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Parthenogenesis in scorpions: Some history - New data


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Parthenogenesis, a rare phenomenon in Chelicerates, apart from mites, is reviewed in scorpions, notably Tityus serrulatus Lutz & Mello from Brazil, Tityus columbianus (Thorell) from Colombia and Tityus metuendus Pocock from Peru and Brazil. Thelytokous parthenogenesis (with all-female broods) is most often observed. The only known exception to this is T. metuendus in which arrhenotoky (all-male broods) has been observed. In the present paper, current ideas regarding parthenogenesis in scorpions are summarized. The notion of geographic parthenogenesis (‘parthénogenèse géographique’), coined by Vandel in 1928, is discussed. This rule is tentatively exemplified by a new case of parthenogenesis reported in a scorpion of the genus Tityus C. L. Koch, inhabiting ‘Pico da Neblina’ in Brazil / Venezuela
Content may be subject to copyright.
Received: August 27, 2007
Accepted: August 27, 2007
Abstract published online: September 12, 2007
Full paper published online: March 8, 2008
J. Venom. Anim. Toxins incl. Trop. Dis.
V.14, n.1, p.19-44, 2008.
Review article.
ISSN 1678-9199.
(1) National Museum of Natural History, Department of Systematics and Evolution,
Arthropods, Arachnology Section, Paris, France.
ABSTRACT: Parthenogenesis, a rare phenomenon in Chelicerates, apart from
mites, is reviewed in scorpions, notably Tityus serrulatus Lutz & Mello from Brazil,
Tityus columbianus (Thorell) from Colombia and Tityus metuendus Pocock from Peru
and Brazil. Thelytokous parthenogenesis (with all-female broods) is most often
observed. The only known exception to this is T. metuendus in which arrhenotoky
(all-male broods) has been observed. In the present paper, current ideas regarding
parthenogenesis in scorpions are summarized. The notion of geographic
parthenogenesis (‘parthénogenèse géographique’), coined by Vandel in 1928, is
discussed. This rule is tentatively exemplified by a new case of parthenogenesis
reported in a scorpion of the genus Tityus C. L. Koch, inhabiting ‘Pico da Neblina’ in
Brazil / Venezuela.
KEY WORDS: scorpions, geographic parthenogenesis, review, thelytoky,
arrhenotoky, deutherotoky.
CONFLICTS OF INTEREST: Conference presented in the Symposium
“Reproductive Biology of Scorpions” during the 17
International Congress of
Arachnology, August 5–10, 2007, São Pedro, São Paulo State, Brazil.
WILSON R. LOURENÇO, Muséum National d’Histoire Naturelle, Département de
Systématique et Evolution, USM 0602, Section Arthropodes (Arachnologie), CP 053,
57 rue Cuvier 75005 Paris, France: Email:
Toxins incl. Trop. Dis., 2008, 14, 1, p.
Parthenogenesis (from the Greek παρθενος parthenos = ‘virgin’ + γενεσις genesis =
‘birth’) is a form of reproduction in which the ovum develops without fertilization. With
the exception of mites, this phenomenon is rare among Chelicerates (42-44, 49). It
has, however, been observed in a few species of harvestmen, spiders and scorpions
(4, 9, 10, 14, 24, 53). Of nearly 1600 species of scorpions distributed throughout the
world, pathenogenesis was demonstrated or suggested for only eleven (26, 32). The
first of these was reported by Matthiesen (34) of the São Paulo State University
(UNESP, Rio Claro), in the Brazilian species Tityus serrulatus Lutz & Mello, 1922
(Figures 1 and 2). The other known or suggested parthenogenetic species are Tityus
uruguayensis Borelli, 1901 from Uruguay and Brazil, Tityus columbianus (Thorell,
1876) from Colombia, Tityus trivittatus Kraepelin, 1898 from Argentina, Brazil and
Paraguay, Tityus stigmurus (Thorell, 1876) from Brazil, Tityus metuendus Pocock,
1897 from Peru and Brazil, Ananteris coineaui Lourenço, 1982 from French Guyana,
Centruroides gracilis (Latreille, 1804) from Cuba, Hottentotta hottentotta (Fabricius,
1787) from West Africa, Hottentotta caboverdensis Lourenço and Ythier, 2006 from
the Cape Verde Islands, and Liocheles australasiae (Fabricius, 1775) from the South
Pacific (32, 51, 52, 62) (see Figures 3 to 13). It is obvious, however, that for some of
these species further investigations are yet necessary to clearly confirm
parthenogenetic reproduction. Thelytokous parthenogenesis (with all-female broods)
is the general trend observed among scorpions (24). The only known exception is T.
metuendus in which arrhenotoky (all-male broods) has been observed (28).
In the present review, ideas about parthenogenesis in scorpions are summarized.
The notion of geographic parthenogenesis (or ‘parthénogenèse géographique’) as
coined by Vandel in 1928 (54) is discussed.
As already pointed out by Lourenço and Cuellar (27), approximately 95% of all living
species reproduce sexually. The origin of sexual reproduction is not clear, however,
and it has probably evolved independently among living organisms several times.
Since sexual reproduction allows genetic recombination, it should also permit the
rapid incorporation of favorable mutations. Muller (41) was the first to propose that
sex accelerates evolution because two favorable mutations (A and B) are more likely
to arise in different individuals of the same population than in a single individual. In
Toxins incl. Trop. Dis., 2008, 14, 1, p.
asexual species, AB can only arise when two similar mutations occur simultaneously
in the same individual (37, 61).
A somewhat similar hypothesis, attempting to explain the advantages of sexual
reproduction, was formulated by Van Valen (55). The environment of any given
species is comprised of two major factors, abiotic and biotic. Abiotic factors consist of
physical factors such as climate, whereas the biotic constitute plants and animal
species in the environment, particularly closely related forms competing with each
other for limited resources such as food. Among such species, any evolutionary
modifications adapting one to the environment may be detrimental to the other, but
their evolution does not influence the abiotic factors. Therefore, each of the
competing species must evolve constantly and rapidly in response to the
modifications of the other. Otherwise, the least adaptable species will ultimately be
eliminated by the selective forces of competition. This is what Van Valen (55) called
‘the Red Queen effect’, in an analogy from Lewis Carol’s book, of ‘Alice in
Wonderland’, in which the Red Queen said to Alice, “Here you see, it takes all the
running you can do to keep in the same place.” In environments such as rain forests
therefore, where competition is extremely intense, sexual reproduction is not merely
advantageous, but a necessity.
