Subspecies comparision of the Genus: Corucia

Subspecies comparision of the Genus: Corucia

--------------------------------------------------------------------------------

From:

FaunaClassifieds Forums > Scientific Journal Section > Scientific Journal Forum

Courtesy of POLYPHEMOS


LEEWAY CORUCIA RESEARCH CENTER (LCRC)


Brian - LCRC
Registered User / Scientific Journal Section moderator
Subspecies comparison of the Genus: Corucia

--------------------------------------------------------------------------------

Subspecies comparison of the Genus: Corucia



Brian L. Schnirel and Sherri L. Jones
Leeway Corucia Research Center (LCRC)
Blenheim, S.C. 29516 U.S.A.

______________________________________________ ________________________

See Addendum after References


Abstract:


Detailed measurements and observations differentiating the two

subspecies of Corucia zebrata (underlined), Corucia zebrata zebrata

(underlined) and Corucia zebrata alfredschmidti (underlined), are

described including new material not previously documented.



Key words: Corucia, Sclera, Parietal, Prefrontal, Rostral, Nasal



Introduction:



Corucia zebrata zebrata(underlined) described and named (Gray, 1855)

and Corucia zebrata alfredschmidti (underlined) described and named

(Kohler, 1997) represent the two subspecies of Corucia zebrata (underlined)-

the prehensile tailed monkey skink.

The common monkey skink (Corucia zebrata zebrata) hails from the

larger islands of the Solomon archipelago southeast of Buka and

Bougainville. This includes Choiseul, Guadalcanal, Isabel, Malaita, Nggla,

New Georgia, Santa Ana, San Cristobal, Shortlands, and Ugi (Balsai,1995).

The North Solomon monkey skink (Corucia zebrata alfredschmidti

(underlined)) hails from the North Solomons which are comprised of

Bougainville and Buka (Kohler,1997).

Bougainville is by far the largest island in the archipelago and being on

the northeast fringe of these islands, supported the establishment of

peripheral isolates evolving into the subspecies alfredschmidti. This is

supported by the sheer number and larger distribution of the subspecies

zebrata in the southeastern islands. The core population of Corucia zebrata

zebrata (underlined) appears to be from Quadalcanal (Balsai, 1995). The

allopatric subspeciation of the Genus: Corucia reveals a larger size of

Corucia zebrata alfredschmidti (underliined) compared to Corucia zebrata

zebrata (underlined). Indeed, a semi-Wallace line appears to exist between

Bougainville and Choiseul. "There is an affinity along the lines of
\
Bougainville - Choiseul, separated by the Bougainville strait, in which the

faunal differences are relatively distinct (faunal differences 86%)"

(Green/Slade,1968). Other animals show a size differential with the

populations on Bougainville being generally larger than that on Choiseul. The

monkey faced flying fox (Pteralopex anceps (underlined)) on Bougainville is

also larger (255-280 mm). On Choiseul, next to Bougainville, the population

is smaller (160-275mm) (E. Bowen-Jones 1997).

The differences between Corucia zebrata zebrata (underlined) and

Corucia zebrata alfredschmidti (underlined) are described here in detail which

should aid in better appreciating the comparative differences between the

two subspecies. As such, identification will achieve a faster result.

However, once one has seen both Corucia zebrata zebrata (underlined) and

Corucia zebrata alfredschmidti (underlined), the visual difference in size and

body coloration alone is readily apparent, even from a distance.


Snout/Vent Length (SVL) & Length Overall (LOA)




common monkey skink
Corucia zebrata zebrata (underlined)





SVL:

Average: Males = 250 mm

Females = 270 mm


Range: Males = 230 - 270 mm

Females = 260 - 280 mm


LOA:

Average: Males = 550 mm

Females = 582.5 mm

Range: Males: = 520 - 580 mm

Females: = 560 - 605 mm




North Solomon monkey skink
Corucia zebrata alfredschmidti (underlined)



SVL:

Average: Males: = 320 mm

Females: = 330 mm


Range: Males: = 290 - 340 mm

Females: = 270 - 330 mm




LOA:

Average: Males: = 660 mm

Females: = 670 mm


Range: Males: = 630 - 680 mm

Females: = 640 - 690 mm




Number of individuals of equal proportions used in study: 96.


