Monthly Archives: July 2018

The history of Systematics: Plants in Systema Naturae, 1758 (Part 8)

by Piter Kehoma Boll

This is the last part of Linnaeus’ classification of plants dealing with flowering plants (see parts 1, 2, 3, 4, 5, 6 and 7) and presents three classes composed by plants that contain more than one type of flower. The last part of the system (part 9) will deal with non-flowering plants.

21. Monoecia (“single house”)

“Husbands inhabit with women in the same house, but in different bedroom”, i.e., male and female organs occur in the same plant, but in different flowers.

21.1 Monoecia Monandria (“single house, single male”), male flowers having a single stamen: Zannichellia (horned pondweeds), Ceratocarpus (hornfruits), Hippomane (manchineels), Cynomorium (desert thumb).

21.2 Monoecia Diandria (“single house, two males”), male flowers having two stamens: Lemna (duckweeds).

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The horned pondweed (Zannichellia palustris, left), the manchineel tree (Hippomane mancinella, center-left) and the desert thumb (Cynomorium coccineum, center-right) were classified in the order Monoecia Monandria, while the common duckweed (Lemna minor, right) was classified in the order Monoecia Diandria. Credits to Yu Ito (horned pondweed), Hans Hillewaert (manchineel, desert thumb) and Wikimedia user 3268zauber (duckweed).

21.3 Monoecia Triandria (“single house, three males”), male flowers having three stamens: Typha (cattails or bulrushes), Sparganium (bur-reeds), Zea (maize), Tripsacum (gamagrasses), Coix (Job’s tear), Olyra (carrycillo), Carex (true sedges), Axyris (pigweeds), Omphalea (cobnuts), Tragia (noseburns), Hernandia (hernandias), Phyllanthus (chamber bitters, Indian gooseberries and alike).

1758Linnaeus_monoecia_triandria

The order Monoecia Triandria included (from left to right, top to bottom) the common cattail (Typha latifolia), branched bur-reed (Sparganium erectum), maize (Zea mays), eastern gamagrass (Tripsacum dactyloides), Job’s tear (Coix lacryma-jobi), carrycillo (Olyra latifolia), carnation-sedge (Carex panicea), Jamaican cobnut (Omphalea triandra), Indian noseburn (Tragia involucrata) and chamber bitter (Phyllanthus urinaria). Credits to H. Zell (maize), Mason Brock (gamagrass), Alex Popovkin (carrycillo), Kristian Peters (sedge), and Wikimedia users AnRo0002 (cattail), Hugo.arg (bur-reed), Vinayaraj (Job’s tear, Indian noseburn), Carstor (cobnut) and Atsuko-y (chamber bitter).

21.4 Monoecia Tetrandria (“single house, four males”), male flowers with four stamens: Betula (birches and alders), Buxus (box), Urtica (nettles), Morus (mulberry trees).

1758Linnaeus_monoecia_tetrandria

The dwarf birch (Betula nana, left), the common box (Buxus sempervirens, center-left), the common nettle (Urtica dioica, center-right) and the black mulberry tree (Morus nigra, right) were classified in the order Monoecia Tetrandria. Credits to Uwe H. Friese (nettle), Fritz Geller-Grimm (mulberry tree) and Wikimedia users El Grafo (birch) and Abrimaal (box).

21.5 Monoecia Pentandria (“single house, five males”), male flowers with five stamens: Xanthium (cockleburs), Ambrosia (ragweeds), Parthenium (feverfews), Iva (marsh elders), Amarantus (pigweeds).

1758Linnaeus_monoecia_pentandria

The common cocklebur (Xanthium strumarium, left), the common ragweed (Ambrosia artemisiifolia, center-left), the American feverfew (Parthenium integrifolium, center), the annual marsh elder (Iva annua, center-right) and the spiny pigweed (Amaranthus spinosus, right) were part of the order Monoecia Pentandria. Credits to Javier Martin (cocklebur), Meneerke Bloem (ragweed), Krzysztof Ziarnek (feverfew), and Forest & Kim Starr (pigweed).

