from Japan was studied in laboratory cultures. This species showed a heteromorphic and diphasic life history, alternating between erect gametophytes and discoid sporophytes. The gametophytes were dioecious and produced isogametes. The zygotes developed into sporophytes at 20°C under long‐day conditions, which formed plurilocular zoidangia. Zoids released from the plurilocular zoidangia developed again into sporophytes that always formed plurilocular zoidangia at 20°C and 25°C in long‐day conditions, and mainly unilocular zoidangia at 25°C in short‐day conditions. Zoids released from unilocular zoidangia developed into dioecious gametophytes. At 15°C zygotic erect thalli were formed and were revealed to be diploid by microspectrofluorometric measurements of nuclear DNA contents. The development and reproduction of unfused gametes were similar to those of zygotes. Some strains showed a direct‐type life history; gametophytic thalli were produced, but not via a sporophytic phase.     

Carrageenans from Cystocarpic and Sterile Plants of Chondrus Pinnulatus (Gigartinaceae, Rhodophyta) Collected from the Russian Pacific Coast

The chemical structure, gel properties and biological activity of the carrageenans isolated from cystocarpic and sterile plants of Chondrus pinnulatus were investigated. The total carrageenan content of the sterile plant was observed to be twice that of the cystocarpic plants. According to data obtained by ¹³C-NMR and FT IR, the gelling polysaccharides from cystocarpic and sterile plants of C. pinulatus have similar structures and were identified as κ/ι-carrageenans. The difference between these polysaccharides was in the ratio of the κ- and ι-segments, with a predominant content of κ-segments in cystocarpic plants (80%). Moreover, KCl-insoluble fractions possibly contain hetero-disperse μ/ν precursor: amounts of this in the polysaccharide from sterile plants were more than that extracted from the cystocarpic plants. The KCl-soluble fractions (non gelling) were λ-carrageenans with another carrageenan type that had a low amount of 3,6-anhydrogalactose. Carrageenans from cystocarpic stages showed good gelling properties, whereas those from sterile plants formed a very weak gel. Structural differences and molecular weight of carrageenans obviously determine the biological activity of the polysaccharides. Non gelling-carrageenans from both types of ιt C. pinnulatus plants showed high macrophage-phosphatase activity and κ/ι-carrageenan from cystocarpic plant possessed a potent anti-coagulant activity, which was extremely strong in a low concentration of 100 μg ml⁻¹.     

杜鹃三节叶蜂生物学特性及其发生规律研究

杜鹃三节叶蜂Arge similis(Vollenhoven)是深圳市梧桐山风景区的一种重要害虫,为害杜鹃花科Ericaceae的多个栽培种类,严重影响植株的长势及观赏价值。本试验通过野外调查和室内观察,对杜鹃三节叶蜂的形态特征、生物学特性及发生规律进行了研究。结果表明:杜鹃三节叶蜂在深圳市梧桐山风景区一年发生7代,以蛹越冬,翌年2月下旬越冬蛹陆续开始羽化为成虫,3月上中旬即开始产卵,4-9月份有明显的世代重叠,11月下旬老熟幼虫入土化蛹越冬,完成一个世代需要32-46 d。卵集中产在杜鹃嫩叶叶背与叶缘表皮之间。幼虫共5龄,具有暴发性、暴食性的特点,1-2龄幼虫群集取食,食量较小,3龄以后幼虫开始分散为害,食量大增。老熟幼虫在植株基部周围的土壤中或枯枝落叶层间吐丝结茧化蛹,化蛹深度在距地表2-5 cm左右。     

The life history of Boyeria irene (Fonscolombe, 1838) (Odonata: Aeshnidae) in the Sierra Morena Mountains (southern Spain)

The life history of Boyeria irene is inferred fromsize-frequency analyses of sweep-net samples taken during fiveyears in a permanent stream in the Sierra Morena Mountains.There the species is apparently mainly semivoltine, although a fewlarvae require three years to complete development. The instardistribution during winter is that of a summer species (sensuCorbet, 1954). Metamorphosis is confined to spring and thereis a long flying season. Similarities between B. ireneand congeneric species in North America are discussed.     

Some observations on the distribution and life history of Caenis robusta Eaton (Ephemeroptera) in Cheshire and North Shropshire,England

Caenis robusta Etn. was found in only 8 of 107 water bodies sampled. All the habitats from which it was recorded contained plant debris; the waters were still or slow-flowing and had conductivities ranging from 120–687 µmhos cm^–1 at 25°C.In North Shropshire, England, C. robusta had one generation per year. Newly hatched nymphs were abundant in August and growth occurred rapidly until September. No growth took place from October until March but was again rapid from April until June. Emergence took place at dusk in late June and July.     

Seed mass, habitat and life history: a re-analysis of Salisbury (1942, 1974)

A recent re-analysis of the data of Salisbury (1974) claims his data do not support the hypothesis that seeds of species from shaded habitats are heavier than those from unshaded habitats, partly because the original analysis was inappropriate and partly because of bias in the dataset. We show first that the re-analysis itself contains errors, and second that the charge of bias is based largely on a misunderstanding. We also show that analysis of a larger dataset, drawn from Salisbury (1942) and from Salisbury (1974), provides convincing support for the hypothesis and suggests that the relationship is independent of life history.     

Aspects of the life history of Rhodophysema elegans (Rhodophyta,Peyssonneliaceae)

The life history of Rhodophysema elegans is described from laboratory culture and the field in Newfoundland, Canada. Sexual plants are lacking and tetraspores germinate to produce new tetrasporangial plants. Approximately 30–35 chromosomes were counted in vegetative cells of successive generations. There was no evidence of chromosome pairing in the early stages of division of tetrasporangial initials, indicating that the tetrasporangia are apomeiotic.     

Nuclear division of the vegetative cells, conchosporangial cells and conchospores of Porphyra yezoensis (Bangiales, Rhodophyta)

To confirm the position and timing of meiosis in Porphyra yezoensis Ueda, the nuclear division of vegetative cells, conchosporangial cells and conchospores was observed. An improved staining method using modified carbol fuchsin was introduced to stain the chromosomes of Porphyra. Pit‐connections between conchosporangial cells also stained well with this method. Leptotene, zygotene, pachytene, diplotene, diakinesis, metaphase, anaphase and telophase were observed in the conchosporangial cells. During the germination of conchospores, no characteristics of meiosis I were found. No difference between the nuclear division of vegetative cells and that of conchospores was observed, and 2–3 days were needed for the first cell division both in vegetative cells and conchospores. Therefore, the cell division that occurs during conchospore germination is not meiosis I. Our results indicate that the prophase of meiosis I begins during the formation of conchosporangial branches, and metaphase I, anaphase I and telophase I take place during the maturation of conchosporangial branches. Then the three‐bivalent nucleate sporangia complete cell division to form two individual conchospores, each with one three‐univalent nucleus. The conchospores released from the sporangia are at meiotic interphase. Meiosis II occurs at the first nuclear division during conchospore germination, which is a possible explanation for the observation of mosaic thalli in mutant germlings of P. yezoensis. The mosaic thalli might also arise from gene conversion/post meiotic segregation events, comparable to those in Sordaria fimicola (Roberge ex Desm.) Ces. & De Not. and Neurospora crassa Shear & B.O. Dodge.