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5.2 Pseudomma magellanensis
Tattersall, 1955
Pseudomma magellanensis Tattersall, 1955: pp.
100, 101 - Mauchline and Murano, 1977: p. 74
(world catalogue) - Miiller, 1993: p. 137 (world
catalogue)
Body length -
female: 8.8 mm {1 specimen)
male: 8.4 mm ( 1 specimen)
Female. Carapace with short anterior margin;
slightly convex and uncovering the high plate.
3rd segment of antennule longer than wide and
equal in length to ca. sum of the first 2 segments.
Dorsal surface at base of2 flagellae bearing rectangular tubercle with robust spine on anterior
outer margin. Inner margin bearing 2 very small
spines and 2 slender setules. Antennal scale
small, 3 times longer than wide, surpassing distai margin of antennular peduncle by 1/3. Unarmed outer margin terminating with wide
tooth. Apex of scale slightly surpassing tooth
margin. Wide ocular plate, typical of the genus,
projecting forward to reach proximal limit of
2nd segment of antennular peduncle; not entirely convex but bearing marked bulges along median line of 2 halves. Rudimentary eyes appear
contiguous. Lateral margins of plate armed with
9 irregular teeth extending along lateral margins
by 3/4, beginning from antero-lateral corners.
Uropod with small pointed endopod extending
beyond telson by 1/2. Exopod wider and much
longer, reaching beyond distal margin of endopod by about 1/4. Telson short and with concave
lateral margins, armed with 8 spines at distal2/3
of margin; these progressively increase in size
distally. Apex wide and convex, armed with 3
long slender spines that become progressively
Subfamily Mysinae
Tribe Erythropini
longer towards median line. Here, a pair of plumose setules are inserted on a small papilla.
Male. Ventral side of distal margin of antennular
peduncle bearing typicallobe with thick tuft of
long setules. 4th pleopod with 8-segmented exopod, longer than endopod. Endopod 7-segmented. All pleopods bearing long and slender simpodites and thread-like rami.
Remarks
P. magellanensis is similar to the congener P. sarsi but can be distinguished by its smaller size and
sunken ocular plate with 2 well-defined dorsal
crests separated by a shallow depression (Tattersall 1955). Also, the species has smaller amorphous teeth along the lateral margins of the
ocular plate, the 4th pleopod of the males differs,
and the telson has a characteristic apex with
concave lateral margins. Differences have been
observed in the number of setules on the rectangular tubercle at the base of the 2 antennular flagella. Males have only 2 setules, whereas females
possess 4. This is probably due to the great individual variability observed in species of the genus Pseudomma, as already noted by O.S.
Tattersall {1955) while studying the material
from the Discovery collection.
Distribution
To date, this species had been reported only by
Tattersall {1955), who recorded a single female
and male specimen in night samples collected
from 0-300 m in the Straits of Magellan. Tattersall assigned the specimens to a new species. In
the present study, the only 2 specimens were
sampled from 0-100 mat St. 19 in the Central
are a of the Straits.
5.2 Pseudomma magellanensis
Tattersall, 1955
Pseudomma magellanensis Tattersall, 1955: pp.
100, 101 - Mauchline and Murano, 1977: p. 74
(world catalogue) - Miiller, 1993: p. 137 (world
catalogue)
Body length -
female: 8.8 mm {1 specimen)
male: 8.4 mm ( 1 specimen)
Female. Carapace with short anterior margin;
slightly convex and uncovering the high plate.
3rd segment of antennule longer than wide and
equal in length to ca. sum of the first 2 segments.
Dorsal surface at base of2 flagellae bearing rectangular tubercle with robust spine on anterior
outer margin. Inner margin bearing 2 very small
spines and 2 slender setules. Antennal scale
small, 3 times longer than wide, surpassing distai margin of antennular peduncle by 1/3. Unarmed outer margin terminating with wide
tooth. Apex of scale slightly surpassing tooth
margin. Wide ocular plate, typical of the genus,
projecting forward to reach proximal limit of
2nd segment of antennular peduncle; not entirely convex but bearing marked bulges along median line of 2 halves. Rudimentary eyes appear
contiguous. Lateral margins of plate armed with
9 irregular teeth extending along lateral margins
by 3/4, beginning from antero-lateral corners.
Uropod with small pointed endopod extending
beyond telson by 1/2. Exopod wider and much
longer, reaching beyond distal margin of endopod by about 1/4. Telson short and with concave
lateral margins, armed with 8 spines at distal2/3
of margin; these progressively increase in size
distally. Apex wide and convex, armed with 3
long slender spines that become progressively
Subfamily Mysinae
Tribe Erythropini
longer towards median line. Here, a pair of plumose setules are inserted on a small papilla.
Male. Ventral side of distal margin of antennular
peduncle bearing typicallobe with thick tuft of
long setules. 4th pleopod with 8-segmented exopod, longer than endopod. Endopod 7-segmented. All pleopods bearing long and slender simpodites and thread-like rami.
Remarks
P. magellanensis is similar to the congener P. sarsi but can be distinguished by its smaller size and
sunken ocular plate with 2 well-defined dorsal
crests separated by a shallow depression (Tattersall 1955). Also, the species has smaller amorphous teeth along the lateral margins of the
ocular plate, the 4th pleopod of the males differs,
and the telson has a characteristic apex with
concave lateral margins. Differences have been
observed in the number of setules on the rectangular tubercle at the base of the 2 antennular flagella. Males have only 2 setules, whereas females
possess 4. This is probably due to the great individual variability observed in species of the genus Pseudomma, as already noted by O.S.
Tattersall {1955) while studying the material
from the Discovery collection.
Distribution
To date, this species had been reported only by
Tattersall {1955), who recorded a single female
and male specimen in night samples collected
from 0-300 m in the Straits of Magellan. Tattersall assigned the specimens to a new species. In
the present study, the only 2 specimens were
sampled from 0-100 mat St. 19 in the Central
are a of the Straits.