21.6 Monoecia Hexandria (“single house, six males”), male flowers with six stamens: Zizania (wild rice), Pharus (stalkgrass), Solandra (a species of doubtful identifcation).

21.7 Monoecia Heptandria (“single house, seven males”), male flowers with seven stamens: Guettarda (beach gardenia).

1758Linnaeus_monoecia_hexandria-heptandria

The wild rice (Zizania aquatica, left) and the broadleaf stalkgrass (Pharus latifolius, center) were placed in the order Monoecia Hexandria, while the beach gardenia (Guettarda speciosa) was in the order Monoecia Heptandria. Credits to Michael Wolf (wild rice), Alex Popovkin (stalkgrass) and Cas Liber (beach gardenia).

21.8 Monoecia Polyandria (“single house, many males”), male flowers with many stamens: Ceratophyllum (hornworts), Myriophyllum (watermilfoils), Sagittaria (arrowheads), Theligonum (dog’s cabbage), Poterium (burnets), Quercus (oaks), Juglans (walnut trees), Fagus (beeches and chestnut trees), Carpinus (hornbeams), Corylus (hazels), Platanus (planes), Liquidambar (sweetgums).

1758Linnaeus_monoecia_polyandria

Linnaeus included in the order Monoecia Polyandria (from left to right, top to bottom) the common hornwort (Ceratophyllum demersum), whorl-leaf watermilfoil (Myrophyllum verticillatum), common arrowhead (Sagittaria sagittifolia), common oak (Quercus robur), common walnut tree (Juglans regia), common beech (Fagus sylvatica), common hornbeam (Carpinus betulus), common hazel (Corylus avellana), Eastern plane (Platanus orientalis) and American sweetgum (Liquidambar styraciflua). Credits to Christian Fischer (hornwort, arrowhead), Piotr Panek (watermilfoil), Krzysztof Ziarnek (oak), H. Zell (walnut tree), Franz Xaver (hornbeam), André Karwath (hazel), Dimitar Nàydenov (plane), Kurt Stueber (sweetgum) and Wikimedia user Der Michels (beech).

21.9 Monoecia Monadelpha (“single house, single brothers”), male flowers with stamens fused in a single body by their filaments: Pinus (pines, larches, spruces and firs), Thuja (thujas), Cupressus (cypresses), Acalypha (acalyphas), Croton (crotons), Jatropha (physicnuts), Ricinus (castor oil plants), Sterculia (bastard poon tree), Plukenetia (Inca nut tree), Hura (possumwood).

1758Linnaeus_monoecia_monadelphia

The order Monoecia Monadelpha included (from left to right, top the bottom) the Swiss pine (Pinus cembra), eastern thuja (Thuja occidentalis), Mediterranean cypress (Cupressus sempervirens), Indian acalypha (Acalypha indica), garden croton (Croton variegatus, now Codiaeum variegatum), black physicnut (Jatropha gossypifolia), castor oil plant (Ricinus communis), bastard poon tree (Sterculia foetida), Inca nut (Plukenetia volubilis) and possumwood (Hura crepitans). Credits to Wouter Hagens (thuja), J. M. Garg (acalypha, croton, physicnut), Martina Nolte (castor oil plant), Raju Kasambe (bastard poon tree), Hans Hillewart (possumwood) and Wikimedia users Moroder (pine), Philmarin (cypress) and NusHub (Inca nut).

21.10 Monoecia Syngenesia (“single house, same generation”), male flowers with stamens united forming a cylinder: Trichosanthes (snake gourd), Momordica (bitter melons and luffas), Cucurbita (pumpkins, squashes, calabashes, watermelon), Cucumis (melons, cucumbers), Bryonia (bryonies), Sicyos (bur cucumber).