A noticable difference in size of neonates is also in evidence: (LOA)

Corucia zebrata zebrata averages about 11 1/2" (Langerwerf, 2006, Schnirel, 2001)

Corucia zebrata alfredschmidti averages just under 15" (Schnirel, 2004)




Czz / Cza neonate comparison:

Corucia zebrata zebrata LOA = 289 mm

Corucia zebrata alfredschmidti LOA = 370 mm


Note:

Both subspecies of Corucia zebrata reproduce by viviparous matrotrophy with the birth
of a single very large neonate. Occasionally, twins are produced, there is one documented case of triplets (Langerwerf, 2003).


Number of young used in study: : 39.




Weight (Average)

Adult Neonate

Common monkey skink = 500 Grams 81 Grams
Corucia zebrata zebrata



North Solomon monkey skink = 845 Grams 173 Grams
Corucia zebrata alfredschmidti


common monkey skink

Corucia zebrata zebrata (underlined)

(Gray,1855)



Czz
Description:

Size:

Smaller size than Northern Solomon monkey skink (Corucia zebrata alfredschmidti (Underlined)).

Average adult: LOA = 572mm (22"), SVL = 262mm (10").



Scalation:

Head
Scalation: The original description by Kohler indicates that common

monkey skinks possess five parietal scales. The

arrangement has, from left to right-head facing observer,

parietal scale one and two larger and less

cramped in width than comparable parietal scales in the

North Solomon monkey skink (width/length ratio- parietal

scale one = 9/13, parietal scale two = 18/27). Parietal

scales encompass nearly the entire left side of the

region (front facing away from observer) of the upper

head. Parietal scale three is positioned centrally

comparable in position to parietal scale four in

the Northern Solomon subspecies. It is larger (length

ratio Czz/Cza = 9/7, Width ratio Czz/Cza = 7/5). Parietal

scale three is triangular with the tapered point directed

towards the rear of the head (width/length ratio =

7/24). Parietal scale four is right of center. It is more

round in shape (length ratio Czz/Cza = 5/8, width ratio

Czz/Cza = 7/9, width/length ratio = 7/8). Parietal scale

five is on the right edge of the head and positioned

more to the rear than the other four parietals

(width/length ratio = 13/30).

Unlike the Northern Solomon subspecies, the common

Solomon monkey skink has no number six and seven

parietal scales. The parietal description is a

guide however, and should not be taken as absolute

except for the total number. In practice, the head

scales are as varied as fingerprints in size and

shape. The prefrontals of Corucia vary in size and

number. Common monkey skinks possess two to three.

Body Scalation:

Dorsal and ventral scales are in a different ratio.

Common monkey skinks are more elongated with a

length/width dorsal scale ratio of 4/9.

\ Northern Solomon skinks have a length/width dorsal

scale ratio of 6/9. Length/width ventral scale ratio for

the common subspecies is 3/7. The

Northern Solomon subspecies length/width ratio = 1/2.


Eyes:

Sclera: A consistent distinquishing feature separating the two

Corucia subspecies is scleral color. Corucia zebrata

zebrata (underlined) has a white sclera. Corucia zebrata

alfredschmidti (underlined) has a black sclera.


Iris: The iris color can vary from dark green, green,

greenish yellow, orange,

and jet-black. A green background iris can be stippled

with brown or black pigment. The green or yellow-green

pigmented iris could be autosomal dominant as is with a

brown-black pigmented iris in humans. This means

only one copy of this gene from a parent is needed in

order for a green-yellow pigment to be manifested in the

individual. For a total black pigmented iris in a Corucia

(which is the least seen); this would signify the black

pigmented gene would have to be contributed by both

parents to achieve this color phase. Unlike the

Northern Solomon subspecies, there is no establishment

of iris color linked to specific islands or cooresponding

phenotypes with the common subspecies.

Body
Coloration:


Holotype
Description: The classic holotype description by John Edward Gray

describes Corucia zebrata zebrata(underlined) as having

prominent banding. The bands are alternating dark

brown-black/ green. The green portion can be of

various shades. The mid body bands are vertical to a

twenty degree forward slope as compared to Corucia

zebrata alfredschmidti (underlined) with a fifty degree

forward slope. Gray also described a play of colors

effect from the body scales,hence the origin of the

scientific name. The Genus name Corucia derives

from the latin coruscus - definition: shimmering.

Zebrata is a latinized form of the word zebra;

pertaining to the zebra-like banding. Black

spots are varied throughout the body. The green in

the body is often blended with brown. The locus

typicus of gray's work with Corucia was on San

Cristobal.


