Hendersonida parvirostris, Rodríguez-Flores & Macpherson & Machordom, 2020

Rodriguez-Flores, Paula C., Macpherson, Enrique & Machordom, Annie, 2020, A new species of squat lobster of the genus Hendersonida (Crustacea, Decapoda, Munididae) from Papua New Guinea, ZooKeys 935, pp. 25-35 : 25

Hendersonida parvirostris sp. nov. Figures 2 , 3

Material.

Holotype: Biopapua stn CP3645, 24/8/2010, 06°46.394'S, 147°50.605'E, 403-418 m: ovigerous female, 8.9 mm (MNHN-IU-2011-4498). Paratype: Biopapua. Stn CP3633, 22/8/2010, 06°51.841'S, 147°04.672'E, 395-406 m: 1 ovigerous female, 12.2 mm (MNHN-IU-2011-3379).

Diagnosis.

Rostrum shorter than supraocular spines, each supraocular spine with small lateral spine. Carapace dorsal surface granulated with few scattered minute spines. Thoracic sternites with numerous arcuate striae, sternite 4 narrowly contiguous to sternite 3. Abdominal somites 2 and 3 spinose. Distomesial spine of antennal article 2 reaching end of article 3. Extensor distal margin of maxilliped 3 armed. Pereopods 2-4 long and slender, merus ca. 25 times as long as wide.

Description.

Carapace: Slightly broader than long; dorsal surface covered with numerous granules and few scattered minute spines, with few short simple setae; epigastric region with row of 6 minute spines; mesogastric region slightly convex, unarmed; cervical groove distinct; cardiac and anterior branchial regions slightly circumscribed; cardiac region with anterior transverse row of four minute spines, and two minute spines posterior to it; each branchial region with 2-4 small spines near lateral borders; frontal margin slightly concave; lateral margins convex; anterolateral spine reaching sinus between rostral and supraocular spines. Rostrum very short; supraocular spines longer than rostrum, each spine with additional small lateral spine; margin between rostral and supraocular spines concave.

Sternum: Thoracic sternites with numerous arcuate striae; sternite 3 width less than half width of sternite 4, anterior margin nearly straight; sternite 4 with anterior margin moderately elongate, narrowly contiguous to sternite 3; sternite 7 with numerous granules.

Abdomen: Somites 2 and 3 each with some small or moderate-sized spines on anterior and posterior ridges, two median spines larger than others; posterior ridge of somite 4 without distinct single median spine.

Eyes: Large, cornea dilated, much wider than eyestalk.

Antennule: Article 1 barely exceeding corneae, with distomesial spine slightly shorter than distolateral; ca. twice as long as wide; lateral margin without fringe of long setae, with distal slender portion ca. half as long as proximal inflated portion.

Antenna: Anterior prolongation of article 1 overreaching antennular article 1 by ca. one-fourth of its length; article 2 shorter than article 3 and slightly longer than wide, ventral surface with small scales; distomesial spine well developed, reaching end of article 3, and clearly not reaching midlength of anterior prolongation of article 1, distolateral angle unarmed; article 3 twice longer than wide, unarmed.

Maxilliped 3: Ischium 1.5 times length of merus measured along dorsal margin, distoventrally bearing one spine; merus with two or three small spines on flexor margin, extensor margin with distal spine.

Pereopod 1: Lost in holotype, only merus preserved in paratype. Merus 2.5 times carapace length, ca. 15 times longer than high, with row of spines along mesial margin.

Pereopods 2-4: Similar, long and slender, with minute granules and short scales on ventrolateral sides of meri, carpi and propodi; scales with short setae; extensor and flexor margins with numerous long plumose setae; pereopod 2 6.0 times carapace length, merus 3.0 times longer than carapace, ca. 25 times as long as wide, 1.8 times as long as propodus; propodus 20 times as long as wide, and 1.7 times dactylus length; merus with well-developed spines along extensor border, flexor margin with few spines; carpus with distal spine on extensor and flexor margin; propodus with some small movable spines along flexor margin; dactylus slightly curved, with longitudinal carinae along mesial and lateral sides, ventral border, under flexor margin, unarmed; pereopods 3 and 4 of similar length as pereopod 2, with similar spinulation and segment proportions as pereopod 2.