21.11 Monoecia Gynandria (“single house, female husband”), male flowers with stamens united to the (sterile) pistil: Andrachne (andrachne).

1758Linnaeus_monoecia_syngenesia_gynandria

The order Monoecia Syngenesia included (from left to right) the snake gourd (Trichosanthes cucumerina), bitter melon (Momordica charantia), pumpkin (Cucurbita pepo), cucumber (Cucumis sativus), white bryony (Bryonia alba) and oneseed bur cucumber (Sicyos angulatus), while the order Monoecia Gynandria included the common andrachne (Andrachne telephioides, right). Credits to Florian Wickern (pumpkin), H. Zell (cucumber), Robert H. Mohlenbrock (bur cucumber), Vojtĕch Zavadil (andrachne), flickr user tanakawho (snake gourd) and Wikimedia users Prenn (bitter melon) and Sannse (bryony).

22. Dioecia (“two houses”)

“Husbands and women live in different bedrooms and houses”, i.e., male and female organs occur in different flowers and in different plants.

22.1 Dioecia Monandria (“two houses, single male”), male flowers having a single stamen: Najas (naiads).

22.2 Dioecia Diandria (“two houses, two males”), male flowers having two stamens: Vallisneria (eelgrasses), Cecropia (trumpet tree), Salix (willows).

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The order Dioecia Monandria included a single species, the spiny naiad (Najas marina, left). The order Dioecia Diandria included the common eelgrass (Vallisneria spiralis, center-left), trumpet tree (Cecropia pelatata, center-right) and weeping willow (Salix babylonica, right). Credits to Stefan Lefnaer (naiad), Ori Fragman-Sapir (eelgrass), and Wikimedia users Cmales (trumpet tree) and Viaouest (willow).

22.3 Dioecia Triandria (“two houses, three males”), male flowers having three stamens: Empetrum (crowberries), Osyris (osyris), Excoecaria (blind-your-eye mangrove).

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The black crowberry (Empetrum nigrum, left), osyris (Osyris alba, center) and blind-your-eye mangrove (Excoecaria agallocha, right) were part of the order Dioecia Triandria. Credits to Krzysztof Ziarnek (crowberry), Hans Hillewaert (osyris) and Wikimedia user Vengolis (blind-your-eye mangrove).

22.4 Dioecia Tetrandria (“two houses, four males”), male flowers having four stamens: Trophis (trophis), Batis (beachwort), Viscum (mistletoes), Hippophae (sea buckthorns), Myrica (bog myrtles and wax myrtles).

1758Linnaeus_dioecia_tetrandria

The beachwort (Batis maritima, left), common mistletoe (Viscum album, center-left), common sea buckthorn (Hippophae rhamnoides, center-right) and bog myrtle (Myrica gale, right) made up the order Dioecia Tetrandria. Credits to Forest & Kim Starr (beachwort), Karunakar Rayker (sea buckthorn), Sten Porse (bog myrtle) and Wikimedia user AnRo0002 (mistletoe).

22.5 Dioecia Pentandria (“two houses, five males”), male flowers having five stamens: Pistacia (pistachios and lentiscs), Zanthoxylum (prickly ashes), Ceratonia (carob tree), Iresine (Juba’s bush), Antidesma (heen embilla), Spinacia (spinach), Acnida (water hemp), Cannabis (hemp), Humulus (hop), Zanonia (zanonia), Fevillea (javillo).

1758Linnaeus_dioecia_pentandria

The order Dioecia Pentandria included (from left to right, top to bottom) the pistachio (Pistacia vera), souther prickly ash (Zanthoxylum clava-herculis), carob tree (Ceratonia siliqua), Juba’s bush (Iresine celosia, now Iresine diffusa), spinach (Spinacia oleracea), hemp (Cannabis sativa), the common hop (Humulus lupulus), zanonia (Zanonia indica) and javillo (Fevillea cordifolia). Credits to Franz Xaver (Juba’s bush), Dinesh Valke (hemp), Fritz Geller-Grimm (hop), P. Acevedo (javillo) and Wikimedia users NAEINSUN (pistachio), Rickjpelleg (carob tree), Rasban (spinach) and Vinayaraj (zanonia).

