''Cicurina madla'' is a rare species of

spider Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

in the family

Dictynidae Dictynidae is a family (biology), family of cribellate, hackled band-producing spiders first described by Octavius Pickard-Cambridge in 1871. Most build irregular webs on or near the ground, creating a tangle of silken fibers among several branche ...

known by the common name Madla Cave meshweaver. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

, United States, where it is known to originate from only eight or nine caves in

Bexar County Bexar County ( or ; es, Béxar ) is a county in the U.S. state of Texas. It is in South Texas and its county seat is San Antonio. As of the 2020 census, the population was 2,009,324. Bexar County is included in the San Antonio–New Bra ...

. This is one of a small number of invertebrates endemic to the karst caves of Bexar County that were federally listed as

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

in the year 2000. Another spider from the caves was described as ''Cicurina venii'', and given the common name Braken Bat Cave meshweaver. In 2018, it was synonymized with ''C. madla''.

Description

''Cicurina madla'' has no functional eyes. Females are cream-colored, with a body length of 4.8–6.7 mm, made up of a

cephalothorax The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...

2.3–3.3 mm long and 1.5–2.3 mm wide and an

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...

2.5–3.4 mm long and 1.5–2.1 mm wide. The fourth leg has the longest femur, 2.5–3.4 mm long. The

spermathecae The spermatheca (pronounced plural: spermathecae ), also called receptaculum seminis (plural: receptacula seminis), is an organ of the female reproductive tract in insects, e.g. ants, bees, some molluscs, oligochaeta worms and certain other in ...

are elongated. Males have a

palpal bulb The two palpal bulbs – also known as palpal organs and genital bulbs – are the copulatory organs of a male spider. They are borne on the last segment of the pedipalps (the front "limbs" of a spider), giving the spider an appearance often descr ...

with a relatively narrow, elongated cymbium and an oblong tegulum. Cokendolpher in 2004 constructed a "troglomorphy index" (TI) defined as the ratio of the sum of the lengths of the femur, patella and tibia of the first leg to the length of the cephalothorax. Higher values of the index indicate relatively longer legs and are associated with a troglodytic life-style. ''C. madla'', including the specimen described as ''C. venii'', produced ratios above 2.0, except for small immatures. ''C. madla'' can be distinguished from ''Cicurina'' species occurring in the same area by its TI index, as well as by genetic data and the structure of the female spermatheca or the male palpal bulb.

Taxonomy

''Cicurina madla'' was first described by

Willis J. Gertsch Willis John Gertsch (October 4, 1906 – December 12, 1998) was an American arachnologist. He described over 1,000 species of spiders, scorpions, and other arachnids, including the Brown recluse spider and the Tooth cave spider. Gertsch was born ...

in 1992. In the same paper, Gertsch described a spider as ''Cicurina venii'', giving its sole location as Bracken Bat Cave. Only two specimens assigned to ''C. venii'' were ever collected, but one is now lost. The entrance to Bracken Bat Cave has been filled in, and the cave cannot currently be accessed. It is located on private property. A study of ''Cicurina'' spiders from Texas caves in 2018 concluded that the sole known specimen of ''C. venii'' belongs to the same species as ''C. madla'', and synonymized them. The authors of the study suggested that either the specimen described as ''C. venii'' was in fact from Government Canyon Bat Cave, but was mislabeled or placed into an incorrect vial, or it was from Bracken Bat Cave, and so represents a further southern extension of the range of ''C. madla''. The synonymy is accepted by the

World Spider Catalog The World Spider Catalog (WSC) is an online searchable database concerned with spider taxonomy. It aims to list all accepted families, genera and species, as well as provide access to the related taxonomic literature. The WSC began as a series of ...

Ecology and conservation

The Bexar County karst cave invertebrates are

troglobite A troglobite (or, formally, troglobiont) is an animal species, or population of a species, strictly bound to underground habitats, such as caves. These are separate from species that mainly live in above-ground habitats but are also able to live u ...

s, species that spend their entire lives in subterranean environments. The current status of the invertebrates is difficult to assess because their habitats are largely inaccessible and the animals themselves are small and cryptic. The threats to all species are the same: habitat loss when the caves are filled in or quarried, and habitat degradation via pollution, alterations in water flow, and direct human interference. Some caves are infested with the

red imported fire ant The red imported fire ant (''Solenopsis invicta''), also known as the fire ant or RIFA, is a species of ant native to South America. A member of the genus ''Fire ant, Solenopsis'' in the subfamily Myrmicinae, it was Species description, describ ...

. In August 2012, a spider assigned to this species was found in a 6-foot-deep natural hole in Northwest

San Antonio ("Cradle of Freedom") , image_map = , mapsize = 220px , map_caption = Interactive map of San Antonio , subdivision_type = Country , subdivision_name = United States , subdivision_type1= U.S. state, State , subdivision_name1 = Texas , s ...

, halting completion of a $15-million highway underpass. Biologists have identified at least 19 cave features in the area, at least five of which could contain more.

References

{{Taxonbar, from=Q2049170 Dictynidae Endemic fauna of Texas Bexar County, Texas Cave spiders Spiders of the United States ESA endangered species Spiders described in 1992