3.7 Acartia tonsa Dana 1849
Acartia tonsa Dana, 1849: p. 26 - Giesbrecht,
1892: p. 508, pI. 30 figs. 7, 24, 34, pI. 43 figs.
6, 10 - Wilson, 1932: p. 160, fig. 109 -
Brodskii, 1950: p. 426, fig. 302 - Gonzalez
and Bowman, 1965: p. 257, fig. llc-f -
Ramirez, 1966: p. 19, figs. 8-14 - Vidal,
1968: p. 46, pI. 17 figs. 12-14, pI. 18 fig. 8Ramirez, 1969: p. 84, pI. 16 fig. 135 - Arcos,
1975: p. 23, pI. 9 figs. 71-74-Sabatini, 1990:
p. 53, figs. 37-48.
Acartia (Acanthacartia) tonsa Steuer, 1915:
p.396.
Acartia tonsa var. cryophylla Bjornberg,
1963: p. 64, fig. 34.
Body length -
females: 1.10-1.27 mm (30 specimens)
males: 0.98-1.12mm (20 specimens)
Female. Body slender. Cephalothorax 3.4
times longer than wide; rounded posterior
corners of last thoracic somite ornated with
short spinules. Proportional lengths of
cephalothorax
and
abdomen
80: 20.
Abdomen 3-segmented; proportional lengths
of abdominal so mites and furca 46: 16: 18: 20
= 100. Genital somite with rows of small
spinules on both dorsal and ventral sides.
Dorsal posterior margins of abdominal
somites naked. P5 basal joint with round
process on inner distal margin. Distal joint
consisting in strong, characteristic basally
swollen spine, serrated at beginning of distal
half and ornated with small scales on thin
distal end. Basal joint with long, feathered
seta on outer margin, longer than terminal
spine.
Family Acartiidae
Male. Same body shape as female. Right
Al geniculated. Proportional lengths of
cephalothorax and abdomen 78 : 22. Posterior
comers of last thoracic somite ornated with
few spinules. Abdomen 5-segmented.
Proportional lengths of abdominal somites
and furca 16: 29: 18: 8: 14: 15 = 100. Hairs
and small spines on dorsal margin of first
somite. Spinules sparsely distributed on
dorsal surface and posterior margin of second
abdominal somite. Caudal rami ornated with
spinules of different size on dorsal surface.
P5 uniramous, asymmetrical, with median Bl
common to both right and left joints. Right
ramus 4-jointed and left ramus 3-jointed. In
right leg, penultimate joint with wide process
on inner margin; last joint swollen in the
middle, strongly turned inwards and with a
hook-like apex. Last joint of left leg bearing
spine and a characteristic lamellar projection resembling the head of a bird, with
numerous, very small spinules on surface. At
basis of this projection, cluster of long hairs
and row of bristles.
Remarks
Both females and males of this species are
highly variable in the ornamentation of the
abdominal somites. This variability may
reflect biogeographic differences. Our
specimens closely resemble those described
by Bjornberg (1963) as A. tonsa var. cryophylla due to the remarkably reduced
ornamentation of the abdominal somites
compared to the typical A. tonsa.
Acartia tonsa Dana, 1849: p. 26 - Giesbrecht,
1892: p. 508, pI. 30 figs. 7, 24, 34, pI. 43 figs.
6, 10 - Wilson, 1932: p. 160, fig. 109 -
Brodskii, 1950: p. 426, fig. 302 - Gonzalez
and Bowman, 1965: p. 257, fig. llc-f -
Ramirez, 1966: p. 19, figs. 8-14 - Vidal,
1968: p. 46, pI. 17 figs. 12-14, pI. 18 fig. 8Ramirez, 1969: p. 84, pI. 16 fig. 135 - Arcos,
1975: p. 23, pI. 9 figs. 71-74-Sabatini, 1990:
p. 53, figs. 37-48.
Acartia (Acanthacartia) tonsa Steuer, 1915:
p.396.
Acartia tonsa var. cryophylla Bjornberg,
1963: p. 64, fig. 34.
Body length -
females: 1.10-1.27 mm (30 specimens)
males: 0.98-1.12mm (20 specimens)
Female. Body slender. Cephalothorax 3.4
times longer than wide; rounded posterior
corners of last thoracic somite ornated with
short spinules. Proportional lengths of
cephalothorax
and
abdomen
80: 20.
Abdomen 3-segmented; proportional lengths
of abdominal so mites and furca 46: 16: 18: 20
= 100. Genital somite with rows of small
spinules on both dorsal and ventral sides.
Dorsal posterior margins of abdominal
somites naked. P5 basal joint with round
process on inner distal margin. Distal joint
consisting in strong, characteristic basally
swollen spine, serrated at beginning of distal
half and ornated with small scales on thin
distal end. Basal joint with long, feathered
seta on outer margin, longer than terminal
spine.
Family Acartiidae
Male. Same body shape as female. Right
Al geniculated. Proportional lengths of
cephalothorax and abdomen 78 : 22. Posterior
comers of last thoracic somite ornated with
few spinules. Abdomen 5-segmented.
Proportional lengths of abdominal somites
and furca 16: 29: 18: 8: 14: 15 = 100. Hairs
and small spines on dorsal margin of first
somite. Spinules sparsely distributed on
dorsal surface and posterior margin of second
abdominal somite. Caudal rami ornated with
spinules of different size on dorsal surface.
P5 uniramous, asymmetrical, with median Bl
common to both right and left joints. Right
ramus 4-jointed and left ramus 3-jointed. In
right leg, penultimate joint with wide process
on inner margin; last joint swollen in the
middle, strongly turned inwards and with a
hook-like apex. Last joint of left leg bearing
spine and a characteristic lamellar projection resembling the head of a bird, with
numerous, very small spinules on surface. At
basis of this projection, cluster of long hairs
and row of bristles.
Remarks
Both females and males of this species are
highly variable in the ornamentation of the
abdominal somites. This variability may
reflect biogeographic differences. Our
specimens closely resemble those described
by Bjornberg (1963) as A. tonsa var. cryophylla due to the remarkably reduced
ornamentation of the abdominal somites
compared to the typical A. tonsa.