Marsh J. Youngbluth

The ultrastructure of oogenesis and yolk formation in Labidocera aestiva (Copepoda: Calanoida)

Yolk formation in the oocytes of the free‐living, marine copepod, Labidocera aestiva (order Calanoida) involves both autosynthetic and heterosynthetic processes. Three morphologically distinct forms of endogenous yolk are produced in the early vitellogenic stages. Type 1 yolk spheres are formed by the accumulation and fusion of dense granules within vesicular and lamellar cisternae of endoplasmic reticulum. A granular form of type 1 yolk, in which the dense granules within the cisternae of endoplasmic reticulum do not fuse, appears to be synthesized by the combined activity of endoplasmic reticulum and Golgi complexes. Type 2 yolk bodies subsequently appear in the ooplasm but their formation could not be attributed to any particular oocytic organelle.

Chemical composition, metabolic rates and feeding behavior of the midwater ctenophore Bathocyroe fosteri

Individuals of the midwater ctenophore Bathocyroe fosteri (0.01 to 1.6 g dry weight, DW) were collected from Bahamian waters by the submersible “Johnson-Sea-Link” during May and September/October 1983 and October/November 1984 from 530 to 700 m depth. Metabolic rates were measured and showed oxygen consumption to be in the range of 0.01 to 0.18 mg O2 g-1 DW h-1 at temperatures ranging from 9° to 12°C. Ammonium excretion (0.01 to 0.14 μg-at N g-1 DW h-1) was typically low. Energy expenditures estimated from respiration data (ca. 7% body C d-1) indicated that one to three midwater crustacean prey (ca. 150 μg C d-1) could provide the daily maintenance ration required by a 40 mm ctenophore. These metabolic characteristics complemented in situ observations of poor locomotor ability and passive feeding behavior.

Fecal pellet production and diel migratory behavior by the euphausiid Meganyctiphanes norvegica effect benthic-pelagic coupling

Abstract Observations made during submersible dives revealed that high densities of fecal pellets (50–325 particles m −3 ) accumulated at night in 5–24 m thick layers coincident with the pycnocline (15–30 m) within the Gulf of Maine and the canyons south of Georges Bank. These large, cylindrical (0.2 mm × 3–10 mm long) particles sank rapidly ( ca 204 m d −1 ± 24 S.E.) and could transport substantial amounts of organic matter (7–12 mg C m −2 d −1 ) to the bottom. Vertically migrating euphausiids, Meganyctiphanes norvegica , produced the pellets. These individuals represented only part of enormous aggregations (up to 10 4 individuals m −3 ) of adults (25–35 mm long) that remained within 10 m of the seabed day and night and appeared to forage in the benthic boundary region. These discoveries reveal that environmental factors and zooplankton behaviors can influence the rate and amount of particle flux. Furthermore, the unexpected observations of prodigious, epibenthic stocks of krill disclosed the distribution of major food resources that have supported the centuries-old fisheries in this region.

Heterotrophic activity on appendicularian (Tunicata: Appendicularia) houses in mesopelagic regions and their potential contribution to particle flux

Repeated observations and collections of appendicularian houses (ca 1–10 cm dia.) from Johnson-Sea-Link submersibles indicate these conspicuous mucoid aggregates (0.08–0.49 houses m−3) were a common component of the biodetritus at midwater depths (490–760 m) in Bermuda and the Bahamas during May and November 1984, respectively. Microorganisms and olive-green bodies found on these houses were 1–3 orders of magnitude more numerous than in an equal volume of surrounding seawater. The production rates of bacteria on aggregates varied from 0.01 to 10.83 ng C house−1 h−1 and accounted for 0.01–4.0% of total bacterial production in the water column. The potential carbon flux from these large particles amounted to 0.83 mg C m−2 day−1 (=8% of total carbon flux).

Radio-Tracking and Survivorship of Two Rehabilitated Bottlenose Dolphins ( Tursiops truncatus ) in the Indian River Lagoon, Florida

Despite an increase in the number of stranded dolphins rehabilitated and returned to the wild, the survivorship of these cetaceans is poorly documented. Since rehabilitation and release programs remain limited in scope, the release of dolphins from different age and sex cohorts provides information that is pertinent to protocols for future release candidates. Novel opportunities to track the survivorship of two rehabilitated bottlenose dolphins with radio transmitters occurred in 2001 and 2003 in the Indian River Lagoon (IRL), Florida. Both dolphins were male and had been identified prior to rehabilitation during a photoidentification monitoring program. Dolphin C6 stranded with multiple life-threatening shark wounds in 2000, at age 24, and was released after a successful 6-mo period of rehabilitation. This dolphin re-established an existing male pair-bond with dolphin C7, traveled 67 km from the release site, and survived 100 d before he died from asphyxiation by an exotic fish that lodged in his pharynx. Carter, a calf orphaned in 2003 at 1 y of age, was released following a 3-mo period of care that provided adequate nutrition and weight gain needed for survival in the wild. This young dolphin remained within a 10-km radius of the release site, failed to form a stable relationship with other dolphins, and appeared to have survived only 7 d when radio transmissions from an acoustic tag ceased. These two cases represent the radio-tracking studies of the oldest and youngest known bottlenose dolphins rehabilitated and released in the IRL.