Stegocephalidae is a little-studied
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
of
amphipod
Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descr ...
s belonging to the
suborder
Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...
Gammaridea
Gammaridea is one of the suborders of the order Amphipoda, comprising small, shrimp-like crustaceans. Until recently, in a traditional classification, it encompassed about 7,275 (92%) of the 7,900 species of amphipods described by then, in approx ...
.
Description
Stegocephalids have smooth and globular bodies with a short and deep head. It has small rostrum and the highly modified mouthparts are arranged into a cone structure. the functions of which are unknown but believed to be either for sucking or piercing. The upper part of the lips has a small notch on the distal side, while the lower lip are tall and lack inner lobes. The mandibular molar and palp may be absent or only present in
vestigial
Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...
forms. On the maxilla, the inner plates are setose and well-developed while the palp is often reduced and consists of only a single segment. The maxillipeds are large, often with an inner cutting edge and slender weakly dactylate palps. The eyes are kidney-shaped when present, but is more often completely absent. The antennae possess short peduncles and flagella, with that on the first pair being somewhat stout with fused flagellar segments near the base. In males the first antennal pair is covered with brushlike setae.
On the first four body segments are four very large, non-overlapping, and deep coxal plates, forming a sort of skirt on the front half of the body. The fourth plates are subovate in shape and are the largest. The gnathopods may are slender and may possess small claws or none at all. The third to seventh pereopods are roughly the same size, with the seventh pair being the shortest. The pleon plates on the sides of the body are deep with strong pleopods. The three uropods possess rami that are about the same size and are lanceolate in shape. Their tips extend past the telson. The telson may be composed of lobes fused at the base and tapering to sharp point; or the lobes may be completely fused together to form a small plate.
Distribution and habitat
Stegocephalids are found worldwide, almost exclusively on deep and cold waters.
Ecology
Most of the members of the family are believed to be bathypelagic and free-floating, inhabiting the oceanic water columns at depths of thousands of meters below the ocean surface. They are commonly found with oil globules just underneath their
carapace
A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tor ...
s. These are believed to function as aids in making the animals more buoyant, allowing them to float in the water with little energy expenditure. The smooth, globular shape of the body helps in streamlining the animal while drifting in the water currents, further aided by the animal retracting all its appendages within its coxal plates. The more pelagic the habits of the species, the more elongated they seem to be.
Some species, however, may primarily be
benthic
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...
, inhabiting the surface of the ocean floor in association with megabenthic fauna like
sponge
Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through t ...
s. This includes ''
Parandaniexis mirabilis'' which shows evidence of being a primarily benthic micropredator of
polychaete
Polychaeta () is a paraphyletic class (biology), class of generally marine invertebrate, marine annelid worms, common name, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that ...
s. Their coxal plates are more reduced with more robust peropods adapted to clinging and walking than that of free-floating stegocephalids.
Stegocephalids extend their legs once resting on a substrate. In observations on captive specimens, they do not seem to have the tendency to burrow into the substrate, though this might only be because of the absence of prey in the laboratory substrates.
They are mostly
predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
s of
cnidaria
Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter.
Their distinguishing feature is cnidocytes, specialized cells that th ...
ns, with the exception of the genus ''
Andaniotes'' which are
scavenger
Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...
s.
Taxonomy
Stegocephalidae is the sole member of the superfamily Stegocephaloidea. It includes the following genera and species divided under five subfamilies:
*Subfamily Andaniopsinae
Berge & Vader, 2001
:*Genus ''
Andaniopsis''
Sars, 1895
::*''
Andaniopsis africana''
Berge, Vader & Galan, 2001
::*''
Andaniopsis integripes''
(Bellan-Santini & Ledoyer, 1986)
::*''
Andaniopsis isaki''
Berge, 2004
::*''
Andaniopsis nordlandica''
(Boeck, 1871)
::*''
Andaniopsis pectinata''