The Red Queen hypothesis, however, does not seem to accord with the geographic
distribution of parthenogenetic animals, the majority of which occur in remote habitats
isolated from their bisexual congeners. According to Cuellar (8), the major reason for
the insular distribution of parthenogenetic species is the ability of single individuals to
find a new colony without a member of the opposite sex. Assuming that
parthenogenetic species are truly superior colonizers and have evolved in isolation
away from their bisexual progenitors (6, 8); then, competition does not appear to
have played an important role in their evolution. Aside from the potentially disruptive
influence of competition on the establishment of unisexual clones, fertilization of
virgin females would also eliminate unisexual lineages by disrupting all-femaleness
as well as the meiotic process which regulates constancy of ploidy and the integrity
of the species (6, 7). At least initially, therefore, parthenogenetic species must
escape their bisexual counterparts in order to find new colonies. As long as they
remain isolated from the bisexuals, they can circumvent extinction.
Although sexuality is the predominant mode of reproduction among all organisms, it
is not entirely devoid of costs. The most common of these are meiosis and the
Toxins incl. Trop. Dis., 2008, 14, 1, p.
production of males (37, 61). As stated by Mayr (38), “in parthenogenetic animals, all
zygotes are egg-producing females that do not waste half of their eggs on males.”
Nevertheless, sexual reproduction has the long-term advantage, which is
undoubtedly the reason why it has appeared several times during evolutionary
history and is the principal reproductive mechanism in living organisms (1, 36, 61). In
contrast, parthenogenesis is only advantageous under special environments (8), may
not be very old evolutionarily (1), and is considered to be an evolutionary blind alley
(59, 60).
As previously pointed out by Cuellar (8), an enormous volume of literature has
appeared on animal parthenogenesis in the last 35 years. This ranges from
understanding their genetic structure, phylogenetic and systematic relationships,
ploidy, mechanisms of meiosis, competitive interactions with bisexual species,
modes of origin and, to a much lesser extent, their ecology and geographic patterns
of distribution (1, 7, 8, 60). As a matter of fact, these last two fields remain the least
understood of all the phenomena concerned with the origin of parthenogenesis.
Most research on different zoological groups has been concerned with attempting to
determine whether parthenogenesis has resulted directly from hybridization, despite
the fact that no one has ever produced a parthenogenetic strain through hybridization
(7). The principal field of research is molecular genetics, and the principal tools are
protein electrophoresis and analysis of mitochondrial DNA. Although such molecular
studies have contributed extensively to the understanding of clonal inheritance, we
have progressed very little ecologically since Vandel (54) first published his classical
study on the geography of parthenogenetic animals almost 80 years ago.
The contribution by Vandel (54) was exceptionally important for modern workers
because it established for the first time a connection between parthenogenesis and
specific environments, for which Vandel coined the term ‘parthénogenèse
géographique.’ It is known today as Vandel’s ‘rule of geographic parthenogenesis’.
According to this rule, whenever closely related bisexual and parthenogenetic
species occur in a given region, their geographical patterns tend to be different. In
general, the parthenogenetic species occur in habitats that are further north or
higher, colder or drier than those of their bisexual counterparts (Figure 14). Vandel
(54) developed his rule when analyzing the distribution of the different races of the
Toxins incl. Trop. Dis., 2008, 14, 1, p.
isopod Trichoniscus elisabethae. He noted that the bisexual populations occurred
only in the mountains of Southern France, which are extensively forested and damp,
whereas the parthenogenetic populations occupied lower and drier regions. Vandel’s
rule has now been widely cited by modern workers (6, 8, 11, 12, 60), and numerous
new examples have been added to his original list (16, 47, 48, 60).
As already emphasized by Cuellar (8), however, the exact ecological reasons for
these different geographic distributions have not yet been clearly elucidated.
Moreover, there is no conclusive evidence demonstrating that cold alone, aridity, or
high latitudes are responsible for the differences in distribution. Parthenogenesis is
also common at low latitudes as well as in tropical environments which are humid
and warm. Therefore, some factors other than climate and latitude must be involved
in determining its varying different geographic patterns. In discussing the distribution
of Vandel’s isopod Trichoniscus elisabethae, White (59) suggested that the main
reason for the peripheral distribution of the parthenogenetic races might be that they
have found it easier to expand their ranges merely because every individual was
capable of founding a local colony of the species and there was no reproductive
wastage. In proposing this explanation, White emphasized two important attributes of
parthenogenetic animals: a stronger dispersal ability and a higher prolificity
compared with those of bisexuals. Cuellar (6, 8) later suggested that parthenogenetic
species can only exist in habitats that are devoid of bisexual species, first because
fertilization would disrupt the perpetuation of a pure unisexual lineage and, secondly,
competition would impede its expansion. Consequently, parthenogenesis should
theoretically evolve in habitats where males tend to be rare, in remote or insular
habitats where both sexes of a bisexual species are not likely to arrive
simultaneously and, finally, in newly created habitats where high prolificity allows
parthenogenetic forms to invade first, and then to outcompete bisexuals (Figures 14
and 15).
