Agassizia excentrica A. Agassiz, 1869

Gondim, Anne Isabelley, Moura, Rafael Bendayan De, Christoffersen, Martin Lindsey & Dias, Thelma Lúcia Pereira, 2018, Taxonomic guide and historical review of echinoids (Echinodermata: Echinoidea) from northeastern Brazil, Zootaxa 4529 (1), pp. 1-72 : 46

Agassizia excentrica A. Agassiz, 1869

Figure 16 A–G

Agassizia excentrica A. Agassiz, 1869: 276 , pl. 11, figs 23–24.― Tommasi, 1972: 32 –33, fig. 66.― Manso, 2004: 21, fig. 2af.― Magalhães et al., 2005: 63.― Ventura et al., 2007a: 352.― Manso et al., 2008: 184 –185, figs 6e–f.― Oliveira et al., 2010: 11.

Material examined. Bahia: 1 spm, 12°56′13″S 38°33′55″W, 56 m [UFBA00369]; 2 spms, Busca Vida Beach, Guarajuba, Camaçari, I.2010, 37 m [UFBA01195]; 1 spm, Busca Vida Beach, Guarajuba, Camaçari, II.2008, 45 m [UFBA01196]; 2 spms, Busca Vida Beach, Guarajuba, Camaçari, II.2011, 37 m [UFBA01304]; 1 spm , Baía de Camamu [UFSITAB-124]; 1 spm, without locality data, 07.XII.1978 [ MZUSP, without voucher]; 1 spm, without locality data [ MZUSP, without voucher] .

Description. Test small, oval or rounded, covered by long, slender, vitreous spines (TL = 7.4 to 15.3 mm; TH = 5.3 to 11 mm; TW = 6 to 13 mm) ( Fig. 16 A–C). Apical system ethmolytic, displaced towards posterior region of test ( Fig. 16A, D, G ). Four gonopores, posterior pores subtly larger than anterior pores ( Fig. 16G ). Ambulacrum III weakly depressed, with very small podial pores ( Fig. 16A, D ). Ambulacra II and IV weakly sunken, with two columns (one is rudimentary) of pore-pairs and three times longer and slightly slenderer than ambulacra I and V ( Fig. 16A, D ). Ambulacra I and V slightly more sunken than anterior paired ambulacra (II and IV), with equally developed columns of pore-pairs ( Fig. 16A, D ). Peripetalous fasciole well-developed and adjacent to paired petals (I, II, IV and V) ( Fig. 16A, C, D ). Lateroanal fasciole present ( Fig. 16C, F ). Cluster of long spines close to periproct. Periproct circular and longitudinal ( Fig. 16D ), covered by plates of variable sizes and shapes, larger plates close to edge and smaller plates towards center. Peristome large, D-shaped, covered by many plates ( Fig. 16B, E ). Labrum short and wide ( Fig. 16E ), in broad contact with sternal plates, and not projecting strongly towards peristome. Amphisternous plastron, with many primary tubercles. Plastron spines large and spatulate ( Fig. 16B, E ). Crenulate and perforate tubercles ( Fig. 16 D–F). Aboral tuberculation fine, uniform, and dense ( Fig. 16D ). Oral tubercles also dense and uniform ( Fig. 16E ). Tube feet with spinules of variable shapes.

Pedicellariae. Ophicephalous pedicellariae distributed over entire test. Ophicephalous pedicellariae short and without a neck. Valves short, proximal region large, blade narrow with denticulate margin, which enlarges towards the tip, forming a foramen with denticulate margin.

Colour. Spines pinkish gray, darkest at the bases, in living specimens ( A. Agassiz 1883). Yellowish in alcohol. Naked test white.

Distribution. Florida, Gulf of Mexico, Mexico, Belize, Bahamas, Barbados, Cuba, Dominican Republic, Trinidad and Tobago, Honduras, Puerto Rico, Nicaragua, Panama, Colombia, Venezuela, Guyana, and Brazil (A.H. Clark et al. 1921; Tommasi 1972; Borrero-Pérez et al. 2002, 2012; Alvarado et al. 2008; Solís-Marín et al. 2013). In Brazil from BA ( Manso 2004). From depths of 43 to 900 m ( Pawson et al. 2009).

Remarks. The genus Agassizia presently consists of only two extant species [ A. excentrica and A. scrobiculata Valenciennes, 1846 ] ( Kroh & Mooi 2016). Agassizia excentrica is the only species in the genus recorded from the Atlantic Ocean. A. Agassiz (1869), in the original description, says that he was not sure that his specimen did not belong to A. porifera ( Ravenel, 1848) (fossil). Nevertheless, A. Agassiz (1869) presented a brief description of his new species and the features he used to distinguish it from other known species at that time, but did not provide illustrations. Although A. excentrica is well established taxonomically, a reanalysis of its type series and a redescription of this species is still needed. Few individuals were analyzed in the present paper, all of which were similar in size and without observed variations. A. Agassiz (1883, 1904) provided an extended discussion on the ontogenetic development of morphological characters of A. excentrica .

Ecological notes. Agassizia excentrica lives buried in sandy or sand-mud substrates. According to Lewis (1963), this species appears to have typical bottom feeding habits and ingests loose bottom material at random. This is a very rare species for which data on ecology and evolutionary biology are scarce. Along the Brazilian littoral, it has been found in fine sediments together with the ophiuroids Microphiopholis atra ( Stimpson, 1854) , Amphioplus camamuensis Manso, 2004 and Amphiodia pulchella ( Lyman, 1869) ( Manso 2004; Manso et al. 2008).

Figures

FIGURE 16. Morphological characters of Agassizia excentrica (MZUSP, without voucher). (A) Aboral view; (B) Oral view; (C) Lateral view; (D) Aboral view of naked test; (E) Oral view of naked test; (F) Lateral view of naked test; (G) Apical system.