Schizocardium peruvianum Spengel, 1893

Cameron, C. B. & Perez, M., 2012, Spengelidae (Hemichordata: Enteropneusta) from the Eastern Pacific including a new species, Schizocardium californicum, from California, Zootaxa 3569, pp. 79-88 : 81-83

Schizocardium peruvianum Spengel, 1893

( Figs. 1, 2A–G)

Material examined. The description given below is based on two anterior fragments, one collected from Pisco, Peru by Waldo Schmitt of the U.S. National Museum in 1935 and the other from Point Mugu, California by Theodore H. Bullock of the Scripps Institution, University of California, in 1947. The latter is the paratype. Additional specimens from Independence Bay, Pisco, Peru were collected and photographed by Giannina Passuni in 2006 ( Fig. 1). We serially sectioned one of Passuni’s specimens to compare with the specimens of Waldo and Bullock, and found no significant differences with the Waldo specimen. This description supplements the account given by Spengel (1893). Spengel’s single specimen came from Pisco, Peru (Lat. 13º45' S, Long. 76º20'W), Schmitt and Passuni’s from Independence Bay, Pisco, Peru in 40 m and 35 m depth in 1935 and 2006; T.H.B.’s from Mugu Lagoon, California, (Lat. 34º7'N, Long. 119º6'W) in 1947. At Mugu it was in mud exposed at low tide, with Macoma, Polinices, Amphitrite, Bulla and Dendraster . Paratype (Bullock’s specimen 540-1.1 to 540-1.127). Catalogue no. NMNH: USNM 1177534 [ IZ].

External features. This is a rather large species. Our incomplete Mugu specimen ( T.H.B. accession no. 382) measured in life 285 mm through the anterior abdominal region. The proboscis is 15 mm long and 10 mm wide at the widest point; the collar 5 mm long and 7 mm wide; the branchial region 72 mm; the genital region overlapping with the branchial and beginning 3 mm behind the collar extends for at least 165 mm; the hepatic region begins 152 mm behind the collar and extends 45 mm. The proboscis is sharply pointed and has prominent middorsal and midventral grooves when relaxed. The genital folds are thick and stubby. T.H. Bullock observed this specimen shed sperm in thick milky streams from many places along the genital region (March 22, 1947).

The colour is notable ( Fig. 1). The proboscis is reddish orange, not pale but rather dark; the collar is the same but darker—almost blood red; the trunk is the same but no darker than the proboscis except the hepatic caeca which are brown and the genital wings which are red where the skin is not too thin, yellow-orange where the gonads show through in patchy pseudosegmental folds. The terminal abdomen is pale yellow brown except for a midventral strip of bright orange.

Internal features. The proboscis epidermis is rather thick being about 200 to 300 µm. The nerve fiber layer may be thickened middorsally especially in the posterior region. The circular muscle fiber layer is conspicuous, comprising several layers of muscle fibers. The longitudinal musculature is also well developed in the proboscis. There is a strong dorsoventral muscle plate ( Fig. 2A). The vermiform process of the stomochord is rather long, extending anteriorly just into the anterior one-third of the proboscis. The ventral septum reaches anteriorly to the tip of the vermiform process, but posteriorly it does not extend to the posterior wall of the ventral coelom. The pair of tubular extensions of the cardiac vesicle extend anteriorly a little beyond the stomochord proper, but not to the same extent as the vermiform process. Anteriorly each half of the glomerulus surrounds the tubular extension of the cardiac vesicle of its side ( Fig. 2B). The glomerulus of the right and left side may or may not be continuous anteriorly. The two tubular extensions of the cardiac vesicle may be connected and continuous anteriorly at their tip (Passuni’s Peru specimen) or they may be completely separate (Spengel’s specimen and the Mugu specimen). Stomochord may have a continuous and spacious lumen (Spengel’s specimen and Mugu specimen) or the lumen may be broken up at the tip of the stomochord and in the neck ( Fig. 2B–C). Only a left proboscis coelomic canal opens by a left proboscis pore ( Fig. 2C). The cardiac vesicle is quite roomy. The proboscis skeleton has a pronounced keel that may be sharp and deep (Spengel and Passuni specimens) or it may be large, conspicuously broad as well as deep (Mugu specimen). The end plate of the skeleton may be flat (Mugu specimen) or it may bear an anteriorly directed obtuse protuberance middorsally ( Peru).

Both the dorsal and ventral mesenteries of the collar may be complete or one of the two may not reach fully to the anterior margin of the collar. The perihaemal cavities extend up to the proboscis canal in the peduncle and are confluent at their anterior ends ( Fig. 2D). An anterior neuropore is present in the face of the collar. The collar nerve cord has no lumen or lacunae. The skeletal cornua extend over nearly four-fifths of the collar length. A posterior neuropore is present in the specimen from Peru, but in the material from Mugu, the ‘neural tube’ appears to continue for over 3 mm into the anterior part of the trunk region, immediately posterior to the collar. It is not clear whether this is due to the accidental fusion of the epithelia in the middorsal region resulting from maceration and poor preservation or whether it is real and anatomical. The collar canals and pores are as described by Spengel (1893), with a deep dorsal fold appearing like a large tongue ( Fig 2E). Peribuccal cavities are present but confined to the posterior quarter of the collar.

The pharynx shows a morphology characteristic of the genus. There is a well developed epibranchial ridge (Fig, 2F), a possible homologue with the chordate endostyle (Ruppert at al, 1999) and the ventral pharynx is reduced to a narrow hypobranchial slit (Fig. G). Each gill has about 30 synapticula.

Remarks. S. peruvianum is anatomically very similar to S. brasiliense . The major anatomical differences between the two species occur with regard to the stomochord and the proboscis skeleton. In the former species the skeleton is conspicuous with a great keel while in the latter it is short with small body and broad, blunt keel. Likewise in the former species the neck of the stomochord is flat and continuous whereas in S. brasiliense , the stomochordal neck is narrow and much reduced and may sometimes be broken up. The other feature of difference is the absence of an anterior neuropore in S. brasiliense .

Externally these two species differ in a few features like the difference in the shape of the collar. As has been pointed out in the description of the species, there are a few differences between the Peru and the Mugu specimens. These differences are not sufficiently great to create a new species. Examination of more specimens from these two localities may change this position.