22.6 Dioecia Hexandria (“two houses, six males”), male flowers having six stamens: Tamus (lady’s seal), Smilax (smilaxes), Rajania (rajanias), Dioscorea (true yams).

1758Linnaeus_dioecia_hexandria

Linnaeus included the lady’s seal (Tamus communis, now Dioscorea communis, left), common smilax (Smilax aspera, center) and air yam (Dioscorea bulbifera, right) in the order Dioecia Hexandria. Credits to Alan Fryer (lady’s seal), Carsten Niehaus (smilax) and Dinesh Valke (yam).

22.7 Dioecia Octandria (“two houses, eight males”), male flowers having eight stamens: Populus (aspens and poplars), Rhodiola (golden root).

22.8 Dioecia Enneandria (“two houses, nine males”), male flowers having nine stamens: Mercurialis (mercuries), Hydrocharis (frogbits).

1758Linnaeus_dioecia_octandria-enneandria

The order Dioecia Octandria included the common aspen (Populus tremula, left) and the golden root (Rhodiola rosea, center-left), while the order Dioecia Enneandria included the dog’s mercury (Mercurialis perennis, center-right) and the common frogbit (Hydrocharis morsus-ranae, right). Credits to Wikimedia users AnRo0002 (aspen), Amazonia Exotics U.K (golden root), BerndH (mercury) and Salicyna (frogbit).

22.9 Dioecia Decandria (“two houses, ten males”), male flowers with ten stamens: Carica (papaya tree), Kiggelaria (wild peach), Coriaria (coriarias), Datisca (datiscas).

22.10 Dioecia Polyandria (“two houses, many males”), male flowers with many stamens: Cliffortia (Cliffortias).

1758Linnaeus_dioecia_decandria-polyandria

The order Dioecia Decandria included (from left to right) the papaya tree (Carica papaya), wild peach (Kiggelaria africana), huique (Coriaria ruscifolia) ad Asian datisca (Datisca cannabina), while the prickly cliffortia (Cliffortia ruscifolia, right) was one of the few members of the order Dioecia Polyandria. Credits to Vijayan Rajapuram (papaya tree), Franz Xaver (huique), H. Zell (datisca), and Wikimedia users JMK (wild peach) and Dwergenpaartje (cliffortia).

22.11 Dioecia Monadelphia (“two houses, single brothers”), male flowers with stamens fused in a single body by their filaments: Juniperus (junipers), Taxus (yews), Ephedra (joint pines), Cissampelos (velvetleaf), Adelia (adelias).

1758Linnaeus_dioecia_monadelphia

Among the members of the order Dioecia Monadelphia there were (from left to right) the Phoenician juniper (Juniperus phoenicea), European yew (Taxus baccata), common joint pine (Ephedra distachya) and velvetleaf (Cissampelos pareira). Credits to Isidre Blanc (juniper), Didier Descouens (yew), Dinesh Valke (velvetleaf) and Wikimedia user Le.Loup.Gris (joint pine).

22.12 Dioecia Syngenesia (“two houses, same generation”), male flowers with stamens fused into a cylinder: Ruscus (butcher’s brooms and poet’s laurel).

22.13 Dioecia Gynandria (“two houses, female husband”), male flowers with stamens united to the (sterile) pistil: Clutia (lightning bushes).

1758Linnaeus_dioecia_syngenesia-gynandria

The common butcher’s broom (Ruscus aculeatus, left) was in the order Dioecia Syngenesia, and the common lightning bush (Clutia pulchella, right) was in the order Dioecia Gynandria. Credits to Fritz Geller-Grimm (butcher’s broom) and Wikimedia user JMK (lightning bush).

