The biology of Peneroplis planatus (Fichtel and Moll) Montfort.

摘要

Peneroplids are particularly interesting because they are unique among protists and invertebrates by forming symbiotic associations with unicellular red algae. P. planatus retained 100% (P {dollar}>{dollar} 0.05) of the {dollar}sp{lcub}14{rcub}{dollar}C-tracer label of six of the ten algal species ingested. There was selectivity in feeding; Cocconeis placentula and Amphora sp. were ingested at a rate 5 times greater than other species. In culture, P. planatus did not grow when starved, and grew less when fed in complete darkness. Dunaliella salina and various diatoms promoted more growth than did Chlorella sp. (AT). Peneroplis planatus and P. pertusus grew (10-40%) in the light when starved or given a nutrient supplement of 1.0 {dollar}mu{dollar}g at 1{dollar}sp{lcub}-1{rcub}{dollar} NO{dollar}sb{lcub}3sp-{rcub}{dollar} and/or 0.1 {dollar}mu{dollar}g at 1{dollar}sp{lcub}-1{rcub}{dollar} PO{dollar}sb4sp{lcub}-2{rcub},{dollar} but specimens fed unialgal or multialgal diets grew an order of magnitude more; P. pertusus grew larger than did P. planatus, and formed nearly 25% more chambers. P. planatus collected from Japan were physiologically different from the specimens of P. planatus from the Red Sea. Morphological variation seen in the laboratory was not strictly a result of genetic factors, since clones from the same parental cell grew differently. The carbon budget and flux of carbon through the Peneroplis planatus - Porphyridium purpureum association was examined. In continuous light, P. planatus incorporated inorganic C at a rate of 0.336 {dollar}pm{dollar} 0.024 {dollar}mu{dollar}g C mg{dollar}sp{lcub}-1{rcub}{dollar} foraminifer h{dollar}sp{lcub}-1{rcub}.{dollar} Respiration measured 0.0405 {dollar}mu{dollar}g C mg{dollar}sp{lcub}-1{rcub}{dollar} foraminifer h{dollar}sp{lcub}-1{rcub}.{dollar} A carbon flow model for an average sized adult P. planatus is ({dollar}sim{dollar}600{dollar}mu{dollar}m long, 47.6 {dollar}mu{dollar}g, with {dollar}sim{dollar}4,900 endosymbionts) has been developed which describes C fluxes under constant conditions. The foraminifer grows 0.36 {dollar}mu{dollar}g d{dollar}sp{lcub}-1{rcub}{dollar} and its endosymbiotic population increases by 68 endosymbionts d{dollar}sp{lcub}-1{rcub}.{dollar} Feeding (net assimilated food) provided 0.0723 {dollar}mu{dollar}g C d{dollar}sp{lcub}-1{rcub}{dollar} to the carbon budget of the growing endosymbiotic system. The symbiotic association tightly recycles carbon while in light, whereas in the dark, it looses some carbon by respiration. The endosymbionts fix enough inorganic carbon to satisfy the energetic demands of the entire system. However, in times of reduced photosynthesis, feeding on external algae must supplement this amount, and provide other limiting nutrients.