(Sars, 1883)
:*Genus ''
Steleuthera''
J. L. Barnard, 1964
::*''
Steleuthera africana''
(Berge, Vader & Galan, 2001)
::*''
Steleuthera ecoprophycaea''
Bellan-Santini & Thurston, 1996
::*''
Steleuthera maremboca''
J. L. Barnard, 1964
*Subfamily Andaniexinae
Berge & Vader, 2001
:*Genus ''
Andaniexis''
Stebbing, 1906
::*''
Andaniexis abyssi''
(Boeck, 1871)
::*''
Andaniexis americana''
Berge, Vader & Galan, 2001
::*''
Andaniexis andaniexis''
Berge & Vader, 2003
::*''
Andaniexis australis''
Barnard, 1932
::*''
Andaniexis eilae Berge''
& Vader, 1997
::*''
Andaniexis elinae Berge''
& Vader, 2003
::*''
Andaniexis gloriosae''
Berge, Vader & Galan, 2001
::*''
Andaniexis gracilis''
Berge & Vader, 1997
::*''
Andaniexis lupus''
Berge & Vader, 1997
::*''
Andaniexis mimonectes''
Ruffo, 1975
::*''
Andaniexis oculata''
Birstein & Vinogradov, 1970
::*''
Andaniexis ollii''
Berge, De Broyer & Vader, 2000
::*''
Andaniexis pelagica''
Berge, Vader & Galan, 2001
::*''
Andaniexis spinescens''
(Alcock, 1894)
::*''
Andaniexis stylifer''
Birstein & M. Vinogradov, 1960
::*''
Andaniexis subabyssi''
Birstein & M. Vinogradov, 1955
:*Genus ''
Andaniotes''
Stebbing, 1897
::*''
Andaniotes abyssorum''
Stebbing, 1888
::*''
Andaniotes bagabag''
Lowry & Stoddart, 1995
::*''
Andaniotes islandica''
(Thompson, 1882)
::*''
Andaniotes karkar''
Lowry & Stoddart, 1995
::*''
Andaniotes linearis''
K. H. Barnard, 1932
::*''
Andaniotes lowryi''
Berge, 2001
::*''
Andaniotes pooh''
Berge, 2001
::*''
Andaniotes poorei''
Berge, 2001
::*''
Andaniotes pseudolinearis''
Berge, 2001
::*''
Andaniotes wallaroo''
J. L. Barnard, 1972
::*''
Andaniotes wollongong''
Berge, 2001
:*Genus ''
Glorandaniotes''
Ledoyer, 1986
::*''
Glorandaniotes eilae''
(Berge & Vader, 1997)
::*''
Glorandaniotes fissicaudata''
Ledoyer, 1986
::*''
Glorandaniotes norae''
Berge & Vader, 2003
::*''
Glorandaniotes sandroi''
Berge & Vader, 2003
::*''
Glorandaniotes spongicola''
(Pirlot, 1933)
::*''
Glorandaniotes traudlae''
Berge & Vader, 2003
::*''
Glorandaniotes vemae''
Berge & Vader, 2003
:*Genus ''
Mediterexis''
Berge & Vader, 2001
::*''
Mediterexis macho''
Berge & Vader, 2004
::*''
Mediterexis mimonectes''
(Ruffo, 1975)
:*Genus ''
Metandania''
Stephensen, 1925
::*''
Metandania islandica''
Stephensen, 1925
::*''
Metandania tordi''
Berge & Vader, 2003
::*''
Metandania wimi''
Berge, 2001
:*Genus ''
Parandaniexis''
Schellenberg, 1929
::*''
Parandaniexis dewitti''
Watling & Holman, 1980
::*''
Parandaniexis inermis''
Watling & Holman, 1980
::*''
Parandaniexis mirabilis''
Schellenberg, 1929
::*''
Parandaniexis pelagica''
(Berge, Vader & Galan, 2001)
::*''
Parandaniexis tridentata''
Ledoyer, 1986
:*Genus ''
Stegosoladidus''
Barnard & Karaman, 1987
::*''
Stegosoladidus antarcticus''
Berge, 2001
::*''
Stegosoladidus complex''
Berge, 2001
::*''
Stegosoladidus debroyeri''
Berge, 2001
::*''
Stegosoladidus ingens''
(Chevreux, 1906e)
::*''
Stegosoladidus simplex''
(K. H. Barnard, 1930)
*Subfamily Bathystegocephalinae
Berge & Vader, 2001
:*Genus ''
Bathystegocephalus''
Schellenberg, 1926
::*''
Bathystegocephalus globosus''
(Walker, 1909)
*Subfamily Parandaniinae
Berge & Vader, 2001
:*Genus ''
Parandania''
Stebbing, 1899
::*''
Parandania boecki''
(Stebbing, 1888)
::*''
Parandania gigantea''
(Stebbing, 1883)
::*''
Parandania nonhiata''
(Andres, 1985)
*Subfamily Stegocephalinae
Dana, 1855
:*Genus ''
Alania
Alania was a medieval kingdom of the Iranian Alans (proto-Ossetians) that flourished in the Northern Caucasus, roughly in the location of latter-day Circassia, Chechnya, Ingushetia, and modern North Ossetia–Alania, from its independence from th ...
''
Berge & Vader, 2001
::*''
Alania beringi''
(Berge & Vader, 2001)
::*''
Alania calypsonis''
(Berge, Vader & Galan, 2001)
::*''
Alania hancocki''
(Hurley, 1956)
:*Genus ''
Austrocephaloides''
Berge & Vader, 2001
::*''
Austrocephaloides australis''
(K. H. Barnard, 1916)
::*''
Austrocephaloides boxshalli''
(Berge, Vader & Galan, 2001)
::*''
Austrocephaloides camoti''
(J. L. Barnard, 1967)
::*''
Austrocephaloides gunnae''
(Berge & Vader, 2003)
::*''
Austrocephaloides ingstadi''
(Berge & Vader, 2003)
::*''
Austrocephaloides tori''
(Berge & Vader, 2003)
::*''
Austrocephaloides tucki''
(Berge & Vader, 2003)
:*Genus ''
Austrophippsia Berge''
& Vader, 2001
::*''
Austrophippsia unihamata''
(Berge & Vader, 2000)
:*Genus ''
Bouscephalus''
Berge & Vader, 2001
::*''
Bouscephalus mamillidacta''
(Moore, 1992)
:*Genus ''
Gordania''
Berge & Vader, 2001
::*''
Gordania minima''
(J. L. Barnard, 1961)
::*''
Gordania pajarella''
(J. L. Barnard, 1967)
:*Genus ''
Phippsia''
Stebbing, 1906
::*''
Phippsia gibbosa''
(Sars, 1882)
::*''
Phippsia roemeri''
Schellenberg, 1925
:*Genus ''
Pseudo
The prefix pseudo- (from Greek ψευδής, ''pseudes'', "false") is used to mark something that superficially appears to be (or behaves like) one thing, but is something else. Subject to context, ''pseudo'' may connote coincidence, imitation, ...
