THE GENETICS OF ATYPICAL MACROMELANOPHORE GROWTH IN PLATYFISH - SWORDTAIL HYBRIDS AND THE HISTOLOGY OF THEIR GONADS AND PITUITARIES

Citation preview

IN F O R M A T IO N T O USERS

This material was produced from a microfilm copy of the original document. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted. The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction. 1. The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spliced into the film along w ith adjacent pages. This may have necessitated cutting thru an image and duplicating adjacent pages to insure you complete continuity. 2. When an image on the film is obliterated with a large round black mark, it is an indication that the photographer suspected that the copy may have moved during exposure and thus cause a blurred image. You will find a good image o f the page in the adjacent frame. 3. When a map, drawing or chart, etc., was part of the material being photographed

the

photographer

followed

a

definite

method

in

"sectioning" the material. It is customary to begin photoing at the upper left hand corner of a large sheet and to continue photoing from left to right in equal sections with a small overlap. If necessary, sectioning is continued again — beginning below the first row and continuing on until complete. 4. The majority of users indicate th at the textual content is of greatest value, however, a somewhat higher quality reproduction could be made from "photographs" if essential to the understanding of the dissertation. Silver prints o f "photographs" may be ordered at additional charge by writing the Order Department, giving the catalog number, title, author and specific pages you wish reproduced. 5. PLEASE received.

N O TE:

Some pages may

have indistinct print. Filmed as

Xerox University Microfilms 300 North Zeeb Road Ann Arbor, Michigan 48106

LD3907 .07 19*0 •A 8

1.

13-219X8

Aronowitz, Olga, 1923The genetics of atypical macromelanophore growth in platyfishswordtail hybrids and the histology of their gonads, with some notes on the histology of their pituitaries. New York, 1950# el|.3,76 typewritten leaves, illus., plates,charts,diagrs•,tables, 29cm. see next card

O

Sf>etf n.:*

2.

LD3907 .G7

1950 •A8

Aronowitz,'Olga, 1923The genetics of atypical macromelanophore growth'in platyfish-swordtail hybrids ... (Card 2) Thesis (Ph.D.) - New York York University. Graduate School. 1950. Bibliography: p.61-76. C57666 Shelf List

Xerox University Microfilms,

Ann Arbor, Michigan 48106

T H IS D IS S E R T A T IO N HAS BEEN M IC R O F IL M E D E X A C T L Y AS R E C E I V E D .

library

op

HEW IORI UNIVERSITY m u m S I T I HEIGHTS

V

THE GENETICS OF ATYPICAL MACROMELANOPHORE GROWTH TO PLATYFISH-SWORDTAIL HYBRIDS AND THE HISTOLOGY OF THEIR GONADS, WITH SOME NOTES ON THE HISTOLOGY OF THEIR PITUITARIES

Olga Aronowitz April 15, 1950

A dissertation in the Department of Biology submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at New York University.

Table of Contents

Introduction Acknov.ied frments Material and Methods Platypoecilus maculatns Female x Xiphonhorus hellerii Male Xiphophorus hellerii Female x Platypoecilus maculatus Male Measurements and Counts Decree of Macromelanophore Pigmentation Histological Techniques Pituitaries Classification of Gonads Ovaries Testes Statistical Methods Results Distribution of Macromelanophore Patterns Abnormal Pigment Cell Growth Incidence of Melanoses and Melanomas Among the Various Genotypes vdthin a Second Generation Population In Two Second Generation Populations In Second Generation and Backcross Generations Discussion of Atypical Pigment Cell Growth Testes: The Normal Gland Histology of Testes in Platyfish-Swordtail Hybrids Ovary: The Normal Gland Histology of Ovaries in Platyfish-Swordtail Hybrids

Pages The Relationship between Ovarian Development and Distribution of Macromelanophores

24.

