Family SPENGELIIDAE

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Family SPENGELIIDAE

Compiler and date details

C. Burdon-Jones, Queensland Museum, Brisbane, Queensland, Australia

Introduction

The Spengeliidae Willey, 1899 are the least homogeneous and least well known family in the Hemichordata. The family comprises four genera and 18 species: Glandiceps Spengel—six species, Schizocardium Spengel—two species, Spengelia Willey—six species, and Willeyia Punnett—three species (Marion 1885, 1886; Spengel 1893; Willey 1899; Punnett 1903; Van der Horst 1929, 1939, 1940; Burdon-Jones & Petersen 1964; Petersen 1965). Of these, only Glandiceps malayanus Spengel is found in Australian waters; it has also been recorded from Indonesian waters. It is readily distinguished by its intense colouration and marked dorso-ventral flattening of the trunk region. The proboscis is a rich yellow, the collar a bright red, and the trunk a deep yellowish red (Spengel 1907; Van der Horst 1939).

Schizocardium, Spengelia and Glandiceps species all have an ovoid to pyriform, often apically pointed, proboscis, depressed dorso-ventrally, with shallow to deep median dorsal and ventral grooves. In all three genera, the collar is as broad or broader than long, about a third to half the length of the proboscis, with a flared, smooth to wavy anterior margin. Willeyia species resemble saccoglossids, and have an elongate, cylindrical, apically blunt proboscis with median dorsal and ventral grooves extending almost to the apex. The proboscis is many times longer than the collar, which is twice as long as broad, with a slightly flared and smooth anterior margin

In all four genera, the protocoel has a very distinct lining and is partially or completely divided by a strongly developed dorso-ventral septum consisting of muscle and connective tissue fibres. The buccal diverticulum has an apical vermiform extension often as long as or longer than the axial complex, but may be small in some species. The circular muscle layer of the proboscis is very well developed and may be two to three times thicker than the epidermal nerve layer. The longitudinal muscle is evenly distributed and not arranged radially or concentrically as in the Ptychoderidae and the Harrimaniidae.

In most species, the proboscis skeleton is enveloped in chondroid tissue which forms a prominent collar or pad around the junction of the crura, and is often visible externally as a swelling at the base of the proboscis. The crura of the proboscis skeleton are elongate and may extend into the posterior third of the collar. The neurocord is devoid of any median dorsal linkages with the epidermal nerve plexus. In Spengelia, Glandiceps and Willeyia the branchiae embrace a half to two thirds of the pharynx, but in Schizocardium they embrace almost the entire pharynx except for narrow epi- and hypobranchial ridges.

The branchial skeletons of Spengelia and Schizocardium have synapticulae, and both have peribuccal cavities. Willeyia has peribuccal cavities, but no synapticulae, and Glandiceps lacks both peribuccal cavities and synapticulae.

Data on the presence of oesophageal pores are not available for all spengelids. Glandiceps has a single anterior series and paired posterior pores, Spengelia has paired posterior pores only and in Schizocardium the anterior pores are unequal on either side and followed by a single isolated pair. They have not been observed in Willeyia.

Hepatic caeca are absent in Spengelia, Willeyia and Glandiceps, but present as digitiform extensions of the dorsal and dorso-lateral surface of the postpharyngeal region in Schizocardium. Glandiceps is the only genus in the family in which a secondary intestine has been described in the posterior hepatic region.

Little is known about the breeding habits and life history of this family other than that the genus Glandiceps is supposed to have a tornaria larva. (Menon 1904; Stiasny-Wijnhoff & Stiasny 1926, 1927; Rao 1953; Björnberg 1959).