Hoppers

The world is home to a wide variety of leafhoppers, both in terms of number of species and range of morphological disparity. One of the more diverse leafhopper families is the Delphacidae, including over two thousand species from around the globe. Delphacids are relatively small leafhoppers that are easily distinguished from other families by the possession of a large movable spur at the end of the tibia of the hind leg. I can't say as I know what the function of this spur is, but similar structures in other insect groups may be used for grooming.

Brown leafhoppers Nilaparvata lugens, from ICAR. The individual on the right is a long-winged disperser, the one on the left is a flightless brachypter.

Delphacids feed on the phloem of their host plants; the greater number of species are associated with monocots such as grasses. A number of species are significant economic pests; perhaps the most infamous are the brown leafhopper Nilaparvata lugens and white-backed leafhopper Sogatella furcifera which attack rice. They feed at the base of rice plants, causing the formation of round, yellow patches that soon dry up and turn brown, a condition known as 'hopper burn'. Death of the entire plant will often follow. As well as the direct damage from feeding, these leafhopper species also transmit viruses that further impact yields. Historically, numerous famines have been blamed on leafhopper outbreaks, such as the Kyoho famine of 1732 that saw rice production reduced to only 10% of its previous level. Estimates of the number of people affected by the famine seem to vary widely—according to Wikipedia, the official death toll was a bit more than twelve thousand people, but estimates of the actual number of fatalities range well in excess of 150,000. In more recent years, leafhopper outbreaks may be exacerbated by indiscriminate fertiliser and pesticide use, with the latter reducing competition for the hoppers from other insects or predators.

Delphacids (and many other leafhoppers) commonly exhibit polymorphism in wing development with both flying macropterous and flightless brachypterous forms occuring in a single population. The question of macroptery vs brachyptery is an environmental one. If a developing delphacid receives sufficient nitrogen then it will develop into a flightless adult, remaining in the place of its birth to continue to benefit from the good feeding conditions there. But if feeding conditions become degraded and the developing nymph is deprived of nitrogen then it will develop into a fully-winged adult that can leave its home in search of more favourable conditions elsewhere. Because of their small size, migrating delphacids may be carried long distances by the winds. In the case of pest species, this phenomenon of migration further exacerbates the problem of control as hopper populations from different countries are regularly mixed, increasing genetic diversity and resistance to varying control methods.

REFERENCE

Urban, J. M., C. R. Bartlett & J. R. Cryan. 2010. Evolution of Delphacidae (Hemiptera: Fulgoroidea): combined-evidence phylogenetics reveals importance of grass host shifts. Systematic Entomology 35: 678–691.

When the Wolf Breaks Wind

Common puffballs Lycoperdon perlatum, copyright H. Krisp.

In an earlier post, I described the way in which the 'gasteromycetes' of historical fungal classifications have come to be expunged as a category. The enclosure of spore-producing structures within a contained fruiting body such as a puffball, instead of exposed on a membrane such as on the underside of a mushroom cap, is something that has evolved many times in fungal history. One possible suggestion for why this may occur is as a protection against moisture loss, allowing the fungus to thrive in drier or more exposed habitats than before.

In that earlier post, I also mentioned off-hand that one of the best known groups of 'gasteromycetes', the puffballs of the Lycoperdaceae, are in fact close relatives of some of the best known typical mushrooms in the Agaricaceae. Indeed, it appears that recent authors may go so far as to synonymise the two families. Puffballs emerge as globular fruiting bodies that become packed with spores as they mature, until one or more openings develop in the external skin of the fruiting body and allow the pores to escape. Supposedly many puffballs are quite edible if collected before the spores begin to develop, though I've never tried myself. Particularly sought in this regard is the giant puffball Calvatia gigantea whose fruiting bodies grow particularly large; supposedly, examples have been found over a metre in diameter and weighing up to twenty kilogrammes.

Giant puffball Calvatia gigantea, copyright Alan Wolf.

