Robert Y. George

Biphasic moulting in Isopod Crustacea and the finding of an unusual mode of moulting in the antarctic genus Glyptonotus

Summary Moulting in Isopod Crustacea usually occurs in two phases and invariably the ecdysis of posterior half precedes the anterior. The hormonal control for regulating such a unique biphasic mode of moulting can only be explained by an effectively functional physiological mechanism probably involving circulatory inhibitions or restricted neurosecretive activities. This paper describes the observations made at McMurdo, Antarctica on an unusual single phase moulting in the endemic antarctic giant isopod Glyptonotus.

Distribution and Probable Origin of the Species in the Deep-Sea Isopod Genus Storthyngura 1)

[Nach morphologischen Merkmalen verteilen sich die 38 bekannten Arten der in der Tiefsee vorkommenden Gattung Storthyngura auf 5 Hauptgruppen. Die geographische Verbreitung der morphologisch verwandten Arten lasst gewisse auffallende Zuge erkennen; alle Gruppen sind in der Antarktis vertreten. Diese Gruppenanalyse macht wahrscheinlich, dass diese Gattung sich in der Antarktis entwickelte und sich zu verschiedenen Zeiten der erdgeschichtlichen Vergangenheit auf die anderen Weltmeere ausgedehnt hat., Nach morphologischen Merkmalen verteilen sich die 38 bekannten Arten der in der Tiefsee vorkommenden Gattung Storthyngura auf 5 Hauptgruppen. Die geographische Verbreitung der morphologisch verwandten Arten lasst gewisse auffallende Zuge erkennen; alle Gruppen sind in der Antarktis vertreten. Diese Gruppenanalyse macht wahrscheinlich, dass diese Gattung sich in der Antarktis entwickelte und sich zu verschiedenen Zeiten der erdgeschichtlichen Vergangenheit auf die anderen Weltmeere ausgedehnt hat.]

Desmosomatidae and Nannoniscidae (Crustacea, Isopoda, Asellota) from bathyal and abyssal depths off North Carolina and their evolution

The deep-sea asellote isopod (Crustacea) species, belonging to the families Desmosomatidae and Nannoniscidae, were studied from R/V Eastward collections of Duke University from three study sites off North Carolina. The Desmosomatid isopod Eugerda svavarssonni n. sp. is described from Site Alpha at 620m. Eugerda latipes Hansen, previously known from boreal North Atlantic, is also reported from this upper slope site. Two new desmosomatid isopods, Mirabilicoxa hessleri n. sp. and M. alberti n. sp., and a new nannoniscid isopod Exiliniscus chandravoli n. sp. are also described from site Beta from 2700 to 3700 m. A nannoniscid isopod Leutziniscus jebamoni gen n., n. sp., and a desmosomatid isopod, Prochelator sarsi n. sp., are described from the deepest study site Omega in the Hatteras Abyssal Plain. A new genus, Nannoniscella is erected to accommodate Nannoniscoides bicustatus Siebenaller and Hessler, 1977. This paper also includes discussions on comparative morphology and sexual dimorphism in species of Mirabilicoxa, zoogeography of species of the genus Eugerda and phylogeny with emphasis on the genus Prochelator.

A re-evaluation of the concept of hadal or ultra-abyssal fauna

Abstract Re-examination of the characteristics of the hadal auct . ultra-abyssal elaborated by Wolff (1960) and Belyaev (1966) reveals no significant differences between the isopods from nonhadal depths and those from hadal depths. Trenches exist which have a maximum depth less than 6000 m and therefore we prefer the term trench floor fauna to indicate the fauna living there. Because reliable criteria have not been found which distinguish ‘hadal’ isopods from abyssal isopods we can see no need for the term other than as a convenience. The term ultra-abyssal implies a relationship with abyssal, just as the fauna reveals, accordingly we prefer this term over ‘hadal.’ The more awkward ‘trench floor fauna,’ it appears, is however more meaningful to us than either ultra-abyssal or hadal. The physical parameters of depth and high hydrostatic pressure are the only ingredients peculiar to the life at the bottom of trenches extending below 10,000 m but these two features do not appear to have resulted in the establishment of a fauna with characteristics peculiar to those depths. Obviously the existence of a deep trench floor fauna is not questioned. Instead, the existence of biological criteria separating one from the other and the usage of terminology is questioned.

Hydrostatic Pressure—Temperature effects on Deep-sea Colonisation *

A diverse benthic and bathypelagic fauna was first incontrovertably established by the deep-sea samples of H.M.S. Challenger , and demonstrated the ability of organisms to live and reproduce in the deep, dark and cold abyssal environment of enormous hydrostatic pressure as high as 1000 atm (14 000 psi) on trench floors at 10 000 metres. The investigations of Regnard (1891), Fontaine (1930) and Ebbecke (1935) established that various shallow animals have the capacity to withstand increased hydrostatic pressure. This paper deals with the response of whole organisms, mainly shallow-water metazoans, to hydrostatic pressure-temperature effects. The level of occurrence of pressure-induced increased activity (R 1 ), onset of paralysis or tetany (T) and LD 50 are discussed for tropical and temperate marine species in relationship to temperature and hydrostatic pressure. The pressure sensitivity and resistance exhibited by different species are examined in relation to various hypotheses and theories such as (1) group effect, in which Schlieper (1968) claims that those shallow species that belong to the group which has successfully colonised the deep sea, such as Echinodermata, Mollusca, Isopoda, have a higher pressure resistance; (2) pressure resistance as a species or genetic property; (3) environmental impact, in which deeper species have a greater pressure resistance; and (4) finally a re-examination of temperature and pressure effects as these relate to deep-sea colonisation.