Hydrobiologia 298: 203-232, 1995.
D. Belk, H. J. Dumont & G. Maier (eds), Studies on Large Branchiopod Biology and Aquaculture II.
© 1995 Kluwer Academic Publishers.
203
A contribution to the systematics of the Streptocephalidae
(Branchiopoda: Anostraca)
Alejandro M. Maeda-Martinez 1 ,3, Denton Belk 2 , Hortencia Obregon-Barboza 1 ,3 &
Henri J. Dumont 1
1 Laboratory of Animal Ecology, University of Ghent, K. L. Ledeganckstraat 35, B-9000 Ghent, Belgium
2 Biology Department, Our Lady of the Lake University of San Antonio, TX 78207-4666, USA
3 Current address: Centro de Investigaciones Biologicas del Noroeste, S.c., Division Biolog(a Marina, Apdo.
Postal 128, La Paz, Baja California Sur, Mexico
Key words: Streptocephalus, morphology, classification, phylogeny, fairy shrimp, phyllopod
Abstract
While developing a data base for phylogenetic analysis of the New World streptocephalids we compared them
with species from Africa, Europe, and India. In doing this, we found that the morphology of the peduncle of the
distal antennal outgrowth and the biramous ovaries developed in seven North American species can contribute to
the systematics of the genus. Thus, our investigation consisted of (1) a review of the external morphology of the
antenna, (2) biometry of selected parts of the antenna to obtain informative ratios, (3) a review of the presence or
absence of genital linguiform outgrowths, extension of the non-retractile parts of the penes, and general morphology
of the cercopods, (4) a study of the location of the ovaries, and extension of the brood-pouch. On the basis of thb
results we classify Streptocephalus into nine species groups. Five subgroups are identified within two of the species
groups. Several implications of the present approach are discussed.
Introduction
The family Streptocephalidae Daday, 1910 is composed of a single genus, Streptocephalus Baird, 1852.
It is the most species-rich genus within the order Anostraca. More than sixty nominal species have been
described from Africa, the Arabian peninsula, India,
Indonesia, and North America. Fifty-eight of these are
considered as valid (Belk & Brtek, 1995; this volume).
The classification of the Streptocephalus species
into different groups started in the last century when
Verrill (1869) pointed out that S. torvicornis (Waga)
and S. rubricaudatus (Klunzinger) seemed closely
related, and that they should be considered as typical of
the genus, while S. cafer (Loven) and S. similis Baird
should be separated in the subgenus Heterobranchipus. Daday (191Oa) was the first worker to formally split Streptocephalus into 3 subgenera. He considered the morphology of the frontal appendage as the
key criterion of such a subdivision: subgenus Streptocephalellus with no frontal appendage, subgenus Streptocephalus with frontal appendage simple or notched at
its tip, and subgenus Streptocephalopsis with branched
frontal appendage. Each of these subgenera, however,
grouped species having a very different antennal morphology, e.g., S. purcelli Sars, and S. papillatus Sars in
Streptocephalellus, S. lamelliferThiele, and S. dichotomus Baird in Streptocephalus s. str., and S. rothschildi
Daday and S. cafer in Streptocephalopsis.
Daday's subgeneric classification was followed by
Barnard (1924), assigning S. ovamboensis Barnard,
and S. indistinctus Barnard to the subgenus Streptocephalus, and S. cladophorus Barnard to the subgenus
Streptocephalopsis. Yet, Barnard was also the first
author to reject the subgeneric system of Daday. He
indicated that the boundary between two of the subgenera was not well delimited, and that a number of species
presented every gradation between the two extreme
forms (Barnard, 1929). Similarly, Creaser (1930) mentioned that the North American species, S. similis, S.
sealii Ryder, and S. texan us Packard belong to the subgenus Streptocephalus. At the same time he pointed
out that the limits of the subgenus Streptocephalopsis
were not well defined, while the structure of the male
cercopods could offer a convenient method to group
D. Belk, H. J. Dumont & G. Maier (eds), Studies on Large Branchiopod Biology and Aquaculture II.
© 1995 Kluwer Academic Publishers.