Dispersal of spores from puffballs may be achieved in a number of ways. In species found in habitats with more regular rainfall, such as species of the genus Lycoperdon, spores are spread by 'boleohydrochory' (Gube & Dörfelt 2011). '-Chory' means dispersal, '-hydro-' obviously means water, 'boleo-' I think may mean something like 'throw'. The puffball opens through a hole in the top, and drops of rain (or other sources of pressure such as being tapped by an animal) cause a puff of spores to be squeezed out. The water may then carry the spores away. The name Lycoperdon, as it happens, literally translates as 'wolf fart', and this is another one of those names I am completely at a loss to explain. The 'fart', obviously, refers to the appearance of the spore puffs, but what on earth do they have to do with wolves?

Tumbling puffballs Bovista pila, copyright Dan Molter.

Other puffballs may spread their spores via 'anemochory', dispersal by wind. This is particularly the case with species found in drier habitats. Some species, such as some members of the genus Bovista, exhibit a variation on this called 'geanemochory' in which the entire puffball becomes detached and blown about by the wind, with the spores escaping through openings in the external shell like pepper being shaken from a pepper-pot. Differences in dispersal method between puffball species are generally reflected by differences in their spore morphology. Hydrochorous species usually have strong ornamentation, with the outside of the spore being covered with warts or the like. These warts provide more surface area for the water to catch onto; they may also help prevent the spores from clumping together. In contrast, anemochorous species have spores that are smooth, making them more streamlined for being blown through the air or, particularly in the case of geanemochorous species, making them less likely to become trapped by hyphae or other structures inside the fruiting body itself and so facilitating their escape.

REFERENCE

Gube, M., & H. Dörfelt. 2011. Gasteromycetation in Agaricaceae s. l. (Basidiomycota): morphological and ecological implementations. Feddes Repertorium 122 (5–6): 367–390.

The Forams that Bind

Cross-section of Fabiania cassis, from BouDagher-Fadel (2008).

Here we see an example of Fabiania. Fabiania is a genus of foraminiferan known from the Eocene epoch that could reach a relatively large size as forams go, up to several millimetres across (nowhere near as large as some that I've covered on this site, maybe, but still respectable). It had a conical test with a rounded apex and a deeply excavated centre; depending on growing conditions, individual Fabiania might be a regular or a flattened cone. In its early stage, Fabiania had two globose thick-walled and perforate chambers; later chambers were cyclical and divided by horizontal and vertical partitions. The aperture of the test was a single row of pores opening into the large umbilicus. The wall of the test was thick and calcareous, and covered with coarse perforations on the upper side of the cone (BouDagher-Fadel 2008; Loeblich & Tappan 1964).

Fabiania lived in association with coral reefs, often preferring the undersides of corals and other sheltered locations. It was primarily found around the mid-depths, not too close to the water's surface but also not too deep (Bosellini & Papazzoni 2003). I've referred in an earlier post to another group of coral-encrusting forams, the acervulinids. Because reef forams tend to be cryptic (in more exposed parts of the reef they tend to get out-competed by coralline algae), and are often variable in morphology making them taxonomically difficult, they tend to be less studied than the reef's more prominent components. However, forams may play a not so insignificant role in developing the reef's structure, helping to bind the reef in place.

REFERENCES

Bosellini, F. R., & C. A. Papazzoni. 2003. Palaeoecological significance of coral-encrusting foraminiferan associations: a case-study from the Upper Eocene of northern Italy. Acta Palaeontologica Polonica 48 (2): 279–292.

BouDagher-Fadel, M. K. 2008. The Cenozoic larger benthic foraminifera: the Palaeogene. Developments in Palaeontology and Stratigraphy 21: 297–418.

Loeblich, A. R., Jr & H. Tappan. 1964. Treatise on Invertebrate Paleontology pt C. Protista 2. Sarcodina, chiefly "thecamoebians" and Foraminiferida vol. 1. The Geological Society of America and The University of Kansas Press.