Tityus serrulatus Lutz & Mello, 1922
In the first recorded case of parthenogenesis among scorpions (34), pregnant
females of Tityus serrulatus from Brazil were collected in the field. Their all-female
progeny were then raised individually, giving virgin birth to a second generation from
Toxins incl. Trop. Dis., 2008, 14, 1, p.
four to seven months later. Matthiesen’s (34) findings were confirmed some years
afterwards by San Martin and Gambardella (46). Thereafter, Tityus serrulatus was
considered to be an obligate parthenogenetic species. Recently, however, a possible
bisexual population has been detected in the state of Minas Gerais (Figure 16),
Brazil, by Lourenço and Cloudsley-Thompson (23). Tityus serrulatus may possibly
have originated as a savanna-dwelling species (Figure 17), or perhaps inhabited
palm trees. Today, however, it is virtually restricted to human habitations (Figure 18)
and the natural savannas have been converted to agriculture and grazing. Its
postulated original habitat of isolated palm trees within a vast savanna would
conform with the concept of insular parthenogenesis proposed by Cuellar (6, 8) for
the origin of parthenogenetic lizards. According to this author, the chances of
colonizing remote or isolated habitats “are greater if the colonizer can reproduce
without a member of the opposite sex, for it dispenses with the need to have both
sexes reach the same place simultaneously.” With the expansion of human
communities in Western Brazil, the geographic range of T. serrulatus has increased
considerably. Accordingly, it poses an exceptional health problem in Brazil, due not
only to its innate prolificacy and rapid expansion into urban areas, but also to its great
toxicity. This species possesses the most lethal venom of all the South American
scorpions (22, 25, 27, 31).
Within historical times, Tityus serrulatus occupied a restricted area in the state of
Minas Gerais in Brazil, but today it is widely distributed throughout the southeast and
central-western regions of the country. The geographical expansion of this species
has undoubtedly been related to human colonization, which began about 300 years
ago from the Atlantic coastal region westward. Typically, newly erected towns are
invaded within a few years after their foundation, although the surrounding natural
areas are virtually devoid of this species of scorpion. The rapid expansion of T.
serrulatus into human dwellings was recently demonstrated by its invasion of Brasilia
(30). Construction of Brasilia, the capital of Brazil, was initiated in 1956 and
completed during the 1970’s. From 1971 to 1975, a precise inventory of the local
scorpions and their densities was conducted in this region, yielding three species (17,
18): Tityus fasciolatus Pessôa, 1935, Bothriurus araguayae Vellard, 1934 and
Ananteris balzani Thorell, 1891 (17, 18). Among these, T. fasciolatus represented
93% of the total population. This species is similar to T. serrulatus in several traits.
Both average essentially the same adult size (65 versus 67mm), same brood size,
Toxins incl. Trop. Dis., 2008, 14, 1, p.
same embryonic development (2.5–3 months) and the same age to maturity (2.0–2.5
years). However, T. fasciolatus is bisexual, with a sex ratio of 1 male to 3 females.
The two species also differ in their type of population regulation, that of T. fasciolatus
being density-dependent and that of T. serrulatus density-independent.
Consequently, the populations of T. fasciolatus have been stable for many years
(17), whereas those of T. serrulatus have fluctuated widely (30). Since the
introduction of T. serrulatus into Brasilia and the adjoining of Federal District during
the late 1980’s and early 1990’s, the populations of T. fasciolatus have been rapidly
declining. A new inventory conducted more recently revealed that T. serrulatus now
constitutes 70% of the scorpions in this urbanized region (30, 31), and is undoubtedly
displacing the bisexual T. fasciolatus. Other cities in Brazil have been similarly
invaded (22, 25, 27).
Scorpionism is well known in Brazil and has been documented there since the end of
the 19
Century (22, 25, 31). The first comprehensive study of the phenomenon was
that of Maurano (35), whose work dealt primarily with Tityus bahiensis (Perty, 1833),
the second most toxic species in South America. This species was originally
described in Brazil.
Before the publication of Maurano’s work, not much had appeared in the literature
about scorpion problems in Brazil. This is curious because of the enormous health
problem caused by scorpions there today.
The fact that Maurano’s work dealt only with T. bahiensis, as well as that antivenom
serum has been produced from this species since 1915, can probably be explained
by the fact that T. serrulatus was not described until 1922. However, one important
question can be addressed: how is it that such a common species as T. serrulatus,
well known since the 1920’s, had not been observed previously and was described
rather later than the other common species? According to Magalhães (33), his
laboratory in Minas Gerais received 600,000 specimens between 1922 and 1952.
I have suggested (18) that T. serrulatus may be closely related to Tityus stigmurus
(Thorell), a species (Figure 7) with both sexual and parthenogenetic populations and
with a current distribution further to the north than that of T. serrulatus. Several other
authors, however, have refused categorically to recognize the possible existence, in
the past, of a southern distribution of T. stigmurus covering the present geographic
range of T. serrulatus (40, 45, 57). Others affirm that, before 1920, T. stigmurus was
a common species in the central and southern regions of Brazil in the states of Minas
Toxins incl. Trop. Dis., 2008, 14, 1, p.
Gerais, São Paulo and Goiás, where it lived sympatrically with T. serrulatus (39, 56).
During the late 1970’s, I was able to discuss this personally with Jean Vellard and to
examine some of the material that he collected in the late 1920’s, thereby confirming
his results. Tityus stigmurus was undoubtedly a common species in the state of
Minas Gerais and south of Goiás, at least until the late 19th Century.
Tityus stigmurus was originally described from the state of Pernambuco in the
Northeast of Brazil. This is due to the fact that such region had been prospected
earlier in Brazilian history. In the recent past, about 300 years ago, the distribution of
T. stigmurus ranged from Minas Gerais to the northeastern states of Brazil. The date
at which the parthenogenetic species T. serrulatus appeared de novo is difficult to
establish. However, if T. serrulatus was already present in Minas Gerais before the
beginning of the 18th Century, its presence was extremely inconspicuous. At the
beginning of the 18th Century, an important development was engendered by the
Portuguese (especially in their search for gold) with the foundation of towns such as
Curral d’El Rei and Vila Rica de Ouro Preto (15). Previously metaclimax
environments suffered human impact, turning them into a disclimax situation. This
favored the previously discrete parthenogenetic population of Tityus serrulatus, a
much more opportunistic species than T. stigmurus, and enabled it to explore the
newly created disclimax habitat. The expansion of human colonization toward the
west and north resulted in a significant regression of the original bisexual population
of T. stigmurus, which was gradually replaced by a population of T. serrulatus. As
already mentioned, this species usually colonizes urban areas (cities and tows), and
can easily be transported by human agency from old to new cities. Brasilia has been
invaded and was colonized by T. serrulatus in less than 15 years (30).
