16.02.2022

The ontogenetic development of tarantula spermathecae.

By Karin Hildebrandt

In contrast to Volker, who deals with the systematic and Taxonomy of tarantulas, primarily those from Asia, I concentrate on the sex determination and ontogenetic development of the male ( = gonads) and female (spermathecae) reproductive organs. For example, I am interested in the questions whether a single-lobed spermathecae in nymphal development starts as such and grows larger and larger, or whether it starts with two separate receptacles and gradually grows together. Furthermore, it will be interesting to learn what size spermathecae will have from molt to molt. Another question I am working on with the help of JProf. Dr. Henrik Krehenwinkel is whether the ontogenetic development of spermathecae possibly reflects the phylogeny of the taxon under study (currently especially Poecilotheria). Unfortunately, there are hardly any publications or studies on the mentioned questions. I try to fill this gap by my investigations. First results show a very interesting development of the spermathecae, which I want to illustrate with the example of a Haplocosmia sp..

Pic 1 shows the spermatheca of a juvenile female with a body length of about 1.5 cm. A distinct division of the spermatheca into two curved and highly sclerotized receptacles can be seen.

Pic 2 is from a larger female with a KL of about 2 cm. The receptacles are now connected, but the connection is still very thin and barely sclerotized.

Pic 3 shows the spermathecae of a female about 3.5 cm in size. The receptacles are now virtually completely fused together and the junction of the two is still very thin and unsclerotized only in the middle.

Pic 4 shows the spermathecae of a subadult female. Now the receptacles are completely joined and also the connecting junction between them is nearly completely sclerotized. Only the base of the spermatheca is not yet completely sclerotized in the middle.

Pic 5 shows the spermathecae of an adult female. Now the base of the spermatheca is also completely sclerotized.

Resumé:

Just such spermathecae, which are described as "single-lobed" or "single-lobed undivided" in the adult stage, start out as two independent receptacles in the course of their ontogeny and fuse together at the end to form a connected lobe. It remains exciting to observe whether this is so in all species with a single-lobed spermathecae, such as Haplopelma, Brachypelma, Tliltocatl, Sericopelma, etc.

Reference:

Bhatnagar R. D. S. & J. G. Rempel (1962): The structure, function and postembryonic development of the male and female copulatory organs of the black Widow Spider Latrodectus curacaviensis (Müller). Canadian Journal of Zoology. 40(3): 465-510.

Frederick A. C. et al. (1983): Observations on the Structure and Function of Spermathecae in Haplogyne Spiders. Transactions of the American Microscopical Society, Vol. 102, No. 3, pp. 272-280.

Tu, L. & G. Hormiga (2009): The female genitalic morphology of "micronetine" spiders (Araneae, Linyphiidae). Genetica 138, 59

Esche K. & S. Esche (2011): The genus Hemiercus Simon, 1903: husbandry and captive breeding of Hemiercus spec. ex Venezuela (Araneae, Theraphosidae, Ischnocolinae); ZAG Phoenix 2 (1).

Andre C. & S. Esche (2011): The genus Sericopelma: habitat, habits, terrarium husbandry, and captive breeding of Sericopelma melanotarsum Valerio, 1980; ARACHNE; 16(4).

Rivera-Quiroz F. et al. (2020): Imperfect and askew: A review of asymmetric genitalia in araneomorph spiders (Araneae: Araneomorphae). PLOS ONE 15(6)