Determination of limited histotrophy as the reproductive mode in <i>Mustelus schmitti</i> Springer, 1939 (Chondrichthyes: Triakidae): analysis of intrauterine growth of embryos

Orlando, Luis; Pereyra, Inés; Silveira, Santiago; Paesch, Laura; Oddone, Maria Cristina; Norbis, Walter

doi:10.1590/1982-0224-20150001

Luis Orlando

Laboratorio de Fisiología de la Reproducción y Ecología de Peces, Facultad de Ciencias, Iguá 4225, Montevideo, Uruguay. (LO) lorlandoch@gmail.com (corresponding author)

UNDECIMAR, Facultad de Ciencias, Iguá 4225, Montevideo 11400, Uruguay.

Inés Pereyra

Área de Biodiversidad y Conservación, Museo Nacional de Historia Natural, 25 de Mayo 582, 11000, Montevideo, Uruguay.

Santiago Silveira

Departamento de Biología Poblacional, DINARA - MGAP. Montevideo, Uruguay, Constituyente 1497, C. P. 11200 - Caixa Postal 1612, Montevideo, Uruguay.

Laura Paesch

Departamento de Biología Poblacional, DINARA - MGAP. Montevideo, Uruguay, Constituyente 1497, C. P. 11200 - Caixa Postal 1612, Montevideo, Uruguay.

Maria Cristina Oddone

Instituto de Ciências Biológicas, Setor de Morfologia, Universidade Federal do Rio Grande, Avenida Itália, Km 8, Campus Carreiros, 96203-900 Rio Grande, RS, Brazil.

Walter Norbis

Laboratorio de Fisiología de la Reproducción y Ecología de Peces, Facultad de Ciencias, Iguá 4225, Montevideo, Uruguay. (LO) lorlandoch@gmail.com (corresponding author)

Departamento de Biología Poblacional, DINARA - MGAP. Montevideo, Uruguay, Constituyente 1497, C. P. 11200 - Caixa Postal 1612, Montevideo, Uruguay.

Figures (3)
Tables (3)

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Fig 1
Mean embryo total length and standard deviation as a function of the ordinal day of the year considering the two consecutive years (2006 and 2007) for Mustelus schmitt i embryos. Dashed line represents the linear model adjusted to the individual data, continuous line is for the Gompertz model and the pointed line represents the Von Bertalanffy growth curve.

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Fig 2
Mean yolk mass and standard deviation as a function of the ordinal day of the year considering the two consecutive years (2006 and 2007) for Mustelus schmitt i embryos. Using the same y axis values the continuous line represents the logistic curve adjusted for presence/absence of yolk sac, the probability of an embryo having external yolk sac is given by Yt=1/(1+e(-13.749 + 0.072*t)) for 2006 and Yt=1/(1+e(-10.472 + 0.054*t)) for 2007.

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Fig 3
Relationship between total dry weight (g) (Mustelus schmitti embryos and its yolk sac) and time (ordinal days), along 2006 and 2007. The bottom and top of the box are the first and third quartiles, and the band inside is the median, the ends of the whiskers represent the range of the distribution. This graphic shows a clear increase in mass that has been associated with matrotrophy.

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Table 1
Overview of the data set used for this study detailing: Date of sampling, number of embryos per sampling event and the proportion of female embryos of Mustelus schmitti in the catch (*indicates significant differences from the ratio 1:1 on a chi-square test).

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Table 2
Continuous and segmented linear regressions applied to length and mass data for Mustelus schmitti embryos. The "Variables" column show the independent and dependent variables and its transformation, Total mass includes the internal and external yolk sac and the embryo, while Embryo mass includes the embryo without the external yolk sac. When a segmented linear regression was applied a Slope 2 and a breakpoint value with its error are shown.

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Table 3
Growth curves adjusted to total length data (TL) of Mustelus schmitti for each year of the study. In "Equation" t is the ordinal day of the year. Within years "Parameters" show the estimations made by least square, the asterisks denote the level of confidence of such estimations: *** p<0.001, ** p<0.01, no asterisks means p>0.05. "r2" is the quasi-r squared score, and "AIC" is Akaike's information criteria.

Date	Embryos (n)	% Females
30/05/06	91	52
06/07/06	25	56
04/08/06	62	54
15/09/06	13	54
08/10/06	17	38*
29/11/06	11	45
18/05/07	66	44
26/06/07	54	43
31/07/07	20	45
23/10/07	70	46
26/11/07	30	31*

Variables		Year	Intercept	Slope 1	Slope 2	Break Point	r²
log(Total Mass)	log(Total Length)	2006	-3.15	2.00	3.43	2.79 +- 0.015	0.97
log(Total Mass)	log(Total Length)	2006	-5.19	2.77	---	---	0.95
log(Embryo Mass)	log(Total Length)	2006	-4.39	2.45	3.45	2.80 +- 0.022	0.98
log(Embryo Mass)	log(Total Length)	2006	-5.77	2.97	---	---	0.97
log(Total Mass)	log(Total Length)	2007	-2.20	1.66	2.96	2.68 +- 0.022	0.97
log(Total Mass)	log(Total Length)	2007	-4.96	2.72	---	---	0.97
log(Embryo Mass)	log(Total Length)	2007	-4.04	2.34	3.00	2.69 +- 0.044	0.98
log(Embryo Mass)	log(Total Length)	2007	-5.42	2.87	---	---	0.98

Model	Equation	2006			2007
Model	Equation	Parameters	r2	AIC	Parameters	r2	AIC
Linear	TL= a + b*t	a = 7.243***	0,6	991,0	a = 7.492***	0.78	999,0
Linear	TL= a + b*t	b = 0.051***			b = 0.050***
Von bertalanffy	TL= Linf(1-e(k* (t-t0)))	Linf = 29.986***	0,6	989.6	Linf = 25.729***	0.80	979.7
		k = 0.004**			k = 0.008***
		t0 = -0.064			t0 = 40.277**
Gompertz	TL= Linf(-b(-k*t))	Linf = 27.735***	0,6	990.7	Linf = 24.742***	0.80	980.9
		b = 1.807**			b = 2.628***
		k = 0.007***			k = 0.011***

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Determination of limited histotrophy as the reproductive mode in Mustelus schmitti Springer, 1939 (Chondrichthyes: Triakidae): analysis of intrauterine growth of embryos

ABSTRACT