Blue Hound's Tongue, Cynoglossum creticum

The Blue Hound's Tongue is a fairly robust, medium to tall, softly hairy biennial. Its stems are angular, erect and branched above. Leaves are oblong to

lanceolate, untoothed, densely hairy, often clasping the stem. Flowers, which are approximately 7 - 9mm (1/4 - 1/3 in), are purplish in bud, but bluish when open, with conspicuous deeper inky-blue or purple net-veins. They are borne in branched cymes, which elongate in fruit. Nutlets, which are 5 - 7mm (1/5 - 1/4 in), have thickened edges and dense, hooked spines. Blue Hound's Tongue spreads by seeds, mature plants each producing several hundred. The seeds have hooks that attach to clothing and hair very easily, so they can be spread long distances attached to people or animals. Because most seeds germinate soon after formation and seed viability is only 2–3 years, there is little development of a soil seedbank. Seedlings are fast growing

A paper by C.F. Asibal, J.A. Glinski, L.T. Gelbaum and L.H. Zalkow, School of Chemistry, Georgia Institute of Technology, entitled "Pyrrolizidine alkaloids from Cynoglossum creticum. Synthesis of the pyrrolizidine alkaloids echinatine, rinderine, and analogues", states that this plant contains various alkaloids, such as echinatine, heliosupine, rinderine, 7-angelylheliotridine and cynoglossamine.

Pyrrolizidine alkaloids (PAs), according to a report published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation, and the World Health Organization, are found in plants growing in most environments and all parts of the world. The main sources are the families Boraginaceae (all genera), Compositae (tribes Senecionae and Eupatoriae), and Leguminosae (genus Crotalaria), and the potential number of alkaloid-containing species is as high as 6,000, or 3% of the worldrs flowering plants (Culvenor, 1980).

They have long been known to be a health hazard for livestock, at least since 1902 (Schoental, 1963), and loss of livestock in various parts of the world has been traced to their grazing on certain plants growing in pastures, especially following periods of drought or in arid climates. They have been found to be toxic for all species of animals tested (Schoental, 1963), though some species, notably the guinea-pig, are resistant (Chesney & Allen, 1973a; White et al., 1973).

Human disease caused by PA toxicity has been known to be endemic in the central Asian republics of the USSR, at least since the early thirties (Ismailov, 1948a,b; Mnushkin, 1949) when several outbreaks occurred, and the cause was discovered to be the seeds of plants of Heliotropium species (Dubrovinskii, 1947, 1952; Khanin, 1948), which contaminated the staple food crops. A spate of reports followed, mostly from the West Indies, of acute and chronic liver disease (Bras et al., 1954, 1961; Bras & Hill, 1956; Stirling et a1., 1962), associated with the ingestion by people of herbal infusions for the treatment of certain ailments. Schoental (1961) and Davidson (1963) suggested that, in view of the evidence of the hepatotoxicity of PAs, consumption of plants containing them could be of etiological significance in human 1iver disease, especially in developing countries.

The "Health and Safety Guide No. 26", a companion volume to the aforesaid report published by the same organizations, states, in respect of the effects of pyrrolizidine alkaloids on human health, that although all age groups are affected, children are particularly vulnerable. The symptoms, which are generally acute in onset, are characterized by upper abdominal discomfort that develops rapidly and progresses to swelling of the abdomen, resulting in increased girth, sometimes accompanied by a reduction in the quantity of urine excreted and swelling of the feet. The disease is called veno-occlusive disease (VOD) because of the characteristic obstruction of the small venous blood channels that carry blood from the liver back to the heart. The disease often progresses rapidly and mortality is high. There may be vomiting of blood in advanced stages of the disease. While many patients recover, the disease may continue for a long time in others resulting in a severely scarred liver - a condition called cirrhosis. Some patients may have only vague symptoms and the only sign of the disease may be persistent enlargement of the liver.

The liver is usually the target organ but, in an epidemic caused by contamination of the staple cereal with the seeds of Trichodesma, the brain and the nervous system were mainly affected.

Chromosome aberrations have been reported in the blood cells of children affected by VOD but, as yet, there is no evidence pointing to an increased incidence of cancer of the liver or other organs or congenital anomalies in the newborn offspring of patients exposed to PAs.

An excellent "Weed Management Guide" on the Blue Hound's Tongue, published by CRC for Australian Weed Management, states that the leaves of the Blue Hound's Tongue contain pyrrolizidine alkaloids that kill cattle and horses. While cattle usually avoid it in the field, the problem occurs when they are fed hay or chopped forage containing the plant. The plant also hinders the establishment of new pasture.

Type of plant
Robust, medium to tall, softly hairy biennial.

Flowering Season
February - June

Known Hazards
Contains pyrrolizidine alkaloids (PAs), which are a known health hazard for livestock and are toxic to humans, mainly affecting the liver.

Known Uses
None known.

Habitat
Cultivated, fallow and waste ground, olive groves, vineyards and roadsides, moist sites by streams and ditches.

Distribution
Throughout the Mediterranean region; has been introduced to various parts of the world, including north and south America, Australia, etc.

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Taxonomy

Kingdom: Plantae (Plants); Subkingdom: Tracheobionta (Vascular plants); Superdivision: Spermatophyta (Seed plants); Division Magnoliophyta (Flowering plants); Class: Magnoliopsida (Dicotyledons); Subclass: Asteridae; Order: Lamiales; Family: Boraginaceae (Borage family); Genus: Cynoglossum; Species: creticum