A review of scorpion reproductive strategies

Michael Warburg has recently published an interesting review on scorpion reproductive strategies. In addition to reviewing the existing knowledge on this topic, he also makes suggestions about future research on this topic.

Abstract:
Most scorpion species are iteroparous, breeding more than once during their life. Some of these species are parthenogenetic. The other reproductive strategy (RS) semelparity, when scorpions breed only a single time during their life, is rare and has been documented only once. The mass allocated by the female to produce either a litter or a single offspring is the reproductive allocation (RA). It is difficult to calculate RA since the difference in female mass before and after parturition is difficult to obtain. In addition, the litter size is hardly ever accurate because of maternal cannibalism. An attempt was made to calculate RA in Nebo hierichonticus (E. Simon, 1872). Based on litter size, on breeding frequency and on longevity of the female, it is possible to estimate the reproductive potential (RP). These aspects of scorpion reproduction are reviewed and the difficulties involved in this study are discussed.

Reference:
Warburg MR. Scorpion reproductive strategies, allocation and potential; A partial review. European Journal of Entomology. 2011;108(2):173-81. [Free fulltext]

Life cycle data for Opisthacanthus madagascariensis

Wilson Lourenco and co-workers have recently published a paper with life history data for Opisthacanthus madagascariensis (Hemiscorpiidae) from Madagascar.

Abstract:
Biological observations were made during the 1980s by the senior author on living specimens of Opisthacanthus madagascariensis Kraepelin, 1894. These were collected by French biologists on a field trip in 1980-1981 to the Parc National de Namoroka, Mahajanga Province, Madagascar. The total duration of embryonic development averaged 18 months. The moults necessary to reach the various juvenile instars and adulthood took place at average ages of 13, 101, 204, 327 and 442 days. These developmental periods are significantly longer than those of most medium-sized species of scorpions but are similar to the ones previously observed in other species of the genus Opisthacanthus. Morphometric growth values of the different instars are also similar to those in other known species of Opisthacanthus. A significant allometric growing of pedipalps is observed for some males collected in the field, suggesting the existence of at least one extra instar.

Reference:
Lourenco WR, Leguin E-A, Cloudsley Thompson JL. The life cycle of the Malagasy scorpion Opisthacanthus madagascariensis Kraepelin, 1894 (Liochelidae). Entomol Mitt Zool Mus Hamburg. 2010;15(183):173-82.

Family Hemiscorpiidae

Reproductive traits in Paruroctonus boreus

James Barron and Amy L. Weidlich have recently published a research note on reproduction in the Northen Scorpion, Paruroctonus boreus (Vaejovidae), which is one of the most widespread species in North America (and also the most northern species, ranging into southern Canada).

Abstract:
Despite its large geographic range, little is known about reproductive traits in the northern scorpion (Paruroctonus boreus). We analyzed reproductive traits for 36 females from a population near Billings, Montana. All data were collected within a single year. Litter size, offspring mass, total litter mass (TLM), and relative litter mass (RLM) were within the ranges of values reported for other species in the Vaejovidae. Female size (length or mass) was not correlated with any reproductive trait. Litter size and offspring mass were each positively correlated with RLM, suggesting that females investing relatively larger amounts of energy in reproduction increase both size and number of offspring. Finally, the within-litter coefficient of variation in offspring mass was negatively correlated with RLM, TLM, and mean offspring mass, suggesting that females investing more energy in reproduction produce more-uniformly sized offspring, an observation that appears common in scorpions.

Reference:
Barron JN, Weidlich AL. Reproductive traits in the northern scorpion (Paruroctonus boreus). West North Am Naturalist. 2009 Sep;69(3):399-402. [Free fultext]

Family Vaejovidae

Gestation period and litter size in Leiurus quinquestriatus

Luc Ross has recently published a research note on the gestation period and litter size in Leiurus quinquestriatus (Buthidae).