Tityus columbianus (Thorell, 1876)
Parthenogenesis was first demonstrated in Tityus columbianus (Figure 4) by
Lourenço (20). Although only females had been detected in this Colombian species
since its description, Lourenço (20) also cited the discovery of a single male in the
northern part of its range. Subsequently, a 250km survey conducted throughout its
entire range (Figure 19) revealed the presence of a sexual population in the northern
region, with a female to male sex ratio of about 2:1. The geographic differences in
reproductive effort between sexual populations of this species (from Iza - Figure 20)
and parthenogenetic populations (from Mosquera – Figure 21), both in Colombia,
Toxins incl. Trop. Dis., 2008, 14, 1, p.
were compared (29). The sexual females from Iza were significantly larger and had
markedly greater relative litter masses (RLM) than had the parthenogenetic females
from Mosquera (Figure 22). In both populations, litter size increased significantly with
female body size. Iza receives significantly more precipitation during the critical
growing season and is also significantly warmer than Mosquera. In addition,
Mosquera experiences a distinct period of drought in the middle of the summer. This
limits productivity to spring and autumn (for precise values see Lourenço et al. (29)).
The heavier body weights and larger litters of the sexual individuals may therefore be
due to environmental differences in primary productivity (29).
Tityus metuendus Pocock, 1897
Tityus metuendus (Figure 8) is a rainforest species distributed mainly in Western
Amazonia between Brazil and Peru. In the vicinity of Manaus, Brazil (specifically in
the Ducke Reserve), the populations of T. metuendus are strictly sexual with equal
numbers of males and females (19). During field studies in the Amazonian region of
Peru, near Iquitos (the town of Jenaro Herrera), a single juvenile female of T.
metuendus was collected from a palm tree (Astrocaryum chambira – Figure 23) and
brought to the laboratory in Paris (13). About three months after its last molt, on
October 18, 1996, this female gave birth to a brood of 21 neonates. Of these, only
three (all males) survived to the adult stage (Figure 24). A detailed examination of the
size and structure of the pectines of the immature specimens, which died and were
preserved, revealed that the entire brood consisted of males. On September 29,
1997, the same female produced another brood of 32. Three of these did not
complete embryological development and 29 were normal. The normal ones all died
a few days after the first molt. As with the previous brood, examination of the
pectines revealed only males. A third all-male brood was born on April 30, 1998,
bringing further evidence of the possible existence of arrhenotoky in this species. The
production of three consecutive all-male broods by the same virgin female may well
represent the first known case of arrhenotoky (the production of males from
unfertilized eggs) in scorpions (24, 28), and possibly among all Arachnida other than
Acari (42). No data are yet available from scorpions, as there are for other arthropod
groups, such as the Hymenoptera (7, 58) and mites, to explain either the meiotic
mechanism of arrhenotoky or its evolutionary significance (3). According to Taylor
and Sauer (50), a major selective advantage of arrhenotoky compared with diploidy
Toxins incl. Trop. Dis., 2008, 14, 1, p.
is that mothers can precisely determine the sex ratios of their offspring by controlling
the fertilization of each egg. This is particularly advantageous in species with finite
mating groups in which the probability is high that some clutches may contain no
males (42), or in which the sex ratio may be biased in favor of females (5). Precise
sex ratios have been documented in the case of several arrhenotokous species of
parasitic wasps (58) which lay their eggs either in a single host or in a clumped group
of hosts. In phytoseiid mites, pseudo-arrhenotoky has apparently arisen as a
consequence of low mobility and a subdivided population structure. Their dominant
prey form patchy infestations which are probably invaded by only a few females,
leading to very small mating groups (42). Similar mating conditions may exist for T.
metuendus, but extensive field work will be needed to explain its life history and
A few specimens, males and females, of a scorpion belonging to a new species of
the genus Tityus were collected alive by a group of biologists in November 2001 –
January 2002 in the ‘Pico da Neblina’, located between Brazil and Venezuela, at
altitudes ranging from 850–2200m. They were brought to the laboratory and raised,
according to standard methods, in plastic boxes at temperatures of +27°C, with food
and water provided once every week. Courtship and mating behavior of two females
was observed. They gave birth to 14 and 15 offspring, respectively, of which a few
were isolated and reached maturity. Three isolated females were maintained in
rooms were the temperature averaged +18°C. Food and water were provided only
once every 21 days. They gave birth to several broods without being inseminated,
suggesting a new example of parthenogenesis in scorpions. Postembryonic
development was achieved by most members of the different broods and revealed
that all the broods were composed of males and females, suggesting the first case of
deutherotokous (male and female brood) parthenogenesis. Parthenogenetic broods
were smaller – 1 to 8 offspring – than sexual broods (Figure 25). Moreover, the
developmental periods observed in the parthenogenetic broods were shorter than
those observed in other species of Tityus studied (21).
‘Pico da Neblina’ is located in North-Western Amazonia. It is characterized by
considerable diversity of habitats resulting from an orographic zonation of vegetation
Toxins incl. Trop. Dis., 2008, 14, 1, p.
and a mosaic pattern of soil types, ranging from 100 to near 3000 meters above sea
level. Lowland primary tropical rainforest is the predominant ecosystem (2). The
vegetation is luxurious from 100 to up to 1000 meters; it is more open and composed
of small trees from 1000 to 1700 meters. From 1800 meters up to the top of the
mountain, the vegetation is very low and the climate much drier. In fact, precipitation
is important up to 1000 meters, and the climate is very wet. Temperatures in the wet
zones range from 28 to 34°C during the day and from 20 to 24°C at night. At altitudes
above 2000 meters, conditions are much drier and stressful. Rain is sparse and
average temperatures fluctuate from 22°C during the day to 12°C at night.
