Aspects of oophagyin Alopiasvulpinus (Elasmobranchii, Alopiidae) in the southern Brazil

doi:10.15406/ijh.2018.02.00075

International Journal of

eISSN: 2576-4454

Hydrology

Research Article Volume 2 Issue 2

Aspects of oophagyin Alopiasvulpinus (Elasmobranchii, Alopiidae) in the southern Brazil

Malavasi Bruno CE,¹

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Alberto Ferreira de Amorim²

¹Department of Surgery, Faculty of Veterinary Medicine and Animal Science, University of São Paulo, Brazil
²Instituto de Pesca, Agência Paulista de Tecnologia dos Agronegócios, Brazil

Correspondence: Alberto Ferreira de Amorim, Instituto de Pesca, Agência Paulista de Tecnologia dos Agronegócios, Brazil

Received: February 21, 2018 | Published: April 25, 2018

Citation: Malavasi-Bruno CE, Amorim AF. Aspects of oophagyin Alopiasvulpinus (Elasmobranchii, Alopiidae) in the southern Brazil. Int J Hydro. 2018;2(2):240-241. DOI: 10.15406/ijh.2018.02.00075

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Abstract

Oophagy of the genus Alopiaswas described by several authors, nevertheless, this paper presents some new aspects of the oophagy of A. Vulpinus.¹ Four embryos of A. vulpinus, being three males with total lengths of 115.5cm (3.2kg), 116.5cm (3.6kg), and 118.8cm (3.3kg), and a female with 118.6cm (3.0kg), were obtained from a female caught by Brazilian artisanal fishing using in shore gillnet at a depth of 4.5m off Peruibe City, Sao Paulo State, Brazil in November, 2007. Five oocytes were integer, and the size ranged from 67 to 71mm.This study found clear evidence that embryos of A. vulpinus ingest the whole oocyte. No traces of smaller siblings were found in the four embryos stomachs, so the species probably do not perform adelphophagy.

Keywords: common thresher shark, food of embryos, oocytes, matrotrophic viviparity

Introduction

Oophagy is a form of matrotrophic viviparity where, after initial yolk-sac nutrition, developing embryos ingest unfertilized eggs to support further development. The Lamniformes sharks are oophageal.^2‒7 The oophagy in the Lamniforms, throughout most of their pregnancy, mothers continuously produce unfertilized eggs which the developing embryos ingest and store in a large bulging yolk stomach⁷ According to Cadenat⁴oocytes are consumed by the developing embryos. This has been confirmed by Okate & Mizue⁸ for A pelagicus, by Gilmore⁹ & Moreno, Moron¹⁰ for A superciliosus, and Gubanov^11,12 for Alopiasvulpinus. This brief communication records the occurrence of integer oocytes in stomachs of Alopiasvulpinus embryos.

Material and methods

Four embryos of Alopiasvulpinus obtained from a pregnant female caught in November 2007 by Brazilian artisanal fishermen using gillnet at 4.5m depth off Peruibe City, Sao Paulo State, Brazil were donated to Fishery Research State Instituto “Instituto de Pesca” (Figure 1). The embryos were identified and measured according to Compagno¹³ and weighed with digital scale, in grams. The embryos had integer oocytes in their oral cavity were placed upside down to remove them and also had the stomachs opened.

Figure 1 Maps of peruibe city, Sao Paulo State, Brazil.

Results and discussion

Four embryos of A. Vulpinus were obtained from a female caught being three males with total lengths of 115.5 cm (3.2kg), 116.5cm (3.6kg), and 118.8cm (3.3kg), and one female with 118.6cm (3.0kg). According to the characteristics of pigmentation, aspects identical to adult and embryo size were in the athermal stage, based on Bigelow & Schroeder¹³ ranging from 114 to 159cm. The embryos were probably performing oophagy and close to birth. Some embryos from 116.5 to 124cm were observed in November 2004 and newborn and juveniles are reported in shore waters from April to July.¹⁴ In Southern Brazil it was observed the presence of pregnant female, neonate and juvenile of Alopiasvulpinus, from December to March.^14,15 One male embryo had an integer oocyte in the oral cavity and in order to extract it the embryo was placed upside down. In addition to this oocyte, three others dropped from his stomach. The same procedure was done for the others and one more oocyte fell from the female (Figure 2). Fiveoocytes were integer, and the size ranged from 67 to 71mm. In addition, all the embryos' stomachs were opened observing a net mass of oocyte. This fact suggests that the embryos swallowed integer oocytes as a food source. According to Moreno et al.¹ The teeth can remain embedded or hidden until shortly before birth. Therefore, the oocyte capsule even being eaten did not break. Some authors as Shann,² Springer,³ Cadenat,⁴ Gilmore⁵ and Hamlett⁷ mentioned the oophagy in Lamniformes. According to Gubanov¹¹A. vulpinus young fetus after resorption of their primitive yolk reserves absorbed eggs at the time of their descent into the oviduct, so the stocks of nutrients enable them to continue their development in the mother uterus without any connection with uterine walls and without specialized system enabling the absorption of nutritive juices thereof. Nevertheless this author did not mention anything about how embryo can ingest the oocyte. Moreno et al.¹ studied the reproductive biology and phenology of A. Vulpinus caught at some areas of Mediterranean and Atlantic oceans, giving, among others, information about size and morphology of embryos. Nevertheless, it has not been demonstrated as the ingestion of egg capsule occurs. This study found clear evidence that embryos of A. vulpinus of 115.5cm or larger ingest the whole oocyte. Capsule was whole in the stomach of the fish with out chewing, demonstrating that the rupture occurs in the stomach, characterizing the mode of ingestion.The absence of smaller siblings or parts of it in the stomach of the embryos suggests that the species does not perform adelphophagy.

Figure 2 Alopiasvulpinus: (A) Exemplar upside down for expulsion of the oocytes from the mouth; (B) Oocyte and embryo; (C) Integer oocyte and broken capsule; and (D) Four embryos of A. vulpinnus.

Conclusion

This study found clear evidence that embryos of A. vulpinus of 115.5cm or larger ingest the whole oocyte. The absence of smaller siblings or parts of it in the stomach of the embryos suggests that the species does not perform adelphophagy.