The habitat of Cryptocoryne hudoroi Bogner & Jacobsen
Takashige Idei, Osaka, Japan

Summary

Cryptocoryne hudoroi Bogner & Jacobsen has the characteristic bullate, long, narrow leaves, and is found in southern Kalimantan, Indonesia. Even though four localities of Cryptocoryne hudoroi are in Kalimantan Selatan, where the Barito River is the main river system, only one locality is connected as a tributary to the Barito River, i.e. AM-01. The locality for B-07 is in the Sungai Jorong, which has no direct connection with the Barito River. The localities for ME-01 and ME-02 don't have connection with the Barito River either, and flow directly into the Makassar Strait between Borneo and Sulawesi (Celebes).

Furthermore there is collection from a Kahajan River tributary in Kalimantan Tengah by A. Hanreider (Bogner 1989). The localities for AM-01, ME-01, and ME-02 are in the Meratus Mountain Range, but B-07 is in the Kusan Mountain Range which is south of the Meratus Mountain Range.

Cryptocoryne hudoroi belongs to the C. striolata group (including C. keei and C. ideii) with a chromosome number of 2n = 20.

Habitat
The rivers are surrounded by hills or lime stone mountains with great water permeability. The altitude is less than 100 m. The river profile is with a wide and flat riverbed, and the average depth in the middle of the river varies in each locality, and it does not inhabit mountain streams or cascades. In the winding river there are places with both rapid and slow flowing water. The riverbed consists of sand or gravel mixed with soil, and this substrate is often more than 1m deep above the bedrock. The water is generally transparent, but contains soil particles depending on the surrounding ground.

The water level is shallow, often less than 40 cm, and some plants even become emerged during the drier season of the year. High water often occurs after a heavy rain, but the high water usually doesn't last for very long, even though the water may rise to about 70 cm. It is unusual for high water to be over an average of 1 m, even though the general water level of the rainy season is high. Above the river there is partly a canopy cover, which provides some shade; however some degree of direct sunlight seems to be rather necessary for the thriving of the stands. The Cryptocoryne hudoroi habitat is in the not too degraded secondary river environment, in which forests or at least trees to some degree surround the water. It can be found only in a few places, but this is probably not due to the environmental disruption, but the habitat and the niches are limited. It is to be hoped that the present habitats are not destroyed like other Cryptocoryne habitats.

Water condition
The water temperature is normally 25 - 27º C, and in the shallow habitat a change in the water level brings a big change in water temperature, especially in places with stagnant-like water. There is a “period-like” temperature change, depending on humidity and rainfall. Furthermore it depends on the condition of each river, by the canopy, the water depth, and the river environments. There is quite a difference in temperature during the night and the day during the dry period. If there is some water flow in the river, the water temperature shows a tendency of being low and it is up to 28 ºC. However, with very shallow and stagnant-like water the change in water temperature becomes greater in direct sunlight, reaching more than 30 ºC in the day and 25 ºC in the early morning. The pH is more than 7.3, and after rainfall, the elements of the substrate and photosynthesis of the plankton changes rapidly.

Because the habitat consists of mostly gravel-bedrock, the pH becomes lower if there is a seasonal rainfall, and in low water periods the pH becomes higher because of the dissolution of the magnesium and calcium elements. The rapid cascade of water dissolves oxygen and releases CO2; and the conductivity is reduced. Dissolved oxygen is more than 7.0 mg/l, due to properties of the river environment, that doesn't exhaust oxygen and also supplies oxygen. The shallow rapid water supplies oxygen, and there is little erosion in the stone/rock riverbed, and a small biological/chemical oxygen demand as mentioned above.

Caused by the present river environment and the obtained data, it is seen that Cryptocoryne hudoroi is part of a hill stream vegetation in the alkaline environment caused by the environment. The peat stream environment usually has a pH of less than 5.5, with little dissolved oxygen of less than 4.5 mg/l and the quicker running rivers have a greater consumption of oxygen and a biological / chemical oxygen demand of more than 8 mg/l.

Plants
Although the leaf length becomes longer when the plants grow in deep water as it is the case with other Cryptocoryne, C. hudoroi does not inhabit more stagnant water like the C. cordata Griff. group. In the habitat the plant density is usually very high, and the plants are often growing “tightly” together. The leaves are generally narrow, and the width is 10 - 30 % as compared to length in submerged leaves, and most of the individuals have stolons with long internodes of 3 - 6 cm in length, deeply situated in the riverbed. It is characteristic that there are different leaf colours in each locality, but they do not become marmorated and they have bullate leaves under all conditions. It is usual to see iron deposits that stick to the rhizome and root system. Emerged leaves become much smaller than the submerged leaves, and this change caused by the change in water level is quite remarkable. The snail-Family Pleuroceridae spawn their eggs that stick to the plants, and these are often partly eaten and damaged by these snails and aquatic insects. Seedlings have not been found, and the propagation seen no doubt comes from stolons in most cases. The rhizome is situated deeply in the riverbed and many plants have an abundance of “main roots”. There is a “stolon layer” under the “hair root layer” and “main root layer”, buried deeply in the gravel. This stolon-root system serves to stabilize the sand/soil around the plants to extend their growth niches. Spathes

