5.3 Arthromysis magellanica
Cunningham, 1871
Macromysis magellanica Cunningham, 1871: p.
497.
Antarctomysis sp. Coutiere, 1906: pp. 1-1 O, 2 pls.
Arthromysis chierchiae Colosi, 1924: pp. 3-5,
figs. 1-3.
Arthromysis magellanica Tattersall, 1955: pp.
179-181, figs. 45, 46 - Mauchline and Murano,
1977: p. 48 (world catalogue) - Miiller, 1993: p.
212 (world catalogue).
Body length -
immature females: 12.0-13.5 mm
( 8 specimens)
Immature female. Posterior margin of carapace
short, uncovering the 8th, 7th and part of the 6th
thoracic somites. Anterior portion with rounded, semicircular frontal plate. Antero-lateral corners of carapace spine-like. Eyes with elongated,
slender and cylindrical peduncle, with hemispherical cornea. Eyes longer than distal extremity of 2nd segment of antennular peduncle.
Antennules bearing elongated peduncle. 3rd segment almost as long as 2nd, with expanded distal
extremity. A small nodule is evident at base of
flagellae, bearing 4 slender setules and spiniform process. Antenna with long and slender
scale, twice the length of antennular peduncle;
antenna bearing setae on both sides and with
distal suture. Pleon with 6th segment twice as
long as 5th. Uropod with long and slender exopod, twice as long as telson. Endopod shorter
and about 2/3 as long as exopod; densely covered
with setae and bearing series of 13 spines on inner side, in submarginal position, below statocysts. Telson 3 times longer than wide. Margins
Tribe Mysini
of telson bearing series of 24-25 regularly distributed spines. Terminal spines closely apposed
to shorter apical spines, giving rise to spinulation on telson cleft. There are about 45 of these
short spines on each side. 2 long and plumose
setules initiate from inner side of cleft and extend beyond distal end by twice their length.
Remarks
This species, referred to as Arthromysis chierchiae by Colosi (1924), who erected the genus,
posed several systematic problems until Tattersall (1955) examined a sufficient number of
specimens to attribute them to A. magellanica.
The species is characterized by two long and plumose setules arising from the base of telson cleft.
Even though the species can be easily confused
with Tenagomysis tenuipes, it can be distinguished by its elongated, slender eyes and semicircular form of the anterior margin of the
carapace (Tattersall1955).
Distribution
This species was first reported by Cunningham
(1871) at the eastern end ofthe Straits ofMagellan. It was later also reported in the Straits by
Zimmer (1915). Colosi (1924) found a single female specimen at Cape Virgin (Straits of Magellan), whereas Tattersall (1955) recorded numerous adult specimens in the area comprised
between the Falkland Islands and Tierra del Fuego, ata depth of 21-23 m. Tattersall (op. cit.)
also sampled it in the Straits at a depth of 040 m. In the present study, A. magellanica was
sampled only from 10-30 mat St. 26, in Atlantic
waters beyond the Straits.
Cunningham, 1871
Macromysis magellanica Cunningham, 1871: p.
497.
Antarctomysis sp. Coutiere, 1906: pp. 1-1 O, 2 pls.
Arthromysis chierchiae Colosi, 1924: pp. 3-5,
figs. 1-3.
Arthromysis magellanica Tattersall, 1955: pp.
179-181, figs. 45, 46 - Mauchline and Murano,
1977: p. 48 (world catalogue) - Miiller, 1993: p.
212 (world catalogue).
Body length -
immature females: 12.0-13.5 mm
( 8 specimens)
Immature female. Posterior margin of carapace
short, uncovering the 8th, 7th and part of the 6th
thoracic somites. Anterior portion with rounded, semicircular frontal plate. Antero-lateral corners of carapace spine-like. Eyes with elongated,
slender and cylindrical peduncle, with hemispherical cornea. Eyes longer than distal extremity of 2nd segment of antennular peduncle.
Antennules bearing elongated peduncle. 3rd segment almost as long as 2nd, with expanded distal
extremity. A small nodule is evident at base of
flagellae, bearing 4 slender setules and spiniform process. Antenna with long and slender
scale, twice the length of antennular peduncle;
antenna bearing setae on both sides and with
distal suture. Pleon with 6th segment twice as
long as 5th. Uropod with long and slender exopod, twice as long as telson. Endopod shorter
and about 2/3 as long as exopod; densely covered
with setae and bearing series of 13 spines on inner side, in submarginal position, below statocysts. Telson 3 times longer than wide. Margins
Tribe Mysini
of telson bearing series of 24-25 regularly distributed spines. Terminal spines closely apposed
to shorter apical spines, giving rise to spinulation on telson cleft. There are about 45 of these
short spines on each side. 2 long and plumose
setules initiate from inner side of cleft and extend beyond distal end by twice their length.
Remarks
This species, referred to as Arthromysis chierchiae by Colosi (1924), who erected the genus,
posed several systematic problems until Tattersall (1955) examined a sufficient number of
specimens to attribute them to A. magellanica.
The species is characterized by two long and plumose setules arising from the base of telson cleft.
Even though the species can be easily confused
with Tenagomysis tenuipes, it can be distinguished by its elongated, slender eyes and semicircular form of the anterior margin of the
carapace (Tattersall1955).
Distribution
This species was first reported by Cunningham
(1871) at the eastern end ofthe Straits ofMagellan. It was later also reported in the Straits by
Zimmer (1915). Colosi (1924) found a single female specimen at Cape Virgin (Straits of Magellan), whereas Tattersall (1955) recorded numerous adult specimens in the area comprised
between the Falkland Islands and Tierra del Fuego, ata depth of 21-23 m. Tattersall (op. cit.)
also sampled it in the Straits at a depth of 040 m. In the present study, A. magellanica was
sampled only from 10-30 mat St. 26, in Atlantic
waters beyond the Straits.