Other
Phenotypes: Unfortunately, not enough research has been done on

populations on specific islands with Corucia zebrata

zebrata (underlined). Certain phenotypes may

correspond to separate islands. The Leeway Corucia

Research Center has found that different phenotypes

within Corucia zebrata zebrata (underlined) will breed

with complete success. In other words, there

appears to be no genetic drift towards speciation to

the point of non-viability of the embryo.

All phenotypes can have black spot pigmentation

throughout the body in various sizes, numbers, and

patterns. The spots may overlap. Dark

green body coloration may occur with little or no black

pigmentation. This may coincide with the report of the

darkest individuals coming from Malaita (McCoy,

1980). There are individuals having incomplete

banding. The incomplete banding consists of

blotches. The blotches are green

to greenish aqua. Some will have no banding or

blotches period.

One phenotype from this category is an army green


color often with little or no black spots. Often, as


previously indicated, the body is flushed

with patches of light brown at various parts of the

body but in addition, there can be brick red around

the head. Yellow is generally less

prominent in Corucia zebrata zebrata (underlined)

than with Corucia zebrata alfredschmidti (underlined).

Some yellow can be seen usually in the throat or

spotted only on parts of the head compared to cases

of almost full yellow on the head of the North

Solomon subspecies. In one documented case, a

highly pigmented (light and dark spots) female

(LCRC/Czz/34) exhibits yellow spots on the tail. To

date, this is the only Corucia seen with this color

pigmentation in the tail region. Some common monkey

skinks have white on the head and throat

(i.e.LCRC/Czz/36). The nasal and rostral scales

of all types are generally darker in color in Corucia

zebrata zebrata (underlined) than with Corucia zebrata

alfredschmidti(underlined). North Solomon monkey

skinks have a distinctive yellowish-cream color to the

nasal and rostral scales which appears striking in

North Solomon monkey skink




Corucia zebrata alfredschmidti (underlined)

(Kohler,1997)


Cza
Description:

Size: Larger size than the common monkey skink (Corucia

zebrata zebrata (underlined)).

Average LOA = 690mm (27"), SVL = 335mm (13").


Head
Scalation: As based on Kohler, North Solomon monkey skinks

possess seven parietal scales. The arrangement has,

from left to right-head facing

observer, parietal scale one and two smaller and more cramped in width

than comparable parietal scales in the common monkey skink (width/length

ratio: parietal scale one = 4/6, parietal scale two = 13/25). Parietal scale

three is smaller in length and width (width/length ratio = 13/16) than

comparable scale in Corucia zebrata zebrata (underlined) (pointed towards the rear of

the skull). Parietal scale four is centralized and elongated with a bottleneck

appearance near vertical center (narrowest point width/length ratio = 2/19,

total width variation ratio = 4/17,). However, the original description of the

holotype and paratypes has no mention of parietal scale four ever pinched-off completely rather than bottlenecked. The

illustration in Salamandrae gives

the impression that the bottleneck configuration is standard. Head scales

actually vary in size and shape as much as the black pigment spots on the

body. In common observation, most specimens of Corucia zebrata

alfredschmidti have the pinced-off version. Parietal scale five is just right of

center rather than at the dextral edge as in the common monkey skink

(width/length ratio = 13/17). Parietal scale five is also more symmetrical in

shape and squarer than parietal scale five in the common monkey skink.

Parietal scale six (not found in Corucia zebrata zebrata(underlined)) is comparable in size

and shape to parietal scale three (width/length ratio = 12/17). Parietel scale

seven (not found in Corucia zebrata zebrata(underlined)) is elongated and more pointed

to the front of the skull (width/length ratio = 7/12). Parietal scale seven is at

the dextral edge of the head. Prefrontal scalation varies from two to four

compared to two-three in the common monkey skink.

In summation, head scales are not the best indicator of Corucia

subspecies classification. It takes a trained eye and much close up viewing to

get an accurate determination. The unwavering criteria to utilize is that

Corucia zebrata alfredschmidti (underlined )has 2 more parietals (six and seven) than with

Corucia zebrata zebrata (underlined).


Body
Scalation: North Solomon monkey skinks have been described as

having larger ventral and dorsal scales than the common

monkey skink (Kohler,1997).

The scales are larger in general due to the larger ultimate size of this

subspecies of Corucia. However, in a ratio comparison of width/length,

there is a difference as noted in the common monkey skink section.

LCRC research data shows that in a width/length ratio of dorsal scales,

North Solomon monkey skinks have a ratio of 6/9. Common monkey

skinks have a ratio of 4/9. The ventral width/length ratio is 1/2 for the

Northern Solomon monkey skink and 3/7 for the common monkey skink.