The spathe has different characteristics in the shape and colour in the different localities. Many flower during the low water level period, especially from July to September, and they often flower in submerged specimens at a water depth of 15 cm. The spathe of C. hudoroi is largest in the C. striolata group, being 15 to 30 cm long. The tube colour is cream-brown-purple, and the colour of the limb is also cream-brown-purple, and it is more or less recurved spirally twisted, and these finer details are characteristic for each locality. The fruit diameter is up to 1.2 cm, broader than long (Bogner 1990). However, it may be difficult to find the fruits, as most fruits are situated deeply in the riverbed, and successful fruiting is not common because they are damaged by phytobenthos predation. Furthermore, the fruit stem (pedunculus) has difficulty in expanding at fruit maturation, as they do not become normal round-shaped because of the pressure of gravel and stone obstacles.

Fruit flies of the Family Simuliidae have been found in the kettles of C. hudoroi, the same as in other species of Cryptocoryne.

It may be considered that the uniformity of the spathe colour has relations with the existence/nonexistence of the fruit, i.e. the populations that have some propagation by seed, show a larger variation than those where seed propagation is more rare. The spathe has a stable colour range in AM-01: cream, and ME-01: purple, and fruits have been found in both localities AM-01 and ME- 01.

The area south of Pleihari. Code No. Idei B-07.
The B-07 locality is the southernmost of the C. hudoroi localities, and was originally found by father H. Stroh who brought plants to Germany in 1978, and F. Hudoro provided photographs of the spathes in 1981 and dried material in 1982. Later on also E. Korthaus and A. Hanreider visited the locality (Bogner 1989). In this report, it can be stated that this locality is largest habitat of C. hudoroi, as it inhabits the tributaries of the Sungai Jorong. There are however, limits to these habitats upstream as C. hudoroi grows in the lower meandering riverbeds, with large gravel, some rock boarded riverbed, and somewhat shaded. C. hudoroi cannot grow in the upper mountain streams.

There is mostly arable land around the river and the erosion of soil affects the river. The water is slightly white muddy because of the washing out of soil, and it turns muddy especially after the rains. The river is 6-25 m wide in the parts with direct sunlight, and it has a sand-gravel riverbed. Large stands of plants somewhat emerged appear during low water level periods. It is also during this period that the highest water temperatures are found. Other aquatic plants found in the rivers are Ceratopteris thalictroides (L.) Brongn.

There are many small brownish plants of Cryptocoryne hudoroi along the water edge or in shallow water. The leaf length is 70 cm in large plants, and the narrower leaves are the least bullate and mostly green on the lower side. Black algae, Diatoms, Bacillariophyceae, cover the leaves and petioles, especially on the lower side. Green algae, Cyanophyceae, also stick to the leaves especially in slow running water, and these algae and periphyton often damage the leaves. Individual plants have only few hair-roots, and they have almost only main roots no more than 20 cm deep. In many places there are transitional stands in the riverbed where the rhizomes may reach depths of more than 70 cm.

The spathes from the locality B-07 are around 15 cm long; and vary in the limb and margin colours from cream to brown, and the limb from short to long, and more or less spirally twisted. The throat colours vary from yellow to cream with many “brown-dark red purple” spots. The tube colours from brown to cream.

Water temperature 25 - 29º C, pH 7.3 - 7.8, Conductivity 46-102 μs/cm, DO 7.2 - 7.5 mg/l, COD 3 - 4 mg/l. Research start: 26 May 2003.

North of Sungei Kupang. Code No. Idei ME-01
ME-01 was visited by me in September 2003 after information provided by Suwidji Wongso and Hendra Budianto. The locality is Sungai Mangdao, on the east side of the Meratus Mountain Range in an extensive karst region of this south Kalimantan province. When you see the plants growing, you get a “wild impression”.

The surrounding river environment is secondary forest. The water in the river is mostly rather transparent flowing into the lowland of Kalimantan, slightly sloping from the headwater from a limestone cave, and meandering in the limestone mountains. It is a shallow and flat riverbed in the greater part, and large populations inhabit it all the way from the nearby headwater. The river is mostly 6 - 10 m wide. The riverbed is soft and the substrate is the finest sand grain found in any C. hudoroi locality.

Most of the C. hudoroi ME-01 plants are found in direct sunlight. The other aquatic vegetation, Microsorium pteropus (Bl.)Copel, inhabits places under the canopy part. The majority of the individuals have short internodes, less than 1.5 cm, and generally with “hairroots”; and the whole root system is growing within a depth of 15 cm.

The leaf length is 40 cm at the maximum. There are two different leaf colour types, viz. dark brown on both sides and green on the upper surface and reddish on the lower side with reddish brown veins in some individuals. Both types inhabit different niches/spots, and it does not seem to relate to light conditions. This difference is not with certainty related to special places, although the former often grows in shallow places and the latter is often found in large plants. Characteristics are the purple spathe of 10 - 20 cm; the spathe colour does not correlate with the above-mentioned two leaf type differences, but it is rather stable within the red purple range. The long limb has red purple-cream colours, and is more or less spirally twisted with a creamyellow margin. The throat colours vary from yellow to red purple with many “dark red purple” spots. The tube colour is red purple.

