Life history of a simultaneously hermaphroditic fish, Diplectrum formosum

Abstract

Sand perch Diplectrum formosum were collected in the Atlantic Ocean waters off the south-eastern U.S. for life history analyses between April 2001 and July 2004 and ranged in size from 63 to 236 mm standard length (L(S)) and 0-8 years of age. Diplectrum formosum are simultaneous hermaphrodites that reach 50% sexual maturity at 12.2 months and 122.8 mm L(S) for testicular tissue and 13.6 months and 129.3 mm L(S) for ovarian tissue. The gonad contains ovarian and testicular tissue separated by a thin basement membrane, with no means of internal self-fertilization. Spawning females were found between March and January with a peak of spawning activity in May and a realized spawning periodicity of 2 days, equivalent to a maximum of 168 spawning events per year. Fish with testicular tissue in spawning condition were obtained throughout the year in every month sampled with a maximum frequency between June and September. There were also trends indicating that testicular tissue was more likely to be in spawning condition in the presence of hydrated oocytes within the accessory structure. This may indicate the use of the accessory structure as a storage site for hydrated oocytes until a mate can be located.

Diplectrum radiale (Quoy & Gaimard, 1824) (Serranidae): A rare case of simultaneous hermaphroditism in a teleost fish

“…The main characteristic of this genus is the presence of an accessory reproductive structure (ovarian sinus) whose function is to store hydrated oocytes. This structure has been reported for D. rostrum , D. pacificum , D. bivittatum and D. formosum (Bortone, , ,b; Bubley & Pashuk, ; Touart & Bortone, ). The species D. radiale is found inhabiting coastal and estuarine areas of the eastern and north‐east coasts of South America at depths of up to 60 m, may reach 250 mm in total length and feeds on crustaceans and small fish, playing an important role in the structure of ecosystems (Bortone, ; Carpenter, ).…”

“…The simultaneous occurrence of postovulatory follicles at different stages and the ovarian sinus filled only with hydrated oocytes found in the present study corroborate the hypothesis of oocyte storage, indicating that the hydrated oocytes were stored in the accessory reproductive structure of D. radiale for at least 24 hr. To date, no atretic oocyte has been recorded in the ovarian sinus of Diplectrum spp., contradicting the theory of oocyte resorption (Bubley & Pashuk, ; Touart & Bortone, ). However, in the present study, atretic hydrated oocytes were found within the ovarian sinus, revealing that the villi‐like projections may also reabsorb the unspawned oocytes, as stated previously by Bortone (), or that atretic hydrated oocytes would be eliminated in the next spawning event.…”

“…Diplectrum radiale is a synchronous hermaphrodite, and the simultaneous occurrence of spermatozoa, hydrated oocytes and postovulatory follicles indicates that both gametes are clearly functional; that is, both types of matured gametes are ready for fertilization. However, the testicular and ovarian tissues were separated from each other by different ducts, indicating a little possibility of internal self‐fertilization, but the external self‐fertilization may occur, as observed in the ovotestes of D. formosum by Obando and León (), and Bubley and Pashuk ().…”

“…This same author and Touart and Bortone () have also reported a positive PAS reaction of the “villae” in the ovarian sinuses of D. pacificum and D. bivittatum , indicating presence of a mucuslike substance. The villi structures are composed of secretory epithelium, and the mucuslike substance creates the appropriate conditions for storage of the hydrated oocytes (Bubley & Pashuk, ); moreover, this substance could also facilitate the movement of the hydrated oocytes through the sinus and oviduct, assist in the adhesion of spermatozoa in the external environment and hold the hydrated oocytes together after spawning (Touart & Bortone, ).…”

“…This same author and Touart and Bortone (1980) have also reported a positive PAS reaction of the "villae" in the ovarian sinuses of D. pacificum and D. bivittatum, indicating presence of a mucuslike substance. The villi structures are composed of secretory epithelium, and the mucuslike substance creates the appropriate conditions for storage of the hydrated oocytes (Bubley & Pashuk, 2010); moreover, this substance could also facilitate the movement of the hydrated oocytes through the sinus and oviduct, assist in the adhesion of spermatozoa in the external environment and hold the hydrated oocytes together after spawning (Touart & Bortone, 1980). The simultaneous occurrence of postovulatory follicles at different stages and the ovarian sinus filled only with hydrated oocytes found in the present study corroborate the hypothesis of oocyte storage, indicating that the hydrated oocytes were stored in the accessory reproductive structure of D. radiale for at least 24 hr.…”