The new species of Tityus was collected in sites ranging from the mesic zones to the
drier zones. When the abiotic conditions of more xeric zones are reproduced in the
laboratory, parthenogenesis appears to be the most advantageous mode of
reproduction. This seems to be in accordance with Vandel’s (54) rule of geographic
parthenogenesis. Several aspects of the reproductive biology of this species are still
under investigation. It will be described, and its complete life cycle outlined later.
Figure 1. Parthenogenetic female of Tityus serrulatus with brood.
Toxins incl. Trop. Dis., 2008, 14, 1, p.
Figure 2. Building of the Department of Zoology in the University of Rio Claro in the
late 1960’s, where F. Matthiesen did his work.
Figure 3. Tityus uruguayensis in a gregarious position.
Figure 4. Tityus columbianus in a gregarious position.
Toxins incl. Trop. Dis., 2008, 14, 1, p.
Figure 5. Male of Tityus trivittatus.
Figure 6. Female of Tityus trivittatus.
Figure 7. Parthenogenetic female of Tityus stigmurus with brood.
Toxins incl. Trop. Dis., 2008, 14, 1, p.
Figure 8. Birth behavior in parthenogenetic female of Tityus metuendus.
Figure 9. Female of Centruroides gracilis.
Figure 10. Female of Hottentotta hottentotta.
Toxins incl. Trop. Dis., 2008, 14, 1, p.
Figure 11. Parthenogenetic female of Hottentotta caboverdensis with brood.
Figure 12. Female of Liocheles australasiae with brood.
Toxins incl. Trop. Dis., 2008, 14, 1, p.
Figure 13. Map showing the distribution of parthenogenetic populations of scorpions.
Figure 14. Schematic representation of the distribution of sexual and parthenogenetic
populations (geographic parthenogenesis).
Toxins incl. Trop. Dis., 2008, 14, 1, p.
Figure 15. Theoretical curves representing the difference between sexual (dotted
line) and parthenogenetic (solid line) population fluctuations in nature. The beginning
of each curve, up to line K (carrying capacity), represents the growth rate during the
invasion of new habitats. Thereafter, sexual populations fluctuate close to K, whereas
the parthenogenetic populations fluctuate radically, overshooting K between
catastrophes due to a high rate of increase, and crashing to a low level during
catastrophes (adapted from Cuellar - 6).
Figure 16. Geographical distribution of Tityus serrulatus (zone I) and possible
location of the sexual population in the north of Minas Gerais State (black circle).
Toxins incl. Trop. Dis., 2008, 14, 1, p.
Figure 17. Female of Tityus serrulatus in the wild.
Figure 18. Parthenogenetic female of Tityus serrulatus in the sewer system of
Brazilian cities.
Toxins incl. Trop. Dis., 2008, 14, 1, p.
Figure 19. Location of Mosquera and Iza in Colombia where parthenogenetic (P) and
sexual (S) populations of Tityus columbianus are distributed.
Figure 20. The moist valley at Iza.
Toxins incl. Trop. Dis., 2008, 14, 1, p.
Figure 21. The dry canyon at Mosquera.
Figure 22. Correlation between clutch size and female body size for Iza and
Mosquera populations of Tityus columbianus (from Lourenço et al., 29).
Figure 23. Palm tree, Astrocaryum chambira, in Peruvian Amazon, where
parthenogenetic female of Tityus metuendus was collected.
Toxins incl. Trop. Dis., 2008, 14, 1, p.
Figure 24. Fifth instar adult male of Tityus metuendus issued from parthenogenetic
Figure 25. Female of Tityus sp. from ‘Pico da Neblina’ (Brazil / Venezuela) with
parthenogenetic brood composed of a single offspring.
I am very grateful to Professor John L. Cloudsley-Thompson, London, for reviewing
the manuscript. My thanks go also to several colleagues who supplied me with
photos used in this article: Eric Ythier, Jan Ove Rein, Elisangela A. da Silva, and
Benedito Barraviera.
Toxins incl. Trop. Dis., 2008, 14, 1, p.
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California: Benjamin & Cummings, 1983. 316p.
4 CAMACHO JP. Female-biased sex ratio in spiders caused by parthenogenesis.
Hereditas, 1994, 120, 183-5.
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... One of the first steps in planning the production of a specific serum is the proven medical relevance of the animal species, followed by an established methodology for creation and programmed extraction of venoms (Batista et al., , 2018. The main scorpion species for serum production is T. serrulatus, which is relatively easy to keep in captivity (Lourenço, 2002), in part due to this animal's potential to live in an anthropic environment and reproduction facilitated by parthenogenesis (Lourenço, 2008). ...
... Venom extracted from scorpions serves as an antigen that is inoculated in horses for antibody production (Salazar et al., 2022). Studies on reproductive aspects of Amazonian scorpions are rare (Lourenço, 2008), and most broods born in the laboratory are from females that came pregnant from the forest (Outeda-Jorge et al., 2009). In addition, an adequate way to keep these animals in artificial environments in the short and long term is not known (Martins et al., 2021). ...
... Although animal venom has geographical features (Calvete, 2017), it is important to verify the relationship between the regional symptoms caused by T. obscurus and the different median lethal doses (LD 50 ) detected in the venoms of their populations (Fig. 4). When compared to other scorpion species that are better known through scientific studies, such as T. serrulatus and T. bahiensis (Lourenço, 2008), the venom of T. obscurus has not yet been widely characterized (Gomes et al., 2020;Cupo, 2015;Wen et al., 2015). There are few proteomic studies to elucidate the diversity of toxins in this venom (Martins et al., 2021) and their effects on the immune system (Torrez et al., 2015). ...