Animals without Gonads

25

Discussion of Poeciliid Gonads

26

Seasonal Changes in Poeciliid Testes

26

Male Hormone Secretion

26

Relation between Hormones and Abnormal Testes

27

Juvenile Testes and Mature Gonopodia

28

Cyclic Behavior of the Ovary

29

Hormone Production by Fish Ovaries

31

The Genetic Constitution of Animals withImmature Ovaries

31

Abnormal Gonads: A Frequent Result of Hybridization

32

Pituitary: The Normal Gland

33

Total Cell Count of the Transitional Lobe of the Pituitary of Hybrids

34

Differential Cell Count of the Transitional Lobe of the Pituitary of hybrids

35

Discussion of Pituitary Cell Count

36

Review of literature on the T'eleost Pituitary

37

Taxonomic Characters

39

The Number of Dorsal Fin Rays

39

The Mean Number of Dorsal Fin Rays in Wild and Laboratory Bred Poeciliids

40

Association between Number of Dorsal Fin Rays and Macromelanopnores

42

Scales along the Lateral Line

43

Body Indices

44

Discussion of Taxonomic Characters

46

Genetics of Sword Length

46

Body Indices of Pure Species and Hybrids

47

Pages General Discussion

4.8

Isolating Mechanisms

4.8

Genetics of Atypical Pigment Cell Growth

52

Tumors in Interspecific Hybrids

52

Genetic Differences Behind Similar Phenotypes in Two Species

54

Relation betvreen Abnormal Pigment Cell Growth, Abnormal Gonads and the Pituitary

55

Phylop.eny of -telanotie Tumors in Vertebrates

56

Summary

57

Bibliography

61

Introduction

The platyfish, Platypoecilus maculatus. and the swordtail, Xiphophorus hellerii, are small, viviparous cyprinodont fishes of the family Poeciliidae. They live together (sympatrically) in a number of fresh-water drainage systems of Mexico and Guatemala.

In spite of the large number of specimens which

have been collected in their natural habitats, a hybrid has never been found in nature. During the early part of the twentieth century platyfishes and sword­ tails were imported from Central America into Germany by tropical fish fan­ ciers; it was then found that these species hybridize readily when in captiv­ ity.

Amateur fish breeders Losslein (1912), Haffner (1913) and Gramsch

(1913) were the first to report that hybrids with a spotted color pattern develop a cancer-like growth but that unspotted hybrids do not.

However,

no detailed study appeared until 1928, when Haussler (1928, 1934) published his first paper on the neoplastic character of melanomas in platyfish-swordtail hybrids.

Kosswig (1928, 1929a* b, c, 1931) described the inheritance

and histology of these melanomas in both spotted and black-banded hybrids. Platyfish have many different patterns formed by various arrangements of two kinds of pigment cells, micro- and macro-melanophores.

Gordon

(1927, 1928) and Fraser and Gordon (1929) determined the genetic behavior of these micro- and macro-melanophores, and Reed and Gordon (1931) described the histology of the melanotic and melanomatous platyfish-swordtail hybrids. In a series of experiments Gordon (1931, 1932, 1937, 1941) and Gordon and Flathman (194-3) then showed that it is the platyfish macromelanophore gene that acts in conjunction wfcth a series of swordtail modifier genes to pro­ duce atypical pigment cell growth in a platyfish-swordtail hybrid.

Further,

Gordon (1948) demonstrated that there are five sex-linked, allelic genes for macromelanophores in the platyfish that control the site of production of

large pigment cells, and therefore, indirectly, the site of the melanotic tumors in the hybrids. The object of the present study -was to determine the method of in­ heritance of atypical pigment cell growth among the platyfish-swordtail hybrids, and then to relate the degree of pigmentation to the development of the gonad in the hybrids.

The pituitaries of the hybrids were examin­

ed histologically in order to gain a possible explanation of the incomplete gonad development common among them, and thus to gain some insight into a possible indirect correlation between pigment growth and pituitary struct­ ure.

At the same time statistical analyses of certain taxonomic charac­

ters such as the number of rays in the dorsal fin and the number of scales along the lateral line, were performed as an aid in studies of speciation and evolution in this group of fishes.

