COLOR VISION IN ANIMALS

Their color vision is a direct a function of how many cones are present in the eye. The more cones, the better the color vision. The following list summarizes the principal animal groups. The actual determination of how many cones are present requires detailed study of the interior of retina, so that the cones can be accurately counted.

NUMBER OF CONES vs ANIMAL GROUPS, listed in decreasing number and quality of color vision:

The mantis shrimp has been reported as having supposedly 16 cones. Recent detailed research by Morrison (2014) shows, however, shows that the mantis shrimp probably has no more than six!

Many butterflies and non-nocturnal birds reportedly have as many as 5 cones (note: these animals can perceive the colors red, green, and blue + ultraviolet wavelengths in some cases).

The bluebottle butterfly most likely has no more than five cones–-certainly, not as many as 15, a number commonly mentioned on the internet whenever one does “a quick search that typically has a one-paragraph answer. These brief reports have no cited references of current detailed studies. The bluebottle butterfly does have, however, the capability of detecting very specific wavelengths of light, for example, blue-colored insects flying against a blue sky! More research is needed to clarify the issue.

Many insects, birds, and fish have 4 cones.

Up to four percent of female humans also have 4 cones. This rare condition is called tetrachromacy.

Other humans have 3 cones and perceive the colors red, green, and blue.

Horses have 2 cones and perceive colors blue and yellow.

Cats and dogs have 2 cones and perceive colors blue and green.

Fish have 2 cones.

Crustaceans have 2 cones and perceive colors blue and red.

Rabbits and rats have 2 cones and perceive blue and green. Rats also can detect ultra-violet light.

Squirrels and insects, including bees, also have 2 cones and perceive blue and yellow. Bees can also detect ultra-violent light.

Snakes have 2 cones; also they can see infra-red light.

Jumping spiders have 1 cone and can distinguish only green and ultra-violent light.

Cephalopods (squid, octopi, etc.) have 1 cone and can distinguish blue light only.

SOME OTHER INTERESTING FACTS:

Eagles have the best eyesight in the animal kingdom and can detect and focus on prey up to two miles away!

Amphibians can see some color.

Snails see only black and white (they do not have color vision).

Slugs have fuzzy vision (probably only in black and white).

Tridacna (so-called “killer clams”) and scallops clams (e.g., Pecten clams have many blue eyes, which are small pinhole eyes known as haline organs, on their exposed mantle. These are light-sensitive and can detect changes in light levels. A concave reflective layer (called the argentea) is present close to the lens of their eyes and reflects the image back, thus reversing the image twice and correcting it, unlike our own eyes. For more information on Tridacna clams, see my earlier post (Friday, April 12, The "Killer" Clam).

REFERENCE

Morrison, J. 2014. Mantis shrimp’s super colour vision debunked. Nature, doi:10.1038/nature.14578 

FUTURE EARTH (IN 250 MILLION YEARS FROM NOW)

(Pangaea Proxima)

Since the beginning of the Earth, its continents have been and still are in constant motion, as tectonic plates collide together and break apart. Uplift will continually form new mountain ranges in the continents, whereas old ocean-floor crust will be pulled below the Earth's surface (i.e., subducted) and eventually disappear (re-melted). This process of formation of new mountain ranges and subduction of the older ocean floor has been going on since the beginning of Earth and will continue as long as the inside of Earth generates heat.

Today, the Atlantic Ocean is widening by approximately an inch year, as the ocean floor plate under it is spreading apart, forming new oceanic crust. The older, overlying granitic land masses move about and their shapes can get re-configured, but overall, because of their lighter density, they will remain on the Earth’s surface.

In about 250 million years, a new supercontinent (i.e., Pangaea Proxima) will most likely form. Only a vestige of the Atlantic Ocean will remain, as its shores collide, but the land masses of the continents will grow larger because of the collisions.

The map shown here is based on a map published by National Geographic in 2018.

Reconstructions of the land masses through time have been mapped and compiled by numerous workers. One of the most notable is C. R. Scotese (his maps are readily available online, eg. Scotese, 2021). He has studied and shown in detail, the reconstruction of the Mesozoic and Cenozoic land masses through time.  

Reference

Chwastyk, F. W. 2028. Future Earth. National Geographic, June, 2018. 

Scotese, C. R. 2021. An atlas of Phaneozoic paleogeographic maps: the seas come in and the seas go out. Annual Review of Earth and Planetary Sciences, v. 49:679–728 (free pdf). 