The European Blackbuck

Horn cores of Gazellospira torticornis hispanica, from here.

From one -spira genus to another, somewhat different one. Gazellospira is a genus of spiral-horned gazelles known from the Pliocene and early Pleistocene of Europe and northern Asia (the reference to Miocene on the Wikipedia page for this genus looks like it might be an error). Most of the known specimens of Gazellospira have been assigned to a single species, G. torticornis, but a second species G. gromovae has been named from the lower Pleistocene of Tadzhikistan. Specimens from the Upper Pliocene of Spain have also been assigned to a distinct subspecies G. torticornis hispanica on the basis of their smaller size than G. torticornis from elsewhere (Garrido 2008).

Gazellospira is a close relative of the modern blackbuck Antilope cervicapra of southern Asia and would have resembled it in overall appearance. The most obvious difference between the two is probably the horns which diverge at a much greater angle in Gazellospira than in the blackbuck (at an eyeball estimate, the angle between the horns in Gazellospira looks to be close to 90° versus closer to 45–60° in Antilope). Like the blackbuck, Gazellospira was probably a more or less mixed feeder, alternating between browsing and grazing as the seasons required.

Gazellospira's eventual extinction was probably connected to the cooling climate of the Pleistocene (the related genus Gazella, which survives to the present in more southerly regions, disappeared from Europe at about the same time). It seems to have been gone from the greater part of Europe by the end of the Pliocene (Crégut-Bonnoure 2007), persisting into the Pleistocene as remnant populations in Iberia, Italy, Greece and central Asia.

REFERENCES

Crégut-Bonnoure, E. 2007. Apport des Caprinae et Antilopinae (Mammalia, Bovidae) à la biostratigraphie du Pliocène terminal et du Pléistocène d’Europe. Quaternaire 18 (1): 73–97.

Garrido, G. 2008. Lu muestra más moderna y completa conocida de Gazellospira torticornis (Bovidae, Artiodactyla, Mammalia en el Plioceno superior terminal de Europa occidental (Fonelas P-1, Cuenca de Guadix, Granada). Cuadernos del Museo Geominero 10: 413–460.

Cochlespira

Shell of Cochlespira radiata, photographed by Jan Delsing.

This beauty is a member of the genus Cochlespira, another one of the conoid shells previously classed as 'turrids' (it now belongs in the family Cochlespiridae since the disassembly of Turridae in the broad sense). Cochlespira species can be relatively large as conoids go, reaching lengths of up to five centimetres. They are found in deep waters in various parts of the world, with a fossil record going back to the Eocene (Powell 1966; Powell treated the western Atlantic species as a separate genus Ancistrosyrinx, but this and the Indo-Pacific Cochlespira have since been synonymised). One of the genus' more distinctive features is a little hard to miss: that eye-catching keel around the outside of the whorls, ornamented with serrations or spines.

As with other deep-water conoids, our knowledge of how Cochlespira species live their lives seems to be pretty limited. The radula has a broad-based central tooth with a single median cusp, and a pair of marginal teeth that are elongate but not as slender as those of many other conoids (Powell 1966). The rhynchodeal walls in the foregut are muscular and the proboscis is long. The venom glands are well-developed but join the oesophagus at about its midlength rather than in the buccal mass (Simone 1999). The arrangement looks to my admittedly inexpert eyes like it might be suited for sucking up invertebrate prey, perhaps something that might be expected to be relatively slow-moving or soft-bodied.

REFERENCES

Powell, A. W. B. 1966. The molluscan families Speightiidae and Turridae. An evaluation of the valid taxa, both recent and fossil, with lists of characteristic species. Bulletin of the Auckland Institute and Museum 5: 1-184.

Simone, L. R. L. 1999. The anatomy of Cochlespira Conrad (Gastropoda, Conoidea, Turridae) with a description of a new species from the southeastern coast of Brazil. Revista Brasileira de Zoologia 16 (1): 103–115.