Editorial Type:
Article Category: Research Article
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Online Publication Date: Jan 01, 2000

Freshwater Cichlid Crenicara punctulata Is a Protogynous Sequential Hermaphrodite

Page Range: 71 – 82
DOI: 10.1643/0045-8511(2000)2000[0071:FCCPIA]2.0.CO;2
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Abstract

Several papers have suggested that the Freshwater Cichlid Crenicara punctulata is capable of protogynous sex change. These studies provide behavioral data and descriptive details of external morphology but lack information about gonadal histology, which is essential for definitive evidence of sequential hermaphroditism. Therefore, this study was designed to determine whether C. punctulata is a sequential hermaphrodite. The present study included a behavioral experiment, an isolation/transformation experiment, as well as a detailed analysis of gonadal structure. The behavioral experiment established social hierarchies in four groups of juvenile female C. punctulata. The hypothesis that the dominant female in each group would be the only individual to develop male secondary sexual characteristics in that group was verified. The isolation experiment tested the hypothesis that female C. punctulata would change sex without the presence of conspecifics. After social isolation, females that were previously dominant among a group of females in a male harem developed male secondary sexual characteristics. Histological analysis revealed that these individuals possessed testes, whereas all dominant females examined possessed mature ovaries. The results from behavioral, isolation, and histological portions of this project strongly suggest that C. punctulata is a protogynous sequential hermaphrodite, at least in captivity.

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Copyright: The American Society of Ichthyologists and Herpetologists
Fig. 1.
Fig. 1.

Displays of aggressive behaviors observed in Crenicara punctulata (adapted from Zupanc, 1988). Individuals with the solid black line are the aggressors, and individuals with the checkerboard pattern are the submissive members of the pair

Fig. 2.
Fig. 2.

Mean (± SE mean) number of chases per hour by Crenicara punctulata. The fish occupying position 1 were the dominant individuals in each social hierarchy (n = 4); position 2 fish were the next most dominant individuals (n = 4); position three fish were the third dominant fish; and position 4 fish were the most subordinate individuals. A significant difference existed among a, b, and c [F(3,11) = 154.63, P < 0.0001; Student Newman Keul's test, P < 0.05]

Fig. 3.
Fig. 3.

Mean (± SE mean) number of tail-nips per hour by Crenicara punctulata. The fish occupying position 1 were the dominant individuals in each social hierarchy (n = 4); position 2 fish were the next most dominant individuals (n = 4); position 3 fish were the third dominant fish; and position 4 fish were the most subordinate individuals. A significant difference existed among a, b, and c [F(3,11) = 54.23, P < 0.0001; Student Newman Keul's test, P < 0.05]

Fig. 4.
Fig. 4.

Average lengths for three groups of Crenicara punctulata that began the isolation experiment as dominant fish (group 1, open squares, middle line), subordinate fish (group 2, open circles, bottom line), or males (group 3, closed squares, top line). The measurements are for weeks 0, 4, 8, 12, 16, and 20. There was a significant difference in the length among groups [F(2,48) = 321.53, P < 0.0001] and for the week difference among groups [F(5,48) = 35.57, P < 0.0001]. The interaction F [F(19,48) = 0.102, P < 0.9997] did not indicate a significant difference; therefore, sex change was not accompanied by a change in growth rate

Fig. 5.
Fig. 5.

Gonads from Crenicara punctulata reflecting differences in morphology and size. The ovaries are from a subordinate female (fish 7) and a mature dominant female (fish 5); the testes are from an individual that began the isolation experiment as a dominant fish (fish 3) with female coloration and developed male coloration after eight weeks in isolation

Fig. 6.
Fig. 6.

(A) Ovary from a subordinate female that remained in isolation for five months. The ovary contains previtellogenic oocytes of small size (e.g., O), some oocytes showing the early signs of vitellogenesis, as well as blastema tissue (BL) located near the ovarian blood supply (BS). Bar = 30 µm. (B) Blastema tissue (BL) in the rostral end of a mature subordinate female ovary. Note the previtellogenic oocytes (e.g. O). Bar = 30 µm

Fig. 7.
Fig. 7.

(A) A dominant female ovary containing follicles undergoing atresia. The zona radiata (Z) has begun to retract from the follicle wall. A collapsed atretic follicle is present (A) and is located near a yolking oocyte (Y). Bar = 30 µm. (B) Blastema tissue (BL) with gonial nest (G) in a mature dominant female ovary. Capillaries (C) are located in close proximity to both the gonial nest and blastema tissue. Bar = 30 µm

Fig. 9.
Fig. 9.

Testicular tissue from a fish that began isolation as a dominant fish with female coloration. Spermatogenesis is occurring and spermatogonia and spermatids are present (S), but no sperm have developed. One pocket of blastema tissue (BL) is located near a testicular vein, but no oocytes are present in the entire gonad. Bar = 30 µm

Fig. 8.
Fig. 8.

(A) Blastema tissue (BL) in the ovary of a mature dominant female. Surrounding the blastema tissue is yolk (Y) from an atretic follicle that has ruptured. Bar = 30 µm. (B) Blastema tissue (BL) located near a healthy previtellogenic oocyte (O) in a mature, dominant female ovary. Bar = 30 µm

Accepted: Jun 22, 1999