Tityus obscurus has caused mild, moderate and severe accidents of medical relevance in the eastern Brazilian Amazon and French Guiana. Tityus obscurus has sexual dimorphism although males and females have uniform black coloration. In the Amazon, one of the habitats of this scorpion is seasonally flooded forests (igapós and várzeas). However, most stings occur in terra firme forest areas (non-flooded region), where most rural communities are located. Adults and children stung by T. obscurus may experience an “electric shock” sensation for more than 30 h after the sting. Our data shows that people inhabiting remote forest areas, including rubber tappers, fishermen and indigenous people, with no access to anti-scorpion serum, use parts of native plants, such as seeds and leaves, against pain and vomiting caused by scorpion stings. Although there is a technical effort to produce and distribute antivenoms in the Amazon, many cases of scorpion stings are geographically unpredictable in this region, due to the lack of detailed knowledge of the natural distribution of these animals. In this manuscript, we compile information on the natural history of T. obscurus and the impact of its envenoming on human health. We identify the natural sites that host this scorpion in the Amazon, in order to warn about the risk of human envenoming. The use of specific antivenom serum is the recommended treatment for accidents involving venomous animals. However, atypical symptoms not neutralized by the available commercial antivenom are reported in the Amazon region. Facing this scenario, we present some challenges to the study of venomous animals in the Amazon rainforest and possible experimental bottlenecks and perspectives for establishing a method aimed at producing an efficient antivenom.
... This population increase occurs via thelytokous parthenogenesis (all-female brood), wherein no males are required for reproduction and no egg wastage occurs from producing males (Mayr, 1963;Cuellar, 1997;Ross, 2010). Therefore, this feature is an important adaptive mechanism that allows females to quickly colonize new areas, mainly in disturbed environments such as urban areas where encounters with males are difficult (Cuellar, 1977;Lourenço, 2008). However, parthenogenesis is unfavorable to populations over long periods because clonal lineages have reduced genetic variability due to an absence of oocyte-sperm interactions (Lourenço, 2008). ...
... Therefore, this feature is an important adaptive mechanism that allows females to quickly colonize new areas, mainly in disturbed environments such as urban areas where encounters with males are difficult (Cuellar, 1977;Lourenço, 2008). However, parthenogenesis is unfavorable to populations over long periods because clonal lineages have reduced genetic variability due to an absence of oocyte-sperm interactions (Lourenço, 2008). These characteristics make parthenogenetic animals good models for studies of developmental biology because they allow side-by-side evaluation of different phenotypes produced by the same genome in single or distinct environments (Vogt, 2015). ...
... Previous studies pointed out that uncontrolled urbanization provides suitable conditions for proliferation of synanthropic scorpions (Brazil & Porto, 2010;Torrez et al., 2019). Furthermore, because parthenogenesis enables a density-independent process of population growth, parthenogenetic scorpions may have a rapid colonization in urban environments (Lourenço & Cloudsley-Thompson, 1999;Lourenço, 2008). For example, Brasília is a Brazilian city created from scratch in the second half of the twentieth century and it was estimated to be colonized by the parthenogenetic scorpion T. serrulatus in less than 15 years (Lourenço et al., 1994). ...
Clonal lineages in similar environments may be influenced by non-Mendelian inheritance, such as maternal age effects and developmental instabilities. These mechanisms may affect the developmental fitness of parthenogenetic litters. In this study, the scorpion Tityus stigmurus (Thorell, 1876) was used to analyze the effects of non-Mendelian variation on parthenogenetic litters. A total of 75 juveniles from five females were reared under the same controlled conditions, while their development was observed and evaluated through differences in offspring fitness traits (litter size, prosoma size, developmental time, and mortality) between the litters. First and second litters had a similar litter size, although second litters exhibited longer developmental time in the early instar stages (second and third) than first litters. These results indicate that T. stigmurus females allocated nutrient resources to maximize litter size rather than developmental fitness in subsequent litters. Differences in developmental time found in early instars but not in late instars may have occurred as a result of stochastic developmental variations in young individuals. Such variation in duration of development has the potential to influence survival of juveniles in natural environments because individuals that grow faster may avoid large predators and consume larger prey, compared to those that do not.
... The most frequent form of reproduction in scorpions involves the indirect transfer of male gametes via spermatophores, and occurs after an elaborate and ritualized courtship (Polis & Sissom 1990;Stockmann 2015). However, some species can also reproduce by parthenogenesis, in which females generate offspring without the genetic contribution of males (Francke 2008;Lourenço 2008). For these species, males are considered rare (Lourenço 2008(Lourenço , 2015, and parthenogenesis is assumed to be the main method of reproduction (Warburg 2011;Ayrey 2017;Seiter & Stockmann 2017). ...
... However, some species can also reproduce by parthenogenesis, in which females generate offspring without the genetic contribution of males (Francke 2008;Lourenço 2008). For these species, males are considered rare (Lourenço 2008(Lourenço , 2015, and parthenogenesis is assumed to be the main method of reproduction (Warburg 2011;Ayrey 2017;Seiter & Stockmann 2017). Consequently, behavioral studies addressing the courtship repertoire in scorpions that can reproduce by either method (i.e., sexual reproduction or parthenogenesis) are extremely rare, and this in turn leads to incorrect generalizations about the reproductive biology of these species. ...
... This is especially true for medically important species such as T. stigmurus, which is one of the most harmful scorpions in South America. For example, in this species, parthenogenetic populations are expected to be more dispersive and proliferative, in part due to density-independent demographic processes (Lourenço 2008). Hence, an understanding of the reproductive biology of such understudied species can provide basic scientific knowledge for the establishment of public health strategies aimed at mitigating recurrent problems related to scorpion envenomation (Lourenço 2015). ...
Parthenogenesis and sex-ratio bias may lead to erroneous assumptions concerning the natural history of some arachnids. To help address this issue, this study provides new data on the sex ratio and geographic distribution of sexual populations of the scorpion Tityus stigmurus (Thorell, 1876). Ultraviolet light lanterns were used to detect specimens during nocturnal searches performed in both urban and non-urban environments scattered thorough northeastern Brazil. Males of T. stigmurus were reported for 10 new localities, and although we did not find males in urban environments, non-urban populations presented near symmetrical sex ratios. Such results suggest that reproductive strategies in this species may be modulated by environmental conditions. Also, the general tendency of less biased sex ratios in non-urban environments reported here is in accordance with previous studies that indicated the occurrence of geographical parthenogenesis in this species. Thereby, we propose that sexual populations of T. stigmurus are less rare than previously reported.
