Guenons

The common perception of monkeys tends to be dominated by a relatively small number of species, generally those most commonly seen in zoos, such as capuchins, macaques, baboons or tamarins. But as is usual when it comes to biodiversity, there are a lot of varieties of monkey out there that may be less familiar to the general public. This post will look at one of those less familiar groups: the guenons of the genus Cercopithecus.

Moustached monkey Cercopithecus cephus, copyright Rufus46.

Cercopithecus is a genus of monkeys found in sub-Saharan Africa. The exact number of species has shifted around a bit (though it currently sits around twenty). Some authors have included almost all species of the monkey tribe Cercopithecini, characterised by self-sharpening lower incisors and four cusps on the lower third molars (Lo Bianco et al. 2017), in the single genus Cercopithecus. However, more recent authors have tended to favour dividing this tribe between a number of phylogenetically and ecologically distinct genera. Under this latter system, Cercopithecus would be restricted to a group of more arboreal species. A number of these species have been divided between multiple subspecies and there may be some back and forthing about what is recognised as which. One entirely new species, previously not even known as a subspecies, was described as recently as 2012 by Hart et al.: the lesula C. lomamiensis.

Young female lesula Cercopithecus lomamiensis, from Hart et al. (2012).

A large part of this uncertainty relates to the fact that Cercopithecus species are most diverse in dense forests of western and central Africa, in regions that may be both physically and politically difficult to access and which have received less attention from researchers than others. The aforementioned lesula was described from the Lomami River basin near the middle of the Democratic Republic of the Congo (the one that used to be called Zaire, though I think they prefer not to talk about it). Another Congolese species, the dryas monkey C. dryas, was long thought to be known from only a single juvenile specimen until it was realised that the adult form had been described as a separate species C. salongo. It's still only known from a handful of records and is thought to be critically endangered.

Diana monkey Cercopithecus diana, copyright Ikmo-ned.

Some species of guenon are notable for their striking colour patterns. Perhaps the species I've most commonly seen in zoos is the diana monkey C. diana, native to the region between Sierra Leone* and the Côte d'Ivoire (though it is possible that at least some of these 'diana monkeys' were actually roloway monkeys C. roloway, until recently treated as a subspecies of the diana monkey). This species has a bright white throat, chest and front of the fore arms that contrasts with the black face and dark grey back. It also has a white band across its brow which is where its name comes from, the band having been thought to resemble the crescent moon. De Brazza's monkey C. neglectus of central Africa has a crescent-shaped orange mark on its forehead and a white muzzle and beard, making it look reminiscent of a grumpy old man (Wikipedia claims that it has also been dubbed the 'Ayatollah monkey'). Male De Brazza's monkeys also have a bright blue scrotum. Large bright blue patches are also present around the scrotum and backside of males in the lesula and the owl-faced monkey C. hamlyni.

*Having grown up in New Zealand in the 1980s, I'm going to have that stuck in my head all day now. Nothing to do with the subject of this post, I just thought I'd mention it.

Male De Brazza's monkey Cercopithecus neglectus, copyright Heather Paul.

Guenons tend to be found living in small troops consisting of one adult male and a harem of females with their offspring; unmated adult males will be found living solitary lives. Males are usually larger than females, up to about 1.5 times the size of their mates. Multiple guenon species may be found in a single location though closely related species tend not to overlap. Famously, hybrids have been described from the Kibale forest in Uganda between the blue monkey C. mitis and the red-tailed monkey C. ascanius, two species that are quite distinct in external appearance. Larger species such as the spot-nosed monkey C. nictitans and the blue monkey tend to eat a higher proportion of leaves in their diet. Smaller species such as the mona monkey C. mona may be more insectivorous (Macdonald 1984).

Blue monkeys Cercopithecus mitis stuhlmanni, copyright Charles J. Sharp.

The origins of the Cercopithecus radiation are relatively recent with the tribe Cercopithecini as a whole probably originating in the late Miocene (Lo Bianco et al. 2017). Karyological studies of the group show a wide variation in chromosome number from 58 in the diana monkey to 72 in the blue monkey. In contrast, the sister group of the Cercopithecini, the Papionini (which includes baboons and macaques) always has 42 chromosomes. Polymorphism in chromosome arrangements has also been described within Cercopithecus species. The possibility that this gene variability is related to their rate of speciation remains a worthwhile line of study.

