Strombocactus corregidorae

Name and discovery history

Strombocactus corregidorae S.Arias & E.Sánchez was described in 2010 from Infiernillo canyon, in the Moctezuma River system near the Querétaro–Hidalgo border. The differing plants were found in 2008 during activities accompanying construction of the water-supply system for Querétaro. The epithet commemorates Josefa Ortiz de Domínguez, known as the Corregidora de Querétaro. [Arias and Sánchez-Martínez 2010, p. 620–621]

In 2021, the name Chichimecactus corregidorae was proposed, basing genus separation on three chloroplast markers. POWO currently accepts Strombocactus corregidorae and treats the other combination as a synonym. The name Chichimecactus on a label or in a publication therefore refers to the same species under a different classification. [Bárcenas et al. 2021, Bárcenas et al., abstract. POWO, as of 11 October 2026] [2-WWW]

Stem, tubercles and persistent spines

The species description includes young stems that are flattened or broad above and narrowed at the base, and adults that are spherical to long-cylindrical. Adult bodies were 18–23 cm tall and 8–12 cm in diameter, grey-green or bluish green. Tubercles 7–13 mm long and 9–20 mm wide at the base were arranged in 8–13 spiral rows. They were irregularly rhomboid and leathery. [Arias and Sánchez-Martínez 2010, p. 620]

Areoles were around 4.2–4.9 mm long and 2.9–3.1 mm wide. Hairs mainly occurred at young areoles near the tip. One areole produced 3–5 spines 2–3.5 cm long. Upper ones were shorter and thinner, central ones longer, thicker and stiffer. Initially grey, they became greyish black with age. In the plants described, persistent spines covered at least two thirds of the stem. This combination clearly distinguishes the species from S. disciformis, which loses its flexible spines early. [Arias and Sánchez-Martínez 2010, p. 620–621, tabela 1]

Roots and the rocky microhabitat

The root was described as fibrous, with slight thickening near the stem. The entire system remains superficial and spreads sideways. This description is specific to S. corregidorae and differs from the napiform root given for S. disciformis. [Arias and Sánchez-Martínez 2010, p. 620]

The original description concerned three small localities in lower parts of Moctezuma canyon, with type material from around 1500 m above sea level. Plants occupied calcareous shale outcrops, very steep south-facing slopes and vertical walls. The ground was bare or sparsely vegetated. Associated cacti described included Echinocactus platyacanthus and Astrophytum ornatum. The count of three sites comes from the assessment published in 2010. [Arias and Sánchez-Martínez 2010, p. 620–621]

Yellow flowers and a secretory ring

Funnel-shaped flowers were described as 3.5–4 cm long and in diameter. Tepals are pale to intense yellow, with reddish shades on the outer side of some tepals. The yellow throat leads into a zone of numerous stamens. The style projects above the stamens, and the yellow stigma divides into 9–12 lobes. Later observations confirmed daytime flower opening. [Arias and Sánchez-Martínez 2010, Arias and Sánchez-Martínez, p. 620. Camacho-Velázquez et al., p. 102, Fig. 1] [Camacho-Velázquez et al. 2019, Arias and Sánchez-Martínez, p. 620. Camacho-Velázquez et al., p. 102, Fig. 1]

The nectary lies below attachment of the deepest stamens and surrounds the style base. Its epidermis has convex, papillose cells. Secretory parenchyma in the material studied comprised around 7–8 layers, with larger cells associated with vascular bundles deeper inside. Nectar emerges through nectarostomata. The floral features agree with a bee-pollination hypothesis, but effectiveness was not determined in this study. [Camacho-Velázquez et al. 2019, p. 102–104, 106–107, ryc. 2–3, 6]

Fruits and seeds without an aril

Ellipsoidal fruits are 9–11 mm long and 6–7 mm in diameter. While ripening, they are yellowish green, sometimes with a purple tint, becoming pale yellow as they dry. They open through a single longitudinal slit. The brownish-reddish seeds have flat outer seed-coat cell walls and fine reticulate relief. The exposed hilum and micropyle area distinguishes them from seeds of both S. disciformis subspecies. [Arias and Sánchez-Martínez 2010, p. 620–623, tabela 1, ryc. 2]

Developmental analysis showed that no aril-forming appendage develops in the funiculus of S. corregidorae. Seeds remain without this structure, although they have spaces in seed-coat cells. In the 2018 measurement, length was 0.48 ± 0.01 mm and diameter 0.37 ± 0.01 mm. These are means ± standard deviation for 32 seeds, four from each of eight fruits. In distilled water, all seeds in the sample floated at the surface for 25 days. [Camacho-Velázquez et al. 2018, p. 90, 92–94, ryc. 5–7]

Seed production and early development

In material from a natural Querétaro locality, mean ovule number was 1611 ± 481.1, and developed seeds per fruit 838 ± 487.5. Ovule counts in ovaries and seed counts in fruits were determined in seventeen samples. The ratio of these means gave 52.01% use of seed potential. This species therefore produced fewer seeds relative to ovule number than the compared S. disciformis material. The authors considered insufficient pollination, also drawing on observations of less frequent insect visits. They left the cause of this difference to be tested in field experiments. [Camacho-Velázquez et al. 2018, p. 91, 93–94, 100]

Controlled sowing yielded 96.67 ± 4.36% germination. This is the mean ± standard deviation of eight replicates of 30 seeds. Samples remained on moist filter paper at 25°C with a twelve-hour photoperiod for 30 days. Neither scarification nor seed disinfection was used. The emerging radicle opens a lid in the coat, and the hypocotyl then broadens and turns green. The short radicle forms numerous root hairs. The data concern early development and do not determine seedling survival over subsequent seasons. [Camacho-Velázquez et al. 2018, p. 91, 94–95, ryc. 8]

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