203
A contribution to the systematics of the Streptocephalidae
(Branchiopoda: Anostraca)
Alejandro M. Maeda-Martinez 1 ,3, Denton Belk 2 , Hortencia Obregon-Barboza 1 ,3 &
Henri J. Dumont 1
1 Laboratory of Animal Ecology, University of Ghent, K. L. Ledeganckstraat 35, B-9000 Ghent, Belgium
2 Biology Department, Our Lady of the Lake University of San Antonio, TX 78207-4666, USA
3 Current address: Centro de Investigaciones Biologicas del Noroeste, S.c., Division Biolog(a Marina, Apdo.
Postal 128, La Paz, Baja California Sur, Mexico
Key words: Streptocephalus, morphology, classification, phylogeny, fairy shrimp, phyllopod
Abstract
While developing a data base for phylogenetic analysis of the New World streptocephalids we compared them
with species from Africa, Europe, and India. In doing this, we found that the morphology of the peduncle of the
distal antennal outgrowth and the biramous ovaries developed in seven North American species can contribute to
the systematics of the genus. Thus, our investigation consisted of (1) a review of the external morphology of the
antenna, (2) biometry of selected parts of the antenna to obtain informative ratios, (3) a review of the presence or
absence of genital linguiform outgrowths, extension of the non-retractile parts of the penes, and general morphology
of the cercopods, (4) a study of the location of the ovaries, and extension of the brood-pouch. On the basis of thb
results we classify Streptocephalus into nine species groups. Five subgroups are identified within two of the species
groups. Several implications of the present approach are discussed.
Introduction
The family Streptocephalidae Daday, 1910 is composed of a single genus, Streptocephalus Baird, 1852.
It is the most species-rich genus within the order Anostraca. More than sixty nominal species have been
described from Africa, the Arabian peninsula, India,
Indonesia, and North America. Fifty-eight of these are
considered as valid (Belk & Brtek, 1995; this volume).
The classification of the Streptocephalus species
into different groups started in the last century when
Verrill (1869) pointed out that S. torvicornis (Waga)
and S. rubricaudatus (Klunzinger) seemed closely
related, and that they should be considered as typical of
the genus, while S. cafer (Loven) and S. similis Baird
should be separated in the subgenus Heterobranchipus. Daday (191Oa) was the first worker to formally split Streptocephalus into 3 subgenera. He considered the morphology of the frontal appendage as the
key criterion of such a subdivision: subgenus Streptocephalellus with no frontal appendage, subgenus Streptocephalus with frontal appendage simple or notched at
its tip, and subgenus Streptocephalopsis with branched
frontal appendage. Each of these subgenera, however,
grouped species having a very different antennal morphology, e.g., S. purcelli Sars, and S. papillatus Sars in
Streptocephalellus, S. lamelliferThiele, and S. dichotomus Baird in Streptocephalus s. str., and S. rothschildi
Daday and S. cafer in Streptocephalopsis.
Daday's subgeneric classification was followed by
Barnard (1924), assigning S. ovamboensis Barnard,
and S. indistinctus Barnard to the subgenus Streptocephalus, and S. cladophorus Barnard to the subgenus
Streptocephalopsis. Yet, Barnard was also the first
author to reject the subgeneric system of Daday. He
indicated that the boundary between two of the subgenera was not well delimited, and that a number of species
presented every gradation between the two extreme
forms (Barnard, 1929). Similarly, Creaser (1930) mentioned that the North American species, S. similis, S.
sealii Ryder, and S. texan us Packard belong to the subgenus Streptocephalus. At the same time he pointed
out that the limits of the subgenus Streptocephalopsis
were not well defined, while the structure of the male
cercopods could offer a convenient method to group