Michael Vecchione

Does Presence of a Mid-Ocean Ridge Enhance Biomass and Biodiversity?

In contrast to generally sparse biological communities in open-ocean settings, seamounts and ridges are perceived as areas of elevated productivity and biodiversity capable of supporting commercial fisheries. We investigated the origin of this apparent biological enhancement over a segment of the North Mid-Atlantic Ridge (MAR) using sonar, corers, trawls, traps, and a remotely operated vehicle to survey habitat, biomass, and biodiversity. Satellite remote sensing provided information on flow patterns, thermal fronts, and primary production, while sediment traps measured export flux during 2007–2010. The MAR, 3,704,404 km2 in area, accounts for 44.7% lower bathyal habitat (800–3500 m depth) in the North Atlantic and is dominated by fine soft sediment substrate (95% of area) on a series of flat terraces with intervening slopes either side of the ridge axis contributing to habitat heterogeneity. The MAR fauna comprises mainly species known from continental margins with no evidence of greater biodiversity. Primary production and export flux over the MAR were not enhanced compared with a nearby reference station over the Porcupine Abyssal Plain. Biomasses of benthic macrofauna and megafauna were similar to global averages at the same depths totalling an estimated 258.9 kt C over the entire lower bathyal north MAR. A hypothetical flat plain at 3500 m depth in place of the MAR would contain 85.6 kt C, implying an increase of 173.3 kt C attributable to the presence of the Ridge. This is approximately equal to 167 kt C of estimated pelagic biomass displaced by the volume of the MAR. There is no enhancement of biological productivity over the MAR; oceanic bathypelagic species are replaced by benthic fauna otherwise unable to survive in the mid ocean. We propose that globally sea floor elevation has no effect on deep sea biomass; pelagic plus benthic biomass is constant within a given surface productivity regime.

'Lophenteropneust' hypothesis refuted by collection and photos of new deep-sea hemichordates.

The deep ocean is home to a group of broad-collared hemichordates—the so-called ‘lophenteropneusts’—that have been photographed gliding on the sea floor but have not previously been collected. It has been claimed that these worms have collar tentacles and blend morphological features of the two main hemichordate body plans, namely the tentacle-less enteropneusts and the tentacle-bearing pterobranchs. Consequently, lophenteropneusts have been invoked as missing links to suggest that the former evolved into the latter. The most significant aspect of the lophenteropneust hypothesis is its prediction that the fundamental body plan within a basal phylum of deuterostomes was enteropneust-like. The assumption of such an ancestral state influences ideas about the evolution of the vertebrates from the invertebrates. Here we report on the first collected specimen of a broad-collared, deep-sea enteropneust and describe it as a new family, genus and species. The collar, although disproportionately broad, lacks tentacles. In addition, we find no evidence of tentacles in the available deep-sea photographs (published and unpublished) of broad-collared enteropneusts, including those formerly designated as lophenteropneusts. Thus, the lophenteropneust hypothesis was based on misinterpretation of deep-sea photographs of low quality and should no longer be used to support the idea that the enteropneust body plan is basal within the phylum Hemichordata.

Cephalopods of the northern Mid-Atlantic Ridge

Abstract A two-leg cruise of R/V G. O. Sars in summer of 2004 along the Mid-Atlantic Ridge explored the diversity and distribution patterns of pelagic and non-hydrothermal bottom communities in the vicinity of the northern Mid-Atlantic Ridge. In total, 1295 cephalopods were caught, representing 56 species. Differences in species composition and size were apparent among the various types of trawls used. The Aakra trawl and bottom trawl caught the largest numbers of species (38 and 34, respectively); size of cephalopods was directly related to the size of the net. Many more species were caught in the southern part of the study area than farther north. The most abundant species was Gonatus steenstrupi, found mostly in the northern part of the study area. A few abundant species, such as Mastigoteuthis agassizii, were found throughout the region, with no clear indication that their northern or southern distributional limits occur within the area sampled. Several benthic and one pelagic species, all taken in small numbers, were captured only in the region of the Charlie Gibbs Fracture Zone. We found many species at very low numbers (i.e. 37 species with <10 specimens in all gear types combined).

A new species of Pareledone (Cephalopoda : Octopodidae) from Antarctic Peninsula Waters

During recent cruises aboard RV Polarstern in the Antarctic Peninsula region, a new species of benthic octopodid was discovered whose generic affinities based on morphological characteristics were uncertain. Molecular sequence analysis of six mitochondrial and nuclear genes allows this species to be placed with confidence within the genus Pareledone. The species is described herein and morphological diagnostic characters are provided for its identification.

The ink sac clouds octopod evolutionary history

Difficulties in elucidating the evolutionary history of the octopods have arisen from problems in identifying informative morphological characters. Recent classifications have divided the largest group, the incirrate octopods, into five groups. These include the pelagic superfamily Argonautoidea and three gelatinous pelagic families (Vitreledonellidae, Bolitaenidae, Amphitretidae). All benthic incirrate octopods have been accommodated in the family Octopodidae, itself divided into four subfamilies, Octopodinae, Eledoninae, Bathypolypodinae and Graneledoninae, which are defined by the presence or absence of an ink sac, and uniserial or biserial sucker arrangements on the arms. We used relaxed clock models in a Bayesian framework and maximum likelihood methods to analyse three nuclear and four mitochondrial genes of representatives from each of the previous subfamilies. Strong evidence indicates that the family Octopodidae is paraphyletic and contains the gelatinous pelagic families. The subfamilies of Octopodidae recognised in earlier works do not reflect evolutionary history. The following clades were supported in all analyses: (1) Eledone/Aphrodoctopus, (2) Callistoctopus/Grimpella/Macroctopus/Scaeurgus, (3) Abdopus/Ameloctopus/Amphioctopus/Cistopus/Hapalochlaena/Octopus, (4) Enteroctopus/Muusoctopus/Vulcanoctopus, (5) Vitreledonella/Japetella, (6) Southern Ocean endemic and deep-sea taxa with uniserial suckers. These clades form the basis for a suite of taxa assigned family taxonomic rank: Amphitretidae, Bathypolypodidae, Eledonidae, Enteroctopodidae, Megaleledonidae and Octopodidae sensu nov. They are placed within the superfamily Octopodoidea.