MUSSELS ON NIPA NUTS

The association between the fruit of the modern-day, low-coastal (tidal estuarine), jungle-dwelling, nipa palm (Nypa fruticans Wurmb) and ocean-dwelling mussels (clams) is not one that you would expect to find hundreds of kilometers from the nearest palm trees (at 11°S in Australian oceanic waters). Yet, they do co-occur!

Example of a typical low-tidal estuarine environment habitat of the modern nipa palm (image derived from Wikipedia).

Nipa is one of the oldest angiosperm plants and probably the oldest palm species. It first appeared during the late Cretaceous (Maastrichtian Stage) 56 mya (million years ago) and had a pan-tropical distribution until middle Miocene time (13 mya). Fossilized nuts of confirmed Nypa dating to the early Eocene occur in deposits of the London Clay. 

Nipa palms originated in Indonesia, Malaysia, Philippines, Thailand, and Papua Guinea. It is native to the Indian and Pacific Oceans. The genus is montypic because N. fruticans is its only member. 

Unlike most palms, the nipa palm’s trunk grows beneath the ground. Only the leaves and stalk grow above ground. The leaves of the plant extend up to 9 m in height, and its flowers, are red or yellow in color. The fruit is made up of many seeds arranged in tough, spiky fibrous clusters, up to 25 cm (10 inches) in diameter. Each cluster (ball) has its own stalk. Eventually, each ball detaches from its stalk and can float away on the tide.

Modern-day nipa-nut clusters (image derived from Wikipedia).

The clusters have to be ripped apart, and each cluster yields many large nuts. It takes skill, much effort, and a strong cutting tool (machete) to expose the nuts (see videos on YouTube and Wikipedia).  

Two attached bivalves (mussels) of Aphrodita longissima in situ on a nipa-nut cluster (figure from Loch, 1990).

Other bivalves found today that can attach to nipa nuts include Adipicola longissima (Theile and Jaekel) and Idasola coppingeri (E.A. Smith).

Due to limited production, widespread other-crop cultivation, and a lack of harvesing practices, as well as deforestation and habitat destruction have put the Nipa palm at risk.

Several mollusks [e.g., 2 bivalves—Crassostrea and Brachiodontes; nine gastropods (including Nerita, Littoraria, and Tegula); 2 barnacles (including Lepas); and 1 chiton] have also been reported as associated with nipa rafts floating in the ocean (Raven, 2019)

It is suspected that these nuts and other wood trawled by these oceanographic ships were derived from Papua rather than the Australian mainland. Nipa palm nuts can float for considerable distance and duration.

Oceanographic research vessels cruising in tropical waters occasionally find shallow-marine bivalves living on the ends of nipa nuts. These cruises typically occur in the open-ocean areas overlying 1600 m of water!

REFERENCES CONSULTED

https://www.youtube.com/watch?v=BEQZ-kpo905g

en.wikipedia.org  2024.

Ian Loch. 1990 (February). Mussels on nuts. Australian Shell News, no. 69, a newsletter of the Malacological Society of Australia, pp. 1-2.

Raven, J.G.M. 2019. Notes on molluscs from NW Borneo-dispersal of molluscs through nipa rafts. The Festivus 5, issue 1, pp. 1-10.

KEEPING THE TERMINOLOGY STRAIGHT

How do paleontology, archeology, and anthropology differ? As I watch movies and television shows, I am constantly reminded that many writers do not seem to know the differences and commonly lump two or more of these sciences together. If you are also confused or uncertain, please read on: 

Paleontology (also spelled by some as palaeontology) is the scientific study of fossils, which are the remains and traces (e.g., tracks, trails, burrows) of ancient life forms older than 10,000 years. The cutoff time is arbitrary, but the 10,000 years datum is useful because it is beyond recorded time. Ancient life forms include bacteria, invertebrates, fish, amphibians, reptiles, and all mammals. The latter category encompasses human remains (if they older than 10,000 years) and their activities that leave traces.

Paleontology encompasses also the following specialities:

  Invertebrate paleontology: study of fossil animals without backbones

  Vertebrate paleontology: study of fossil animals with backbones

  Micropaleontology: studyof microscopic ancient lifeforms

  Paleobotany: study of ancient plants

  Ichnology: study of tracks and fossils of ancient lifeforms

  Exopaleotology: study of extraterrestrial lifeforms

Archeology (also spelled as archaeology) is the scientific study of ancient human remains and the ancient activities of humans (especially human artifacts). The fossil record of humans is late Pliocene to modern times. Because the geologic record of humans is approximately during the last 4 million years old, archeology is confined to that time range.