Colour in life: Base colour of carapace light orange, gastric region reddish; granules and spines orange. Rostrum and supraocular spines reddish. Abdominal somites 1-4 light orange, with scales and granules orange or reddish; somites 5 and 6 and telson whitish. Pereopods 2-4 light orange, spines along flexor margins reddish, spines along flexor margins whitish; distal portion of meri, carpi, and propodi and proximal part of carpi, propodi, and dactyli with reddish band, distal half of dactyli whitish.

Genetic data.

GenBank accession numbers: 16S MT252616-MT252617, and COI MT250542-MT250543 (Fig. 1 ).

Etymology.

From the Latin, parvus, little, and rostrum, in reference to the small size of the rostral spine.

Remarks.

The genus Hendersonida was erected for one rare species, H. granulata (Henderson, 1885) known from several localities of the western Pacific, clearly differentiable from all species of the genus Paramunida Baba, 1988 ( Macpherson 1993; Cabezas et al. 2010). The new species, H. parvirostris , is the second representative of the genus. Both species are morphologically and genetically separated from all the species of Paramunida (Fig. 1 ).

Two conspicuous diagnostic characteristics differentiate the Hendersonida genus from Paramunida : the granulated surface of the carapace; and the long distomesial spine of antennal article 2, almost reaching the end of the anterior prolongation of article 1 ( Cabezas and Macpherson 2014). The morphology of the new species, however, shows that the long distomesial spine of antennal article 2 is not a valid generic character because this spine is moderately short, only reaching the end of antennal article 3, in H. parvirostris . Additionally, in both species the anterior margin of sternite 4 is moderately elongate, narrowly contiguous with sternite 3, whereas this margin is nearly transverse, broadly contiguous with sternite 3, in Paramunida .

The two species of Hendersonida can be differentiated by the following characters:

The dorsal carapace surface has numerous well-developed spines in H. granulata, whereas these spines are minute and nearly absent in H. parvirostris.

The supraocular spines slightly exceed the rostral spine in the new species, whereas the rostral spine clearly overreaches the supraocular spines in H. granulata. Furthermore, each supraocular spine has one additional small lateral spine in the new species, which are absent in H. granulata.

The distomesial spine of the antennal article 2 reaches the end of the article 3 in the new species, whereas this spine almost reaches the end of the anterior prolongation of the article 1 in H. granulata.

The extensor margin of maxilliped 3 merus has a distal spine in the new species, whereas this spine is absent in H. granulata.

Pereopods 2-4 are much longer and slender in the new species: propodus 20 times as long as wide in H. parvirostris and 7-8 times as long as wide in H. granulata (Cabezas et al. 2010).

Distribution.

Papua New Guinea, between 395 and 418 m.

Figures

Figure 1. Phylogenetic hypothesis based on mitochondrial molecular data (COI and 16 S) represented by a tree obtained by Bayesian inference, including Bayesian posterior probabilities. To test the monophyly of Hendersonida, we have included all genetic data available from species of Paramunida included in Cabezas et al. (2012) and McCallum et al. (2016) (38 species). We have collapsed the Paramunida node to facilitate comparison between genera.

Figure 2. Hendersonida parvirostris sp. nov. ovigerous female holotype, 8.9 mm (MNHN-IU- 2011 - 4498), Papua New Guinea. A Carapace and abdomen, dorsal view B sternum C left antennule and antenna, ventral view D right maxilliped 3, lateral view E left pereopod 2, lateral view F left pereopod 3 merus, lateral view G left pereopod 4 merus, lateral view. Scale bars: 4 mm (A, B, E, F, G); 8 mm (C, D).

Figure 3. Hendersonida parvirostris sp. nov. dorsal view of ovigerous female holotype, 8.9 mm (MNHN-IU- 2011 - 4498), Papua New Guinea.