23. Polygamia (“many marriages”)

“Husbands with wives as well as unmarried ones live together in different bedrooms”, i.e., there are hermaphroditic flowers, as well as male-only or female-only flowers in the same species.

23.1 Polygamia Monoecia (“many marriages, single house”), hermaphrodite flowers occur in the same plant in which male-only or female-only flowers occur: Musa (banana trees), Ophioxylon (devil pepper), Celtis (hackberries), Veratrum (false hellebores), Andropogon (beard grasses, bluestems, spear grasses, lemon grasses, among others), Holcus (soft grasses, fountaingrasses, sorghums, among others), Apluda (Mauritian grass), Ischaemum (murainagrass), Cenchrus (sandspurs), Aegilops (goatgrasses), Valantia (valantias), Parietaria (pellitories), Atriplex (oraches), Dalechampia (dalechampias), Clusia (copeys), Acer (maples), Begonia (begonias), Mimosa (mimosas, shimbilloes, sennas, blackbeads, among others).

1758Linnaeus_polygamia_monoecia

The diverse order Polygamia Monoecia included (from left to right, top to bottom) the banana tree (Musa paradisiaca, currently Musa × paradisiaca, a hybrid), devil pepper (Ophioxylon serpentinum, now Rauvolfia serpentina), Mediterraean hackberry (Celtis australis), white hellebore (Veratrum album, broomsedge bluestem (Andropogon virginicus), creeping soft grass (Holcus mollis), Mauritian grass (Apluda mutica), common murainagrass (Ischaemum aristatum), common sandspur (Cenchrus echinatus), bearded goatgrass (Aegilops triuncialis), wall valantia (Valantia muralis), upright pellitory (Parietaria officinalis), garden orache (Atriplex hortensis), common dalechampia (Dalechampia scandens), lesser copey (Clusia minor), red maple (Acer rubrum), Antillean begonia (Begonia obliqua), and touch-me-not (Mimosa pudica). Credits to Franz Xaver (banana tree), H. Zell (devil pepper), Krish Dulal (hackberry), Hedwig Storch (white hellebore), Harry Rose (bluestem), Krzysztof Ziarnek (soft grass), J. M. Garg Mauritian grass), Javier Martin (goatgrass), Radio Tonreg (pellitory), Stefan Lefnaer (orache), David J. Stang (copey), Yercaud Elango (begonia), flickr user Macleay Grass Man (sandspur) and Wikimedia users Keisotyo (murainagrass), Aroche (valantia), Aniprina (dalechampia), Famartin (maple) and Werner1122 (touch-me-not).

23.2 Polygamia Dioecia (“many marriages, two houses”), hermaphrodite flowers and male-only or female-only flowers occur in different plants: Gleditsia (locusts), Fraxinus (ashes), Diospyros (persimmon trees), Nyssa (tupelo), Anthospermum (anthosperm), Arctopus (bear foot), Pisonia (birdcatcher trees), Panax (ginseng).

1758Linnaeus_polygamia_dioecia

In the order Polygamia Dioecia, Linnaeus included (from left to right, top to bottom) the honey locust (Gleditsia triacanthos), common ash (Fraxinus excelsior), American persimmon (Diospyros virginiana), water tupelo (Nyssa aquatica), bear foot (Arctopus echinatus), thorny birdcatcher tree (Pisonia aculeata) and American ginseng (Panax quinquefolius). Credits to Andrew Butko (locust), Donar Reiskoffer (ash), Dinesh Valke (persimmon), Winfried Bruenken (bear foot), Alex Popvkin (birdcatcher tree), Dan J. Pittillo (ginseng) and Flickr user lucianvenutian (tupelo).

23.3 Polygamia Trioecia (“many marriages, three houses”), there are plants with only male flowers, others with only female flowers and others with both male and female flowers: Ficus (fig trees).

