Field of Science

Jewels among Beetles

There are many contenders for the title of most stunning-looking insect but there is no question that the jewel beetles have a place among the line-up. Some of these brilliantly coloured insects look as if they could have been sculpted from gleaming metal:

Buprestis niponica, copyright Kohichiro Yoshida.


Buprestis is a genus of jewel beetles found in the Holarctic region, with the greater diversity around the Mediterranean and North America. Somewhere between forty and eighty species are recognised, depending on whether the closely related genera Cypriacis and Yamina are regarded as distinct or not. Species of Buprestis come in a variety of colours, with green, blue or black backgrounds often patterned with yellow or red.

Female Buprestis octoguttata ovipositing, copyright Christian Fischer.


Despite their attractive appearance, jewel beetles are not always welcome. They spend the larval part of their life cycle burrowing into wood so some are known for damaging timbers. The preferred hosts of most Buprestis species, where known, appear to be conifers such as pine, spruce and larch. They primarily attack dead and dying wood, and females of some species are known for searching the trunks of trees following fires to find where protective bark has cracked open (some jewel beetle species in other genera are commonly known as 'fire beetles' in reference to this habit). Buprestis larvae have been claimed to live for extraordinarily long periods. Mature beetles have been observed emerging from furniture and the like multiple decades after the original tree was felled, leading to claims of larval life spans of up to 51 years! It almost goes without saying that such inferences have attracted their share of scepticism, with detractors suggesting the possibility of eggs being laid after the wood was already worked. It is true that the low nutritious value of dry wood might be expected to lead to slow development, but how slow are you willing to believe?

Hairy-Winged Barklice

Forewing and fore tibia of Siniamphipsocus fusconervosus, from Mockford (2003). Scale bar for the femur = 0.1 mm.


For my next semi-random post, I drew Siniamphipsocus, a genus of more than twenty species of barklice known from eastern Asia. Most of these species were described by China by the almost ludicrously prolific psocopterologist Li Fasheng who over the course of his career has described close to 1000 psocopteran species—nearly a fifth of the world's barklouse fauna. It should be noted, though, that this productivity has not entirely come without criticism: for instance, in the case of the Siniamphipsocus species, most if not all are known from a single sex with some described from males and others from females (Li 2002).

Siniamphipsocus is a genus of the Amphipsocidae, a family of barklice most easily recognised by their wings which have a double row of setae along each of the veins. Amphipsocids can be relatively large as barklice go: the largest Siniamphipsocus species, S. aureus, has a body length of four millimetres, with the forewings being up to 6.75 millimetres long. Features distinguishing Siniamphipsocus from other amphipsocids include the absence of the brush of hairs present at the base of the hind wing in many other species, the absence of a spur vein in the rear of the forewing pterostigma, and the presence of a row of minute spines along the fore femur (Li 2002). Distinguishing the individual species of the genus requires fine attention to details such the patterns of markings on the face, the proportions of the wing veins, and details of the genitalia.

REFERENCES

Li F. 2002. Psocoptera of China (2 vols). Science Press: Beijing.

Mockford, E. L. 2003. New species and records of Psocoptera from the Kuril Islands. Deutsche Entomologische Zeitschrift 50 (2): 191–230.

Sordariomycetidae: Soil Fungi A-Plenty

I'm pretty sure I've commented before that, although most of us tend to associate the word 'fungi' with mushrooms and other eye-catching fruiting bodies, the vast majority of fungal diversity is minute and tends to go unnoticed. Nevertheless, despite their obscurity, many of these microfungi are crucial to our own continued existence. These are the decomposers, the organisms that break down fallen plant matter and animal wastes in their own search for nourishment and so contribute to the release of locked-up nutrients back into the environmental cycle.

Neurospora growing on sugar cane waste, from here.


The group of fungi that I drew for today's post, the Sordariomycetidae, is primarily made up of these minute decomposers. Sordariomycetids have already made an appearance here at Catalogue of Organisms, in a post from ten years ago on black mildews. Depending on how broadly the group is circumscribed, the Diaporthales could also be included. Due to a simple morphology that provides few distinct characters, the Sordariomycetidae are primarily defined on the basis of molecular phylogenies. The difficulty of classifying microfungi by morphology alone is underlined by cases where species previously classified within the same genus have proven to belong to entirely distinct fungal lineages.