''
Berge & Vader, 2001
::*''
Pseudo bioice''
(Berge & Vader, 1997)
::*''
Pseudo pacifica''
(Bulycheva, 1952)
::*''
Pseudo pseudophippsia''
(Bellan-Santini, 1985)
::*''
Pseudo vanhoeffeni''
(Schellenberg, 1926)
::*''
Pseudo viscaina''
(J. L. Barnard, 1967)
:*Genus ''
Stegocephalexia''
Moore, 1992
::*''
Stegocephalexia''
penelope Moore, 1992
:*Genus ''
Stegocephalina''
Stephensen, 1925
::*''
Stegocephalina barnardi''
Berge & Vader, 2001
::*''
Stegocephalina beringi''
Berge & Vader, 2001
::*''
Stegocephalina biofar''
Berge & Vader, 1997
::*''
Stegocephalina boxshalli''
Berge, Vader & Galan, 2001
::*''
Stegocephalina idae''
Berge & Vader, 1997
::*''
Stegocephalina ingolfi''
Stephensen, 1925
::*''
Stegocephalina pacis''
(Bellan-Santini & Ledoyer, 1974)
::*''
Stegocephalina trymi''
Berge, 2001
::*''
Stegocephalina wagini''
( Gurjanova, 1936)
::*''
Stegocephalina wolf''
Berge & Vader, 2004
:*Genus ''
Stegocephaloides''
Sars, 1895
::*''
Stegocephaloides attingens''
Barnard, 1932
::*''
Stegocephaloides auratus''
(Sars, 1882)
::*''
Stegocephaloides australis''
K. H. Barnard, 1916
::*''
Stegocephaloides bernardi''
Berge & Vader, 1997
::*''
Stegocephaloides boxhalli''
Berge, Vader & Galan, 2001
::*''
Stegocephaloides christianiensis''
Boeck, 1871
::*''
Stegocephaloides gunnae''
Berge & Vader, 2003
::*''
Stegocephaloides ingstadi''
Berge & Vader, 2003
::*''
Stegocephaloides ledoyeri''
Berge, Vader & Galan, 2001
::*''
Stegocephaloides tori''
Berge & Vader, 2003
::*''
Stegocephaloides tucki''
Berge & Vader, 2003
::*''
Stegocephaloides wagini''
(Gurjanova, 1936)
:*Genus ''
Stegocephalus''
Krøyer, 1842
::*''
Stegocephalus abyssicola''
(Oldevig, 1959)
::*''
Stegocephalus ampulla''
(Phipps, 1774)
::*''
Stegocephalus casadiensis''
(Moore, 1992)
::*''
Stegocephalus inflatus''
Krøyer, 1842
::*''
Stegocephalus kergueleni''
(Schellenberg, 1926a)
::*''
Stegocephalus longicornis''
(Gurjanova, 1962)
::*''
Stegocephalus nipoma''
(J. L. Barnard, 1961)
::*''
Stegocephalus rostrata''
K. H. Barnard, 1932
:*Genus ''
Stegomorphia''
Berge & Vader, 2001
::*''
Stegomorphia watlingi''
(Berge, De Broyer & Vader, 2000)
:*Genus ''
Stegonomadia''
Berge & Vader, 2001
::*''
Stegonomadia biofar''
(Berge & Vader, 1997)
::*''
Stegonomadia idae''
(Berge & Vader, 1997)
::*''
Stegonomadia katalia''
(J. L. Barnard, 1962)
:*Genus ''
Tetradeion''
Stebbing, 1899
::*''
Tetradeion angustipalma''
(Berge & Vader, 2000)
::*''
Tetradeion crassum''
(Chilton, 1883)
::*''
Tetradeion dampieri''
(Berge & Vader, 2000)
::*''
Tetradeion latus''
(Haswell, 1879)
::*''
Tetradeion quatro''
Berge & Vader, 2000
*Subfamily ''
incertae sedis
' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...
''
:*Genus ''
Glorandantiotes''
::*''
Glorandantiotes fissicaudata''
Ledoyer, 1986
References
{{Taxonbar, from=Q3933174
Gammaridea
Crustacean families