REFERENCES

Hart, J. A., K. M. Detwiler, C. C. Gilbert, A. S. Burrell, J. L. Fuller, M. Emetshu, T. B. Hart, A. Vosper, E. J. Sargis & A. J. Tosi. 2012. Lesula: a new species of Cercopithecus monkey endemic to the Democratic Republic of Congo and implications for conservation of Congo's central basin. PLoS One 7 (9): e44271.

Lo Bianco, S., J. C. Masters & L. Sineo. 2017. The evolution of the Cercopithecini: a (post)modern synthesis. Evolutionary Anthropology 26: 336–349.

Macdonald, D. (ed.) 1984. All the World's Animals: Primates. Torstar Books: New York.

Matoniaceae: Ferns with a Heritage

Ferns are one of those groups of organisms, like sharks and cockroaches, that are not really as ancient as most people imagine. For all that ferns are indelibly associated in the public conscience with antediluvian imagery of steamy coal swamps and great lumbering reptiles, the dominant fern groups that can be seen today did not arise until the Cretaceous and diversified as part of a flora that would have been largely modern in appearance (Schneider et al. 2004). Nevertheless, there are some fern lineages around today that might be said to have a genuine claim to a more venerable pedigree. One such group is the Matoniaceae.

Matonia pectinata, copyright Ahmad Fuad Morad.

In the modern flora, the Matoniaceae are a small family, including only three or four species in two genera, Matonia and Phanerosorus, found in south-east Asia (Lindsay et al. 2003). The two genera are distinct in appearance and habits. Matonia is found on more or less exposed montane summits and ridges and has pedate fronds with pectinate pinnae radiating from an erect central stipe that may grow well over a metre in height. Phanerosorus is found on vertical limestone walls and has pendulous, branching fronds whose pinnae are simple or more weakly pectinate (Kato & Setoguchi 1999). Both genera have the fronds arising from a long, hairy, creeping rhizome. Lateral veins in the pinnules show one or more bifurcations and in Matonia these branching forks may anastomose with each other to form a reticulate vein pattern. The genera also share features of the reproductive anatomy such as massive, deciduous sporangia.

Phanerosorus major, copyright Wally Suarez.

The fossil record of Matoniaceae indicates that they were far more widespread in the past; indeed, Matonia was illustrated from preserved compression fossils before it was described as a living genus (Klavins et al. 2004). Leaf fossils of Matoniaceae go back to the Late Triassic, and the Middle Triassic stem taxon Soloropteris rupex has been more tentatively assigned to the family (van Konijnenburg-van Cittert 1993). Fossil forms are more similar to Matonia in overall appearance and this is presumed to be the plesiomorphic morphology for the family. A certain resemblance exists between Phanerosorus and younger fronds of Matonia and it seems likely that the former genus evolved from Matonia-like forms by a process of paedomorphosis (Kato & Setoguchi 1998). The family was most widespread during the Jurassic and Early Cretaceous but became extinct in temperate regions of the Northern Hemisphere during the Late Cretaceous. It persisted longer in the Southern Hemisphere, with the stem taxon Heweria kempii known from the Early Tertiary of Australia, but at some point following that it became restricted to its modern localised range.

REFERENCES

Kato, M., & H. Setoguchi. 1999. An rbcL-based phylogeny and heteroblastic leaf morphology of Matoniaceae. Systematic Botany 23 (4): 391–400.

Klavins, S. D., T. N. Taylor & E. L. Taylor. 2004. Matoniaceous ferns (Gleicheniales) from the Middle Triassic of Antactica. Journal of Paleontology 78 (1): 211-217.

Konijnenburg-van Cittert, J. H. A. van. 1993. A review of the Matoniaceae based on in situ spores. Review of Palaeobotany and Palynology 78: 235–267.

Lindsay, S., S. Suddee, D. J. Middleton & R. Pooma. 2003. Matoniaceae (Pteridophyta)—a new family record for Thailand. Thai Forestry Bulletin 31: 47–52.

Schneider, H., E. Schuettpelz, K. M. Pryer, R. Cranfill, S. Magallón & R. Lupia. 2004. Ferns diversified in the shadow of angiosperms. Nature 428: 553–557.

Radiolarians of the Globe

Radiolarians are one of the primary groups of micro-organisms to be found among the marine plankton. These unicellular greeblies are justly famed for their intricate mineralised skeletons, leading to their comparison to living works of art. Today's post is covering one particular group of radiolarians, the Spumellaria.