In general, the vegetative body of most Sordariomycetidae consists of little more than disassociated hyphae embedded in their substrate, with the only distinct structures being the reproductive fruiting bodies. These are perithecia: that is, globular or flask-shaped fruiting bodies with a single small opening or ostiole at the top through which the mature spores are released. In some cases, the internal structure of the mature perithecium will simply dissolve, freeing the spores to escape through the ostiole in the manner of a miniature puffball. In others, the spores become entangled in a long strand or seta that is then extruded through the ostiole like toothpaste being squeezed out of a tube.

Perithecium of Chaetomium extruding spore-bearing setae, from here.


Sordariomycetids are found in almost every habitat imaginable: as well as soil- and dung-dwelling forms, they may also be found in aquatic and even marine habitats. Perhaps the best-known sordariomycetid is Neurospora crassa, red bread mould, which is widely used in laboratories as a model organism for genetic research. Indeed, it was investigations into N. crassa in the 1950s that first led to the proposal of the 'one gene, one enzyme' model that became a cornerstone of molecular genetics.

A Western Rockweed

Rockweed Silvetia compressa, from here.


Silvetia compressa is a species of brown alga found on shorelines on the western coast of North America, from British Columbia to Baja California. It is a member of the wrack family Fucaceae that I covered in an earlier post. Silvetia compressa is found in midtidal habitats, generally higher up on the shoreline than other large seaweeds. Individual thalli can reach a maximum length of about three feet (90 cm) but are often smaller. This is a slow-growing species, so patches of Silvetia are slow to recover from damage due to trampling and other disturbance. Please try to avoid walking on the rockweed!

Thalli of Silvetia compressa are composed of thin strands a few millinetres in width with irregular, dichotomous branching. Strands of the thalli lack a midrib (distinguishing them from some other Fucaceae species found in the same area). The width of the strands and regularity of the branching varies with environmental conditions: for instance, individuals growing in locations with stronger wave action have more robust strands that branch more frequently. As with other Fucaceae, the reproductive structures a produced on swollen branch tips called receptacles, but these receptacles do not become inflated with gases and buoyant like those of other species. The exact size and shape of the receptacles is, again, variable.

In many older references, Silvetia compressa may be referred to as Pelvetia fastigiata. The supposed species 'Fucodium compressum' and 'F. fastigiatum' were originally distinguished on the basis that the latter was smaller than the former with more fastigiate branches (that is, the branches remained subparallel). As indicated above, these characters represent the effects of environmental conditions, not fixed differences (Silva 1996). They were eventually included in the genus Pelvetia, together with the Atlantic species P. canaliculata, on the basis of the thalli without a midrib, and the production of just two eggs from each oogonium in the receptacles. However, later analyses supported the separation of the Atlantic and Pacific species of Pelvetia. Not only did they not form a clade in molecular analyses, the eggs in the oogonia were separated by a horizontal division in the Atlantic species but a longitudinal or oblique division in the Pacific species (Silva et al. 2004). As such, the Pacific Pelvetia were transferred into a new genus Silvetia.

Further taxonomic complications involved subspecific variation in Silvetia compressa. A distinctive form of 'Pelvetia fastigiata' found at Pebble Beach in California's Monterey Bay, with smaller, finer thalli and more abundant, regular branching, was labelled as a separate forma gracilis. Similar individuals were also found on the islands off California's coast. However, when Silva (1996) examined the original type specimen of P. fastigiata, he discovered that it was an individual of this 'gracilis' form, not the more typical larger form. Later, Silva et al. (2004) examined genetic variation within the Silvetia compressa of California and Baja California. They found that the individuals of the offshore islands were indeed genetically distinct from continental individuals. As well as the differences in growth habit, there was also some difference in receptacle shape: the continental form had receptacles that tended to be linear and pointed whereas those of the island form were ellipsoidal and blunt. However, the island form still could not be labelled with either of the 'fastigiata' or 'gracilis' monikers, as individuals from the type locality of Pebble Beach did not align genetically with insular individuals but with other continental forms. As such, yet another name had to be coined for the insular form which now goes by the name of Silvetia compressa ssp. deliquescens. Let's see if it sticks this time.

REFERENCES

Silva, P. C. 1996. California seaweeds collected by the Malaspina expedition, especially Pelvetia (Fucales, Phaeophyceae). Madroño 43 (3): 345–354.

Silva, P. C., F. F. Pedroche, M. E. Chacana, R. Aguilar-Rosa, L. E. Aguilar-Rosa & J. Raum. 2004. Geographic correlation of morphological and molecular variation in Silvetia compressa (Fucaceae, Fucales, Phaeophyceae). Phycologia 43 (2): 204–214.