WT 24 - 25º C, pH 8.2 - 8.5, Conductivity 263 - 290 μs/cm, DO 8.1 - 8.5 mg/l, COD 2mg/l, Fe below 0.05 mg/l, Ca 10 - 20 mg/l, Mg 15 - 20 mg/l, Al 0 mg/l. Research start: 23 September 2003.

Mehakit. Code No. Idei ME-02
ME-02 is located north of ME-01; it is also on the east side of the Meratus Mountain Range. The plants give a nice and beautiful impression. The surrounding river environment is shrub and heath forest. This Sungai Magam profile is also slightly sloping from the headwater in a limestone cave. The river is 6 - 8 m wide; and the plants inhabit places in direct sunlight. The substrate is sand and gavel, with transparent water. The point of investigation was downstream with about 2 km to the estuary surrounded by mangrove forest, inhabiting brackish water fish like Valamugil buchanani, V. cunnesius, and Scatophagus argus. However, C. hudoroi ME-02 does not inhabit the brackish water tidal zone, and the habitat is limited to the pure fresh water tidal zone. The leaf length has a maximum of 30 cm; and all individuals have a characteristic light green leaf on both sides. The majority of the individuals have short internodes of less than 1 cm; the whole root system is growing within a depth of 15 cm with horizontal “stolon communities”. It is highest plant population density in any C. hudoroi locality seen. The spathe is more or less 15 cm long, and the majority of the spathes open widely into the throat and tube, and the limb turns backwards flat-like, even in submerged conditions. Such spathe shapes are very rare in other C. hudoroi localities (though this backwards bent limb type is sometimes found in C. cordata group).

It is variable in limb colours from red purple-reddish brown to brown-cream, and the limb is short to long, more or less spirally twisted. The margin is reddish brown-cream-yellow, and the throat colours are yellow to cream with many “brown-dark red purple” spots. The tube colours vary in red purple-reddish brown to brown-cream. WT 24- 25º C, pH 7.9, Conductivity 291 μs/cm, DO 8.9 mg/l, COD 4 mg/l, Fe below 0.05 mg/l, Ca above 50 mg/l, Mg 10 mg/l, Al 0 mg/l. Research start: 20 October 2003.

Kandagan. Code No. Idei AM-01
AM-01 is on the west side of the Meratus Mountain Range, and it is a tributary to the Sungai Barito. The altitude is about 100 m. The plants give a strong impression. They inhabit the lower parts of the mountain stream of Sungai Ahan and this joins to the Sungai Amandit from the point of investigation 100 m downstream. The surrounding river environment has some shifting agriculture on the hillsides. Fish can hardly be seen in the river because of the thoughtless collection by the local people by the use of poisons.

AM-01 is smallest habitat of C. hudoroi, because of the scarcity of suitable habitat niches i.e. shallow and flat riverbed etc. The river is 6 - 8 m wide, and usually carries transparent water that, however, turns somewhat muddy after a heavy rain. The substrate has the largest gravel size of the C. hudoroi localities with some rock boarding the sides, and the habitat has both some shade and some sunlight. Other aquatic vegetation is Hydrilla verticillata (L.f.) Royle.

The leaf length is 60 cm in large plants. The leaves are the most bullate of all the populations, and the majority of the submerged leaves are red on the lower side. The majority of individuals have long internodes up to 6 cm, and there are generally “main roots” to a depth of 40 cm. The rhizome dept in the riverbed is up to 70 cm. Very hard and thick stolons were found in the shallow riverbed layer.

The spathe is at the most 30 cm in this locality. The limb and margin colour is stable cream, and it is the longest with the strongest spirally twisted outer part. The throat colours are reddish purple- cream- light yellow with many “dark brown” spots, and the tube colours are reddish purple-brown. WT 25 - 26ºC. pH 7.6 - 8.0. Conductivity 180-192 μs/cm. DO 7.9 - 8.1 mg/l, COD 2 mg/l. Fe below 0.05 mg/l. Ca below10 mg/l. Mg below 15 mg/l. Al 0 mg/l. Research start: 29 May 2003.

Acknowledgements
This report was written with the cooperation of the friends of the European Cryptocoryne Society (ECS). Professor Niels Jacobsen and Mr. Jan D. Bastmeijer helped me with the correction of the English text and information. Dr. Suwidji Wongso and Mr. Hendra Budianto supplied some of the habitat information, and Hendra Budianto also provided many of the photographs. Then, Dr. Josef Bogner translated it into German. I appreciate everyone with respect.

References

Bogner, J. 1989. Cryptocoryne hudoroi Bogner & Jacobsen – Aqua-Planta 14(1): 12-16.

Bogner, J. 1990. Weitere Angaben zu Cryptocoryne hudoroi Bogner & Jacobsen – Aqua-Planta 15(1): 10-13.