Eunapius Fragilis Research Articles

Studies on histocompatibility in natural populations of freshwater sponges

AbstractHistocompatibility in natural populations of individuals was examined for the following four Japanese species of freshwater sponges: Ephydatia fluviatilis, Ephydatia muelleri, Radiospongilla cerebellata, and Eunapius fragilis. Gemmules were obtained from field‐grown specimens. Then, using juvenile sponges hatched from gemmules, fusibility was tested in the laboratory. Every interspecific combination among these four species displayed non‐fusion with no cytotoxic interaction. For all species, the occurrence of allogeneic histoincompatibility was assured, but manifestation of incompatibility was different from species to species. Among 36 specimens of E. fluviatilis collected from three localities, two strains nonfusible with each other were distinguished. Each locality was populated by a single strain. Specimens of E. muelleri were obtained from two localities. All combinations of specimens coming from the same locality were compatibly fusible, but those between specimens coming from different localities displayed conspicuous cytotoxic rejection reaction. This reaction occurred asymmetrically, resulting in the destruction of one partner. In R. cerebellata, two types of reactions, fusion and rejection, were also distinguished. In rejection, cytotoxic reaction occurred bilaterally and symmetrically in and around the contact zone. A total of 40 specimens, collected from a single pond, could be divided into 16 groups by their fusibility. As to E. fragilis, some combinations of specimens were compatibly fusible; the others displayed various degrees of incompatibility. In completely incompatible combinations, the paired sponges simply showed nonfusion with no sign of cytotoxic reaction. In more weakly incompatible combinations, the paired sponges were separated after initial fusion, the degree of which was variable depending on combination. A total of 59 specimens, collected from a single pond, could be classed into 14 groups by their fusibility. In both R. cerebellata and E. fragilis, some intergroup combinations were compatible, giving rise to probable genetic chimeras. Such chimeric sponges persisted with no sign of segregation for more than 1 month in the field.

Comparison of the radiosensitivity of dry dormant eggs, gemmules, and statoblasts of three invertebrate forms.

Radio sensitivities of the special structures (reproductive organs) of various invertebrate animals were examined. The doses of 50% hatch were about 5 kR for staboblasts of the bryozoa, Pectinatella magnifica; 70 kR for gemmules of the freshwater sponge, Eunapius fragilis; 130 kR for gemmuls of the freshwater sponge, Ephydatia fluviatilis; 180 kR for dry eggs of the rotifer, Brachionus plicatilis, and 350 kR for dry eggs of Artemia saliva. The results showed that Artemia eggs were the most radioresistant reproductive organ among the materials examined.

Life‐cycles of lotic populations of Spongilla lacustris and Eunapius fragilis (Porifera: Spongillidae)

SUMMARY. The life‐cycles of green and white morphs of the freshwater sponge Spongilla lacustris were examined in the light of past evidence that zoochlorellae may augment their sponge host's nutrition. Field collections from a lotic population of S. lacustris were supplemented by laboratory experiments on gemmule hatching and gemmule size. Both white and green S. lacustris produced sperm for a 6‐week period in 1976 starting in the middle of May. Out of thirty white and thirty green sponges examined during this period, twenty white and ten green sponges contained sperm. Sperm production in both morphs was limited primarily to the basal 3.18mm of sponge tissue, and the density of sperm packets in the two morphs was the same. Out of 180 white and green sponges examined in 1976, only four eggs, no embryos, and no larvae were observed. White sponges gemmulated a week or two earlier, and produced smaller gemmules which were more uniform in size than those of green sponges. White and green gemmules hatched synchronously in the spring. In 1977 one female and numerous male specimens of S. lacustris, and numerous females but no males of another sponge, Eunapius fragilis, were found. The life‐cycles are discussed in the light of other recent studies on freshwater sponges.

Cytochemical Observations of Gemmule Development in Eunapius fragilis (Leidy): Porifera; Spongillidae

The cytology and cytochemistry of gemule formation in the freshwater sponge Eunapius fragilis (Leidy) is investigated. The aggregation of ameboid cells which initiates gemmulation is composed of three distinct cell types, two of these fitting the morphological criteria of the archeocyte class. The third cell type, the granular cell, is a differentiated cell type which undergoes cytolysis during gem-mule coat synthesis. Following early polarisation of the aggregate into an internal reproductive area and a peripheral coat region, a structurally and chemically heterogeneous gemmule coat is synthesis-ed. The coat is formed through secretory activities involving several cell types including, possibly, the internal endothelium. The coat is composed of “collagenous” fibers embedded in a matrix of varying degrees of density–showing close structural and cytochemical similarities to vertebrate chondroid tissue. Vitelline platelets of thesocytes of E. fragilis do not cytochemically resemble any previously reported vitelline inclusions from other sponges. Outer valves of the platelets contain components stained by basic dyes at acidic pH which are not extracted by RNase. Distinct differences in developmental processes and morphological–including cytochemical–characteristics of gemmules of different spongillid species are apparent.

Feulgen microspectrophotometric analysis of deoxyribo‐nucleoprotein organization in larval and adult freshwater sponge nuclei

Microspectrophotometric measurements of nuclei of adult choanocytes and archeocytes and larval archeocytes and flagellated ectodermal epithelia from stages III and IV were undertaken on tissues from the freshwater sponge, Eunapius fragilis (Leidy). The condensed nuclei of differentiated choanocytes and state IV flagellated epithelial cells presented integrated extinction values about 64% of those obtained for either adult or larval archeocytes. This suggests that such measurements represent sensitive indicators of deoxyribonucleoprotein-complex organization; thus, nuclear differentiation. Further, no large population of G2 (4C) nuclei was found among these populations as has been reported in two classes of coelenterates.

Cytochemical observations of larval development in Eunapius fragilis (Leidy): Porifera; spongillidae.

Freshwater sponges of the family Spongillidae reproduce sexually through formation of a parenchymula larva. The cytochemical characteristics of parenchymula larval metamorphosis - beginning with the blastula and terminating with the motile escape stage - for the spongillid Eunapius fragilis (Leidy) have been defined using both absorption and fluorescent cytochemical methods, particularly those demonstrating protein end-groups. Morphogenesis of the parenchymula larva of E. fragilis involves the interrelated processes of cytodifferentiation and mobilization of reserve materials. Larval development has been categorized into five stages, from blastula (stage I) through the escape stage (stage V). Parenchymula development is characterized by morphogenetic precocity, a fact influencing the rate of mobilization of cytoplasmic reserves, cytodifferentiation, and the fate of individual cell types. With attainment of the stage V parenchymula, the larva is, essentially, a mobile adult sponge exhibiting flagellated chambers, canal systems, a well defined connective tissue stroma, a diverse cell population consisting of specialized elements and a totipotent archeocyte reserve, and a terminal epitheliocyte line. The present study recognizes differences in development within the spongillids as well as within more remote poriferan taxa - emphasizing the need for detiled understanding of particular processes in individual species before proposing major generalizations about development in this ancient but evolutionally specialized group.