Anthropology is the scientific study of the origin and of the physical, social (including language), cultural development, and behavior of humans. There are specialists (cultural anthropologists) who focus their studies mainly on cultural anthropology, whereas others (physical anthropologists) focus their studies mainly on the long-term biological development of the human body.

   Forensic anthropology = examination of human skeletal remains for law-enforcement agencies 

   Paleoanthropology = concerned only with fossil hominids 

ENTELODON: SO-CALLED “KILLER PIGS”

Entelodon [the name means “complete teeth”) were large pig-like mammals that lived in forests of the northern continents, especially Europe. They are classified as entelodontids. They were not true pigs, and the moniker “killer pigs” is very misleading. Molecular studies indicate that Entelodon was more closely related to hippos and cetaceans (whales) than to pigs or peccaries.

Entelodon sp. (length 2 m), from the Oligocene of Europe. 

      Classification (from Wikipedia, 2024):

Kingdom Animalia

Phylum Chordata

Class Mammalia

Order Artiodactyla (= even-toed ungulates)

Suborder Suina

Family Entelodontidae

Genus Entelodon

Entelodon teeth are similar to pigs [i.e., dentition formula 3.1.4.3/3.1.4.3] --- namely, each row has three pairs of robust incisors, a pair of large canines, four pairs of premolars, and three pairs of simple flat molars. For an explanation of mammal dentition, see one of my earlier posts that discusses this subject matter. Entelodon incisors were commonly stout and blunt and their canines robust, suggesting that Entelodon was an omnivore and especially good at browsing (for nuts and fruit, branches, and carrion?). Its adult teeth were especially good for crushing and grinding. 

This genus ranged from the late Eocene to early Miocene (38 to 19 million years ago) and lived in Europe, Asia, and North America. They were most common during the Oligocene, especially in Europe. They were never abundant in North America although they survived there until the early Miocene. 

Entelodon resembled a large wild boar. Entelodon’s length was about two meters. Most individuals were no taller (at the shoulder) than about 6 feet. They were strong shouldered and had a bison-like spinal hump and a heavy head. They also had a huge head, and their cheekbones developed huge flanges that projected downwards and outwards. Also, the underside of their lower jaw had one or two pairs of knob-like tubercles that were variable in size from individual to individual.

[Note: The largest known entelodonid [genus Daeodon] lived in North America. It was up to 1650 pounds in size and reached almost 7 feet tall at the shoulder].

Entelodon could have run well but probably not at high speeds nor for too long. 

REFERENCES CONSULTED

Savage, R.J.G. and M.R. Long, 1986. Mammal evolution (an illustrated guide). British   Museum (Natural History), 259 pp.

Wikipedia. 2024. 

OSTRICHES

They are the largest flightless birds living on Earth today. They can be up to 9 feet tall and weight up to 300 pounds. They have the fastest land speed of any bird. They can run steadily up to 34 mph, and can run up to 43 mph, for short durations. They have also the largest eyes of any land vertebrate. They have claws at the end of their wings. For a comparsion of the size of the ostrich egg to that of a modern chicken, see my June 11, 2022 blog. 

Their earliest relatives (referred to as “paleotididae struthioniformes”) were widely distributed, as early as the late Eocene in Asia, Europe, and, to a lesser degree, in North America. The first true ostriches first appeared in Africa during the early Miocene, and, today, wild ostriches are confined to Africa (Mayr et al. 2021). Some escaped ostriches in Australia represent feral populations.

CLASSIFICATION (see Wikipedia, 2024)

Class Aves [=birds)

Order Struthioniformes [=ratites]

Family Struthionidae

Genus Struthio Linneaus, 1758, type species S. camelus Linneaus, 1758

       

Species:

S. camelus camelus = “red-necked,” North African ostrich they  are the most wide ranging ostrich but do not live in the Sahara Desert region).

S. c. australis = “black-necked,” South African ostrich

S. c. massaicus = “pink-necked,” Masai ostrich (central eastern Africa)

S. molybdophanes = “bluish-necked,” southern Ethiopia, NE Kenya, and Somalia

Two individuals of Strutio molybdonphanes (showing color variation) living at the Living Desert Zoo and Gardens in Palm Desert, Riverside County, southern California.