Eyes:
Sclera: As noted earlier, Corucia zebrata alfredschmidti

(underlined) has a black sclera and

Corucia zebrata zebrata (underlined)

has a white sclera. This is unvaried.



Iris: The iris color of Corucia zebrata alfredschmidti

(underlined) does not seem to vary as much as in


Corucia zebrata zebrata (underlined).

The color is almost always a green-

yellow mix - at least in Corucia zebrata alfredschmidti from Bougainville.

However, Corucia zebrata alfredschmidti from Buka appear to have a more

intense green iris.

Besides the striking head color and larger ultimate size, the eyes of

Corucia zebrata alfredschmidti (underlined) are another very prominent and stunning

attribute of this subspecies. The yellow-green iris coloration surrounded by

the black sclera makes this so.



Body
Coloration: The top of the head in the North Solomon Monkey skink is a striking

turquoise often suffused with yellow. This concurs with the holotype

description by Kohler. Most of the yellow is prominent in the throat and

chin region but may occur on top of the head as well in several areas including

the region around the ear openings. There has not been observed in Corucia zebrata alfredschmidti, a yellow spotted individual in the tail region like the

LCRC / Czz /34 specimen. From imports of highly questionable legal

passage but traced and personally seen, it appears that North Solomon

Corucia that hail from Buka differ from the main pennisula contingent in that

the Buka contingent of Corucia shows a light brownish component overlaying

the bright turquoise on the head. In addition, as mentioned, the iris is an

intense green. Otherwise, all other aspects of Buka Corucia zebrata

alfredschmidti (underlined) are germane to that of

Bougainville Corucia zebrata alfredschmidti (underlined). It would appear,

that the Buka Corucia are a polytypic

variant but would not constitute a separate subspecies classification.

As with the common monkey skink, North Solomon monkey skinks

are found with and without banding. The banded individuals have central

bands that slope at a 50 degree angle. Common monkey skinks have a

0 - 20 degree angle to the transverse torso of the body. This has also been

noted by Burt Langerwerf of Agama International. The bands on the

North Solomon monkey skinks are a consistent light brown whereas

common monkey skinks are darker brown to black. The lighter brown

banding in contrast to the aqua bands gives a more faded appearance to the

North Solomon subspecies compared to the common subspecies. Blotched

North Solomon individuals are occasionally encountered. Both banded and

unbanded North Solomon monkey skinks may have black spots. Northern

Solomon monkey skinks have the light brown tone mentioned in the bands

often intermixed with the aqua of the body. Common monkey skinks often

have a brown wash with the green/aqua color of the body but the brown is

usually darker. All North Solomon monkey skinks have a distinctive

yellowish-cream color to the nasal and rostral scales in contrast to a darker

color in common monkey skinks as noted in the common monkey skink section.

The cream color of these scales also shows a significant contrast to the turquoise

color of the head of the North Solomon subspecies. contrast to the generally turquoise head






Kohler lists the holotype of Corucia zebrata alfredschmidti (underlined) as holotypes SMF

77587 with locus typicus being the island of Bougainville (Mekamuri or North

Solomons). The Holotype resides in the Senckenberg Museum, Frankfort

Germany (Museum Franfort Senckenberg an lage 25 60325 Frankfort am main D.

Germany tel +49 06917542-0 fax ++90691746238). The holotype is described as

being an adult Male.


The Paratype of Corucia zebrata alfredschmidti (underlined) is listed as MTKD - 39481. The

paratype resides in the Staatiches Museum Fur tierkunole Augustus strasse 2

Dresden Germany. The Paratype is described as being unknown in gender.



The Leeway Corucia Research Center (LCRC) Studbook classification system is as follows:


LCRC / Czz / 34




LCRC = Corucia Research Center of individual




Czz = Subspecies classification Czz = Corucia zebrata zebrata (underlined)

Cza = Corucia zebrata alfredschmidti (underlined)




34 = Individual number at research center


Discussion:


Although Genetic drift of the peripheral isolates of the Corucia population

resulted in the subspeciation of Corucia zebrata alfredschmidti, (underlined) the ecological

niche in this subspecies remained constant. This is based on a pattern in the

Scincidae where the more arboreal the species, the proportionally longer the

digits. A smooth, non-varying, numerical progression can be seen from species

of various niches based on anterior foot length (the junction of the ulna / radius

carpal bones to longest digit) divided by the snout to vent length (SVL). In the

case of Corucia, both subspecies occupy a high canopy arboreal niche with the

same numerical value.