1758Linnaeus_polygamia_trioecia

The order Polygamia Trioecia included only the genus Ficus, with species such as the common fig tree (Ficus carica, left) and the sacred fig tree (Ficus religiosa, right). Credits to Flickr user INRA DIST (common fig tree) and Wikimedia user Amada44 (sacred fig tree).

By classifying all plants with flowers of different sexualities in three classes, Linnaeus made a complete mess. We usually can see at least a vague pattern toward what was later found to be phylogenetically true in some other groups, but it is hard to find anything still relevant today here.

We only need one more part and we will finally finish Linnaeus’ system!

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Reference:

Linnaeus, C. (1758) Systema Naturae per regna tria Naturae…

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Friday Fellow: Wood Cricket

by Piter Kehoma Boll

It is always cool to look at the extravagant, unusual and extreme species of our world, but it is also nice to know about the ordinary small creatures living right around us. So today we are going to talk about an insect found in Western, Central and Southern Europe, as well as Northern Africa, the wood cricket, Nemobius sylvestris.

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A male wood cricket. Photo by Piet Spaans.*

The wood cricket is a small cricket, reaching about 1 cm in length. It is flightless, with males having only a pair of front wings that reach half of the abdomen and females lacking wings entirely. Living in the leaf litter, especially close to the forest edge, the wood cricket feeds on decaying plant matter and fungi growing on it.

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A wingless female wood cricket. Photo by Gilles San Martin.**

During the mating season, male wood crickets attract females by stridulation (“singing”) and then present them with a spermatophore, i.e., a sperm-filled sack, which they attach to the female genital opening. Sometimes, before transfering the large spermatophore (called macrospermatophore) to the female, the male transfers a smaller spermatophore (called microspermatophore) that lacks sperm. The female eats the microspermatophore and then accepts the macrospermatophore, eating it too some minutes after having it attached to it. The male usually pursues the female, sometimes pushing her with his head, apparently to prevent her from eating the spermatophore too soon, as it would reduce the chances of fertilization.

Females really seem to like eating spermatophores. Sometimes they also “lick” the male wings while they mate, as if thinking “that looks delicious”. Kind of creepy, right?

Despite being a common species in Europe, the wood cricket is rare in the United Kingdom, with only a few isolated populations known. As a result, it is considered a species of conservation concern in this country, a status that invertebrates rarely attain in the world, unfortunately.

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References:

Brouwers, N. C.; Newton, A. C. (2009) Habitat requirements for the conservation of wood cricket (Nemobius sylvestris) (Orthoptera: Gryllidae) on the Isle of Wight, UKJournal of Insect Conservation13(5): 529–541.

Brouwers, N. C.; Newton, A. C. (2010) Movement analyses of wood cricket (Nemobius sylvestris) (Orthoptera: Gryllidae)Bulletin of Entomological Research (2010) 100, 623–634.

Prokop, P.; Maxwell, M. R. (2008) Interactions Between Multiple Forms of Nuptial Feeding in the Wood Cricket Nemobius sylvestris (Bosc): Dual Spermatophores and Male ForewingsEthology 114: 1173–1182.

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Friday Fellow: Titan Arum

by Piter Kehoma Boll

Today our fellow is another star of the plant kingdom and you probably heard of it before. Growing in the rainforests of Sumatra and Java, this species has a giant inflorescence and emits a smell of rotten meat, sometimes being called corpse flower, but do not mistake it for another rotten meat-smelling giant flower from the same place, the corpse flower Rafflesia arnoldi already presented here some years ago.

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The giant inflorescence of the titan arum. Photo by Wikimedia user Rhododendrites.*

The name of today’s species if Amorphophallus titanum, which literally means something like “titan shapeless penis”. The name may not please many audiences, so the common name “titan arum” was coined by the British naturalist and broadcaster David Attenborough.

