Reproductive anatomy, gonad development and spawning seasonality of nurseryfish, Kurtus gulliveri (Perciformes : Kurtidae)
T. M. Berra A E , B. Gomelsky B , B. A. Thompson C and D. Wedd DA Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Mansfield, OH 44906, USA.
B Aquaculture Research Center, Kentucky State University, Frankfort, KY 40601, USA.
C Coastal Fisheries Institute, Louisiana State University, Baton Rouge, LA 70803, USA.
D Parks and Wildlife Commission of the Northern Territory, Territory Wildlife Park, PO Box 771, Palmerston, NT 0831, Australia.
E Corresponding author. Email: berra.1@osu.edu
Australian Journal of Zoology 55(4) 211-217 https://doi.org/10.1071/ZO07033
Submitted: 15 January 2007 Accepted: 28 May 2007 Published: 24 September 2007
Abstract
The nurseryfish, Kurtus gulliveri, of northern Australia, is remarkable for the fact that the males carry the egg mass on a supraoccipital hook on their forehead. Plankton samples of larval nurseryfish indicate a prolonged spawning season (June–November) that more or less corresponds with the dry season in the Northern Territory. The paired, elongate testes are located in the posterior portion of the body cavity suspended by the mesorchium. The gonadosomatic index (GSI) of males was small and highly variable (mean 0.14, range 0.01–0.27) from June to November. The histological structure of testicular lobes showed maturing and mature stages that contained spermatocytes, spermatids, and spermatozoa. The paired, bean-shaped ovaries contained about 5500 oocytes (1176–9783) and were located in the rear of the abdominal cavity. GSI averaged 1.58 (range 0.36–4.48). Ovarian histology revealed primary growth, cortical alveolar oocytes, vitellogenic oocytes, coalesced yolk, and atresia. The occurrence of postovulatory follicles and late vitellogenetic oocytes in the ovaries clearly indicate that nurseryfish females are batch spawners. Maturing testes showed signs of previous spawnings indicating that males are capable of spawning several times throughout the spawning season. We speculate that nurseryfish may spawn in a manner similar to their closest relatives, cardinalfishes (Apogonidae), with eggs carried on the male’s hook instead of orally.
Acknowledgements
Fieldwork was supported by small grants from the National Geographic Society (No. 6895-00, No. 7550-03), the Columbus Zoo and Aquarium, Bioscience Productions, the College of Biological Sciences of The Ohio State University, and the Mansfield Campus of OSU to TMB. Q. Allsop provided field assistance. TMB is Research Associate of the Museum and Art Gallery of the Northern Territory, and the cooperation of museum personnel made the project possible. The logistic support of the Territory Wildlife Park and the N.T. Fisheries Research Laboratory is greatly appreciated. This research was carried out under Special Permit No. 2000-2001/S17/1521, No. 2003-2004/S17/1521 and No. 2005/S17/1521 from the Director of Fisheries of the Northern Territory to TMB. All institutional animal ethics protocols were carried out. The authors thank S. Mims, B. Wilhelm and K. Schneider for the help in fish dissecting and histological processing of testes samples. We are grateful to M. Wiredu for patiently counting oocytes. Preparation of ovarian slides, including washing, embedding, sectioning, and staining were completed by the Louisiana State University School of Veterinary Medicine, Department of Pathology. For this assistance we thank C. Crowder and her staff. We thank D. Nieland for discussions on interpretations of the nurseryfish’s ovarian histology and J. Blackburn for computer assistance with the preparation of Fig. 3. M. Persinger produced Fig. 4 from our raw data, and M. Collura arranged Fig. 2. A. Vagelli made valuable comments on a draft of the manuscript. We dedicate this paper to the memory of our coauthor, Bruce Thompson, who passed away on 5 January 2007.
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