Acknowledgments The writer wishes to express her sincere thanks to Dr. Myron Gordon of New York University and the New York Aquarium, New York Zoological Soc­ iety, for his help and encouragement and for his sponsorship of this work. This study, which is part of a project, "Genetic and Correlated is Studies on Normal and Atypical Pigment Cell Growth,"^supported by a grant to the New York Zoological Society from the National Cancer Institute of the U. S. Public Health Service.

The work was done in the Genetics Lab­

oratory of the New York Zoological Society at the American Museum of Nat­ ural History and part in the Genetics Laboratory of New York University. The animals used were obtained from the Genetics Laboratory of the New York Zoological Society.

They were made available through the court­

esy of Dr. Myron Gordon. My thanks are extended to Sam McDowell, T. R. Marcus and M. Glucks-

man for their comments and criticisms, to Sam C. Dunton of the New York Zoological Society for the photographs of the living fish, to Dr. R. Nigrelli of the New York Zoological Society for the photomicrographs, and to Mrs. Nelda Knobloch for the preparation of the figures.

Material and Methods The animals used in this study, Platypoecilus maculatus from the Rio Jamapa and Xiphophorus hellerii from the Rio Papaloapan (Arroyo Zacatispan), in Mexico, were laboratory bred descendants of the wild fishes collected by Gordon, Atz and Gordon in 1939 (Gordon 194-0).

The platyfish and sword­

tail differ in many morphological characters among which are the greater body length of the swordtail, the stouter body form of the platyfish, the greater number of dorsal fin rays in the swordtail, the greater number of scales along the lateral line in the swordtail, and the presence of the "sword" (a prolongation of the ventral rays of the caudal fin) in the male swordtail.

In addition, the platyfish used have a type of sex inheri­

tance in which the male is definitely heterogametic (male XY, female XX). The genetic mechanism for sex determination in the swordtail is indefinite and has not yet been determined. For statistical analyses of some taxonomic characters, 142 male and

86 female platyfish and 62 male and 52 female swordtails were examined. The platyfish came from several different laboratory cultures, some of which were highly inbred, but they were all descendants of those originally collected from the Rio Jamapa.

Two stocks of swordtails were used. The which first was a laboratory culture of inbred fish, strain 3B,^ were the descemdents of those collected from the Rio Papaloapan.

The second and smaller

stock was a stock labeled h36 composed of the Fi intraspecific hybrids of a cross between a Rio Papaloapan swordtail and a Rio Coatzacoalcos swordtail.

Experiment I:

P. maculatus female x X. hellerii male

A platyfish female bearing a spot-side (Sp) gene in one of its X chromosomes, and a dorsal fin spot (Sd) gene in the other X was mated to a swordtail male which carried modifiers of those sex-linked genes for macromelanophores (Gordon 1937).

The results of the cross were reported

by Gordon (1948) as 100 females and 4 males, and since then 6 more males have appeared.

This mating may be expressed as follows:

Female platyfish x male swordtail

*1 46 $?, 5

44 99> 5

(X*)+/(X)g£

(X')+/ W s d

Some of the Fj animals were inbred, and others were backcrossed to either a swordtail or a platyfish.

These matings and their results are recorded

in Table I (Experiments 3 to 6 , 8 to 14).

Experiment 2: X. hellerii female x P. maculatus male A swordtail female was mated with a platyfish male having a stripeside (Sr) gene in its X and an Sd gene in its X chromosome. report of the mating was given by Gordon (1948) as follows:

Female swordtail x male platyfish (X »)+/(X ')+

W s i / (I)Sd n

(X')+/(3C)sr

+

(x«)V(x)sd

A preliminary

Ninety-three per cent of the (X)^.(l)s(j hybrids were sterile; five per cent were fertile males and two per cent were fertile females.