The titan arum belongs to the family Araceae, the same that includes some popular garden plants such as the anthurium. It is the flowering plant with the largest unbranched inflorescence in the world. The giant structure is not a single flower, but a giant inflorescence, called spadix, containing many small flowers and surrounded by a single petal-like leaf called spathe. In most species of Araceae the whole spadix contains flowers, but in the titan arum they are present only at two rings at the base, an upper ring of male flowers and a lower ling of female flowers. Most of the spadix is just a giant hollow appendix.

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Male flowers (above) and female flowers (below) seen through a cut of the spathe. Photo by Wikimedia user Rosetta.**

The inflorescence of the titan arum can reach over 3 meters in height. It emits a fragrance that resembles that of rotting meat and attracts the pollinators, which are carrion-eating beetles and flesh flies. In fact, the odor changes during the opening and maturation of the inflorescence, but always resembles something decomposing. While the spathe is opening, the smell is more like that of rotten fruits, a few hours later it changes to a more rotten-egg smell and then to a real rotting-meat smell. During this last phase, the temperature of the inflorescence increases, reaching up to 36°C, about the temperature of a mammal, and this is considered as a probable additional feature to simulate the rotting meat appearance of the structure. Furthermore, the inner surface of the spathe has a deep-red to purple color that also resembles rotting meat.

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The single giant leaf of the titan arum. Photo by Emőke Dénes.*

Like many giant-flowered or giant-inflorescenced species, the titan arum is not a very leafy species. While the inflorescence is growing and opening, the plants does not have any leaf. After the inflorescence dies and fruits are produced, a single giant leaf starts to grow from the plants subterranean corm (a stem working as a storage organ), reaching the size of a small tree. The corm, as everything in this species, is also giant, being the largest known corm in the world, usually reaching aroound 50 kg, but some specimens in botanical gardens going beyond 100 kg after some years.

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The giant corm of the titan arum. Photo by Wikimedia user Georgialh.*

The titan arum is really one of the most remarkable species on our planet. Don’t you agree?

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References:

Korotkova, N.; Barthlott, W. (2009) On the thermogenesis of the Titan arum (Amorphophallus titanum). Plant Signaling & Behavior, 4(11): 1096–1098.

Shirasu, M.; Fujioka, K.; Kakishima, S.; Nagai, S.; Tomizawa, Y.; Tsukaya, H.; Murata, J.; Manome, Y.; Touhara, K. (2010) Chemical identity of a rotting animal-like odor emitted from the inflorescence of the titan arum (Amorphophallus titanum). Bioscience, Biotechnology and Biochemistry 74(12): 2550–2554.

Wikipedia. Amorphophallus titanum. Available at < https://en.wikipedia.org/wiki/Amorphophallus_titanum >. Access on June 14, 2018.

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Having few females turns male tortoises into rapists

by Piter Kehoma Boll

The war between the sexes and the endless conflicts that result from that are a common theme in behavioral and evolutionary research and have been addressed several times here too.

As we know very well, even from examples in our own species, males are usually not very good parents, being more interested in producing as many descendants as possible with little effort. Females, on the other hand, due to their great investment on eggs (and usually other resources for the offspring) are much more selective and will not accept any male to mate with them.

One of the most common solutions for males to resolve this sexual conflict is by forced copulation, or rape as it is called when it happens in our own species. Sometimes this forced copulation is extreme, with males heavily injuring females in order to make them surrender. One of those violent species is the Hermann’s tortoise, Testudo hermanni, a tortoise found around the Mediterranean areas of Europe.

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“I’m gonna bang you, bitch!” This photo of a juvenile male trying to mount on an adult female may look funny, but sex is no fun for female tortoises. Photo by Wikimedia user Palauenc05.*

Forced copulation is much more common in species in which males are bigger and stronger than females. This is not the case with tortoises, but male Hermann’s tortoises have found a way to deal with that. They pursue the females, sometimes for hours, pushing them, biting them, sometimes to the point of making them bleed, and eventually the poor females surrender. It is also common for the males to “stimulate” the cloaca of the females with their pointed tail, resulting in a swollen cloaca and sometimes severe injuries that let the females with horrible scars and deformities. Yes, it is not a nice face of nature.