The Millenium Post

Apparently, this is the 1000th post to appear at Catalogue of Organisms. When I first started this site, over ten years ago, I don't know if I had any idea when, if ever, I would reach this point and where I would be when it happened. I probably imagined I would be thinner.

I want to thank everyone that has followed Catalogue of Organisms over the years. I particularly want to thank those readers who have supported me on Patreon: Paul Selden, Sebastian Marquez, Rob Partington, William Holz. Your contributions have meant a lot to me. Apropos of that, some news: some of my readers may recall that my employment status has been a little up in the air for a large chunk of the last couple of years (though I was able to find casual positions for some of that time). A few months ago, though, an opportunity came up to work on a project looking at insect diversity in mangroves in Hong Kong. Though it means being away from my home, my partner and my dog for a couple of years, the opportunity was too good to pass up and for the next little while I'll be based in the city of the Fragrant Harbour (especially around the port district in high summer).

So on to the next 1000 posts, then? We'll just have to see. Certainly I'm not putting stuff up here as frequently as I did in the past, when I was a carefree post-graduate student. There have been times when I've wondered if I should keep going. People far more talented and perspicacious than I have had a great deal to say elsewhere about the apparent decline of science blogging as a format, and it certainly doesn't seem to attract the audience it once did. Nevertheless, I think I'll be going for a while yet. I've noted before that this blog functions as my own means and motivation for investigating things that I might find interesting, and there's certainly no shortage of things left to investigate. And as for the health of science blogging overall: a glance to the sidebar to the right of this page reminds me that there's still a lot out there worth following. There's Deep Sea News, there's Small Things Considered, Bug Eric, Tetrapod Zoology, Letters from Gondwana, Synapsida, Beetles in the Bush, and so many more. If you don't already know these sites, check them out!

For my part, the main indicator I see as to whether people are reading anything here is when people leave comments. A big thank you again to those who have contributed over the years. I'm needy, and need validation... And in that light, I'd like to specially ask my readers to comment on their general feelings (if any) about Catalogue of Organisms. Has there been anything you've particularly liked about the site over the years? Any favourite posts? Anything you'd like to see going forward? And once again...

The Shrinking World of Bandicoots

A bandicoot is a very disagreeable animal to clean, therefore it should be done as soon after killing as possible, and then the flesh can be left in strong vinegar and water for a few hours before dressing. Sweet potatoes and onion make a good stuffing for bandicoot, which is good either boiled or baked.--Mrs Lance Rawson, Australian Enquiry Book of Household and General Information.


Golden bandicoots Isoodon auratus barrowensis, copyright Kathie Atkinson.


Back when I used to work on Barrow Island in the north-west of Australia, one of the more noticeable animals to be seen around the place was the golden bandicoot Isoodon auratus. In the evenings, the place seemed to absolutely swarm with them. About the size of a guinea pig, with no tails to speak of (bandicoots are actually born with fairly long tails but tend to lose them in the course of their quite vicious fights with one another; few if any individuals reach maturity with their tails intact), there was no question about their qualifications when it came to cuteness.

Bandicoots are a group of twenty-odd species of marsupial found in Australia and New Guinea (one species, the Seram bandicoot Rhynchomeles prattorum, was described from montane forest on the Indonesian island of Seram to the west of New Guinea). Most are primarily insectivorous, but they also eat varying amounts of small vertebrates and plant matter such as bulbs and fruit. The largest bandicoot, the giant bandicoot Peroryctes broadbenti, has been recorded to reach close to five kilograms in weight. The smallest, the Papuan bandicoot Microperoryctes papuensis, weighs less than 200 grams. I suspect many people in Australia assume that the name 'bandicoot' comes from one of the the Aboriginal languages, but it is in fact Indian (specifically Telugu) in origin. The original bandicoot Bandicota indica is a large rat that is widespread in southern Asia and Australian bandicoots were named for their resemblance to this species. Personally, I have maintained in the past that Australian bandicoots look more like rats than rats do: with their relatively long snouts, bandicoots bear a distinct resemblance to the sort of cartoon figure that comes to most people's minds when they hear the word 'rat'.

New Guinea spiny bandicoot Echymipera kalubu, copyright Michael Pennay.