Abstract:
The following notes on gestation periods and litter size in seven specimens of Leiurus quinquestriatus are presented as observational data. Specimens of Leiurus quinquestriatus from southern Egypt and southern Israel were mated in the laboratory during 2007; afterwards, gestation periods and litter sizes of all females were recorded. Previous studies on this species reported that the gestation period ranged from 150 to 155 days and that litter size was between 12 and 99 offspring. In the present study, gestation periods in specimens from both geographic regions varied from 155 to 227 days and litter sizes were between 35 and 87 offspring. The current contribution expands on previously published data on gestation periods and supports previously reported litter size in Leiurus quinquestriatus.

Reference:
Ross LK. Notes on gestation periods and litter size in the arenicolous buthid scorpion Leiurus quinquestriatus (Ehrenberg, 1828) (Scorpiones: Buthidae). Journal of Venomous Animals and Toxins Including Tropical Diseases. 2009;15 (2):347-52.

Family Buthidae

Litter size, effects of maternal body size, and date of birth in South American scorpions

Outeda-Jorge, Mello & Pinto-da-Rocha have recently published an interesting article on litter size and date of birth in 21 South American species (first time data for 13 species). In addition, they also discuss the impact on maternal body size on number and size of scorplings. Multiple broods (without new matings) are also reported in seven buthid species.

This is a very interesting paper for those interested in scorpion reproduction, ecology and life history, but has also interest for those trying to breed South American scorpions in captivity.

Abstract:
We present new data on litter size and date of birth (month) for 21 South American scorpions species. We provide data for one katoikogenic species, the liochelid Opisthacanthus cayaporum Vellard, 1932 (offspring = 3; birth month: Jan); and for several apoikogenic species, such as the bothriurids Bothriurus araguayae Vellard, 1934 (53; Sep), B. rochensis San Martín, 1965 (22-28; Jan, Aug); the buthids Ananteris balzanii Thorell, 1891 (10-34; Jan-Mar), Physoctonus debilis (Koch, 1840) (2; Sep), Rhopalurus amazonicus Lourenço, 1986 (19; Nov), R. lacrau Lourenço & Pinto-da-Rocha, 1997 (30; Dec), R. laticauda Thorell, 1876 (41; Nov), R. rochai Borelli, 1910 (11-47; Dec-Jan, Mar-Apr), Tityus bahiensis (Perty, 1833) (4-23; Oct-Mar), T. clathratus Koch, 1844 (8-18; Nov-Jan), T. costatus (Karsch, 1879) (21-25; Jan, Apr), T. kuryi Lourenço, 1997 (4-16; Mar), T. mattogrossensis Borelli, 1901(8-9; May), T. obscurus (Gervais, 1843) (16-31; Jan-Feb, May, Jul), T. serrulatus Lutz & Mello, 1922 (8-36; Dec, Feb-Apr), T. silvestris Pocock, 1897 (5-14; Dec-Jan, Apr), T. stigmurus (Thorell, 1876) (10-18; Nov, Jan, Mar), Tityus sp. 1 (T. clathratus group - 7-12; Feb-Apr), Tityus sp. 2 (T. bahiensis group - 2; Mar); and the chactid Brotheas sp. (8-21; Jan, Apr). We observed multiple broods: R. lacrau (offspring in the 2nd brood = 27), T. kuryi (6-16), T. obscurus (2-32), T. silvestris (8), T. stigmurus (4-9), T. bahiensis (offspring in the 2nd brood = 2-18; 3rd = 1), and T. costatus (2nd brood = 18; 3rd = 4). We found statistically significant positive correlation between female size and litter size for T. bahiensis and T. silvestris, and nonsignificant correlation for T. serrulatus.

References:
Outeda-Jorge S, Mello T, Pinto-da-Rocha R. Litter size, effects of maternal body size, and date of birth in South American scorpions (Arachnida: Scorpiones). Zoologia. 2009;26(1):43-53. [Free fulltext]