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The tail of a male. Photo by Wikimedia user Bizarria.**

A recent study with two populations of the Hermann’s tortoise in Macedonia revealed that male aggressiveness is linked to female availability. The team of researchers studied one population in which the female:male ratio was close to 1:1 and other in which it was extremely male-biased to the point of 1 female to 17.5 males.

The results indicate that in the more balanced population forced copulation was less common and usually only adult females presented injuries caused by males, while in the male-biased population the lack of females made males go mad to the point that they forced copulation even with immature females. The situation as a whole is clearly maladaptive, as females end up injured and males end up exhausted and no offspring is generated.

I can only see two possible outcomes for such a population: either more resistant females will be selected or the population will go extinct after all females die by male violence.

As we see, sexual conflict is one of those deleterious side effects that natural selection created. Afterall, nobody is perfect, not even the fundamental laws of life.

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You may also like:

Male dragonflies are not as violent as thought

Gender conflict: Who’s the man in the relationship?

Badass females are unpopular among praying mantids

Having more females makes you gayer… if you are a beetle

Male resistance: when females disappear and hermaphrodites don’t like you

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Reference:

Golubović, A.; Arsovski, D.; Tomović, L.; Bonnet, X. (2018) Is sexual brutality maladaptive under high population density? Biological Journal of the Linnean Society 124(3): 394–402. https://doi.org/10.1093/biolinnean/bly057

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Filed under Behavior, Evolution, Zoology

Friday Fellow: Truncate Trapdoor Spider

by Piter Kehoma Boll

Today I’m bringing you a species that fascinates me and that I was willing to introduce for a while. Unfortunately, there isn’t much information available about it, that being the reason for my delay in showing it here. However, as new information seems unlikely to appear soon, I can only show it with whatever is avaible.

Named Cyclocosmia truncata, today’s fellow is a trapdoor spider found in the East of the United States and sometimes referred to as truncate trapdoor spider. As all trapdoor spiders, it is a mygalomorph spider, such as tarantulas, and lives in a tunnel that it burrows in the ground and that is covered by a trapdoor. Trapdoor spiders in general rarely leave their burrows and hunt prey at night by standing behind the closed trapdoor and waiting for a prey to pass nearby, then jumping out and capturing it.

A truncate trapdoor spider in southeastern United States. Photo by iNaturalist user jimstarrett.*

Because trapdoor spiders are highly sedentary, they are very vulnerable to predators and parasites that can easily find them by locating their burrows. Species in the genus Cyclocosma have developed a fascinating morphological adaptation to cope with that. Their abdomen is abruptly truncated, giving the impression that someone just cut half of the abdomen off. This region of the abdomen is covered by a heavily sclerotized disc. When the spider is not active, it enters its burrow head first and the sclerotized disc fits perfectly to the walls of the tunnel, forming a false bottom that is impenetrable.

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A nice view of the peculiar disc of Cyclocosmia truncata. Author unknown. Photo taken from imgur.com

Not much more is known about the truncate trapdoor spider or its close relatives. They seem to be considerably rare, living in very restrict habitats, and their burrows are so well hidden that it is hard to find them in the wild.

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References:

Gertsch, W. J.; Platnick, N. I. (1975) A revision of the trapdoor spider genus Cyclocosmia (Aranae, Ctenizidae). American Museum Novitates 2580: 1–20.

Hunt, R. H. 1976. Notes on the ecology of Cyclocosmia truncata (Aranae, Ctenizidae) in Georgia. Journal of Arachnology 3: 83–86.

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Filed under Arachnids, Friday Fellow, Zoology