ability of all species in this group is low and less than
0.03.
Concerning the distance between the two rows of
setules, the interspecific difference is most prominent
between the two related Streptocephalus: S. torvicornis
(0.32) (Fig. 3a) and S. rubricaudatus (0.52) (Fig. 3b)
(Hartland-Rowe, 1968; Mertens et al., 1989). There
are two genera where a median line of small spiny
hairs divides the interrow distance. In Chirocephalus
many hairs form a line (Fig. 3d). In Tanymastigites, it is
the scarcity of hairs which is characteristic (Fig. 3f).
The diameter of the setules at their base differs
strikingly between S. torvicornis and S. rubricaudatus: 0.08 versus 0.20. Only Tanymastigites (Fig. 3f)
and Branchinella (Fig. 3e) have small, almost circular
bases. The base of the setules of the other species is
elongated towards the center.
The setules are smooth, except in Chirocephalus
(Fig. 3d) where one, sometimes more denticles rise on
the inner side, and in S. rubricaudatus (Fig. 3b) where
the setules are armed on the inner side with four to five
spiny tubercles.
Discnssion
The data of the endo- and exopodite analysis presented in this paper are based on observations on
one parthenogenetic female in Artemia, one male of
Tanymastigites, Branchipus, Branchinella and Chirocephalus and several males in S. torvicornis and
S. rubricaudatus. The species-specific setation pattern
of the limbs is, however, striking and the methodology
looks extremely promising. Nevertheless, an evaluation of variability between populations, age classes
and sexes remains necessary. The data in Table 2 are
indicative, and need more detailed quantitative analysis.
So far we did not observe differences between
males and females in setal structure of endite I, based
on S.E.M. photographs of at least one male and female
in all species treated here (the Artemia used was a
parthenogenetica form). This holds also for the exoand endopodites of Branchinella and Chirocephalus,
but more work on this will certainly be useful.
201
Acknowledgments
We thank Mrs H. De Paepe for the preparation of the
graphs, and Mr H. Segers for assistance with the scanning electron microscopy.
References
Dumont, H., 1. Mertens & A. Maeda-Martinez, 1995. Historical biogeography and morphological differentiation of Streptocephaius
torvicornis (Waga) since the Wiirm III-glaciation. Hydrobiologia
298 (Dev. Hydrobiol. 103): 281-286.
Hartland-Rowe, R., 1968. On the identity of Streptocephaius rubricaudatus (Klunzinger, 1867) (Anostraca). Crustaceana 15: 319321.
Linder, F., 1941. Contribution to the morphology and taxonomy of
the branchiopoda Anostraca. Zool. Bidr. Uppsala 20: 101-302.
Mertens, 1. & H. Dumont, 1989. Confirmation of Streptocephaius
rubricaudatus as a good species (Anostraca). Crustaceana 56:
211-212.
Mertens, 1., N. Munuswamy, C. De Walsche & H. J. Dumont, 1991.
The filtration apparatus of Anostraca (Crustacea): species- specific setulation in the genus Streptocephaius. Hydrobiologia 212:
187-193.
Watling, L., 1989. A classification system for crustacean setae based
on the homology concept. in: Crustacean issues 6: Functional
morphology of feeding and grooming in Crustacea - pp. 15-26.
Ed. Schram F. R.- Balkema, Rotterdam, Brookfield.
0.03.
Concerning the distance between the two rows of
setules, the interspecific difference is most prominent
between the two related Streptocephalus: S. torvicornis
(0.32) (Fig. 3a) and S. rubricaudatus (0.52) (Fig. 3b)
(Hartland-Rowe, 1968; Mertens et al., 1989). There
are two genera where a median line of small spiny
hairs divides the interrow distance. In Chirocephalus
many hairs form a line (Fig. 3d). In Tanymastigites, it is
the scarcity of hairs which is characteristic (Fig. 3f).
The diameter of the setules at their base differs
strikingly between S. torvicornis and S. rubricaudatus: 0.08 versus 0.20. Only Tanymastigites (Fig. 3f)
and Branchinella (Fig. 3e) have small, almost circular
bases. The base of the setules of the other species is
elongated towards the center.
The setules are smooth, except in Chirocephalus
(Fig. 3d) where one, sometimes more denticles rise on
the inner side, and in S. rubricaudatus (Fig. 3b) where
the setules are armed on the inner side with four to five
spiny tubercles.
Discnssion
The data of the endo- and exopodite analysis presented in this paper are based on observations on
one parthenogenetic female in Artemia, one male of
Tanymastigites, Branchipus, Branchinella and Chirocephalus and several males in S. torvicornis and
S. rubricaudatus. The species-specific setation pattern
of the limbs is, however, striking and the methodology
looks extremely promising. Nevertheless, an evaluation of variability between populations, age classes
and sexes remains necessary. The data in Table 2 are
indicative, and need more detailed quantitative analysis.
So far we did not observe differences between
males and females in setal structure of endite I, based
on S.E.M. photographs of at least one male and female
in all species treated here (the Artemia used was a
parthenogenetica form). This holds also for the exoand endopodites of Branchinella and Chirocephalus,
but more work on this will certainly be useful.
201
Acknowledgments
We thank Mrs H. De Paepe for the preparation of the
graphs, and Mr H. Segers for assistance with the scanning electron microscopy.
References
Dumont, H., 1. Mertens & A. Maeda-Martinez, 1995. Historical biogeography and morphological differentiation of Streptocephaius
torvicornis (Waga) since the Wiirm III-glaciation. Hydrobiologia
298 (Dev. Hydrobiol. 103): 281-286.
Hartland-Rowe, R., 1968. On the identity of Streptocephaius rubricaudatus (Klunzinger, 1867) (Anostraca). Crustaceana 15: 319321.
Linder, F., 1941. Contribution to the morphology and taxonomy of
the branchiopoda Anostraca. Zool. Bidr. Uppsala 20: 101-302.
Mertens, 1. & H. Dumont, 1989. Confirmation of Streptocephaius
rubricaudatus as a good species (Anostraca). Crustaceana 56:
211-212.
Mertens, 1., N. Munuswamy, C. De Walsche & H. J. Dumont, 1991.
The filtration apparatus of Anostraca (Crustacea): species- specific setulation in the genus Streptocephaius. Hydrobiologia 212:
187-193.
Watling, L., 1989. A classification system for crustacean setae based
on the homology concept. in: Crustacean issues 6: Functional
morphology of feeding and grooming in Crustacea - pp. 15-26.
Ed. Schram F. R.- Balkema, Rotterdam, Brookfield.