Regeneration of Giant Salvinia from Apical and Axillary Buds following Desiccation or Physical Damage

Can a new giant salvinia infestation occur even if most of the mat is destroyed except for the protected buds? From this study, we are able to conclude that buds can produce new growth under certain stressful conditions. They must be greater than 0.2 cm in length and they must possess greater than 30% moisture content to survive.

High-Temperature Effects on Growth and Propagule Formation in Hydrilla Biotypes

In consecutive greenhouse studies, growth and propagule formation were examined first in monoecious hydrilla [Hydrilla verticillata (L.f.) Royle], then in dioecious hydrilla, at three temperature levels (25, 30, and 35 C) and contrasted over three periods of growth (8, 12 and 16 wks). Each biotype was grown under natural photoperiods, decreasing from 14 hrs (in Oct, Nov, and Dec). For both biotypes, total biomass and root-to-shoot ratios were significantly reduced at 35 C; greater biomass was produced both at 25 and 30C. Increases in growth period generally enhanced total biomass and shoot production; however, shoot length was unresponsive to growth periods beyond 8 wks. The 35C treatment strongly impeded tuber formation and eliminat4ed the production of axillary turions; the number and biomass of these propagules peaked at lower temperatures under short photoperiods after 12 to 16 wks. Shoot elongation was stimulated with increases in temperature and was especially pronounced in the dioecious biotype. Notably, in the monoecious biotype, the number of shoots as a potential source of fragments, and tuber production (although reduced) occurred at relatively high levels under unfavorably hihg-temperature (35C) conditions. These results suggest that monoecious hydrilla may be better adapted to high temperatures than previously shown, and that the distribution of both biotypes in the U.S. could overlap further in southern states.

Interactions between American pondweed and monoecious hydrilla grown in mixtures

To assess the potential for monoecious hydrilla ( Hydrilla verticillata (L.f.) Royle) to invade existing aquatic plant communities, monoecious hydrilla was grown in mixtures with American pondweed ( Potamogeton nodosus Poiret). When grown with hydrilla from axillary turions, American pondweed was a stronger competitor. When grown with hydrilla from tubers, American pondweed was equally as strong a competitor as hydrilla.

Embryogenesis of Heterobranchus longifilis (Curvier and Valenciennes, 1840)

Studies on development of H. longifilis (Curvier and Valenciennes, 1840) were conducted at a temperature of 25EC ( 1Ec) in aquaria tanks continuous development were monitored with the use of wild Heerbrugy photomacroscope and length of yolk and larva were monitored using Stereo Olympus microscope with ocular micrometer. The division into animal and vegetal poles was observed 22 minutes after activation. The first cleavage occurred 65 minutes after activation while the second division which was perpendicular to the first line of division occurred 74 minutes after activation. This was quickly followed by the third and fourth cleavage at 80th and 82nd minutes after activation respectively. Morular stage was reached at 4 hours 20 minutes with formation of optic bud at 14 hours 35 minutes. (DBO) Developing embryo hatched after 27 hours of activation at a mean length of 6.63 and mean yolk length of 2.17. Yolk size decrease at an average rate of 38.5 % till the 5th day of total absorption. Growth of larvae proceeded faster in tail-anus region than in anus-snout portion of the body. The rate of yolk absorption and larva development (survival) as monitored in this work gives important information in Research and development programme for H. longifilis larva - an important aspect of Research development and implementation of appropriate technologies in small scale fisheries

Sexual differentiation and gonad development in striped mullet (Mugil cephalus L.) from South Carolina estuaries*

This study examined the sexual differentiation and reproductive dynamics of striped mullet (Mugil cephalus L.) in the estuaries of South Carolina. A total of 16,464 specimens were captured during the study and histological examination of sex and maturity was performed on a subsample of 3670 fish. Striped mullet were sexually undifferentiated for the first 12 months, began differentiation at 13 months, and were 90% fully differentiated by 15 to 19 months of age and 225 mm total length (TL). The defining morphological characteristics for differentiating males was the elongation of the protogonial germ tissue in a corradiating pattern towards the center of the lobe, the development of primary and secondary ducts, and the lack of any recognizable ovarian wall structure. The defining female characteristics were the formation of protogonial germ tissue into spherical germ cell nests, separation of a tissue layer from the outer epithelial layer of the lobe-forming ovarian walls, a tissue bud growing from the suspensory tissue that helped form the ovary wall, and the proliferation of oogonia and oocytes. Sexual maturation in male striped mullet first occurred at 1 year and 248 mm TL and 100% maturity occurred at age 2 and 300 mm TL. Female striped mullet first matured at 2 years and 291 mm total length and 100% maturity occurred at 400 mm TL and age 4. Because of the open ocean spawning behavior of striped mullet, all stages of maturity were observed in males and females except for functionally mature females with hydrated oocytes. The spawning season for striped mullet recruiting to South Carolina estuaries lasts from October to April; the majority of spawning activity, however, occurs from November to January. Ovarian atresia was observed to have four distinct phases. This study presents morpholog ical analysis of reproductive ontogeny in relation to size and age in South Carolina striped mullet. Because of the length of the undifferentiated gonad stage in juvenile striped mullet, previous studies have proposed the possibility of protandric hermaphrodism in this species. The results of our study indicate that striped mullet are gonochoristic but capable of exhibiting nonfunctional hermaphroditic characteristics in differentiated mature gonads.

Neonatal growth of Steller sea lion (Eumetopias jubatus) pups in Alaska

The growth rate of Steller sea lion (Eumetopias jubatus) pups was studied in southeast Alaska, the Gulf of Alaska, and the Aleutian Islands during the first six weeks after birth. The Steller sea lion population is currently stable in southeast Alaska but is declining in the Aleutian Islands and parts of the Gulf of Alaska. Male pups (22.6 kg [±2.21 SD]) were significantly heavier than female pups (19.6 kg [±1.80 SD]) at 1−5 days of age, but there were no significant differences among rookeries. Male and female pups grew (in mass, standard length, and axillary girth) at the same rate. Body mass and standard length increased at a faster rate for pups in the Aleutian Islands and the western Gulf of Alaska (0.45−0.48 kg/day and 0.47−0.53 cm/day, respectively) than in southeast Alaska (0.23 kg/day and 0.20 cm/day). Additionally, axillary girth increased at a faster rate for pups in the Aleutian Islands (0.59 cm/ day) than for pups in southeast Alaska v(0.25 cm/day). Our results indicate a greater maternal investment in male pups during gestation, but not during early lactation. Although differences in pup growth rate occurred among rookeries, there was no evidence that female sea lions and their pups were nutritionally stressed in the area of population decline

Nueva especie del género Mugil (Pisces: Mugilidae) de aguas cubanas.

A new species of mullet (Mugil) from Nipe Bay. North coast of Oriente Province, Cuba. The absence of axillary scale of pectoral fins, a very slender body and a notably elongated caudal peduncle are among the most diagnostic features of a new species.