No abstract

No abstract

Larvaceans, common members of marine plankton communities, filter-feed with renewable, external, mucous houses. The houses of some species of Oikopleuridae produce endogenous bioluminescent flashes upon mechanical stimulation and may contribute significantly to surface luminescence. To determine which members of the Oikopleuridae are luminescent, we examined several species for stimulable luminescence and for morphological features responsible for or associated with light production. Luminescence is newly reported from house rudiments and from clean, particle-free houses ofOikopleura rufescens and Stegosoma magnum. In these species, light emanates from previously undescribed fluorescent inclusions in the house rudiment. Neither fluorescence nor luminescence were detected from other parts of the body. Both species also possess oral glands, which apparently are not directly involved in light production but serve as a convenient taxonomic marker of luminescence. All six known luminescent species of larvaceans possess fluorescent and luminescent house rudiment inclusions and oral glands. We predict on these morphological grounds that all twelve species of Oikopleura (Vexillaria) plus the oikopleurids S. magnum and Folia gracilis are luminescent. In two other oikopleurids that lack oral glands, O. fusiformis and Megalocercus huxleyi, neither fluorescent inclusions nor luminescence were detected in clean houses and animals with house rudiments. However, some field-collected houses of these species produced luminescent flashes, perhaps from dinoflagellates on or in the houses. This report should facilitate assessment of the contribution of larvaceans to surface luminescence on a global scale.

Luminescent flashes emanate spontaneously and on mechanical stimulation from the bodies of Oikopleura dioica (Urochordata, Larvacea); flashes also emanate, on mechanical stimulation only, from both their occupied and discarded mucous houses. The luminescence is intrinsic to the animals and their houses. Field observations suggest that, because of this dual method of light production, larvaceans may contribute substantially to surface coastal displays of marine bioluminescence.

ABSTRACT. The ectoparasitic dnoflagellate Apodinlum floodi n. sp. is reported from the pelagic tunicate Oikopleura labradoriensis (Phylum Chordata, Subphylum Urochordata, Class Larvacea). The trophozoite of A. flood, which reaches 890 pm in length, is encased by a membranous envelope and is attached to the tail of the host. Divisions of the young trophozoite produce an elongate, single file of sporogenic cells. Later, divisions perpendicular to the long axis of the trophozoite occur in distal sporogenic cells, and ultimately dinospores are produced. An attachment organelle or peduncle penetrates the host's musculature, crosses the hemocoel and reaches the notochord; at that level, 2 principal rhizoids, each provided with a condyle, a dense lining, and an absorptive outer layer of tubules, diverge from the peduncle and invade the outer region of the notochord. Tumor-like growths in the lumen of the notochord, and other abnormal proliferations of the host's cells, occur