Eurythenes S.I. Smith
- Dataset
- Contribution to the systematics of the genus Eurythenes S. I. Smith in Scudder, 1882 (Crustacea: Amphipoda: Lysianassoidea: Eurytheneidae)
- Rank
- GENUS
Classification
- kingdom
- Animalia
- phylum
- Arthropoda
- class
- Malacostraca
- order
- Amphipoda
- family
- Lysianassidae
- genus
- Eurythenes
biology_ecology
Biology. Eurythenes obesus is a pelagic species, of which the biology is poorly known, whilst other Eurythenes species are benthopelagic, E. thurstoni being more confined to the pelagic realm than the species of the E. gryllus - complex or E. gryllus s. l. (Stoddart & Lowry 2004). A substantial corpus of biological literature exists for this species complex. It has to be reviewed collectively because the pseudocyptic species described herein have not been previously separated, assuming that their overall biology is reasonably similar. Barnard (1962) stated that, " morphologically, E. gryllus s. l. is more pelagic than benthic, but obviously feeds on the bottom ”, but Bowman & Manning (1972) found that “ the heavy compact body seems poorly adapted for a continuous pelagic existence, even though the heavily muscled pleon indicates that E. gryllus is a strong swimmer ". Subsequent papers repeatedly confirmed that E. gryllus s. l. is a benthopelagic species and Thurston (1990) gave an extensive list of papers recording E. gryllus s. l. in the water column, often far above the abyssal sea floor. An extreme case is the record 1800 m above the bottom by Baldwin & Smith (1987). According to observations in the European Basin by Christiansen et al. (1990), it is predominantly found in the first 15 m above the sea floor; juveniles and large females being exclusively found in the first 50 m above the bottom; adult males have a bimodal distribution with maxima at 15 and 300 m above the bottom; isolated specimens were observed 1000 m above the sea floor. Baldwin & Smith (1987), who made fairly similar observations on populations from the central and eastern North Pacific, suspected that juvenile Eurythenes remain close to the bottom due to larger food supplies and the possibility to seek refuge in the sediment as a protection from predation. Concerning pelagic specimens, Ingram & Hessler (1983) state that: " The bathymetric distribution of E. gryllus implies that individuals probably spend long periods above the sediment searching for food. Those that live hundreds of meters above the sediment might only rarely, if ever, descend to the sediment. Such behavior would be energetically expensive unless E. gryllus were neutrally buoyant or nearly so. Their primary energy store, lipids, may aid in maintaining the neutral buoyancy that would require little if any energy expenditure for staying in the water column. " The data of Baldwin & Smith (1987) suggest that Eurythenes gryllus s. l. has a continuous recruitment, as there is no size class progression along with the annual cycle. Hatchlings are 11 mm long (Thurston & Bett 1995) and according to Ingram & Hessler (1987), in E. gryllus s. l. from the central North Pacific, males mature at instar VIII (mean length 70 mm) and females at instar XV (mean length 109 mm); both males and females are mature through several instars and females can have multiple broods; they estimate that females mature at 9 years and males at 4 years. However, according to Thurston & Bett (1995) the relationship between the size and the instars as calculated by Ingram & Hessler (1987) requires minor adjustments. Adult females with setose oostegites are uncommonly recorded and have very soft teguments compared to males and females in non-brooding intermoult (Ingram & Hessler 1987, Thurston & Bett 1995). The only brooding female ever caught (bearing hatchlings, not eggs) was caught with a midwater trawl 1500 m above the seafloor, suggesting pelagic incubation, at a depth range where predators are scarce (Thurston & Bett 1995). We hypothesise that soft (i. e. lighter) teguments would ensure a better buoyancy — hence a reduced energetic budget — during the presumably non-feeding pelagic brooding stage and that females descend to the bottom for releasing their hatchlings.
description
Description. See description of family Eurytheneidae by Stoddart & Lowry (2004). Composition. In the present paper, seven Eurythenes species are recognized: E. andhakarae sp. nov., E. gryllus (Lichtenstein in Mandt, 1822), E. magellanicus (H. Milne Edwards, 1848), E. maldoror sp. nov., E. obesus (Chevreux, 1905), E. sigmiferus sp. nov., and E. thurstoni Stoddart & Lowry, 2004. DNA sequences of specimens not directly examined and morphological observations published in literature are indicative of the existence of further species. Nomenclature issues. The name Eurythenes was erected in very unusual manner, and has been a source of confusion for more than a century. Lilljeborg (1865 a) created the genus Eurytenes (without " h ") for Lysianassa magellanica H. Milne Edwards, 1848 (currently Eurythenes magellanicus) but this name was preoccupied by Eurytenes Förster, 1862 (Hymenoptera). On page 135 of the first part of the book by Scudder (1882) (Supplemental list of genera in Zoölogy), ' Eurythenes Lilljeborg. Nova Acta Soc. Sc. Upsal., vii, p. 11. 1865. Crust., Amph. Smith. ' is listed. Column 3 of page 122 of the second part of Scudder (1882) (Universal index to genera in Zoölogy) lists ' Eurytenes Först., Hym. 1862 M. ' and two lines below ' Eurythenes Lillj. Crust. 1865. S. ' Chevreux (1889) made the following statement (freely translated from French): ' Since Eurytenes was used by Förster for a new genus of Hymenoptera, Smith has slightly modified the spelling of the name proposed by Lilljeborg (1865), so that it remains phonetically identical. In this paper, I keep that spelling of Smith, although I consider the procedure which he followed highly inappropriate'. G. O. Sars (1891) proposed the name Euryporeia G. O. Sars, 1891 as a replacement name for Eurytenes Lilljeborg, 1865, with the following justification: ' In 1865 Prof. Lilljeborg established this genus to include the remarkable gigantic form described by Milne Edwards under the name of Lysianassa magellanica. The denomination Eurytenes proposed by him having, however, been before adopted for a genus of Hymenoptera, I have changed the latter half of the compound, still conserving the signification of the name as intended by Prof. Lilljeborg. ' Fifteen years later, in his classical revision of gammaridean amphipods, Stebbing (1906) implicitly treated Eurythenes S. I. Smith, 1882 as a replacement name validly introduced for Eurytenes Lilljeborg, 1865. Between 1893 and 1925, a few authors adopted Euryporeia (see the list given by Stoddart & Lowry 2004), but otherwise the point of view of Stebbing (1906) became prevalent and, after 1925, universally accepted. The listing of both ' Eurytenes Först. ' and ' Eurythenes Lillj. ' in the second part of the book of Scudder (1882), which was overlooked by previous authors, clearly indicates that the spelling modification was deliberate and was intended to be a replacement name sensu ICZN (1999) Art. 60.3. As the change operated by Smith has been done within a book authored by Scudder and not by him, it seems advisable to indicate the authority of the genus Eurythenes as ' Smith in Scudder, 1882 ' and not simply as ' Smith, 1882 ' as it is usually the case. The name Eurysthenes S. I. Smith, 1884 b has been interpreted as a typographical error (Stoddart & Lowry 2004), since the paper of S. I. Smith (1884 b) is a reprint of S. I. Smith (1884 a), where the spelling Eurythenes is used.
etymology
Etymology. Lilljeborg (1965 a) indicated the following etymology of Eurytenes: ' On account of its extensive geographical distribution, we give to this genus the name Eurytenes, from the Greek ' εύρυτεής, which signifies widely stretched'.
Name
- Homonyms
- Eurythenes
- Eurythenes S.I. Smith
- Eurythenes