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Volume 85, 1957-58
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Family Naididae

Pristina nothofagi n.sp. Figs. 1–3.

This is a very small, transparent worm in which the coelomocytes, white in reflected light, are the most conspicuous feature to the naked eye. Individual worms are about 1 mm in length and two zooids may be up to 2 mm. The breadth of the prostomium is about 100 mu,

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Fig. 1.–Pristina nothofagi n. sp. semi-diagrammatic drawing. Fig. 2.–Pristina nothofagi n.sp. needle seta. Fig. 3.–Pristina nothofagi n.sp. ventral seta. Fig. 4.–Pristina minutum (Marcus) needle seta. Fig. 5.–Pristina minutum (Stephenson) needle seta. Fig. 6.–Pristina osborni (Walton) needle seta.

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but the body broadens to about 180 mu. There may be up to 22 segments in a worm and n is always 12. The prostomium is small, rounded, with no proboscis development. The first seven body segments are generally smaller than the succeeding segments.

The setae commence on the second segment. They consist dorsally of a single unserrated hair seta and a single needle seta per bundle and ventrally of 6–2 bifid crotchets per bundle. The hair setae are simple and flexible and vary in length from 110–200 mu, increasing in length up to segment VII. The needle setae (Fig. 2) are bayonet shaped with a distinct kink but no nodulus. The kink occurs about one-third the length from the distal end. The setae are 35–50 mu in length, bifid, with slightly separated teeth about 6 mu long. The teeth are nearly equal in size, the proximal tooth being slightly larger than the distal. The ventral setae (Fig. 3) are sigmoid, from 30–40 mu in length, with a distinct nodulus about one-third the length from the distal end. The teeth are subequal and about 1.5 mu long.

The alimentary canal consists of a pharynx in segments I-III with a dorsal diverticulum in II-III; a narrow oesophagus IV-VI; a stomach with characteristic Pristina canals in VII; a short looped narrow intestine in VIII broadening in IX into a wide intestine, some 100 mu in width, which narrows again posteriorly. Chloragogen starts in IV.

There is a simple dorsal and a simple ventral blood vessel. The main commissure is in II and other perivisceral commissures in III and IV. The dorsal vessel is not attached to the alimentary canal in VIII but passes directly from the stomach in VII to the large intestine in IX.

Nephridia are paired in IX. They may occur in subsequent segments either paired or single In the posterior zooid they are generally single. They are similar in form to those of P. taita Stout, 1956, with a small nephrostome and double lumina. The nephridiophore opens ventrally just anterior to the ventral setae.

Pharyngeal, oesophageal, and septal glands occur in II-VI. Coelomocytes, black in transmitted light, are numerous throughout the body length and are up to 20 mu in diameter.

Budding is the only form of reproduction observed. There may be several fission zones, the intermediate zooids consisting always of a single segment.

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Table I
P. osborni (Walton) P. nothofagi n.sp. P. minutum (Stephenson) P. minutum (Marcus)
Hair setae Length μ 145 110–200 80–90 80–90 up to 120
Needle setae Type Crotchet with nodulus (Fig. 6) Bayonet-shaped (Fig. 2) Crotchet with nodulus (Fig. 5) Bayonet-shaped (Fig. 4)
Length μ 50 35–50 35 30–35
Ventral setae Length μ 40 30–40 30–40 30–40
Nephridia ? Paired IX Single IX, XI Single IX, XI
Stomach VIII VII VIII VII? or VIII?
Length mm 1.6 1–2 2 1–2
n ? 12 12 12
s 15–16 22 17–19 ?

Three of the species of Pristina which have the same setal characteristics as this worm are distinguished by their very much larger size. These are P. menoni, P. jenkini, and P. breviseta, in which n is 19 or more. These worms have the stomach in VII. The remaining species, without a proboscis and with the same setal characters, is P. minutum (Stephenson). In this species Sperber (1948) includes worms described by Walton (1906) from North America, by Stephenson (1914) from India, and by

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Marcus (1943) from Brazil. All these worms resemble each other, and the present worm in their very small size. However, there is a marked distinction between the North American and Indian worms on one hand, and the Brazilian and the New Zealand worms on the other. The needle setae are clearly figured by Walton (Fig. 6) and by Stephenson (Fig. 5) as bifid, sigmoid crotchets with a distinct nodulus. Marcus, figures a bayonet shaped seta (Fig. 4) without a nodulus, closely resembling the setae of my worm. Marcus' worm is not therefore P. minutum. The principal distinction between Marcus' worm and the New Zealand worm lies in the position of the stomach. Although Marcus (1943: 130) is ambiguous on this point, indicating either VII or VIII, he figures it in VIII. He also states that the sinuous intestine occurs in IX and the swollen intestine in X. Another difference, although not so important, is that the nephridia are single in the Brazilian and paired in the New Zealand worm. The hair setae are very much longer in the New Zealand worm. The relations between the four worms are summarised in Table I. As can be seen from this table there is insufficient information about P. osborni to identify it with P. minutum (Stephenson). They may well prove distinct species. The New Zealand worm is separated from the Brazilian by the position of the stomach. Accepting this distinction it will be necessary to give a new name to P. minutum (Marcus).

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