Although no viable cross subspeciation has been documented resulting

in 'whatticles' (Jones, 1984), being subspecies, it is theoretically possible to

cross North Solomon Corucia with common Corucia. Balsai (1995) has

theorized that common Corucia from various islands have been genetically

apart enough based on miscarriages that have occurred in captivity.

However, many breeding centers have had great success rates in breeding of

this species of different phenotypes. The South Florida Corucia Research

Center had a 100% success rate of over thirty births. Agama International also

shows a positive record. Other factors may be the reasons for the

miscarriages resulting in slugs (miscarriages) or stillbirths other than genetic

incompatibility that need to be explored. For instance, improper



environmental conditions (humidity, temperature, diet, etc.), stress, disease,

exposure to toxins, the possibility of too much genetic closeness if the mated

pair came from the same island canopy and were closely related, etc. Other

than Corucia zebrata zebrata (underlined) and Corucia zebrata alfredschmidti (underlined), there appear

no other candidates for subspecies classification. As such, genetic

incompatibilty between the common subspecies of Corucia is a topic that

requires further research. Although common Solomon monkey skinks may not

exhibit miscarrages due to genetic drift, it would be logical to conclude that

between subspecies (Corucia zebrata zebrata (underlined)and Corucia zebrata

alfredschmidti (underlined), they could be enough apart that breeding between the two

would result in genetic misfires to some degree. This, of course, would be

based on the time honored rule of distinct speciation depending on a species

being unable to produce a viable species with another. Whether or not the

two subspecies straddle the fence of genetic compatibilty is also a future

topic of research.

To distinquish Corucia subspecies in summation, if one cannot see the

two subspecies in comparison or a photograph, look for the following. In

Corucia zebrata alfredschmidti (underlined), two extra parietal scales, or up to two extra

pre-frontal scales, a black sclera, bright turquoise head (in most cases), and in

banded individuals, a 50 degree slope in banding. In a visual comparison, look

for a reduced ratio in dorsal and ventral scale ratios of width/length of

Corucia zebrata alfredschmidti (underlined) compared to Corucia zebrata zebrata (underlined). A larger

size of approximately 17%, a lighter brownish coloration - especially a faded

appearance in the banded individual, and a noticeable contrast between body

coloration and nasal and rostral scales - with the scales having a distinctive

yellow cream coloration.


References:


Balsai, Michael J.; 1995. Husbandry and breeding of the Solomon islands

prehensile-tailed skink (Corucia zebrata). The

Vivarium,

Escondido, California, U.S.A. pp. 4-11.


Bowens, E.; Jones; 1997. Flying foxes on Choiseul (Solomon islands) - the

need for conservation. Oryx, Volume 31, July,

Cambridge, U.K. page 309.


Coburn, John; 1996. Prehensile tailed skinks. T.F.H. Publications

Inc. Neptune City,

New Jersey, U.S.A. 64 pages.


De Vosjoli, Phillippe
1993. The general care and maintainence of

prehensile tailed skinks.

Advanced Vivarium Systems Inc.,

Lakeside, California,

U.S.A. 57 pages.


Kohler, G.; 1997. Eine neue unterart des wickelshwanz skinkes

Corucia zebrata

(underlined) von Bougainville, Papua

Neuguinea - Salamandrae, Germany

Volume 33, Issue 1, pp. 61-65.


Green, Slade; 1968. Island patterns in the Solomon islands bird

fauna. Evolution, Volume 11-Number 4,

December, London, U.K. pp. 751-761.


Langerwerf, Burt; 2003. Agama International; Personal

communication.


McCoy, Michael; 1980. Reptiles of the Solomon islands. Wau Ecology

Institute, Handbook No. 7:30. Papua New

Guinea.


Parker, F.; 1983. The prehensile tailed skink (Corucia zebrata)

on Bougainville island, Papua New Guinea.

Advances in herpetology and

evolutionary biology, Museum of Comparative

Zoology, Cambridge, Massachusetts, U.S.A.

pp. 435-440.


Schnirel, Brian L. 2004. Seni biometric analysis on the extinct

Scincidae species: Macroscincus coctei

(underlined). Polyphemos, Volume 2, Issue 1,

May, Florence, South Carolina, U.S.A.

pp. 12-22.


Brian L. Schnirel
LCRC

Addendum:


The color, banding, blotches and spots mentioned are adaxial in general. The abaxial area (lower chest and belly region to vent) is void of bands and spots. It is generally a solid green or aqua.


Brian
LCRC