One of these

females was mated with a male of the same genetic constitution as follows:

*1 x

Female (x')+(x)sd

Male (x')+(y)sd

*2 2?o} 2°^

26 not male,ll o Of 535

* A« s ~

A S A !8 £} A 5S A 5S *3 £ M

Of ofIt

M 5J

of .3 n e o n f n o o n 3 •H o a o p

K T Of

m

^3i 32S2a^8|%32g sasaji22

a a s s a a a

«J "®S T3 _ '®S T©g

* S 8 &8 * *°*O f cd Of

a

•p

Of iH

©

•ft T3

2 fl ^ • E3S°

a a

5§|«Si

col col CO| CQ| C0|

£ S5 s. bo a

• til

S.SBBBB&

a Vi

S ^ g j f to

ff\ H

as

b © © © O ©iH Qi Pi +* •p • ©

•p

§ bo CM

0

1

-g s g s-" a

cr>

C*>

«n

so

g) p > © n © I_ § M p

O'

9 iH

H

3

"t

vO

to

cn

4

«n

2o

o n

I

o S5

H S

s|

a

&

I

© b

0

§ n

cm

o o

I m o

cr'ytO

H H

O

■s s pi 4* a K (d © © -P

O O' O' CM 525

d)

i—I

s

0 s 23 ra

o g> m to

O'

to

o O' H

NO

o I —I

ir \

O'

CM

©

e xl

cm

o ca CM

H CM

similar to the so-called residual bodies (multicellular balls formed from degenerating ovocytes and their follicles) found in X. hellerii by Regnier (1938).

The Relationship between Ovarian Development and Distribution of Macromelanophores The numbers of immature and mature ovaries among the F2 and backcross generations are indicated in Table V.

Among the h52 and h6l animals

(Exps. 3 and U) 85°/° of these fish recessive for the macromelanophore genes (X1)

(X1) had mature ovaries.

More than 50°/o of the (X*)+/(X)g^ and

(X*)f/(X) Sd hybrids had mature ovaries.

However, when the Sp and Sd genes

were combined in one animal the number of normal (X)g^(X)gci ovaries in those hybrids fell to 32°/o.

Therefore, there appears to be a definite correla­

tion between the presence of macromelanophores and the absence of mature ovaries (Figure jj.). There were not enough unspotted animals in the other F 2 populations (Exps. 5-7) to justify a correlation analysis.

Among the ani­

mals obtained from the backcross of an Fi hybrid to X. hellerii. 55°/° of the spotted and 7A°/o of the unspotted backcross fish had mature gonads. The difference between the two percentages is statistically significant; therefore, immature gonads are associated with the presence of the Sp gene in this sample.

No data could be gathered from animals derived from a

backcross of an F]_ to a platyfish for this correlation because all the fishes had macromelanophores. It seemed probable that the above correlations were the secondary result of another relationship, namely a correlation between the degree of pigment cell growth and egg development.

Table VI outlines the associa­

tion between the degree of pigmentation and the relative maturity of the ovary in the F 2 hybrids and those of the two backcross generations.

The

Table V Relationship of Macromelanophore Pattern to Gonad Development in Platypoecilus maculatua-XiphoPhorus hellerii Hybrids (Regrouped from Table I) Exp. No. Culture

3, 4

(PXr h52, h6l

(XP)2 h74 (PX)2 h66 (PX)2 h53 8

PX-X

h68

10,11,12 PX-nP h54,h57,h70 h71,h?2 13, U

PX XP (PX)2 (XP)2 PX-X PX-P Sp+.SpSp Sd+.SdSd Sr» SdSp

Genotype ++ Spf Sd+ SdSp 44

No. Spec- Without Immature Matui linens Gonad 9 Gonad 9 G01

82

1 26

5 27

67

17

260

22 66

16 22 80

9

10

4

1

4 19

42

23

++ Sp+.SpSd

5 48

++ Sd-t-.SdSd

1

SrwSr+ SdSp SdSr SfSp

114

2

Sd+,SdSd

-HSp+

36 29 34

43

2

5

24

1 7

15

21

51

9

11

31

121

2k

hk

SI

172

33

55

84

28 37 28 39

1

6

21

5

32

6 8 6

21

6 138

1 ~2

31

Fx hybrid of a P. maculatus $ and an X. hellerii Fx hybrid of an X. hellerii $ and a P. maculatus