References Cited

Mayr, G. and N. Zelenkov. 2021. Exintct crane-like birds (Eogruidae and Ergilornithi) from the Cenozoic of central Asia are indeed ostrich precursors. Orthnithology 138(4):1-15. Pdf is free.

Wikipedia. 2024. Ostriches. 

GIRAFFES

They are the tallest mammals today, have an even number of toes, and are geographically limited today to central Africa. Why giraffes have such long necks is still resolved; for example, do the long necks help obtain food more easily, and/or did their long necks evolved to be used for battle against other giraffes? Perhaps, it is for both reasons.

Figure 1: A juvenile giraffe living at the Los Angeles County Zoo. The author took this picture about 30 years ago.

Figure 2: A typical giraffe skull. The dental formula is 0/3, 0/1, 3/3, 3/3 = 32 teeth(see one of my earlier posts that discusses the details of how to determine dental formulae of vertebrates. Note that the upper canine teeth are absent. Also, this skull shows the  three unbranched “horns” typically present in both sexes. As shown here, the unique third bone is often found (especially in males) is in front and between the other two horns (Lawlor, 1979). 

Determining how many living species there are of giraffes has historically not been an easy task. There has been little or no agreement about this matter, which has been going on over many years now.   

Back in the early 1900’s, workers claimed that there is only a single species and nine subspecies. Woolston (2016) did a detailed study of 97% of giraffe’s DNA and determined that there are four species. Subsequent DNA studies by Fennessy et al. (2017) and Coimbra et al (2021) corroborated this number. Nevertheless, in 2023, the number of any possible subspecies ranges continues to be reported by various workers, as from two to four (usually four).

For those who are interested, Pheasant (year not given) has a blog post that agrees that there are four giraffe species. He also included a useful distribution map, showing that most of them live today only in the southern half of Africa [none live in the Sahara region]. They evolved and separated and have not crossbred, thereby there has not been any exchange of genetic material for millions of years. Only about 100,000 giraffes are estimated to be living “in the wild,” and as in the case of other large land mammals, their numbers are dwindling.

Giraffes range in geologic time back as far as about 20 million years ago (i.e., early Miocene). Their long necks first appeared even as early as the Miocene. Even then, they lived in forests. About 8 million years ago, when climate changes caused their eating habits to changes, they started adapting to living in more-open areas.They are most closely related to pronghorns, deer, antelopes, buffalo, goats sheep, and cattle (Wikipedia, 2024).

Classification:

ORDER Artiodactyla

FAMILY Giraffidae

Genus Giraffa

4 Species 

  giraffa---------------southern giraffe, mainly So. Africa, Namibia, & Botswana

  tippelskirchi--------Masai giraffe, in Tanzania, Kenya, and Zambia

  reticulata-----------G. cameloparadis, scattered groups in central and eastern Africa 

 cameloparadalis---G. camelopardalis, in Ethiopa and South Sudan

note: some authors, but not all, recognize “subspecies” 

Genus Okapia (has zebra-like stripes on its posterior and legs)

1 Species

  johnstoni---limited geographically to central-African rain forests

Figure 3. Okapia johnstoni. This relative of giraffes is about 5 feet tall (at the shoulder) and weights about 440 to 770 pounds. It is mainly active during the day and lives a solitary life in dense forests in the Congo region of central Africa, at 1600 to 4,900 feet in elevation. It eats leaves, fruit, and fungi. The Okapia has an extremely long tongue that can clean its eyes and ears. 

Other Comments:

Although nearly all giraffes are reticulated (consisting of connected “spots”), some genetic mutants have a solid brown color (Maron, 2024). Examples like the latter show that relying on color patterns for identifying a species is not always reliable, yet the very similar geometric and color patterns of giraffes are given heavy emphasis for identification as to species.

I have attempted to decipher, via illustrations in the literature, how the so-called different species of giraffes are differentiated by the shapes and sizes of their spots/reticulations. My attempts were frustratingly inconclusive.

REFERENCES CITED

Coimbra, R.T. F. and others. 2021. Whole-genome analysis of giraffe supports four  distinct species. Current Biology 31:2929-2938.

Lawlor, T. E. 1979. Handbook to the orders and families of living mammals. Second edition. Mad River Press, Eureka, California, 327 pp. 

Pheasant, T. year unknown. The four giraffe species explained. Bonamy (an online blog)

Maron, D.F. 2024. On the coat tales. National Geographic. January, 2024, p. 25.

Wikipedia. 2024

 

Woolston, C. 1026. DNA reveals that giraffes are four species, not one. Nature 537:290-291.