... This species' geographic distribution was previously restricted to Minas Gerais state (Southeast region), but due its easy adaptation to urban environments and its proliferation potential, T. serrulatus has expanded considerably over the Southeast, Northeast, South, and Central regions of Brazil, and its occurrence has been recorded in at least 19 of the 27 Brazilian states [4,[72][73][74][75][76]. T. serrulatus has been also spotted in other countries like Ecuador and Argentina [77], where even a human accident occurred [78]. Its ability to reproduce by parthenogenesis is one of the factors that seems to contribute the most to T. serrulatus rapid proliferation and wide distribution [79]. A single specimen transported to a new location, finding the right conditions, can readily reproduce and develop a new colony [17]. ...
... Like T. serrulatus, T. stigmurus is predominantly parthenogenetic, with few recorded sexual populations [79,91]. T. stigmurus also present a yellowish body color and may have a superimposed occurrence in the Cerrado and Atlantic Forest biomes with T. serrulatus, which makes it difficult to estimate the real contribution of each species to the epidemic scenario in some parts of the Northeast region, as both species are synanthropic and well adapted to urban centers [43,60,92]. ...
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Opportunistic scorpion species can colonize urban environments, establishing high-density communities that enhance the chances of human accidents. This scenario has been taking place in Brazil, in which some Tityus species have taken city centers, causing an explosion in the number of scorpion envenoming cases. The characteristics of this scorpionism epidemic in Brazil is discussed in the present work. The number of Brazilian scorpion stings has surpassed 120,000 cases in 2017, and has been maintained above this number ever since, representing a more than 3-fold increase in 10 years, which was higher than the number of cases for most of the neglected tropical diseases in the country. The escalation in scorpionism cases is even higher in some regions of Brazil. Fortunately, the proportion of mild cases has also increased in the analyzed period, as well as the number of victims seeking for medical attention within the first hour after the accident. The species Tityus serrulatus, Tityus stigmurus, Tityus bahiensis, and Tityus obscurus are traditionally accountable for most of the scorpion accidents in different regions of Brazil, but other species deserve to be closely watched. Despite scorpionism being a notable health problem in Brazil, accident prevention and pest control regarding this venomous animal have not been properly addressed by the scientific community nor by policy makers. Therefore, this review also aims to point possible fields of research that could help to contain the aggravation of the current scorpionism landscape in Brazil.
... In a series of previous publications addressed to the readers of the Journal of Venomous Animals and Toxins including Tropical Diseases (JVATiTD), I attempted to bring general information about scorpions and scorpionism, but also on models of reproduction and in particular parthenogenesis [1,2,3]. Even some notions about how to proceed with systematics and taxonomy were the subject of one article [4]. ...
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Abstract This synoptic review aims to bring some general information on fossil scorpions, namely those trapped in amber - fossilized resin - ranging from Lower Cretaceous through the Palaeocene and up to the Miocene. The question to be addressed is how the study of these fossils can be connected with possible present scorpionism problems. A precise knowledge of these ancient lineages provides information about the evolution of extant lineages, including the buthoids, which contain most known noxious species. Among the Arthropods found trapped in amber, scorpions are considered rare. A limited number of elements have been described from the Late Tertiary Dominican and Mexican amber, while the most ancient Tertiary amber from the Baltic region produced more consistent results in the last 30 years, primarily focusing on a single limited lineage. Contrarily, the Cretaceous amber from Myanmar, also called Burmite, has yielded and continues to yield a significant number of results represented by several distinct lineages, which attest to the considerable degree of diversity that existed in the Burmese amber-producing forests. As in my previous similar contributions to this journal, the content of this note is primarily addressed to non-specialists whose research embraces scorpions in various fields such as venom toxins and public health. An overview knowledge of at least some fossil lineages can eventually help to clarify why some extant elements associated with the buthoids represent dangerous species while others are not noxious.
... A single female can have an average of two births per year, with an average of 18-25 young scorpions per gestation, which makes control work difficult. The species originally lived in transition forest, dry forest, savanna, and caatinga environments, a restricted area in the state of Minas Gerais 6,7 . Currently, this species lives in habitats with minimal vegetation, being an endemic species in Brazil, and proliferates widely in states such as Bahia, Espírito Santo, Minas Gerais, Rio de Janeiro, São Paulo, Paraná, and Goiás, covering the northeast, midwest, and southeast regions of Brazil 2 . ...
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Background: Scorpions are a leading cause of envenomation in Brazil. The species Tityus serrulatus is associated with the most severe cases, especially in children. Despite not being endemic to the state of Santa Catarina, such occurrences have increased more than 500% in the state recently. Therefore, this study aimed to analyze the occurrence of envenomation by T. serrulatus, attended by the Center for Toxicological Information and Assistance of Santa Catarina. Methods: This was a retrospective and descriptive study of the occurrence of T. serrulatus, identified by the agency, from 2014 to 2021 in Santa Catarina, using data obtained by the BI-DATATOX system. Results: A total of 112 occurrences were classified as envenomation. Of these cases, 48.2% were recorded in the Itajaí Valley region and 33% in Greater Florianópolis. Men were involved in 59.8% of these, and the most common age group was 20-39 years (39.3%). Most envenomation occurred in urban areas (89.3%) under non-occupational circumstances (83%). Stings were more frequent on the hands (50.9%). Care was sought within 1 h after the event in 75.9% of the cases, and 94.6% were classified as mild. Conclusions: Occurrence of envenomation involving T. serrulatus in Santa Catarina increased significantly during the study period. Most cases occurred in urbanized areas, which suggests that they might have been transported from other states, and it must be considered that, in the urban environment, scorpions find a large supply of food and shelter and a reduced number of specific predators, allied to parthenogenesis.
... Among the species of the family Buthidae, Tityus serrulatus is particularly interesting since, in all the comparative analyses we conducted, this species exhibit very dissimilar mitochondrial genomic features compared to other species in the same family (Figs. 2 and 4). In addition to their medical importance, scorpions belonging to the genus Tityus have been studied because they reproduce by parthenogenesis, which is an asexual process in which the embryo develops from an unfertilized egg (Lourenço, 2008). This type of reproduction has only been reported in eight scorpions , five of them belonging to the genus Tityus (Gary & Sissom, 2019). ...
