New observations on the rare physonect Melophysa melo (Siphonophora; Agalmatidae) from the northern Gulf of Mexico.

The rare short-stemmed physonect Melophysa melo typically lives above the thermocline in warm waters of the world's oceans. In the past this species has been described from fragmented or distorted material, with the last two accounts being published in 1931 and 1954. A new description is given herein with pertinent figures based on nine samples recently collected in the Gulf of Mexico (GoM), including the first detailed illustrations of mature nectophores, and of a well-developed corm. The corm comprises a prominent pneumatophore, a narrow nectosome bearing small attachment lamellae for four nectophores and a much larger short, swollen spiral siphosome bearing eight cormidia. The last five cormidia of this corm are still attached to the pneumatophore, while the oldest three are free, with cormidium one being the oldest and eight the youngest. Two rings of bracteal muscular lamellae occur on the siphosome of this corm, one on the upper surface of each cormidium and a second on the lower surface. Laterally each cormidium supports an upper gonodendron, a zooid meridian bearing palpons and a lower gonodendron. Cormidium one has the most mature gonodendra, and all cormidia have palpons on the zooid meridian, which become progressively mature towards the base. Differences in corm structure from previously described corms are attributed to the younger age of the present two corms. Bracts are re-described from photographic images of both young and mature bracts.

High Abundance of the Epibenthic Trachymedusa Ptychogastria polaris Allman, 1878 (Hydrozoa, Trachylina) in Subpolar Fjords along the West Antarctic Peninsula.

Medusae can be conspicuous and abundant members of seafloor communities in deep-sea benthic boundary layers. The epibenthic trachymedusa, Ptychogastria polaris Allman, 1878 (Hydrozoa: Trachylina: Ptychogastriidae) occurs in the cold, high latitude systems of both the northern and southern hemispheres, with a circumpolar distribution in Arctic and sub-Arctic areas, and disjunct reports of a few individuals from Antarctica. In January-February 2010, during benthic megafaunal photosurveys in three subpolar fjords along the West Antarctic Peninsula (Andvord, Flandres and Barilari Bays), P. polaris was recorded in Antarctic Peninsula waters. The trachymedusa, identified from megacore-collected specimens, was a common component of the epifauna in the sediment floored basins at 436-725 m depths in Andvord and Flandres Bays, reaching densities up to 13 m-2, with mean densities in individual basins ranging from 0.06 to 4.19 m-2. These densities are 2 to 400-fold higher than previously reported for P. polaris in either the Arctic or Antarctic. This trachymedusa had an aggregated distribution, occurring frequently in Andvord Bay, but was often solitary in Flandres Bay, with a distribution not significantly different from random. Epibenthic individuals were similar in size, typically measuring 15-25 mm in bell diameter. A morphologically similar trachymedusa, presumably the same species, was also observed in the water column near the bottom in all three fjords. This benthopelagic form attained abundances of up to 7 m-2 of seafloor; however, most P. polaris (~ 80%), were observed on soft sediments. Our findings indicate that fjords provide a prime habitat for the development of dense populations of P. polaris, potentially resulting from high and varied food inputs to the fjord floors. Because P. polaris resides in the water column and at the seafloor, large P. polaris populations may contribute significantly to pelagic-benthic coupling in the WAP fjord ecosystems.

Home ranges of bottlenose dolphins (Tursiops truncatus) in the Indian River Lagoon, Florida: environmental correlates and implications for management strategies.

Photo-identification surveys conducted between 2002 and 2005 were used to determine dolphin home ranges and site fidelity within the Indian River Lagoon (IRL), Florida. The IRL was divided into six segments based on hydrodynamics and geographic features for purposes of characterization. Among the 615 dolphins with identifiable dorsal fins, 339 had > or =6 sightings and were used in segment and linear range analyses. The majority (98%) of dolphins were seen in < or =3 consecutive segments (331/339); of these, 44% (144/331) occurred in two segments, and 33% (109/331) in one segment. No dolphins were observed in all six segments. The largest number of dolphins was sighted in segment 1C (North Indian River). However, the highest density of dolphins was found in segment 2 (North-Central Indian River). Re-sighting rates for dolphins with > or =6 sightings ranged from 2.8 to 8.7 times observed. The mean linear home range varied from 22 to 54 km. Distributional analyses indicated that at least three different dolphin communities exist within the IRL: Mosquito Lagoon, and the North and South Indian River. No statistically significant correlations were found between the total number or density per km(2 )of dolphins and surface water area, salinity, or contaminant loads within segments of the lagoon. These results suggest that dolphins do not selectively avoid areas with relatively unfavorable water quality. IRL dolphins should be studied on smaller spatial scales than currently practiced, and potential anthropogenic impacts should be evaluated based on geographic partitioning.

Ultrastructure of the "pigment knob" of Pleuromamma spp. (Copepoda: Calanoida).

The calanoid copepod genus Pleuromamma is easily distinguished from all other copepods by the presence of a rounded, dark-red cuticular structure ( = pigment knob) that protrudes from the left or right side of the second thoracic segment in both sexes. The present study of the pigment knob reveals a complex ultrastructure consisting of various cell types within three distinct areas that are bathed by hemolymph from the lateral sinus. The knob is covered by a greatly expanded cuticle through which a pore passes. The pore appears to connect with a centrally positioned pigment cell containing a large mass of darkly staining granules. This suggests that the knob may have a secretory function. Observations of live animals and dissected pigment knobs, however, indicates that the knob does not secrete a luminescent material nor does it luminesce internally.