ROV observations of benthic fishes in the Northwind and Canada Basins, Arctic Ocean

Abyssal and midslope Arctic benthic fishes were sampled nonquantitatively by still photography and videography from a remotely operated vehicle (ROV) between 13 August and 7 September 2002. Species diversity was low: only six putative species were seen, including Lycodes frigidus Collett 1879, Lycodes sp., Rhodichthys regina Collett 1879, Paraliparis bathybius (Collett 1879), Raja (Amblyraja) hyperborea Collett 1879, and Cottunculus species diversity varied among stations sampled. An analysis of 1-min segments of videotape from one long ROV dive suggested that habitat selection by demersal nekton in these environments may be associated with the presence, absence, or density of other benthic animals.

Benthoctopus rigbyae, n. sp., a new species of cephalopod (Octopoda; Incirrata) from near the Antarctic Peninsula

ABSTRACT Among the many octopods collected during recent Antarctic trawling surveys were 93 specimens of an undescribed octopod with biserial suckers. Although most similar in appearance to the sub-Antarctic Benthoctopus levis (Hoyle 1885), these octopods differed in several morphological characters, including arm length, web depth, and details of the hectocotylus. Furthermore, molecular evidence supports the separation of the present material from known species. We therefore describe a new species named Benthoctopus rigbyae. These octopods attain mantle lengths of at least 105 mm (400 mm total length), and they are common at depths of 250–600 m throughout the South Shetland Island chain off the Antarctic Peninsula. We present some information on the biology of this species.

Biology of the cirrate octopod Grimpoteuthis glacialis (Cephalopoda; Opisthoteuthididae) in the South Shetland Islands, Antarctica

The capture of 52 specimens of the cirrate octopod Grimpoteuthis glacialis (Robson, 1930), of dorsal mantle length 20-165 mm during a 1996 trawling survey near the Antarctic Peninsula allowed the basic biology of the species to be examined. Their presence in bottom trawls at depths of 333-879 m, but their absence from benthopelagic and pelagic trawls, is consistent with a primarily benthic habitat. The largest single sample, 40 animals, came from a soft mud bottom and highlights the patchy nature of the distribution. Males tended to be bigger in total length and mass than females of similar mantle length. The males, however, were mature at a smaller size. Mature males have tiny sperm packets, rather than typical cephalopod spermatophores, in their distal reproductive tract. Mature females have large, smooth eggs in the proximal oviduct, in the huge oviducal gland and in the distal oviduct. Eggs in the distal oviduct have a thick, sticky coating that hardens in seawater into a secondary egg case. Ovarian eggs vary greatly in size, possibly indicating protracted egg laying. Observations on live animals indicate that the species swims primarily by fin action, rather than by jetting or medusoid pulses with the arm/web complex. It may be capable of limited changes in colour pattern, especially on the oral surface of the web. Three pairs of surface structures that appear superficially to be white spots anterior to the eyes and near the bases of the fins are actually transparent patches in the skin. When considered in association with the transparent subdermal layer and the anatomy of the eyes, optic nerves and optic lobes, these clear patches seem to function in detecting unfocused light on the horizontal plane of the benthic animal.

First in situ observations of the deep-sea squid Grimalditeuthis bonplandi reveal unique use of tentacles

The deep-sea squid Grimalditeuthis bonplandi has tentacles unique among known squids. The elastic stalk is extremely thin and fragile, whereas the clubs bear no suckers, hooks or photophores. It is unknown whether and how these tentacles are used in prey capture and handling. We present, to our knowledge, the first in situ observations of this species obtained by remotely operated vehicles (ROVs) in the Atlantic and North Pacific. Unexpectedly, G. bonplandi is unable to rapidly extend and retract the tentacle stalk as do other squids, but instead manoeuvres the tentacles by undulation and flapping of the clubs’ trabecular protective membranes. These tentacle club movements superficially resemble the movements of small marine organisms and suggest the possibility that G. bonplandi uses aggressive mimicry by the tentacle clubs to lure prey, which we find to consist of crustaceans and cephalopods. In the darkness of the meso- and bathypelagic zones the flapping and undulatory movements of the tentacle may: (i) stimulate bioluminescence in the surrounding water, (ii) create low-frequency vibrations and/or (iii) produce a hydrodynamic wake. Potential prey of G. bonplandi may be attracted to one or more of these as signals. This singular use of the tentacle adds to the diverse foraging and feeding strategies known in deep-sea cephalopods.

Mastigoteuthis microlucens, a new species of the squid family Mastigoteuthidae (Mollusca: Cephalopoda)

ABSTRACT We describe a new species, Mastigoteuthis microlucens, of the family Mastigoteuthidae from the tropical North Pacific. Its most distinctive morphological character is the presence of microscopic photophores in the integument. Morphological data indicate that its closest relative is the Atlantic Ocean species Mastigoteuthis magna. Molecular data from three genes, based on four species for which molecular data is available, indicates that Mastigoteuthis microlucens differs from its closest relative, M. magna, by a sufficient degree to substantiate its separate species status.