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Scorpions are a group of arachnids with great evolutionary success within invertebrates comprising more than 2,000 species. Mitochondrial genomes in animals have been extensively studied and have been used mainly for phylogenetic studies, however, due to the low number of available mitogenomes mitochondrial genomes in scorpions have been little studied. We describe and compare different scorpion mitogenomes and analyze their architecture and molecular characteristics. We obtained eight new scorpion mitogenomes from transcriptomic data, annotated them, generated the secondary structures of tRNAs, compared the nucleotide composition, codon usage, and relative synonymous codon usage of 16 complete scorpion mitogenomes, and provided a phylogeny based on all mitochondrial coding genes. We characterized the mitogenomes in detail and reported particularities such as differential synteny in the family Buthidae compared to other scorpions, unusual secondary structures of tRNAs, and unconventional start and stop codons in all scorpions. Our comparative analysis revealed that mitogenomes show differential mitochondrial molecular architectures and features depending on their taxonomic group, we highlight the parvorder Buthida particularly the family Buthidae, as it invariably showed differential patterns in its mitogenome features such as synteny, codon usage, and AT bias compared to the Iurida parvorder encompassing the rest of the scorpion families we analyzed in this research. Our results provide a better understanding of the evolution of mitogenome features and phylogenetic relationships in scorpions.
... It is being replaced, in many peri-urban landscape scenarios, within Atlantic Forest residues, by the yellow scorpion T. serrulatus (Szilagyi-Zecchin et al. 2013;Torrez et al. 2019). This phenomenon reflects a growing adaptation of the species T. serrulatus to urban environments, favoured by its mode of reproduction (parthenogenesis) which allows it to gradually displace autochthonous and non-parthenogenic species, such as T. bahiensis, from its ecological niche (Lourenço 2008;Bucaretchi et al. 2014). ...
The brown scorpion Tityus bahiensis is a species of medical importance to the state of São Paulo. Citizens who encounter scorpions in their homes bring them alive to our public health vivarium. The age of the scorpions was unknown at the time of delivery, but the time was recorded as the start of their longevity in our terrarium. All scorpions were juveniles or adult when brought to us. Some were removed from the study and transferred to another facility for venom extraction and anti-venom production. For scorpions continuing in this study, handling was minimized, and no venom extraction was done. This survival time to death is considered important because dangerous scorpions are often maintained in public health vivaria for possible venom extraction. Data collection was within the time period from 2015 to 2021, with the distinguishing features of each scorpion used for identification. The survival time for males ranged from 42 and 503 days and for females 69 and 365 days. The half-life in captivity of the received scorpions was 285 (Confidence Interval: 203 to 365) days.
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The order Phasmatodea includes insects known as stick insects. In Brazil, few taxonomic, ecological or evolutionary studies have been published in recent years, the reason is related to the few number of researchers dedicated to this particular group. Cladomorphus phyllinus Gray is one of the largest Brazilian insects and perhaps one of the most studied species of Phasmatodea in the country. It is considered as a phytophagous, generalist, and feeds mainly on guava leaves (Psidium guajava), powder-puff (Calliandra sp) or Angico (Piptania sp.). Females of this species reproduce in a sexual and asexual manner, by the production of diploid daughters from unfertilized eggs (thelytokous parthenogenesis). The absence of records on the reproductive capacity of virgin parthenogenetic females of C. phyllinus led us to record the longevity, fertility, and eggs viability of ten specimens. The results obtained were compared to those found in the scientific literature for mated females of the same species. The fertility and eggs viability were observed to be much lower for the parthenogenetic females when compared to the mated females; however, the longevity for virgin females was longer than that recorded in the literature for mated females.
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Abstract A synopsis on the historical, geographical and ecological aspects related to the most conspicuous scorpion species of the genus Tityus known from Brazil is proposed. Tityus serrulatus Lutz & Mello, 1922 was described precisely one century ago, nevertheless many questions related to its ecological adaptations and geographical expansion remain without a precise response. This species, well known for its infamous reputation of noxious species, is also known for its capacity to reproduce asexually, by parthenogenesis. Although the individuals of a given population are considered clones, a new hypothesis could suggest the occurrence of mutations within isolated individuals, leading to distinct subpopulations that could present better phenotypic performances in ecological habitats distinct from those of the original area of distribution of the species.
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Parthenogenesis is rare in chelicerates with the exception of mites. In scorpions this form of asexual reproduction has been observed in some species of the families Buthidae and Liochelidae. In the present paper, parthenogenesis is reported in a species of scorpion inhabiting the Cape Verde islands and recently described as Hottentotta caboverdensis. The postem-bryonic development of H. caboverdensis is also described. The Cape Verde population of H. caboverdensis seems to be an obligate thelytokous (all-female broods) parthenospecies. Partenogénesis en los Hottentotta caboverdensis Lourenço & Ythier, 2006 (Scorpiones, Buthidae) de las islas de Cabo Verde Resumen: La partenogénesis es rara en los quelicerados, con excepción de los ácaros. En los escorpiones esta forma de re-producción asexual se ha observado en algunas especies de las familias Buthidae y Liochelidae. En el presente trabajo se se-ñala la existencia de partenogénesis en una especie de escorpión que habita en las islas de Cabo Verde y que se ha descrito recientemente como Hottentotta caboverdensis. Se describe igualmente el desarrollo postembrionario de H. caboverdensis. La población de Cabo Verde de H. caboverdensis parece ser una partenoespecie, de telitoquia obligada (con sólo hembras).
A new parthenogenetic species of scorpion, Ananteris coineaui Lourenco, is reported from French Guyana. Parthenogenesis is based on the production of an all-female brood (thelytoky) by a wild virgin female. Conversely, the first probable case of male parthenogenesis (arrehnotoky) in scorpions is reported based on the production of two successive all-male broods by a wild caught virgin female of Tityus metuendus Pocock from Peru. Both species were found in isolated palm trees within the rain forest, conforming with the insular theory of parthenogenesis.