Ultrastructure of the spirocyst tubule in black corals (Coelenterata: Antipatharia) and its taxonomic implications

Spirocyst tubules in five shallow-water antipatharian species Antipathes pennacea, Antipathes sp. cf. salix, A. fiordensis, A. galapagensis, and Cirrhipathes luetkeni contain an electron-opaque, helically arranged structure, composed of four distinct and separate bundles of microfibril-like material. Each bundle appears to be solid, rather than hollow, and is enveloped by a sheath of lesser electron-opacity that is continuous with the pleats. Tubules from a more distantly related, deep-water antipatharian, are similarly configured but are composed of only three distinct bundles, separated from one another by electron-opaque sheath material. The bundles are electron-lucent; their substructure was not preserved because this specimen was prepared for microscopy after preservation in alcohol for 27 yr, apparently without initial fixation. Most other details of the spirocyst tubule and capsule can be determined from this museum specimen. The arrangement within the tubule of multiple bundles, clearly defined by sheaths, is structurally distinct from other zoantharian spirocysts, and appears to be unique to the Antipatharia. The tubule structure of the anemone Aiptasia sp., examined for comparison, is consistent with that of spirocysts from other actiniarians and zoantharians generally, including the appearance of electron-opaque rodlets within the tubule lumen. No substructural information was obtained from Aiptasia sp. rodlets. It is unclear whether the microfibrillar bundles of antipatharian spirocysts differ from those of other zoantharians by being more amenable to resolution, or if their tubule substructure is fundamentally distinct from those of more typical zoantharians. In terms of overall structure, Aiptasia sp. spirocyst tubules contain a single bundle of rodlets without a clearly defined sheath, in contrast to antipatharians which have three or four bundles, each clearly defined. These structural differences may be useful in determining relationships both within the Antipatharia, and between antipatharians and allied orders.     

Aggregations and offshore movements as indicators of spawning activity of bonefish (Albula vulpes) in The Bahamas

To identify the timing and location of spawning activity for bonefish (Albula spp.) in the Bahamian archipelago, we used an acoustic telemetry array spanning 44?km² of shallow tidal creeks, flats, and adjacent deeper coastal waters near Cape Eleuthera. In two successive years, we surgically implanted transmitters in male and female bonefish (n?=?60) and examined their movement patterns within the array. Eight bonefish surgically implanted with transmitters as part of an earlier study were also tracked. In 2009, the telemetry information was complemented with snorkeling observations, underwater video, and manual tracking of the same acoustically tagged fish, as well as fish (n?=?3) gastrically implanted with continuous transmitters. During a period of 4?C7?days spanning the full and new moons, primarily between October and May, bonefish moved from their typical shallow flats and aggregated at sites in close proximity to the deep water drop-off of the Exuma Sound. Localized movements of the large schools of bonefish (often?>1,000 fish) at these presumptive pre-spawning aggregation sites included brief trips (<8?h) just after sunset until just prior to sunrise to the abyssal wall at the edge of the Exuma Sound (i.e.,?>1,000?m depth). Tagged bonefish detected at these aggregation sites were subsequently detected back in the tidal creeks and coastal flats shortly after new and full moons and remained at these more typical shallow sites (i.e.,?<2?m depth). Although we did not directly observe spawning events, we did observe ventral nudging and porpoising behaviors, which are potentially associated with courtship. Timing of the observed movements and possible courtship behaviors was coincident with periods when gametes were well developed. Collectively, our study provides the first objective evidence suggesting that the aggregation and seasonal migration of bonefish to deep shelf environments during certain moon phases is for spawning.