Bandicoots are highly distinctive from all other marsupials in appearance. Their hind legs are noticeably longer than their forelegs and more or less specialised for cursorial locomotion (especially so in one example that I'll get to shortly). The fourth and fifth toes of the hind foot are much larger than the other three; the first toe in particular is reduced to a non-functional stub. The second and third toes of the hind foot, as in diprotodontian marsupials such as kangaroos and possums, are externally joined together with the two claws at the end forming a comb that is used in grooming more than in locomotion. The fore feet, in contrast, are mostly functionally three-fingered (with the first and fifth fingers reduced) and adapted for digging with the claws large and flat.

Many bandicoots are rapid reproducers with their gestation periods among the shortest of any mammal, less than two weeks between fertilisation and birth. Bandicoots also have the most developed placentas of any marsupial group (yes, most marsupials do have a placenta, albeit a much simpler one than found in placental mammals); it is presumably because of this that, despite their short gestation, bandicoot young are born at a more advanced stage of development than those of some other marsupials. When the young are born, they initially remain attached to their mother via the umbilical cord; this latter does not become detached and the placenta ejected until after the joey is firmly attached to a teat in the rearward-opening pouch. The young remain in the pouch for about two months and grow rapidly; they may reach full sexual maturity at the age of only three months. As a result, bandicoot populations may increase rapidly if conditions permit.

Greater bilby Macrotis lagotis, copyright Bernard Dupont.


In terms of classification, there is a general consensus that Recent bandicoots can be divided between four groups though there has been some disagreement about exactly these groups are interrelated (and hence exactly how they should be ranked). The most diverse, but probably also the least studied, group of modern bandicoots are the rainforest bandicoots of the Peroryctidae or Peroryctinae. These are about a dozen species found mostly in New Guinea with the aforementioned Rhynchomeles prattorum on Seram and the the long-nosed spiny bandicoot Echymipera rufescens extending its range to the northern tip of Queensland. Most of continental Australia is home to the dry-country bandicoots of the Peramelidae sensu stricto or Peramelinae, of which there are six Recent species (one of these, the northern brown bandicoot Isoodon macrourus, is also found in southern New Guinea). Peramelids tend to have shorter snouts and flatter skulls than peroryctids. The other two groups are both very small and also native to arid regions of Australia. Two Recent species are known of the genus Macrotis, the bilbies, though one of these is extinct and the other is endangered. Bilbies are larger than most other bandicoots, with long ears (hence their alternative vernacular name of 'rabbit-bandicoots') and a long, silky-haired tail.

Gerard Krefft's 1857 illustration of the pig-footed bandicoot Chaeropus ecaudatus, from here.


The final representative of the Recent bandicoots is unquestionably the weirdest of them all. Unfortunately, it is also now extinct, last recorded some time about the middle of the 20th Century, a fact that cannot be called anything less than a fucking tragedy. The pig-footed bandicoot Chaeropus ecaudatus was the most cursorial of all bandicoots. Its forelegs, rather than being adapted for digging as in other bandicoots, had only two functional toes on which the claws were modified into hooves. The hind legs went a step further and had only a single functional toe (raising the question of how this animal groomed itself without the aforementioned claw-comb of other bandicoots Edit: That was a bit of a blonde moment; a second look at the Krefft illustration above shows that the comb is definitely there). The most extensive observations of its habits seem to have been made by Gerard Krefft (1866) who kept a pair alive for about six weeks in 1857 on a trip to the Murray-Darling region before killing them to provide specimens because, you know, 19th-Century naturalist. Krefft recorded that his bandicoots subsisted primarily on plant foods such as lettuce, grass and roots, refusing all meat offered to them (Krefft also refers to providing grasshoppers for them but his account is unclear about whether they were ever eaten). A herbivorous diet was also indicated by the animals' droppings, which where dry and similar to a sheep's. The bandicoots constructed a covered nest from grass and leaves in the tin enclosure in which Krefft kept them in which they sheltered during the day, only becoming active after nightfall. Krefft notes that he acquired "about eight" specimens of pig-footed bandicoot during his six-month camp, admitting that some met a stickier end than others: "They are very good eating, and I am sorry to confess that my appetite more than once over-ruled my love for science; but 24 hours upon "pig-face" (mesembryanthemum) will dampen the ardour of any naturalist". Krefft also noted that several of the specimens found were female, and that despite being provided with eight teats the females never carried more than two joeys. A particularly interesting detail was that the fourth toe of the joeys' fore foot, rather than being reduced as in the adults, remained large so that the feet resembled those of other bandicoots. Presumably this was so that the fore-claws could still be used to allow the newborn joeys to climb from the birth canal to the pouch.