Haeckel's (1899–1904) figure of Hexancistra quadricuspis from Kunstformen der Natur.

Spumellaria are one of the major subdivisions of radiolarians, containing species characterised by a generally spherical skeletal form. Many authors have also included the colonial radiolarians, which often lack a coherent skeleton and may form colonies up to several metres long, in the Spumellaria but these have more recently been treated as a distinct group. The skeleton of radiolarians is entirely enclosed by cytoplasm in life, though in those species in which the skeleton bears radiating spines, those spines may extend beyond the main body of the cell and be covered by only a thin cytoplasmic layer distally. In Spumellaria and anothre major radiolarian group, the Nassellaria, the skeleton is composed of opal, making these living jewels in more ways than one (another radiolarian group, the Acantharea, composes its skeleton of a mineral by the somewhat ethereal-sounding name of celestite). The cytoplasm of radiolarians is internally divided by a fibrous capsule into two structurally distinct sections, the internal endoplasm and external ectoplasm. The denser endoplasm contains most of the cell's primary organelles, such as the nucleus and large mitochondria. Linear microtubular structures called axonemes extend outwards from the endoplasm, passing through pores in the internal capsule and through the ectoplasm. The ectoplasm is often frothy in texture, containing an extensive assemblage of cellular vacuoles. In many of these radiolarians, some of these ectoplasmic vacuoles will house symbiotic algae that contribute much of the radiolarian's nutrition. Otherwise, radiolarians may feed on other small organisms that are captured on axopodia supported by the axonemes, which in spumellarians radiate outwards from the cell body in all directions. Extension and contraction of the axopodia may also help maintain the radiolarian's position in the water column (Cachon et al. 1990).

Schematic diagram of organisation of Didymocyrtis tetrathalamus from Sugiyama & Anderson (1998).

In many spumellarians, the basic skeletal architecture is one of nested spheres and/or globules. Sugiyama & Anderson's (1998) description of Didymocyrtis tetrathalamus stands as a fairly typical example. The central part of the skeleton is a double sphere well within the cytoplasmic capsule with the lobate nucleus contained in the spaces between the spheres. Radiating axes connect the inner shell with an outer shell mostly just outside the capsule (the capsular wall crosses the skeleton at some points). In Didymocyrtis, this outer shell is not spherical but a sort of peanut shape. At each end of the 'peanut', a further cap is added beyond the main shell. In many spumellarians, the outer shell appears spongy in texture, being constructed of densely criss-crossing fine opal fibres. There may be further extensions of the outer shell such as polar spines or funnels.

Not surprisingly, spumellarian classification has most commonly been based on skeletal architecture. Some attempts have been made to construct alternative classifications incorporating cytoplasmic features such as the relationship between the axopods and the nucleus (Cachon et al. 1990) but, as these systems require access to live specimens to place taxa, they have been less popular (especially as most people studying radiolarians are primarily working with fossil material). A phylogenetic study of recent spumellarians by Ishitani et al. (2012) found evidence for two main lineages within the class that differ in ecology. One, including the families Pyloniidae and Sponguridae, contained species found in temperate and cold waters. The other, including the families Astrosphaeridae, Hexalonchidae and Coccodiscidae, was found in tropical waters. Species assigned to the family Spongodiscidae were divided between both lineages, suggesting the need for some further tinkering with the morphological classification.

REFERENCES

Cachon, J., M. Cachon & K. W. Estep. 1990. Phylum Actinopoda. Classes Polycystina (=Radiolaria) and Phaeodaria. In: Margulis, L., J. O. Corliss, M. Melkonian & D. J. Chapman (eds) Handbook of Protoctista. The structure, cultivation, habitats and life histories of the eukaryotic microorganisms and their descendants exclusive of animals, plants and fungi. A guide to the algae, ciliates, foraminifera, sporozoa, water molds, slime molds and the other protoctists pp. 334–346. Jones & Bartlett Publishers: Boston.

Ishitani, Y., Y. Ujiié, C. de Vargas, F. Not & K. Takahashi. 2012. Two distinct lineages in the radiolarian order Spumellaria having different ecological preferences. Deep-Sea Research II 61–64: 172–178.

Sugiyama, K., & O. R. Anderson. 1998. Cytoplasmic organization and symbiotic associations of Didymocyrtis tetrathalamus (Haeckel) (Spumellaria, Radiolaria). Micropaleontology 44 (3): 277–289.