Krefft also noted that the pig-footed bandicoot was already declining in abundance, blaming its increased rarity on competition with introduced grazing livestock. Sadly, changing habitats and introduced predators have caused other bandicoot species to also become endangered since Krefft's time. Please, don't let them go the way of the pig-footed bandicoot.

REFERENCES

Gordon, G., & a. J. Hulbert. 1989. Peramelidae. In: Fauna of Australia vol. 1B. Mammalia. Australian Biological Resources Study: Canberra.

Krefft, G. 1866. On the vertebrated animals of the lower Murray and Darling, their habits, economy, and geographical distribution. Transactions of the Philosophical Society of New South Wales 1862–1865: 1–33.

A Second Look at Scallops

In a post that appeared at this site over eight years ago, I described some of the distinctive features of the Pectinoidea, the group of bivalves commonly known as scallops. It's time to look in a bit more detail at some of the points mentioned in that post.

Fossil of Pernopecten, the earliest scallop genus, from ammonit.ru.


Pectinoidea, in the sense recognised by Waller (2006), first appear in the fossil record way back in the late Devonian. They were probably derived from earlier members of the Aviculopectinoidea, an extinct group of bivalves that closely resemble scallops in their overall appearance and were included in the Pectinoidea by many earlier authors (such as in the 1969 Treatise on Invertebrate Paleontology volume on bivalves). However, the shell ligament of aviculopectinoids was reinforced by aragonite fibres (a primitive feature for bivalves) rather than having the specialised rubbery core found in pectinoids. As such, aviculopectinoids would have lacked the swimming abilities of true scallops. The Palaeozoic pectinoids belong to a single genus, Pernopecten, that possesses a number of features such as details of the shell crystalline structure that indicate a position outside the pectinoid crown group. In the early Triassic, Pernopecten begat the family Entolioididae that includes the ancestors of living pectinoids.

As mentioned in the previous post, four pectinoid families survive to the present day: the Pectinidae, Propeamussiidae, Entoliidae and Spondylidae. The first three families diverged in the early Triassic. Spondylids (usually classified in a single genus, Spondylus) were not to appear until the mid-Jurassic and Waller (2006) argued for their derivation from within the Pectinidae. The Pectinidae are otherwise distinguished from other pectinoids by a structure called the ctenolium. This is a row of teeth that develops on the shell in the gap between the disc and one of the auricles (the triangular 'wings' at the top of the shell). During the earlier part of the scallop's life, when it lives attached to the ocean bottom by a byssus (what in mussels we call the 'beard'), the ctenolium functions to hold the byssus threads in place and help stop the shell from twisting. In those pectinid species that lack a byssus in the latter part of their life, the ctenolium may end up getting overgrown by the expanding shell and disappearing, but all pectinids (ignoring the aforementioned Spondylus question) have a ctenolium for at least part of their life.

The propeamussiid Cyclopecten secundus, copyright Museum of New Zealand Te Papa Tongarewa.


The Pectinidae is the largest scallop family in the present day, followed by the Propeamussiidae. The Entoliidae were diverse during the Mesozoic but declined dramatically after the end of the Cretaceous (I'm not clear whether or not their decline was a direct part of the end-Cretaceous mass extinction). Indeed, entoliids are completely unknown from the fossil record between the Palaeocene and the late Pleistocene; like the tuatara, it might be that the post-Mesozoic survival of entoliids could have gone completely unrecognised were it not for the single surviving relictual genus.

In the earlier post, I implied that propeamussiids lack the eyes and guard tentacles of other pectinids; it turns out that this was a mistake on my part. Many propeamussiids found in the deep sea do indeed lack these features but they are present in shallow-water propeamussiids. It appears that these features are ancestrally common to all crown-group pectinoids but have been lost as an adaptation to life below the photic zone. The anatomy and lifestyle of many propeamussiids remains poorly known but those species that have been investigated have simplified gills compared to pectinids. The filaments of the gills are free rather than being connected by ciliary junctions. The lips of the mantle are also simplified, lacking the complex lobes found in pectinids. These features may be related to the carnivorous diet of many propeamussiids that feed on zooplankton rather than smaller phytoplankton and organic particles.

REFERENCE

Waller, T. R. 2006. Phylogeny of families in the Pectinoidea (Mollusca: Bivalvia): importance of the fossil record. Zoological Journal of the Linnean Society 148 (3): 313–342.